硅片电子制造

A Pentium 4 procesistors
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Silicon Micromachines
• The other application is micromachines, also called the microelectricmechanical system (MEMS), which have the potential of making the computer obsolete
• Inductively coupled plasma (ICP) reactors have been introduced for silicon RIE process leading to the deep reactive ion etching (DRIE) technique. – Higher plasma density – Higher etching rate, either for anisotropic and isotropic etching – Higher aspect ratio (AR) – Reduction of parasitic effects
• The micromachines include:
– Fuel cells – DNA chips – ……
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Microfabrication
• Silicon crystal structure is regular, well-understood, and to a large extent controllable.
• It can be applied in both MEMS and traditional precision manufacturing.
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LIGA Process—X-ray lithography
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LIGA Process—Electroplating
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LIGA Process—Molding
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Silicon Review
• In a perfect crystal, each of silicon’s four outer electrons form covalent bonds, resulting in poor electron mobility (i.e. insulating)
• Guckel (U. Wisc) integrated LIGA with existed semiconductor industry so that LIGA becomes one major micro fabrication process.
• Today, more and more prototypes have been fabricated. And some LIGA companies have been founded and provided professional services to users.
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Process of Microfabrication
Single crystal growing
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Silicon Circuits
• Silicon makes the transistors
• Transistors can be made to very large scale integration (VLSI) and ultralarge scale integration (ULSI)
• Metals
– Used in electrodeposition phase to form a mould – Nickel is a popular choice.
• Polymer again
– Used in molding period – The final LIGA product is usually made of polymers
• It is all about control: the size of a transistor is 1 m, the doping must therefore less than have of that
• How to control?
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Microfabrication Techniques
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LIGA Materials
• Polymers
– Used in X-ray lithography period. The materials must be able to allow photochemical reaction under exposure under X-ray
– Thick PMMA is a popular choice
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Why Is LIGA Interesting?
• Very high aspect ratio structures can be achieved
– Height(typical) 20-500 μm, this can not be achieved by state of art silicon surface micromachining
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Brief History of LIGA
• Electrodeposition and X-ray lithography
– Romankiw et al at IBM, 1975.
• Adding molding
– Ehrfeld et al at KfK, 1982.
• In Germany, LIGA was initially independent from semiconductor industry.
• Doping silicon with impurities alters electron mobility (i.e. semiconducting)
– Extra electron (“N-type”, with phosphorous, for example)
– Missing electron (“P-type”, with boron, for example)
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LIGA Applications
high aspect ratio microstructures
Micro turbine rotor, KfK
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LIGA Applications
Spinneret Capillary, IMM
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Problem Associated with LIGA
– Wet Etching (isotropic, anisotropic) – Dry Etching (physical, chemical, physical-chemical)
• Be able to describe the process of bonding and packaging
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What is LIGA?
• LIGA is a fabrication process for high aspect ratio microstructures consisting of three major process steps.
• X-ray lithography (LI=lithographie) to generate primary microstructures. (DXRL=deep X-ray lithography, UDXRL=ultra-deep X-ray lithography)
• You need to buy a big X-ray source
– expansive
• Need long time to exposure and develop
– Time consuming (several days)
• Other compete technology are rapidly catching up
– LIGA-Like – Si DRIE technology
• The X-ray lithography process can be replaced to reduce the cost.
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LIGA-Like Process Overview
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DRIE System
Plasmalab System 100 Modular ICP-RIE Etching System Oxford Instruments
• Electroplating/Electrodeposition (G=Galvanik) to produce microstructures in metal.
• Molding (A=Abformung) to batch produce secondary microstructures in polymers, metals, ceramics…
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Overview of DRIE
• Reactive ion etching (RIE) is a dry etching method which combines plasma etching and ion beam etching principles. – Choice for most advanced product line – It’s not well suitable for deep etching (>10μm)
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DRIE Applications
Use ICP etcher to create deep etching in silicon substrate
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DRIE Applications
processes, including relative comparisons among them.
– Physical Vapor Deposition (evaporation, sputtering) – Chemical Vapor Deposition
• Be able to describe the basic mechanisms of the subtractive processes, including relative comparisons among them.
Chapter 2, Microfabrication (Electronics Manufacturing)
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Learning Objectives
• Be able to describe the basic processes of microfabrication • Be able to explain the principles of photolithography. • Be able to describe the basic mechanisms of the additive
• Have more material selectivity in final products
– Could be metal, polymer, and even ceramics.
• Vertical and better surface roughness in sidewall
– Vertical slope<1μm/mm, – Surface roughness 0.03-0.05 μm(max. peak to valley)
• The silicon structures were part of an innovative escape mechanism of the Ulysse Nardin "Freak" watch. ( CSEM SA, IMT)
• Silicon parts:
– Lighter – Lower friction coefficient – Insensitive to magnetic fields