System and methods for polishing a wafer

• US 7,378,355 B2
• Filed: 05/11/2005
• Issued: 05/27/2008
• Est. Priority Date: 05/09/1997
• Status: Expired due to Fees

• Current Assignee: OEM Group, LLC
• Original Assignee: Semitool Incorporated (Applied Materials Incorporated)
• Inventors: Gebhart, Thomas Maximilian, Bergman, Eric J.
• Primary Examiner(s): Ghyka; Alexander G.
• Application Number:
  US11/127,052
• Publication Number:
  US 20050236363A1
• Time in Patent Office: 1,112 Days
• Field of Search: 438/745, 438/753, 216/88
• US Class Current: 438/753
• CPC Class Codes: H01L 21/02019 Chemical etching
• CPC Class Codes: H01L 21/02024 Mirror polishing
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/6708 using mainly spraying means, e.g. nozzles
• CPC Class Codes: H01L 21/67086 with the semiconductor substrates being dipped in baths or vessels

Abstract

In methods for smoothing or polishing a surface of a wafer, such as a silicon wafer, a liquid layer is formed on a surface of the wafer. The liquid layer may be an invisible microscopic layer, or a visible macroscopic layer. A flow of an oxidizing gas is directed over, against or onto the liquid layer of the surface of the wafer, in the presence of an etchant. The flow of gas thins the liquid layer at high points or areas on the surface of the wafer more than at low points or areas on the wafer surface. Consequently, the high points are oxidized and etched away more than the low points. As a result, the wafer surface is smoothed and polished.

Claims

1. A method for smoothing a surface of a wafer, comprising:

forming a liquid layer on a surface of the wafer, with the liquid layer including an acid;

directing a flow of an oxidizing gas across the liquid layer, with the flow of oxidizing gas thinning the liquid layer at high points on the surface of the wafer more than at low points on the wafer surface; and

with the flow of oxidizing gas oxidizing and removing at least one micron of wafer material from the high points on the wafer surface, to smooth the wafer surface.

2. The method of claim 1 with the acid provided as a vapor with the oxidizing gas.

3. The method of claim 2 wherein the acid comprises a liquid sprayed onto the wafer.

4. The method of claim 1 wherein the oxidizing gas comprises ozone.

5. The method of claim 1 wherein the flow is directed at an angle relative to the surface of the wafer ranging from about 0 to 45°

.

6. The method of claim 1 further comprising spinning the wafer.

7. The method of claim 1 wherein the liquid layer further comprises a surfactant.

8. A method for polishing a surface of a silicon wafer, comprising:

forming a layer of heated liquid on a surface of the workpiece, with the liquid comprising water and a silicon etchant;

spinning the workpiece;

directing a spray of ozone gas at the liquid layer from at least one nozzle adjacent to the wafer, with the spray of ozone gas thinning the liquid layer at high points on the workpiece surface more than at low points of the workpiece surface, and with the ozone gas chemically reacting with the surface of the wafer at the high points to remove at least one micron of silicon, resulting in polishing of the surface of the wafer.

9. The method of claim 8 further comprising spinning the wafer at 1-50 rpm.

10. The method of claim 8 with the spray of ozone gas directed at an angle relative to the liquid layer ranging from 0-45 degrees.

11. The method of claim 8 wherein the liquid is heated to a temperature ranging from about 30-99°

C.

12. The method of claim 8 wherein the spray of ozone gas is directed substantially parallel to the surface of the liquid layer.

13. The method of claim 8 wherein the liquid film is microscopic and not visible.

14. The method of claim 8 wherein the liquid film is created by condensation of a vapor onto the wafer.

16. The method of claim 8 further comprising spinning the wafer at 1-50 rpm.

15. A method for polishing a surface of a silicon wafer, comprising:

forming a layer of heated liquid on a surface of the workpiece, with the liquid comprising water and an acid;

directing a jet of ozone gas at a target area on the surface of the wafer, with the jet of ozone gas having an initial velocity of more than about 20 meters/second, and with the jet of ozone gas thinning the liquid layer on the target area, and with the liquid layer at high points of the wafer surface in the target area thinned more than the liquid layer at low points in the target area;

removing at least five microns of silicon material from high points in the target area via chemical reaction between the silicon material at the high points and the spray of ozone gas, to polish the surface of the wafer.