Apparatus and method for determining the temperature of a radiating surface

• US 5,874,711 A
• Filed: 04/17/1997
• Issued: 02/23/1999
• Est. Priority Date: 04/17/1997
• Status: Expired due to Term

• Current Assignee: STEAG RTP Systems, Inc. (KSBG Kommunale Beteiligungsgesellschaft GmbH & Company KG)
• Original Assignee: AG Associates Incorporated (KSBG Kommunale Beteiligungsgesellschaft GmbH & Company KG)
• Inventors: Man, Avner, Fabian, Ram Z., Gat, Arnon, Champetier, Robert J.
• Primary Examiner(s): Paschall, Mark H.
• Application Number:
  US08/843,925
• Time in Patent Office: 677 Days
• Field of Search: 219/497, 219/501, 219/505, 219/502, 219/121.43, 219/494, 118/724, 356/43-45, 359/350, 359/359, 392/416, 392/418
• US Class Current: 219/497
• CPC Class Codes: G01J 5/0003 for sensing the radiant heat transfer of samples, e.g. emittance meter

Abstract

The present invention is generally directed to a system and process for accurately determining the temperature of an object, such as a semiconductive wafer, by sampling from the object radiation being emitted at a particular wavelength. In particular, a reflective device is placed adjacent to the radiating object. The reflective device includes areas of high reflectivity and areas of low reflectivity. The radiation being emitted by the object is sampled within both locations generating two different sets of radiation measurements. The measurements are then analyzed and a correction factor is computed based on the optical characteristics of the reflective device and the optical characteristics of the wafer. The correction factor is then used to more accurately determine the temperature of the wafer. Through this method, the emissivity of the wafer has only a minor influence on the calculated temperature.

Claims

1. An apparatus for measuring the temperature of an object comprising:

a chamber adapted to receive an object;

a reflective device contained within said chamber, said reflective device being positioned so as to be placed adjacent to an object when said object is received within said chamber, said reflective device being configured to reflect thermal radiation being emitted by said object between a surface of said object and a surface of said device, said reflective device including at least a first areas a second area, and a third area, said first area having a greater reflectivity than said second area and said third area; and

a radiation sensing device for sensing said reflected thermal radiation at a plurality of locations, said radiation sensing device sensing said thermal radiation within said first area, within said second area, and within said third area of said reflective device for determining the temperature of said object.

2. An apparatus as defined in claim 1, further comprising a heat source in communication with said chamber for heating objects contained within said chamber, said heat source comprising at least one lamp.

3. An apparatus as defined in claim 2, further comprising a filter positioned between said heat source and said chamber for substantially preventing light at a preselected wavelength from entering said chamber.

4. An apparatus as defined in claim 3, wherein said radiation sensing device senses said thermal radiation at said preselected wavelength.

5. An apparatus as defined in claim 4, further comprising a controller in communication with said radiation sensing device and with said heat source, said controller being configured to receive thermal radiation information from said radiation sensing device and, based on said information, to control the amount of heat being emitted by said heat source.

6. An apparatus as defined in claim 1, wherein said reflective device comprises a substrate coated within said first area with a first dielectric film and coated with at least a second dielectric film within said second area and said third area.

7. An apparatus as defined in claim 1, wherein said reflective device comprises a substrate coated with a dielectric film, and wherein said second area is defined by an opening located within said film.

8. An apparatus as defined in claim 1, wherein said first area of said reflective device comprises a plate having a highly reflective surface, and wherein said second area of said reflective device is created by placing a partial light transmitting mirror over a portion of said reflective surface.

9. An apparatus as defined in claim 1, wherein said second area and said third area are smaller in size than said first area of said reflective device.

10. An apparatus as defined in claim 9, wherein said reflective device further includes a fourth area having a reflectivity lower than said first area, said fourth area being smaller in size than said first area of said reflective device, said radiation sensing device sensing said thermal radiation within said fourth area for determining the temperature of said object.

11. An apparatus as defined in claim 1, wherein said reflective device includes at least five distinct areas having a reflectivity lower than said first area, said radiation sensing device sensing said thermal radiation at each of said five areas for determining the temperature of said object.

13. An apparatus as defined in claim 10, wherein said reflective surface has a reflectivity of greater than 0.9 and wherein said at least two areas have a reflectivity of from about 0.2 to about 0.7.

12. An apparatus for measuring the temperature of a semiconductor wafer comprising:

a chamber adapted to receive said semiconductor wafer;

a heat source in communication with said chamber for heating said semiconductor wafer when contained therein;

a reflective device positioned within said chamber, said reflective device including a reflective surface being spaced a predetermined distance from said wafer, said reflective surface being configured to reflect thermal radiation being emitted by said wafer between a surface of said wafer and said reflective surface, said reflective surface including at least two areas having a reflectivity lower than the remainder of said reflective surface; and

a radiation sensing device for sensing said thermal radiation being emitted by said semiconductor wafer at a plurality of locations, said radiation sensing device sensing said thermal radiation within said at least two areas and outside said at least two areas upon said reflective surface, wherein said thermal radiation being sensed at said plurality of locations is used to determine the temperature of said wafer.

14. An apparatus as defined in claim 12, wherein said heat source comprises at least one lamp and wherein said apparatus further includes a filter positioned between said heat source and said chamber for substantially preventing light at a preselected wavelength from entering said chamber, said radiation sensing device sensing thermal radiation at said preselected wavelength.

15. An apparatus as defined in claim 14, wherein said filter comprises a quartz window for substantially preventing light from entering said chamber at a wavelength of from about 2.7 microns to about 2.8 microns.

16. An apparatus as defined in claim 14, further comprising a controller in communication with said radiation sensing device and with said heat source, said controller receiving thermal radiation information sensed by said radiation sensing device for determining the temperature of said wafer, said controller, based on said determined temperature, controlling the amount of heat being emitted by said heat source.

17. An apparatus as defined in claim 12, wherein said radiation sensing device comprises a plurality of pyrometers.

18. An apparatus as defined in claim 12, wherein said reflective surface of said reflective device comprises a first multi-layer dielectric film defining said at least two areas and a second multi-layer dielectric film defining the remainder of said reflective surface.

19. An apparatus for measuring and controlling the temperature of a semiconductor wafer comprising:

a chamber adapted to received said semiconductor wafer;

a heat source in communication with said chamber for heating said semiconductor wafer when contained therein;

a filter position between said heat source and said chamber for substantially preventing light at a preselected wavelength from entering said chamber;

a reflective device positioned within said chamber, said reflective device including a reflective surface being spaced a predetermined distance from said wafer, said reflective surface being configured to reflect thermal radiation being emitted by said wafer between a surface of said wafer and said reflective surface, said reflective surface including at least a first area, a second area and a third area, said second area and said third area having a reflectivity lower than said first area of said reflective surface;

a radiation sensing device for sensing said thermal radiation being emitted by said semiconductor wafer at said preselected wavelength, said radiation sensing device sensing said thermal radiation within at least said first area, within said second area, and within said third area upon said reflective surface; and

a controller in communication with said radiation sensing device and with said heat source, said controller receiving thermal radiation information sensed by said radiation sensing device for determining the temperature of said wafer, said controller, based on said determined temperature, controlling the amount of heat being emitted by said heat source.

20. An apparatus as defined in claim 19, wherein said reflective surface of said reflective device is substantially parallel to said surface of said wafer.

21. An apparatus as defined in claim 19, wherein said filter comprises a quartz window for preventing light from entering said chamber at a wavelength of from about 2.7 micrometers to about 2.8 micrometers.

22. An apparatus as defined in claim 19, wherein said radiation sensing device comprises a plurality of pyrometers and wherein said reflective device comprises a substrate coated with a first dielectric film within said first area and at least a second dielectric film within said second area and said third area on said reflective surface, said first dielectric film having a reflectivity of greater than 0.9 and said second dielectric film having a reflectivity of from about 0.2 to about 0.7.

23. An apparatus as defined in claim 19, wherein said second area and said third area of said reflective surface comprise low reflective zones surrounded by said first area, said second area and said third area being smaller than said first area.

24. A method for measuring the temperature of a radiating body comprising the steps of:

providing a radiating body;

positioning a reflective device adjacent to a surface of said radiating body, said reflective device including a reflective surface facing said surface of said radiating body, said reflective surface including a first area having a first reflectivity, a second area having a second reflectivity, and a third area having a third reflectivity said first reflectivity being greater than said second reflectivity and said third reflectivity, said reflective surface causing thermal radiation being emitted by said radiating body to reflect between said surface of said radiating body and said reflective surface; and

sensing the thermal radiation being emitted by said radiating body within said first area, within said second area and within said third area for determining the temperature of said radiating body.

25. A method as defined in claim 24, wherein said thermal radiation being emitted by said radiating body is sensed at a preselected wavelength.

26. A method as defined in claim 24, wherein said second area and said third area of said reflective surface are smaller in size then said first area.

27. A method as defined in claim 24, wherein said first area of said reflective surface has a reflectivity greater then 0.9 and wherein said second area and said third area of said reflective surface have a reflectivity of from about 0.2 to about 0.7.

28. A method as defined in claim 24, wherein said reflective device comprises a substrate coated within said first area by a first dielectric film and coated within said second area by a second dielectric film.

29. A method as defined in claim 26, wherein said reflective surface further comprises a fourth area having a reflectivity lower than said reflectivity of said first area, said fourth area being smaller in size than said first area, wherein the thermal radiation being emitted by said radiating body is also sensed within said fourth area for determining the temperature of said radiating body.