HF vapor phase wafer cleaning and oxide etching

• US 6,740,247 B1
• Filed: 02/04/2000
• Issued: 05/25/2004
• Est. Priority Date: 02/05/1999
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Sawin, Herbert H., Han, Yong-Pil
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): CULBERT, ROBERTS P
• Application Number:
  US09/498,303
• Time in Patent Office: 1,572 Days
• Field of Search: 216/73, 216/79, 216/80, 438/706, 438/743, 134/2, 134/31
• US Class Current: 216/73
• CPC Class Codes: H01L 21/02049 with gaseous HF
• CPC Class Codes: H01L 21/31116 by dry-etching

Abstract

The invention provides HF vapor process conditions that can be precisely controlled with a high degree of reproducibility for a wide range of starting wafer conditions. These HF vapor processes for, e.g., etching oxide on a semiconductor substrate, cleaning a contaminant on a semiconductor substrate, removing etch residue from a metal structure on a semiconductor substrate, and cleaning a metal contact region of a semiconductor substrate. In the HF vapor process, a semiconductor substrate having oxide, a contaminant, metal etch residue, or a contact region to be processed is exposed to hydrofluoric acid vapor and water vapor in a process chamber held at temperature and pressure conditions that are controlled to form on the substrate no more than a sub-monolayer of etch reactants and products produced by the vapor as the substrate is processed by the vapor. The sub-monolayer HF vapor process regime is defined in accordance with the invention to proceed under conditions wherein no more than about 95% of a monolayer of coverage of the substrate surface occurs.

Claims

1. A method for etching oxide on a semiconductor substrate, comprising the steps of:

producing a positive electrical charge on the oxide; and

subsequent to the positive electrical charge production, exposing the previously positively charged oxide on the substrate to hydrofluoric acid vapor and water vapor in a process chamber held at temperature and pressure conditions that are controlled to form on the substrate no more than a saturated monolayer of etch reactants and products produced by the vapor as the oxide is etched by the vapor.

4. The method of any of claims 1, 2, or 3 wherein the process chamber temperature and pressure conditions are controlled to form on the substrate no more than a sub-monolayer of etch reactants and products produced by the vapor as the oxide is etched by the vapor.

6. The method of any of claims 1, 2, or 3 wherein the positive electrical charge is produced on the oxide by exposure of the oxide to ultraviolet light through an electrically-biased metallic screen.

7. The method of any of claims 1, 2, or 3 wherein the positive electrical charge is produced on the oxide by exposure of the oxide to a plasma environment wherein the substrate is capacitively biased by a negative-polarity DC voltage.

2. A method for etching oxide on a semiconductor substrate, comprising the steps of:

producing a positive electrical charge on the oxide; and

subsequent to the positive electrical charge production, exposing the previously positively charged oxide on the substrate to hydrofluoric acid vapor and methanol vapor in a process chamber held at temperature and pressure conditions that are controlled to form on the substrate no more than a saturated monolayer of etch reactants and products produced by the vapor as the oxide is etched by the vapor.

3. A method for etching oxide on a semiconductor substrate, comprising the steps of:

producing a positive electrical charge on the oxide; and

subsequent to the positive electrical charge production, exposing the previously positively charged oxide on the substrate to hydrofluoric acid vapor and isopropyl alcohol vapor in a process chamber held at temperature and pressure conditions that are controlled to form on the substrate no more than a saturated monolayer of etch reactants and products produced by the vapor as the oxide is etched by the vapor.

5. The method of any of clam 1, 2, or 3 wherein the positive electrical charge is produced on the oxide by exposure of the oxide to an electron beam.

8. A method for etching oxide on a semiconductor substrate, comprising the steps of:

producing a negative electrical charge on the oxide; and

subsequent to the negative electrical charge production, exposing the previously negatively electrically charged oxide on the substrate to hydrofluoric acid vapor and water vapor in a process chamber held at temperature and pressure conditions that are controlled to form on the substrate no more than a multilayer of etch reactants and products produced by the vapor as the oxide is etched by the vapor.

9. The method of claim 8 wherein the negative electrical charge is produced on the oxide by exposure of the oxide to a plasma environment wherein the wherein the substrate is capacitively biased by a RF voltage.

10. The method of claim 8 wherein the negative electrical charge is produced on the oxide by exposure of the oxide to a plasma environment wherein the substrate is capacitively biased by a positive-polarity DC voltage.