Electrostatic discharge protection device.

摘要

A thick-oxide ESD transistor for a BiCMOS integrated circuit has its source/drain contacts formed of the BiCMOS base or emitter polysilicon and its source/drain formed by an outdiffusion of the respective polysilicon contact. In one embodiment the BiCMOS resistor doping deepens the ESD source/drains, and in another embodiment the BiCMOS collector reach through doping deepens the ESD source/drains. The entire ESD transistor is fabricated from a standard BiCMOS process without any additional steps, has an area of about 100 square microns, can shunt up to 6000 volts, and has a turn-on time of about 10 picoseconds. For instance, a NFET (70) is formed on the a P+ silicon substrate (30), P- epitaxial layer (31), and N- epitaxial layer (32). A P well (64) is formed in a CMOS process that is used to form the P wells for N channel FET in the BiCMOS protected circuitry. Here the source contact (48A) and the drain contact (48B) are formed from the N+ emitter polysilicon layer (48). The source (62) is formed from an outdiffusion (39A) from the source contact (48A), corresponding to the emitter outdiffusion (39) of the NPN subcollector doping (33) and reach-through collector doping (34). Likewise drain (63) is formed from drain contact outdiffusion (39B) and well (69) which is also formed in the said same process. The gate (66) of NFET (70) and the drain interconnector (67) are formed from a single section (52B) of the metal interconnection layer (52) which forms the emitter interconnection of the NPN (15C). Likewise the source interconnector (52A) is made from another section thereof. <IMAGE>