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Pattern deformation during SEM inspection has been investigated for different types of 193 nm positive resists. The mechanism of the CD changes is discussed based on the slimming rate analyses as well as on the a-beam penetration depth. As a general tendency, the methacrylate resists exhibit faster line width reduction than the cycloolefin-maleic anhydride (COMA) systems; however, other resist components as well as CD SEM settings play an important role. Based on the exposure time vs. CD loss, the line width slimming (LWS) is found to proceed in three steps, which are assigned as: (1) chemical change of outer resist layer, (2) evaporation of volatiles and (3) bulk chain scission or deprotection. Countermeasures for CD degradation are proposed from both the formulation and process sides. A calculation of a-beam penetration depth suggests that deprotection, chain scission and other reactions occur in the first 20-40 nm, and these reaction rates combined with thermal effects determine LWS. The CD SEM measurement method has been improved to minimize a-beam exposure and to spread out the thermal load over a larger period of time. An optimized formulation exhibits less than 0.2% LWS per measurement with the improved CD measurement program.

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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.

San 136-1, Ami-ri, Bubal-eub, Ichon-si, Korea This paper discusses the 193 nm lithography of contact holes with various pitches for 100 nm node. We have studied 193 nm contact hole resists in view of resist components, process conditions and optical settings. Sidewall roughness was improved by optimizing photoacid generators. Side lobes were eliminated by applying higher post exposure bake temperature or modification of polymers. The influence of optical settings, types of masks and mask bias was discussed with simulation and lithographic results and guidelines for better resolution and iso-dense bias were proposed. The optimized formulation, AZ® AXTM l O50P has a high resolution combined with a large depth of focus and an iso-dense overlap window (130 nm (NA=0.63) DOF 0.38 µm C Exposure latitude 10%).