Pre-metal deposition cleaning for bipolar semiconductors
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United States of America Patent
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Jun 21, 1988
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N/A
app pub date -
Jan 13, 1987
filing date -
Jan 13, 1987
priority date (Note) -
Expired
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Abstract
A pre-metal deposition cleaning process for bipolar semiconductors includes a two step boron glass etching procedure: a chemical etchant consisting of DI, H.sub.2 SO.sub.4, HNO.sub.3 and HCl (500:65:325:163) heated to 80 deg. C. followed by a 10:1 (DI:HF) dip. The semiconductor wafer is then annealed in forming gas. Then the boron glass etching procedure is repeated. The initial etch removes any B-Si-O glass present at base contacts. The anneal removes any fluorine clustered under the boron skin, and the final etch removes any retained B-Si-O-F phase from the anneal step. The cleaning procedure produces bipolar semiconductors with low V.sub.be. The procedure can also be used for rework of high V.sub.be wafers without the anneal and the second boron glass etch steps.
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