Polymethyl methacrylate prepared under special circumstances exhibits a substantial increase in refractive index after irradiation with uv light. The essential step in the preparation is peroxidation of the monomer prior to polymerization. This increase in refractive index results from a photoinduced polymerization of unreacted monomer (1-2%) within the film which produces an increase in density (and hence refractive index) in the irradiated region. It is believed that peroxides, both polymeric and monomeric, act as photoinitiators. Sensitivity depends on the concentration of photoinitiator, but the absolute value of Deltan depends on the amount of unreacte monomer.

Poly(olefin sulfones) have been shown to represent a new class of positive electron beam resists exhibiting sensitivities in the region of 1–3×10−6 coulombs cm−2. Processing variables have been evaluated and exposure characteristics determined. These materials can be used in two development modes, (i) as a conventional solvent‐developed system and (ii) as a system which self develops during e‐beam irradiation by depolymerization followed by vaporization. Limitations of this “vapor development” process are discussed.

A positive electron resist has been developed which appears to operate on a different mechanism from conventional positive electron resists. Resists in the latter category such as PBS or PMMA achieve differential solubility primarily as a result of scission of the main chain. In the case of the new resist, differential solubility appears to be achieved by the removal of a polymeric dissolution inhibitor. The resist is a composite system consisting of a novolac resin similar to that used in most positive photoresists in solid solution with poly(2-methyl-l-pentene sulfone) which functions as a dissolution inhibitor of the novolac resin in aqueous base. The process operates by spontaneous depolymerization of the polymeric dissolution inhibitor, a process which is initiated by electron irradiation. The sensitivity of this resist (called NPR) is 3 #C cm -2 at 20 kV and the contrast is 1.0. Submicron features have been delineated in 1.0 #m resist films. The resist withstands A1, poly-Si, SIO2, doped SiO~, and SixNu plasma etching environments and has been used as a plasma etch mask to transfer submicron features into these film substrates.

synopsisAll the poly(o1efin sulfones) examined degraded rapidly under electron irradiation.The dose required to effect a molecular weight distribution completely separated from the original distribution as required for fractional solution development was similar for all polymers, viz., 1-2 X 10-6 coulomb/cm2. This indicates that they all have similar values for G(scission). The film thickness of the exposed area decreased at a rate dependent on olefin structure and temperature. This process, termed vapor development, has been attributed to concurrent chain scission and depolymerization. Factors determining the rate of depropagation are discussed.

No abstract