ESD Phenomena and Test Methods The Physics of ESD Protection Circuit Elements Requirements and Synthesis of ESD Protection Circuits Design and Layout Requirements Analysis and Case Studies Modelling of ESD in Integrated Circuits Effects of Processing and Packaging.

ESD in silicon integrated circuits

The dependence of the increase of current in a transistor of n+-p-n-n+type on time is investigated, and current mode second breakdown (CSB)and thermal mode second breakdown (TSB) are discriminated by the duration of the delay time before which second breakdown occurs. The boundary conditions between CSB and TSB in steady state are clarified. The critical voltage between CSB and TSB is determined by the width of the n layer, the immobile charge density of the n layer, and the injected electron density from the emitter to the n layer. The numerical analysis was in qualitative agreement with the experimental results.

Boundary conditions between current mode and thermal mode second breakdown in epitaxial planar transistors

The experimental data for the temperature dependence of the thermal conductivity of silicon are reviewed. It is proposed that an empirical formula of the form K = K_{0}/(T-T_{0}) provides a good description of the measurements. The steady-state heat-flow equations are formulated so that the nonlinear heat-flow problem may be solved in terms of an equivalent linear problem. The method is applied in conjunction with an idealized thermal and electrical device model, to calculate the thermal instability boundary (or second breakdown boundary), of a commercial power transistor.

The heat-flow problem in silicon: An approach to an analytical solution with application to the calculation of thermal instability in bipolar devices

A literature search on semiconductor device modeling was performed and a bibliography of 486 references was compiled Electrical and Electronics Abstracts and Engineering Index of January 1970 to May 1974 were the main sources used in this search Selected articles from the literature prior to 1970 are also included in this bibliography For easy access to the needed references, the bibliography is divided into twenty-nine sections A cross reference is given at the end of each section

A bibliography on semiconductor device modeling

The current/voltage characteristics of Si n-p-ntransistors, when the device is pulsed into second breakdown for several nanoseconds, are studied. The collector/base characteristics have limits given by Ie= 0 which can be modelled approximately by neglecting recombination, and by Ib= 0 which requires recombination to be fully understood. This later condition is closely analagous to the Kirk effect with a plasma of holes and electrons close to the base region. In all these second-breakdown states the electron multiplication factor is low, typically less than 1.33, so that there is little useful multiplication gain. Second breakdown thus prevents the transistor from being used as a 3-terminal avalanche transistor. Failure at high current levels occurs most readily in the Ie= 0 state. The cutback in voltage and increase in current can be limited by tailoring the collector impurity profile. These two features suggest ways in which transistors may be improved to protect them against short pulse burnout via current-mode second breakdown.

Current/voltage characteristics of transistors operating in current-mode second breakdown

Two kinds of second breakdown are considered. 1. (1) thermal mode breakdown. 2. (2) current mode breakdown. All the theoretical considerations refer to the open circuit base configuration, but the results are generalized to both the forward and reverse bias cases. The problem is approached by assuming that the transverse voltage drops are negligibly small in both the emitter and collector ohmic connections (the substrate is regarded as the ohmic connection of the collector). Calculations show that the current-temperature system of a transistor is in a negative feedback regime as long as the temperature of the hottest part of the device does not exceed the critical value. At this stage, an approximately constant current density is maintained within the ‘effective transistor’. Once the critical value is reached, the transistor goes over into a positive-feedback regime and a spontaneous constriction of the current paths results. The current mode breakdown is due to the occurrence of a negative resistance in the collector junction as a result of the Kirk effect. Once this begins in a spot, the collector capacity discharges through it and this creates a pinching-in field. The high concentration of the dissipated energy which follows brings about a final thermal breakdown.

G. Roman

Papers

A model for computation of second breakdown in transistors