Method for surface treatment of substrates

• US 6,221,774 B1
• Filed: 04/05/1999
• Issued: 04/24/2001
• Est. Priority Date: 04/10/1998
• Status: Expired due to Term

• Current Assignee: Silicon Genesis
• Original Assignee: Silicon Genesis
• Inventors: Malik, Igor J.
• Primary Examiner(s): KUNEMUND, ROBERT M
• Application Number:
  US09/286,259
• Time in Patent Office: 750 Days
• Field of Search: 438/690, 438/691, 438/692, 216/89, 216/92
• US Class Current: 438/690
• CPC Class Codes: B24B 37/105 the workpieces or work carriers being actively moved by a drive, e.g. in a combined rotary and translatory movement
• CPC Class Codes: H01L 21/67046 using mainly scrubbing means, e.g. brushes

Abstract

A polishing pad (24) is rotated about an axis parallel to a surface (10) of a semiconductor wafer (12). The polishing pad (24) is supported by a roller (22) that receives fluid (38) and distributes the fluid through the polishing pad (24) across the surface of the wafer. The surface (10) of the wafer is moved in relation to the polishing pad so that the wafer surface is smoothed, or touch-polished, with or without the use of abrasive slurry. In one embodiment the wafer is rotated between an upper roller assembly (20) and a lower roller assembly (14). In another embodiment, the polishing pad is held at an angle to the surface of the wafer to remove a ridge of material from a donor wafer for re-use in a thin film transfer process.

Claims

1. A method of finishing a surface of a semiconductor substrate comprising steps of:

(a) bonding a donor substrate to a target substrate;

(b) separating a thin film of donor semiconductor material from the donor substrate, the thin film of donor material adhering to the target substrate to form a composite substrate with a separated surface; and

(c) touch-polishing the separated surface with an essentially cylindrical polishing pad, the polishing pad rotating about a first axis, the first axis being essentially parallel to the separated surface, while moving the separated surface relative to a contact polishing area of the polishing pad.

2. The method of claim 1 wherein the donor substrate comprises a semiconductor material.

3. The method of claim 2 wherein the donor substrate comprises single-crystal silicon.

4. The method of claim 1 wherein the th in film comprises polysilicon.

5. The method of claim 2 wherein the target substrate is a silicon wafer.

6. The method of claim 2 further comprising a step, after the step (b) and prior to the step (c) of pre-polishing the separated surface.

7. The method of claim 6 wherein the step of pre-polishing includes growing an oxide layer on the separated surface and stripping the oxide layer.

8. The method of claim 2 wherein the target substrate comprises silicon oxide.

9. The method of claim 1 wherein the step (c) includes rotating the composite substrate about a second axis relative to a roller, the roller holding the polishing pad in contact with the composite substrate, the second axis being essentially normal to the cleaved surface.

10. The method of claim 1 wherein the thin film is separated from the donor substrate by a controlled cleave process.

11. The method of claim 1 wherein the thin film is separated from the donor substrate by a blister separation method.

12. The method of claim 1 wherein the step (c) of touch polishing includes use of a slurry.

13. A method of finishing a cleaved surface of a donor wafer comprising steps of:

(a) separating a thin film of material from the donor wafer to form a separated surface on the donor wafer; and

(b) touch-polishing the separated surface with an essentially cylindrical polishing pad, the polishing pad rotating about a first axis, the first axis forming an angle between about 0-30 degrees with the separated surface, while moving the separated surface relative to a contact area of the polishing pad.

14. A method of finishing a surface of an epitaxial wafer comprising steps of:

(a) growing an epitaxial layer on a surface of a substrate to form an epitaxial wafer with an epitaxial surface; and

(b) touch-polishing the epitaxial surface with an essentially cylindrical polishing pad, the polishing pad rotating about a first axis, the first axis being essentially parallel to the epitaxial surface, while moving the epitaxial surface relative to a polishing contact area of the polishing pad.

15. The method of claim 14 wherein the epitaxial surface comprises silicon.

16. The method of claim 14 wherein the epitaxial surface comprises a compound semiconductor material selected from the group consisting of gallium arsenide, silicon carbide, gallium nitride, and silicon-germanium.

17. The method of claim 14 wherein the epitaxial surface is on a compliant substrate.

18. The method of claim 14 wherein the substrate is a single-crystal silicon wafer.

19. The method of claim 14 wherein the step (c) includes rotating the epitaxial wafer about a second axis, the second axis being essentially normal to the epitaxial surface.

20. A method of finishing a surface of a semiconductor substrate, the method comprising steps of:

(a) providing a semiconductor substrate, the surface having an initial surface roughness of less than about 500 Å

RMS;

(b) pressing a polishing pad against the surface of the semiconductor substrate with a cylindrical polishing bar to form a linear contact area between the polishing pad and the surface of the semiconductor substrate; and

(c) moving the surface of the substrate relative to the linear contact area.

21. The method of claim 20 wherein the cylindrical polishing bar comprises a roller.

22. The method of claim 20 further comprising a step of providing the polishing pad from a source roller to the linear contact area.

23. A method of finishing a surface of a semiconductor substrate, the method comprising steps of:

(a) pre-polishing the surface of the semiconductor substrate to obtain a surface roughness of less than about 300 Å

RMS; and

(b) touch-polishing the surface of the semiconductor substrate with a polishing pad, the polishing pad being held in contact with the semiconductor substrate by a polishing roller rotating about a first axis, the first axis being essentially parallel to the surface of the semiconductor substrate, while moving the surface of the semiconductor substrate relative to a contact area of the polishing pad in contact with the semiconductor substrate.

24. The method of claim 23 wherein the semiconductor is a bulk silicon wafer.

25. A method of finishing a surface of a silicon substrate comprising steps of:

(a) implanting insulator-forming particles through a polished surface of the silicon substrate;

(b) pre-smoothing the silicon substrate; and

(c) touch-polishing the surface of the silicon substrate with an essentially cylindrical polishing pad, the polishing pad rotating about a first axis, the first axis being essentially parallel to the surface of the semiconductor substrate, while moving the surface of the semiconductor substrate relative to a contact area of the polishing pad.

26. The method of claim 25 wherein the insulator-forming particles comprise nitrogen.

27. The method of claim 25 wherein the insulator-forming particles comprise oxygen.

28. The method of claim 25 further comprising post-smoothing the silicon substrate after the step (c) of touch-polishing.

29. A method of converting a double-brush scrubber to a wafer surface finishing system, the method comprising steps of:

(a) installing a polishing pad on at least one roller of a double-brush scrubber for polishing the wafer surface with the polishing pad; and

(b) setting the one roller in relation to an opposing roller such that, during a wafer surface finishing operation, a contact force between a contact area of the polishing pad and the wafer surface is greater than about 2 psi.

30. The method of claim 29 further comprising a step, prior to the step (a), of perforating the polishing pad to form a plurality of conduits for fluid to flow from an interior portion of the one roller through the conduits.

31. The method of claim 29 wherein the polishing pad includes a matrix containing embedded abrasive particles.

32. A method of preparing a surface of a donor wafer for re-use in a thin-film transfer process, the method comprising:

(a) providing a donor wafer having a ridge of donor material in a perimeter region of a surface of the donor wafer;

(b) applying a polishing pad to only the perimeter region of the surface of the donor wafer such that the polishing pad contacts at least the ridge of donor material; and

(c) moving the donor wafer relative to the polishing pad to remove the ridge of donor material from the donor wafer.

33. A method of finishing a surface of a composite thin film wafer, the thin film transfer wafer having a thin film of material bonded to a handle wafer, the perimeter of the thin film of material forming a step with the handle wafer, the method comprising:

(a) supporting the composite thin film wafer with a wafer support;

(b) pressing a polishing pad against the composite thin film wafer at an angle greater than about 0 degree between the polishing pad and a surface of the composite thin film wafer to selectively engage the step; and

(c) moving the composite thin film wafer relative to the polishing pad to smooth the step.