Study of the fundamental contributions to line edge roughness in a 193 nm, top surface imaging system

Abstract

Top surface imaging systems based on vapor phase silylation have been investigated for use at a variety of wavelengths. This approach to generating high aspect ratio, high resolution images held great promise particularly for 193 nm and EUV lithography applications. Several 193 nm top surface imaging ͑TSI͒ systems have been described that produce very high resolution ͑low k factor͒ images with wide process latitude. However, because of the line edge roughness associated with the final images, TSI systems have fallen from favor. In fact, TSI does not appear in the strategy or plan for any imaging technology at this time. Most of the 193 nm TSI systems that have been studied are based on poly͑p-hydroxystyrene͒ resins. These polymers have an unfortunate combination of properties that limit their utility in this application. These limiting properties include ͑1͒ high optical density, ͑2͒ poor silylation contrast, and ͑3͒ low glass transition temperature of the silylated material. These shortcomings are related to inherent polymer characteristics and are responsible for the pronounced line edge roughness in the poly͑p-hydroxystyrene͒ systems. We have synthesized certain alicyclic polymers that have higher transparency and higher glass transition temperatures. Using these polymers, we have demonstrated the ability to print high resolution features with very smooth sidewalls. This article describes the synthesis and characterization of the polymers, their application to top surface imaging at 193 nm, and the analysis that was used to tailor the processing and the polymer's physical properties to achieve optimum imaging.

Negative resist image by dry etching as a novel top surface imaging process for ion-beam lithography

“…The Positive Resist Image by Dry Etching (PRIME) process [11] , by comparison, is a single layer positive resist system incorporating e-beam exposure, near UV exposure, silylation and dry development. More recently, TSI was applied to 193nm lithography [12] , 157nm lithography [13,14] and to the Extreme Ultraviolet lithography (EUVL) at 13.5nm [15] , successfully solving the higher optical absorbance problem of organic resists under these exposure wavelengths and achieving resolution deep into the nanometer region.…”

Direct thin-film imaging, DTFI, based on PMOD (photochemical metal-organic deposition) methodology

“…The resulting structure is shown in Figure 4. It is not yet an optimal process so we see the formation of "grass" in the etch field (7,8). The "grass" is thought to be produced by etch redeposition.…”

“…Si02 or Si3N4) is shown in Figure 1 . This technology is not without its problems and limitations, e.g., "grass" formation and line edge roughness has been discussed elsewhere (7,8) Use ofa directly patterned PMOD Ti02 hard mask offers process simplification and increased etch selectivity relative to traditional TFI processes. The work presented here demonstrates the use of a direct thin-film imaging, DTFI, technology based on PMOD process of a directly patterned hard mask to form ofhigh aspect ratio features for use as etch-masks or plating templates in MEMS fabrication.…”

Two-step modified NERIME process using combined focused ion beam lithography and plasma etching

“…More recently, TSI was applied to 193nm lithography [12] , 157nm lithography [13,14] and to the Extreme Ultraviolet lithography (EUVL) at 13.5nm [15] , successfully solving the higher optical absorbance problem of organic resists under these exposure wavelengths and achieving resolution deep into the nanometer region.…”