U.S. Philips Corporation

Richard B Withers

Ian M Baker

An infra-red radiation detector element and its manufacture. The detector element has a mesa (31) of infra-red sensitive material, e.g. cadmium mercury telluride, with separate metal electrodes (64 and 55, see FIG. 17) formed on side-walls of the mesa (31) from a metal layer 33. This permits a significant proportion of the current flow occurring between the electrodes (64 and 55) in operation of the element to pass across the bulk of the mesa (31) between its side-walls and not adjacent its top surface where the carrier recombination velocity may be higher. The mesa (31) is formed by ion-etching using a masking layer (24) e.g. of photoresist, and this permits reproducible etching over a uniform depth and the obtaining of a topographically rough surface to which the subsequently-deposited metal layer (33) can have good adhesion. The electrodes are formed from this layer (33) by a lift-off technique using the same masking layer (24). The ion-etch definition of the mesa (31) can also be used to etch unmasked parts of a passivating layer (14) on the element surface without any significant undercutting.

Infra-red detector elements

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

Richard B Withers