Browse Prior Art Database

Control of Photoresist Edge Slope

IP.com Disclosure Number: IPCOM000035852D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Wuestenhagen, J: AUTHOR

Abstract

A method is shown for controlling the edge slope of semiconductor contact holes so that a uniform resistance of the metalization is achieved.

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Control of Photoresist Edge Slope

A method is shown for controlling the edge slope of semiconductor contact holes so that a uniform resistance of the metalization is achieved.

A blanket layer of conductive material is evaporated over the surface of a semiconductor after contact hole personalization and etching. Referring to Fig. 1, if the edge slope of a contact hole is vertical, a high resistance contact will result after metalization. Con versely, if the contact hole has a uniformly sloped sidewall profile, the metalization is uniform and results in a low resistance contact.

A new method for controlling contact hole edge slope is dependent upon the development of a photoresist (PR) pattern with sloped sidewalls. When a PR pattern with sloped resist edges is used with a vertical etch that also attacks the photoresist, the PR slope is projected into the underlying material to control the sidewall slope of the contact holes being formed in the underlying material by the etch process.

The sloped resist edge is generated by a double exposure process. By attaching a variable aperture lens to an exposure tool, control over the amount of light used for exposing photoresist is realized. The first exposure, used to define the contact holes, is made with the aperture wide open to maximize the amount of light. The light resolution under these conditions is sharp as shown in Fig. 2a. A second blanket exposure is made with the aperture closed so far that the resolution degra...