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Method for controlling of thermal donor formation in high resistivity CZ silicon
| Details |
Inventors: Binns, Martin J.; Falster, Robert J.; Libbert, Jeffrey L.;
Assignee: MEMC Electronic Materials, Inc. (St. Peters, MO)
Primary Examiner: Brewster; William M.
Assistant Examiner:
Attorney, Agent or Firm: Senniger Powers
The present invention is directed to a single crystal Czochralski-type silicon wafer, and a process for the preparation thereof, which has at least a surface layer of high resistivity, the layer having an interstitial oxygen content which renders it incapable of forming thermal donors in an amount sufficient to affect resistivity upon being subjected to a conventional semiconductor device manufacturing process. The present invention further directed to a silicon on insulator structure derived from such a wafer. |
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DETAILED DESCRIPTION Among the features of the present invention, therefore, is the provision of a single crystal silicon wafer, and a process for the preparation thereof, which has at least a high resistivity surface layer; the provision of such as wafer which, upon being subjected to an oxygen precipitation heat-treatment, has a high resistivity denuded zone and a high density of oxygen precipitates in the bulk for internal gettering; and, the provision of such a wafer which has a low concentration of interstitial oxygen in the surface layer.
Further among the features of the present invention is a silicon on insulator device wherein the supporting layer is derived from such a wafer.
Briefly, therefore, the present invention is directed to a wafer sliced from a single crystal silicon ingot grown in accordance with the Czochralski method.
The wafer comprises a front surface, a back surface, an imaginary central plane approximately equidistant between the front and back surfaces, a front surface layer which comprises a region of the wafer between the front surface and a distance, D.
sub.
1, measured from the front surface and toward the central plane, and a bulk layer which comprises the imaginary central plane but not the front surface layer.
The wafer additionally comprises a non-uniform concentration of crystal lattice vacancies, the concentration of the vacancies in the bulk layer being greater than the concentration of vacancies in the front surface layer, wherein (i) D.
sub.
1 is at least about 5 microns but less than about 30 microns, (ii) the surface layer has a resistivity of greater than about 50 ohm cm, and (iii) upon being subjected to an oxygen precipitation heat-treatment at a temperature in excess of about 700.
degree.
C.
, the surface layer has less than about 1.
times.
10.
sup.
7 cm.
sup.
-3 oxygen precipitates while the bulk layer has more than about 1.
times.
10.
sup.
7 cm.
sup.
-3 oxygen precipitates.
The present invention is further directed to a process for preparing a silicon wafer, the wafer being sliced from a single crystal silicon ingot grown in accordance with the Czochralski method and having a front surface, a back surface, an imaginary central plane approximately equidistant between the front and back surfaces, a front surface layer which has a resistivity of greater than about 50 ohm cm and which comprises a region of the wafer between the front surface and a distance, D
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MEMS 
