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Making Flat, Thin, and Uniformly Thick Wafers

IP.com Disclosure Number: IPCOM000089488D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Guggenheim, RC: AUTHOR [+2]

Abstract

A method for making thin silicon wafers with parallel and damage-free surfaces is described. Wafers as thin as 2 mils have been made. With this technique, workpieces are provided that can then be treated by preferential etches to generate dimensionally precise arrays of etched-out patterns. Such arrays are used, for instance, to provide multiple orifice nozzles for ink jet printing.

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Making Flat, Thin, and Uniformly Thick Wafers

A method for making thin silicon wafers with parallel and damage-free surfaces is described. Wafers as thin as 2 mils have been made. With this technique, workpieces are provided that can then be treated by preferential etches to generate dimensionally precise arrays of etched-out patterns. Such arrays are used, for instance, to provide multiple orifice nozzles for ink jet printing.

The chemical thinning method utilizes a mixture of concentrated NaOH or KOH at 90-100 Degrees C. Optimum results are obtained when 1 part NaOH (or KOH) is dissolved in 4 parts, by weight, of water. In order to obtain parallel wafer surfaces, the workpiece 1 must be rotated at 35-40 rpm while immersed in the etch solution, as shown in Fig. 1. The workpiece 1 is held in slots 2 of holder 3 and rests on rotating driver 4.

The surface finish of the chemically thinned wafer depends on the nature of the starting material. Highly specular surfaces, with minimal roughness, are obtained if the starting material had been previously polished. The amount of material removed during chemical thinning is readily controlled, as shown in Fig.
2.

The results show that (1) flatness and thickness variation is dependent on the starting material, and that the contour of the starting material is faithfully reproduced, (2) chamfered edges do not degrade, (3) edge-roll is not generated, and (4) fine surface finishes are preserved.

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