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Via Sidewall Shaping by Projection Image Degradation

IP.com Disclosure Number: IPCOM000059680D
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Bradley, AR: AUTHOR [+4]

Abstract

In the fabrication of semiconductor integrated circuits having multi- level metallization, it is important to control the sidewall slope of the vias in the insulating layers that provide contact points between metal layers. The disclosed process utilizes a mask pellicle to degrade the projected image and achieve an improved via sidewall slope. A via having too steep a slope or sharp edges can result in step- coverage defects in the overlying metal layer. Conventional methods for controlling the sidewall slope include modifying the chemical constituents of the photoresist used to define the via or altering the etching parameters during via formation. Alternatively, a post-develop heating step may be used to reflow the photoresist and produce a degraded mask image which is transferred to the insulating layer during etching.

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Via Sidewall Shaping by Projection Image Degradation

In the fabrication of semiconductor integrated circuits having multi- level metallization, it is important to control the sidewall slope of the vias in the insulating layers that provide contact points between metal layers. The disclosed process utilizes a mask pellicle to degrade the projected image and achieve an improved via sidewall slope. A via having too steep a slope or sharp edges can result in step- coverage defects in the overlying metal layer. Conventional methods for controlling the sidewall slope include modifying the chemical constituents of the photoresist used to define the via or altering the etching parameters during via formation. Alternatively, a post-develop heating step may be used to reflow the photoresist and produce a degraded mask image which is transferred to the insulating layer during etching. These methods may not be repeatable from wafer to wafer, and the reflow method is not effective for high contrast photoresists. In the present method, a pellicle formed of a polyester film is affixed to the projection mask which is used to expose the photoresist. The scattering characteristics of the polyester film degrades the projected image in a known, repeatable manner. The developed profile in the photoresist has a shallow slope and is transferred to the via profile in the insulating layer during reactive ion etching. The image degradation technique provides a precisely controlled and rep...