Such semiconductor devices are also known as compensation devices. Such compensation devices are, for example, n- or p-channel MOS field effect transistors, diodes, thyristors, GTOs, or other components. In the following, however, a field effect transistor (also referred to briefly as “transistor”) is assumed as an example.
There have been various theoretical investigations spread over a long period of time concerning compensation devices (cf. U.S. Pat. No. 4,754,310 and U.S. Pat. No. 5,216,275) in which, however, specifically, improvements of the on-resistance RDS (on) but not of stability under current load, such as, in particular, robustness with regard to avalanche and short circuit in the high-current operation with high source-drain voltage, are sought.
Compensation devices are based on mutual compensation of the charge of n- and p-doped areas in the drift region of the transistor. The areas are spatially arranged such that the line integral above the doping along a line running vertical to the pn-junction in each case remains below the material-specific breakdown voltage (silicon: approximately 2×1012 cm−2). For example, in a vertical transistor, as is customary in power electronics, p-and n-columns or plates, etc. may be arranged in pairs. In a lateral structure, p- and n-conductive layers may be stacked on each other laterally alternating between a groove with a p-conductive layer and a groove with an n-conductive layer (cf. U.S. Pat. No. 4,754,310).
By means of the extensive compensation of the p- and n-doping, the doping of the current-carrying region (for n-channel transistors, the n-region; for p-channel transistors, the p-region) can be significantly increased, whereby, despite the loss in current-carrying area, a clear gain in on-resistance RDS(on) results. The blocking capability of the transistor depends substantially on the difference between the two dopings. Since, because of the reduction of the on-resistance, a doping higher by at least one order of magnitude of the current-carrying area is desirable, control of the blocking voltage requires controlled adjustment of the compensation level, which can be defined for values in the range ≦±10%. With a greater gain in on-resistance, the range mentioned becomes even smaller. The compensation level is then definable by(p-doping−n-doping)/n-dopingor bycharge difference/charge of one doping area.
Other definitions are, however, possible.
USPTO Backgrounds
USPTO Backgrounds