Abstract
Trench gate power MOSFET is the most popular product recently. It is due to the advantages of low switching loss and easy driver circuit design. Furthermore, the on-resistance of trench capacitor is reduced by the development of semiconductor fabrication technology. The conventional vertical double-diffused MOSFET’s on-resistance and packing density were limited by the horizontal channel of the device. In the trench gate MOSFET, the channel is vertical. So, it has a higher channel density than either the VMOS or DMOS structures. The trench gate power MOSFET also has low specific on-resistance because of lacking JFET effect. But the technology for the fabrication of this trench structure is difficult. And the gate oxide quality depends on the post-etching important. This thesis investigates the gate oxide process optimization and evaluation of the trench gate power MOSFET. Two major topics are investigated under this thesis : (1) The effects of different sacrificial oxide treatments on reactive-ion-etched trench surfaces were discussed. Silicon dioxide grown on the trench surfaces which was treated by sacrificial oxidation would improve the gate oxide quality. Besides, the N2O annealing after gate oxidation improves the electrical characteristics significantly. (2) CF4/O2 post etching treatments was investigated too. The effects of gas flow, RF power, chamber pressure and etching time for post etching treatments were discussed by electrical characteristics. By combining the effects of the CF4/O2 treatment and sacrificial oxidation processes, a smooth trench surface with excellent electrical characteristics was obtained.