RADIOISOTOPES

The dissolution characteristics of a chemically amplified electron beam (EB) resist composed of partially tert-butoxycarbonyl group (tBOC) protected poly(p-vinylphenol)(PVP), a dissolution inhibitor, and an acid generator were investigated. The resist sensitivity was improved with decreasing tBOC ratio of the matrix resin. As the tBOC ratio increased, the resolution of the resist was better. SEM observation of the pattern profile was carried out to investigate the sensitivity and the resolution of the resist. The optimum tBOC ratio was 23.8％. As dissolution inhibitors, hydroquinone protected by a tert-butoxycarbonyl group(B-HQ) and isophthalic acid protected by a tert-butyl group(B-IP) are used. Dissolution inhibitors (B-HQ and B-IP) become dissolution promoters (HQ and IP) after exposure. The dissolution rate of the resist consisting of B-IP was faster than that of B-HQ in the exposed area. Pka of IP is smaller than that of HQ, and the acidity of IP is higher than that of HQ. Therefore IP enhances the solubility of the matrix resin in the alkaline developer. We evaluated the dependence of sensitivity of the resist upon acid generators. Triphenylsulfonium triflate, Diphenyliodonium triflate, Triphenylsulfonium antimonate, and Diphenyliodonium antimonate were used. When iodonium ion was used as cation, the sensitivity of the resist was better. When antimonate ion as anion was used, the sensitivity of the resist was better.