U.S. Philips Corporation

Brian C Easton

Peter A Whiffin

Christopher D Maxey

A CVD reactor vessel for forming a solid state electronic device comprising (a) a reaction zone laterally separated from a first zone, (b) support means for supporting a substrate in said reaction zone, (c) heating means for heating both said first zone and said reaction zone, (d) first supply means for supplying at least one first reactant into a gas stream flowing from said first zone to said reaction zone, and (e) second supplying means for supplying at least one second reactant into said gas stream between said first zone and said reaction zone, said second supply means including an injection tube extending through said first zone to a location between said first zone and said reaction zone, said injection tube having a widened outlet so that the flow velocity of said second reactant more closely matching the flow velocity of said gas stream, wherein said substrate receives a layer of material such as cadmium mercury telluride formed from said reactants.

CVD reactor vessel for forming a solid state electronic device

In the manufacture of an electronic device, e.g. an infrared detector of cadmium mercury telluride, a gas stream (36) comprising two or more reactants is passed over a heated substrate (29) in a reaction zone (C) of a reactor vessel (1) so as to deposit material in a layer (30) on the substrate (29). One reactant, e.g. a readily decomposible cadmium alkyl (Me.sub.2 Cd), is supplied to the reaction zone (C) by means of an injection tube (b 12) which passes through a heated first zone (A) of the vessel (1). The tube (12) has a narrow bore (y) to provide a high flow velocity for this reactant (Me.sub.2 Cd) through the first zone (A). In accordance with the invention, the tube (12) widens in at least one dimension (x), towards its outlet end, so as to provide a wider outlet for injecting the reactant (Me.sub.2 Cd) into the gas stream (38,36) with a lower flow velocity which matches more closely the flow velocity of the gas stream (38,36). A more balanced mixing is achieved leading to improved compositional homogeneity in the deposited layer (30), even for difficult materials such as cadmium mercury telluride. The heated first zone (A) may comprise a capsule (2) containing e.g. a pool of mercury (3), and such a capsule (2) preferably has an outlet (a) of smaller cross-sectional area within which the widened outlet of the injection tube (12) is concentrically arranged so that the gas stream (38) is symmetrically constricted around the outlet of the injection tube (12).

Chemical vapor deposition of cadmium mercury telluride

Alternate layers of CdTe and HgTe are deposited on a substrate in a reaction zone inside a reactor vessel using a method involving the steps of (a) passing a gas stream containing a volatile tellurium compound (Et.sub.2 Te) over the substrate while maintaining an atmosphere of mercury vapour in the reaction zone, and (b) switching on and off a separate supply of a volatile cadium compound (Me.sub.2 Cd) to the reaction zone so as to deposit CdTe when the separate supply is on and to deposit HgTe when the separate supply is off (O). The surface of the substrate is irradiated with electromagnetic radiation (UV) the intensity of which is switched during the deposition. The irradiation intensity (UV) is reduced, possibly even to zero (0), when the supply of the volatile cadium compound (Me.sub.2 Cd) is switched on. When the cadium supply (Me.sub.2 Cd) is switched off (O), the irradiation intensity (UV) is increased to promote photodissociation of the volatile tellurium compound (Et.sub.2 Te) by the electromagnetic radiation (UV). This permits the layers to be grown at a low substrate temperature, while avoiding premature nucleation of CdTe in the gas stream. The switching of the radiation intensity (UV) may be effected using a mechanical shutter to switch off (O) the irradiation (UV) or using an adjustable iris or movable neutral-density filter to reduce the UV intensity. The alternate layers may be interdiffused during growth to form a cadmium mercury telluride layer for an electronic device, for example an infrared detector or a bipolar transistor. Alternatively, the alternate HgTe and CdTe layers may be preserved in the final device, for example as a 'superlattice'.

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Reigate, United Kingdom

Brian C Easton