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Browse Prior Art Database

Preferential Chemical Etchant

IP.com Disclosure Number: IPCOM000047193D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Schwuttke, GH: AUTHOR [+2]

Abstract

A chemical system is described which consistently results in reliable preferential etching of (100) silicon crystals. Preferential etching is a simple and fast technique to evaluate the structural perfection of a single crystal. For silicon crystals such techniques are widely used to select dislocation-free crystal sections for further processing and also to delineate process-induced defects in silicon wafers. There are several preferential etches currently available for (100) silicon crystals. Use of these etches, however, usually produces contradictory results. A more reliable preferential etch for (100) silicon crystals is therefore highly desirable. It has been found that a mixture of CrO3 (chromium trioxide) dissolved in water at HF (hydrofluoric acid 48%) produces a superior etch.

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Preferential Chemical Etchant

A chemical system is described which consistently results in reliable preferential etching of (100) silicon crystals. Preferential etching is a simple and fast technique to evaluate the structural perfection of a single crystal. For silicon crystals such techniques are widely used to select dislocation-free crystal sections for further processing and also to delineate process-induced defects in silicon wafers. There are several preferential etches currently available for (100) silicon crystals. Use of these etches, however, usually produces contradictory results. A more reliable preferential etch for (100) silicon crystals is therefore highly desirable. It has been found that a mixture of CrO3 (chromium trioxide) dissolved in water at HF (hydrofluoric acid 48%) produces a superior etch. The optimum performance occurs with a mixture consisting of one part by volume of 1.0 to 2.0 molar CrO3 and one part by volume of 48% HF.

For a lesser concentration of CrO3 vigorous bubble formation occurs during etching resulting in unwanted artifacts in the etched surface.

Increasing the concentration of CrO3 results in no preferential etching. Through use of this etch an excellent correlation is achieved between the X-ray topograph and etch features revealed by the etch. Features such as grown-in dislocations, slip dislocations induced by hot processing, swirl patterns, and stacking faults are all clearly defined.

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