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Finding Temperature Distribution in High Voltage Transistor

IP.com Disclosure Number: IPCOM000087411D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Gaur, SP: AUTHOR

Abstract

Fig. 1 shows a section view of a portion of a silicon chip of a conventional transistor having emitter region 2, base region 3, collector N-region 4, collector N+ region 5, a collector electrode 6 on the bottom surface of the chip and base electrode 9, emitter electrode 7 and insulation layer 8 on the top of the chip. While a high voltage transistor is being switched, it undergoes a simultaneous condition of high current and high voltage and thus is subject to temperature stress. Fig. 2 describes a program that calculates the temperature distribution within the transistor for selected conditions of voltage at the terminals 6, 7 and 9.

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Finding Temperature Distribution in High Voltage Transistor

Fig. 1 shows a section view of a portion of a silicon chip of a conventional transistor having emitter region 2, base region 3, collector N-region 4, collector N+ region 5, a collector electrode 6 on the bottom surface of the chip and base electrode 9, emitter electrode 7 and insulation layer 8 on the top of the chip. While a high voltage transistor is being switched, it undergoes a simultaneous condition of high current and high voltage and thus is subject to temperature stress. Fig. 2 describes a program that calculates the temperature distribution within the transistor for selected conditions of voltage at the terminals 6, 7 and 9.

Block 12 in Fig. 2 shows the step of entering the design parameters of the transistor that is being studied. The parameters N(D)+ and N(A) (shown in other blocks) are the concentration of donor atoms and acceptor atoms at each of a large number of points in the two-dimensional drawing of Fig. 1. The selected voltages of the three electrodes and the physical dimensions of the transistor are also entered in step 1. In block 13, initial values are established for psi, n, p and
T. The terms n and p are concentration of mobile electrons and the concentration of holes, and these initial values are set corresponding to initial values of zero voltage for the base, emitter and collector electrodes. For the same reason, the term psi (the potential at a point in the transistor) is initially given a value corresponding to zero applied voltages. Temperature, T, is set to a suitable value such as 300 Degrees K representing the heat sink temperature. If the approximate solution for the specified operating condition is known from some previous estimate, then the initial values of psi, n, p and T correspond to this approximate solution. These initial values are established for each point in the system of points in the diagram of Fig. 1.

In block 14 of the program, Poisson's equation is solved for psi, using the initial values established in the two preceding steps. (Poisson's equation relates the gradient of the electric field to the concentration of mobile electrons and holes and to the fixed donor and acceptor atom concentrations.)

In block 15 in the diagram the hole continuity equation is solved for p. This equatio...