The Secretary of State for Defence in Her Britannic Majesty's Government

Qinetiq Limited

Rex Watton

Charles Thomas Elliott

Cyril Hilsum

Paul Antony Manning

Richard George Humphreys

John Peter Gillham

John Charles Alderman

A method of fabricating a micro-bridge device () onto a substrate (). The method includes the steps of: providing a sacrificial material () on a surface region of the substrate (); patternwise etching the sacrificial material (); providing a sensing material () on a surface region of the sacrificial material; providing a support material () on a surface region of the sensing material; and removing the sacrificial material () leaving support material () with the sensing material () on its lower surface, substantially free standing above the substrate ().

Micro-bridge structure

A thermal detector device comprising an array of thermal detector elements, an array of microbridge structures comprising the array of thermal detector elements, readout silicon integrated circuitry (ROIC) and an interconnect layer on which the array of microbridge structures are arranged. The interconnect layer comprises a plurality of conducting interconnect channels providing an electrical connection between the microbridge structures and input contacts on the ROIC such that the microbridge structures are in electrical contact with, but are separated from, the readout silicon integrated circuitry. As the interconnect layer separates the microbridge structures from the ROIC, the detector material, typically a ferroelectric material, may be fabricated on the microbridge structures at a deposition or anneal temperature which is not limited by the avoidance of damage to the ROIC. Deposition temperatures of at least 500&deg; C. or, preferably, at higher temperatures e.g. 700&deg; C.-900&deg; C., may therefore be used, enabling the fabrication of high performance ferroelectric or microbolometer thermal detector arrays. The invention also relates to a method of fabricating high performance thermal detector arrays comprising an interconnect layer.

Thermal detector array

A thermal detector comprises a row of thermal detector elements each connected to a common bus line via the gate of a high impedance input preamplifier and a switch. The line output from the bus line is taken across a load resistance providing a common source follower load for the prepamplifiers. The signal across the load is passed through an anti-aliasing low-pass filter to a sample-and-hold. Signals then pass to a high-pass digital filter arranged to substract successive signals from each detector element corresponding to open and closed positions of a radiation modulator. This attenuates 1/f noise. The filters are located outside the row. Bulky filter components may accordingly be employed giving good noise performance without affecting detector element spacing. The preamplifiers and the switches are preferably MOSFETs. The detector may incorporate many rows of detector elements to provide a two-dimensional array.

Thermal detector

A thermal imager includes an infrared sensitive light valve and a light source arranged to illuminate the full responsive area of the valve. The imager also includes an optical stage having focussing optics for forming an infrared image upon the surface of the valve and a chopper for modulating infrared radiation from a scene. Modulated light from the valve is read out in parallel by a detector array, and frame signals corresponding to alternate positions of the chopper are subtracted to provide uniformity correction. The light valve may comprise an infrared sensitive optically active liquid crystal cell and an analyzer adjusted to near extinction. An optical processor comprising a lens and an apodized stop filter lies in the light path between the valve and the detector array. The light source may comprise an array of light emitting diode elements and the filter a number of corresponding off-axis stop regions.

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Malvern, United Kingdom

Rex Watton