GB1263381A - Metal contact and interconnection system for nonhermetic enclosed semiconductor devices - Google Patents

Abstract

1,263,381. Semi-conductor devices. TEXAS INSTRUMENTS Inc. 1 May, 1969 [17 May, 1968], No. 22235/69. Heading H1K. [Also in Division C7] A contact layer in ohmic connection with a region of a semi-conductor body comprises a layer of molybdenum containing a homogeneously distributed additive comprising from 3-60% by weight of the layer which additive increases its resistance to corrosion in moist environments. The specified additives in order of preference are titanium, tantalum, chromium, zirconium, hafnium and silicon. For good ohmic contact the contacted regions should be highly doped, e.g. with > 2 x 10<SP>19</SP> atoms cm.<SP>-3</SP> of boron or phosphorus introduced if necessary in an auxiliary diffusion step. Alternatively the surface can be thinly coated with aluminium or with platinum which is sintered to form a platinum silicide layer. Typically electrodes with bonding pads are formed on a planar oxidepassivated transistor element by RF sputtering in a low pressure argon atmosphere from a cathode fabricated from titanium and molybdenum powder to form an overall layer 2500 Š thick which is covered with a 10,000 Š layer of gold deposited in the same sputtering apparatus or by evaporation. The electrode pattern is formed by photoresist masking and etching steps using specified etchants. The element is finally mounted on the central one of parallelstrips, with gold wire emitter and base connections to the outer strips, and potted in plastics by a transfer moulding process. Part of an integrated circuit consisting of a number of interconnected sub-circuits each as in Fig. 9 (not shown) is seen in Fig. 12 with two layers of interconnections forming respectively the internal connections of the sub-circuits and the connections between them. The first layer of interconnections are form etched from an overall layer 116, 117, 118 consisting of 7500 Š of gold or copper sandwiched between 1200 Š layers of molybdenum or molybdenum-titanium. A 20,000 Š layer 119 of silicon oxide, or of silicon nitride, alumina or organic insulator is then formed by evaporation or sputtering and selectively etched to expose parts of the interconnection pattern to be contacted. Molybdenum is then removed from these parts V prior to deposition of an overall 1200 Š thick layer 120 of molybdenum-titanium and a 7500 Š overlayer 121 of gold. These layers are next patternetched to form the intercircuit connections and wires thermocompression bonded to the terminal points of the completed circuit.