Polymers, resist compositions and patterning process

#This invention relates to polymers useful as the base resin in resist compositions suited for microfabrication. It also relates to resist compositions, especially chemical amplification resist compositions comprising the polymers, and a patterning process using the same.

#In the drive for higher integration and operating speeds in LSI devices, the pattern rule is made drastically finer. The rapid advance toward finer pattern rules is grounded on the development of a projection lens with an increased NA, a resist material with improved performance, and exposure light of a shorter wavelength. To the demand for a resist material with a higher resolution and sensitivity, chemical amplification positive working resist materials which are catalyzed by acids generated upon light exposure are effective as disclosed in U.S. Pat. No. 4,491,628 and U.S. Pat. No. 5,310,619 (JP-B 2-27660 and JP-A 63-27829). They now become predominant resist materials especially adapted for deep UV lithography.

#Also, the change-over from i-line (365 nm) to shorter wavelength KrF excimer laser (248 nm) brought about a significant innovation. Resist materials adapted for KrF excimer lasers enjoyed early use on the 0.30 micron process, passed through the 0.25 micron rule, and currently entered the mass production phase on the 0.18 micron rule. Engineers have started investigation on the 0.10 micron rule or less, with the trend toward a finer pattern rule being accelerated.

#Examples of the invention are given below by way of illustration and not by way of limitation. The abbreviations used herein are THF for tetrahydrofuran, GPC for gel permeation chromatography, NMR for nuclear magnetic resonance, Mw for weight average molecular weight, and Mn for number average molecular weight. Mw/Mn is a molecular weight distribution or dispersity.

#Reaction to Introduce Tert-Butyl Carboxylate Units into Polymer 1

#In a 500-ml flask, 0.75 g of sodium hydride was admitted and thoroughly washed with hexane, to which 50 ml of THF was added. A solution of 20 g of Polymer 1, shown below, in 100 ml of THF was added dropwise to the flask at room temperature. Agitation was continued for 20 hours at the temperature. Thereafter, 5.50 g of tert-butyl bromoacetate was added dropwise to the flask at room temperature, followed by 20 hours of agitation. 18