Physics-Based Breakdown Voltage Optimization of Trench MOS Barrier Schottky Rectifiers

A comprehensive study of the breakdown voltage optimization of trench MOS barrier Schottky (TMBS) rectifiers is performed by means of drift-diffusion simulations. First, the principles of operation are explained in terms of the charge-sharing effect between the Schottky and trench MOS components of the unit cell, and correlated with the profiles of the electric field along the drift region E_Sch and the MOS capacitor E_TMOS. Then, the systematic variation of relevant design parameters is used to determine breakdown voltage and leakage current trends, which are analyzed in terms of the electric field. Our results show that E_Sch is the dominating component in structures with thick oxides, shallow trenches, or high-doping concentrations, whereas E_TMOS is the limiting factor for devices with thin oxides, deep trenches, or low doping. Finally, optimum BV is found when the peak value of E_Sch and E_TMOS is approximately the same, and this condition can be reached in a wide range of trench depths for devices with long drift regions and high doping, but in a very narrow window for thin epi-layers or low-doping concentration.