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Making Photolithographic Chromium Masks having Various Small Patterns

IP.com Disclosure Number: IPCOM000077005D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Daetwyler, K: AUTHOR [+3]

Abstract

Photolithographic masks, as used in semiconductor manufacture, are very difficult to make if the smallest details to be resolved in the pattern are in the order of 0.5 to 1 mum. When sets of subsequent masks are to be used alignment is the top problem. This method allows the production of a set of multiple masks yielding useful results in semiconductor manufacture.

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Making Photolithographic Chromium Masks having Various Small Patterns

Photolithographic masks, as used in semiconductor manufacture, are very difficult to make if the smallest details to be resolved in the pattern are in the order of 0.5 to 1 mum. When sets of subsequent masks are to be used alignment is the top problem. This method allows the production of a set of multiple masks yielding useful results in semiconductor manufacture.

The masks are made of glass plates bearing a 1000 angstroms layer of chromium. Photoresist is applied and in a step and repeat process exposed with the most critical of the different mask patterns. The mask is developed and etched so the chromium is removed in the desired mask pattern. All other masks of the set are then contact-exposed through this first mask and etched only sufficiently to mark the chromium surface. These marks are then used in a subsequent photoresist and etching step as alignment marks for the individual mask pattern, which again is exposed by the step and repeat process.

Fig. A. shows a secondary mask with the marking of the pattern of the first mask. Fig. B shows the secondary mask after exposure and etching of its individual pattern. Note that the marking pattern does not penetrate the chromium layer.

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