Surface denuding of silicon wafer
AssigneeMotorola, Inc.
InventorPhilip J. Tobin
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Abstract
A process is disclosed for preparing silicon wafers having a high quality, high lifetime surface layer and a bulk region characterized by a low lifetime and by a high density of precipitated oxygen gettering sites. A wafer having a relatively high concentration of interstitial oxygen is heated in a reducing ambient at a sufficiently high temperature and a sufficiently long time to cause a surface layer to be denuded of oxygen related defects and dislocations. The temperature is then ramped down to a lower temperature and the wafer is maintained at this lower temperature for a sufficient time to allow precipitation of oxygen within the bulk of the wafer.
Claims14
A process for preparing a silicon substrate for the fabrication of a device which comprises the steps of:
- providing a silicon substrate having a concentration of oxygen incorporated therein;
- heating said substrate to a first elevated temperature in a reducing ambient;
- lowering the temperature of said substrate to a second elevated temperature lower than said first elevated temperature;
- and
- maintaining said substrate at said second elevated temperature for a time to allow nucleation of oxygen precipitates in the bulk of said substrate.
A process for fabricating a semiconductor device which comprises the steps of:
- providing a silicon wafer of first conductivity type having a concentration of oxygen incorporated therein;
- heating said wafer to a temperature between about 1000.degree. and 1200.degree. C. in a reducing ambient for a sufficient time to form a denuded surface layer on said wafer;
- heating said wafer in an oxidizing ambient to form a protective oxide on the surface thereof;
- reducing the temperature of said wafer to a second temperature between about 600.degree. and 800.degree. C. to nucleate the precipitation of oxygen in the bulk of said wafer;
- and
- forming regions of second conductivity type in said denuded surface layer, said regions having a depth into said wafer less than the thickness of said surface layer.
A process for preparing a silicon substrate for the fabrication of a device which comprises the steps of:
- providing a silicon wafer having a concentration of oxygen greater than about 1.3.times.10.sup.18 cm.sup.-3 incorporated therein;
- heating said wafer to a first elevated temperature;
- annealing said wafer in a reducing ambient at said first elevated temperature for about 1-4 hours;
- cooling said wafer to a second temperature lower than said first elevated temperature;
- maintaining said wafer at said second temperature in an oxidizing ambient to form an oxide layer on said wafer;
- further cooling said wafer to a third temperature lower than said second temperature;
- and maintaining said wafer at said third temperature for a sufficient time for the nucleation of microprecipitates.
Dependencies are inferred from the claim text.