SEMICONDUCTOR DEVICE DRIVING CIRCUIT AND METHOD OF TESTING THE SAME

A semiconductor device driving circuit includes: a driving circuit that drives a semiconductor device; an input circuit that gives a control signal to the driving circuit; a driving power source that drives output stages of the driving circuit; and a control power source provided independently of the driving power source, and which drives the input circuit. Only the driving voltage of the driving power source is reduced during a test and the current capability of the driving circuit is adjusted based on the current capabilities of the output stages in a pentode region.

EMBODIMENT FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are described below based on the drawings.

A technique prerequisite to the present invention is described first.

FIG. 6shows an example of the structure of a semiconductor device driving circuit according to the prerequisite technique.

As shown inFIG. 6, the semiconductor device driving circuit of the prerequisite technique includes a driving circuit2that drives a semiconductor device1, an input circuit3that shapes the waveform of an input signal and then inputs the resultant signal to the driving circuit2, and a driving power source13that drives the driving circuit2and the input circuit3.

The semiconductor device1is provided to drive a load arranged for example in a high-voltage circuit, and is composed of an N-channel MOSFET. The semiconductor device1can also be composed of a P-channel MOSFET.

The driving circuit2has output stages21to28. A combination of the output stages21and22, that of the output stages23and24, that of the output stages25and26, and that of the output stages27and28each form a CMOSFET (complementary MOSFET), and this CMOSFET functions as an inverter. The inverter is composed of an arbitrary number of stages.

In the semiconductor device driving circuit of the prerequisite technique, regarding testing and evaluating the current capability of the driving circuit2, the current capability of the driving circuit2cannot be evaluated directly during high-voltage operation of the driving circuit2that is normal operation thereof Hence, the current capability of the driving circuit2is evaluated based on the on-resistances of the output stages21to28measured in a triode region. This method of evaluation measures the on-resistances in a triode region. Thus, even if adjustment is made based on the evaluation, the current capability of the driving circuit2cannot become desirable characteristics (a design value of the current capability of the driving circuit2).

The present invention has been made to solve this problem, and is described in detail below.

First Preferred Embodiment

FIG. 1shows an example of the structure of a semiconductor device driving circuit according to a first preferred embodiment of the present invention.

As shown inFIG. 1, the semiconductor device driving circuit of the first preferred embodiment includes a driving circuit2that drives a semiconductor device1, an input circuit3that shapes the waveform of an input signal and inputs the resultant signal as a control signal to the driving circuit2, a driving power source4that drives output stages21to28(MOSFET output stages) of the driving circuit2, and a control power source5provided independently of the driving power source4and which drives the input circuit3.

A method of adjusting the current capability of the driving circuit2(method of testing a semiconductor device driving circuit) is described next.

First, to establish a standard for a semiconductor device driving circuit to be manufactured, correlation is examined in advance between current capability determined when the driving voltage of the driving power source4is low and that determined when the driving voltage thereof is a general driving voltage.

Next, during test of each manufactured semiconductor device driving circuit, current capability is measured when the driving voltage of the driving power source4is low. At this time, only the driving voltage of the driving power source4is reduced in the semiconductor device driving circuit. Thus, Vds (drain-to-source voltage) and Vgs (gate-to-source-voltage) are reduced by the same amount in each of the output stages21to28, making it possible to reduce the current capability of each of the output stages21to28while maintaining the output stages21and28in a pentode region.

Next, adjustment is made by trimming such that the current capability measured under the low driving voltage becomes desirable characteristics with respect to the previously examined current capability determined under the low driving voltage. At this time, current capability determined under the general driving voltage can be adjusted by taking the previously examined correlation into consideration. To be specific, based on the current capability measured under the low driving voltage, the current capability determined under the general driving voltage is adjusted by taking the previously examined correlation into consideration, thereby allowing adjustment of the current capability of the driving circuit2. A known technique such as laser trimming is applicable as an exemplary way of the trimming. More specifically, a fuse made of an aluminum line of a wiring pattern is cut, for example. This places the aluminum line in an open condition to allow switching between signals. To be specific, the output stages21and22are composed of a plurality of MOSFETs connected in parallel. To adjust the amount of current to flow into the output stages, it is determined if each of the MOSFETs is to operate (to receive an input signal and to be turned on or off), or is not to operate (always off independently of an input signal) by opening or shorting the aforementioned fuse. Then, the number of the MOSFETs to be connected in parallel in the output stages21and22is determined, thereby adjusting a current value.

As described above, in the first preferred embodiment, only the driving voltage of the driving power source4is reduced during the test, and the current capabilities of the output stages21and22of the driving circuit2are adjusted based on the current capabilities of the output stages21and28in a pentode region. This allows adjustment such that the current capability of the driving circuit2becomes desirable characteristics.

Second Preferred Embodiment

FIG. 2shows an example of the structure of a semiconductor device driving circuit according to a second preferred embodiment of the present invention.

As shown inFIG. 2, the semiconductor device driving circuit of the second preferred embodiment includes output stages61and62(test MOSFET output stages) corresponding to the output stages21and22(MOSFET output stages) respectively of the driving circuit2, and a test circuit6driven by the driving power source4.

In a layout, the output stages61and62of the test circuit6are paired with the output stages21and22of the driving circuit2respectively. The current capabilities of the output stages61and62are 1/n of the current capabilities of the output stages21and22respectively. A DC ammeter7to measure a current output from the test circuit6is connected to the test circuit6. The structure of the second preferred embodiment is the same in other respects as that of the first preferred embodiment, so that it will not be described here. Paring between output stages mentioned here means arranging the output stages in relation to each other (arranging the output stages in proximity to each other, for example) such that they receive the same process error.

A method of adjusting the current capability of the driving circuit2(method of testing a semiconductor device driving circuit) is described next. Referring toFIG. 2, the driving circuit2and the input circuit3perform the same operations as those of the first preferred embodiment. Control signals to be input to the gates of the output stages61and62of the test circuit6correspond to control signals to be input to the gates of the output stages21and22of the driving circuit2respectively. To be specific, the output stages61and62are driven by voltages common to those for the output stages21and22respectively.

First, the current capabilities of the output stages61and62are measured with the DC ammeter7.

Next, differences x[%] between the measured current capabilities of the output stages61and62and desirable characteristics are checked.

Then, the current capabilities of the output stages21and22are adjusted by trimming the aforementioned difference x[%]. To be specific, the current capabilities of the output stages21and22are adjusted based on the measured current capabilities of the output stages61and62and design values of the current capabilities of the output stages61and62. Current capability output from the driving circuit2is adjusted by adjusting the current capabilities of the output stages21and22.

As described above, in the second preferred embodiment, the current capabilities of the output stages21and22of the driving circuit2are adjusted based on the current capabilities of the output stages61and62of the test circuit6. This allows adjustment such that the current capability of the driving circuit2becomes desirable characteristics.

In the second preferred embodiment, a common power source is used for the test circuit6and the driving circuit2. Meanwhile, respective power sources may be prepared for the test circuit6and the driving circuit2, and only the test circuit6may be driven during the test.

Third Preferred Embodiment

FIG. 3shows an example of the structure of a semiconductor device driving circuit according to a third preferred embodiment of the present invention.

As shown inFIG. 3, the semiconductor device driving circuit of the third preferred embodiment includes an output stage81(first transistor) corresponding to the N-channel output stage22(N-channel MOSFET output stage) of the output stages21to28of the driving circuit2, and a current detecting circuit8(first current detecting circuit) driven by the driving power source4.

In a layout, the output stage81of the current detecting circuit8is paired with the output stage22of the driving circuit2. The current capability (sinking capability) of the output stage81is 1/n of the current capability (sinking capability) of the output stage22. In a layout, resistors R1and R2of the current detecting circuit8are paired with each other. A DC ammeter9to measure a current output from the current detecting circuit8is connected to the current detecting circuit8. The structure of the third preferred embodiment is the same in other respects as that of the first preferred embodiment, so that it will not be described here.

A method of adjusting the current capability of the driving circuit2(method of testing a semiconductor device driving circuit) is described next. Referring toFIG. 3, the driving circuit2and the input circuit3perform the same operations as those of the first preferred embodiment. A control signal to be input to the gate of the output stage81of the current detecting circuit8corresponds to a control signal to be input to the gate of the output stage22of the driving circuit2. To be specific, the output stage81is driven by a voltage common to that for the output stage22.

First, a short-circuit current is caused to flow in the output stage81of the current detecting circuit8. The short-circuit current is diverted through the resistors R1and R2, and current capability output from the current detecting circuit8is measured with the DC ammeter9.

Next, a difference x[%] between the measured current capability of the output stage81and desirable characteristics is checked.

Then, the current capability of the output stage22is adjusted by trimming the aforementioned difference x[%]. To be specific, the current capability of the output stage22is adjusted based on the measured current capability of the output stage81and a design value of the current capability of the output stage81. Current capability output from the driving circuit2is adjusted by adjusting the current capability of the output stage22.

As described above, in the third preferred embodiment, the current capability of the driving circuit2is adjusted based on the current capability of the output stage81of the current detecting circuit8. This allows adjustment such that the current capability of the driving circuit2becomes desirable characteristics.

In the third preferred embodiment, a common power source is used for the current detecting circuit8and the driving circuit2. Meanwhile, respective power sources may be prepared for the current detecting circuit8and the driving circuit2, and only the current detecting circuit8may be driven during the test.

Fourth Preferred Embodiment

FIG. 4shows an example of the structure of a semiconductor device driving circuit according to a fourth preferred embodiment of the present invention.

As shown inFIG. 4, the semiconductor device driving circuit of the fourth preferred embodiment includes an output stage101(second transistor) corresponding to the P-channel output stage21(P-channel MOSFET output stage) of the output stages21to28of the driving circuit2, and a current detecting circuit10(second current detecting circuit) driven by the driving power source4.

In a layout, the output stage101of the current detecting circuit10is paired with the output stage21of the driving circuit2. The current capability (sourcing capability) of the output stage101is 1/n of the current capability (sourcing capability) of the output stage21. In a layout, resistors R1and R2of the current detecting circuit10are paired with each other. A DC ammeter11to measure a current output from the current detecting circuit10is connected to the current detecting circuit10. The structure of the fourth preferred embodiment is the same in other respects as that of the first preferred embodiment, so that it will not be described here.

A method of adjusting the current capability of the driving circuit2(method of testing a semiconductor device driving circuit) is described next. Referring toFIG. 4, the driving circuit2and the input circuit3perform the same operations as those of the first preferred embodiment. A control signal to be input to the gate of the output stage101of the current detecting circuit10corresponds to a control signal to be input to the gate of the output stage21of the driving circuit2. To be specific, the output stage101is driven by a voltage common to that for the output stage21.

First, a short-circuit current is caused to flow in the output stage101of the current detecting circuit10. The short-circuit current is diverted through the resistors R1and R2, and current capability output from the current detecting circuit10is measured with the DC ammeter11.

Next, a difference x[%] between the measured current capability of the output stage101and desirable characteristics is checked.

Then, the current capability of the output stage21is adjusted by trimming the aforementioned difference x[%]. To be specific, the current capability of the output stage21is adjusted based on the measured current capability of the output stage101and a design value of the current capability of the output stage101. Current capability output from the driving circuit2is adjusted by adjusting the current capability of the output stage21.

As described above, in the fourth preferred embodiment, the current capability of the driving circuit2is adjusted based on the current capability of the output stage101of the current detecting circuit10. This allows adjustment such that the current capability of the driving circuit2becomes desirable characteristics.

In the fourth preferred embodiment, a common power source is used for the current detecting circuit10and the driving circuit2. Meanwhile, respective power sources may be prepared for the current detecting circuit10and the driving circuit2, and only the current detecting circuit10may be driven during the test.

Fifth Preferred Embodiment

FIG. 5shows an example of the structure of a semiconductor device driving circuit according to a fifth preferred embodiment of the present invention.

As shown inFIG. 5, a target to be driven by the semiconductor device driving circuit of the fifth preferred embodiment is an SiC device12. The structure and the operation of the fifth preferred embodiment are the same in other respects as those of the first preferred embodiment, so that they will not be described here.

Even if the SiC device12to be driven with a higher voltage and a higher current is a target to be driven by the semiconductor device driving circuit, the fifth preferred embodiment still realizes adjustment such that the current capability of the driving circuit2becomes desirable characteristics.

The preferred embodiments of the present invention can be combined freely, and each of the preferred embodiments can be modified or omitted where appropriate without departing from the scope of the invention.