Ozone concentration sensor

• US 7,502,114 B2
• Filed: 03/12/2004
• Issued: 03/10/2009
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Lohr, Joachim, Brammer, Ulrich, Fittkau, Jens, Seiwert, Johannes, Levine, Stephan
• Primary Examiner(s): Chowdhury; Tarifur R.
• Assistant Examiner(s): Akanbi; Isiaka O
• Application Number:
  US10/799,331
• Publication Number:
  US 20050200848A1
• Time in Patent Office: 1,824 Days
• Field of Search: 356/407, 356409-411, 356432-442, 356445-448
• US Class Current: 356/432
• CPC Class Codes: G01N 2021/3181 using LEDs
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

An apparatus and method provide measurement of a constituent of a fluid, such as ozone in ozonated water. The apparatus includes a vessel to contain the fluid, a light source configured to direct a first band of light and a second band of light along a substantially shared path though the fluid, and a photosensor that senses the first band of light and the second band of light. The constituent has a greater absorption associated with the first band of light than with the second band of light. The method includes modification of a measured attribute of the component in response to the sensed second band of light to improve the accuracy of the measured attribute.

Claims

1. An apparatus for measuring an attribute of ozone, the apparatus comprising:

a delivery pipeline to contain ozonated water for delivery to a semiconductor process tool, the delivery pipeline including a plurality of reflection sites;

a light source configured to direct a first band of visible light and a second band of visible light along a substantially shared path through the ozonated water in the delivery pipeline, the first and second bands of visible light diffusely scattered by the plurality of reflection sites, wherein ozone in the ozonated water has a greater absorption associated with the first band of visible light than with the second band of visible light; and

a photosensor that senses the first band of visible light and the second band of visible light passing along the substantially shared path for measuring the attribute of the ozone in the ozonated water.

2. The apparatus of claim 1, wherein the delivery pipeline permits in situ measurement of the ozone in the ozonated water during delivery of the ozonated water to the semiconductor process tool.

3. The apparatus of claim 1, wherein the first band of visible light is associated with a yellow-red frequency and a first width, and the second band of visible light is associated with a blue frequency and a second width.

4. The apparatus of claim 3, wherein the light source comprises a yellow-red light-emitting diode to provide the first band of visible light, and a blue light-emitting diode to provide the second band of visible light.

5. The apparatus of claim 4, further comprising a second photosensor that senses the first band of visible light and the second band of visible light after they pass along at most a portion of the substantially shared path to detect differential aging of the light-emitting diodes.

6. The apparatus of claim 1, wherein the substantially shared path is defined in part by the plurality of reflection sites to increase a length of the path through the ozonated water in the delivery pipeline, thereby increasing a measurement sensitivity for the attribute of the ozone in the ozonated water.

7. The apparatus of claim 1, wherein the delivery pipeline comprises a material that defines an inner surface of the delivery pipeline for diffusely scattering the first and second bands of visible light at the plurality of reflection sites.

8. The apparatus of claim 1, further comprising a coating on an exterior surface of the delivery pipeline for diffusely scattering the first and second bands of visible light at the plurality of reflection sites.

9. The apparatus of claim 1, wherein the attribute of the ozone in the ozonated water has an absorption band that overlaps the first band of visible light.

10. The apparatus of claim 1, wherein the light source comprises a light-emitting diode.

11. The apparatus of claim 1, wherein the delivery pipeline comprises a material selected from the group of quartz and a polymer.

12. The apparatus of claim 1, wherein the photosensor senses the first band of visible light and the second band of visible light after the first band of visible light and the second band of visible light pass along the substantially shared path.

13. The apparatus of claim 1, wherein the photosensor senses the first band of visible light and the second band of visible light as the first band of visible light and the second band of visible light pass along a portion of the substantially shared path.

14. The apparatus of claim 1, further comprising a temperature sensor, for measuring a temperature of the ozonated water in the delivery pipeline.

15. The apparatus of claim 1 wherein the attribute is ozone concentration.

16. The apparatus of claim 1 wherein the attribute is absorption of the first or second bands of visible light by the ozone.

17. The apparatus of claim 1, wherein the plurality of reflection sites affects an amount of diffuse scattering of the first or second bands of visible light.

18. The apparatus of claim 1, wherein the photosensor is positioned along the substantially shared path for sensing the first and second bands of visible light as the first and second bands of visible light pass through the delivery pipeline.

19. The apparatus of claim 1, further comprising a second photosensor positioned along a longitudinal axis defined by an external surface of the delivery pipeline for sensing the first band of visible light and the second band of visible light passing along the substantially shared path prior to the first and second bands of visible light reaching the photosensor.

20. The apparatus of claim 1, wherein an interior surface of the delivery pipeline or an exterior surface of the delivery pipeline comprises a material to facilitate diffuse scattering of the first or second bands of visible light.

21. The apparatus of claim 20, wherein the material is a coating.

22. The apparatus of claim 1, wherein the plurality of reflection sites facilitates a diffuse reflection by the first and second bands of visible light within the delivery pipeline.

23. An ozonated water generator, comprising:

a contactor for mixing water and ozone gas to produce ozonated water;

a delivery pipeline in fluid communication with the contactor for delivery of ozonated water to a semiconductor process tool, the delivery pipeline including a plurality of reflection sites;

a light source configured to direct a first band of visible light and a second band of visible light along a substantially shared path though the ozonated water in the delivery pipeline, the first and second bands of visible light diffusely scattered at the plurality of reflection sites in the delivery pipeline, wherein ozone in the ozonated water has a greater absorption associated with the first band of visible light than with the second band of visible light; and

a photosensor that senses the first band of visible light and the second band of visible light after they pass along the substantially shared path for measuring an attribute of the ozone in the ozonated water.

24. A method for measuring an attribute of ozone in an ozonated water, the method comprising:

selecting a first band of visible light for which ozone has a greater absorption than for a second band of visible light;

directing the first and second bands of visible light thru a delivery pipeline to diffusely scatter the first and second bands of light at a plurality of reflection sites of the delivery pipeline;

sensing the first band of visible light and the second band of visible light after they pass along a substantially shared path through the ozonated water; and

modifying a measured attribute of the ozone in the ozonated water determined from the sensed first band of visible light in response to the sensed second band of visible light to improve the accuracy of the measured attribute.

25. The method of claim 24, wherein modifying comprises correcting the measured attribute for an intensity loss of the sensed first band of visible light associated with at least one factor other than absorption by the attribute of the ozone in the ozonated water.

26. The method of claim 25, wherein the at least one factor comprises at least one of bubbles, a reflectivity of a reflection site of the substantially shared path, an impurity in the ozonated water, and a mechanical dimension of delivery pipeline containing the ozonated water.

27. The method of claim 24, further comprising providing the substantially shared path in the delivery pipeline defined at least in part by the first and second bands of visible light being diffusely reflected at the plurality of reflection sites.

28. The method of claim 27, wherein the plurality of reflection sites increase a length of the substantially shared path in the delivery pipeline.

29. The method of claim 27, further comprising causing the ozonated water to flow through the delivery pipeline from an ozonated water generator to a semiconductor process tool to permit in situ measurement of the ozone concentration in the delivery pipeline.

30. The method of claim 29, wherein alternately directing further comprises alternately directing no light along the substantially shared path.

31. The method of claim 29, further comprising sensing at least one of the first band of visible light and the second band of visible light along after the first and second bands of visible light have passed at most a portion of the substantially shared path, and responsively maintaining an emitted intensity of at least one of the first band of visible light and the second band of visible light.

32. The method of claim 24, further comprising alternately directing the first band of visible light and the second band of visible light along the substantially shared path, wherein sensing comprises alternately sensing the first band of visible light and the second band of visible light.

33. A method for producing ozonated water having a desired ozone concentration, the method comprising:

selecting a first band of visible light for which the ozone has a greater absorption than for a second band of visible light;

generating ozonated water in a ozonated water generation device;

sensing the first band of visible light and the second band of visible light after the first and second bands of visible light are diffusely scattered at a plurality of reflection sites and pass along a substantially shared path defined in part by diffuse scattering at the plurality of reflection sites through the ozonated water after the ozonated water flows from the ozonated water generation device towards a semiconductor process tool;

modifying a measured ozone concentration determined from the sensed first band of visible light in response to the sensed second band of visible light to improve the accuracy of the measured ozone concentration; and

adjusting at least one parameter of the ozone water generation device until the measured ozone concentration of the ozonated water substantially matches the desired ozone concentration.

34. An apparatus for measuring an attribute of an ozonated water, the apparatus comprising:

a delivery pipeline to contain the ozonated water, the delivery pipeline defining a first end, a second end, a plurality of reflection sites, an interior surface, and an exterior surface, the interior surface and the exterior surface extending from the first end to the second end;

a light source to direct a first band of visible light and a second band of visible light along a substantially shared path through the delivery pipeline defined in part by the plurality of reflection sites, wherein ozone in the ozonated water has a greater absorption associated with the first band of visible light than with the second band of visible light and the interior surface or the exterior surface facilitates diffuse scattering of the first and second bands of visible light at the plurality of reflection sites and;

a photosensor positioned relative to the interior surface or exterior surface of the delivery pipeline for sensing the first and second bands of visible light passing along the substantially shared path to measure the attribute of the ozonated water.

35. The apparatus of claim 34, wherein the plurality of reflection sites increases a length of the substantially shared path relative to a length of the interior surface or exterior surface of the delivery pipeline.

36. An apparatus for measuring an attribute of ozone, the apparatus comprising:

a delivery pipeline to carry ozonated water from an ozonated water generator to a semiconductor process tool;

a light source configured to direct a first band of visible light and a second band of visible light through the ozonated water in the delivery pipeline, wherein ozone in the ozonated water has a greater absorption with the first band of visible light than with the second band of visible light; and

a photosensor that senses the first band of visible light and the second band of visible light passing along a path for measuring an attribute of the ozone in the ozonated water.

37. The apparatus of claim 36, wherein the delivery pipeline permits in situ measurement of an attribute of ozone in the ozonated water during delivery of the ozonated water to the semiconductor process tool.