A New Class Of Bilevel And Mono-Level Positive Resist Systems Based On A Chemically Stable Imide Polymer

Abstract

A new resin system, comprising a thermoplastic polymer backbone with chemically stable imide functionality, has been adapted for use in three different positive resist product types. These include an advanced bilayer system, a near, mid and deep UV monolevel resist; and an antireflective coating. The key features of the imide polymer system which are utilized for the new resist products are: 1. Novolac-like solubility in aqueous base. This property allows formulation of resists, including the planarizing layer of a bilevel system, with conventional types of positive resist photoactive compounds and aqueous base developers, unlike the situation with PMMA which is not base soluble. 2. Transparency to wavelengths above 260nm. This permits use of the polymer as the matrix for systems which utilize mid and deep UV exposure, including the planarizing layer for a bilevel system and mid and deep UV monolayer resists. This is in contrast to novolac resin wHch absorbs strongly in the deep UV region. 3. Insolubility in solvents used for conventional positive resists. This property is critical to use of the resin in planarizing layers of bilevel systems, including antirefiective coatings. It eliminates the intermixing problems which represent a major problem in conventional PMMA bilevel systems. 4. High Tg (185°C). This value is about 80°C higher than that of PMMA and allows higher temperature processing without pattern distortion. 5. Chemical stability and plasma resistance. Unlike conventional reactive polyimide resins the subject polymer is chemically unreactive and is stable to temperatures above 300°C. Further, the polymer has significantly greater resistance to plasma than does PMMA.