Resist fundamentals for resolution, LER and sensitivity (RLS)performance tradeoffs and their relation to micro-bridging defects

摘要

High NA immersion and EUV lithography processes are challenged to meet stringent control requirements for the 22 nmnode and beyond. Lithography processes must balance resolution, LWR and sensitivity (RLS) performance tradeoffswhile scaling resist thickness to 100 nm and below". Hardware modules including coat, bake and development seek toenable resist processes to balance RLS limitations. The focus of this paper is to study the fundamentals of the RLSperformance tradeoffs through a combination of calibrated resist simulations and experiments. This work seeks to extend the RLS learning through the creation of calibrated resist models that capture the exposurekinetics, acid diffusion properties, deprotection kinetics and dissolution response as a function of PAG loading in a 193nm polymer system. The calibrated resist models are used to quantify the resolution and sensitivity performancetradeoffs as well as the degradation of resist contrast relative to image contrast at small dimensions. Calibrated resist simulations are capable of quantifying resolution and sensitivity tradeoffs, but lack the ability to modelLWR. LWR is challenging to simulate (lattice models) and to measure; due to the dependence on spectral frequency.This paper seeks to use micro-bridging experiments as means to better understand the statistical nature of LWR. Micro-bridging analysis produces a statistical distribution of "discrete bridging events" that encompasses practical variationsacross scanner, track and resist. Micro-bridging and LWR experiments are done using a 1.2 NA immersion system on 45nm space structures (90 nm pitch) as a means to demonstrate the concept, but the methodology can also be used to studyEUVL processes as the technology matures. The understanding of the RLS performance tradeoffs enables TEL todevelop future hardware and processes that support industry scaling goals.