Detection of wafer fragments in a wafer processing apparatus

• US 6,535,628 B2
• Filed: 10/15/1998
• Issued: 03/18/2003
• Est. Priority Date: 10/15/1998
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Ahmad, Wayez R., Smargiassi, Eugene
• Primary Examiner(s): WERNER, BRIAN P
• Application Number:
  US09/173,665
• Publication Number:
  US 20010043735A1
• Time in Patent Office: 1,615 Days
• Field of Search: 382/152, 382/141, 382/145, 382/149, 356/390, 356/394, 356/237.2, 356/237.3, 356/237.1, 356/237.4, 356/237.5, 250/559.05, 250/559.2, 250/559.39, 250/559.41, 250/559.46, 702/40, 702/82, 702/134, 438/7-9, 438/16, 148/215, 148/508, 427/99, 427/123, 427/124, 427/125, 348/82, 348/83, 348/86, 348/130, 348/87, 348/126
• US Class Current: 382/149
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/0008 checking presence/absence
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

During a wafer process, fragments can break away from a wafer. The wafer fragments can compromise the accuracy of the temperature signals generated by sensor probes in a rapid thermal process. In particular, the fragments can attenuate or otherwise interfere with the radiation received from the wafer. This interference can undermine the accuracy of the temperature measurement signal generated by the probes. If the temperature control function is compromised, excessive temperature gradients can result in damage to the wafer, reducing device yield and degrading device quality. To alleviate the effects of wafer fragments, the presence of a wafer fragment is detected. An image acquisition device acquires an image of an area adjacent the sensor probe. A processor analyzes the acquired image to determine whether a wafer fragment is present. One approach involves comparing the acquired image to a reference image taken in the absence of a wafer fragment quantifying the amount of deviation. Another approach involves analyzing the acquired image for optical density contrast changes indicative of the presence of a wafer fragment. Detection of a wafer fragment allows the rapid thermal process to be stopped so that the fragment can be cleared away, either manually or automatically, prior to insertion of the next wafer into the chamber.

Claims

1. A system for detecting the presence of a wafer fragment, which has broken away from a wafer during processing of the wafer in a deposition process chamber, the system comprising:

an image acquisition device disposed to acquire an image representative of a surface between a temperature sensing device and a wafer processing position within the deposition process chamber upon exit of the wafer from the deposition process chamber; and

a processor that analyzes the acquired image to detect the presence of the wafer fragment on the surface.

2. The system of claim 1, wherein the deposition process chamber is a rapid thermal process chamber.

3. The system of claim 2, wherein the rapid thermal process chamber includes a reflector plate, and the acquired image is representative of at least a portion of the reflector plate.

4. The system of claim 3, wherein the processor is configured to generate an advisory in the event the presence of a wafer fragment is detected.

5. The system of claim 4, wherein the processor is configured to compare the acquired image to a reference image, the processor generating the advisory in the event the acquired image deviates from the reference image by more than a threshold deviation representative of the presence of a wafer fragment.

6. The system of claim 5, wherein the threshold deviation is representative of the presence of a wafer fragment having a size that exceeds a threshold size.

7. The system of claim 5, wherein the act of comparing includes comparing the acquired image to the reference image on a pixel-by-pixel basis, and calculating an amount of the deviation based on differences between corresponding pixels in the acquired image and the reference image.

8. The system of claim 4, wherein the processor is configured to analyze the acquired image by identifying an optical density contrast change at a position within the imaged area, and determine whether a wafer fragment is present within the imaged area based on identification of the optical density contrast change.

9. The system of claim 4, wherein the processor is further configured to halt operation of the rapid thermal process chamber upon generation of the advisory.

10. The system of claim 3, wherein the chamber includes one or more temperature sensor probes disposed proximate the reflector plate, and the image acquisition device is oriented such that the acquired image is representative of at least a portion of the reflector plate proximate the temperature sensor probes within the rapid thermal process chamber, the acquired image being indicative of potential presence of a wafer fragment between the temperature sensor probes and the wafer processing position.

11. The system of claim 3, wherein the rapid thermal process chamber includes a viewport disposed laterally relative to the reflector plate, and the image acquisition device is oriented to acquire an image via the viewport that is representative of a perspective areal view of the reflector plate.

12. The system of claim 3, wherein the rapid thermal process chamber includes a lamp source, the system further comprising a controller that controls the lamp source to illuminate the reflector plate with radiation generated by the lamp source during the acquisition of the image.

13. A system for detecting the presence of a wafer fragment in a rapid thermal process chamber that includes a reflector plate, the system comprising:

an image acquisition device disposed to acquire an image representative of an area between a temperature sensing device and a wafer processing position within the deposition process chamber, wherein the acquired image is representative of at least a portion of the reflector plate;

and a processor that analyzes the acquired image to detect the presence of a wafer fragment within the area, wherein the processor is configured to drive the image acquisition device to generate a reference image by acquiring an image representative of at least a portion of the reflector plate at a time when the reflector plate is substantially free of wafer fragments, and is configured to compare the acquired image to a reference image, the processor generating an advisory in the event the presence of a wafer fragment is detected and the acquired image deviates from the reference image by more than a threshold deviation representative of the presence of a wafer fragment.

14. A rapid thermal processing system comprising:

a process chamber;

a wafer mount disposed within the process chamber;

a heat source disposed to heat a wafer in the wafer mount;

a reflector plate disposed on a side of the wafer mount opposite the heat source;

one or more temperature sensor probes disposed proximate to the reflector plate;

a viewport allowing visual access to the process chamber;

an image acquisition device disposed to acquire an image via the viewport, the image being representative of at least a portion of the reflector plate within the process chamber; and

a processor that analyzes the acquired image to detect the presence of a wafer fragment on the reflector plate.

15. The system of claim 14, wherein the processor is configured to generate an advisory in the event the presence of a wafer fragment is detected.

16. The system of claim 15, wherein the processor is configured to compare the acquired image to a reference image, the processor generating the advisory in the event the acquired image deviates from the reference image by more than a threshold deviation representative of the presence of a wafer fragment.

17. The system of claim 16, wherein the threshold deviation is representative of the presence of a wafer fragment having a size that exceeds a threshold size.

18. The system of claim 16, wherein the processor is configured to drive the image acquisition device to generate the reference image by acquiring an image representative of at least a portion of the reflector plate at a time when the reflector plate is substantially free of wafer fragments.

19. The system of claim 16, wherein the act of comparing includes comparing the acquired image to the reference image on a pixel-by-pixel basis, and calculating an amount of the deviation based on differences between corresponding pixels in the acquired image and the reference image.

20. The system of claim 15, wherein the processor is configured to analyze the acquired image by identifying an optical density contrast change at a position within the imaged area, and determine whether a wafer fragment is present within the imaged area based on identification of the optical density contrast change.

21. The system of claim 15, wherein the processor is further configured to halt operation of the process chamber upon generation of the advisory.

22. The system of claim 14, wherein the processor is further configured to control the image acquisition device to acquire the image following exit from the chamber of a wafer processed within the chamber.

23. The system of claim 14, wherein the image acquisition device is oriented to acquire an image via the viewport that is representative of a perspective areal view of the reflector plate.

24. The system of claim 14, wherein the rapid thermal process chamber includes a lamp source, the system further comprising a controller that controls the lamp source to illuminate the reflector plate with radiation generated by the lamp source during the acquisition of the image.

25. A method for detecting the presence of a wafer fragment, which has broken away from a wafer during processing of the wafer in a deposition process chamber, the method comprising:

acquiring an image representative of a surface between a temperature sensing device and a wafer processing position within the deposition process chamber upon exit of the wafer from the deposition process chamber; and

analyzing the acquired image to detect the presence of the wafer fragment on the surface.

26. The method of claim 25, wherein the deposition process chamber is a rapid thermal process chamber.

27. The method of claim 26, wherein the rapid thermal process chamber includes a reflector plate, and the image acquiring act includes acquiring an image representative of at least a portion of the reflector plate.

28. The method of claim 27, wherein the processor is configured to generate an advisory in the event the presence of a wafer fragment is detected.

29. The method of claim 28, further comprising analyzing the acquired image by comparing the acquired image to a reference image, and generating the advisory in the event the acquired image deviates from the reference image by more than a threshold deviation representative of the presence of a wafer fragment.

30. The method of claim 29, wherein the threshold deviation is representative of the presence of a wafer fragment having a size that exceeds a threshold size.

31. The method of claim 29, wherein the act of comparing includes comparing the acquired image to the reference image on a pixel-by-pixel basis, and calculating an amount of the deviation based on differences between corresponding pixels in the acquired image and the reference image.

32. The method of claim 28, further comprising analyzing the acquired image by identifying an optical density contrast change at a position on a surface of the reflector plate, and determining whether a wafer fragment is present on the reflector plate based on identification of the optical density contrast change.

33. The method of claim 28, further comprising halting operation of the rapid thermal process chamber in response to generation of the advisory.

34. The method of claim 27, wherein the chamber includes one or more temperature sensor probes disposed proximate the reflector plate, and the act of acquiring the image includes acquiring an image representative of at least a portion of the reflector plate, the acquired image being indicative of potential presence of a wafer fragment between the temperature sensor probes and the wafer processing position.

35. The method of claim 27, wherein the rapid thermal process chamber includes a viewport disposed laterally relative to the reflector plate, and the act of acquiring the image includes acquiring a perspective areal view image of the reflector plate via the viewport.

36. The method of claim 27, wherein the rapid thermal process chamber includes a lamp source that generates radiation to heat the chamber, the method further comprising illuminating the reflector plate with the radiation generated by the lamp source during the acquisition of the image.

37. A method for detecting the presence of a wafer fragment in a rapid thermal process chamber that includes a reflector plate, the method comprising:

generating a reference image by acquiring an image representative of at least a portion of the reflector plate at a time when the reflector plate is substantially free of wafer fragments;

acquiring an image representative of an area between a temperature sensing device and a wafer processing position within the rapid thermal process chamber, wherein the acquired image is representative of at least a portion of the reflector plate; and

analyzing the acquired image to detect the presence of a wafer fragment within the area by comparing the acquired image to the reference image; and

generating an advisory in the event the presence of a wafer fragment is detected and the acquired image deviates from the reference image by more than a threshold deviation representative of the presence of a wafer fragment.