2017 Volume 38 Issue 4 Pages 173-183
Cresol formaldehyde novolac resins (Cre/Form) having hard properties cannot be applied minutely the positivetype photoresist material onto dry films. Therefore, a new development was needed, so we carried out the synthesis and application of novolac resins having flexibility such as cresols glutaraldehyde novolac resin (Cre/Glu). In this study, the reaction with bisphenol A (BisA) and formaldehyde (Form) were carried to obtain BisA/Form novolac resins. Because of we attempt to obtain photo-resist material having the higher flexibility by introducing of bulky the isopropylidene group into molecular chain. When BisA/Form novolac resins were obtained, 3 kinds of synthesis conditions, those were reflux [R], dehydration [D] and the combination of reflux and dehydration [R]－[D], were considered because of attempt a increase of Mw and a decrease of dissolving rate for alkaline aq. (DR) with ratio of lower decomposition of BisA units. The feature of the molecule structures by the difference synthesis protocols was confirmed with 13C-NMR measurement. The obtained resins having DR value below 1000 Å/sec were chosen. The 5μm thick cast films of the obtained resin were applied onto polyimide films in order to evaluate the flexibility properties of the obtained resins by observation of their bent parts. The flexibility of the BisA/Form novolac resin little exceeded Cre/Glu novolac resin. The lithography performance of the obtained resin coated 1.5μm in thickness onto the silicon wafers was examined. The BisA/Form novolac resins showed almost same lithography performance with Cre/Form novolac resin. Especially, BisA/Form novolac resin obtained from combination reaction, 95℃[R]－110℃[D], could be decompose of BisA unit lower than the resin obtained from 120℃[D], and showed higher drawing performance (The residual membrane thickness: 98%, the resist pattern: below 2.5μm).
