Design of Bonded MTO ThyristorsThe silicon-silicon bonding technology enables the realization of innovative semiconductor devices by separate manufacturing of MOS-structures and bipolar structures, using a full wafer for single devices. Afterwards both parts can be connected by a bonding process, realizing a device with new characteristics. A MOS-Turn-Off Thyristor (MTO) manufactured via this bonding technique is depicted in Figure 1. This device offers the low on-state voltage drop typical for thyristors and can be turned off by a simple voltage signal. A lot of other semiconductor devices can also be realized by the use of the bonding technology. For example, fully bi-directional devices can be built quite easily.
Chip-on-Wafer Bonding - A new Fabrication Technology for High-Power SemiconductorsIn a current research project, a new fabrication technology for high-power semiconductor devices is developed. With the Chip-on-Wafer bonding process MOSFET-Chips can be directly bonded on large wafer substrates. Thereby, the two semiconductors are connected via hydrophobic wafer bonding. As an advantage of this process, the MOS-structures of the devices can be manufactured independently from the bipolar structures. By using the bonding technology, new high-power semiconductor devices with MOS-structures can be manufactured, without using lifetime reducing bond-wires. A simplified illustration of the chip-on-wafer bonding process is depicted in Figure 1. At the beginning, the MOSFET-chips are glued on a carrier wafer with a special epoxy resin (A). The MOSFETs are back thinned and polished to a final thickness of approximately 20 µm (B). Next a wet chemical cleaning is accomplished, before the MOSFETs are bonded to a bipolar wafer (C). The carrier wafer and the MOSFET-chips are separated during the last process step (D). A test structure with dummy chips which are bonded on a wafer is depicted in Figure 2.