Apparatus and method for direct current plasma immersion ion implantation

• US 20030116090A1
• Filed: 02/13/2003
• Published: 06/26/2003
• Est. Priority Date: 03/23/2000
• Status: Abandoned Application

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: Kwok, Dixon T.K., Zeng, Xuchu, Chu, Paul K.
• Application Number:
  US10/366,193
• Publication Number:
  US 20030116090A1
• Time in Patent Office: Days
• US Class Current: 118/723E
• CPC Class Codes: C23C 14/48 Ion implantation
• CPC Class Codes: C23C 8/36 using ionised gases, e.g. ionitriding
• CPC Class Codes: H01J 37/32412 Plasma immersion ion implantation
• CPC Class Codes: H01J 37/32697 Electrostatic control

Abstract

An apparatus and method are disclosed for a low-pressure steady-state direct current or long-pulse mode of plasma immersion ion implantation. A conducting grid is located between the wafer stage and the supply of plasma. The supply of plasma may be controlled through a variable aperture in which is provided the conducting grid.

Claims

1. Apparatus for direct current plasma ion implantation, comprising:

(a) a vacuum chamber,

(b) an ion/plasma source

(c) means for supporting a target in said chamber,

(d) means for applying an electrical potential to said target supporting means, and

(e) a conducting grid being located between said target supporting means and said ion/plasma source dividing said chamber into two parts.

2. Apparatus as claimed in claim 1 wherein said conducting grid is grounded and said target supporting means is maintained at a negative potential.

3. Apparatus as claimed in claim 1 wherein said conducting grid is maintained at a positive or negative potential.

4. Apparatus as claimed in claim 1 wherein said vacuum chamber has a disk-like shape.

5. Apparatus as claimed in claim 4 wherein the dimensions of the chamber have the ratio r:

R;

H;

D=1;

4;

2.5;

2 where;

r=radius of the target

R=radius of the vacuum chamber

H=the distance between the target and the grid, and

D=the thickness of the target.

6. Apparatus as claimed in claim 1 wherein the grid is made of a material compatible with an intended target.

7. Apparatus as claimed in claim 6 wherein the intended target is a silicon wafer and the grid is made of a silicon mesh.

8. Apparatus as claimed in claim 1 wherein means are provided for varying the distance between the target supporting means and the conducting grid.

9. Apparatus as claimed in claim 1 wherein said vacuum chamber is divided into said two parts by a wall of said chamber, said wall being provided with an aperture allowing plasma formed in a first of said two part to diffuse into the second of said two parts containing said target, and wherein said conducting grid is provided across said aperture.

10. Apparatus as claimed in claim 9 wherein said aperture has a variable size.

11. Apparatus as claimed in claim 1 wherein said ion/plasma source is a radio-frequency inductively-coupled plasma source.

12. Apparatus as claimed in claim 1 wherein said ion/plasma source is an electron cyclotron resonance plasma source.

13. A method of plasma immersion ion implantation, comprising:

(a) providing on a supporting means within a vacuum chamber a target to be implanted,

(b) providing an ion/plasma source to said chamber,

(c) providing a conducting grid extending across said chamber and being located between said target and said ion/plasma source,

(d) maintaining a low pressure plasma in a space defined between said source and said grid, and

(e) maintaining said target supporting means at an electrical potential negative relative to said grid.

14. A method as claimed in claim 13 wherein said grid is maintained at a ground potential.

15. A method as claimed in claim 13 wherein said conducting grid is maintained at a first negative potential and said target supporting means is maintained at a second negative potential, said wafer stage being maintained at a negative potential relative to said conducting grid.

16. A method as claimed in claim 13 wherein said method is a DC method in which a continuous ion current is established between said grid and said target.

17. A method as claimed in claim 13 wherein said method is a long-pulse method in which said target is provided with a negative potential for long pulses.

18. A method as claimed in claim 17 wherein said pulses have a duration of from 100 μ

s to 500 μ

s.