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Method for Determining the 110 Directions on (100) Gallium Arsenide Substrates

IP.com Disclosure Number: IPCOM000038638D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 85K

Publishing Venue

IBM

Related People

Arienzo, WA: AUTHOR [+2]

Abstract

A simplified method has been developed for determining azimuthal orientation on GaAs substrates. The development involves a roughening of the surface and then the applying of an etch of a specific composition to form a distinguishing pattern. In the production of gallium arsenide semiconductor wafers it is necessary to determine the azimuthal crystallographic orientation of the wafers. This is because the threshold voltage of the devices is very sensitive to azimuthal orientation. Due to the polarity of the GaAs lattice, [01-] and [011] directions on (100) GaAs substrates are not equivalent in the behavior of chemical etching. When patterned and etched along these two orthogonal directions, the mesas will display an acute bottom along the [01-] direction, but an obtuse bottom along the [011] direction.

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Method for Determining the 110 Directions on (100) Gallium Arsenide Substrates

A simplified method has been developed for determining azimuthal orientation on GaAs substrates. The development involves a roughening of the surface and then the applying of an etch of a specific composition to form a distinguishing pattern. In the production of gallium arsenide semiconductor wafers it is necessary to determine the azimuthal crystallographic orientation of the wafers. This is because the threshold voltage of the devices is very sensitive to azimuthal orientation. Due to the polarity of the GaAs lattice, [01-] and [011] directions on (100) GaAs substrates are not equivalent in the behavior of chemical etching. When patterned and etched along these two orthogonal directions, the mesas will display an acute bottom along the [01-] direction, but an obtuse bottom along the [011] direction. This distinction is significant in epitaxial growth and device fabrication. A simple etching method makes it possible to identify the [011] direction unambiguously. The surface of the (100) GaAs substrate is first roughened by lapping with a grit 600 SiC powder. The surface is then etched in an orientation etch consisting of 1 part CrO3 (5 molar), 2 parts HCl and 1 part water. The etch delineates etch pits preferentially aligning along the [01-] direction (Fig. 1), a microphotograph of the front side. The [011] direction is at a 90OE displacement. The direction of the etch pits on the ba...