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Distinguishing Failure Modes in a Bipolar Device

IP.com Disclosure Number: IPCOM000046626D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Hsieh, CM: AUTHOR [+2]

Abstract

Testing methods have been developed to distinguish the failure modes of a transistor pipe from the failure mode due to the lack of connection between the extrinsic and intrinsic base regions of a transistor. The methods are convenient and nondestructive. For the advanced transistor with extrinsic and intrinsic bases processed separately, a link-up problem can occur between these two base regions. When the lateral diffusions are insufficient or the sidewall is too wide, the two base regions 2 and 1 are separated and are not linked up or connected together, as shown in Fig. 1. The device becomes defective, and the intrinsic base 1 is inaccessible from the external land or pad. The extrinsic base 2 is connected to the external land, but it is isolated from the emitter and the collector of the transistor.

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Distinguishing Failure Modes in a Bipolar Device

Testing methods have been developed to distinguish the failure modes of a transistor pipe from the failure mode due to the lack of connection between the extrinsic and intrinsic base regions of a transistor. The methods are convenient and nondestructive. For the advanced transistor with extrinsic and intrinsic bases processed separately, a link-up problem can occur between these two base regions. When the lateral diffusions are insufficient or the sidewall is too wide, the two base regions 2 and 1 are separated and are not linked up or connected together, as shown in Fig. 1. The device becomes defective, and the intrinsic base 1 is inaccessible from the external land or pad. The extrinsic base 2 is connected to the external land, but it is isolated from the emitter and the collector of the transistor. It is impossible to check directly whether the two base regions are linked or not. The inversion layer 3 establishes a channel path between the collector and emitter because the intrinsic basewidth is very narrow and its doping concentration is very low. The forward and reverse characteristics of base-collector, base-emitter and collector-emitter are all very similar to the transistor with a pipe, as shown in Fig. 2. There are two ways to differentiate these two types of failure modes: 1. For a transistor pipe, the pipe size or the pipe resistance can be modulated by applying a bias voltage at the extrinsic base. When...