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Browse Prior Art Database

Method of Cleaning Shadow Masks for Corpuscular Ray Lithography

IP.com Disclosure Number: IPCOM000049374D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Bohlen, H: AUTHOR [+4]

Abstract

Being arranged in a vacuum, masks for corpuscular ray lithography cannot be blown clean. Instead, the contamination particles, without being removed from the mask, are either rendered ineffective by being covered with a conductive metal layer or are removed from the mask by a second cleaning technique, using electrostatic measures.

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Method of Cleaning Shadow Masks for Corpuscular Ray Lithography

Being arranged in a vacuum, masks for corpuscular ray lithography cannot be blown clean. Instead, the contamination particles, without being removed from the mask, are either rendered ineffective by being covered with a conductive metal layer or are removed from the mask by a second cleaning technique, using electrostatic measures.

As integrated circuits are being produced with increasing densities, corpuscular rays, in particular electron or ion beams, are used to image very fine structures. In corpuscular ray lithography, the problem of mask contamination requires particular attention because of the very fine structures and the relatively frequent occurrence of small particles, on the one hand, and the step by step exposure of the semiconductor surface, on the other.

Fig. 1 shows contaminating dust particles 7 and 8, which are opaque to radiation, in the areas of mask 2. Fig. 1 shows a corpuscular ray 1 for scanning the mask. a shadow mask 2, a gold layer 3 arranged thereon, and a silicon wafer 4 with structures 6 that is covered with a photoresist layer 5. Particles 7, which are charged by being bombarded with electrically charged corpuscular rays 1, lead to undesirable beam deflections, as shown in Fig. 1. The broken line in Fig. 1 marks the beam path without beam deflection.

According to the first cleaning technique, the detrimental effect of the electrically charged dust particles 7 is eliminated by vapor depositing a thin gold/palladium layer 9 (Fig. 2) or a similar heavy-metal la...