Patent GB-1270031-A (GB)
Title: Improvements in and relating to semiconductor devices
IPC: H01L23/522
Filed: 1969-04-01
Abstract: 1,270,031. Semi-conductor bi-stable circuits. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 1 April, 1969 [4 April, 1968], No. 16967/69. Heading H3T. [Also in Divisions G4 and H1] A semi-conductor switch comprises an emitter electrode disposed between a pair of contacts on a zone of one conductivity type and capable of injecting minority carriers so as to cause conductivity modulation in the zone, the emitter being also connected to another point on the zone outside the area in which modulation occurs. In the Fig. 1 arrangement zone 1 is of N-type silicon and the pair of contacts comprise parallel diffused N-type strips 3, 9 communicating with conductive tracks 16, 11 lying on the passivating oxide layer. The emitter consists of a diffused P-type inclusion 4 and is connected to a point 14 on the zone via conductive track 12 so that, in the absence of conductivity modulation it is at a lower potential than the parts of the N zone adjacent the emitter thus inhibiting injection, and the device is switched off. In certain cases connection to the track 11 is made through a resistive track on the insulation or a resistor diffused into the zone surface. When a large enough positive pulse is applied to track 12 minority carriers are injected and produce conductivity modulation so that on termination of the pulse the device remains on. For certain voltages VB the on and off states can both be achieved at zero current thus economizing on power. In an alternative arrangement the emitter is connected to an N-type zone overlapping the P-type emitter zone so that injection occurs in the off and on conditions. This arrangement can be switched as above or by momentarily changing the voltage V B . A modified device can be used as a memory cell. In this case a read-in emitter is disposed between emitter 4 and contact 9. Information is stored by temporarily reducing voltage V B , causing the device to turn off unless the read-in emitter is biased to cause injection and hence conductivity modulation. Read-out is effected by superimposing a pulse on voltage V B  and sensing the potential of a collector disposed between emitter 4 and contact 3. The read-out signal can be amplified in a lateral planar transistor formed by diffusion in the N-type zone adjacent the device which may form part of a rectilinear matrix. In the shift register shown in Fig. 6 each emitter region, e.g., 4B is connected by a conductive strip 12B on the passivation to a contact 13B disposed between auxiliary emitter 32B and contact 3, this emitter in turn being connected to a collector lying between the emitter 4A of the preceding device and contact 3. In operation or application of a shift pulse constituted by a temporary reduction in V B , if devices A and B are initially both off no injection occurs and they remain off. If A only is on, its injected holes are swept up by the collector, thus causing injection from 32B. The potential of contact 13B rises as a result of conductivity modulation, causing emitter 4B to inject carrier and turn on device B. On termination of the pulse device A remains off. If initially only B is on both devices are switched off by the pulse and if both are initially on device A is switched off. A more efficient physical arrangement and configuration of the various parts of such a shift register are described with reference to Fig. 8 (not shown).