Developer Characteristics of Poly‐(Methyl Methacrylate) Electron Resist

Abstract

We report on the solubility characteristics of poly‐(methyl methacrylate) electron‐resist for developer combinations of methyl isobutyl ketone (MIBK) and isopropyl alcohol (IPA). The solubility rate is determined in terms of the fragmented molecular weight which is a function of original molecular weight and the energy absorbed by the polymer in degrading to a lower molecular weight. An empirical formula for the solubility rate is , where is the fragmented molecular weight, , β, and α are constants characteristic of a given developer. The temperature dependence is characterized by an activation energy, , for a given developer. The solubility kinetics are discussed showing a rate limited process for most developer conditions. From the solubility rate and the characteristic energy absorption in the resist, the development time and contrast are defined and calculated for a variety of exposure parameters including beam energy, resist thickness, developer, developer temperature, and original molecular weight. Compared to the standard developer, 1:3 MIBK:IPA, an improved sensitivity of 10–50 times is obtained using MIBK at the expense of increased development time. For a given contrast level the development time is greatly reduced by increasing the developer temperature. A lower original molecular weight also reduces the required development time.