Patent US3890215A successfully refreshed from Google Patents.
US3890215A
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Electrochemical thinning of semiconductor devices
Assignee: AT&T Inc
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Filing: 1974-02-08
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Granted: 1975-06-17
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Expires: 1994-02-08
Abstract
Abstract A method for precisely tailoring the thickness of a layer of semiconductor material in a structure comprising regions of varying doping concentrations in order to achieve desired uniform electrical properties. The method involves, generally, electrolytically thinning the layer to remove the semiconductor material until a desired field distribution in the structure is reached. In one embodiment, an FET with an epitaxial layer on a semi-insulating substrate is manufactured by successively oxidizing the epitaxial layer and dissolving the oxide until the depletion region resulting from the applied potential extends into the semi-insulating substrate and oxide growth stops. This results in a uniform pinch-off condition along the layer regardless of the original non-uniformity in the epitaxial layer. In a further embodiment, the epitaxial layer in an IMPATT structure is thinned by successive oxidation and dissolution until the voltage dropped across the semiconductor is equal to the applied potential and again oxide growth stops. This procedure results in a desired uniform breakdown voltage for the wafer.
Inventors
- 👤 James Vincent Dilorenzo
- 👤 William Charles Niehaus
- 👤 Daniel Leon Rode
- 👤 Bertram Schwartz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 13:09
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/63; H10P14/6302; H10P14/6304; H10P14/6306; H10P14/6312; H10D; H10D99/00; H10P50/00; H10P50/60; H10P50/61; H10P50/613; H10P50/617; H10P14/6324; Y; Y10; Y10S; Y10S438/00; Y10S438/977
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
176 words
A METHOD FOR THINNING A LAYER OF SEMICONDUCTOR MATERIAL OF ONE CONDUCTIVITY TYPE WITH A FIRST IMPURITY CONCENTRATION IN A STRUCTURE WHICH INCLUDES ADJACENT THERETO A SEMICONDUCTOR MATERIAL OF THE SAME CONDUCTIVITY TYPE WITH A SECOND IMPURITY CONCENTRATION COMPRISING THE STEPS OF: MAKING THE STRUCTURE THE ANODE IN AN ELECTROLYTIC CELL WHEREIN THE ELECTROLYTE IS CAPABLE OF GROWING AN OXIDE INTO THE SURFACE OF THE LAYER UPON THE APPLICATION OF A POTENTIAL TO SAID CELL; APPLYING A CONSTANT POTENTIAL TO SAID STRUCTURE SO AS TO FORM AN ELECTRIC FIELD DISTRIBUTION IN SAID STRUCTURE TO CREATE A CURRENT THROUGH SAID LAYER SUFFICIENT TO FORM AN OXIDE INTO THE SURFACE OF SAID LAYER; DISSOLVING THE OXIDE FORM BY SAID ELECTROLYTE THEREBY REMOVING A PORTION OF SAID LAYER; AND REPEATING THE OXIDATION AND DISSOLUTION OF THE OXIDE UNTIL THE CURRENT THROUGH SAID LAYER IS INSUFFICIENT TO FORM SAID OXIDE INTO SAID LAYER WHEN SAID POTENTIAL IS APPLIED AS THE RESULT OF A PREDETERMINED ELECTRIC FIELD DISTRIBUTION BEING REACHED UNIFORMLY ALONG THE MAJOR PORTION OF THE SURFACE OF SAID LAYER.
Claim 2
Independent Claim
176 words
A METHOD FOR THINNING A LAYER OF SEMICONDUCTOR MATERIAL OF ONE CONDUCTIVITY TYPE WITH A FIRST IMPURITY CONCENTRATION IN A STRUCTURE WHICH INCLUDES ADJACENT THERETO A SEMICONDUCTOR MATERIAL OF THE SAME CONDUCTIVITY TYPE WITH A SECOND IMPURITY CONCENTRATION COMPRISING THE STEPS OF: MAKING THE STRUCTURE THE ANODE IN AN ELECTROLYTIC CELL WHEREIN THE ELECTROLYTE IS CAPABLE OF GROWING AN OXIDE INTO THE SURFACE OF THE LAYER UPON THE APPLICATION OF A POTENTIAL TO SAID CELL; APPLYING A CONSTANT POTENTIAL TO SAID STRUCTURE SO AS TO FORM AN ELECTRIC FIELD DISTRIBUTION IN SAID STRUCTURE TO CREATE A CURRENT THROUGH SAID LAYER SUFFICIENT TO FORM AN OXIDE INTO THE SURFACE OF SAID LAYER; DISSOLVING THE OXIDE FORM BY SAID ELECTROLYTE THEREBY REMOVING A PORTION OF SAID LAYER; AND REPEATING THE OXIDATION AND DISSOLUTION OF THE OXIDE UNTIL THE CURRENT THROUGH SAID LAYER IS INSUFFICIENT TO FORM SAID OXIDE INTO SAID LAYER WHEN SAID POTENTIAL IS APPLIED AS THE RESULT OF A PREDETERMINED ELECTRIC FIELD DISTRIBUTION BEING REACHED UNIFORMLY ALONG THE MAJOR PORTION OF THE SURFACE OF SAID LAYER.
Claim 3
Dependent Claim
27 words
The method according to claim 1 wherein the semiconductor material is selected from the group consisting of GaAs, GaP, AlGaAs, AlGaP, InGaP, InGaAs, GaAsP, InSb, and InAs.
Claim 4
Dependent Claim
12 words
The method according to claim 1 wherein the semiconductor material is GaAs.
Claim 5
Dependent Claim
18 words
The method according to claim 1 wherein the oxide is grown and dissolved in situ in the electrolyte.
Claim 6
Dependent Claim
28 words
The method according to claim 4 wherein the electrolyte comprises H2O and a source of hydroxyl ions sufficient to the pH of the solution to at least 8.
Claim 7
Dependent Claim
20 words
The method according to claim 1 wherein the ratio of the first to second impurity concentrations is at least 1.2.
Claim 8
Dependent Claim
28 words
The method according to claim 1 wherein the electrolyte is selected from the group consisting of H2O containing added ions for conductivity and an aqueous solution of H2O2.
Claim 9
Independent Claim
195 words
A method for thinning a layer of semiconductor material of one conductivity type with a frist impurity concentration which is disposed over a substrate of semiconductor material of the same conductivity type with a second impurity concentration which is less than said first concentration comprising the steps of: making the structure the anode in an electrolytic cell wherein the electrolyte is capable of growing an oxide into the surface of said layer upon the application of a potential to said cell; applying a constant potential to said structure so as to form a depletion region in said layer to create a current through said layer sufficient to form an oxide into the surface of said layer; dissolving the oxide formed by said electrolyte thereby removing a portion of said layer; and repeating the oxidation and dissolution of the oxide until the current through said layer is insufficient to form said oxide into said layer when said potential is applied as the result of said depletion region extending into said substrate along the major portion of the surface of said substrate resulting in a pinchable condition along the major portion of the surface of said layer.
Claim 10
Independent Claim
195 words
A method for thinning a layer of semiconductor material of one conductivity type with a frist impurity concentration which is disposed over a substrate of semiconductor material of the same conductivity type with a second impurity concentration which is less than said first concentration comprising the steps of: making the structure the anode in an electrolytic cell wherein the electrolyte is capable of growing an oxide into the surface of said layer upon the application of a potential to said cell; applying a constant potential to said structure so as to form a depletion region in said layer to create a current through said layer sufficient to form an oxide into the surface of said layer; dissolving the oxide formed by said electrolyte thereby removing a portion of said layer; and repeating the oxidation and dissolution of the oxide until the current through said layer is insufficient to form said oxide into said layer when said potential is applied as the result of said depletion region extending into said substrate along the major portion of the surface of said substrate resulting in a pinchable condition along the major portion of the surface of said layer.
Claim 11
Dependent Claim
20 words
The method according to claim 8 wherein the ratio of the first to second impurity concentrations is at least 1.2.
Claim 12
Dependent Claim
28 words
The method according to claim 8 wherein the electrolyte is selected from the group consisting of H2O containing added ions for conductivity and an aqueous solution of H2O2.
Claim 13
Independent Claim
223 words
A method for thinning a first outer layer of semiconductor material of one conductivity type with a first impurity concentration in a structure which includes a second intermediate layer of semiconductor material of the same conductivity type with a second impurity concentration disposed over a substrate of semiconductor material of the same conductivity type with a third impurity concentration which is greater than said first and second impurity concentrations comprising the steps of: making the structure the anode in an electrolytic cell wherein the electrolyte is capable of growing an oxide into the surface of said first layer upon the application of a potential to said cell; applying a constant potential to said structure which is approximately equal to a desired breakdown potential for the structure so as to form an electric field distribution in said structure to create a current through said first layer sufficient to form an oxide into the surface of said layer; dissolving the oxide formed by said electrolyte thereby removing a portion of said first layer; and repeating the oxidation and dissolution of the oxide until the current through said first layer is insufficient to form an oxide into said layer when said potential is applied resulting in said desired breakdown potential being reached in the structure uniformly along the major portion of the surface of said layer.
Claim 14
Independent Claim
223 words
A method for thinning a first outer layer of semiconductor material of one conductivity type with a first impurity concentration in a structure which includes a second intermediate layer of semiconductor material of the same conductivity type with a second impurity concentration disposed over a substrate of semiconductor material of the same conductivity type with a third impurity concentration which is greater than said first and second impurity concentrations comprising the steps of: making the structure the anode in an electrolytic cell wherein the electrolyte is capable of growing an oxide into the surface of said first layer upon the application of a potential to said cell; applying a constant potential to said structure which is approximately equal to a desired breakdown potential for the structure so as to form an electric field distribution in said structure to create a current through said first layer sufficient to form an oxide into the surface of said layer; dissolving the oxide formed by said electrolyte thereby removing a portion of said first layer; and repeating the oxidation and dissolution of the oxide until the current through said first layer is insufficient to form an oxide into said layer when said potential is applied resulting in said desired breakdown potential being reached in the structure uniformly along the major portion of the surface of said layer.
Claim 15
Dependent Claim
31 words
The method according to claim 11 wherein said first lAyer is disposed adjacent to said second layer and said first impurity concentration lies between said second and said third impurity concentrations.
Claim 16
Dependent Claim
35 words
The method according to claim 12 wherein the ratio of the first and second impurity concentrations is at least 1.2 and the ratio of the third and second impurity concentrations is also at least 1.2.
Claim 17
Dependent Claim
43 words
The method according to claim 11 wherein the structure further comprises a third layer of semiconductor material disposed between said first and second layers which layer has a fourth impurity concentration which lies between said first impurity concentration and said third impurity concentration.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |