# US 6,171,935 B2 · Process for producing an epitaxial layer with laterally varying doping

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- Number: US 6,171,935 B2
- Document ID: US6171935B2
- Status: Granted
- Kind: B2
- Application number: 09/317,694
- Filed: 1999-05-24
- Granted: 2001-01-09
- Earliest claimed: 1998-05-06
- Assignees: Siemens Aktiengesellschaft
- Inventors: Paul Nance; Wolfgang Werner
- Web page: https://patentgrep.com/patent/US6171935B2

## CPC

- H10D 30/66: Vertical DMOS [VDMOS] FETs
- H10D 30/0291: {of vertical DMOS [VDMOS] FETs}
- H10D 62/111: {Multiple RESURF structures, e.g. double RESURF or 3D-RESURF structures}
- H10D 62/127: {of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs}
- H10D 62/156: {Drain regions of DMOS transistors}
- H10P 14/271: {characterised by the preparation of substrate for selective deposition}
- H10P 14/2905: {Silicon, silicon germanium or germanium}
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- H10D 62/393: {Body regions of DMOS transistors or IGBTs (cell layout of DMOS H10D62/127)}
- H10P 50/642: {Chemical etching}
- Y10S 438/969: Simultaneous formation of monocrystalline and polycrystalline regions
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A process for producing an epitaxial layer with laterally varying doping includes the following steps: (a) applying a patterned insulator layer to a semiconductor body; (b) growing a first epitaxial layer on the semiconductor body and the patterned insulator layer so that monocrystalline regions are formed over the semiconductor body and polycrystalline regions are formed over the patterned insulator layer, the angle of inclination (α) of the interface between the monocrystalline regions and the polycrystalline regions depending on the grain size of the polycrystalline regions; (c) removing the polycrystalline regions and the insulator layer, and (d) growing a second epitaxial layer which, together with the monocrystalline regions of the first epitaxial layer, forms the epitaxial layer.

## Claims

### Claim 1

A process for forming over a top surface of a monocrystalline semiconductive body an epitaxial semiconductive layer whose conductivity characteristics vary laterally across the surface comprising the steps of:
forming over the top surface of the monocrystalline semiconductive body a patterned insulating layer;
growing over the top surface a first semiconductive layer that forms monocrystalline regions where it overlies the monocrystalline semiconductive body and polycrystalline regions where it overlies the patterned insulating layer;
removing selectively the polycrystalline regions and the insulating layer; and
growing over the top surface a second semiconductive layer with conductivity characteristics different from that of the first semiconductive layer for forming essentially monocrystalline regions of said different conductivity characteristic between the monocrystalline regions of said first semiconductive layer.

### Claim 2 (depends on 1)

The process of claim 1 in which the different conductivity characteristic is a difference in conductivity type.

### Claim 3 (depends on 1)

The process of claim 1 in which the different conductivity characteristic is a difference in doping concentration.

### Claim 4 (depends on 1)

The process of claim 1 in which the monocrystalline semiconductive body initially includes an epitaxial layer over its top surface.

### Claim 5 (depends on 1)

The process of claim 1 in which after the formation of the patterned insulating layer it is used as a mask for doping the semiconductive body before the growth of the first semiconductive layer.

### Claim 6 (depends on 1)

The process of claim 1 in which the growing of the first semiconductive layer is done under conditions to promote the growth of polycrystalline regions that form interfaces with the monocrystalline regions that are essentially perpendicular to the surface of the semiconductive body.

### Claim 7 (depends on 6)

The process of claim 6 in which factors that control the growth of the polycrystalline region are the size of the grains of the polycrystalline regions.

### Claim 8 (depends on 1)

The process of claim 1 in which the insulating layer is silicon dioxide that acts as an etch stop in the removal of the polycrystalline regions.

### Claim 9 (depends on 1)

The process of claim 1 in which the first layer is grown to form conical monocrystalline regions between the polycrystalline regions.

### Claim 10 (depends on 1)

The process of claim 1 in which the second layer is grown to overlap and merge over tops of the monocrystalline regions of the first semiconductive layer and the top surface is planarized to the level of the monocrystalline regions of the first layer.

### Claim 11 (depends on 1)

The process of claim 1 in which the patterned insulating layer includes a pattern of square openings whereby there is formed over the semiconductive body a semiconductive layer that includes a pattern of columns of square cross-section of different conductivity characteristics.

### Claim 12 (depends on 1)

The process of claim 1 in which the patterned insulating layer includes a pattern of rings whereby the second semiconductive layer formed over the semiconductive body includes ring-shaped regions of different conductivity types.

### Claim 13

A process for producing an epitaxial layer with laterally varying doping comprising the steps of:
applying a patterned insulator layer to a semiconductor body;
growing a first epitaxial layer on the semiconductor body and the patterned insulator layer so that monocrystalline regions are formed over the semiconductor body and polycrystalline regions are formed over the patterned insulator layer, the angle of inclination (α) of the interface between the monocrystalline regions and the polycrystalline regions depending on the grain size of the polycrystalline regions;
removing the polycrystalline regions and the insulator layer; and
growing a second epitaxial layer which, together with the monocrystalline regions of the first epitaxial layer, forms the epitaxial layer.