# US 4,391,034 A · Thermally compensated shadow mask

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- Number: US 4,391,034 A
- Document ID: US4391034A
- Status: Granted
- Kind: A
- Application number: 06/218,910
- Filed: 1980-12-22
- Granted: 1983-07-05
- Earliest claimed: 1980-12-22
- Assignees: IBM Corporation
- Inventors: Kenneth P. Stuby
- Web page: https://patentgrep.com/patent/US4391034A

## CPC

- G03F 7/70433: {Layout for increasing efficiency or for compensating imaging errors, e.g. layout of exposure fields for reducing focus errors; Use of mask features for increasing efficiency or for compensating imaging errors}
- C23C 14/042: {using masks}
- G03F 9/00: Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically (G03F7/22 takes precedence; preparation of photographic masks G03F1/00; within photographic printing apparatus for making copies G03B27/00)
- H10P 72/57: {Mask-wafer alignment}
- Y10S 438/945: Special, e.g. metal
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

In vacuum sputter cleaning and plating operations forming a patterned metallic layer on a silicon semiconductor chip, alignment is maintained by anticipating the difference in thermal expansion between the molybdenum mask and the silicon chip and forming the apertures in the molybdenum mask in a radially offset position with respect to the intended cleaning and deposition locations on the semiconductor chip, when the mask and the chip are at room temperature. Then, when the mask and the silicon chip are maintained in a concentric position and are raised to the cleaning and deposition temperature, the differential expansion of the molybdenum mask will bring the apertures therein into perfect alignment with the intended deposition locations on the silicon wafer.

## Claims

### Claim 1

An improved high temperature shadow mask for a large diameter silicon wafer, comprising:
a planar plate having a pattern of apertures misregistered at room temperature but registered at high temperature during a deposition process each of whose respective distances from the centroid of said plate at room temperature is misregistered with respect to the corresponding desired distance from the centroid of said wafer of a corresponding shadow image on the silicon wafer at room temperature, by approximately the product of the difference between said high temperature and said room temperature times said desired distance times the difference between the thermal coefficient of expansion of the plate material and the thermal coefficient of expansion of the silicon wafer;
whereby when the plate and silicon wafer are raised to said high temperature for processing, the differential expansion of the plate material will bring the apertures therein into alignment with the intended deposition locations on the silicon wafer.

### Claim 2

An improved high temperature shadow mask for a large diameter silicon wafer, comprising:
a planar plate having a pattern of apertures misregistered at room temperature but registered at high temperature during a deposition process, each of whose respective distances from the centroid of said plate at room temperature is misregistered with respect to the corresponding desired distance from the centroid of said wafer of a corresponding shadow image on the silicon wafer at room temperature, by approximately the product of the difference between said high temperature and said room temperature times said desired distance times the difference between the thermal coefficient of expansion of the plate material and the thermal coefficient of expansion of the silicon wafer; whereby when the plate and silicon wafer are clamped in a fixture which does not maintain said plate centroid and said wafer centroid mutually coincident at said high temperature and are raised to said high temperature for processing, the differential expansion of the plate material will bring the apertures therein into a minimum total misalignment with the intended deposition locations on the silicon wafer.

### Claim 3

A method for making an improved high temperature shadow mask assembly for a large diameter silicon wafer, comprising the steps of:
forming a planar plate having a pattern of apertures misregistered at room temperature but registered at high temperature during a deposition process, each of those respective distances from the centroid of said plate at room temperature is misregistered with respect to the corresponding desired distance from the centroid of said wafer of a corresponding shadow image on the silicon wafer at room temperature, by approximately the product of the difference between said high temperature and said room temperature times said desired distance times the difference between the thermal coefficient of expansion of the plate material and the thermal coefficient of expansion of the silicon wafer;
clamping said plate and said wafer with their said centroids mutually coincident, in a fixture which does not maintain their said centroids mutually coincident at said high temperature;
raising the temperature of said plate and silicon wafer to said high temperature for processing;
whereby the differential expansion of the plate material will bring the apertures therein into a minimum total misalignment with the intended deposition locations on the silicon wafer.