Monolithic integrated semiconductor means to reduce power dissip

Details Monolithic integrated semiconductor means to reduce power dissip Monolithic integrated semiconductor means to reduce power dissip

1987-05-05

1989-05-09

James, Andrew J.

Electrical transmission or interconnection systems

Nonlinear reactor systems

Parametrons

357 51, 357 15, 3072962, H01L 2702, H01L 2948

Patent

active

048293601

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention is based on monolithic integrated semiconductor arrangement of the type having a power diode whose anode forms an emitter and whose cathode forms a base of a parasitic substrate transistor.
Such monolithic integrated semiconductor means are well-known, particularly with respect to integrated ignition output stages of internal combustion engines and output stages of electrical generator controlling means. In order to connect the current and the voltage to inductive loads, thyristors and recovery diodes are connected in parallel with the inductive load. In monolithic integrated circuits, these power component parts form a parasitic transistor toward the substrate, which parasitic transistor allows an additional substrate current to flow. However, because of technical measures relating to manufacture the current gain of this parasitic transistor can only be adjusted to typically small values between 0.05 and 0.15. For the recovery diode of a conventional three-phase generator, which can only absorb currents of up to 5 amperes, this means a parasitic substrate current between approximately 0.25 amperes and 0.75 amperes.
In a generator with a nominal rating of 14 volts, for example, a light dynamo in a motor vehicle, this means an additional power loss of between 3.5 watts and 10.5 watts.


SUMMARY OF THE INVENTION

In contrast, the monolithic integrated semiconductor means, according to the invention, has the advantage that the power loss known from the prior art, which is caused by parasitic substrate currents, can be significantly reduced. This is achieved by means of increasing the collector path resistance of the parasitic transistor, which can accordingly reach saturation.
Particularly advantageous steps for increasing the collector path resistance of the parasitic transistor can include the doping of the substrate by means of suitable doping substances. This can be carried out from the back side of the substrate. Another advantageous possibility for increasing the collector path resistance is achieved in that the substrate region located below the parasitic transistor is isolated from the conductor which is at the substrate potential whereby an additional horizontal substrate path resistance is added to the collector path resistance. In substrates with back metallization, this can already be achieved by making use of the current blocking effect of a metal semiconductor blocking or barrier layer. However, this can also be achieved by means of applying an isolation layer prior to the application of the back metallization by means of oxidizing or nitriding the back side of the substrate.
An example of an embodiment of the invention is shown in the drawing and explained in more detail in the following description.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic circuit diagram of a power output stage for the connection of an inductive load;
FIG. 2 shows a cross section of a part of its structure in the form of a monolithic integrated semiconductor device; and
FIG. 3 shows a top view of the structure of FIG. 2.


DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 a n-p-n power transistor 1 is connected to an inductive load 2 by its collector, a recovery power diode 3 being connected in parallel with the inductive load 2. The recovery diode 3 simultaneously forms the emitter-base diode of a parasitic transistor 4 whose collector is connected to a substrate connection 42 via a collector path resistor 41. A first supply voltage terminal 5 is connected to the emitter of the power transistor 1, and a second supply voltage terminal 6 is connected to the inductive load 2 and to the cathode of the diode 3. The potential at the supply voltage terminal 5 corresponds to the ground potential 7 of the circuit arrangement. An additional substrate resistor 8 is connected in parallel with the interrupted substrate connection 42 as it will be explained later. The entire circuit arrangement is operated by a control circuit 9 which controls the base of the output-stage tra

REFERENCES:
patent: 3423647 (1969-01-01), Kurosawa et al.
patent: 4082571 (1978-04-01), Grant et al.
Bertotti et al, "New Voltage . . . Field", IEEE Trans. Consum. Elect., vol. CE-24, No. 1, Feb. 78.

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