Browse Prior Art Database

Fabrication of Defect Free Masks

IP.com Disclosure Number: IPCOM000092891D
Original Publication Date: 1967-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Barson, F: AUTHOR

Abstract

Sources of errors in semiconductor device fabrication are the flaws in masks used in the photolithographic process. The flaws in masks become increasingly more harnnful as the density of the semiconductor devices increases. This is because the probability of a random mask defect has a higher probability of coinciding with a device structure.

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Fabrication of Defect Free Masks

Sources of errors in semiconductor device fabrication are the flaws in masks used in the photolithographic process. The flaws in masks become increasingly more harnnful as the density of the semiconductor devices increases. This is because the probability of a random mask defect has a higher probability of coinciding with a device structure.

There are two general types of mask defects which can occur. First, an opaque spot can occur where the mask should be transparent. The opaque spot then masks the photoresist where it should be exposed, resulting in a pinhole when the resist is developed. A second type of mask effect is the converse, that is, a clear spot where the mask pattern should be opaque. This second type of flaw results in the photoresist being exposed and fixed where it should be removed by developing.

It is possible to eliminate both types of flaws initially present and to produce essentially defect-free masks by a reiteration of a double-masking process. The process starts with an opaque pattern on a clear background in a conventional photographic mask as in drawing 1. Both types of defects can exist, such as the opaque spot shown at A and the clear spot shown at B. If this mask is used as the master to reproduce the pattern in a metal film on a glass plate, a double- masking process can be used to eliminate the first type of defect A. This process includes developing the photoresist patterns, recoating the photoresist, aligning a second mask identical to the first except for the random defects present over the first pattern, and exposing and developing the photoresist....