David F. Witman

A simplified silylation process

This paper discusses a simplified ‘‘silylation’’ process, which converts typical diazo‐type photoresists into oxygen plasma etch barriers that are insoluble and thermally stable. Previous workers have reported on a silylation process that incorporates silicon in the resist in the gas phase. This paper reports on the use of a bifunctional silylation agent, which when diffused into the patterned resist using a solvent carrier, crosslinks the novolac resin, incorporating silicon in the matrix. The mechanism and the properties of the resist film after silylation such as thermal stability, reactive ion etch (RIE) resistance, silicon content, and solubility will be discussed.

A simple bilayer lift-off process

Abstract This paper discusses a simplified “lift-off” process, which consists of two layers. This consists of an underlayer of soluble, thermally stable polyimide, and a new process, “silylation”, which converts typical positive photoresists into oxygen RIE barriers. The uses of this new material and process for chip and packaging applications are described in this paper.

Diazopolysiloxanes: unique imageable barrier layers

Abstract This paper describes new types of organosilicon photoresists, sensitive throughout the ultraviolet region from 2000 to 45A. The synthesis is based upon a simple condensation reaction of 3-aminopropyl-substituted polysiloxanes with photosensitive naphthoquinone diazosulfonyl chlorides. These polymers when used in bilayer systems are very sensitive, high contrast negative photoresists with sensitivities of about 10 mJ/cm 2 at 4047A and (γ) of 1.4. Because of the inorganic polysiloxane backbone, they are resistant to oxygen plasmas, with an etch rate ratio of 50:1 (photoresist/diazosiloxane), and they are thermally stable up to 400°C. The synthetic procedure, mechanisms of crosslinking and processing characteristics of these materials are discussed along with data concerning their resolution capabilities and lithographic applications.

Silylation of resist materials using di- and polyfunctional organosilicon compounds

Abstract Different types of polyfunctional organosilicon compounds (chloro-, alkoxy-, acetoxysilanes, linear and cyclic silazanes and silylamines) were studied as silylating agents in the diffusion limited heterogeneous silylation process. It was shown that compounds with reactive silicon nitrogen bonds were most effective at silylating AZ4110 resist. Surprisingly, it was found that the higher the organosilicon compound reactivity, the lower the degree of silylation of the photoresist. One of the most effective silylating agents was found to be bis (dimethylamino)dimethylsilane (BDAMS). The chemistry of silylation of both novolak resins and 1,2,5-naphthoquinone diazo type photoactive compounds (PAC) leading to the formation of crosslinked materials is discussed. The formation of triazine derivatives was also detected. Photoresist images which were UV irradiated at 365 nm after exposure and development were found to be more amenable to silylation than those which had not.