Claims
- 1. The method comprising
- providing an N.sup.- type silicon wafer containing active device regions of known depth below a surface of said wafer,
- mounting said wafer on an electrically conductive member so as to expose said surface of said wafer, and to cover the entire opposite surface of said wafer,
- contacting said surface of said wafer with a hydrofluoric acid solution of concentration less than about 15%,
- applying a potential difference between said solution and said member making said solution negative with respect to said member, and
- setting the amplitude of said potential difference solely in accordance with the desired depth of the depletion region created thereby so that said depletion region is created below said surface of said wafer having a depth no greater than said depth of said active device regions, whereby etch pits are formed in said surface of said wafer overlying electrically active defects within said active device regions.
- 2. The method defined in claim 1 wherein said concentration is about 5%.
- 3. The method defined in claim 1 wherein a vertical bipolar transistor is formed in said silicon material and said depth of said depletion layer is commensurate with the depth of the collector-base junction of said transistor.
- 4. The method defined in claim 1 wherein said solution contacts only a portion of said surface of said wafer.
Parent Case Info
This is a continuation of application Ser. No. 667,232 filed Mar. 15, 1976, now abandoned.
US Referenced Citations (9)
Foreign Referenced Citations (1)
Number |
Date |
Country |
543098 |
Nov 1973 |
CHX |
Continuations (1)
|
Number |
Date |
Country |
Parent |
667232 |
Mar 1976 |
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