Novel MTO-design based on silicon-silicon bonding

A new MOS-turn-off thyristor (MTO) device structure is proposed which is based on the silicon-silicon bonding technology. The basic idea is to connect several p-channel power-MOSFETs with a 3-layer bipolar structure. The 3-layer structure corresponds to the pnp-transistor structure of classical thyristors. It can be manufactured as a disc-type device. During the MTO on-state the current is flowing through the reverse conducting diode of the MOSFET structure. Hence, the n-well of the MOSFETs represents the cathode of the thyristor. The device is turned off with unity-gain by switching on the p-channel to bypass the cathode-side pn-junction. Thus, the device operates like a fully integrated MTO but avoids the technological restrictions in manufacturing VLSI-structures on disc-type devices. In contrast to the conventional hybrid MTO, the device can be also turned on by the MOS gate. The capacitive gate current of the MOSFETs enables an extremely homogeneous latching behavior of the thyristor structure. Finite element simulations have been performed including a physical model of the bonding interface. The results are showing very promising device characteristics.