Browse Prior Art Database

Method for Making Convex Wafers

IP.com Disclosure Number: IPCOM000051367D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Finkeldie, FJ: AUTHOR [+3]

Abstract

The use of wafers whose front surface is convex is increasing in importance in certain device applications. A method for making wafers with convex front surfaces has three basic elements: (1) The fiducial marking system is selected so that the wafer front and back sides are symmetrical and indistinguishable before laser scribing, as shown in the figure. (2) Device quality surfaces are generated on both sides of the wafers using free polishing techniques. (3) The sense of wafer warpage is measured after polishing, and the convex surface is laser scribed to identify the front side at a convenient and standard location.

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Method for Making Convex Wafers

The use of wafers whose front surface is convex is increasing in importance in certain device applications. A method for making wafers with convex front surfaces has three basic elements: (1) The fiducial marking system is selected so that the wafer front and back sides are symmetrical and indistinguishable before laser scribing, as shown in the figure. (2) Device quality surfaces are generated on both sides of the wafers using free polishing techniques. (3) The sense of wafer warpage is measured after polishing, and the convex surface is laser scribed to identify the front side at a convenient and standard location.

A wafer-shaping process that uses these three process elements is as follows:
(1) Centerless grind a silicon crystal to the appropriate

diameter (82, 100, 125 mm).
(2) Generate symmetrical fiducial markings, such as shown in the

figure.
(3) Slice the crystal into wafers.
(4) Chemically thin the wafers to remove damage.
(5) Free polish wafers using one of the options:

(a) 1 plain and 1 perforated poromeric pad, (b) 2 unperforated

pads, or (c) 2 perforated pads of dissimilar patterns and hole

sizes. A slip drive mechanism is used and the process is

terminated with RODELENE*.
(6) Brush and clean the wafers.
(7) Measure the sense of wafer warpage using a non-contact

technique.
(8) Laser scribe a machine- and man-readable identification

mark on the convex side of the wafers to define the front of

the wafers.
(9) Clean the w...