chapter 6C, Normal Incidence (Multilayer) Collector Contamination

Excerpt

6C.1 Introduction

Current lithography using 193-nm light can be extended down to the 45-nm and even 32-nm nodes using various resolution enhancement techniques such as immersion and double patterning. However, to produce smaller and faster chips by the year 2010 or 2011 for the 22-nm mode, next-generation lithography (NGL) methods such as extreme ultraviolet lithography (EUVL) will be needed. EUVL requires EUV light from a plasma source to be collected using reflective mirror optics. The economic feasibility of EUVL commercialization will require these mirror components to have a longer lifetime because frequent replacement would lead to an unacceptable cost of ownership (CoO).

Before EUVL technology can be put into high-volume use, several critical issues must be solved. One challenging problem in moving EUVL from the drawing board to the manufacturing floor is the need to operate a high-power light source in conjunction with the collector optics for light capture. Currently, two prospects for EUV light sources are being considered. The first is a laser-produced plasma (LPP), which uses a pulsed laser to ablate fuel material (xenon [Xe], tin [Sn], or lithium [Li]) and create the high temperatures required for EUV light generation. The second option is a discharge-produced plasma (DPP), which uses some type of pinch (dense plasma focus, z-pinch, etc.) to compress plasmas to high temperatures, generating the ion species required for EUV light emission.