THYRISTORS AND THEIR MANUFACTURE

摘要

The forward and reverse blocking voltage capability of a thyristor in accordance with the invention is substantially independent of the active thyristor area (Aa), thereby facilitating its design and its manufacture. This is achieved by means of a concentric arrangement of a deep inner lower-doped perimeter zone (42) of the forward base region (2) with a deep outer perimeter zone (43) of the same conductivity type, doping profile and depth (A4xj=Axj). The outer perimeter zone (43) brings the reverse blocking p-n junction (34) to the front surface (11) at a lateral distance (D3) around the forward blocking p-n junction (32). The outer perimeter zone (43) extends in depth to a lower perimeter zone (44) of the underlying region (4) that forms the reverse blocking junction with the high-resistivity base region (3) of opposite conductivity type. All these perimeter zones (42-44) together provide the thyristor with a deep peripheral termination which surrounds the active thyristor area (Aa). By making the inner and outer perimeter zones (42, 43) much deeper than the surrounded forward base region (2), the forward and reverse blocking voltage capability of the thyristor is determined substantially independently of the doping of the forward base region (2) and layout geometry of the N-P-N-P or N-P-N-P-N region structure in the active thyristor area (Aa). This doping and layout geometry can be chosen to give different magnitudes of transistor gain and different thyristor switching characteristics, all within the same peripheral termination. Current conduction in the lower-doped perimeter zone (42) is less than in the highly-doped, highly-conductive base perimeter of prior-art planar thyristors and may even be pinched off from the active area (Aa), so easing the layout design of emitter-base shorts (1a) in the active area (Aa).