| 摘要 |
1,195,515. Semi-conductor devices. STANDARD TELEPHONES & CABLES Ltd. 7 June, 1968, No. 27164/68. Heading H1K. The cathode region of a thyristor has a shallow centred portion 13 surrounded by a deeper portion 12, so that the gate region 2 has a central portion 5 of greater thickness than a surrounding portion 6. The Si device shown has boron or gallium-diffused gate and anode regions 2, 4 respectively and a phosphorusdiffused cathode region 1. A P+ type anode contact region is also diffused from a layer of gallium printed on to the lower surface 11 of the wafer. The outer portion 12 of the cathode region 1 is formed in two stages; viz. deposition of phosphorus from its vapour followed by a drive-in stage to produce the deep annular portion 12; while the central portion 13 is formed by a single deposition stage which results in relatively shallow diffusion. Oxide masking defines the limits of these diffusion processes. Gold is diffused into the base region 3 from a layer plated on the lower surface 11 of the wafer. Layers of nickel are plated on to the surfaces of regions 4, 1, 2 to form bases for the subsequently applied electrodes 7, 8, 9 respec tively. Individual thyristors are then divided from the wafer in which they have been formed simultaneously, and their edges are tapered by air-abrasion. |
