850V NMOS driver with active outputs

• Published in: 1984 International Electron Devices Meeting pp. 266 - 269
• Main Authors: Martin, R.A., Buhler, S.A., Lao, G.
• Format: Conference Proceeding
• Language: English
• Published: IRE 1984
• Subjects: Dielectric materials; Dielectric substrates; Driver circuits; Logic devices; MOS devices; Resistors; Sheet materials; Shift registers; Surface resistance; Voltage
• DOI: 10.1109/IEDM.1984.190698

This paper describes a unique second generation fully integrated NMOS device operating at up to 850V. The 5.46×5.26 mm 2 chip consists of 16 pull-up/pull-down high voltage output drivers, a 16 bit shift register, and gating logic. The HV output drivers are comprised of two high voltage transistors and a polysilicon pull-up resistor, fabricated on a 70Ω-cm substrate, without dielectric isolation or epitaxial material. The high voltage transistors have closed geometry with a two layer polysilicon field plate. One layer of the field plate has high sheet resistance to set the surface potential above the n- drift region. The low voltage logic is standard TTL compatible NMOS, isolated from the high voltage by a grounded barrier. An analysis of the high voltage transistors, based on a solution of Poisson's Equation 1 is presented which emphasizes the effect of the overlaying metal line on the transisor's performance.