Abstract
We discuss the effect of prebake temperature on the development characteristics of the positive-tone novolak resin/diazonaphthoquinone (i.e., Photoactivecompound=PAC) resists. Relationships between initial film thickness and sensitivity (Eth) of resists with various prebake temperatures were investigated, and multiplex interference and bulk effect were estimated from results of Swing curves of resists. When the prebake temperature is from 80 to 130°C, the sensitivity of resists became lower with rising prebake temperature. Peculiarly, it was observed that the sensitivity of resists degrades remarkably when the prebake temperature is higher than 120°C. On the other hand, the multiplex interference and the bulk effect were independent of prebake temperature. Results of photosensitive parameters (A, B, C) for resists with difference prebake temperatures show that PAC absorption of exposure light (A), resist absorption after exposure (B), and photodegradative rate of PAC (C) were all constant even with differences of prebake temperature. FT-IR and DSC measurements showed no changes in chemical structures of novorlak resin and PAC. The amount of residual solvent in resist film decreased with rising prebake temperature. Peculiarly, the amount of residual solvent at prebake temperatures over 120°C was less than that at prebake temperatures under 120°C. Therefore, we concluded that the sensitivity of the resists becomes lower with rising prebake temperature because the hardness of the resist film increases due to decreases of residual solvent amount because of the rise of prebake temperature.
