# US 10,319,599 B2 · Methods of planarizing SiC surfaces

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- Number: US 10,319,599 B2
- Document ID: US10319599B2
- Status: Granted
- Kind: B2
- Application number: 15/609,438
- Filed: 2017-05-31
- Published: 2018-12-06
- Granted: 2019-06-11
- Earliest claimed: 2017-05-31
- Assignees: Infineon Technologies AG
- Applicants: Infineon Technologies AG
- Inventors: Hans-Joachim Schulze; Helmut Oefner; Roland Rupp
- Web page: https://patentgrep.com/patent/US10319599B2

## CPC

- H10P 50/242: {of Group IV materials}
- B05D 3/044: {Pretreatment}
- C30B 25/186: {being specially pre-treated by, e.g. chemical or physical means}
- C30B 29/36: Carbides
- C30B 31/22: by ion-implantation
- C30B 33/04: using electric or magnetic fields or particle radiation
- C30B 33/10: in solutions or melts
- C30B 33/12: in gas atmosphere or plasma
- H10D 62/83: being Group IV materials, e.g. B-doped Si or undoped Ge
- H10P 14/2926: {Crystal orientations}
- H10P 14/36: {characterised by treatments done before the formation of the materials}
- H10P 30/20: into semiconductor materials, e.g. for doping
- H10P 30/202: {characterised by the semiconductor materials}
- H10P 30/204: {into Group IV semiconductors}
- H10P 30/208: {of electrically inactive species}
- H10P 30/21: {of electrically active species}
- H10P 30/212: {Through-implantation}
- H10P 30/22: using masks
- H10P 30/222: {characterised by the angle between the ion beam and the crystal planes or the main crystal surface (characterised by the angle between the ion beam and the mask H10P30/221)}
- H10P 50/00: Etching of wafers, substrates or parts of devices
- H10P 50/642: {Chemical etching}
- H10P 70/277: {the processing being a planarisation of conductive layers}
- H10P 72/0422: {for wet etching}
- H10P 95/04: {Planarisation of conductive or resistive materials}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- B05D: PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL (conveying articles or workpieces through baths of liquid B65G, e.g. B65G49/02)
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A method of planarizing a roughened surface of a SiC substrate includes: forming a sacrificial material on the roughened surface of the SiC substrate, the sacrificial material having a density between 35% and 120% of the density of the SiC substrate; implanting ions through the sacrificial material and into the roughened surface of the SiC substrate to form an amorphous region in the SiC substrate; and removing the sacrificial material and the amorphous region of the SiC substrate by wet etching.

## Claims

### Claim 1

A method of planarizing a roughened surface of a SiC substrate, the method comprising:
forming a sacrificial material on the roughened surface of the SiC substrate, the sacrificial material having a density between 35% and 120% of the density of the SiC substrate;
implanting ions through the sacrificial material and into the roughened surface of the SiC substrate to form an amorphous region in the SiC substrate; and
removing the sacrificial material and the amorphous region of the SiC substrate by wet etching.

### Claim 2 (depends on 1)

The method of claim 1, wherein the surface of the SiC substrate has remaining roughness after the sacrificial material and the amorphous region of the SiC substrate are removed by wet etching, the method further comprising:
forming an additional sacrificial material on the surface of the SiC substrate with the remaining roughness, the additional sacrificial material having a density between 35% and 120% of the density of the SiC substrate;
implanting ions through the additional sacrificial material and into the surface of the SiC substrate with the remaining roughness to form an additional amorphous region in the SiC substrate; and
removing the additional sacrificial material and the additional amorphous region of the SiC substrate by wet etching.

### Claim 3 (depends on 1)

The method of claim 1, wherein implanting ions through the sacrificial material and into the roughened surface of the SiC substrate to form the amorphous region comprises:
generating an ion beam directed towards the sacrificial material; and
tilting the ion beam at an angle between 1 degree and 10 degrees with respect to a direction perpendicular to the SiC substrate.

### Claim 4 (depends on 1)

The method of claim 1, wherein the sacrificial material comprises at least one of a polymer, an anti-reflective coating, a photoresist, spin-on-glass and a high-density-plasma chemical vapour deposited (HDP-CVD) oxide.

### Claim 5 (depends on 1)

The method of claim 1, further comprising:
planarizing the sacrificial material before implanting the ions.

### Claim 6 (depends on 1)

The method of claim 1, wherein the ions are electrically active in the SiC substrate.

### Claim 7 (depends on 6)

The method of claim 6, wherein some of the ions remain in the SiC substrate after removal of the amorphous region to form an electrically conductive region at a planarized surface of the SiC substrate formed by removal of the amorphous region.

### Claim 8 (depends on 1)

The method of claim 1, wherein the ions are electrically inactive in the SiC substrate.

### Claim 9 (depends on 1)

The method of claim 1, wherein the ions are selected from the group consisting of aluminum, argon, arsenic, nitrogen, oxygen, phosphorous, boron, silicon, carbon and germanium.

### Claim 10 (depends on 1)

The method of claim 1, wherein the roughened surface of the SiC substrate has a maximum peak-to-valley distance, and wherein the ions are implanted at an energy level selected so that the amorphous region extends deeper in the SiC substrate than the maximum peak-to-valley distance.

### Claim 11 (depends on 1)

The method of claim 1, wherein removing the amorphous region of the SiC substrate by wet etching comprises etching the SiC substrate in a solution of hydrofluoric acid, nitric acid, tetramethylammonium hydroxide or potassium hydroxide.

### Claim 12 (depends on 1)

The method of claim 1, further comprising:
dry etching the roughened surface of the SiC substrate before forming the sacrificial material on the roughened surface.

### Claim 13 (depends on 1)

The method of claim 1, further comprising:
dry etching the surface of the SiC substrate after removing the sacrificial material and the amorphous region of the SiC substrate by wet etching.

### Claim 14 (depends on 1)

The method of claim 1, further comprising:
implanting ions directly into the roughened surface of the SiC substrate to form an additional amorphous region in the SiC substrate before forming the sacrificial material on the roughened surface; and
removing the additional amorphous region by wet etching before forming the sacrificial material on the roughened surface.

### Claim 15 (depends on 1)

The method of claim 1, further comprising:
implanting ions directly into the surface of the SiC substrate to form an additional amorphous region in the SiC substrate after removing the sacrificial material and the amorphous region of the SiC substrate by wet etching; and
removing the additional amorphous region of the SiC substrate by wet etching.

### Claim 16 (depends on 1)

The method of claim 1, further comprising:
partly planarizing the roughened surface of the SiC substrate before forming the sacrificial material on the roughened surface.

### Claim 17 (depends on 16)

The method of claim 16, wherein the roughened surface of the SiC substrate has an average peak-to-valley distance in a range between 5 microns and 15 microns before being partly planarized, and wherein the roughened surface of the SiC substrate has an average peak-to-valley distance in a range between 1 micron and 5 microns or between 0.3 micron and 1.5 microns after being partly planarized and before forming the sacrificial material on the roughened surface.

### Claim 18 (depends on 1)

The method of claim 1, wherein the sacrificial material and the amorphous region of the SiC are removed by different etching solutions.

### Claim 19 (depends on 1)

The method of claim 1, further comprising:
splitting a SiC wafer to form the SiC substrate, wherein the roughened surface of the SiC substrate results from the splitting.

### Claim 20 (depends on 1)

The method of claim 1, further comprising:
thinning a SiC wafer to form the SiC substrate, wherein the roughened surface of the SiC substrate results from the thinning.

### Claim 21 (depends on 1)

The method of claim 1, further comprising:
sawing a SiC boule to form the SiC substrate, wherein the roughened surface of the SiC substrate results from the sawing.