US5129982A
Expired / Lapsed
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Selective electrochemical etching
Assignee: Motors Liquidation Co
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Filing: 1991-03-15
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Granted: 1992-07-14
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Expires: 2011-03-15
Abstract
Abstract A method of selectively etching a body of a semiconductor material, such as single crystalline silicon, having regions of n-type and p-type conductivity to remove at least a portion of the n-type region. The body is placed in an etching solution of an etchant having a high pH value and a positive voltage is applied between the body and the etchant. This forms passivating layers on the surfaces of the two regions with the passivating layer on the n-type region being different from that on the p-type region. The voltage is then removed and the body is etched for a period long enough to remove all of the passivating layer from the n-type region and at least a portion of the n-type region, but is not long enough to remove all of the passivating layer from the p-type region. This is allowed by the difference between the passivating layers on the two regions. The steps of forming the passivating layers and etching them is repeated until a desired amount of the n-type region is removed.
Inventors
- 👤 Su-Chee S. Wang
- 👤 Vincent M. McNeil
- 👤 Martin A. Schmidt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 18:43
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/60; H10P50/61; H10P50/613; Y; Y10; Y10S; Y10S438/00; Y10S438/914; Y10S438/924
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
130 words
A method of selectively etching from a body of a semiconductor material having regions of opposite conductivity type at least a portion of the region of one conductivity type comprising the steps of: forming on the surfaces of the regions passivating layers with the passivating layer on the region of one conductivity type being different from that of the passivating layer on the region of the other conductivity type; and etching the body in a chemical etchant for a period of time long enough to etch away all of the passivating layer on the region of the one conductivity type and a portion of the region of the one conductivity type, but not long enough to remove all of the passivating layer from the region of the other conductivity type.
Claim 2
Independent Claim
130 words
A method of selectively etching from a body of a semiconductor material having regions of opposite conductivity type at least a portion of the region of one conductivity type comprising the steps of: forming on the surfaces of the regions passivating layers with the passivating layer on the region of one conductivity type being different from that of the passivating layer on the region of the other conductivity type; and etching the body in a chemical etchant for a period of time long enough to etch away all of the passivating layer on the region of the one conductivity type and a portion of the region of the one conductivity type, but not long enough to remove all of the passivating layer from the region of the other conductivity type.
Claim 3
Dependent Claim
43 words
The method of claim 1 wherein the steps of forming the passivating layers on the regions and etching the passivating layer from the region of one conductivity type are repeated until a desired amount of the region of one conductivity type is removed.
Claim 4
Dependent Claim
20 words
The method of claim 2 in which the one conductivity type is n-type and the other conductivity type is p-type.
Claim 5
Dependent Claim
22 words
The method of claim 3 in which the forming and etching steps are repeated until all of the n-type region is removed.
Claim 6
Dependent Claim
14 words
The method of claim 3 in which the body is of single crystalline silicon
Claim 7
Dependent Claim
35 words
The method of claim 1 in which the passivating layers are formed by placing the body in an etchant having a high pH value and applying a positive voltage between the body and the etchant.
Claim 8
Dependent Claim
33 words
The method of claim 6 in which the etching step is carried out by removing the positive voltage from between the body and the etchant and exposing the passivating layers to the etchant.
Claim 9
Dependent Claim
38 words
The method of claim 7 in which the voltage is applied by immersing an electrode in the etchant spaced from the body and connecting the electrode and the body across a voltage source to achieve the desired voltage.
Claim 10
Dependent Claim
43 words
The method of claim 8 wherein the steps of forming the passivating layer on the regions and etching the passivating layer from the region of one conductivity type are repeated until a desired amount of the region of one conductivity type is removed.
Claim 11
Dependent Claim
25 words
The method of claim 9 in which the forming and etching steps are repeated until all of the region of one conductivity type is removed.
Claim 12
Dependent Claim
20 words
The method of claim 9 in which the one conductivity type is n-type and the other conductivity type is p-type.
Claim 13
Dependent Claim
14 words
The method of claim 11 in which the body is of single crystalline silicon.
Claim 14
Dependent Claim
27 words
The method of claim 12 in which the etchant is selected from the group consisting of KOH, NaOH, LiOH, CsOH, NH 4 OH, ethylenediamine pyrocatechol, and hydrazine.
Claim 15
Dependent Claim
29 words
The method of claim 13 in which the etchant has a concentration of 5% to 95% and a temperature in the range of about 10° C. to 120° C.
Claim 16
Dependent Claim
18 words
The method of claim 14 in which the etchant is a 20% solution of KOH at 60° C.
Claim 17
Independent Claim
163 words
A method of selectively etching from a body of a semiconductor material having regions of opposite conductivity type at least a portion of the region of one conductivity type comprising the steps of: immersing the body in an etchant of high pH value which will etch the semiconductor material and an oxide of the semiconductor material; applying a voltage between the body and the etchant of the polarity suitable to form an oxide passivating layer on the surface of the regions with the passivating layer on the region of one conductivity type being different from the passivating layer on the region of the other conductivity type; and then etching away the passivating layers for a long enough period of time to remove all of the passivating layer from the region of one conductivity type and a portion of the region of the one conductivity type but which does not remove all of the passivating layer from the region of the other conductivity type.
Claim 18
Independent Claim
163 words
A method of selectively etching from a body of a semiconductor material having regions of opposite conductivity type at least a portion of the region of one conductivity type comprising the steps of: immersing the body in an etchant of high pH value which will etch the semiconductor material and an oxide of the semiconductor material; applying a voltage between the body and the etchant of the polarity suitable to form an oxide passivating layer on the surface of the regions with the passivating layer on the region of one conductivity type being different from the passivating layer on the region of the other conductivity type; and then etching away the passivating layers for a long enough period of time to remove all of the passivating layer from the region of one conductivity type and a portion of the region of the one conductivity type but which does not remove all of the passivating layer from the region of the other conductivity type.
Claim 19
Dependent Claim
20 words
The method of claim 16 in which the one conductivity type is n-type and the opposite conductivity type is p-type.
Claim 20
Dependent Claim
18 words
The method of claim 17 in which a positive voltage is applied between the body and the etchant.
Claim 21
Dependent Claim
38 words
The method of claim 18 in which the voltage is applied by immersing an electrode in the etchant spaced from the body and connecting the body and electrode across a source of current to achieve the desired voltage.
Claim 22
Dependent Claim
22 words
The method of claim 18 in which the etching is carried out by removing the voltage between the body and the etchant.
Claim 23
Dependent Claim
40 words
The method of claim 20 in which the steps of forming the passivating layers and etching away the passivating layers and the region of n-type conductivity is repeated until a desired amount of the region of n-type conductivity is removed.
Claim 24
Dependent Claim
14 words
The method of claim 21 in which the body is of single crystalline silicon.
Claim 25
Dependent Claim
27 words
The method of claim 22 in which the etchant is selected from the group consisting of KOH, NaOH, LiOH, CsOH, NH 4 OH, ethylenediamine pyrocatechol, and hydrazine.
Claim 26
Dependent Claim
29 words
The method of claim 23 in which the etchant has a concentration of 5% to 95% and a temperature in the range of about 10° C. to 120° C.
Claim 27
Dependent Claim
18 words
The method of claim 24 in which the etchant is a 20% solution of KOH at 60° C.
References Cited (Backward Citations)
No citation records indexed.
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-07-14 | 1996-01-13 | 1996-07-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-07-14 | 2000-01-13 | 2000-07-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-07-14 | 2004-01-13 | 2004-07-14 | $7700.00 | Window Closed / Lapsed |