现代光刻机的发展历程与未来展望

Development and future outlook of modern lithography machines

在过去的30多年,集成电路芯片的制造工艺通过不断减小芯片特征尺寸来提高芯片性能、降低芯片成本,而其中的光刻工艺一直是实现特征尺寸缩小的主要推动技术。光刻工艺中的细小图形需要通过光刻机来制作。可以说,光刻机的发展历程与芯片制造工艺需求息息相关。早期的光刻机是接触、接近式,极限分辨率周期约为1.5μm。随着技术节点的不断发展,线宽逐渐缩小,光刻机也由之前简单的接触、接近式结构发展到采用投影物镜成像的结构,即采用一个成像物镜将掩模版上的图形按照一定比例缩小投影到硅片上的光刻胶薄膜上,以获得更高的分辨率与更低的缺陷率。投影式光刻机的成像比例一般是4∶1。目前深紫外光刻机和低数值孔径的极紫外光刻机的极限分辨率周期分别约为76 nm和26 nm。本文以各主流逻辑技术节点中关键层次的设计规则为主线,通过总结各技术节点的工艺窗口,描绘相应的投影式光刻机从g线、i线到氟化氪(Krypton Fluoride,KrF)(248 nm)、氟化氩(Argon Fluoride,ArF)(193 nm)、ArF水浸没式光刻机,最后到最先进的投影式光刻机——极紫外光刻机的发展历程。并详细介绍各个阶段投影式光刻机的重要架构和功能模块,例如光源、照明系统、投影物镜、工件台材料和悬浮方式以及传感器类型等等,并对各个阶段光刻机的各技术指标进行分解。同时也整理了每个阶段光刻机引入的关键技术,尤其是与深紫外光刻机差异较大的极紫外光刻机中的特征技术。

In the past 30 years,the manufacturing process of integrated circuit chips has continuously improved chip performance and reduced chip costs by reducing the size of chip features,and the photolithography process has always been the main driving technology to achieve feature size reduction.The fine patterns in photolithography need to be made using a lithography machine.It can be said that the development of lithography machines is closely related to the requirements of chip manufacturing processes.Early lithography machines were contact or proximity type,with a limit resolution cycle of about 1.5μm.With the continuous development of technology nodes and the gradual reduction of linewidth,lithography machines have also developed from simple contact or proximity structures to structures that use projection lenses for imaging.That is,using an imaging lens to project the pattern on the mask to the photoresist film on the silicon wafer at a certain proportion to obtain higher resolution and lower defect rate.The imaging ratio of the projection lithography machine is generally 4∶1.Currently,the limit resolution cycles of deep ultraviolet lithography machines and low numerical aperture extreme ultraviolet lithography machines are about 76 nm and 26 nm,respectively.This article takes the design rules of key levels in various mainstream logic technology nodes as the main line,summarizes the process windows of each technology node,depicts the development process of the corresponding projection lithography machines from g-line,i-line to Krypton Fluoride(KrF)(248 nm),Argon Fluoride(ArF)(193 nm),ArF immersion lithography machines,and finally to the most advanced projection lithography machines-Extreme Ultraviolet lithography machines.It also introduces in detail the important structures and functional modules of projection lithography machines at each stage,such as light source,illumination system,projection lens,workpiece table material and suspension method,sensor type,etc.,and decomposes the various technical indicators of lithography machines at each stage.At the same time,the key technologies introduced by lithography machines at each stage are also sorted out,especially the feature technologies in extreme ultraviolet lithography machines that differ greatly from deep ultraviolet lithography machines.