Wednesday, December 1, 2010

Gallium Arsenide (GaAs) Fabrication

Although there are various approaches that are currently used, high-pressure liquid-encapsulated Czochralski (LEC) growth of gallium arsenide crystals from high purity pyrolytic boron nitride (PBN) crucibles is becoming the primary growth technique over several other methods that have emerged during the last few years.
Since preference is usually for wafers grown in the <100> orientation, much of the success of the above method is achieved as the result of the ability to grow LEC material in the <100> direction, which produces relatively large diameter, round (100) wafers that are thermally stable and have superior semi-insulating properties.
Since the <110> cleavage planes are at a right angle, square chips can be obtained with a diamond scribe and break. This means that by adhering to the <100> growth plane many of the problems associated with cutting and subsequent handling can be alleviated.
The sequence for GaAs wafer preparation is very similar to that of silicon wafer preparation technique. The first step involves mechanically grinding the As-grown boules to a precise diameter and incorporating orientation flats. This is followed by
•                    Wafering using a diamond ID saw
•                    Edge rounding
•                    Lapping
•                    Polishing
•                    Wafer Scrubbing

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