Methods for detecting the endpoint of a photoresist stripping process

• US 20020148811A1
• Filed: 06/05/2002
• Published: 10/17/2002
• Est. Priority Date: 12/21/1999
• Status: Active Grant

• Current Assignee: Tuqiang Ni, Wenli Collision
• Original Assignee: Tuqiang Ni, Wenli Collision
• Inventors: Collision, Wenli, Ni, Tuqiang
• Granted Patent: US 7,077,971 B2
• Time in Patent Office: Days
• US Class Current: 216/59
• CPC Class Codes: H01J 2237/3342 Resist stripping
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32963 End-point detection

Abstract

Methods for detecting the endpoint of a photoresist stripping process provide O for reaction with the photoresist for a wafer to be stripped of photoresist. NO is also supplied for reaction with O not reacted with the photoresist. After substantially all the photoresist is stripped from the wafer, the rate of a reaction of O and NO to form NO₂ increases, which increases the intensity of emitted light. An operation of detecting this increase in light intensity signals the endpoint of the photoresist stripping process.

Claims

1. A method for detecting an endpoint of a photoresist stripping process, the method comprising the operations of:

stripping photoresist from a wafer disposed inside a chamber;

detecting an intensity of light emitted; and

using a change in the intensity of light emitted to detect the endpoint of the photoresist stripping process.

2. A method as recited in claim 1, wherein the chamber contains substantially no plasma.

3. A method as recited in claim 1, further comprising the operation of:

introducing a flow of O and a flow of NO into the chamber.

4. A method as recited in claim 3, wherein the emitted light is emitted in a reaction of NO and O to form NO₂.

5. A method as recited in claim 3, wherein the O reacts with the photoresist to strip the photoresist from the wafer.

6. A method as recited in claim 3, wherein the operation of detecting a change in the intensity of light emitted further comprises detecting an increase in the intensity of light emitted from a reaction of NO and O.

7. A method as recited in claim 6, wherein the increase in intensity of the light emitted from the reaction of NO and O signals the endpoint of the photoresist stripping process.

8. A method as recited in claim 6, wherein the emitted light detected is in the wavelength range of about 470 nm to about 770 nm.

9. A method as recited in claim 6, wherein a wall of the chamber includes a window, the intensity of the light emitted being detected through the window by a light detecting apparatus.

10. A method as recited in claim 1, further comprising the operations of:

introducing a flow of O into the chamber;

providing an outlet from the chamber;

providing a downstream channel, the downstream channel being in fluid communication with the chamber outlet;

introducing a flow of NO into the downstream channel; and

detecting an increase in intensity of the light emitted from a reaction of NO and O, wherein the increase in intensity of the light emitted from the reaction of NO and O signals the endpoint of the photoresist stripping process.

11. A method as recited in claim 10, wherein a wall of the downstream channel includes a window, the intensity of the light emitted being detected through the window by a light detecting apparatus.

13. A method as recited in claim 12, further comprising the operation of introducing a flow of NO into the chamber through the first inlet, wherein an increase in the intensity of light emitted from the reaction of NO and O to form NO₂ signals the endpoint of the photoresist stripping process.

14. A method as recited in claim 13, wherein a wall of the chamber includes a window, the intensity of the light emitted being detected through the window by a light detecting apparatus.

15. A method as recited in claim 12, further comprising the operation of introducing a flow of NO into the chamber through a second inlet, wherein an increase in the intensity of light emitted from the reaction of NO and O to form NO₂ signals the endpoint of the photoresist stripping process.

16. A method as recited in claim 15, wherein a wall of the chamber includes a window near the second inlet, the intensity of the light emitted being detected through the window by a light detecting apparatus.

17. A method as recited in claim 12, further comprising the operation of introducing a flow of NO into a downstream channel in fluid communication with the chamber outlet and wherein an increase in the intensity of light emitted from the reaction of NO and O to form NO₂ signals the endpoint of the photoresist stripping process.

18. A method as recited in claim 17, wherein a wall of the downstream channel includes a window, the intensity of the light emitted being detected through the window by a light detecting apparatus.

20. A method as recited in claim 19, further comprising the operation of:

dissociating O₂ to supply the first gas for the first reaction.

21. A method as recited in claim 19, further comprising the operation of:

collecting the first gas that was supplied to the stripping chamber and that did not react with the photoresist; and

supplying the second gas to the collected first gas to facilitate performing the second reaction.

22. A method as recited in claim 21, wherein:

the operation of supplying the second gas to facilitate performing the second reaction also emits a range of wavelengths of the second light; and

the detecting operation detects the intensities of all of the wavelengths of the range to provide the indication as to when to stop the stripping process.

24. A method as recited in claim 23, further comprising the operations of:

dissociating O₂ to form the O for the first reaction.

25. An apparatus as recited in claim 23, further comprising the operations of:

separately from the first reaction, receiving the O supplied for the first reaction and not reacted with the photoresist; and

supplying the NO to the received O supplied for the first reaction and not reacted with the photoresist to facilitate, separately from the first reaction, the end point detection process between the NO and the O supplied to the stripping chamber and not reacted with the photoresist.

26. An apparatus as recited in claim 23, wherein:

the end point detection process emits the second light having a range of wavelengths; and

the detecting operation detects the intensities of all of the wavelengths of the range to provide the indication of the endpoint.

12. A method for monitoring a photoresist stripping process, comprising the operations of:

providing a stripping chamber with a first inlet and an outlet;

providing a wafer at least partially coated with a photoresist layer;

providing a detecting apparatus operable to detect an intensity of light emitted from a reaction of NO and O to form NO₂;

disposing the wafer within the stripping chamber;

introducing a flow of O into the stripping chamber through the first inlet, wherein the O reacts with the photoresist layer to strip the photoresist layer from the wafer;

detecting a change in the intensity of light emitted from the reaction of NO and O to form NO₂ with the detecting apparatus; and

using the change in intensity of light emitted from the reaction of NO and O to form NO₂ to monitor the photoresist stripping process.

19. A method for detecting an endpoint in a process of stripping photoresist from a wafer, the method comprising the operations of:

performing a first reaction of a first gas and the photoresist to strip the photoresist from the wafer, the first reaction emitting first light having a first intensity;

performing a second reaction between a second gas and the first gas supplied for the first reaction and not reacted with the photoresist, upon completion of the first reaction the second reaction emitting second light having a second intensity that differs substantially from the first intensity; and

detecting the intensities of the first and second lights to provide an indication as to when to stop the stripping process.

23. A method for detecting an endpoint in a process of stripping photoresist from a wafer, the method comprising the operations of:

performing the stripping process by a first reaction of O and the photoresist to strip the photoresist from the wafer, first light having a first intensity being emitted during the first reaction;

supplying NO to facilitate an end point detection process between the O supplied to the stripping chamber and not reacted with the photoresist and the NO, upon completion of the first reaction the end point detection process emitting second light having a second intensity that differs substantially from the first intensity; and

detecting the intensities of the first light and the second light to provide an indication of the endpoint.