Patent GB-1405459-A (GB)
Title: Bidirectional integrated semiconductor component
IPC: H01L29/747
Filed: 1972-07-06
Abstract: 1405459 Semi-conductor devices SILECSEMI-CONDUCTEURS 6 July 1972 [6 July 1971] 31801/72 Heading H1K [Also in Division H3] A bidirectional integrated semi-conductor device has a first current carrying electrode of a first gate controlled bidirectional semi-conductor switch T 3 , Fig. 2 connected to the gate of a second gate controlled bidirectional semiconductor switch T 4  of lower switching sensitivity than the switch T 3  and the second current carrying electrodes of the switches T 3  and T 4  are coupled together so that an application of an operating potential between the first and second electrodes of the second switch T 4 , which is to be switched, a current flows initially in the first switch T 3  and provides a gate control current for switching the second switch T 4  into the conductive state. This current is relatively large and improves the di/dt characteristic of the triac T 4 . The current circulating in the triac T 3  is now lower than that circulating in the triac T 4 . The current in T 3  is finally reduced to zero. Following this period of conduction the device is then conditioned for blocking voltage in the opposite direction of conduction. The switching sensitivity of a gate controlled bidirectional semi-conductor switch is defined to be inversely proportional to the voltage on the gate with respect to the more negative of the main current carrying electrodes necessary to turn the switch on. The triac T 3  does not conduct until the end of the conduction cycle, during which time the triac T 4  conducts alone and triac T 3  exhibits the same dv/dt characteristics as it exhibits under conditions of non-conduction. The triac T 4  exhibits improved dV/dt blocking characteristics. A relatively high increase in load current (di/dt) in the device can cause breakdown of the device by point fashion. This characteristic can be improved by increasing the amplitude and rate of application of the control current to the gate electrede of the device by means of the first switch T 3  which is more sensitive than the second switch T 4 . The second switch T 4  being less sensitive has a higher dv/dt characteristic so as to improve the dv/dt blocking characteristic of the device so as to protect the device from being triggered on by a relatively large dv/dt voltage applied between the load current terminal of the device. The circuit of Fig. 2 is formed as an integrated bidirectional control device (Figs. 3A, 4B, not shown) and Fig. 5 where the first switch T 3  is formed as a triac 200 and the second switch T 4  is formed as two unidirectional thryristors 100, 300 integrated on the same silicon wafer. The regions 12, 14, 15, 2, 4 and 5 may be of N-type and the regions 13, 16, 1 and 6 are of P-type. The triac 200 is formed as a central core while the thyristors 100 and 300 are located diametrically opposite and are semicircular in shape forming a ring surrounding the central core. The triac 200 has a gate electrode 26 and regions 4 and 12. The thyristor 300 has remote triggering and the two thyristors 100 and 300 have opposite directions of conductivity and their switching sensitivies are similarly reduced by a short circuit coupling 11. A resistive layer 8 interconnects the gate 7 of the thyristor 100 and a part of the layer 1 of the thyristor 300. The gate 4 of the thyristor 300 is intergrown with the upper region 4 of the triac 200 and is also connected by the layer 9 to the region 3 of the triac 200. Metalized surfaces 24 and 25 are provided between the gate 4 of the thyristor 300 and the layer 6 and between the layer 4 of the triac and the gate 7 of the thyristor 100.