David A. Mixon

Preliminary lithographic characteristics of an all-organic chemically amplified resist formulation for single-layer deep-UV lithography

When used in conjunction with a nitrobenzylester photoacid generator, poly(t-butoxycarbonyloxy-styrene-sulfone) deep-UV resist films exhibit high contrast, good resolution and linewidth stability. Use of overcoat materials dramatically reduce the surface inhibition problems, improve the latent image stability (time delay) and enhance the sensitivity by isolating the resist surface from environmental contaminants that react with the photogenerated acid. The photospeed of the all organic CAMP formulation is lower compared to the arsenate based system but can be improved by using more aggressive PEB conditions. Coded, 0.35 micrometers l/s pairs could be resolved in 1 micrometers thick resist films at a dose of 20-30 mJ/cm2. The exposure latitude is approximately equals 25% for 0.5 micrometers features, upon exposure with a GCA prototype deep-UV exposure tool with a NA equals 0.35 and 5x reduction optics. This paper will discuss the resolution, depth-of-focus, exposure latitude and processing characteristics obtained during the evaluation of this chemically amplified resist.

Dry etch patterning of chrome on glass optical masks using P(SI-CMS) resist

Poly(trimethylsilylmethyl methacrylate-co-chloromethylstyrene) P(SI-CMS) has been designed to function as a negative-acting electron beam sensitive resist. This material is shown to be applicable to processes in which the chrome layer of 1X, 5X, and phase shifting masks is patterned via plasma etching. P(SI-CMS) containing 90 mole % trimethylsilylmethyl methacrylate and 10 mole % chloromethylstyrene exhibits thermal properties (Tg > 80 degree(s)C; Td > 250 degree(s)C) which provide stability in reactive ion etch environments. In a Cl2 - O2 plasma P(SI.90-CMS.10) resist etches a factor of 4.25 slower than chromium, and 16 times slower than novolac based resists.

193 nm lithography using a negative acting P(SI-CMS) resist

Abstract Copolymers of trimethysilylmethyl methacrylate and chloromethylstyrene [P(SI-CMS)] have been formulated as negative resists for exposure at 193 nm. To achieve maximum sensitivity, absorption has been targeted so that the amount of radiation exposing the base of a given film thickness is I 0 e −1 , leading to an optimum optical absorbance of log 10 e , or 0.434. Through control of the mole ratio of the monomers in the P(SI-CMS) copolymer, optimum response has been tailored for coating thicknesses from 2000 A to 5500 A. Optimal formulations yield working sensitivities of from 4 to 20 mJ/cm 2 for materials having a M w of 4 × 10 4 g/mole, with resolution demonstrated below 0.4 μm. Resists exhibit etching resistance in O 2 RIE and are suitable for application in both single layer and bi-layer processes.

Identification of sensitive positive and negative working resist materials for proximity X-ray lithography

Proximity x-ray lithography represents one of the emerging technologies currently under investigation for advanced circuit design fabrication. A pulsed laser point source proximity print stepper is currently being evaluated for the feasibility of fabricating working devices having design rules in the range of 0.12-0.18@mm. Both conventional and chemically amplified (CA) positive and negative working resists have been evaluated on the stepper and exhibit sensitivities in the range of 15-60mJ/cm^2. Multi- and single component positive CA resists represent the leading candidates for use in device fabrication. Negative resists provide high sensitivity but have more limited resolution capability vs. positive working materials.

Design, synthesis and characterization of poly(trimethylsilylmethyl methacrylate-co-chloromethyl styrene) for 193-nm exposure

Requirements of materials for lithography at 193 nm limit single layer resist candidates to those with high optical transmission. A random copolymer of trimethylsilymethyl methacrylate (SI) and chloromethyl styrene (CMS), [P(SI-CMS)], has been shown to be highly sensitive negative 193 nm resist in both bi-layer and single layer modes. Such resists show maximum sensitivity with an optical absorbance of the coating of log10e, or 0.434. Through control of the mole ratio of the monomers in the P(SI-CMS) copolymer, absorbance values have been optimized for film thicknesses of 0.2 - 0.3 micrometers for 90:10 SI:CMS, 0.35 - 0.45 micrometers for 95:5 SI:CMS and 0.55 - 0.65 micrometers for 98:2 SI:CMS. Optical absorbance of the CMS is at a maximum in the 190 to 205 nm range, allowing the copolymer to be tailored for a large degree of crosslinking at a relatively low CMS concentration. Spray development of these materials is performed with ethanol, followed by a two step methanol/isopropanol-water rinse. Sensitivities are on the order of 4 to 20 mj/cm2 at Mw near 40,000 g/mol. Furthermore, these ratios have been found to produce optimum O2 etch resistance.