# US 7,407,868 B2 · Chemical thinning of silicon body of an SOI substrate

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- Number: US 7,407,868 B2
- Document ID: US7407868B2
- Status: Granted
- Kind: B2
- Application number: 11/073,324
- Filed: 2005-03-04
- Published: 2005-08-18
- Granted: 2008-08-05
- Earliest claimed: 2003-06-17
- Assignees: Intel Corporation
- Inventors: Justin K. Brask; Mohamed A. Shaheen; Ruitao Zhang
- Web page: https://patentgrep.com/patent/US7407868B2

## CPC

- H10P 90/1922: {using silicon etch back techniques, e.g. BESOI or ELTRAN}
- H10P 50/644: {Anisotropic liquid etching (H10P50/61 takes precedence)}
- H10W 10/181: {Semiconductor-on-insulator [SOI] isolation regions, e.g. buried oxide regions of SOI wafers}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

The present invention discloses a method including: providing a silicon wafer; forming a buried oxide (BOX) in the silicon wafer below a silicon body; and reducing a thickness of the silicon body by chemical thinning.

## Claims

### Claim 1

A method comprising:
providing a silicon wafer;
forming a buried oxide (BOX) in said silicon wafer below a silicon body; and
reducing a thickness of said silicon body by chemical thinning in an alkaline solution with an additive, said alkaline solution comprising tetramethyl ammonium hydroxide (TMAH), said additive comprising trimethylamine.

### Claim 2 (depends on 1)

The method of claim 1 wherein said buried oxide (BOX) comprises a thickness of 30 nanometers or less.

### Claim 3 (depends on 1)

The method of claim 1 wherein said silicon body comprises a thickness of 40 nanometers or less before chemical thinning.

### Claim 4 (depends on 1)

The method of claim 1 wherein said silicon body comprises a thickness of 10 nanometers or less after chemical thinning.

### Claim 5 (depends on 1)

The method of claim 1 wherein said tetramethyl ammonium hydroxide (TMAH) comprises 25 weight % in water.

### Claim 6 (depends on 1)

The method of claim 1 wherein said chemical thinning is done at 25 degrees Centigrade.

### Claim 7

A method comprising:
providing a seed wafer;
forming an oxide over said seed wafer;
forming a release interface in said seed wafer below said oxide;
bonding said oxide to a handle wafer to form a buried oxide (BOX), said BOX being embedded between said seed wafer and said handle wafer;
removing a portion of said seed wafer that is disposed below said release interface, leaving behind a silicon body attached to said buried oxide; and
chemically thinning said silicon body in an alkaline solution with an additive, said alkaline solution comprising tetramethyl ammonium hydroxide (TMAH), said additive comprising trimethylamine.

### Claim 8 (depends on 7)

The method of claim 7 wherein said buried oxide (BOX) comprises a thickness of 30 nanometers or less.

### Claim 9 (depends on 7)

The method of claim 7 wherein said silicon body comprises a thickness of 40 nanometers before chemical thinning.

### Claim 10 (depends on 7)

The method of claim 7 wherein said silicon body comprises a thickness of 10 nanometers after chemical thinning.

### Claim 11 (depends on 7)

The method of claim 7 wherein said tetramethyl ammonium hydroxide (TMAH) comprises 25 weight % in water.

### Claim 12 (depends on 7)

The method of claim 7 wherein said chemical thinning is done at 25 degrees Centigrade.