Method for sulfuric acid resist stripping

• US 6,032,682 A
• Filed: 06/24/1997
• Issued: 03/07/2000
• Est. Priority Date: 06/25/1996
• Status: Expired due to Fees

• Current Assignee: Scp Services, Inc.
• Original Assignee: CFMT Inc.
• Inventors: Verhaverbeke, Steven
• Primary Examiner(s): Utech, Benjamin
• Assistant Examiner(s): GOUDREAU, GEORGE A
• Application Number:
  US08/881,267
• Time in Patent Office: 987 Days
• Field of Search: 134/1.3, 216/83, 438/745
• US Class Current: 134/1.3
• CPC Class Codes: B08B 3/08 the liquid having chemical or dissolving effect substances used, see the relevant classes
• CPC Class Codes: C11D 2111/22 Electronic devices, e.g. PCBs or semiconductors
• CPC Class Codes: G03F 7/423 containing mineral acids or salts thereof, containing mineral oxidizing substances, e.g. peroxy compounds
• CPC Class Codes: H01L 21/02052 Wet cleaning only H01L21/02085 takes precedence
• CPC Class Codes: H01L 21/31111 by chemical means
• CPC Class Codes: H01L 21/31133 by chemical means

Abstract

The present invention provides methods for efficiently cleaning semiconductor wafers, and particularly for removing photoresist material from the surfaces of semiconductor wafers, using a mixture of sulfuric acid and hydrogen peroxide. In accordance with the present invention, an initial sulfuric acid-based photoresist stripping bath, either being pure sulfuric acid or a sulfuric acid:hydrogen peroxide mixture with a ratio of at least 15:0.3, based on the anhydrous chemical substances, is prepared for processing an initial batch of wafers. During the processing of the semiconductor wafers, hydrogen peroxide is added to the bath solution at a controlled rate of between about 0.015-1.5 g H₂ O₂ (anhydrous basis)/min./liter of photoresist bath solution. In such a way, the conversion of hydrogen peroxide to Caro'"'"'s acid is optimized resulting in an extended bath life and conservation of hydrogen peroxide.

Claims

1. A method for stripping ashed photoresist material from an exposed surface of a semiconductor wafer comprising:

(a) preparing an initial bath solution consisting essentially of sulfuric acid (H₂ SO₄);

(b) adding hydrogen peroxide (H₂ O₂) to the initial bath solution to produce a processing bath solution, the rate of addition of the hydrogen peroxide being from about 0.015 to about 1.5 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution;

(c) processing the semiconductor wafers through the processing bath solution by contacting the surfaces of the semiconductor wafers with the processing bath solution and removing ashed photoresist material from the semiconductor wafers, wherein the processing bath solution has a temperature of about 90°

C. during the processing of the semiconductor wafers; and

(d) maintaining the rate of hydrogen peroxide addition during the processing of the semiconductor wafers.

2. The method of claim 1 where the rate of addition of the hydrogen peroxide is from about 0.05 to about 0.7 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution.

14. The method of claim 1 further comprising feeding ozone into the processing bath solution during processing of the semiconductor wafers.

3. A method for stripping ashed photoresist material from an exposed surface of a semiconductor wafer comprising:

(a) providing an initial bath solution comprising sulfuric acid (H₂ SO₄) and hydrogen peroxide (H₂ O₂), where the ratio of sulfuric acid to hydrogen peroxide used to prepare the initial bath solution is greater than 15;

0.3, referring to volume quantities of the anhydrous chemical substances;

(b) adding hydrogen peroxide to the initial bath solution to produce a processing bath solution, the rate of addition of the hydrogen peroxide being from about 0.015 to about 1.5 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution;

(c) processing semiconductor wafers through the processing bath solution by contacting the surfaces of the semiconductor wafers with the processing bath solution and removing ashed photoresist material from the semiconductor wafers, wherein the processing bath solution has a temperature of about 90°

C. during the processing of the semiconductor wafers; and

(d) maintaining the rate of hydrogen peroxide addition during the processing of the semiconductor wafers.

4. The method of claim 3 wherein the ratio of sulfuric acid to hydrogen peroxide in the initial bath solution is greater than 20:

0.3, referring to volume quantities of the anhydrous chemical substances.

5. The method of claim 3 where the rate of addition of the hydrogen peroxide is from about 0.05 to about 0.7 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution.

13. The method of claim 3 further comprising feeding ozone into the processing bath solution during the processing of the semiconductor wafers.

6. A method for stripping ashed photoresist material from an exposed surface of a semiconductor wafer comprising:

(a) preparing an initial bath solution by adding concentrated sulfuric acid (H₂ SO₄), being at least 95% by weight sulfuric acid, with dilute hydrogen peroxide (H₂ O₂), being between about 25-35% by weight hydrogen peroxide, where the ratio of sulfuric acid to hydrogen peroxide used to prepare the initial bath solution is greater than 15;

0.3, referring to volume quantities of the anhydrous chemical substances;

(b) adding dilute hydrogen peroxide, being between 25-35% by weight hydrogen peroxide, to the initial bath solution to create a processing bath solution, the rate of addition of the hydrogen peroxide being from about 0.05 to about 5 ml H₂ O₂ /min./liter of the processing bath solution;

(c) processing semiconductor wafers through the processing bath solution by contacting the surfaces of the semiconductor wafers with the processing bath solution and removing ashed photoresist material from the semiconductor wafers, wherein the processing bath solution has a temperature of about 90°

C. during the processing of the semiconductor wafers; and

(d) maintaining the rate of hydrogen peroxide addition during the processing of the semiconductor wafers.

7. The method of claim 6 wherein the ratio of sulfuric acid to hydrogen peroxide used to prepare the initial bath solution prior to the processing of the semiconductor wafers is greater than 20:

0.3, referring to volume quantities of the anhydrous chemical substances.

8. The method of claim 6 wherein the rate of addition of the hydrogen peroxide is from about 0.15 to about 2.1 ml H₂ O₂ /min./liter of the processing bath solution.

9. A method for stripping photoresist material from an exposed surface of a semiconductor wafer or for cleaning an exposed surface of semiconductor wafers in general, comprising:

(a) preparing an initial bath solution consisting essentially of sulfuric acid (H₂ SO₄);

(b) processing a first batch of semiconductor wafers within the initial bath solution by contacting the surfaces of the semiconductor wafers with the initial bath solution;

(c) adding hydrogen peroxide (H₂ O₂) to the initial bath solution, during the processing of the first batch of semiconductor wafers, to produce a processing bath solution, the rate of addition of the hydrogen peroxide being from about 0.015 to about 1.5 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution;

(d) processing subsequent batches of semiconductor wafers within the processing bath solution by contacting the surfaces of the semiconductor wafers with the processing bath solution; and

(e) maintaining the rate of hydrogen peroxide addition to the processing bath solution during the processing of the subsequent batches of semiconductor wafers.

10. The method of claim 9 wherein the rate of addition of the hydrogen peroxide is from about 0.05 to about 0.7 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution.

11. A method for stripping ashed photoresist material from an exposed surface of a semiconductor wafer comprising:

(a) providing an initial bath solution comprising sulfuric acid (H₂ SO₄) and hydrogen peroxide (H₂ O₂), where the ratio of sulfuric acid to hydrogen peroxide used to prepare the initial bath solution is greater than 15;

0.3, referring to volume quantities of the anhydrous chemical substances;

(b) processing a first batch of semiconductor wafers within the initial bath solution by contacting the surfaces of the semiconductor wafers with the initial bath solution and removing ashed photoresist material from the semiconductor wafers, wherein the initial bath solution has a temperature of about 90°

C. during the processing of the first batch of semiconductor wafers;

(c) adding hydrogen peroxide to the initial bath solution, during the processing of the first batch of semiconductor wafers, to produce a processing bath solution, the rate of addition of the hydrogen peroxide being from about 0.015 to about 1.5 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution;

(d) processing subsequent batches of semiconductor wafers within the processing bath solution by contacting the surfaces of the semiconductor wafers with the processing bath solution and removing ashed photoresist material from the semiconductor wafers, wherein the processing bath solution has a temperature of about 90°

C. during the processing of the subsequent batches of semiconductor wafers; and

(e) maintaining the rate of hydrogen peroxide addition to the processing bath solution during the processing of the subsequent batches of semiconductor wafers.

12. The method of claim 11 wherein the rate of addition of the hydrogen peroxide is from about 0.05 to about 0.7 g H₂ O₂ (anhydrous basis)/min./liter of the processing bath solution.