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Electrostatic Discharge Protect Device for Integrated Bipolar Technology

IP.com Disclosure Number: IPCOM000038962D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Leen, TK: AUTHOR [+2]

Abstract

A standard NPN transistor, with collector and base leads tied together, is used as a shunt path to protect emitter/base junctions against damage (typically, an emitter-base short) during an electrostatic discharge (ESD). The protective device is made on the chip in the same processes that create the devices to be protected. Thus, though the breakdown potential (BVebo) of the devices may vary from chip to chip, BVebo of protected and protective devices on any one chip is always a single value. Therefore, prevention of ESD-induced base-emitter shorting is assured. In Fig. 1, transistor T2 is the protective device for other transistors in a circuit, e.g., transistor T4. When the base B is connected to the collector C as shown for Transistor T2, the current- voltage (I-V) characteristic, shown in Fig. 2, results.

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Electrostatic Discharge Protect Device for Integrated Bipolar Technology

A standard NPN transistor, with collector and base leads tied together, is used as a shunt path to protect emitter/base junctions against damage (typically, an emitter-base short) during an electrostatic discharge (ESD). The protective device is made on the chip in the same processes that create the devices to be protected. Thus, though the breakdown potential (BVebo) of the devices may vary from chip to chip, BVebo of protected and protective devices on any one chip is always a single value. Therefore, prevention of ESD-induced base-emitter shorting is assured. In Fig. 1, transistor T2 is the protective device for other transistors in a circuit, e.g., transistor T4. When the base B is connected to the collector C as shown for Transistor T2, the current- voltage (I-V) characteristic, shown in Fig. 2, results. During a positive ESD voltage excursion, the device T2 displays characteristic Zener conduction (linear I-V curve) from circuit voltage V = BVebo to VH . As the ESD event attempts to raise V above VH, the device T2 enters a low resistance regime which reduces circuit voltage V to VL . Thus, the most positive voltage experienced by the protected circuit is VH . In a negative ESD voltage excursion, device T2 acts as a conventional diode to clamp the circuit voltage V at Vbe. Since devices within the protected circuit, e.g., T4, are created in the same process in which device T2 is made, B...