化学气相沉积英文相关介绍
化学气相沉积的发展过程及展望
化学气相沉积的发展过程及展望化学气相沉积（Chemical Vapor Deposition，简称CVD）是一种将气态物质分解并沉积在基底表面上形成薄膜的技术。
随着材料科学的快速发展，化学气相沉积已经成为制备高质量薄膜的重要手段之一化学气相沉积技术的发展可以追溯到20世纪60年代。
最初，CVD主要用于金属薄膜的制备，例如金属电极的制备等。
然而，随着对新材料需求的不断增长，化学气相沉积技术逐渐扩展到了半导体、陶瓷、纳米材料等领域。
至今，CVD已经成为一种广泛应用于材料研究和工业生产领域的重要技术。
在CVD的发展过程中，有几个重要的里程碑。
首先是在20世纪70年代中期，化学气相沉积技术的研究出现了快速的发展，出现了像低压化学气相沉积（LPCVD）和高压化学气相沉积（HPCVD）等新技术。
这些新技术大大提高了薄膜的质量和沉积速率，为化学气相沉积技术的应用开辟了广阔的前景。
另一个里程碑是在20世纪80年代和90年代，随着纳米科技的兴起，CVD技术开始在纳米材料的制备中起到重要作用。
例如，通过化学气相沉积技术可以制备出纳米线、纳米颗粒和纳米膜等结构。
这些纳米材料具有独特的物理和化学性质，在光电子学、催化剂等领域具有广阔的应用前景。
目前，化学气相沉积技术仍在不断发展中，主要集中在以下几个方面：1.薄膜质量的提高：现阶段，CVD技术的主要挑战是如何提高薄膜的质量。
例如，通过优化沉积条件、控制物理参数等手段，可以改善薄膜的致密性、表面平整度和晶体质量等性能。
2.多功能材料的制备：CVD技术可以制备具有多种功能的材料，如氮化硅（SiN）薄膜用于光子器件的制备、氧化镓（Ga2O3）薄膜用于功率电子器件的制备等。
未来的发展方向是实现多功能材料的复合沉积，以实现更复杂的器件性能。
3.低温沉积的发展：目前，大多数CVD技术需要较高的沉积温度，这对一些温度敏感的材料限制较大。
因此，研究人员致力于开发低温CVD技术，以扩大化学气相沉积技术的应用范围。
化学气相沉积
历史的简短回顾
→古人类取暖或烧烤时熏在岩洞壁或岩石上的黑色碳层 →中国古代炼丹术中的“升炼”（最早的记载） →20世纪50年代，现代CVD技术用于刀具涂层（碳化钨 为基材经CVD氧化铝、碳化钛、氮化钛） →20世纪60、70年代，半导体和集成电路技术、超纯多 晶硅。 →1990年以来我国王季陶，提出激活低压CVD金刚石生 长热力学耦合模型。第一次真正从理论和实验对比上定 量化地证实反自发方向的反应可以通过热力学反应耦合 依靠另一个自发反应提供的能量推动来完成。
化学气相沉积的反应类型 简单热分解和热分解反应沉积
通常ⅢA,ⅣA，ⅤA族的一些低周期元素的氢化物如CH4、 SiH4、GeH4、B2H6、PH3、AsH3等都是气态化合物，而且加 热后易分解出相应的元素。因此很适合用于CVD技术中作 为原料气。其中CH4，SiH4分解后直接沉积出固态的薄 膜，GeH4也可以混合在SiH4中，热分解后直接得Si—Ge 合金膜。例如：
简单热分解和热分解反应沉积
通常金属化合物往往是一些无机盐类．挥发性很低，很 难作为CVD技术的原料气；而有机烷基金属则通常是气体 或易挥发的物质，因此制备金属或金属化合物薄膜时， 常常采用这些有机烷基金属为原料，应地形成了一类金 属有机化学气相沉积(Metal—Organic Chemical Vapor Deposition简称为MOCVD)技术。 其它一些含金属的有机化合物，例如三异丙醇铝 [Al(OC3H7)3] 以及一些β—丙酮酸(或β—二酮)的金属配 合初等不包含C—M键(碳一金属键)．并不真正属于金属 有机化合物，而是金属的有机配合物或含金属的有机化 合物。这些化合物也常常具有较大的挥发性，采用这些 原料的CVD技术，有时也被包含在MOCVD技术之中。
CVD的沉积反应室内部结构及工作原理变化最大，常常根 据不同的反应类型和不同的沉积物要求来专门设计。但 大体上还是可以把不同的沉积反应装置粗分为以下一些 类型。
化学气相沉积法发展历史
化学气相沉积法发展历史化学气相沉积法（Chemical Vapor Deposition，简称CVD）是一种重要的材料合成技术，通过在气相中使化学反应发生并生成所需材料，将其沉积在基底上。
这种方法具有高效、高纯度、可控性强等优势，被广泛应用于薄膜制备、纳米材料合成和微电子器件制造等领域。
CVD技术的历史可以追溯到19世纪末，当时一位叫做PaulSchützenberger的法国化学家首次观察到了金属在高温下由气相转变为固相的现象。
他发现，将一些金属试样加热，会在其表面上形成均匀的沉积物。
这个发现为后来的CVD技术奠定了基础。
20世纪初，人们开始系统地研究和应用CVD技术。
1913年，一位叫做Irving Langmuir的美国物理学家提出了气体从气相转变为固相的机理，并创建了一个名为“表面吸着”的概念。
他的研究揭示了CVD 现象背后的原理，为之后的研究提供了理论基础。
随着化学和物理的发展，CVD技术逐渐成为一种重要的合成方法。
1951年，美国科学家Allan C. Viegut首次提出了“化学气相沉积”这个术语，并详细描述了他在研究中所使用的技术。
在1950年代和1960年代，人们对CVD技术的理论和实验研究取得了显著进展，涂层技术开始应用于航空航天工业和其他领域。
到了1970年代，CVD技术取得了突破性的进展。
人们发展了各种CVD方法，包括低压CVD、热CVD、等离子体增强CVD等。
这些方法使得我们能够在更加复杂的材料系统中进行沉积，并实现了更高的沉积速率和纯度。
这一时期，CVD技术逐渐成为化学合成领域的重要研究方向。
随着科学技术的不断发展，CVD技术也在不断演化和完善。
近年来，人们将CVD技术与纳米材料合成、二维材料制备等领域结合起来，取得了许多重要进展。
例如，通过CVD方法，人们成功制备出了石墨烯、二硫化钼等具有重要应用价值的二维材料。
这些研究为材料科学和纳米技术的发展提供了重要的支持。
化学气相沉积
化学气相沉积作为一种非常有效的材料表 面改性方法,具有十分广阔的发展应用前景。 随着工业生产要求的不断提高, CVD 的工艺 及设备得到不断改进, 现已获得了更多新的 膜层, 并大大提高了膜层的性能和质量，它 对于提高材料的使用寿命、改善材料的性 能、节省材料的用量等方面起到了重要的 作用,下一步将向着沉积温度更低、有害生 成物更少、规模更大等方向发展。随着各 个应用领域要求的不断提高, 对化学气相沉 积的研究也将进一步深化,CVD 技术的发展 和应用也将跨上一个新的台阶。
2、CVD过程 反应气体向基体表面扩散
反应气体吸附于基体表面
在基体表面上产生的气相副产物脱离表面
留下的反应产物形成覆层
3、CVD几种典型化学反应
1）热分解
SiH4 >500℃ Si + 2H2 （在900-1000℃成膜） CH3SiCl3 1400℃ SiC + 3HCl
2）还原
WF6 +3H2 SiCl4 + 2Zn WF6 + 3 Si 2 W + 6HF (氢还原) Si + 2ZnCl2 （金属还原） SiF4 （基体材料还原） W+3 2
反应沉积成膜 反应沉积成膜
3、PCVD的特点
成膜温度低
沉积速率高 膜层结合力高
膜层质量好 能进行根据热力学规律难以发生的反应
4、PCVD与CVD装置结构相近， 只是需要增加能产生等离子体 的反应器。用于激发CVD反应 的等离子体有： 直流等离子体 射频等离子体 微波等离子体 脉冲等离子体
直流等离子体法(DCPCVD)
2、PCVD的成膜步骤 等离子体产生 等离子体产生
辉光放电的压力较低，加 速了等离子体的质量 输送和扩散
化学气相沉积CVD
这些具有高反应活性的物质很容易被吸附到较低温度的基
体表面上，于是，在较低的温度下发生非平衡的化学反应
沉积生成薄膜，这就大大降低了基体的温度，提高了沉积
速率。
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3. PECVD装置
普通CVD+高频电源（用于产生等离子体）
用高频产生辉光放电等离子体的卧式反应
主要由反应器（室）、供气系统和加热系统等组成
图8.3.1
Si片PN结构微细加工的CVD装置意示图
6
反应器的类型：
图8.3.2 CVD反应器的类型
7
沉积过程：
① 在主气流区域，反应物从反应器入口到分解区域的质
量输运；
② 气相反应产生膜形成的前驱体和副产物；
③ 成膜前驱体质量输运至生长表面；
④ 成膜前驱体吸附在生长表面；
可有效解决普通CVD基体温度高，沉积速率慢的不足。
1.等离子体
（1）物质的第四态
给物质以能量，即T↗：
固 液 气 电离，离子+自
由电子，等离子体，第四态。
（2）产生
自然界：大气电离层,高温太阳
实验室：气体放电，供给能量,维持；
图8.3.3 物质的四态
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（3）性质及应用
气体高度电离的状态；
下进行沉积的某些场合，如沉积平面
硅和MOS集成电路的纯化膜。
（2）按照沉积时系统压强的大小分类：
常压CVD（NPCVD），～1atm；
低压CVD（LPCVD），10～100Pa；
LPCVD具有沉积膜均匀性好、台阶覆盖及一致性较好、
针孔较小、膜结构完整性优良、反应气体的利用率高等优
点，不仅用于制备硅外延层，还广泛用于制备各种无定形
化学气相沉积(CVD)技术梳理
化学气相沉积（CVD）技术梳理1. 化学气相沉积CVD的来源及发展化学气相沉积（Chemical Vapor Deposition）中的Vapor Deposition意为气相沉积，其意是指利用气相中发生的物理、化学过程，在固体表面形成沉积物的技术。
按照机理其可以划分为三大类：物理气相沉积（Physical Vapor Deposition,简称PVD），化学气相沉积（Chemical Vapor Deposition,简称CVD）和等离子体气相沉积（Plasma Chemical Vapor Deposition,简称PCVD）。
[1]目前CVD的应用最为广泛，其技术发展及研究也最为成熟，其广泛应用于广泛用于提纯物质、制备各种单晶、多晶或玻璃态无机薄膜材料。
CVD和PVD之间的区别主要是，CVD沉积过程要发生化学反应，属于气相化学生长过程，其具体是指利用气态或者蒸汽态的物质在固体表面上发生化学反应继而生成固态沉积物的工艺过程。
简而言之，即通过将多种气体原料导入到反应室内,使其相互间发生化学反应生成新材料，最后沉积到基片体表面的过程。
CVD这一名称最早在Powell C F等人1966年所著名为《Vapor Deposition》的书中被首次提到，之后Chemical Vapor Deposition才为人广泛接受。
[2]CVD技术的利用最早可以被追溯到古人类时期，岩洞壁或岩石上留下了由于取暖和烧烤等形成的黑色碳层。
现代CVD技术萌芽于20世纪的50年代，当时其主要应用于制作刀具的涂层。
20世纪60～70年代以来，随着半导体和集成电路技术的发展，CVD技术得到了长足的发展和进步。
1968年Nishizawa课题组首次使用低压汞灯研究了光照射对固体表面上沉积P型单晶硅膜的影响，开启了光沉积的研究。
[3] 1972年Nelson和Richardson用CO2激光聚焦束沉积碳膜，开始了激光化学气相沉积的研究。
化学气相沉积英文(1)
OVERVIEWStudying chemical vapor deposition processes with theoretical chemistryHenrik Pedersen •Simon D.ElliottReceived:26February 2014/Accepted:28February 2014/Published online:18March 2014ÓSpringer-Verlag Berlin Heidelberg 2014Abstract In a chemical vapor deposition (CVD)process,a thin film of some material is deposited onto a surface via the chemical reactions of gaseous molecules that contain the atoms needed for the film material.These chemical reactions take place on the surface and in many cases also in the gas phase.To fully understand the chemistry in the process and thereby also have the best starting point for optimizing the process,theoretical chemical modeling is an invaluable tool for providing atomic-scale detail on surface and gas phase chemistry.This overview briefly introduces to the non-expert the main concepts,history and applica-tion of CVD,including the pulsed CVD variant known as atomic layer deposition,and put into perspective the use of theoretical chemistry in modeling these processes.Keywords Chemical vapor deposition ÁAtomic layer deposition ÁThin films ÁSurface chemistry ÁGas phase chemistry ÁTheoretical chemistry1An introduction to vapor-phase deposition techniques Thin films are layers of materials with thicknesses ranging from \1nm (a few atomic layers)to hundreds ofmicrometers (for reference,a human hair is about 75l m thick)[1].The importance of thin films in today’s society is enormous,and thin films can be found everywhere;from low friction coatings in a car engine to the anti-reflecting coating on the lenses of spectacles,as well as the decora-tive coating on their frames.Most metal objects around us have been machined by cutting tools that are coated with a hard,wear-resistant thin film.Replacement parts for the human body,such as hip joints,are often coated with a thin film to make them more biocompatible.Furthermore,today’s nanoelectronic devices are built up very precisely from stacks of thin films of various materials with different electrical properties,with some of the films as thin as one atomic layer.Technologically important thin films can be amorphous,polycrystalline or epitaxially grown single crystals,and the properties of the materials can often be tuned with great precision to suit various applications.To coat an object (the ‘‘substrate’’)with a thin film,it is often preferred to start from atoms or molecules in a vapor phase and place the object(s)to be coated in that vapor,letting atoms and/or molecules from the vapor build up a thin film on the surface of the object.These vapor-based thin film synthesis methods are classified as either physical vapor deposition (PVD)or chemical vapor deposition (CVD),depending on whether the film deposition process is driven by physical impacts or by chemical reactions,respectively.Generating the vapor in the reactor is of course straightforward when the desired element is avail-able in gaseous form,e.g.,O 2,but this is not the case for most elements.Therefore,in PVD,a solid sample con-taining the target elements is subjected to substantial energy,often in the form of a plasma or an electric dis-charge,thereby ejecting atoms and producing a vapor,which can then condense onto the substrate [2].In CVD,target elements are delivered in the form of volatilePublished as part of a special collection of articles focusing on chemical vapor deposition and atomic layer deposition.H.Pedersen (&)Department of Physics,Chemistry and Biology,Linko¨ping University,58183Linko ¨ping,Sweden e-mail:henke@ifm.liu.seS.D.ElliottTyndall National Institute,University College Cork,Lee Maltings,Cork,Ireland e-mail:Simon.Elliott@tyndall.ie Theor Chem Acc (2014)133:1476DOI 10.1007/s00214-014-1476-7molecules,denoted as precursors,and thefilm is built up via a series of chemical reactions between precursors, precursor fragments and the substrate.In the general case, such reactions can take place both in the gas phase and on the substrate surface.However,a form of CVD named atomic layer deposition(ALD)uses only surface chemical reactions to build up thinfilms with great precision[3,4].The precursor molecules are often diluted in a carrier gas that makes up the main part of the gas volume in the process, analogous to the solvent in liquid-phase chemical reactions. The carrier gas in CVD is most often hydrogen,nitrogen or argon,or mixtures of these.The majority of CVD processes are thermally activated by applying temperatures typically in the range200–2,000°C,although there are examples of CVD and ALD processes at lower temperatures,even down to room temperature,and at higher temperatures up to 2,500°C.There are also CVD and ALD processes that use a plasma to activate the chemistry by opening up new reaction pathways,by electron impact collisions[5]and by the gen-eration of ions and radicals,and these processes are referred to as plasma-enhanced CVD(PECVD)or alternatively plasma-assisted CVD(PACVD).The gas phase chemistry can also be activated by photons from a laser,referred to as laser-enhanced CVD(LECVD)or photo-assisted CVD[6].CVD may indeed be regarded as a chemical process that spans many traditional disciplines:chemical physics of gases and plasmas,surface science,solid-state chemistry of inorganic materials and organometallic or organic chem-istry for precursor synthesis.Thefield of CVD has been the subject of a number of books and book chapters[7–11], and several review articles on CVD[12–17]and ALD[3, 4,18–22]have been published over the last years,pro-viding both a detailed background to the processes and overviews of the current research frontier.The scope of this paper is limited to a brief overview of CVD,so as to put into perspective the use of theoretical studies,including those featured in this special collection of papers on the-oretical chemistry for CVD.2A brief history of CVDIn the history of CVD,J.M.Blocher is often mentioned as a father of modern CVD,since he suggested that thinfilm deposition processes based on chemical reactions should be distinguished from those based on physical processes.He proposed this at the symposium of the Electrochemical Society(ECS)1960in Houston and since then the terms CVD and PVD are used[23].Blocher also significantly developed the understanding of CVD,notably by summa-rizing the factors for structure/property/process relation-ships for CVDfilms[24].Refs.[23,25]and[26]provide a more complete account of the history of CVD.Thefirst CVD processes were reported and patented in the late nineteenth century and were used for the produc-tion of carbon powder for color pigment and of carbon fibers forfilaments in early versions of the electrical lamp. CVD of metals was also reported in the mid-and late nineteenth century;one of the earliest examples is the deposition of tungsten from WCl6in a hydrogen atmo-sphere reported by Wo¨hler in1855[27].Some years later, the famous Mond process for deposition of Ni was reported [28,29].This process was developed to purify nickel ore by transforming it to nickel tetracarbonyl[Ni(CO)4]at low temperatures and from this molecule deposit afilm of nickel on a substrate at a higher temperature.As early as1909,CVD of silicon was reported from SiCl4in hydrogen[30].This process is still used to produce pure silicon for industry,although somewhat refined to allow for greater control in the process.This is thefirst example of CVD being used to deposit afilm of a semi-conducting material and looking back in time it is clear that the microelectronics industry and CVD processes have developed hand-in-hand.The electronics boom,and asso-ciated drive toward miniaturization,has been pushing the development of CVD processes toward higher-qualityfilms over larger areas with better run-to-run reproducibility and uniformity.An important advance for the CVD of elec-tronic materials was the development in the late1960s of metal–organic CVD(MOCVD),where a metal is rendered volatile by surrounding it with organic ligands.Thefirst MOCVD process was used to deposit GaAs and was reported in1968[31].The use of metal–organic precursors such as trimethylgallium[Ga(CH3)3,also known as TMG] has thus been a key factor in the development of GaAs and other III–V-based electronics and forms today a corner-stone of III-nitride technology.The latest major breakthrough in thefield of CVD is the development of ALD,which wasfirst patented by Suntola in1977[32],although it should be pointed out that sig-nificant work was done prior to this in the former USSR (for more details on ALD history see ref[20]).Thefirst commercial application of ALD was in thinfilm electro-luminescent displays(TFELs),where ALD was shown to producefilms for the luminescent and protective layers with superior quality compared to the state-of-the-art thin film synthesis techniques of the1970s[33].Nevertheless, research into ALD remained at a low level until the late 1990s,when it was identified as a possible process solution for high-permittivity(‘‘high-k’’)thinfilms in the elec-tronics industry,specifically in memory devices and tran-sistors.Recently,Intel stated that the use of ALD was a key factor for the successful development of the high-k metal gate transistors that allowed further downscaling of the size of integrated circuit chips[34].Spurred on by this success, ALD is now becoming a widespread nanofabrication1476Page2of10Theor Chem Acc(2014)133:1476technique and being applied in a wide variety of industrial sectors.3Some applications of CVDThe applications of CVD are numerous,and their impact on today’s society is enormous.Here,a few important examples of CVD applications are described to provide a flavor of the impact of CVD on our everyday lives.3.1Hard coatingsMetal objects can be found everywhere,and most of them are machined by some cutting operation,e.g.,turning,milling or drilling.As an example,if one considers the amount of machined parts in an ordinary car and then considers how many cars are produced worldwide,it is obvious that metal cutting is of great importance for our society.Almost all cutting tools use exchangeable edges,referred to as inserts, made of cemented carbide.The great majority of inserts are coated with a hard,wear-resistant thinfilm that prolongs their lifetime by several orders of magnitude.Although PVD processes,especially for depositing hard nitride compounds, are emerging,CVD still is the work horse for coating cutting tools.A typical CVD coating for a cutting tool is a multilayer structure consisting mainly of some of the following mate-rials:TiN,TiC,TiC1-x N x,a-Al2O3and j-Al2O3.Thesefilm stacks are deposited in a single deposition process,typically at around50mbar and1,000°C,and a coating batch consists of several thousands of cutting inserts.Importantly,the properties of the individualfilms can be controlled with great precision[35].3.2Functional coatings on glassConsidering total area of depositedfilm,the largest appli-cation of CVD is to coat window glass.One of the most important reasons for coating a window is to prevent heat passing through,reducing the need for cooling down or warming up buildings,and thus reducing energy con-sumption.Typicallyfilms of transparent SnO2:F are used for this application.To alter the darkness of the window via electrochromism or thermochromism,films of WO3or VO2,respectively,are used.The coating can also reflect some of the incoming light,and for this,TiNfilms are employed.Thesefilms are deposited on the glass as afinal production step by an atmospheric pressure CVD technique mounted on thefloat glass production line.The technique was developed by Pilkington in the mid1980s.A recent development is to coat window glass with transparent TiO2,making the window self-cleaning by breaking down dirt via photocatalysis with sunlight[36].3.3MicroelectronicsIt is fair to say that without CVD we would not have the electronics that we take for granted today.All sorts of electronic devices are constructed from stacks of thin lay-ers with highly controlled electrical properties,and CVD is often the method of choice for depositing these thin layers. High process temperature is often not an issue for Si or III–V materials that form the bedrock of most of our everyday electronics devices,as well as for the emerging high-fre-quency and high-power electronics and light-emitting diodes based on silicon carbide(SiC)and III-nitrides. Therefore,CVD processes with process temperatures above1,000°C can be used;these processes are carried out close to thermodynamic equilibrium and do not suffer from particle bombardment.Thefilm quality is therefore gen-erally very high,with few defects in thefilms.The alter-native to CVD would be PVD,which is done further from thermodynamic equilibrium and often with a substantial amount of particle bombardment which gives rise to crystal defects.As mentioned above,ALD-grown high-k dielectric films have proven to be vital for a new generation of nanometer-scale transistors[34],where standard CVD is unable to deliver the required quality and uniformity at the thickness scale of just a few nanometers.Now that the utility of ALD in the semiconductor industry has been proven,it is being targeted for the deposition of a variety of materials in ultra-thin layers,particularly as interface control and three-dimensional structures become more important with continued down-scaling.3.4Gas permeation barriersAmong all deposition techniques,ALD is unique in enabling nanometer-thin,pinhole-freefilms that are con-formal over features at all length scales.By a happy coincidence,one of the most successful ALD processes across a wide temperature range is that of Al2O3,which is highly impermeable to oxygen gas and water vapor.It is therefore possible to use ALD to coat a variety of objects with an Al2O3coating that is impermeable to these gases, while also being so thin(on the order of10nm)that the optical and mechanical properties of the object are almost unaffected.Examples include reduced CO2permeability through ALD-coated PET bottles[37]and moisture/oxygen diffusion barriers for organic light emitting diodes in flexible display technology[38].4Chemical processes in CVDThinfilm growth by CVD is the result of a complex sequence of chemical reactions.All CVD processesTheor Chem Acc(2014)133:1476Page3of101476involve surface chemical processes and most CVD pro-cesses,with the exception of pure ALD processes,involve also gas phase chemical reactions.The types of chemical reactions that have been recognized as playing a role in CVD are schematically summarized in Fig.1.Such a conceptual scheme is generally the starting point for building theoretical models of the process.It is therefore important to test the relative importance of these chemical processes in the deposition of a given material system.An important feature of CVD is that a boundary layer develops above the substrate surface,also known as stag-nant boundary layer.The development of this layer is a consequence of thefluid dynamics whenflowing a gas mixture above the surface[11].In the boundary layer,the velocity of species in theflow direction is significantly lower than that in the main gas stream and the concentra-tion of species differs substantially compared to the main body of the gas stream.It is generally considered that all chemistry of importance to the CVD process takes place in the boundary layer and on the substrate surface.In most,but not all,CVD processes the precursors undergo gas phase chemical reactions that result in the formation of more reactive species.The reactions may be activated thermally or by an external source of energy,e.g., application of a plasma.Generally these more reactive species are smaller fragments of the original molecule and when a plasma is used to activate the chemistry the molecular fragments can even be radicals or ions.One should bear in mind here that many CVD processes are done at low pressures and high temperatures,allowing a significant lifetime of very reactive species,compared to many other chemical reaction environments in, e.g.,a liquid solution.It should be mentioned that for some CVD chemistries,the gas phase chemistry produces larger complexes of several precursor molecules that after some molecular re-arrangements are the species active infilm deposition[39].When hydrogen is used as carrier gas,it often takes part in the gas phase reactions,but even rela-tively inert nitrogen gas can in some thermally activated CVD processes function as both carrier gas andfilm pre-cursor.A mixture of hydrogen and nitrogen is then used as carrier gas,and only a very small fraction of the nitrogen molecules react to form thefilm.The use of plasma to activate the gas phase chemistry,as in PECVD,opens up several new reaction paths at signif-icantly lower temperatures,mainly by electron impact collisions but also by collisions between plasma ions and precursor molecules,and by ions or radicals reaching the surface[5].The effect of the plasma is therefore often controlled by the distance between plasma and substrate in the reactor;if the substrate is placed in the plasma or very close to the plasma(‘‘direct PECVD’’),ionic species will significantly contribute to the chemistry,both in the gas phase and on the surface.A longer distance between plasma and substrate(‘‘remote PECVD’’)leads to more significant contribution from radical species rather than ions.It should be noted also that the power supplied to the plasma discharge will change the amount of ions in the plasma and thereby also the ionic contribution to thefilm growth chemistry[40].In PECVD,dinitrogen gas is often used as nitrogen precursor since the molecule rather easily dissociates in the plasma.The precursor molecules or the more reactive fragments of the precursor molecules are transported via gas diffusion through the boundary layer to the substrate surface.The adsorption mode depends critically on the chemical prop-erties of the incident precursor or fragment and of the surface.All precursor molecules can be expected to weakly physisorb at least for a short time,followed by desorption, since CVD reagents are volatile by design.If there is suf-ficient chemical complementarity between precursor or reactive fragment and surface,stronger chemisorption is1476Page4of10Theor Chem Acc(2014)133:1476possible,leading to longer lifetimes of the adsorbate.Some adsorbates react rapidly on the surface(e.g.,dissociative chemisorption),either because bonds within the adsorbate are weakened or because of co-reagents on the surface. ALD is based on the elimination of ligands from the adsorbate through reaction with co-adsorbed remnants from a prior co-reagent pulse.Adsorbate molecules or fragments may be mobile on the surface and may sample a variety of surface sites via dif-fusion,which again may lead to reactions.In general, surface diffusion is the process that leads ultimately to formation of afilm of the target material.Finding the optimum adsorption site via diffusion is particularly important in the growth of epitaxial thinfilms for elec-tronics since the crystalline quality of thefilm determines the performance of thefinal device.Finding optimum sites is facilitated by a strong energetic driving force toward forming the target material from the reagents.In ALD,this has been described as‘‘densification,’’whereby the coor-dination number of the constituent atoms increases from the low value of molecular precursors to the high value of the solid product[42,43].An important aspect of thinfilm deposition is the growth mode of thefilm on a given substrate.Fragments may aggregate into nuclei or islands,or may attach to an atomic step,or may favor a uniform coating.Roughness will increase if subsequent growth is favored at islands.By contrast,well-behaved ALD processes give conformal films that exactly follow the roughness of the substrate. Ultimately the growth processes combine and dictate the larger-scale morphology of the as-grownfilm(epitaxial crystal,polycrystalline or amorphous),but the factors determining this are not in general well understood[4].The parts of the precursor molecule(e.g.,the ligands)that do not constitute the target material should then desorb from thefilm surface as by-products.These by-products can be simple molecules formed by the chemical reactions on the surface,e.g.,H2,CO2or Cl2,or can be large molecules derived from the ligands.For example,a protonated ligand is the by-product in thermal ALD of metal oxides using H2O as co-reagent.In any case,it is of great importance to all CVD processes that these by-products desorb cleanly from thefilm surface and are not incorporated as impurities in thefilm. 5The use of theoretical studies developmentand understanding of CVD processesThe main motivation for theoretical chemical studies of CVD processes is obtaining a detailed understanding of the chemical reactions summarized in Fig.1.There are various outcomes from obtaining this understanding,as shown in the following examples.5.1A better understanding of established CVDprocessesThermochemical modeling of the gas phase chemistry in CVD is a convenient approach for understanding the gas chemistry,given that not many experimental techniques are available.Spectroscopic technique,e.g.,Raman or FT-IR spectroscopy,could in principle be used but this requires that all molecules in the gas phase can be detected by these techniques and that the CVD reactor can befitted with viewports of a material that is both transparent for the excitation light and at the same time not affected by the CVD gases and process temperatures.A mass spectrometer measuring the gasflow could also be used to study the process chemistry;the problem with this is that only the stable molecules are detected while all unstable interme-diates are lost.An example of a CVD process where much understanding has been provided by thermochemical modeling is CVD of electronic grade SiC.Significant effort has been directed toward understanding the process,and a gas phase and surface reaction model has been proposed [44].Using this model,the CVD process can be discussed based on the gas phase and surface chemistry,rather than susceptor design and gasflow patterns.Modeling can then be used to predict growth rate,etching rate,surface mor-phology and doping,all key aspects when doing CVD of electronic device structures.Detailed gas phase chemistry models can also be obtained by quantum chemical calcu-lations,an example is the gas chemistry model for CVD of boron carbide from BCl3and C3H8involving16interme-diates presented in ref[45].Consider the CVD of Al2O3from AlCl3and CO2,which has mainly been developed by research departments in the hard coatings industry.CO2forms H2O and CO together with the hydrogen carrier gas in a gas phase reaction in the reactor,and H2O then acts as the oxygen precursor in the formation of Al2O3.The catalytic effect of H2S in this process has been known for many years.The addition of H2S leads to a higher deposition rate and more surface-controlled deposition process as evidenced by more uni-form coating thickness on complex substrate geometries [46].But since this process was mainly developed in industry,where detailed understanding often has low pri-ority,it was only lately that a surface chemical model supported by careful theoretical chemistry modeling could be presented[47].It was suggested that H2S acts as a true surface catalyst by facilitatingfirst the removal of adsorbed chlorine from the surface and then the adsorption of H2O. Another example where modeling has been able to explain details in CVD of hard coatings is the observation that thin films of titanium carbide grow along the(111)direction when aromatic hydrocarbons such as benzene are used, while aliphatic hydrocarbons, e.g.,methane,produceTheor Chem Acc(2014)133:1476Page5of101476growth in the(100)direction.This is of interest since(111) TiC performs better in cutting operations[48]and since control of the preferred TiC growth direction enables control of the preferred growth direction of alumina deposited on top of the TiC layer[49].The explanation for the change in preferred growth direction with aromatic hydrocarbons,provided by quantum chemical calculations, was that benzene chemisorbs significantly more strongly on the(111)surface compared to the(100)surface and reduces the surface energy of the(111)surface[50]. Methane did not show any significant preference for either surface,so the lower surface energy of the(100)surface controls the growth direction when aliphatic hydrocarbons are used.Although thesefindings on the surface chemistry are not likely to change the well-established and optimized CVD process for industrially used hard coatings,such deeper understanding of the chemistry can serve as a guide for design of future CVD processes.5.2Using modeling for designing new CVD processes Theoretical studies of CVD surface chemistry that is more directed toward designing a new CVD process for a material are the theoretical studies of CVD of cubic boron nitride(c-BN)onto diamond surfaces.Models are devel-oped of both the initial growth stage onto a diamond sur-face[51]and the subsequent growth of c-BN onto c-BN [52,53],including surface reconstructions induced by adsorption of precursor molecules onto c-BN[54,55].The authors of these studies boil down their results to a sug-gested ALD chemistry for deposition of c-BN[52], although it remains to be seen whether it will be tested given the large amount of HF produced as by-product.When developing precursors for new CVD processes, modeling can give a better understanding of the behavior of the molecules.It is especially important to understand how the molecules behave upon vaporization and in the vapor phase.One such example is the development of CVD precursors for metal boridefilms of the actinides and lan-thanides[56,57],where DFT modeling provided a better understanding of why the same type of organometallic molecule works as CVD precursor for Sm,Pr and Er but decomposes instead of subliming for U[58].Approaches exist for the simulation of gas–liquid equi-libria for small molecules[59],which allow the vapor pressure to be predicted.Extending these to metalorganic molecules requires accurate estimation of both metal–ligand bonding and intermolecular interaction,and there-fore requires an approach beyond standard density func-tional theory.Simulating hundreds of molecules at such a high level is currently beyond routine computational capacity.5.3ALD development and understandingGiven its great importance for the electronics industry,ALD is today thefield of CVD where perhaps the largest amount of effort is being directed toward increased understanding of the process chemistry.Research on ALD is somewhat simplified by the surface-controlled nature of the process—at least in the ideal case—so that growth should be independent of other factors such as gas phase chemistry and gasflow in the reactor. However,the stringent and partially contradictory requirements for achieving ALD make it very difficult to design a new pro-cess,even when theory and experiment work closely together.Since the earliest days of ALD research,atomic-scale models have been made of the underlying chemistry.Pio-neering calculations were carried out on the zinc sulfide system by Pakkanen and Lindblad in the1980s[60,61].Over150 publications modeling ALD have followed since then,mostly carrying out quantum chemistry on the reactions of precursors with model substrates and many of these concerned with high-permittivity dielectrics on silicon.The state of the art to2012is summarized in ref[62].Since then,our most recent atomic-scale simulations have revealed new details of the mechanism of oxide ALD[43],have accounted for the stoichiometry of ternary oxides[63],have assessed precursor ligands for alka-line earth metal oxides[64]and for copper metal[65]and have developed kinetic Monte Carlo models offilm growth[66].The ALD process is manifest across many length scales.The pulsedflow of gases into meter-scale reactors,around milli-meter-scaled geometries,leads to chemical reactions between atoms,which grow into nanometer-thickfilms and coat micron-scaled pores or particles.It is clearly impossible to describe explicitly all of these length scales in one model,and most simulations are‘‘multi-scale’’insofar as they involve coupling between selected length scales according to the property of interest.The problem of timescale in ALD is perhaps even more acute than that of length scale,since a combination of fast(ps–ns)and slow reactions(l s–ms)contribute tofilm growth,and gases are pulsed and purged over second-long timescales.Well-behaved ALD processes are independent of reactor conditions, and so modeling ALD chemistry exclusively at the atomic scale can in fact explain many features offilm growth,without ref-erence to reactor conditions.Nevertheless,explaining ALD’s unique selling point—conformal and uniform growth regard-less of the size and shape of the substrate—requires modeling at higher length scales,ideally incorporating information about the reaction chemistry from the atomic scale.6An overview of the special collection of paperson CVD and ALD modelingThis overview strives to aid readers with little or no experience in CVD and ALD and to put this special1476Page6of10Theor Chem Acc(2014)133:1476。
等离子化学气相沉积
等离子体化学气相沉积(plasmachemical vapor deposition)是指用等离子体激活反应气体，促进在基体表面或近表面空间进行化学反应，生成固态膜的技术。
按产生等离子体的方法，分为射频等离子体、直流等离子体和微波等离子体CVD等。
等离子体化学气相沉积（plasma chemical vapor deposition）简称PCVD，是一种用等离子体激活反应气体,促进在基体表面或近表面空间进行化学反应,生成固态膜的技术。
等离子体化学气相沉积技术的基本原理是在高频或直流电场作用下，源气体电离形成等离子体，利用低温等离子体作为能量源，通入适量的反应气体，利用等离子体放电，使反应气体激活并实现化学气相沉积的技术。
PCVD与传统CVD技术的区别在于等离子体含有大量的高能量电子，这些电子可以提供化学气相沉积过程中所需要的激活能，从而改变了反应体系的能量供给方式。
由于等离子体中的电子温度高达10000K，电子与气相分子的碰撞可以促进反应气体分子的化学键断裂和重新组合，生成活性更高的化学基团，同时整个反应体系却保持较低的温度。
这一特点使得原来需要在高温下进行的CVD过程得以在低温下进行。
化学气相沉积 书籍 -回复
化学气相沉积书籍-回复您好！下面是一篇关于化学气相沉积（Chemical Vapor Deposition，简称CVD）的1500-2000字的文章。
化学气相沉积（Chemical Vapor Deposition，简称CVD）是一种制备高品质、薄膜状材料的重要技术。
它可用于制备各种薄膜材料，如金属、半导体、无机化合物和高分子材料。
CVD技术在微电子、光电子、表面工程、传感器、涂层和纳米科技等领域有着广泛的应用。
CVD的原理是通过在反应室中使反应气体与衬底表面发生化学反应，形成所需的薄膜材料。
整个过程实际上是在高温和低压下进行的。
当反应气体进入高温的反应室时，气体分子会分解并与衬底表面上的反应物发生反应，从而形成薄膜。
其中的反应过程包括气体分解、物理吸附、化学反应和复合反应等多个阶段。
CVD的关键因素之一是反应气体的选择，这取决于所需的薄膜材料。
例如，金属薄膜的制备通常使用有机金属化合物作为反应气体。
而SiO2薄膜的制备则需要将硅源气体和氧源气体一起引入反应室中进行反应。
此外，衬底的选择、反应温度和压力等也对CVD过程和薄膜质量有重要影响。
CVD技术有几种主要的类型，如低压CVD、热CVD、等离子体增强CVD 和液相CVD等。
每种类型都有其独特的优点和适用范围。
例如，低压CVD通常用于制备高质量薄膜和多层薄膜结构。
热CVD可以在较高的温度下形成薄膜，使得反应速率更高。
等离子体增强CVD则可通过激发和离子化反应气体来提高反应速率和薄膜质量。
液相CVD是一种将CVD技术应用于液体阶段的方法，适用于一些高分子材料的制备。
然而，不同的CVD技术也存在一些共同的问题，如气相混合、副反应、杂质控制和薄膜均匀性等。
这些问题需要通过调整反应条件、改进反应体系和优化反应装置来解决。
此外，监测和控制薄膜的厚度、成分和质量也是CVD过程中关键的挑战之一。
近年来，随着纳米科技的快速发展，CVD技术也得到了快速的发展和应用。
CVD
化学气相沉积中文名称：化学气相沉积英文名称：chemical vapor deposition其他名称：CVD法(CVD)定义：用化学方法使气体在基体材料表面发生化学反应并形成覆盖层的方法。
应用学科：机械工程（一级学科）；表面工程（二级学科）；气相沉积（三级学科）定义化学气相沉积(Chemical vapor deposition，简称CVD)是反应物质在气态条件下发生化学反应，生成固态物质沉积在加热的固态基体表面，进而制得固体材料的工艺技术。
它本质上属于原子范畴的气态传质过程。
与之相对的是物理气相沉积（PVD）。
应用现代科学和技术需要使用大量功能各异的无机新材料，这些功能材料必须是高纯的，或者是在高纯材料中有意地掺人某种杂质形成的掺杂材料。
但是，我们过去所熟悉的许多制备方法如高温熔炼、水溶液中沉淀和结晶等往往难以满足这些要求，也难以保证得到高纯度的产品。
因此，无机新材料的合成就成为现代材料科学中的主要课题。
化学气相淀积是近几十年发展起来的制备无机材料的新技术。
化学气相淀积法已经广泛用于提纯物质、研制新晶体、淀积各种单晶、多晶或玻璃态天机薄膜材料。
这些材料可以是氧化物、硫化物、氮化物、碳化物，也可以是III-V、II-IV、IV-VI族中的二元或多元的元素间化合物，而且它们的物理功能可以通过气相掺杂的淀积过程精确控制。
目前，化学气相淀积已成为无机合成化学的一个新领域。
特点1)在中温或高温下，通过气态的初始化合物之间的气相化学反应而形成固体物质沉积在基体上。
2)可以在常压或者真空条件下(负压“进行沉积、通常真空沉积膜层质量较好)。
3)采用等离子和激光辅助技术可以显著地促进化学反应，使沉积可在较低的温度下进行。
4)涂层的化学成分可以随气相组成的改变而变化，从而获得梯度沉积物或者得到混合镀层。
5)可以控制涂层的密度和涂层纯度。
6)绕镀件好。
可在复杂形状的基体上以及颗粒材料上镀膜。
适合涂覆各种复杂形状的工件。
化学气相沉积CVD
化学气相沉积1 前言化学气相沉积CVD(Chemical Vapor Deposition)是利用加热，等离子体激励或光辐射等方法，使气态或蒸汽状态的化学物质发生反应并以原子态沉积在置于适当位置的衬底上，从而形成所需要的固态薄膜或涂层的过程。
一般地说，化学气相沉积可以采用加热的方法获取活化能，这需要在较高的温度下进行；也可以采用等离子体激发或激光辐射等方法获取活化能，使沉积在较低的温度下进行。
另外，在工艺性质上，由于化学气相沉积是原子尺度内的粒子堆积，因而可以在很宽的范围内控制所制备薄膜的化学计量比；同时通过控制涂层化学成分的变化，可以制备梯度功能材料或得到多层涂层。
在工艺过程中，化学气相沉积常常在开放的非平衡状态下进行，根据耗散结构理论，利用化学气相沉积可以获得多种晶体结构。
在工艺材料上，化学气相沉积涵盖无机、有机金属及有机化合物，几乎可以制备所有的金属（包括碳和硅），非金属及其化合物（碳化物、氮化物、氧化物、金属间化合物等等）沉积层。
另外，由于气态原子或分子具有较大的转动动能，可以在深孔、阶梯、洼面或其他形状复杂的衬底及颗粒材料上进行沉积。
为使沉积层达到所需要的性能，对气相反应必须精确控制。
正是由于化学气相沉积在活化方式、涂层材料、涂层结构方面的多样性以及涂层纯度高工艺简单容易进行等一系列的特点，化学气相沉积成为一种非常灵活、应用极为广泛的工艺方法，可以用来制备各种涂层、粉末、纤维和成型元器件。
特别在半导体材料的生产方面，化学气相沉积的外延生长显示出与其他外延方法（如分子束外延、液相外延）无与伦比的优越性，即使在化学性质完全不同的衬底上，利用化学气相沉积也能产生出晶格常数与衬底匹配良好的外延薄膜。
此外，利用化学气相沉积还可生产耐磨、耐蚀、抗氧化、抗冲蚀等功能涂层。
在超大规模集成电路中很多薄膜都是采用CVD方法制备。
经过CVD 处理后，表面处理膜密着性约提高30%，防止高强力钢的弯曲，拉伸等成形时产生的刮痕。
化学气相沉积
三、化学输运反应
140 ~ 240C
一、热解反应
单氨络合物已用于热解制备氮化物。
GaCl 3 NH3 GaN＋3HCl
800~900C
AlCl3 NH3 AlN＋3HCl
800~900C
B3 N3 H6 3BN 3H2
9001100
二、化学合成反应
两种或多种气态反应物在一热衬底上相互反应，这类反应称为化 学合成反应。
化学气相沉积合成实例 1.制备纳米级氧化物、碳化物、氮化物超细粉
A(g) + B(g) → C(s) + D(g)↑
典型的气相合成反应有： 3SiH4(g)+4NH3(g) → Si3N4(s)+12H2(g)↑ 3SiCl4(g)+4NH3(g) → Si3N4(s)+12HCl(g)↑ 2SiH4(g)+C2H4(g) → 2SiC(s)+6H2(g)↑ BCl(g)+3/2H2(g) → B(s)+3HCl(g)↑
~1200C SiCl 4 2H 2 1150 Si ＋4HCl
475 SiH4 2O2 325 SiO2 2H 2O 1250C TiCl4 N2 H 2 1200 2TiN 8HCl
C Al2 (CH3 )6 12O2 450 Al2O3 9H2O
化学气相沉积CVD
化学气相沉积1 前言化学气相沉积CVD(Chemical Vapor Deposition)是利用加热，等离子体激励或光辐射等方法，使气态或蒸汽状态的化学物质发生反应并以原子态沉积在置于适当位置的衬底上，从而形成所需要的固态薄膜或涂层的过程。
一般地说，化学气相沉积可以采用加热的方法获取活化能，这需要在较高的温度下进行；也可以采用等离子体激发或激光辐射等方法获取活化能，使沉积在较低的温度下进行。
另外，在工艺性质上，由于化学气相沉积是原子尺度内的粒子堆积，因而可以在很宽的范围内控制所制备薄膜的化学计量比；同时通过控制涂层化学成分的变化，可以制备梯度功能材料或得到多层涂层。
在工艺过程中，化学气相沉积常常在开放的非平衡状态下进行，根据耗散结构理论，利用化学气相沉积可以获得多种晶体结构。
在工艺材料上，化学气相沉积涵盖无机、有机金属及有机化合物，几乎可以制备所有的金属（包括碳和硅），非金属及其化合物（碳化物、氮化物、氧化物、金属间化合物等等）沉积层。
另外，由于气态原子或分子具有较大的转动动能，可以在深孔、阶梯、洼面或其他形状复杂的衬底及颗粒材料上进行沉积。
为使沉积层达到所需要的性能，对气相反应必须精确控制。
正是由于化学气相沉积在活化方式、涂层材料、涂层结构方面的多样性以及涂层纯度高工艺简单容易进行等一系列的特点，化学气相沉积成为一种非常灵活、应用极为广泛的工艺方法，可以用来制备各种涂层、粉末、纤维和成型元器件。
特别在半导体材料的生产方面，化学气相沉积的外延生长显示出与其他外延方法（如分子束外延、液相外延）无与伦比的优越性，即使在化学性质完全不同的衬底上，利用化学气相沉积也能产生出晶格常数与衬底匹配良好的外延薄膜。
此外，利用化学气相沉积还可生产耐磨、耐蚀、抗氧化、抗冲蚀等功能涂层。
在超大规模集成电路中很多薄膜都是采用CVD方法制备。
经过CVD 处理后，表面处理膜密着性约提高30%，防止高强力钢的弯曲，拉伸等成形时产生的刮痕。
化学气相沉积英文相关介绍
A number of forms of CVD are in wide use and are frequently referenced in the literature. These processes differ in the means by which chemical reactions are initiated (e.g., activation process) and process conditions.∙Classified by operating pressure:o Atmospheric pressure CVD (APCVD) – CVD processes at atmospheric pressure.o Low-pressure CVD(LPCVD) –CVD processes at subatmospheric pressures.[1] Reduced pressures tend to reduce unwantedgas-phase reactions and improve film uniformity across thewafer. Most modern CVD processes are either LPCVD or UHVCVD.o Ultrahigh vacuum CVD(UHVCVD) –CVD processes at a very low pressure, typically below 10−6Pa (~10−8torr). Note that inother fields, a lower division between high and ultra-highvacuum is common, often 10−7 Pa.∙Classified by physical characteristics of vapor:o Aerosol assisted CVD (AACVD) – A CVD process in which the precursors are transported to the substrate by means of aliquid/gas aerosol, which can be generated ultrasonically.This technique is suitable for use with non-volatileprecursors.o Direct liquid injection CVD(DLICVD) –A CVD process in which the precursors are in liquid form (liquid or solid dissolvedin a convenient solvent). Liquid solutions are injected ina vaporization chamber towards injectors (typically carinjectors). Then the precursor vapors are transported to thesubstrate as in classical CVD process. This technique issuitable for use on liquid or solid precursors. High growthrates can be reached using this technique.∙Plasma methods (see also Plasma processing):o Microwave plasma-assisted CVD (MPCVD)o Plasma-Enhanced CVD (PECVD) – CVD processes that utilize plasma to enhance chemical reaction rates of the precursors.[2]PECVD processing allows deposition at lower temperatures,which is often critical in the manufacture of semiconductors.o Remote plasma-enhanced CVD (RPECVD) – Similar to PECVD except that the wafer substrate is not directly in the plasmadischarge region. Removing the wafer from the plasma regionallows processing temperatures down to room temperature.∙Atomic layer CVD(ALCVD) –Deposits successive layers of different substances to produce layered, crystalline films. See Atomic layer epitaxy.∙Combustion Chemical Vapor Deposition (CCVD) – nGimat's proprietary Combustion Chemical Vapor Deposition process is anopen-atmosphere, flame-based technique for depositinghigh-quality thin films and nanomaterials.∙Hot wire CVD (HWCVD) – also known as catalytic CVD (Cat-CVD) or hot filament CVD (HFCVD). Uses a hot filament to chemicallydecompose the source gases.[3]∙Metalorganic chemical vapor deposition (MOCVD) – CVD processes based on metalorganic precursors.∙Hybrid Physical-Chemical Vapor Deposition (HPCVD) – Vapor deposition processes that involve both chemical decomposition of precursor gas and vaporization of a solid source.∙Rapid thermal CVD (RTCVD) – CVD processes that use heating lamps or other methods to rapidly heat the wafer substrate. Heating only the substrate rather than the gas or chamber walls helps reduce unwanted gas phase reactions that can lead to particle formation.∙Vapor phase epitaxy (VPE)UsesIntegrated circuitsVarious CVD processes are used for integrated circuits(ICs). Particular materials are deposited best under particular conditions.PolysiliconPolycrystalline silicon is deposited from silane (SiH4), using the following reaction:SiH4→ Si + 2 H2This reaction is usually performed in LPCVD systems, with either pure silane feedstock, or a solution of silane with 70–80% nitrogen. Temperatures between 600 and 650 °C and p ressures between 25 and 150 Pa yield a growth rate between 10 and 20 nm per minute. An alternative process uses a hydrogen-based solution. The hydrogen reduces the growth rate, but the temperature is raised to 850 or even 1050 °C to compensate.Polysilicon may be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber. Diborane increases the growth rate, but arsine and phosphine decrease it.Silicon dioxideSilicon dioxide (usually called simply "oxide" in the semiconductor industry) may be deposited by several different processes. Common sourcegases include silane and oxygen, dichlorosilane (SiCl2H2) and nitrousoxide(N2O), or tetraethylorthosilicate(TEOS; Si(OC2H5)4). The reactionsare as follows[citation needed]:SiH4 + O2→ SiO2+ 2 H2SiCl2H2+ 2 N2O → SiO2+ 2 N2+ 2 HClSi(OC2H5)4→ SiO2+ byproductsThe choice of source gas depends on the thermal stability of the substrate; for instance, aluminium is sensitive to high temperature. Silane deposits between 300 and 500 °C, dichlorosilane at around 900 °C, and TEOS between 650 and 750 °C, resulting in a layer of low- temperature oxide (LTO). However, silane produces a lower-quality oxide than the other methods (lower dielectric strength, for instance), and it deposits non conformally. Any of these reactions may be used in LPCVD, but the silane reaction is also done in APCVD. CVD oxide invariably has lower quality than thermal oxide, but thermal oxidation can only be used in the earliest stages of IC manufacturing.Oxide may also be grown with impurities (alloying or "doping"). This may have two purposes. During further process steps that occur at high temperature, the impurities may diffuse from the oxide into adjacent layers (most notably silicon) and dope them. Oxides containing 5–15% impurities by mass are often used for this purpose. In addition, silicon dioxide alloyed with phosphorus pentoxide ("P-glass") can be used to smooth out uneven surfaces. P-glass softens and reflows at temperatures above 1000 °C. This process requires a phosphorus concentra tion of at least 6%, but concentrations above 8% can corrode aluminium. Phosphorus is deposited from phosphine gas and oxygen:4 PH3 + 5 O2→ 2 P2O5+ 6 H2Glasses containing both boron and phosphorus (borophosphosilicate glass, BPSG) undergo viscous flow at lower temperatures; around 850 °C is achievable with glasses containing around 5 weight % of both constituents, but stability in air can be difficult to achieve. Phosphorus oxide in high concentrations interacts with ambient moisture to produce phosphoric acid. Crystals of BPO4can also precipitate from the flowing glass on cooling; these crystals are not readily etched in the standard reactive plasmas used to pattern oxides, and will result in circuit defects in integrated circuit manufacturing.Besides these intentional impurities, CVD oxide may contain byproducts of the deposition process. TEOS produces a relatively pure oxide, whereas silane introduces hydrogen impurities, and dichlorosilane introduces chlorine.Lower temperature deposition of silicon dioxide and doped glasses from TEOS using ozone rather than oxygen has also been explored (350 to 500 °C). Ozone glasses have excellent conformality but tend to be hygroscopic –that is, they absorb water from the air due to the incorporation of silanol (Si-OH) in the glass. Infrared spectroscopy and mechanical strain as a function of temperature are valuable diagnostic tools for diagnosing such problems.Silicon nitrideSilicon nitride is often used as an insulator and chemical barrier in manufacturing ICs. The following two reactions deposit nitride from the gas phase:3 SiH4 + 4 NH3→ Si3N4+ 12 H23 SiCl2H2+ 4 NH3→ Si3N4+ 6 HCl + 6 H2Silicon nitride deposited by LPCVD contains up to 8% hydrogen. It also experiences strong tensile stress, which may crack films thicker than 200 nm. However, it has higher resistivity and dielectric strength than most insulators commonly available in microfabrication (1016Ω·cm and 10 M V/cm, respectively).Another two reactions may be used in plasma to deposit SiNH:2 SiH4 + N2→ 2 SiNH + 3 H2SiH4 + NH3→ SiNH + 3 H2These films have much less tensile stress, but worse electrical properties (resistivity 106 to 1015Ω·cm, and dielectric strength 1 to 5 MV/cm).[4]MetalsSome metals (notably aluminium and copper) are seldom or never deposited by CVD. As of 2010, a commercially cost effective, viable CVD process for copper did not exist, though copper formate, copper(hfac)2, Cu(II) ethyl acetoacetate, and other precursors have been used. Copper deposition of the metal has been done mostly by electroplating, in order to reduce the cost. Aluminum can be deposited from tri-isobutyl aluminium (TIBAL), triethyl/methyl aluminum (TEA,TMA), or dimethylaluminum hydride (DMAH), but physical vapor deposition methods are usually preferred.[citation needed]However, CVD processes for molybdenum, tantalum, titanium, nickel, and tungsten are widely used[citation needed]. These metals can form useful silicides when deposited onto silicon. Mo, Ta and Ti are deposited by LPCVD, from their pentachlorides. Nickel, molybdenum, and tungsten can be deposited at low temperatures from their carbonyl precursors. In general, for an arbitrary metal M, the reaction is as follows:2 MCl5 + 5 H2→ 2 M + 10 HClThe usual source for tungsten is tungsten hexafluoride, which may be deposited in two ways:WF6→ W + 3 F2WF6 + 3 H2→ W + 6 HFDiamondColorless gem cut from diamond grown by chemical vapor depositionCVD can be used to produce synthetic diamond by creating the circumstances necessary for carbon atoms in a gas to settle on a substrate in crystalline form.CVD of diamond has received a great deal of attention in the materials sciences because it allows many new applications of diamond that had previously been considered too difficult to make economical. CVD diamond growth typically occurs under low pressure(1–27 kPa; 0.145–3.926 psi;7.5-203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically includehydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others. The energy source is intended to generate a plasma in which the gases are broken down and more complex chemistries occur. The actual chemical process for diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.The advantages to CVD diamond growth include the ability to grow diamond over large areas, the ability to grow diamond on a substrate, and the control over the properties of the diamond produced. In the past, when high pressure high temperature (HPHT) techniques were used to produce diamond, the diamonds were typically very small free standing diamonds of varying sizes. With CVD diamond growth areas of greater than fifteen centimeters (six inches) diameter have been achieved and much larger areas are likely to be successfully coated with diamond in the future. Improving this ability is key to enabling several important applications.The ability to grow diamond directly on a substrate is important because it allows the addition of many of diamond's important qualities to other materials. Since diamond has the highest thermal conductivity of any bulk material, layering diamond onto high heat producing electronics (such as optics and transistors) allows the diamond to be used as a heat sink[5][6]. Diamond films are being grown on valve rings, cutting tools, and other objects that benefit from diamond's hardness and exceedingly low wear rate. In each case the diamond growth must be carefully done to achieve the necessary adhesion onto the substrate. Diamond's very high scratch resistance and thermal conductivity, combined with a lower coefficient of thermal expansion than Pyrex glass, a coefficient of friction close to that of Teflon (Polytetrafluoroethylene) and strong lipophilicity would make it a nearly ideal non-stick coating for cookware if large substrate areas could be coated economically.The most important attribute of CVD diamond growth is the ability to control the properties of the diamond produced. In the area of diamond growth the word "diamond" is used as a description of any material primarily made up of sp3 bonded carbon, and there are many different types of diamond included in this. By regulating the processing parameters—especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the method of generating plasma—many different materials that can be considered diamond can be made. Single crystal diamond can be made containing various dopants[7]. Polycrystalline diamond consisting of grain sizes from several nanometers to several micrometers can be grown[8][9]. Some polycrystalline diamond grains are surrounded by thin, non-diamond carbon,while others are not. These different factors affect the diamond's hardness, smoothness, conductivity, optical properties and more.See also。
化学气相沉积法
化学气相沉积法化学气相沉积CVD(Chemical Vapor Deposition)原理CVD(Chemical Vapor Deposition, 化学气相沉积)，指把含有构成薄膜元素的气态反应剂或液态反应剂的蒸气及反应所需其它气体引入反应室，在衬底表面发生化学反应生成薄膜的过程。
在超大规模集成电路中很多薄膜都是采用CVD方法制备。
经过CVD处理后，表面处理膜密着性约提高30%，防止高强力钢的弯曲，拉伸等成形时产生的刮痕。
CVD特点淀积温度低，薄膜成份易控，膜厚与淀积时间成正比，均匀性，重复性好，台阶覆盖性优良。
CVD制备的必要条件1) 在沉积温度下，反应物具有足够的蒸气压，并能以适当的速度被引入反应室;2) 反应产物除了形成固态薄膜物质外，都必须是挥发性的;3) 沉积薄膜和基体材料必须具有足够低的蒸气压。
编辑本段何为cvd,CVD是Chemical Vapor Deposition的简称，是指高温下的气相反应，例如，金属卤化物、有机金属、碳氢化合物等的热分解，氢还原或使它的混合气体在高温下发生化学反应以析出金属、氧化物、碳化物等无机材料的方法。
这种技术最初是作为涂层的手段而开发的，但目前，不只应用于耐热物质的涂层，而且应用于高纯度金属的精制、粉末合成、半导体薄膜等，是一个颇具特征的技术领域。
其技术特征在于:(1)高熔点物质能够在低温下合成;(2)析出物质的形态在单晶、多晶、晶须、粉末、薄膜等多种;(3)不仅可以在基片上进行涂层，而且可以在粉体表面涂层，等。
特别是在低温下可以合成高熔点物质，在节能方面做出了贡献，作为一种新技术是大有前途的。
例如，在1000?左右可以合成a-Al2O3、SiC，而且正向更低温度发展。
CVD工艺大体分为二种:一种是使金属卤化物与含碳、氮、硼等的化合物进行气相反应;另一种是使加热基体表面的原料气体发生热分解。
CVD的装置由气化部分、载气精练部分、反应部分和排除气体处理部分所构成。
气相沉积CVD、PVD简介
气相沉积简介CVD(Chemical Vapor Deposition,化学气相沉积），指把含有构成薄膜元素的气态反应剂或液态反应剂的蒸气及反应所需其它气体引入反应室，在衬底表面发生化学反应生成薄膜的过程。
在超大规模集成电路中很多薄膜都是采用CVD方法制备。
经过CVD处理后，表面处理膜密着性约提高30%，防止高强力钢的弯曲，拉伸等成形时产生的刮痕。
特点沉积温度低，薄膜成份易控，膜厚与淀积时间成正比，均匀性，重复性好，台阶覆盖性优良。
制备的必要条件1）在沉积温度下，反应物具有足够的蒸气压，并能以适当的速度被引入反应室；2）反应产物除了形成固态薄膜物质外，都必须是挥发性的；3）沉积薄膜和基体材料必须具有足够低的蒸气压。
PVD是英文Physical Vapor Deposition（物理气相沉积）的缩写，是指在真空条件下，采用低电压、大电流的电弧放电技术，利用气体放电使靶材蒸发并使被蒸发物质与气体都发生电离，利用电场的加速作用，使被蒸发物质及其反应产物沉积在工件上。
涂层技术增强型磁控阴极弧：阴极弧技术是在真空条件下，通过低电压和高电流将靶材离化成离子状态，从而完成薄膜材料的沉积。
增强型磁控阴极弧利用电磁场的共同作用，将靶材表面的电弧加以有效地控制，使材料的离化率更高，薄膜性能更加优异。
过滤阴极弧：过滤阴极电弧(FCA )配有高效的电磁过滤系统，可将离子源产生的等离子体中的宏观粒子、离子团过滤干净，经过磁过滤后沉积粒子的离化率为100%，并且可以过滤掉大颗粒，因此制备的薄膜非常致密和平整光滑，具有抗腐蚀性能好，与机体的结合力很强。
磁控溅射：在真空环境下，通过电压和磁场的共同作用，以被离化的惰性气体离子对靶材进行轰击，致使靶材以离子、原子或分子的形式被弹出并沉积在基件上形成薄膜。
根据使用的电离电源的不同，导体和非导体材料均可作为靶材被溅射。
离子束DLC：碳氢气体在离子源中被离化成等离子体，在电磁场的共同作用下，离子源释放出碳离子。
化学气相沉积
1. CVD Process Introduction
Components of DCVD Systems
1. Gas sources
2. Gas feed lines 3. Mass flow controller 4. Reaction chamber 5. Heating and temperature control system
BEOL
IMD 3 M2
IMD 2
IMD 1
PMD
FEOL
P+
N-Well 10
P+
STI
N+
P-Well
N+
1. CVD Process Introduction
DCVD Process Precursors:
Silicon source: TEOS,SiH4, TMS…… Oxygen source: O3 ,TEOS,N2O,O2…… Phosphorus source: TEPO,PH3…… Boron source: TEB,B2H6…… Fluorine: SiF4, NF3…… Nitric source: N2,NH3…… Carbon source: C2H2, C3H6……
Islands grow
Islands grow (cross section) Islands merge
Continuous thin film
1. CVD Process Introduction
(I) (II)
(I):MASS TRANSPORT LIMITED at higher temperature Deposition rate is sensitive to flux concentration insensitive to temperature (II):SURFACE REACTION RATE LIMITED at lower temperature Deposition rate is sensitive to temperature insensitive to flux concentration
催化化学气相沉积名词解释
催化化学气相沉积名词解释催化化学气相沉积（Catalytic Chemical Vapor Deposition，简称CCVD）是化学气相沉积（CVD）技术中的一种重要分支。
这可是一种超级有趣又非常有用的技术呢，下面咱们就好好唠唠它到底是怎么一回事儿。
化学气相沉积，简单来说，就是利用气态的先驱体在一定的条件下发生化学反应，然后在基底表面沉积出固态的薄膜或者材料的一种技术。
那催化化学气相沉积呢，就是在这个过程中加入了催化剂，这可不得了，就像给化学反应注入了一针强心剂一样。
你想啊，在很多化学反应中，反应的进行可能需要很高的温度或者能量，这就像爬山一样，要费好大的劲儿才能到达山顶。
但是有了催化剂就不一样啦，催化剂就像是给爬山的人修了一条捷径，让反应能够在相对温和的条件下就顺利进行。
比如说在制备碳纳米管的时候，如果采用普通的化学气相沉积，可能需要非常高的温度，这不仅对设备的要求极高，而且还很不经济呢。
可是一旦加入了合适的催化剂，比如一些过渡金属催化剂，就能够在较低的温度下让含碳的气态先驱体分解并且在催化剂表面沉积生长出碳纳米管。
这多神奇呀！在催化化学气相沉积中，催化剂的选择那可是相当关键的。
不同的催化剂对反应的活性、选择性都有着很大的影响。
就好比厨师做菜，不同的调料会做出不同口味的菜。
比如说铁催化剂可能对某种特定结构的碳材料生长有很好的催化效果，而镍催化剂可能就更适合另外一种结构的碳材料生长。
这其中的原理啊，和催化剂的原子结构、电子性质等都有着千丝万缕的联系。
从反应的过程来看，气态先驱体在催化剂表面吸附是第一步。
这就像小昆虫被蜘蛛网粘住一样，先驱体分子被吸附在催化剂表面。
然后呢，在催化剂的作用下发生化学反应，化学键断裂、重组，最后在基底上沉积下来。
这个过程中，反应的温度、压力、气体流量等条件也都在影响着最终沉积材料的质量和性能。
催化化学气相沉积在现代材料科学领域有着广泛的应用。
在电子工业中，它可以用来制备高质量的半导体薄膜。
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A number of forms of CVD are in wide use and are frequently referenced in the literature. These processes differ in the means by which chemical reactions are initiated (e.g., activation process) and process conditions.∙Classified by operating pressure:o Atmospheric pressure CVD (APCVD) – CVD processes at atmospheric pressure.o Low-pressure CVD(LPCVD) –CVD processes at subatmospheric pressures.[1] Reduced pressures tend to reduce unwantedgas-phase reactions and improve film uniformity across thewafer. Most modern CVD processes are either LPCVD or UHVCVD.o Ultrahigh vacuum CVD(UHVCVD) –CVD processes at a very low pressure, typically below 10−6Pa (~10−8torr). Note that inother fields, a lower division between high and ultra-highvacuum is common, often 10−7 Pa.∙Classified by physical characteristics of vapor:o Aerosol assisted CVD (AACVD) – A CVD process in which the precursors are transported to the substrate by means of aliquid/gas aerosol, which can be generated ultrasonically.This technique is suitable for use with non-volatileprecursors.o Direct liquid injection CVD(DLICVD) –A CVD process in which the precursors are in liquid form (liquid or solid dissolvedin a convenient solvent). Liquid solutions are injected ina vaporization chamber towards injectors (typically carinjectors). Then the precursor vapors are transported to thesubstrate as in classical CVD process. This technique issuitable for use on liquid or solid precursors. High growthrates can be reached using this technique.∙Plasma methods (see also Plasma processing):o Microwave plasma-assisted CVD (MPCVD)o Plasma-Enhanced CVD (PECVD) – CVD processes that utilize plasma to enhance chemical reaction rates of the precursors.[2]PECVD processing allows deposition at lower temperatures,which is often critical in the manufacture of semiconductors.o Remote plasma-enhanced CVD (RPECVD) – Similar to PECVD except that the wafer substrate is not directly in the plasmadischarge region. Removing the wafer from the plasma regionallows processing temperatures down to room temperature.∙Atomic layer CVD(ALCVD) –Deposits successive layers of different substances to produce layered, crystalline films. See Atomic layer epitaxy.∙Combustion Chemical Vapor Deposition (CCVD) – nGimat's proprietary Combustion Chemical Vapor Deposition process is anopen-atmosphere, flame-based technique for depositinghigh-quality thin films and nanomaterials.∙Hot wire CVD (HWCVD) – also known as catalytic CVD (Cat-CVD) or hot filament CVD (HFCVD). Uses a hot filament to chemicallydecompose the source gases.[3]∙Metalorganic chemical vapor deposition (MOCVD) – CVD processes based on metalorganic precursors.∙Hybrid Physical-Chemical Vapor Deposition (HPCVD) – Vapor deposition processes that involve both chemical decomposition of precursor gas and vaporization of a solid source.∙Rapid thermal CVD (RTCVD) – CVD processes that use heating lamps or other methods to rapidly heat the wafer substrate. Heating only the substrate rather than the gas or chamber walls helps reduce unwanted gas phase reactions that can lead to particle formation.∙Vapor phase epitaxy (VPE)UsesIntegrated circuitsVarious CVD processes are used for integrated circuits(ICs). Particular materials are deposited best under particular conditions.PolysiliconPolycrystalline silicon is deposited from silane (SiH4), using the following reaction:SiH4→ Si + 2 H2This reaction is usually performed in LPCVD systems, with either pure silane feedstock, or a solution of silane with 70–80% nitrogen. Temperatures between 600 and 650 °C and p ressures between 25 and 150 Pa yield a growth rate between 10 and 20 nm per minute. An alternative process uses a hydrogen-based solution. The hydrogen reduces the growth rate, but the temperature is raised to 850 or even 1050 °C to compensate.Polysilicon may be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber. Diborane increases the growth rate, but arsine and phosphine decrease it.Silicon dioxideSilicon dioxide (usually called simply "oxide" in the semiconductor industry) may be deposited by several different processes. Common sourcegases include silane and oxygen, dichlorosilane (SiCl2H2) and nitrousoxide(N2O), or tetraethylorthosilicate(TEOS; Si(OC2H5)4). The reactionsare as follows[citation needed]:SiH4 + O2→ SiO2+ 2 H2SiCl2H2+ 2 N2O → SiO2+ 2 N2+ 2 HClSi(OC2H5)4→ SiO2+ byproductsThe choice of source gas depends on the thermal stability of the substrate; for instance, aluminium is sensitive to high temperature. Silane deposits between 300 and 500 °C, dichlorosilane at around 900 °C, and TEOS between 650 and 750 °C, resulting in a layer of low- temperature oxide (LTO). However, silane produces a lower-quality oxide than the other methods (lower dielectric strength, for instance), and it deposits non conformally. Any of these reactions may be used in LPCVD, but the silane reaction is also done in APCVD. CVD oxide invariably has lower quality than thermal oxide, but thermal oxidation can only be used in the earliest stages of IC manufacturing.Oxide may also be grown with impurities (alloying or "doping"). This may have two purposes. During further process steps that occur at high temperature, the impurities may diffuse from the oxide into adjacent layers (most notably silicon) and dope them. Oxides containing 5–15% impurities by mass are often used for this purpose. In addition, silicon dioxide alloyed with phosphorus pentoxide ("P-glass") can be used to smooth out uneven surfaces. P-glass softens and reflows at temperatures above 1000 °C. This process requires a phosphorus concentra tion of at least 6%, but concentrations above 8% can corrode aluminium. Phosphorus is deposited from phosphine gas and oxygen:4 PH3 + 5 O2→ 2 P2O5+ 6 H2Glasses containing both boron and phosphorus (borophosphosilicate glass, BPSG) undergo viscous flow at lower temperatures; around 850 °C is achievable with glasses containing around 5 weight % of both constituents, but stability in air can be difficult to achieve. Phosphorus oxide in high concentrations interacts with ambient moisture to produce phosphoric acid. Crystals of BPO4can also precipitate from the flowing glass on cooling; these crystals are not readily etched in the standard reactive plasmas used to pattern oxides, and will result in circuit defects in integrated circuit manufacturing.Besides these intentional impurities, CVD oxide may contain byproducts of the deposition process. TEOS produces a relatively pure oxide, whereas silane introduces hydrogen impurities, and dichlorosilane introduces chlorine.Lower temperature deposition of silicon dioxide and doped glasses from TEOS using ozone rather than oxygen has also been explored (350 to 500 °C). Ozone glasses have excellent conformality but tend to be hygroscopic –that is, they absorb water from the air due to the incorporation of silanol (Si-OH) in the glass. Infrared spectroscopy and mechanical strain as a function of temperature are valuable diagnostic tools for diagnosing such problems.Silicon nitrideSilicon nitride is often used as an insulator and chemical barrier in manufacturing ICs. The following two reactions deposit nitride from the gas phase:3 SiH4 + 4 NH3→ Si3N4+ 12 H23 SiCl2H2+ 4 NH3→ Si3N4+ 6 HCl + 6 H2Silicon nitride deposited by LPCVD contains up to 8% hydrogen. It also experiences strong tensile stress, which may crack films thicker than 200 nm. However, it has higher resistivity and dielectric strength than most insulators commonly available in microfabrication (1016Ω·cm and 10 M V/cm, respectively).Another two reactions may be used in plasma to deposit SiNH:2 SiH4 + N2→ 2 SiNH + 3 H2SiH4 + NH3→ SiNH + 3 H2These films have much less tensile stress, but worse electrical properties (resistivity 106 to 1015Ω·cm, and dielectric strength 1 to 5 MV/cm).[4]MetalsSome metals (notably aluminium and copper) are seldom or never deposited by CVD. As of 2010, a commercially cost effective, viable CVD process for copper did not exist, though copper formate, copper(hfac)2, Cu(II) ethyl acetoacetate, and other precursors have been used. Copper deposition of the metal has been done mostly by electroplating, in order to reduce the cost. Aluminum can be deposited from tri-isobutyl aluminium (TIBAL), triethyl/methyl aluminum (TEA,TMA), or dimethylaluminum hydride (DMAH), but physical vapor deposition methods are usually preferred.[citation needed]However, CVD processes for molybdenum, tantalum, titanium, nickel, and tungsten are widely used[citation needed]. These metals can form useful silicides when deposited onto silicon. Mo, Ta and Ti are deposited by LPCVD, from their pentachlorides. Nickel, molybdenum, and tungsten can be deposited at low temperatures from their carbonyl precursors. In general, for an arbitrary metal M, the reaction is as follows:2 MCl5 + 5 H2→ 2 M + 10 HClThe usual source for tungsten is tungsten hexafluoride, which may be deposited in two ways:WF6→ W + 3 F2WF6 + 3 H2→ W + 6 HFDiamondColorless gem cut from diamond grown by chemical vapor depositionCVD can be used to produce synthetic diamond by creating the circumstances necessary for carbon atoms in a gas to settle on a substrate in crystalline form.CVD of diamond has received a great deal of attention in the materials sciences because it allows many new applications of diamond that had previously been considered too difficult to make economical. CVD diamond growth typically occurs under low pressure(1–27 kPa; 0.145–3.926 psi;7.5-203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically includehydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others. The energy source is intended to generate a plasma in which the gases are broken down and more complex chemistries occur. The actual chemical process for diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.The advantages to CVD diamond growth include the ability to grow diamond over large areas, the ability to grow diamond on a substrate, and the control over the properties of the diamond produced. In the past, when high pressure high temperature (HPHT) techniques were used to produce diamond, the diamonds were typically very small free standing diamonds of varying sizes. With CVD diamond growth areas of greater than fifteen centimeters (six inches) diameter have been achieved and much larger areas are likely to be successfully coated with diamond in the future. Improving this ability is key to enabling several important applications.The ability to grow diamond directly on a substrate is important because it allows the addition of many of diamond's important qualities to other materials. Since diamond has the highest thermal conductivity of any bulk material, layering diamond onto high heat producing electronics (such as optics and transistors) allows the diamond to be used as a heat sink[5][6]. Diamond films are being grown on valve rings, cutting tools, and other objects that benefit from diamond's hardness and exceedingly low wear rate. In each case the diamond growth must be carefully done to achieve the necessary adhesion onto the substrate. Diamond's very high scratch resistance and thermal conductivity, combined with a lower coefficient of thermal expansion than Pyrex glass, a coefficient of friction close to that of Teflon (Polytetrafluoroethylene) and strong lipophilicity would make it a nearly ideal non-stick coating for cookware if large substrate areas could be coated economically.The most important attribute of CVD diamond growth is the ability to control the properties of the diamond produced. In the area of diamond growth the word "diamond" is used as a description of any material primarily made up of sp3 bonded carbon, and there are many different types of diamond included in this. By regulating the processing parameters—especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the method of generating plasma—many different materials that can be considered diamond can be made. Single crystal diamond can be made containing various dopants[7]. Polycrystalline diamond consisting of grain sizes from several nanometers to several micrometers can be grown[8][9]. Some polycrystalline diamond grains are surrounded by thin, non-diamond carbon,while others are not. These different factors affect the diamond's hardness, smoothness, conductivity, optical properties and more.See also。