Low power infrared scene projector array and method of manufacture
First Claim
1. An apparatus for emitting a wide-band infrared image, comprising:
- a semiconductor substrate having a plurality of cavities therein;
address means disposed on the substrate proximate the plurality of cavities for routing electrical signals to various portions of the substrate, wherein the electrical signals include a pixel addressing signal, a voltage signal, and drive voltage;
at least two emitter pixel members coupled to the address means and each disposed above one of the plurality of cavities in the substrate wherein each emitter pixel member comprises a two-level microstructure;
a first level bearing a transistor means, and a second level, set apart and disposed above the first level, and comprising the emitter pixel member, wherein the first level is made of silicon nitride and wherein the second level has an absorber and the first level has a reflector layer opposite of and facing the absorber layer;
means for connecting, supporting, and thermally isolating each pixel member from the substrate;
a trace of electrically resistive material coupled to each pixel member and at least one leg physically and electrically coupled to the substrate;
electronic control means for electrically coupling the pixel addressing signal, the voltage signal, and the drive voltage to each emitter pixel member; and
, transistor means for driving a controlled amount of electrical current through the trace of electrically resistive material and for maintaining the temperature of the trace.
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Abstract
An array for projecting thermal images and a method of making same. The array of the present invention combines a two-tier architecture created with special processing whereby each pixel member resides on an elevated platform directly over discrete pixel control electronics and electrically conducting traces couple a plurality of pixels so that they can be controlled to project thermal images at equal to or faster than video frame rates. Microlens assemblies coupled to each discrete pixel improves the thermal efficiency of the array for certain applications. In the method of fabrication, a semiconductor microbridge-type structure obtains with the use of sacrificial layers under deposited pixel members in a compact array so that the pixel electronics reside beneath their associated pixel and the array electronics inhabit the same chip as the array thereby improving fill factor and time constant of the resulting array.
20 Citations
37 Claims
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1. An apparatus for emitting a wide-band infrared image, comprising:
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a semiconductor substrate having a plurality of cavities therein;
address means disposed on the substrate proximate the plurality of cavities for routing electrical signals to various portions of the substrate, wherein the electrical signals include a pixel addressing signal, a voltage signal, and drive voltage;
at least two emitter pixel members coupled to the address means and each disposed above one of the plurality of cavities in the substrate wherein each emitter pixel member comprises a two-level microstructure;
a first level bearing a transistor means, and a second level, set apart and disposed above the first level, and comprising the emitter pixel member, wherein the first level is made of silicon nitride and wherein the second level has an absorber and the first level has a reflector layer opposite of and facing the absorber layer;
means for connecting, supporting, and thermally isolating each pixel member from the substrate;
a trace of electrically resistive material coupled to each pixel member and at least one leg physically and electrically coupled to the substrate;
electronic control means for electrically coupling the pixel addressing signal, the voltage signal, and the drive voltage to each emitter pixel member; and
,transistor means for driving a controlled amount of electrical current through the trace of electrically resistive material and for maintaining the temperature of the trace. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
a layer of planarization oxide disposed covering said transistor means, a passivating layer disposed covering said planarization oxide layer; and
,a reflector layer is disposed covering said passivating layer, so that said reflector layer opposes said second level.
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10. The apparatus of claim 9, further comprising:
an absorber layer disposed on a nitride layer formed on the second level, directly opposing the reflector layer across a gap region.
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11. The apparatus of claim 10, wherein said gap region is evacuated to a pressure less than ambient pressure.
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12. The apparatus of claim 11, wherein said reflector layer and said absorber layer contain the same surface area.
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13. The apparatus of claim 12, further comprising a metallic plug member disposed to electrically couple only to the electrically resistive material and the electronic control means without establishing electrical contact with said reflector layer or said absorber layer.
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14. Apparatus for emitting a wide-band infrared image comprising:
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a) a substrate, said substrate having a reflective surface;
b) an emitter pixel member supported above and by said substrate, said emitter pixel member being (i) comprised of material which, when heated, emits infrared radiation and (ii) spaced above said reflective surface of said substrate so as to define a cavity therebetween; and
c) electrical connection means connected to said emitter pixel member and adapted to selectively apply electric current thereto so as to heat said member;
d) said apparatus being further characterized by the distance between said reflective surface and said emitter pixel member being selected to provide a tuned optical cavity to thus provide a high optical emissivity of said emitter pixel member over a preselected band of infrared wavelengths. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
a) a trace of electrically resistive material disposed on said emitter pixel members and on legs respectively physically and electrically coupling said members to said substrate, said legs facilitating the thermal isolation of said members from said substrate, and b) means for driving a controlled amount of electrical current through said trace of resistive material.
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34. The apparatus of claim 33 wherein said electronic control means comprises a pixel decoder/multiplexer select circuit and a row enable decoder each electrically coupled to a plurality of discrete pixel column group electrical interconnections.
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35. An apparatus for emitting a wide-band infrared image comprising:
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a) a semiconductor substrate;
b) integrated circuit means disposed on the substrate;
c) an array of emitter pixel members supported above and by said substrate and electrically coupled to said integrated circuit means, each of said emitter pixel members being (i) comprised of material which, when heated, emits infrared radiation and (ii) spaced above said substrate so as to define a cavity therebetween; and
apply electric current thereto so as to heat said member;
d) an infrared reflector layer disposed on said substrate opposite said emitter pixel members;
- View Dependent Claims (36, 37)
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Specification