# US 9,437,432 B1 · Self-compensating oxide layer

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- Number: US 9,437,432 B1
- Document ID: US9437432B1
- Status: Granted
- Kind: B1
- Application number: 14/840,932
- Filed: 2015-08-31
- Granted: 2016-09-06
- Earliest claimed: 2015-08-31
- Assignees: Varian Semiconductor Equipment Associates, Inc.
- Applicants: Varian Semiconductor Equipment Associates, Inc.
- Inventors: Helen L. Maynard; Deven Raj Mittal; Jun Seok Lee
- Web page: https://patentgrep.com/patent/US9437432B1

## CPC

- H10P 30/204: {into Group IV semiconductors}
- H10D 30/0241: {doping of vertical sidewalls, e.g. using tilted or multi-angled implants}
- H10P 30/212: {Through-implantation}
- H10P 30/208: {of electrically inactive species}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A method of conformally doping a device on a semiconductor workpiece is disclosed. An oxide layer is applied to all surfaces of the device. Further, the thickness of the oxide layer on each surface is proportional to the energy that ions impact that particular surface. For example, ions strike the horizontal surfaces at nearly a normal angle and penetrate more deeply into the workpiece than ions striking the vertical surfaces. After creating an oxide layer that has a variable thickness, a subsequent dopant implant is performed. While ions strike the horizontal surfaces with more energy, these ions pass through a thicker oxide layer to penetrate the workpiece. In contrast, ions strike the vertical surfaces with less energy, but traverse a much thinner oxide layer to penetrate the workpiece. The result is a conformally doped device.

## Claims

### Claim 1

A method of doping a workpiece having at least two surfaces of different orientations, comprising:
applying an oxide layer to the at least two surfaces of the workpiece, where a thickness of the oxide layer on each surface of the workpiece is proportional to an energy at which ions strike that surface during implant and wherein a thickness of the oxide layer is greater on one of the at least two surfaces of the workpiece due to the orientation of the one surface;
performing an implant of a dopant species to the workpiece after the oxide layer has been applied; and
removing the oxide layer after implanting the dopant species.

### Claim 2 (depends on 1)

The method of claim 1, wherein the applying is performed by depositing an oxide on the workpiece.

### Claim 3 (depends on 1)

The method of claim 1, wherein the applying comprises:
performing an amorphizing implant to the workpiece; and
exposing the workpiece to oxygen after the amorphizing implant to create an oxide layer.

### Claim 4 (depends on 3)

The method of claim 3, wherein the amorphizing implant is performing using germanium, xenon or argon.

### Claim 5

A method of doping a workpiece, comprising:
amorphizing portions of the workpiece by implanting a first species into the workpiece, wherein implanted portions of the workpiece become amorphized regions and a remainder of the workpiece remains crystalline;
exposing the workpiece to oxygen after the amorphizing, wherein the amorphized regions of the workpiece are converted to a silicon oxide layer, wherein a thickness of the silicon oxide layer is greater on certain surfaces of the workpiece based on orientation of the surfaces;
implanting a dopant species into the workpiece after the exposing such that the dopant species travel through the silicon oxide layer to reach a crystalline portion of the workpiece disposed beneath the silicon oxide layer; and
removing the silicon oxide layer.

### Claim 6 (depends on 5)

The method of claim 5, further comprising applying a mask to one or more surfaces of the workpiece prior to the amorphizing.

### Claim 7 (depends on 5)

The method of claim 5, wherein a thickness of the silicon oxide layer on a surface of the workpiece is proportional to an energy at which the first species is implanted into that surface.

### Claim 8 (depends on 5)

The method of claim 5, further comprising subjecting the workpiece to a thermal treatment after the implanting.

### Claim 9 (depends on 8)

The method of claim 8, wherein the thermal treatment is performed prior to the removing.

### Claim 10 (depends on 5)

The method of claim 5, wherein a depth and concentration of dopant species that is implanted in the crystalline portion of the workpiece are substantially equal for all surfaces of the workpiece.

### Claim 11 (depends on 5)

The method of claim 5, wherein the first species comprises germanium, xenon argon, helium or hydrogen.

### Claim 12

A method of creating a conformally doped structure on a workpiece, comprising:
amorphizing at least one horizontal surface and at least one non-horizontal surface of a structure on a workpiece by implanting a first species into the structure, wherein implanted regions of the structure become amorphized regions and a remainder of the structure remains crystalline;
exposing the structure to oxygen after the amorphizing, wherein the amorphized regions of the structure are converted to a silicon oxide layer;
implanting a dopant species into the structure after the exposing such that ions of the dopant species travel through the silicon oxide layer to reach a crystalline portion of the structure disposed beneath the silicon oxide layer; and
removing the silicon oxide layer from the structure.

### Claim 13 (depends on 12)

The method of claim 12, wherein a thickness of the silicon oxide layer on the at least one horizontal surface is greater than a thickness of the silicon oxide layer on the at least one non-horizontal surface.

### Claim 14 (depends on 12)

The method of claim 12, wherein the structure has desired dimensions and the structure is formed having dimensions different than the desired dimensions to account for removal of the silicon oxide layer.

### Claim 15 (depends on 12)

The method of claim 12, further comprising subjecting the workpiece to a thermal treatment after the implanting.

### Claim 16 (depends on 15)

The method of claim 15, wherein the thermal treatment is performed prior to the removing.

### Claim 17 (depends on 12)

The method of claim 12, wherein a depth and concentration of dopant species that are implanted in the crystalline portion of the workpiece disposed beneath the silicon oxide layer is substantially equal for all surfaces.