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Selective Etching of Small Crystalline Structures

IP.com Disclosure Number: IPCOM000090908D
Original Publication Date: 1969-Aug-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Marinace, JC: AUTHOR [+2]

Abstract

An N-type GaAs wafer with its polished surface in a {100} plane is diffused with Zn, forming a junction at a depth of the order of 10 mu. A film of SiO(2) is put on the polished surface. Narrow slots are etched into this film by a photoresist method in a ›110| direction to form a mask. The wafer is lapped to ~100 mu. Metallic ohmic contacts are applied to the bottom of the wafer and to the slotted regions. A lacquer-type etch resist is electrophoretically deposited over the metallized regions. The SiO(2) is removed by HF acid.

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Selective Etching of Small Crystalline Structures

An N-type GaAs wafer with its polished surface in a {100} plane is diffused with Zn, forming a junction at a depth of the order of 10 mu. A film of SiO(2) is put on the polished surface. Narrow slots are etched into this film by a photoresist method in a >110| direction to form a mask. The wafer is lapped to ~100 mu. Metallic ohmic contacts are applied to the bottom of the wafer and to the slotted regions. A lacquer-type etch resist is electrophoretically deposited over the metallized regions. The SiO(2) is removed by HF acid.

The wafer is then immersed in a GaAs etchant, such as NH(4)OH: H(2)O: H(2)O: : 1: 1: 1:. After a particular time, the etching is stopped. The wafer can then be cleaved in a direction perpendicular to the axes of the slots, and the etched mesas cleave along with the major portion of the wafer.

The mesa profiles (transverse) are distinctly characteristic of the particular >110| direction of the slot axes. There are two such >110| type directions perpendicular to each other. The shape of the mesa is determined by the orientation of the mask slots relative to these crystalline directions as shown in A, B, and C. The preferred structure for an injection laser is shown in B. The junction is located at the narrow portion of the mesa immediately above the substrate. Sample etch patterns are made on the wafer to determine the proper orientation of the crystalline directions so that the mask slo...