Method of fabricating Group III-V compound semiconductor devices using selective etching

- Watkins Johnson Company
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Claims

2. The method of claim 1 further including the step of formulating said etchant such that said concentration of H.sub.2 O.sub.2 is in the range of approximately 1-2.5 moles/liter when said concentration of citric acid is in the range of approximately 0.2-0.7 moles/liter.

3. The method of claim 2 further including the step of formulating said etchant such that said concentration of H.sub.2 O.sub.2 is in the range of approximately 1-2.5 moles/liter when said concentration of said salt of citric acid is approximately in the range 0.2-0.7 moles/liter.

4. The method of claim 1 further including the step of formulating said etchant such that:

said concentration of said salt of citric acid in said solution is in the range of 0.2-0.7 moles/liter, and
one-half of the sum of said concentrations of said citric acid and said salt of citric acid is greater than 0.3 moles/liter and less than 1.0 moles/liter.

5. The method of claim 1 wherein said first compound region consists of Al.sub.y Ga.sub.1-y As and said second compound region consists of Al.sub.x Ga.sub.1-x As wherein (0.ltoreq.y<0.2) and (0.2<x.ltoreq.1.0).

6. A method of making a semiconductor device comprising the steps of:

fabricating a structure by
(i) growing one or more layers of the type X.sub.a Y.sub.1-a As, where X is an atom selected from the group of IIIA atoms and Y is a different atom selected from the group of IIIA atoms, and where (0<a.ltoreq.1) upon a semiconductor substrate, and
(ii) growing first and second Group III-V compound regions of differing composition upon said one or more layers, said first compound region including GaAs; and subjecting said structure to an etchant comprising a solution of a citrate buffer and H.sub.2 O.sub.2 with a pH in the range of approximately 3 to 6 so that said first region is selectively etched, said citrate buffer including citric acid and a salt of citric acid, wherein the concentration in.Iadd.moles/liter.Iaddend.of hydrogen peroxide in said solution is greater than the concentration.Iadd.in moles/liter.Iaddend.of citric acid in said solution and greater than the concentration.Iadd.in moles/liter.Iaddend.of said salt of citric acid in said solution.

7. The method of claim 6 wherein said second region comprises Al.sub.x Ga.sub.1-x As where (0.2<x.ltoreq.1), said second region being grown upon said one or more layers to a thickness selected in accordance with the value of x.

8. A method of making a field-effect transistor comprising the steps of:

fabricating a structure by
(i) growing one or more active channel layers comprised of Group III-V compounds upon a semiconductor substrate,
(ii) growing a thin etch stop region of Al.sub.x Ga.sub.1-x As upon said active channel layers where (0.2<x.ltoreq.1), and
(iii) growing a cap region including GaAs upon said thin etch stop region; and
subjecting said structure to an etchant comprising a solution of a citrate buffer and H.sub.2 O.sub.2 with a pH in the range of approximately 3 to 6 so that said cap region is selectively etched and said etch stop region prevents etching of said active channel layers, said citrate buffer including citric acid and a salt of citric acid, wherein the concentration.Iadd.in moles/liter.Iaddend.of hydrogen peroxide in said solution is greater than the concentration.Iadd.in moles/liter.Iaddend.of citric acid in said solution and greater than the concentration.Iadd.in moles/liter.Iaddend.of said salt of citric acid in said solution.

9. The method of claim 1 wherein said salt of citric acid comprises potassium citrate.

10. The method of claim 6 wherein said salt of citric acid comprises potassium citrate.

Referenced Cited
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4486536 December 4, 1984 Baker et al.
4835101 May 30, 1989 Kao et al.
4914488 April 3, 1990 Yamane et al.
4935377 June 19, 1990 Strifler et al.
5041393 August 20, 1991 Ahrens et al.
5110765 May 5, 1992 Balakanti et al.
5215885 June 1, 1993 Marrujo et al.
Foreign Patent Documents
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Other references
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Patent History
Patent number: RE36185
Type: Grant
Filed: Dec 5, 1996
Date of Patent: Apr 6, 1999
Assignee: Watkins Johnson Company (Palo Alto, CA)
Inventors: Ronald E. Remba (Sunnyvale, CA), Paul E. Brunemeier (Sunnyvale, CA), Bruce C. Schmukler (Greensboro, NC), Walter A. Strifler (Sunnyvale, CA), Daniel H. Rosenblatt (San Carlos, CA)
Primary Examiner: Jey Tsai
Law Firm: Flehr Hohbach Test Albritton & Herbert LLP
Application Number: 8/751,776
Classifications
Current U.S. Class: Iii-v Compound Semiconductor (438/604); Ga And As Containing Semiconductor (438/606)
International Classification: B44C 122;