Bandpass photon detector

• US 5,995,235 A
• Filed: 02/13/1997
• Issued: 11/30/1999
• Est. Priority Date: 02/13/1997
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Sui, Zhifeng, Luscher, Paul E.
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): SMITH, ZANDRA V
• Application Number:
  US08/800,003
• Time in Patent Office: 1,020 Days
• Field of Search: 356/315, 356/317, 356/318, 356/416, 356/417, 356/419, 356/311, 250/226
• US Class Current: 356/419
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/71 thermally excited
• CPC Class Codes: G02B 6/29362 Serial cascade of filters or filtering operations, e.g. for a large number of channels

Abstract

Apparatus for bandpass photon detection containing a lens for collimating input light, a bandpass filter element, and a photomultiplier detector. Light passes from a source into the lens which collimates the light which then is incident upon the filter. The filter is tuned to a particular band of wavelengths, such that out of all of the wavelengths that are incident upon the front side of the filter, a wavelength band is propagated through the filter and passes from the filter to the photomultiplier detector, such that the output of the photomultiplier detector is a voltage level representing the energy content within that wavelength band. In various alternative embodiments, the bandpass photon detectors are arranged in a number of cascade arrangements such that multiple wavelength bands are simultaneously detected.

Claims

1. A system for measuring a plurality of bands of wavelengths of an optical signal, said system comprising:

a plurality of bandpass photon detectors, arranged in a cascade pattern, for detecting respectively different bands of wavelengths, where each bandpass photon detector comprises;

a filter element for transmitting a predefined band of wavelengths of the optical signal and reflecting other predefined wavelengths of the optical signal; and

an optical signal detector, optically coupled directly to said filter element, for generating a voltage that represents the energy in the predefined band of wavelengths that is transmitted by the filter element;

where at least one of said filter elements is aligned to transmit a predefined band of wavelengths of the optical signal directly to an optical signal detector and reflect other predefined wavelengths of the optical signal to at least one other of the bandpass photon detectors; and

a monochromator detector, coupled to a last bandpass photon detector in said cascade pattern, for selecting a band of wavelengths from a remaining optical signal for detection.

2. The system of claim 1 further comprising a spectrum analyzer, coupled to selected ones of said plurality of bandpass photon detectors, for combining and analyzing a plurality of the predefined bands of wavelength.

3. The system of claim 1 wherein the cascade pattern of bandpass photon detectors is formed by positioning a plurality of bandpass photon detectors equidistant from a central point and having each of the filter elements in the bandpass photon detectors substantially facing the central point.

4. The system of claim 1 wherein each of said filter elements has a surface and the optical signal has an angle of incidence upon the surface of the filter element to cause said predefined band of wavelengths of the optical signal to propagate through said filter element and cause said other predefined band of wavelengths of the optical signal to be reflected toward said other bandpass photon detector.

5. The system of claim 1 wherein the plurality of bandpass photon detectors comprises N bandpass photon detectors, where N is an integer, and each of the N bandpass photon detectors is arranged in said cascade pattern to cause a reflected optical signal to be incident upon another one of the bandpass photon detectors or a termination.

6. The system of claim 1 wherein said predefined band of wavelengths has a bandwidth of approximately 2 nm.

7. A system for measuring a plurality of bands of wavelengths of an optical signal, said system comprising:

a plurality of bandpass photon detectors, arranged in a cascade pattern formed by positioning the plurality of bandpass photon detectors equidistant from a central point and having each of the bandpass photon detectors substantially facing the central point and aligned to cause a reflected optical signal to be incident upon another one of the bandpass photon detectors or a termination, where each of the bandpass photon detectors measures a predefined band of wavelengths of the optical signal and reflects other bands of wavelengths of the optical signal.

8. The system of claim 7 wherein each of the bandpass photon detectors comprises:

a filter element for transmitting said predefined band of wavelengths of the optical signal and reflecting said other predefined wavelengths of the optical signal; and

an optical signal detector, optically coupled to said filter element, for generating a voltage that represents the energy in the predefined band of wavelengths that is transmitted by the filter element.

9. A system for measuring a plurality of bands of wavelengths of an optical signal produced by a plasma within a semiconductor wafer processing chamber, said system comprising:

a plurality of bandpass photon detectors for detecting a respectively different bands of wavelengths, where each bandpass photon detector comprises;

a first filter element for transmitting a predefined band of wavelengths of the optical signal and reflecting other predefined wavelengths of the optical signal; and

an optical signal detector, optically coupled to said first filter element, for generating a voltage that represents the energy in the predefined band of wavelengths that is transmitted by the first filter element; and

an optical signal distributor having a plurality of second filter elements that reflect certain wavelengths of said optical signal and transmit certain wavelengths of said optical signal, where said second filter elements are arranged in series and each second filter element is associated with a bandpass photon detector that is aligned with said associated second filter element to receive an optical signal that is reflected from said associated second filter element.

10. The system of claim 9 wherein said second filter elements are a plurality of low pass filter elements.

11. The system of claim 9 wherein said second filter elements are a plurality of high pass filter elements.

12. The system of claim 9 further comprising a spectrum analyzer, coupled to selected ones of said plurality of bandpass photon detectors, for combining and analyzing a plurality of the predefined bands of wavelength.