第三章 微纳制造技术_光刻

单项工艺： 光刻

1. Introduction

Photolithography

• Photo-litho-graphy: latin : light-stone-writing

• Photolithography is an optical means for transferring patterns onto a substrate. It is essentially the same process that is used in lithographic printing.

• Patterns are first transferred to an imagable photoresist layer. • Photoresist is a liquid film that can be spread out onto a

substrate, exposed with a desired pattern, and developed into a selectively placed layer for subsequent processing.

• Photolithography is a binary pattern transfer: there is no gray -scale, color, nor depth to the image.

Key Historical Events in Photolithography

• 1826- Joseph Nicephore Niepce, in Chalon, France, takes the first photograph using bitumen of Judea on a pewter plate, developed using oil of lavender and mineral spirits.

• 1843- William Henry Fox Talbot, in England, develops dichromated gelatin, patented in Britain in 1852.

• 1935- Louis Minsk of Eastman Kodak developed the first synthetic photopolymer, poly(vinyl cinnamate), the basis of the first negative photoresists.

• 1940- Otto Suess of Kalle Div. of Hoechst AG, developed the first diazoquinone-based positive photoresist. • 1954- Louis Plambeck, Jr., of Du Pont, develops the Dycryl polymeric letterpress plate.

transparent glass

Cr patterned film

掩模版

Si 光刻胶 SiO 2 film

Al film Si UV 曝光

Si

显影

Si

图形转移

Si 腐蚀Al film

Patterning by lithography and wet etching

完整的光刻工艺

Wafer with mask film (e.g. SiO2, Al)带有掩

膜的晶圆片

Photoresist coating 旋涂光刻胶

Prebake (softbake)前烘

Mask alignment 对准

Exposure 曝光

Develop-ment 显影

Postbake 后烘

Removal of exposed photoresist 去除曝光的胶

Etching of mask film 腐蚀掩膜

Removal of unexposed resist 去除非曝光的胶

Next process (e.g. implantation, deposition)

掩模板设计软件L-Edit

Starting material for reticle （刻线）

manufacturing is ~800 Å thick

film of chromium （铬）covered with resist and

anti-reflective coating (ARC)

Chromium has very good adhesion and

opaque properties （粘附力好，不透明）

Substrate: quartz glass plate （石英玻璃板）

Patterned by direct writing using e-beam or

laser （电子束或激光直写）

Usually wet etching of Cr after exposure

4 or 5x magnification is normal for projection

litho （投影制版）

Pellicle used for dust protection of reticle

掩模板制作

亮场和暗场掩模板工程

1. Optical proximity correction (OPC)光学邻近校正

High-frequency components of the diffracted light is lost because of finite apertures,

circular lenses etc

Ends and bows of narrow lines are not ideal（端面和弯曲的地方不理想）

OPC: Clever mask engineering based on software algoritms can

compensate some of this error: （软件算法补偿）

掩膜版工程

2. Phase shifting masks (PSM) （相移掩膜）

Introducing material which shifts the light by 180°for adjacent mask patterns barely resolved improved resolution

Intensity ∝ (Electrical amplitude)2Positive vs. Negative Photoresist 正性和负性光刻胶