Study on Synthesis and Lithographic Performance of Deep UV Photoresist

• Main Authors: Fu, Shih-Chi, 傅士奇
• Other Authors: Hsieh, Kuo-Huang
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/94450478885868338275

博士 === 國立臺灣大學 === 化學工程學研究所 === 89 === The thesis is focused on the ArF photoresist which is the key chemicals for the next generation of integrated circuit (IC) manufacture. Polymethacrylate and Cycloolefin copolymers were synthesized for use as single layer photoresists. The effect of composition, the developing processes, and the kinetic reaction of the photoresist on the lithographic performance were investigated. The Deep UV light-source outputs with less energy comparing with the conventional Hg light-source. Therefore, the chemical-amplified (CA) conception is widely adopted to design the Deep UV photoresist which can effectively utilize the illumination energy. A photoacid generator (PAG) in the CA photoresist can generate a strong acid after light stimulation, and this acid can catalyze the deprotection or crosslinking reaction of the photoresist during the post exposure baking (PEB) process. The acrylate resin, for its intrinsic high transmittance in ArF (193 nm) wavelength, was first designed as the ArF photoresist by IBM company. The first part of the thesis was to investigate effect of each component of the commercialized acrylate photoresist, which is the tert-butyl methacrylate (TBMA), isobornyl methacrylate (IBMA), methacrylic acid (MAA) and methyl methacrylate (MMA), on the contrast curve and the lithographic performance of the photoresist. The characteristics of acid-labile tert-butyl group in the photoresist are well understood. But for its low developing tolerance, various kinds of acid-labile group or polymer structure are studied to eliminate the developing problems. In the second part of the thesis, the tert-amyl group was substituted for the tert-butyl group as the acid-labile group in the photoresist. Two kinds of dissolution inhibitor (DI) were also added to investigate the effect of DI on the developing characteristics of the photoresist. The experimental results indicated that the elongation of carbon-chain of the tert-butyl group have little improvement in the developing tolerance, and a addition of 10% DI in the photoresist would have the widest developing tolerance. Because of the swelling phenomenon of the crosslinked polymer, negative-tone photoresist are scarcely used in sub-micron lithography. But negative-tone ArF photoresist still has some advantages in special cases, and was therefore studied in the thesis. The dehydration and the crosslinking reaction of the tertiary alcohol by photoacid was used to design the photoresist. Negative-tone patterns can be resulted from developing the exposed photoresist with isopropyl alcohol. The kinetic study of the dehydration reaction of the photoresist indicated that the dehydration rate was proportional to both concentrations of the acid and the hydroxy group. The lithographic patterns of the photoresist was found to have some connections to the Tg of the photoresist, and a copolymer with 50 % IBMA in composition was found to have best lithographic performance. The low reactive ion etching (RIE) resistance of the acrylate photoresist can be enhanced by the incorporation of alicyclic group in the photoresist, but the best way to enhance the RIE resistance of the photoresist is to substitute the cycloolefin structure for the acrylate structure. Therefore, the negative-tone cycloolefin photoresists were prepared by using free radical polymerization and vinyl polymerization methods in the last part of the thesis. The physical properties, RIE resistance, and the lithographic capabilities of the photoresists were discussed, and the negative-tone cycloolefin photoresists were also found to have higher RIE resistance than the afcrylate photoresist.