Integrated circuit (IC) with a two-terminal diode device to protect metal-oxide-metal capacitors from ESD damage

An integrated-circuit (IC) chip comprising circuitry with elements such as transistors and including capacitors, said circuitry being connected by a lead to an external terminal point of said IC chip, said IC chip further being formed with a clamp device to prevent damage to any capacitor element of said circuitry from electrostatic discharge (ESD) striking said terminal point, said clamp device comprising a diode with anode and cathode and being formed during the process of forming the chip including:

• isolation means defining a region for said clamp device;
• said region including a silicon region with dopant of one type;
• said silicon region including an annular plug with dopant of said one type extending around the outer reaches of said region to serve as a low resistance current path for the anode;
• said silicon region further including a plug of circular cross section interiorly of and concentric with said annular plug, said circular-section plug being formed with dopant of type opposite said one type to serve the function of a cathode;
• first contact means centrally located interiorly of said silicon region to establish one contact for making electrical connection to said circular plug;
• means to establish a second contact to make electrical connection to said annular plug;
• means connecting one of said contacts to a low-impedance bus;
• and
• means connecting the other of said contacts to said lead between said terminal point and said IC circuitry so as to intercept and shunt to said low-impedance bus electrostatic pulse energy received from said terminal point thereby to provide for dissipation of the ESD energy to prevent it from damaging said IC circuitry.