Deep trench junction termination employing variable-K dielectric for high voltage devices

Deep trench junction termination employing variable-K (VK) dielectric for high voltage devices is proposed and studied. The device features 3 layers dielectric trench. The bottom of the trench is low-K dielectric (LK2), which is used to sustain the most reverse bias voltage. The top of the trench is high-K dielectric (HK), which forces most of the electric displacement lines via HK dielectric in the trench instead of the silicon drift layer. The middle layer is also low-K dielectric (LK1), which transmits part of the electric displacement lines in the LK2. A new electric field (E-field) peak introduced in the drift region next to the interface between LK1 and LK2 dielectric results in a more uniform E-field, compared with the device with low-K dielectric-filled trench (LKT). Numerical simulation shows that a diode with proposed junction termination reduces the termination width by 21%-77% compared with the LKT diode at the same breakdown voltage (BV).