US4373989A
Expired / Lapsed
US
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Controlled in situ etch-back
Assignee: Individual
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Filing: 1981-11-30
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Granted: 1983-02-15
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Expires: 2001-11-30
Abstract
Abstract A controlled in situ etch-back technique is disclosed in which an etch melt 17 and a growth melt 18 are first saturated by a source-seed crystal 15 and thereafter etch-back of a substrate 14 takes place by the slightly undersaturated etch melt, followed by LPE growth of a layer by the growth melt, which is slightly supersaturated.
Inventors
- 👤 with respect to an invention of Beggs James M. Administrator of the National Aeronautics and Space Administration
- 👤 Robert J. Mattauch
- 👤 Alan C. Seabaugh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:58
CPC Classifications
C; C30; C30B; C30B19/00; C30B19/12; Y; Y10; Y10S; Y10S438/00; Y10S438/955
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
136 words
A method of etching back the top surface of a substrate with an etch melt, the substrate being one on which a layer of matter is to be grown epitaxially from a growth melt, the steps comprising: saturating the etch melt at a temperature, definable as T es ; saturating the growth melt at a temperature, definable as T gs which is greater than T es ; exposing the substrate to the etch melt at a temperature definable as T e , where T gs >T e >T es for a selected period, T e being a temperature at which the depth of etching vs. time of the substrate by the etch melt, saturated at T es is known; and after said selected period exposing said substrate to said growth melt, to grow a layer thereon.
Claim 2
Independent Claim
136 words
A method of etching back the top surface of a substrate with an etch melt, the substrate being one on which a layer of matter is to be grown epitaxially from a growth melt, the steps comprising: saturating the etch melt at a temperature, definable as T es ; saturating the growth melt at a temperature, definable as T gs which is greater than T es ; exposing the substrate to the etch melt at a temperature definable as T e , where T gs >T e >T es for a selected period, T e being a temperature at which the depth of etching vs. time of the substrate by the etch melt, saturated at T es is known; and after said selected period exposing said substrate to said growth melt, to grow a layer thereon.
Claim 3
Dependent Claim
30 words
A method of etching back the top surface of a substrate as recited in claim 1 wherein T e is greater than T es by more than one degree Celsius.
Claim 4
Dependent Claim
39 words
A method of etching back the top surface of a substrate as recited in claim 1 wherein said etch melt and said growth melt are saturated at the temperatures, T es and T gs respectively, with a source-seed crystal.
Claim 5
Dependent Claim
44 words
A method of etching back the top surface of a substrate as recited in claim 3 wherein said substrate is GaAs, said growth melt is composed of Ga and As, and said etch melt contains matter for etching the surface of a GaAs substrate.
Claim 6
Dependent Claim
41 words
A method of etching back the top surface of a substrate as recited in claim 4 wherein said etch melt and said growth melt are saturated at the temperatures T es and T gs respectively, with a source-seed crystal of GaAs.
Claim 7
Dependent Claim
23 words
A method of etching back the top surface of a substrate as recited in claim 5 where T e -T es >1/4° C.
Claim 8
Dependent Claim
29 words
A method of etching back the top surface of a substrate as recited in claim 6 wherein T e -T es =ΔT being on the order of 7° C.
Claim 9
Dependent Claim
36 words
A method of etching back the top surface of a substrate as recited in claim 7 wherein T gs is on the order of 752° C. and T es is on the order of 745° C.
Claim 10
Dependent Claim
33 words
A method of etching back the top surface of a substrate as recited in claim 8 wherein T e is on the order of one-and-one-half to two degrees Celsius below T gs .
Claim 11
Independent Claim
279 words
A method of etching a substrate prior to growing epitaxially a layer of matter thereon, in a liquid phase epitaxial (LPE) furnace of the type including a boat with a plurality of spaced apart wells, and a slider adapted to slide with respect to said boat to form the bottom of said wells, said slider including recesses, the steps comprising: providing an etch melt and a growth melt in two spaced apart wells in said boat; providing a source-seed crystal and a substrate in two spaced apart recesses in said slider; heating said furnace to a temperature definable as T es with the slider positioned so that said source-seed crystal is in contact with the etch melt; saturating said etch melt with said source-seed crystal at T es ; sliding said slider so that neither said source-seed crystal nor said substrate is in contact with either of said melts; raising said furnace temperature to a temperature T gs where T gs >T es ; sliding said slider so that said source-seed crystal is in contact with said growth melt until said growth melt is saturated; lowering the furnace temperature to a temperature definable at T e where T gs >T e >T es . sliding said slider to position said substrate under said etch melt for a selected period of time, based on a predetermined etch depth vs. time of said melt at T e , after having been saturated at T es , to etch said substrate to a selected depth; and sliding said slider to position said etched substrate under said growth melt which was previously saturated at T gs to grow a layer of matter thereon.
Claim 12
Independent Claim
279 words
A method of etching a substrate prior to growing epitaxially a layer of matter thereon, in a liquid phase epitaxial (LPE) furnace of the type including a boat with a plurality of spaced apart wells, and a slider adapted to slide with respect to said boat to form the bottom of said wells, said slider including recesses, the steps comprising: providing an etch melt and a growth melt in two spaced apart wells in said boat; providing a source-seed crystal and a substrate in two spaced apart recesses in said slider; heating said furnace to a temperature definable as T es with the slider positioned so that said source-seed crystal is in contact with the etch melt; saturating said etch melt with said source-seed crystal at T es ; sliding said slider so that neither said source-seed crystal nor said substrate is in contact with either of said melts; raising said furnace temperature to a temperature T gs where T gs >T es ; sliding said slider so that said source-seed crystal is in contact with said growth melt until said growth melt is saturated; lowering the furnace temperature to a temperature definable at T e where T gs >T e >T es . sliding said slider to position said substrate under said etch melt for a selected period of time, based on a predetermined etch depth vs. time of said melt at T e , after having been saturated at T es , to etch said substrate to a selected depth; and sliding said slider to position said etched substrate under said growth melt which was previously saturated at T gs to grow a layer of matter thereon.
Claim 13
Dependent Claim
26 words
A method of etching a substrate as recited in claim 10 wherein T e is greater than T es by more than one greater degree Celsius.
Claim 14
Dependent Claim
34 words
A method of etching a substrate as recited in claim 10 wherein said substrate, said source-seed crystal and said growth melt are GaAs and said etch melt contains matter for etching a GaAs substrate.
Claim 15
Dependent Claim
18 words
A method of etching a substrate as recited in claim 12 where T e -T es =ΔT>1/4° C.
Claim 16
Dependent Claim
25 words
A method of etching a substrate as recited in claim 13 wherein ΔT=T gs -T es , ΔT being on the order of 7° C.
Claim 17
Dependent Claim
31 words
A method of etching a substrate as recited in claim 14 where T gs is on the order of 752° C. and T es is on the order of 745° C.
Claim 18
Dependent Claim
28 words
A method of etching a substrate as recited in claim 15 where T e is on the order of one-and-one-half to two degrees Celsius below T gs .
Claim 19
Independent Claim
290 words
A method of etching a substrate prior to growing epitaxially a layer of matter thereon, in a liquid phase epitaxial (LPE) furnace of the type including a boat with a plurality of spaced apart wells, and a slider adapted to slide with respect to said boat to form the bottom of said wells, said slider including recesses, the steps comprising: providing an etch melt and a growth melt in two spaced apart wells in said boat; providing a source-seed crystal and a substrate in two spaced apart recesses in said slider; heating said furnace to a temperature definable as T es with the slider positioned so that said source-seed crystal is in contact with the etch melt; saturating said etch melt with said source-seed crystal at T es ; sliding said slider so that neither said source-seed crystal nor said substrate is in contact with either of said melts; raising said furnace temperature to a temperature T gs where T gs >T es ; sliding said slider so that said source-seed crystal is in contact with said growth melt until said growth melt is saturated; at a furnace temperature of T e , where T gs ≧T e sliding said slider to position said substrate under said etch melt for a selected period of time, based in a predetermined etch depth vs. time of said etch melt at T e , after having been saturated at T es , to etch said substrate to a selected depth; and at a temperature T x , where T gs >T x sliding said slider to position said etched substrate under said growth melt which was previously saturated at T gs to grow a layer of matter thereon, from the supersaturated growth melt.
Claim 20
Independent Claim
290 words
A method of etching a substrate prior to growing epitaxially a layer of matter thereon, in a liquid phase epitaxial (LPE) furnace of the type including a boat with a plurality of spaced apart wells, and a slider adapted to slide with respect to said boat to form the bottom of said wells, said slider including recesses, the steps comprising: providing an etch melt and a growth melt in two spaced apart wells in said boat; providing a source-seed crystal and a substrate in two spaced apart recesses in said slider; heating said furnace to a temperature definable as T es with the slider positioned so that said source-seed crystal is in contact with the etch melt; saturating said etch melt with said source-seed crystal at T es ; sliding said slider so that neither said source-seed crystal nor said substrate is in contact with either of said melts; raising said furnace temperature to a temperature T gs where T gs >T es ; sliding said slider so that said source-seed crystal is in contact with said growth melt until said growth melt is saturated; at a furnace temperature of T e , where T gs ≧T e sliding said slider to position said substrate under said etch melt for a selected period of time, based in a predetermined etch depth vs. time of said etch melt at T e , after having been saturated at T es , to etch said substrate to a selected depth; and at a temperature T x , where T gs >T x sliding said slider to position said etched substrate under said growth melt which was previously saturated at T gs to grow a layer of matter thereon, from the supersaturated growth melt.
Claim 21
Dependent Claim
30 words
A method of etching a substrate as recited in claim 17 wherein T e =T gs and T x is less than T e by less than one degree Celsius.
Claim 22
Dependent Claim
38 words
A method of etching a substrate as recited in claim 17 wherein T gs ≧T e and, T e ≧T x , T e >T es and T gs -T x is not more than one degree Celsius.
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) | 1986-02-14 | 1986-08-16 | 1987-02-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-02-14 | 1990-08-16 | 1991-02-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-02-14 | 1994-08-16 | 1995-02-15 | $7700.00 | Window Closed / Lapsed |