M.S. Adler

The insulated gate transistor: A new three-terminal MOS-controlled bipolar power device

A new three-terminal power device, called the insulated gate transistor (IGT), with voltage-controlled output characteristics is described. In this device, the best features of the existing families of bipolar devices and power MOSFETs are combined to achieve optimal device characteristics for low-frequency power-control applications. Devices with 600-V blocking capability fabricated using a vertical DMOS process exhibit 20 times the conduction current density of an equivalent power MOSFET and five times that of an equivalent bipolar transistor operating at a current gain of 10. Typical gate turn-off times have been measured to range from 10 to 50 µs.

The insulated gate rectifier (IGR): A new power switching device

A new power semiconductor device called the Insulated Gate Rectifier (IGR) is described in this paper. This device has the advantages of operating at high current densities while requiring low gate drive power. The devices exhibit relatively slow switching speeds due to bipolar operation. The results of two dimensional computer modelling of the device structure are compared with measurements taken on devices fabricated with 600 volt forward and reverse blocking capability.

Theory and breakdown voltage for planar devices with a single field limiting ring

The use of one or more floating field limiting rings reduces the adverse effect of junction curvature on the breakdown voltage in planar devices. Although this has been known for some time, there has not been a way of accurately predicting the amount of improvement that can be achieved using field rings. In this paper, a computer algorithm is presented which makes it possible to perform field calculations on devices with floating field rings. In addition, a normalized curve is presented which shows the relative improvement that a single optimally placed field ring has on the breakdown voltage for any planar device. The basis of the construction of this curve is the use of a normalized radius of curvature which is a precise measure of the effect of curvature for any device. The theoretical predictions are compared with experiments for over 640 devices encompassing 16 different field ring locations. Good agreement is achieved between theory and experiment.

Accurate calculations of the forward drop and power dissipation in thyristors

Four-layer power thyristors are analyzed using exact numerical solutions of the full set of semiconductor device equations together with the heat-flow equation. Included in the analysis are the physical mechanisms of carrier-carrier scattering, Auger and SRH recombination, and band-gap narrowing. The experimental current-voltage curves for three-thyristor structures are compared with the theoretical predictions and are shown to be in good agreement. The limiting effects on device behavior of the physical mechanisms noted above, including heat-sink thermal impedance, are investigated over the range of device operating conditions. The distribution of power dissipation throughout the device is shown and compared with the distribution of recombination in the device. The theory of calculating power dissipation in a semiconductor is also discussed.

Measurement of heavy doping parameters in silicon by electron-beam-induced current

Limits on the magnitude of bandgap narrowing and Auger recombination in heavily phosphorus-diffused silicon layers ∼ 10²⁰cm^-3have been measured by electron-beam-induced current. It is determined that the slope of the bandgap narrowing versus doping must be nearly zero above 3 × 10¹⁹cm^-3to be consistent with previous data at lower doping levels. It is also shown that the low-level minority-carrier lifetime in these layers is consistent only with an Auger recombination coefficient<tex>C_{N} < 0.4 \times 10^{-31}</tex>cm⁶/s.

n-channel lateral insulated gate transistors: Part I&#8212;Steady-state characteristics

The basic physics of the steady-state characteristics of the lateral insulated gate transistor (LIGT) is discussed. Results from a tWo-dimensional computer simulation Of representative LIGT structures are presented. Several Structural and process enhancements to the basic LIGT structure to increase the current handling capability and suppress latchup are pointed out. Experimental results of the steady-state characteristics of a variety of LIGT test structures are presented and analyzed. The static latching aspect of LIGT is discussed insome detail. LIGT devices employing either a buried layer or surface shorts are shown to current limit rather than latching up.

Measurements of the p-n product in heavily doped epitaxial emitters

A new method is described for the measurement of the p-n product in the heavily doped epitaxial emitters of biopolar tansistors. Quantitative electron-beam-induced conductivity is used to determine the diffusion length in the emitter as well as the emitter thickness. I - V characterization and other standard methods are then used to measure the p-n product. The principal advantage of this method is that corrections for recombination in both the emitter and the base can be made based on measurements on identical regions of the same device. A key problem with other methods for determining the p-n product is their inability to separate changes in the p-n product (bandgap narrowing) from recombination, based on measurements taken on the same region of the device. New data for the p-n product at ∼ 1020.cm3free-carrier electron density are uniformly compared to other published data. The importance of the effective bandgap narrowing parameter both for comparing experimental data and for device modeling is stressed. Diffusion length measurements on the more heavily doped emitters yield lifetimes longer than expected based on published lifetimes determined by the decay of optical luminescence in heavily doped silicon. Possible reason for this difference are discussed and attributed to gettering in our samples.

Suppressing latchup in insulated gate transistors

Two-dimensional computer modeling of insulated gate transistor (IGT) structures has been used to demonstrate the suppression of latchup in the parasitic thyristor by increasing the p-base conductivity using a deep p+ diffusion in the device cells. Experimental verification of these modeling results has been performed with thyristor latching current density of over 1000 A per cm2achieved in 600-V devices at room temperature.

Theoretical basis for field calculations on multi-dimensional reverse biased semiconductor devices

Abstract In this report the theory and the computational methods used to perform numerical field calculations on reverse biased two-dimensional (or three-dimensional with circular symmetry) structures are fully described and completely justified. Finite difference methods are used to approximate Poissons equation and, together with a depletion region logic, solutions to semiconductor field problems are obtained without the need to solve the complete set of device equations. Two unique aspects of the methods are the depletion logic and the approach taken to handle dielectric interfaces.

Power semiconductor switching devices&#8212;A comparison based on inductive switching

In this paper, a comparison of the switching efficiency of MOSFETs Darlington transistors, field controlled thyristors (FCTs), and gate turn-off thyristors (GTOs) will be made for devices with breakdown voltages between 100 and 1000 V. The comparison is made as a function of switching frequency with a 50-percent duty cycle and for devices of the same area, carrying the same current. Conclusions are presented as to the most appropriate device for different combinations of breakdown voltage and switching frequency requirements.