New Photoresists with Photoacid Generator in the Backbone
- PDF / 414,789 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 92 Downloads / 214 Views
New Photoresists with Photoacid Generator in the Backbone Hengpeng Wu and Kenneth E. Gonsalves* AZ Electronic Materials, Clariant Corporation, 70 Meister, Somerville, NJ 08876 *Dept. of Chemistry & Cameron Applied Research Center, University of North Carolina, Charlotte, NC 28223 ABSTRACT A photoacid generating (PAG) sulfonium monomer was designed and synthesized. CA resists were prepared based on this PAG monomer. Incorporation of the PAG in the resist backbone offered a few advantages such as high sensitivity and absence of phase separation. These resists proved to be especially useful for low-voltage EB lithography. INTRODUCTION Recently, tremendous efforts have contributed towards the design and synthesis of new polymer materials to be used for microlithography [1,2]. At present, one of the most promising imaging systems is chemically amplified (CA) resists [3]. These resists have been studied intensively due to their high sensitivity, resulting from an acid-catalyzed deprotection pathway. A CA resist usually consists of a polymer matrix and a small molecule photoacid generator. Small molecule PAGs may have limited compatibility with the polymer matrix [4]. It has been reported that the efficiency of acid generation is highly dependent on the compatibility between the PAGs and the polymer matrix [5]. Poor compatibility between the PAGs and the polymer matrix could cause phase separation, non-uniform acid distribution and migration. To alleviate these problems, we designed and synthesized a sulfonium photoacid generating monomer [6 - 9]. Copolymerization of this monomer with various methacrylate monomers led to a series of CA resists with PAG units in the polymer chain, which were found to exhibit excellent film formation behavior due to absence of phase separation often observed in CA resists formulated by physically blending polymer matrix with small molecule PAGs. EXPERIMENTAL DETAILS Synthesis of the PAG monomer All materials were used as received. HCl gas was generated in situ by a reaction of concentrated sulfuric acid (98 %) and analytical-grade hydrochloric acid (36.5 %). As outlined in Figure 1, phenol 1 (0.25 mol) and dimethyl sulfoxide (0.25 mol) were dissolved in 200 ml of methanol in a three-necked flask fitted with a thermometer and the solution was cooled to below 5 oC. Under stirring, anhydrous HCl was slowly bubbled through the solution until a white solid appeared. The dissolved HCl and most of the solvent were removed under reduced pressure in a rotary evaporator. Then the solution was poured into 400 ml of ether. The sulfonium chloride 2 obtained was filtered, washed thoroughly with ether, and dried in vacuum overnight. The yield was 70 %. 20 g of this material and a slight excess of sodium triflate were suspended in 100 ml of anhydrous acetone and stirred vigorously for 12 hours at room temperature. The unreacted solids Y2.3.1
OH
OH DMSO/HCl Methanol,
Data Loading...
