Limits to etch resistance for 193-nm single-layer resists

Abstract

An important aspect ofsingle-layer resist use at 193-nm is the inherently poor etch resistance ofthe polymers currently under evaluation for use. In order to provide the information necessary for resist process selection at 1 93 urn, we have projected the ultimate etch resistance possible in 193-nm transparent polymers based on a model we have developed. First, a data base ofetch rates was assembled for various alicyclic methacrylates. This data base has been used to develop an empirical structure-property relationship for predicting polymer etch rates relative to novolac-based resist.This relationship takes the functional form NormalizedRate -3.8Or +6.71r -4.42r+ 2.10, where r is the mass fraction ofpolymer existing as cyclic carbon. From this analysis, it appears as though methacrylate resists equal in etch resistance to deep UV resists will be possible. Early generations of methacrylate-based 1 93-nm resists were also evaluated in actual IC process steps, and those results are presented with a briefdiscussion ofhow new plasma etch chemistries may be able to further enhance resist etch selectivity.

Polymer Structural Variation Towards Enhancing KrF Resist Lithographic Properties.

“…The low etch rates for these resists may be explained on the basis of the high C/H ratio of the bulky groups and the low volatility of the corresponding bulky alcohols which might have been generated as a result of heat induced decomposition of the acetal. Alicyclic polymers similar to nopyl acetal are known to have reasonably high etch resistance [19]. The "bulky" acetal based resists show improved resolution compared to the corresponding tertiarybutyl acetal based resist ( Figure 6) reflecting the higher contrast of the former.…”

Design considerations for ultraviolet-nanoimprint lithography resists

“…Dry etching resistance increases with decreasing Ohnishi parameter, defined as the value obtained by dividing the total number of atoms in the chemical structure by the difference between the number of oxygen atoms and carbon atoms. 36,37 This is the same approach as is used in photolithography.…”

Differences in erosion mechanism and selectivity between Ti and TiN in fluorocarbon plasmas for dielectric etch

“…Low mask ER and correspondingly high ES are found for organic masks with low oxygen content as expressed by the Ohnishi parameter and high content of aromatic structures as described by the ring-parameter. 31,32 In contrast to organic masks, metallic masks such as Ti and TiN are difficult to etch in FC plasmas and intrinsically etch-resistant. In order to understand how differences in material composition and density between Ti and TiN impact ER, we compared the erosion of the two materials in CF 4 /Ar and C 4 F 8 /Ar plasmas.…”