Radiation thermometer using off-focus telecentric optics

Patent metadata

Field	Value
Publication number	US-9448119-B2
Application number	US-201213531162-A
Country	US
Kind code	B2
Filing date	Jun 22, 2012
Priority date	Jun 22, 2012
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

A radiation thermometer utilizing an off-focus telecentric lens arrangement in chemical vapor deposition reactors. An object assembly of one or more optical components is positioned at a distance equal to its focal length from an aperture stop. The aperture stop is dimensioned so that the chief rays are substantially parallel with the optical axis of the object assembly, and so that the rays that pass through the aperture stop define a narrow solid angle about the chief rays. The off-focus telecentric arrangement thus configured is focused at infinity, but is utilized to capture radiation from a relatively proximate target (e.g., within a couple meters) that is out of focus. The capture of collimated radiation from the target diminishes the contribution of stray radiation, particularly with targets having a highly specular surface.

First claim

What is claimed is:

1. A metalorganic chemical vapor deposition system, comprising:
a telecentric optical arrangement for a radiation thermometer tailored to reduce the effects of stray radiation on a temperature measurement of a target, said telecentric optical arrangement including:
an aperture stop;
an object assembly of one or more optical components arranged for transfer of radiation to said aperture stop, said object assembly and said aperture stop defining an optical axis, said object assembly defining a first focal length relative to a first reference point within said object assembly, said first reference point being located on said optical axis at a distance from said aperture stop that is substantially equal to said first focal length of said object assembly for transfer of said radiation from said target through said object assembly and for focusing said radiation from said target onto said aperture stop, said object assembly disposed within a recess at a depth sufficient to limit the amount of stray radiation incident upon the object assembly; and
an electromagnetic radiation detector arranged to generate a signal representing said temperature measurement of said target from at least a portion of said radiation transferred from said object assembly through said aperture stop to said electromagnetic radiation detector;

said telecentric optical arrangement being mounted above a wafer carrier and oriented to view said target supported by a top surface of said wafer carrier at a distance such that said radiation transferred from said target to said object assembly is off-focus.

2. The metalorganic chemical vapor deposition system of claim 1 , further comprising an image assembly of one or optical components disposed opposite said object assembly from said aperture stop and arranged to receive radiation transferred from said object assembly through said aperture stop along said optical axis, said image assembly defining a second local length relative to a second reference point within said image assembly, said second reference point being located on said optical axis.

3. The metalorganic chemical vapor deposition system of claim 2 , wherein said second reference point of said image assembly is located at a distance from said aperture stop that is substantially equal to said second focal length of said image assembly.

4. The metalorganic chemical vapor deposition system of claim 1 , wherein said aperture stop defines a major dimension that is approximately ⅓ or less of an effective radial dimension of said object assembly.

5. The metalorganic chemical vapor deposition system of claim 1 , wherein said electromagnetic radiation detector is a photon counter having a cutoff wavelength of approximately 700 nm.

6. The metalorganic chemical vapor deposition system of claim 1 , further comprising a filtering device having a primary hand pass at wavelengths less than 450 nm, said filtering device being arranged to filter radiation incident on a sensing region of said electromagnetic radiation detector.

7. The metalorganic chemical vapor deposition system of claim 6 , wherein said primary band pass of said filtering device has a center wavelength in the range of 380 nm to 420 nm and has a band width in the range of 20 nm to 50 nm.

8. The metalorganic chemical vapor deposition system of claim 6 , wherein said filtering device comprises a band pass filter.

9. The metalorganic chemical vapor deposition system of claim 1 , wherein a distance between said target and said object assembly is less than two meters.

10. The metalorganic chemical vapor deposition system of claim 1 , wherein said object assembly comprises at least one lens.

11. A method of utilizing a telecentric lens arrangement for reducing stray radiation bias in a radiation thermometer to provide a temperature measurement of a target in a metalorganic chemical vapor deposition chamber, comprising:
providing a telecentric lens arrangement including an aperture stop and a first optical component assembly for collecting radiation from said target, said telecentric optical lens arrangement being mounted above a wafer carrier and oriented to view said target supported by a top surface of a wafer carrier at a distance such that said radiation transferred from said target to said object assembly is off-focus, said telecentric lens arrangement being adapted for positioning said aperture stop at the focal length of said first optical component assembly for capture of radiation emitted from said target, said object assembly disposed within a recess at a depth sufficient to limit the amount of stray radiation incident upon the object assembly;
providing instructions on a tangible medium, said instructions comprising:
orienting said first optical component assembly to intercept radiation emitted from a target within said metalorganic chemical vapor deposition chamber.

12. The method of claim 11 , wherein said instructions provided in the step of providing instructions further comprise positioning said aperture stop at the focal length of said first optical component assembly.

13. The method of claim 11 , wherein said instructions provided in the step of providing instructions further comprising operatively coupling said telecentric lens arrangement with an electromagnetic radiation detector.

14. The method of claim 11 , further comprising positioning said aperture stop at the focal length of said first optical component assembly.

15. The method of claim 11 , further comprising operatively coupling said telecentric lens arrangement with an electromagnetic radiation detector.

16. A system for measuring a temperature of a target in a metalorganic chemical vapor deposition chamber, comprising:
a radiation thermometer operatively coupled with said metalorganic chemical vapor deposition chamber above a wafer carrier and oriented to view said target supported by a top surface of said wafer carrier at a distance such that said radiation transferred from said target to an object assembly is off-focus, said object assembly disposed within a recess at a depth sufficient to limit the amount of stray radiation incident upon the object assembly, and said radiation thermometer including means for defining said target inside said chemical vapor deposition chamber.

17. The metalorganic chemical vapor deposition system of claim 1 , further comprising a light trap configured to limit transfer of stray radiation onto said target.

18. The metalorganic chemical vapor deposition system of claim 17 , wherein said optical axis of said object assembly is positioned at an angle with respect to a surface of said target, and wherein said light trap is positioned at an angle corresponding to the specular reflection of said target surface.

Assignees

• Tas Guray
• Zhou Jing
• Kwon Daewon
• Veeco Instr Inc

Inventors

• Tas Guray
• Zhou Jing
• Kwon Daewon

Classifications

• G01J5/0859

  Sighting arrangements, e.g. cameras · CPC title

• G01J5/0806

  Focusing or collimating elements, e.g. lenses or concave mirrors · CPC title

• G01J5/06

  Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity (for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801) · CPC title

• G01J5/0007

  of wafers or semiconductor substrates, e.g. using Rapid Thermal Processing · CPC title

• C23C16/44

  characterised by the method of coating (C23C16/04 takes precedence) · CPC title