A sub‐0.5 μm bilevel lithographic process using the deep‐UV electron‐beam resist p(si‐cms)

Abstract

Optimization of the deep‐UV and electron‐beam lithographic properties of a copolymer of trimethylsilylmethyl methacrylate (SI) and chloromethylstyrene (CMS), P(SI‐CMS), within a weight average molecular weight range of 1.4 to 4.1 × 105 and 90 to 93 mole percent SI composition has been achieved. The solubility behavior of P(SI‐CMS) resist was examined using the Hansen 3‐dimensional solubility parameter model and dissolution rate measurements. Swelling of the resist has been minimized through the identification of a single component developer (2‐propanol) and rinse (water) system. For the material containing 90 mole percent SI (14.9 weight percent Si) and M̄ω = 1.4 × 105, the sensitivity to 248 nm radiation is 65 mJ/cm2 and to electron‐beam exposure is 3.4 μC/cm2 at 20 kV. This material Is applicable to bilevel lithographic processes, and the O2 reactive ion etching (RIE) rate is 16 times slower than standard hard‐baked photoresist. Using a He/O2(60/40) RIE pattern transfer process, 0.4 μm line/space patterns have been resolved in a 1.3 μm bilayer structure for deep‐UV exposures, and 0.25 μm imaging has been demonstrated in a 0.7 μm thick planarizing layer using electron beam irradiation. The loss in linewidth associated with the 0.25 μm process is ∼0.04 μm.

Lithographic Resist Materials Chemistry

“…Other resists that exhibit acceptable thermal prop erties and etching resistance for bilevel applications are copolymers of trimethylsilyl- (36,37) and trimethylstanylstyrene (36) with chlorostyrene. Additionally, copolymerization of trimethylsilylmethyl methacrylate with chloromethylstyrene yields a viable electron-beam and deep-UV negative resist even though the homopolymer of the silicon-containing methacrylate is a posItive acting material (38). In this case, at the exposure doses employed, crosslinking of the chloromethylstyrene units in this resist pre dominates, and the silyl metharylate serves only to provide the source of silicon in the resist.…”

Studies of 1 and 2 keV electron beam lithography using silicon containing P(SI–CMS) resist

“…5 It is a copolymer of trimethysilylmethyl methacrylate ͑SI͒ and chloromethylstyrene ͑CMS͒. Recently, studies have shown P͑SI-CMS͒ to be a high resolution, high contrast, and high sensitivity resist.…”