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Improved Plasma Composition for Reactive Ion Etching Polymers with Silicon Based Masks

IP.com Disclosure Number: IPCOM000037505D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

McGouey, RP: AUTHOR [+2]

Abstract

This disclosure describes an improved gas composition used in the plasma for reactive ion etching the polymers used in thin film modules. The polymer-mask etch rate ratio is improved, and redeposition of silicon products from the mask is prevented.

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Improved Plasma Composition for Reactive Ion Etching Polymers with Silicon Based Masks

This disclosure describes an improved gas composition used in the plasma for reactive ion etching the polymers used in thin film modules. The polymer- mask etch rate ratio is improved, and redeposition of silicon products from the mask is prevented.

Polyimides, as well as other polymers, are now commonly accepted materials for use as dielectrics separating orthogonal layers of metal circuitry in packaging modules. The state of the art method for producing via holes and line trenches in these polymer layers is subjecting them to an oxidizing ambient by means of an RF glow discharge in oxygen. The patterns for the vias and trenches are fabricated in this plasma by the use of an oxidation resistant mask. The masks used to date have been generally silicon based compounds, viz., silicon nitride, silicon oxide, or a hydroxylated photoresist which has been silylated. This is the Reactive Ion Etching process as it has been practiced.

RIE is a complex process. Because of the velocity of the oxygen atoms impinging upon the material being chemically etched, there is also simple sputtering taking place. In a pure oxygen plasma, silicon by-products are removed from the mask and redeposited into the pattern being etched. This redeposit has accumulated in amounts sufficient to ruin the etched pattern.

We have added small quantities of carbon tetrafluoride to the oxygen plasma. The effect has...