REMOVAL OF SURFACE DOPANTS FROM A SUBSTRATE

• US 20090162996A1
• Filed: 12/21/2007
• Published: 06/25/2009
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Foad, Majeed A., Ramaswamy, Kartik, Hilkene, Martin A., Hanawa, Hiroji, Scotney-Castle, Matthew D., Collins, Kenneth S., Gallo, Biagio, Santhanam, Kartik
• Granted Patent: US 7,989,329 B2
• Time in Patent Office: Days
• US Class Current: 438/477
• CPC Class Codes: H01L 21/2253 by ion implantation
• CPC Class Codes: H01L 21/2254 from or through or into an applied layer, e.g. photoresist, nitrides

Abstract

A method and apparatus for removing excess dopant from a doped substrate is provided. In one embodiment, a substrate is doped by surfaced deposition of dopant followed by formation of a capping layer and thermal diffusion drive-in. A reactive etchant mixture is provided to the process chamber, with optional plasma, to etch away the capping layer and form volatile compounds by reacting with excess dopant. In another embodiment, a substrate is doped by energetic implantation of dopant. A reactive gas mixture is provided to the process chamber, with optional plasma, to remove excess dopant adsorbed on the surface and high-concentration dopant near the surface by reacting with the dopant to form volatile compounds. The reactive gas mixture may be provided during thermal treatment, or it may be provided before or after at temperatures different from the thermal treatment temperature. The volatile compounds are removed. Substrates so treated do not form toxic compounds when stored or transported outside process equipment.

Claims

1. A method of treating a substrate containing dopants, comprising:

disposing the substrate in one or more chambers;

providing a dopant removal mixture to the one or more chambers;

producing one or more volatile compounds in at least one of the chambers by applying the dopant removal mixture to the substrate; and

removing the one or more volatile compounds from the one or more chambers.

2. The method of claim 1, wherein the dopants comprise boron (B), arsenic (As), phosphorus (P), or combinations thereof.

3. The method of claim 1, wherein the dopant removal mixture comprises hydrogen (H₂), nitrogen (N₂), oxygen (O₂), ammonia (NH₃), nitrogen trifluoride (NF₃), silicon tetrafluoride (SiF₄), air, or combinations thereof.

4. The method of claim 1, wherein the one or more volatile compounds comprise arsine (AsH₃), phosphine (PH₃), borane (BH₃), diborane (B₂H₆), borazine (B₃H₆N₃), or combinations and derivatives thereof.

5. The method of claim 1, wherein the substrate is thermally controlled at one or more temperatures selected to encourage the one or more volatile compounds to evaporate from the substrate.

6. The method of claim 5, wherein the one or more temperatures are at least about 50°

C.

7. A method of annealing a doped substrate in one or more chambers, comprising:

providing one or more dopant removal mixtures to at least one of the chambers;

forming one or more plasmas of the dopant removal mixture;

exposing the doped substrate to the one or more plasmas;

producing one or more volatile compounds in the one or more chambers by applying the one or more plasmas to the substrate; and

removing the one or more volatile compounds from the one or more chambers.

8. The method of claim 7, wherein dopants implanted in the doped substrate comprise boron (B), arsenic (As), phosphorus (P), or combinations thereof.

9. The method of claim 7, wherein at least one of the plasmas is an inductively coupled plasma.

10. The method of claim 7, further comprising thermally treating the substrate at one or more temperatures selected to cause diffusion and activation of dopants in the substrate.

11. The method of claim 7, wherein at least one of the plasmas is generated outside the one or more chambers.

12. The method of claim 10, wherein the one or more temperatures comprise a first temperature for producing the one or more volatile compounds and a second temperature for thermally treating the substrate.

13. The method of claim 12, wherein the first temperature is at least about 50°

C.

14. A process for treating a silicon-containing substrate in a process chamber, comprising:

depositing a layer of dopants on at least a portion of a surface of the substrate;

forming a capping layer over at least a portion of the dopant layer;

thermally treating the substrate to diffuse the dopants into the substrate and activate them;

providing a reactive etchant to the process chamber;

removing the capping layer from the dopant layer;

forming one or more volatile compounds by reacting the etchant with dopants; and

removing the one or more volatile compounds from the process chamber.

15. The process of claim 14, wherein the dopants comprise boron (B), arsenic (As), phosphorus (P), or combinations thereof.

16. The process of claim 14, wherein the capping layer comprises silicon, oxygen, carbon, nitrogen, metal, or combinations thereof.

17. The process of claim 14, wherein the capping layer is an anti-reflective coating.

18. The process of claim 14, wherein the etchant comprises nitrogen trifluoride (NF₃), silicon tetrafluoride (SiF₄), or combinations thereof.

19. The process of claim 14, further comprising forming a plasma of the reactive etchant.

20. The process of claim 19, wherein the plasma is a remote plasma.

21. The process of claim 19, wherein the plasma is inductively coupled.

22. A method of removing high-concentration dopants from a surface region of a substrate, comprising:

exposing the surface region to a gas mixture;

forming one or more volatile compounds by reacting the gas mixture with dopants in the surface region; and

removing the one or more volatile compounds from the substrate.

23. The method of claim 22, wherein the dopants comprise boron (B), arsenic (As), phosphorus (P), or combinations thereof.

24. The method of claim 22, wherein the substrate is thermally controlled at a temperature selected to encourage the one or more volatile compounds to evaporate from the surface region of the substrate.

25. The method of claim 22, further comprising forming a plasma from the reactive gas mixture.