Ferroelectric imaging system

• US 4,143,269 A
• Filed: 12/19/1977
• Issued: 03/06/1979
• Est. Priority Date: 12/19/1977
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: McCormack, Kent, McNeill, Dane A.
• Primary Examiner(s): Anderson, Bruce C.
• Application Number:
  US05/861,754
• Time in Patent Office: 442 Days
• Field of Search: 250/330, 250/332, 250/338, 250/340, 250/351, 250/352, 250/370, 313/4, 313/46, 357/29, 357/30
• US Class Current: 250/352
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20
• CPC Class Codes: H10N 15/10 Thermoelectric devices using thermal change of the dielectric constant, e.g. working above and below the Curie point

Abstract

An improved ferroelectric imaging system comprises a chopper, lens system, ferroelectric detector matrix, anistropic heat sink, switching matrix, temperature controlled heat sink, drive and read out electronics, video processor, and display. The chopper interrupts infrared energy emanating from a scene, and the lens system focuses the chopped infrared energy on the ferroelectric detector matrix which produces electrical signals representative of the infrared energy impinging thereon. The signals are read out by the drive and read out electronics whose action is synchronized with the chopper action, processed in the video processor and displayed by the display. The ferroelectric detector matrix is a plurality of detector capacitor elements whose lower plates are metal pads formed on the lower surface of the dielectric which is a wafer of ferroelectric material. The switching matrix includes a corresponding plurality of solid state switches operatively connected to output pads, a bias source, and the drive and readout electronics. The anisotropic heat sink includes a plurality of spaced conductor rods of a preselected cross-sectional area and length. The conductor rods are grown on the output pads of the solid state switches and the lower plate capacitor pads are bump bonded to their ends. The conductor rods are either vacuum packed or glass packed depending on their mechanical strength to support the detector matrix. The conductor rods are formed by coating the switching matrix with a photoresist, patterning the photoresist, and electrodepositing metal in the pattern of photoresist. Additional layers are used where necessary to achieve the preselected length. The photoresist is then removed to leave the conducting rods in a spaced relationship. To provide additional mechanical strength the conductor rods are refilled with a glass filled photoresist, the photoresist exposed and removed to leave the glass particles which are sintered to provide a glass frit support for the conductor rods.

Claims

1. An improved ferroelectric imaging system having a ferroelectric detector structure comprising:

(a) a housing;

(b) a temperature controlled heat sink mounted in one end of the housing;

(c) a solid state switching matrix mounted in the housing on the temperature controlled heat sink;

(d) an anisotropic heat sink mounted in the housing in electrical communication with the switching matrix;

(e) a ferroelectric detector matrix mounted in the housing on the anisotropic heat sink, said ferroelectric detector matrix in electrical communication with the anisotropic heat sink; and

(f) a window mounted in the end of the housing opposite the temperature controlled heat sink and in optical alignment with the ferroelectric detector matrix, said ferroelectric detector matrix operative at its Curie temperature in response to the temperature controlled heat sink impinging infrared energy, bias source, said solid state switching matrix to produce electrical signals representative of the impinging infrared energy.

2. An improved ferroelectric imaging system according to claim 1 wherein the anisotropic heat sink comprises a plurality of spaced conductor rods electrically connecting the solid state switching matrix and the ferroelectric detector matrix, said conductor rods having a preselected aspect ratio (A/L) sufficient to eliminate substantially the possibility of thermal shorts existing between the ferroelectric detector matrix and the solid state switching matrix.

3. An improved ferroelectric imaging system according to claim 2, wherein the plurality of spaced conductor rods are in a vacuum.

4. An improved ferroelectric imaging system according to claim 1 wherein the anisotropic heat sink comprises a plurality of spaced conductor rods, each conductor rod thereof including a plurality of electrically connected rod segments.

5. An improved ferroelectric imaging system according to claim 4 wherein the plurality of segmented conductor rods are encapsulated in insulating material to provide mechanical strength.

6. A method of fabricating an improved ferroelectric imaging detector comprising the steps of:

(a) mounting a temperature controlled heat sink in a first end of a housing;

(b) mounting a solid state switching matrix on the temperature controlled heat sink, said switching matrix having a plurality of switches formed in a silicon substrate;

(c) forming an anisotropic heat sink on the solid state switching matrix, said anisotropic heat sink having a plurality of spaced conductor rods in electrical communication with the plurality of switches of the solid state switching matrix;

(d) mounting a ferroelectric detector matrix on the anisotropic heat sink, said ferroelectric detector matrix having a plurality of ferroelectric capacitors in electrical communication with the plurality of conductor rods of the anisotropic heat sink; and

(e) mounting a window in a second end of the housing in optical alignment with the ferroelectric detector matrix.

7. A method of fabricating an improved ferroelectric imaging detector according to claim 6 wherein the fabrication of the anisotropic heat sink comprises the steps of:

(a) forming a plurality of pads on a surface of the solid state switching matrix;

(b) coating the paded surface of the silicon solid state switching matrix with a layer of photoresist;

(c) masking the layer of photoresist and processing the layer of photoresist to form a pattern having a plurality of conductor rod apertures corresponding to the plurality of conductor pads on the surface of the solid state switching matrix;

(d) electrodepositing metal conducting rods in the conductor rod apertures of the photoresist pattern;

(e) polishing the tips of the conductor rods to provide a uniform height and bump bonding surface; and

(f) removing the photoresist pattern to provide a plurality of spaced conductor rods.

8. A method of fabricating an improved ferroelectric imaging detector according to claim 7 wherein the steps are repeated to form a plurality of spaced multiple segmented conducting rods.

9. A method of fabricating an improved ferroelectric imaging detector according to claim 7 further comprising filling the spaces between the plurality of spaced conducting rods with an insulation filled photoresist, exposing the photoresist, removing the photoresist, and sintering the insulating material to provide mechanical strength to the plurality of conducting rods for supporting the ferroelectric detector matrix.

10. A method of fabricating an improved ferroelectric imaging detector according to claim 8 further comprising filling the spaces between the plurality of spaced conducting rods with a glass filled photoresist, curing the photoresist, removing the photoresist and sintering the glass to provide a glass frit for providing mechanical strength to the plurality of conducting rods for supporting the ferroelectric detector matrix.

11. A method of fabricating an improved ferroelectric imaging detector according to claim 7 further comprising filling the spaces between the plurality of spaced conducting rods with a thermosetting plastic for supporting the conducting rods.