Method for removing photoresist and other adherent materials from substrates

• US 5,201,960 A
• Filed: 02/26/1992
• Issued: 04/13/1993
• Est. Priority Date: 02/04/1991
• Status: Expired due to Fees

• Current Assignee: Applied Photonics Research Incorporated
• Original Assignee: Applied Photonics Research Incorporated
• Inventors: Starov, Vladimir
• Primary Examiner(s): Morris, Theodore
• Assistant Examiner(s): EL ARINI, ZEINAB
• Application Number:
  US07/841,856
• Time in Patent Office: 412 Days
• Field of Search: 134/11, 134/26, 134/30, 134/31, 134/37
• US Class Current: 134/11
• CPC Class Codes: H01L 21/67023 for general liquid treatment, e.g. etching followed by cleaning

Abstract

A method for removing adherent matrices, such as highly cross-linked photoresist layers, from substrates, such as semiconductor wafers, comprises exposing the matrix to a vapor phase solvent and allowing the solvent to penetrate the matrix. After penetration, the vapor is condensed and then revaporized in order to promote fragmentation of the matrix and facilitate removal. Optionally, the matrix may be treated with a pre-swelling solvent and the resulting fragments removed by washing with a liquid or vapor solvent for the fragmented matrix material.

Claims

1. A method for removing an adherent matrix which is a cross-linked photoresist which has been hardened by baking, ion implantation, ultraviolet radiation, or exposure to a plasma from a substrate surface, said method comprising:

exposing the adherent matrix to a non-oxidizing vapor phase solvent for at least 30 seconds under temperature and pressure conditions selected to allow penetration of the vapor phase solvent into the matrix while the matrix remains substantially intact, wherein said solvent has a vapor pressure of at least one atmosphere at room temperature;

condensing the vapor phase solvent after the matrix has been penetrated but while the matrix remains intact to produce a liquid phase within the adherent matrix, whereby the matrix is structurally disrupted without substantial oxidation to produce non-adherent fragments; and

removing the fragments from the substrate surface.

2. A method as in claim 1, wherein the substrate is a semiconductor wafer.

3. A method as in claim 1, wherein the solvent is selected from the group consisting of ammonia, carbon dioxide, nitrous oxide, hydrocarbons, and chlorofluorocarbons.

4. A method as in claim 1, further comprising exposing the adherent matrix to a preswelling solvent prior to exposing to the vapor phase solvent.

5. A method as in claim 4, wherein the preswelling solvent is selected from the group consisting of DMSO, DMF, NMP, THF, IPA, MIBK, and acetone.

6. A method as in claim 5, wherein the preswelling solvent is exposed to the matrix as a vapor.

7. A method as in claim 5, wherein the preswelling solvent is exposed to the matrix as a liquid.

8. A method as in claim 1, further comprising repeating the steps of exposing the adherent matrix to the vapor phase solvent and condensing the vapor phase solvent at least once prior to removing the fragments.

9. A method as in claim 1, wherein the step of removing the fragments comprises washing the substrate surface with a liquid organic solvent or water.

10. A method as in claim 1, wherein the step of removing the fragments comprises blowing a stream of air, nitrogen, oxygen, or organic solvent vapor against the surface.

11. A method for removing an adherent matrix which is a cross-linked photoresist which has been hardened by baking, ion implantation, ultraviolet radiation, or exposure to a plasma from a surface of a substrate, said method comprising:

placing the substrate within a chamber;

maintaining a preselected temperature within the chamber;

delivering to the chamber a non-oxidizing solvent vapor at a temperature above the chamber temperature and at a pressure below the saturation vapor pressure at the chamber temperature, wherein said solvent has a vapor pressure of at least three atmospheres at room temperature;

increasing the pressure of the solvent vapor within the chamber from an initial value below the saturation vapor pressure to a subsequent value above the saturation vapor pressure, whereby the solvent initially penetrates the matrix while in the vapor phase and thereafter condenses to physically disrupt the matrix to produce fragments; and

removing the fragments from the substrate surface.

12. A method as in claim 11, wherein the substrate is a semiconductor wafer.

13. A method as in claim 11, wherein the solvent is selected from the group consisting of ammonia, carbon dioxide, nitrous oxide, hydrocarbons, and chlorofluorocarbons.

14. A method as in claim 11, further comprising exposing the adherent matrix to a preswelling solvent prior to exposing to the vapor phase solvent.

15. A method as in claim 14, wherein the preswelling solvent is selected from the group consisting of DMSO, DMF, NMP, THF, IPA, MIBK, and acetone.

16. A method as in claim 15, wherein the preswelling solvent is exposed to the matrix as a vapor.

17. A method as in claim 15, wherein the preswelling solvent is exposed to the matrix as a liquid.

18. A method as in claim 11, further comprising decreasing the pressure in the chamber to a value below the saturation vapor pressure, whereby the liquid phase solvent revaporizes to further physically disrupt the matrix.

19. A method as in claim 18, further comprising repeating the steps of delivering a solvent vapor to the chamber and increasing the pressure of solvent within the chamber at least once after decreasing the pressure to revaporize the solvent and prior to removing the fragments.

20. A method as in claim 11, wherein the adherent matrix is exposed to the vapor phase solvent for at least 30 seconds prior to condensation.

21. A method as in claim 11, wherein the step of removing the fragments comprises washing the substrate surface with a liquid organic solvent or water.

22. A method as in claim 11, wherein the step of removing the fragments comprises blowing a stream of air, nitrogen, oxygen, or organic solvent vapor against the surface.

23. A method as in claim 11, wherein the pressure of the solvent vapor delivered to the chamber is the saturation vapor pressure at the solvent delivery temperature.

24. A method as in claim 23, wherein the solvent vapor is delivered to the chamber from a source maintained at said temperature above the chamber temperature, whereby a saturated solvent vapor phase is produced which flows to the chamber under a natural pressure gradient.

25. A method as in claim 24, wherein the pressure in the chamber is controlled by permitting equilibrium to be achieved between the source and the chamber.

26. A method for removing "an adherent matrix which is a cross-linked photoresist which has been hardened by baking, ion implantation, ultraviolet radiation, or exposure to a plasma" from the surface of a semiconductor wafer, said method comprising:

placing the wafer within a chamber;

maintaining a preselected temperature within the chamber;

connecting the chamber to a source of solvent consisting essentially of ammonia which has been heated to a temperature above the preselected chamber temperature, whereby the saturation vapor pressure of the ammonia at the source is sufficient to cause ammonia vapor to flow into the chamber;

allowing the source and the chamber to reach equilibrium pressure, whereby ammonia vapor which has penetrated the cross-linked organic polymer condenses at the lower chamber temperature to physically disrupt the polymer and produce fragments; and

removing the fragments from the water surface.

27. A method as in claim 26, further comprising exposing the cross-linked photoresist to a preswelling solvent prior to exposing to the ammonia.

28. A method as in claim 27, wherein the preswelling solvent is selected from the group consisting of DMSO, DMF, NMP, THF, IPA, MIBK, and acetone.

29. A method as in claim 28, wherein the preswelling solvent is exposed to the matrix as a vapor.

30. A method as in claim 28, wherein the preswelling solvent is exposed to the matrix as a liquid.

31. A method as in claim 26, further comprising decreasing the pressure in the chamber to a value below the saturation vapor pressure, whereby the condensed ammonia revaporizes to further physically disrupt the matrix.

32. A method as in claim 31, further comprising reconnecting the chamber to the source of ammonia and allowing the chamber and source to reach pressure equilibrium after decreasing the chamber pressure and prior to removing the fragments.

33. A method as in claim 26, wherein the adherent matrix is exposed to the vapor phase solvent for at least 30 seconds prior to condensation.

34. A method as in claim 26, wherein the step of removing the fragments comprises washing the substrate surface with a liquid organic solvent or water.

35. A method as in claim 26, wherein the step of removing the fragments comprises blowing a stream of air, nitrogen, oxygen, or organic solvent vapor against the surface.

36. A method as in claim 26, wherein the preselected chamber temperature is in the range from about 20°

C. to 80°

C. and the source temperature is in the range from about 40°

C. to 150°

C.