Method for fabricating an infrared radiation detector

Details Method for fabricating an infrared radiation detector Method for fabricating an infrared radiation detector

1989-11-22

2001-03-06

Hellner, Mark (Department: 3662)

Radiant energy

Invisible radiant energy responsive electric signalling

Infrared responsive

Reexamination Certificate

active

06198100

ABSTRACT:

FIELD OF THE INVENTION
The present invention pertains in general to radiation detectors and in particular to the fabrication of such detectors which operate at short wavelengths, such as in the infrared region.
BACKGROUND OF THE INVENTION
Infrared radiation detectors have long been used for producing thermal images which makes it possible to observe scenes at night or through clouds, smoke and dust. A conventional infrared detector is a large scale device, that is, each detector element is much larger than the wavelength of the incident radiation. Such conventional detector elements are purposely designed to be relatively large in order to insure that there is an adequate collection area for the incident radiation. Further, such detectors are made relatively thick to absorb penetrating incident radiation.
A principal limitation in the use of conventional infrared detectors has been the requirement that the detectors be enclosed within a cold chamber. The cooling is required to raise the detectivity of the detector to a usable level. Such cooling is typically provided by the evaporation of liquid gases, such as nitrogen. However, the storage, piping and handling of coolants such as liquid nitrogen is a difficult, expensive and time consuming task. Conventional large area detectors further have relatively low detectivity which reduces the sensitivity of the detector system.
In view of the need for thermal imaging and the difficulties associated with the use of such infrared detectors, such as cooling and low detectivity there exist a need for an infrared detector which has a much higher detectivity and, as a result, can produce a useful signal at ambient temperature thereby eliminating or reducing the need for cooling equipment.
SUMMARY OF THE INVENTION
A selected embodiment of the present invention is a method for fabricating a device for detecting infrared radiation. In a first step, a plurality of groups of photosensitive segments are formed in a planar array. These segments are sensitive to the infrared radiation and have a thickness which is less than the wavelength of the infrared radiation. The photosensitive segments in each group are preferably offset from each other by less than the wavelength of the radiation. Further, the lateral dimension of each of the photosensitive segments is less than the radiation wavelength. A plurality of electrically conductive segments are formed for interconnecting adjacent ones of the photosensitive segments in each of the groups. The electrically conductive segments are not photosensitive to the infrared radiation to be detected. Each group of the photosensitive segments together with the corresponding conductive segments is electrically conductive along its length. A plane is formed which is reflective to the infrared radiation. The reflective plane is offset from the planar array of photosensitive segments by an insulating layer which has a thickness that is less than the wavelength of the infrared radiation. Conducting lines are formed for electrically connecting in parallel the plurality of groups of photosensitive elements to provide a conduction path for detection signals produced by the photosensitive segments in response to the incident infrared radiation.


REFERENCES:
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patent: 4639756 (1987-01-01), Rosbeck et al.
patent: 4731640 (1988-03-01), Bluzer
patent: 4875084 (1989-10-01), Tohyama

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