Synthesis and Properties of Bisphenol B Type Novolac Resin:

<p>As we proceeded with the development of a Novolac resin with flexibility and high lithography performance, we focused on adopting a linear polymer structure with few branched structures similar to a dry film resist. In our attempt to develop a flexible Novolac resin for resists, we found that BisC/Glu Novolac resins consisting of bisphenol C (BisC) and glutaraldehyde (Glu), which contain a bulky isopropylidene group in the molecular chain skeleton as a phenolic (PhOH) component, exhibited the highest flexibility and high drawing ability of 4 μm or less that we have investigated. In this study, BisB/Glu and BisB/Form Novolac resins using bisphenol B (BisB, 2,2-Bis(4-hydroxyphenyl)butane) with methylpropylidene group, effect on flexibility expression by alkyl side chain elongation in addition to bulkiness, were newly synthesized and their properties were investigated. The M_w of BisB/Glu and BisB/Form Novolac resins was about 3000－3300 and 1200－1900, respectively. The dissolving rate for alkaline aq. solution (DR) tended to decrease with increasing molar ratio of Glu and/or Form as a crosslinking agent. This is quite different from the correlation between M_w and DR observed in general Novolac resins. Among the obtained Novolac resins, a Novolac resin satisfying the condition DR ≦ 800 Å/sec was chosen, applied to a silicon wafer to obtain a resin film thickness of 1.5μm, and a resist pattern was prepared to evaluate drawing performance. It was confirmed from the bending test that BisB/Glu and BisB/Form Novolac resins showed high flexibility, especially BisB/Glu Novolac resin showed very high flexibility similar to BisC/Glu Novolac resin. Both Novolac resins exhibited high drawing ability (Patterning: 3 μm or less, residual membrane thickness: 90% or more), slightly exceeding the drawing ability of BisC/Glu Novolac resin.</p>