# US 5,344,517 A · Method for lift-off of epitaxial layers and applications thereof

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- Number: US 5,344,517 A
- Document ID: US5344517A
- Status: Granted
- Kind: A
- Application number: 08/052,004
- Filed: 1993-04-22
- Granted: 1994-09-06
- Earliest claimed: 1993-04-22
- Assignees: Bandgap Technology Corporation
- Inventors: Virginia Houlding
- Web page: https://patentgrep.com/patent/US5344517A

## CPC

- H10H 20/013: {having light-emitting regions comprising only Group III-V materials}
- C25F 3/12: of semiconducting materials
- Y10T 156/11: Methods of delaminating, per se; i.e. , separating at bonding face
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- C25F: PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention provides for improved methods of fabricating layered materials which are epitaxially grown on an electrically conductive single crystal substrate. The improved methods comprise the step of applying an electrochemical potential between the layered material/substrate and a counter electrode to oxidize and dissolve a thin etch layer positioned between the film and substrate, to thereby free the layered material from the substrate.

## Claims

### Claim 1

A process for selectively freeing an epitaxial film from an electrically conductive single crystal substrate upon which it was grown comprising:
a) placing the film and substrate into an etching solution; and
b) applying an electrochemical potential between the film/substrate and a counter electrode to oxidize and dissolve a thin etch layer positioned between the film and substrate to thereby separate the film and the substrate from each other.

### Claim 2 (depends on 1)

The process of claim 1 in which the epitaxial film is multilayered.

### Claim 3 (depends on 1)

The process of claim 1 in which the epitaxial film is selected from the group consisting of III-V semiconductor material, II-VI semiconductor material and combinations of both.

### Claim 4 (depends on 1)

The process of claim 1 in which the etch layer is AlAs.

### Claim 5 (depends on 4)

The process of claim 4 in which the etch layer is between about 50 .ANG. and about 10,000 .ANG. thick.

### Claim 6 (depends on 1)

The process of claim 1 wherein the film is attached to a rigid second substrate prior to steps a) and b), and the second substrate remains attached after dissolution of the etch layer.

### Claim 7 (depends on 6)

The process of claim 6 wherein the film is attached to a rigid second substrate by attachment means from the group consisting of an adhesive, Van der Waals forces, solder or melt.

### Claim 8 (depends on 1)

The process of claim 1 in which the single crystal substrate is n-doped GaAs.

### Claim 9 (depends on 1)

The process of claim 1 where in step b) the etch layer is oxidized and dissolved in an electrolyte solution containing dissolved fluoride ions.

### Claim 10 (depends on 9)

The process of claim 9 where the electrolyte solution is NaF, KF or NH.sub.4 F.

### Claim 11

A process for selectively freeing an epitaxial film from an electrically conductive single crystal substrate upon which it was grown comprising:
a) attaching a rigid transfer substrate onto the epitaxial film with an adhesive, wherein the transfer substrate and the adhesive are insoluble in an etch solution;
b) placing the transfer substrate, film and substrate into an etching solution; and
c) applying an electrochemical potential between the transfer substrate/film/substrate and a counter electrode to dissolve a thin etch layer positioned between the film and substrate to thereby separate the transfer substrate/film and the substrate from each other.

### Claim 12 (depends on 11)

The process of claim 11 further comprising a step d) after step c) of placing the transfer substrate and film into another solution that dissolves the adhesive to thereby free the transfer substrate from the film.

### Claim 13 (depends on 12)

The process according to claim 12 wherein the transfer substrate and film of step c) is bonded on the film side to a final substrate prior to step d).

### Claim 14 (depends on 13)

The process according to claim 13 wherein the final substrate is selected from the group consisting of glass, silicon wafer, chromium and palladium coated silicon wafer, germanium wafer, III-V material, II-VI material, sapphire, lithium niobate and gadolinium garnet.

### Claim 15 (depends on 11)

The process according to claim 11 wherein the etch solution comprises dissolved fluoride ions.

### Claim 16 (depends on 15)

The process according to claim 15 wherein the transfer substrate is polycarbonate.

### Claim 17 (depends on 12)

The process according to claim 12 wherein the solution used in step d) is acetone.

### Claim 18 (depends on 11)

The process according to claim 11 wherein the etch layer is AlAs.