U.S. Philips Corporation

Leonardo Mw Ltd.

Selex Sensors and Airborne Systems Limited

Philips Electronics UK Limited

Ian M Baker

Richard B Withers

William A Dunn

Christopher Laurence Jones

Christopher David Maxey

Philip Stephen Karl Booker

Leslie George Hipwood

Raymond E King

A large format array is described having a series of smaller arrays daisy chained together to form the larger array. The smaller arrays are mounted on a base plate that may be of a non planar configuration. The daisy chaining together of the smaller arrays enables a smaller number of connections to be made to the external interface via connections.

Large format arrays and methods

Described herein is a multi-color radiation detector that comprises a mesa-type multi-layered mercury-cadmium-telluride detector structure monolithically integrated on a substrate. The detector is responsive to three or more discrete wavelength ranges and means is provided whereby each of the wavelength ranges can be detected independently or in combination with others of the ranges.

Multi colour photon detectors

In an infrared detector device for viewing an object or scene at more than one wavelength, the detector elements (10 and 20) are optimized to have appropriately different infrared responses by being formed in accordance with the invention in different levels (1 and 2) of different material on a substrate (3). Infrared concentrators (55) such as immersion lenses, light-pipes and/or reflectors collect incident radiation (50) over an area larger than the active portion of the associated detector element (10 and/or 20) and concentrate the radiation (50) onto the active portions. The arrangement adopted in accordance with the invention provides adequate space for at least one connection (15) of each upper-level detector element (10) to extend to the substrate (3) through an area of the lower level (2) which is located between the lower-level active portions on which the radiation (50) is concentrated by the associated concentrators (55). This upper-level connection (15) may extend via an island (28) separated from the active portions ( 22,23) of the lower level (2) by a gap (40), or it may extend on a side-wall of the lower-level detector element (20) when this side-wall is insulated or separated by a p-n junction from the active portions of the detector element (20). The different-response elements (10 and 20) may be arranged one above the other or one between the others when viewed in plan view.

Infrared detector devices

An infrared detector device for at least two wavelengths, i.e. 3 to 5 microns and 8 to 14 microns, comprises detector elements (10 and 20) formed in two or more infrared-sensitive materials with different badgaps, e.g. in cadmium mercury telluride. These materials may be provided side-by-side in a single level on a substrate (3) or preferably as different levels (1 and 2) on the substrate (3). Each detector element (10 and 20) comprises a p-n junction (11 and 21) between opposite conductivity type regions (12,13 and 22,23). Electrical connections (15,25,24) extend from these regions to the substrate (3). Freedom in design and fabrication is obtained by a connection structure in which one connection (25) of the longer-wavelength response element (20) contacts both the semiconductor material (2) of that element (20) and the larger-bandgap material (1) of the shorter-wavelength response element (10), at a side-wall (42) of both materials. The larger-bandgap material (1) comprises a further region (18) which adjoins the side-wall (42) and which forms a further p-n junction (19) electrically in parallel with the p-n junction (21) of the longer-wavelength detector element (20).

Plural-wavelength infrared detector devices

An imaging device arrangement comprises infra-red radiation detector elements (10) and signal-processing circuitry including at least one charge-transfer line (30). The detector elements (10) are preferably cadmium mercury telluride photodiodes formed in a common body or body portion which is secured to a substrate (e.g. of silicon) comprising the charge-transfer line (30). Each detector element (10) is connected between an input connection (2,3) of the charge-transfer line (30) and a common electrical connection (4). At least one storage electrode (62) and at least one subtraction gate (63) are present at each input connection (2,3) for subtracting at least one portion (77) of the charge-signal so that only a portion (78) of the charge-signal from each detector element (10) is transferred along the charge-transfer line (30). The substracted charge (77) is drained away via the radiation detector elements (10) by means of a pulse generator (50) or other voltage switching means which is connected to the common electrical connection (4) to switch the common voltage applied to the detector elements (10). A compact structure with fast draining at each input connection (2,3) is obtained. The pulse generator (50) can be formed with other pulse generators of the at least one charge-transfer line (30) in a peripheral area of the circuit substrate.

Infra-red radiation imaging device arrangements

In an imaging device, photocurrent generated by detector elements (1), e.g. cadmium mercury telluride photodiodes, may be integrated in resettable capacitors (2), and an output signal (S) may be derived by reading the potential of the capacitor (2) at the end of its integration period, e.g. using a source-follower MOST (3). In accordance with the invention first and second capacitors (2a and 2b) are switchably coupled in alternate parallel arms between each detector element (1) and the voltage-reading means (3), by means of an arrangement of input gates (8a and 8b) and output gates (9a and 9b). Since one of the first and second capacitors (2a or 2b) can be coupled to the detector element (1) while the other (2b or 2a) is coupled to the voltage-reading means (3), each detector element (1) can be switched from one to the other so as to be operated the whole time for photodetection without its signal being lost (i.e. not integrated) when reading the previous output signal from that detector element (1). This is particularly useful for coupling a row of storage capacitors via a 2-d switching array to a 2-d array of infrared detector elements (1). A similar arrangement of alternately-switchable first and second capacitors (2a and 2b) may be used for visible light imaging, and a modified arrangement may used with a CCD signal processing circuit.

Imaging devices comprising photodetector elements

In an imaging device, photocurrent generated by photovoltaic detector elements (1), e.g. cadmium mercury telluride photodiodes, is integrated in resettable capacitors (2), and an output signal (S) is derived by reading the potential of the capacitor (2) at the end of its integration period, e.g. using a source-follower MOST (3). In accordance with the invention, blooming-protection means (11,48,12) is coupled to each capacitor (2) to inhibit forward-biasing of the detector elements (1) and inversion of the capacitor potential when the capacitor (2) becomes fully discharged by excessive photocurrent. The blooming-protection means comprises a further gate (11) which has substantially the same threshold voltage as the injection gate (10) via which the photocurrent is injected into the capacitor (2). The further gate (11) which is connected at substantially the same control potential as the injection gate (10), is most conveniently formed together with the injection gate (10) as alternate integral parts of a common gate stripe (37) extending at one side of the capacitors (2). When a capacitor (2) becomes fully discharged, the further gate (11) couples it to a source (12) which supplies current to the capacitor (2) to stabilize the potential of both the capacitor (2) and its detector element (1) and so to protect against signal blooming.

Imaging devices comprising photovoltaic detector elements

An array of photovoltaic infrared radiation detector elements are formed in a body of infrared sensitive material, e.g. of cadmium mercury telluride. The body is present on a circuit substrate, which may comprise a silicon CCD for processing signals from the detector elements. An array of regions of a first conductivity type which form the p-n junctions of each detector element with an adjacent body part of opposite conductivity type, extend through the thickness of the body at side-walls of an array of apertures. Each aperture is associated with a detector element and is preferably formed by ion etching. These regions of the first conductivity type are electrically connected to substrate conductors in a simple and reliable manner by a metallization layer in the apertures, without rendering a significant area of the detector insensitive to radiation imaged onto the upper surface of the body. At least the back surface of the detector body (11) has a passivating layer over the area around and between the apertures, to enhance detector element performance. This back surface is secured to the circuit substrate by a layer of electrically insulating adhesive. The main body part is connected to a substrate conductor by a metallization at a surface portion which is outside of the area of the back surface and which is between the apertures. The resulting device is a closely-packed array of high performance detector elements on a circuit substrate. The spacing between adjacent apertures is 100 microns or less.

Method of manufacturing an infrared radiation imaging device

An array of photovoltaic infrared radiation detector elements are formed in a body of infrared-sensitive material, e.g. of cadmium mercury telluride. The body is present on a circuit substrate, which may comprise a silicon CCD for processing signals from the detector elements. An array of regions of a first conductivity type, which form the p-n junctions of each detector element with an adjacent body part of opposite conductivity type, extend through the thickness of the body at side walls of an array of apertures. Each aperture is associated with a detector element and is preferably formed by ion etching. These regions of the first conductivity type are electrically connected to substrate conductors in a simple and reliable manner by a metallization layer in the apertures, without rendering a significant area of the detector insensitive to radiation imaged onto the upper surface of the body. At least the back surface of the detector body has a passivating layer over the area around and between the apertures to enhance detector element performance. This back surface is secured to the circuit substrate by a layer of electrically insulating adhesive. The main body part is connected to a substrate conductor by a metallization at a surface portion which is outside of the area of the back surface and which is between the apertures. The resulting device is a closely-packed array of high performance detector elements on a circuit substrate. The spacing between adjacent apertures is 100 microns or less.

Infra-red radiation imaging devices and methods for their manufacture

A group of infra-red radiation detector elements are manufactured from a body (21) of infra-red sensitive materials on an insulating substrate (22) using two masking steps which do not require critical alignment even with close spacing between the elements. A first masking layer (24; see FIG. 10) e.g. of photoresist is formed on the upper surface of at least the body (21) to determine by a lift-off technique a metallization pattern (35, 36; see FIG. 13) on the body (21) and the substrate (22). A second masking layer (44) e.g. of photoresist is then provided to determine by ion-bombardment through windows (45) of this layer (44) the desired pattern of elements and their electrodes. The ion-bombardment permits removal of exposed areas of not just the body (21) and metallization pattern (35, 36) but also of a passivating layer on the body surfaces; a closely spaced group of elements and their electrodes can be obtained because the ion-bombardment results in steep sides without significant undercutting.

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Romsey, United Kingdom

Ian M Baker