Etch Properties of 193nm Resists: Issues and Approaches.

Abstract

Polymer chemistries for 193nm resists are more or less defined and their lithographic performance is quite good to implement 100nm design rules. In spite of the use of high carbon containing adamantane or norbomene moieties in the polymer design, there exists etch selectivity as well as surface roughness issues after treatment with etch plasma. It is very much necessary to modify the etch plasma used for 193 nm resists to improve the surface roughness. Etch rates of several acrylate, methacrylate and hybrid type polymers are measured and compared. While the problem still exists, acrylates in general seem to offer better surface properties than methacrylates. On the process side, a-beam curing of 193nm resists offers improvement in both etch selectivity as well as surface roughness. It was found from the IR spectra of before and after a-beam cured films that ebeam curing reduces the carbonyl groups and compacts the resist film leading to etch improvements. Effects of three different a-beam curing processes (Standard, LT and ESC) on the methacrylate & hybrid type 193nm resists were studied with respect to resin chemistry changes, resist film shrinkage, pattern profiles, etch rates, and CD SEM stability. Etch rate, selectivity and resist surface roughness after etch of both methacrylate and hybrid resists were improved using the a-beam curing process. E-beam curing drastically reduces (from ca. 15% to 2 -5 %) the CD SEM shrinkage; however, considerable shrinkage occurs during the curing process itself.

Investigation of surface modifications of 193 and 248nm photoresist materials during low-pressure plasma etching

“…Consistent with our findings, Padmanaban et al 7 compared the surface roughness of different types of 193 nm photoresist in aggressive fluorocarbon plasmas used for oxide etching. They found that electron beam curing of 193 nm photoresist before plasma exposure strongly improved the etch performance of 193 nm photoresist, with regards to both etching rate and introduction of surface roughness.…”

“…1,2 The decrease of the thickness of 193 nm photoresist materials requires higher plasma etching resistance relative to 248 nm photoresist materials. [5][6][7][8][9][10][11][12][13] In this work, the plasma etching behavior of 193 and 248 nm photoresist is examined in fluorocarbon discharges used for dielectric etching. One issue with 193 nm photoresist materials in plasma etching environments is increased surface roughness as a result of the etch process.…”

Comparing 193 nm photoresist roughening in an inductively coupled plasma system and vacuum beam system

“…As noted above, some groups have studied plasma pre-treatment and VUV/e-beam smoothing effects on 193 nm PR to eliminate LER and LWR [2][3][4][15][16][17][18]. Pargon et al demonstrated that HBr and Ar plasma treatments reduce LWR and attributed the effect to VUV emission (110-210 nm) and low energy ion bombardment [3,4].…”