GB1366845A - Integrated thyristor semiconductor arrangements - Google Patents

Abstract

1366845 Thyristors SIEMENS AG 21 March 1973 [23 March 1972] 13461/73 Heading H1K A thyristor (Figs. 1, 2) has a square semiconductor body within which a first cathode zone 1 of, e.g. N-type Si of annular shape has a central aperture containing an ignition electrode 6 electrically connected to a P-type base zone 2. A further P-type zone 7 extending to the boundaries of the square defines the anode of an antiparallel connected diode. A third zone 3 underlying zone 2 forms an N-type base zone of the transistor, and under this is a fourth P-type anode zone 4, surrounded by an edge N-type zone 8 forming the diode cathodes Electrodes 5 and 9 are applied to the thyristor cathode 1 and anode 4, and are electrically connected to P-type base 2 and N-type base 3, and to diode anode 7 and cathode 8 respectively. For negative potential on electrode 5 and positive on electrode 9, the integrated diode is blocked and positive potential on electrode 6 fires the thyristor, while with positive potential on electrode 5 and negative on electrode 9 the diode conducts a reverse current, so that for control of oscillating current the thyristor fires during positive halfwave and the negative halfwave traverses the diode. The anode of the latter is spaced a distance d (= at least 2 diffusion lengths) from the thyristor cathode and its cathode is similarly spaced from the thyristor anode so that stored charge carries are eliminated by recombination to discourage unintended ignition. In a modification (Fig. 3, not shown) the lower zone of the thyristor extends over the whole width of the s/c body and the diode has four layers incorporating the P, N, and P layers of the thyristor and the cathode N-zone 8; so that it conducts on a trigger voltage not exceeding the highest allowable thyristor blocking voltage. A five layer diode may be used, alternatively, with a trigger voltage which drops on triggering to the Zener voltage of one of the outer PN junctions. The zone sequence of the thyristor may equally be PN PN with reversal of the diode anode and cathode. The zones may be doped by the usual masking and diffusion, and the thyristor is surrounded by the diode on all sides.