Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1999-06-24
2001-08-28
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S335000
Reexamination Certificate
active
06281549
ABSTRACT:
BACKGROUND INFORMATION
A MOSFET component in which a means is provided for protecting against the through-switching of a parasitic transistor is described in German Patent No. 30 39 803. A method is also described in German Patent No. 197 25 091 by which MOSFET components having a p-type trough region, in which a heavily n-type doped source region is embedded, are provided with a heavily p-type doped region within the p-type trough, with this p-type region extending all the way to the n-type region located beneath the p-type trough and/or stretching laterally beneath the source region. Providing such a heavily p-typed doped region is not suitable for mixed processes if one wishes to avoid additional manufacturing process steps. In addition, a heavily p-type doped region limits the ability to scale down the component.
SUMMARY OF THE INVENTION
An object of the present invention is to provide reliable protection against the through-switching of a parasitic transistor, which would inevitably lead to irreversible damage to the component due to high currents, using simple means and at no additional expense.
It is particularly advantageous to scale down the component so that, for example, the p-type trough has a depth of less than 1 &mgr;m. This produces a submicron MOS arrangement which can be operated with the usual threshold voltages, but with drain-to-source voltages of only 40 V instead of 60-80 V. With methods according to the related art, such compact, space-saving components make it difficult or even impossible to protect against parasitic bipolar effects. If the threshold voltage is set to the usual values even in the submicron arrangement, a higher doping of the p-type trough is necessary. In spite of this higher p-type doping, the resistance of the resistor formed by p-type regions of the p-type trough beneath the source region (referred to below as the pass-under resistor) increases, thus heightening the susceptibility to parasitic bipolar effects, since the space-charge effect between the p-type trough and the underlying n-type region becomes more significant in very shallow p-type troughs. However, protective measures, such as the deep p-type diffusions known from the related art, cannot be used with scaled-down p-type troughs that are less than 1 micrometer deep. A compact component that is reliably protected against through-switching of the parasitic transistor can be provided only by combining a submicron structure with a p-type path connected in parallel to the pass-under resistor.
A design based on DMOS technology allows the component to be further miniaturized, at the same time increasing its current carrying capacity. Particularly in the case of DMOS components, there is great danger of the minority charge carriers generated in the areas of the n-type region adjacent to the channel regions passing through the narrow channel region and flowing through the pass-under resistor. A p-type conductive path that is connected in parallel to the pass-under resistor is therefore especially advantageous, particularly in the case of DMOS components.
When using lateral components, in particular, high field strengths can also be expected in the areas of the n-type region adjacent to the channel regions, thus producing a large number of holes in these regions and resulting in a high hole current flowing through the pass-under resistor. The parallel-connected path can therefore be used to advantage particularly in the case of lateral components.
By selecting the area ratio between the source and auxiliary regions, the component can be set to a low drain-to-source starting resistance or to a highly efficient extraction of the minority charge carriers, which are undesirable because they produce parasitic effects, depending on the application.
The arrangement according to the present invention can be used in the same manner with reversed doping.
REFERENCES:
patent: 3412297 (1968-11-01), Amlinger
patent: 4803532 (1989-02-01), Mihara
patent: 30 93 803 (1981-05-01), None
patent: 197 25 091 (1998-12-01), None
patent: 0 841 702 (1998-05-01), None
patent: 56-88363 (1981-07-01), None
patent: 1-140773 (1989-06-01), None
patent: 11-74517 (1999-03-01), None
patent: 11-330451 (1999-11-01), None
patent: 11-307763 (1999-11-01), None
Crane Sara
Kenyon & Kenyon
Robert & Bosch GmbH
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