A Bootstrap Diode Fabricated by a New 1200-V Silicon-on-Insulator Bipolar-CMOS-DMOS Process for High Voltage Integrated Circuits

The bulk-silicon bootstrap diode (BSD) is difficult to be integrated in 1200 V high voltage integrated circuits (HVIC), because of the large substrate leakage current. In this work, a new 1200 V silicon-on-insulator (SOI) process is proposed to realize the integration of 1200 V BSD. The proposed SOI process relies on the deep N-well (DN)/P-type substrate (P-sub) junction to increase the vertical BV, and the BSD region in the top silicon is almost only withstand lateral voltage. The DN is formed in the P-sub by high-energy ion implantation, penetrating through both the top silicon and the buried oxide. In addition, tungsten-filled deep trench isolation (DTI) is used to bring the electrode of the DN to the device surface, and the oxide-filled DTI provides electrical isolation between devices. In the off-state of the proposed BSD, the DN and cathode are biased to a high voltage, and the P-sub and anode are grounded. The vertical BV is determined by the reverse-biased DN/P-sub junction. The fabricated BSD achieves a breakdown voltage of 1460 V. It achieves a forward current of 444 μA/μm at forward voltage of 15 V, with a very low substrate leakage current (< 1 nA). This performance is more competitive than that of BSD emulator devices in bulk-silicon processes.