JP2019052855A - Thermal resistance measuring apparatus and thermal resistance measuring method - Google Patents

Abstract

To achieve high precision thermal resistance measurement with a simple configuration.SOLUTION: A thermal resistance measuring apparatus according to an embodiment which includes a first terminal as a control terminal, a second terminal and a third terminal, is the thermal resistance measuring apparatus for measuring the thermal resistance of a semiconductor element, which can flow a bidirectional current between the second terminal and the third terminal according to the control state of the first terminal, and includes: a table that stores in advance the relationship between a voltage between the second terminal and the third terminal and a junction temperature of the semiconductor element in a state in which current flows from the second terminal to the third terminal; a voltage measurement unit for measuring the voltage between the second and third terminals in a state in which the measuring current flows from the third terminal to the second terminal before and after heating by heating the semiconductor element by the heating current flowing from the second terminal to the third terminal; and a thermal resistance calculation unit that calculates a thermal resistance value of the semiconductor element on the basis of the table and a voltage difference before and after heating measured by the voltage measurement unit.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a thermal resistance measurement device and a thermal resistance measurement method.

Conventionally, thermal resistance measurement has been performed to measure the heat dissipation capability of a semiconductor element.
For example, when measuring the thermal resistance of a MOSFET as a semiconductor element, the gate voltage is controlled so that the power consumption of the MOSFET is constant, and the thermal resistance is measured using the temperature characteristic of the gate voltage threshold, and the MOSFET The ΔVds method is used in which the gate voltage is controlled to be constant and the thermal resistance is measured using the temperature characteristics of the on-resistance of the MOSFET.

JP 2007-221922 A

By the way, when the thermal resistance measurement is performed using the above-described ΔVgs method and ΔVds method, the element temperature measurement current before and after element heating by the ΔVgs method and the heating current for element heating by the ΔVds method are both positive. In addition, since current flows in the same direction, if the current does not converge due to oscillation or the like immediately after heating the element, it is difficult to determine which current it is.
For this reason, in order to wait for convergence, it is necessary to take a long time from heating to measurement, and the cooling of the element progresses, the temperature of the element to be measured deviates from the actual element temperature, and an error occurs. There was a risk of occurrence.
Then, this invention is providing the thermal resistance measuring apparatus and the thermal resistance measuring method which can aim at high precision of thermal resistance measurement with a simple structure.

A thermal resistance measurement apparatus according to an embodiment of the present invention includes a first terminal, a second terminal, and a third terminal as control terminals, and the control state of the first terminal is between the second terminal and the third terminal. A thermal resistance measuring device for measuring the thermal resistance of a semiconductor element capable of flowing a corresponding current bidirectionally, the second terminal in a state in which a current flows from the second terminal toward the third terminal- A table in which the relationship between the voltage between the third terminals and the junction temperature of the semiconductor element is stored in advance, the semiconductor element is heated by a heating current flowing from the second terminal toward the third terminal, and the third terminal before and after the heating. Based on the voltage measurement unit that measures the voltage between the second terminal and the third terminal in a state where the measurement current flows from the first terminal to the second terminal, the voltage difference before and after heating measured by the voltage measurement unit, and the table Thermal resistance value of semiconductor element Comprising a heat resistance calculating unit that calculates a.
According to the above configuration, since the heating current and the measurement current can be easily identified, the time from heating to measurement can be shortened, and the accuracy of the thermal resistance measurement can be improved. .

In the thermal resistance measurement apparatus according to the embodiment, a first constant current circuit for flowing a measurement current, a second constant current circuit for flowing a heating current, a temperature measurement current, and the heating current flow. The second voltage measuring circuit for measuring the voltage between the first terminal and the third terminal in the state of being, the voltage measured by the second voltage measuring circuit, the current value of the measuring current, and the current value of the heating current And a power consumption calculation unit that calculates power consumption of the semiconductor element, and the thermal resistance calculation unit may calculate the thermal resistance value of the semiconductor element based on the power consumption.
According to the above configuration, it is possible to increase the accuracy of the thermal resistance measurement with a simple configuration.

Further, in the thermal resistance measurement apparatus according to the embodiment, a terminal protection diode is provided in which a cathode is connected to the first terminal and an anode is connected to the third terminal so that the applied voltage of the first terminal does not exceed a predetermined voltage. You may make it prepare.
According to the above configuration, it is possible to increase the accuracy of the thermal resistance measurement while reliably protecting the semiconductor element to be measured for thermal resistance.
In the thermal resistance measurement apparatus according to the embodiment, the semiconductor element is a GaN semiconductor element, the first terminal is a gate terminal, the second terminal is a drain terminal, and the third terminal is a source terminal. Also good.
According to the above configuration, even in a GaN semiconductor element that does not have a body diode (parasitic diode), it is possible to improve the accuracy of thermal resistance measurement with a simple configuration.

A thermal resistance measurement method according to an embodiment of the present invention includes a first terminal, a second terminal, and a third terminal as control terminals, and a current corresponding to a control state of the first terminal between the second terminal and the third terminal. There is a thermal resistance measurement method executed by a thermal resistance measurement device that measures the thermal resistance of a semiconductor element that can flow in both directions, the thermal resistance measurement device being directed from the second terminal toward the third terminal. A table for storing in advance the relationship between the voltage between the second terminal and the third terminal and the junction temperature of the semiconductor element in a state where current is flowing, and for heating that flows from the second terminal toward the third terminal A voltage measurement process in which the semiconductor element is heated by a current, and a voltage between the second terminal and the third terminal is measured in a state where only a measurement current flows from the third terminal to the second terminal before and after the heating; Measured during the voltage measurement process Comprising the voltage difference calculating step of calculating the voltage difference before and after heating, and the heat resistance calculation step of calculating the thermal resistance of the semiconductor element based on the voltage difference and the table, the.
According to the above configuration, since the heating current and the measurement current can be easily identified, the time from heating to measurement can be shortened, and the accuracy of the thermal resistance measurement can be improved. .

FIG. 1 is an explanatory diagram of a schematic configuration of a thermal resistance measurement apparatus according to the first embodiment. FIG. 2 is a flowchart of thermal resistance measurement operation processing according to the embodiment. FIG. 3 is an explanatory diagram of the thermal resistance measurement operation of the embodiment. FIG. 4 is an explanatory diagram of the relationship between the normalized drain-source voltage and the junction temperature. FIG. 5 is a schematic configuration explanatory diagram of a thermal resistance measurement apparatus according to the second embodiment. FIG. 6 is a schematic configuration explanatory diagram of a thermal resistance measurement apparatus according to the third embodiment.

  Hereinafter, exemplary embodiments of the present invention are disclosed. The configuration of the embodiment shown below and the operations, results, and effects brought about by the configuration are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments, and at least one of various effects based on the basic configuration and derivative effects can be obtained. .

First, prior to the description of the embodiment, the principle of the embodiment will be described.
In measuring the thermal resistance of a GaN transistor as a semiconductor device using gallium nitride (GaN), the applicants applied a negative bias between the drain terminal and the source terminal of the GaN transistor and the source-drain voltage Vsd and the source. It has been found that the relationship between the source-drain current Isd flowing from the terminal toward the drain terminal is temperature dependent.

  Therefore, in the embodiment, the current for heating the GaN transistor is caused to flow from the drain terminal side to the source terminal side by applying a positive bias, and when a current for measurement at the time of measuring the thermal resistance is passed, a negative bias is applied. By applying the current to the drain terminal side from the source terminal side, the heating current and the measurement current can be easily identified, and the measurement accuracy can be improved.

[1] First Embodiment FIG. 1 is an explanatory diagram of a schematic configuration of a thermal resistance measuring apparatus according to a first embodiment.
In FIG. 1, a case of a GaN transistor TR as an example of a semiconductor element to be measured for thermal resistance will be described.
In FIG. 1, a GaN transistor TR as a semiconductor element to be measured for thermal resistance includes a first terminal T1 (= gate terminal g), a second terminal T2 (= drain terminal d), and a third terminal T3 (= source terminal s). ).

  The thermal resistance measurement apparatus 10 of the first embodiment includes a constant current source for measurement current 11 having one end connected to the second terminal T2 of the GaN transistor TR, which is a semiconductor element to be measured for thermal resistance, and the other end grounded. A heating power source 12 for supplying heating power to the GaN transistor TR, and a heating switch for connecting one end to the second power source T2 and the other end to the heating power source 12 to connect the heating power source 12 to the GaN transistor TR 13 and the anode is connected to the second terminal T2 of the GaN transistor TR, the cathode is connected to the first terminal T1 of the GaN transistor TR, and one end is connected to the anode of the diode 14 for backflow prevention. A bias resistor 15 for applying a bias voltage with the other end grounded, and a heating current constant having one end connected to the third terminal T3 and the other end grounded. A current source 16; a gate-source voltage measuring device 17 for measuring a gate-source voltage Vgs which is a voltage between the first terminal T1 and the third terminal T3; a second terminal T2 and a third terminal T3; A drain-source voltage measuring device 18 for measuring a drain-source voltage Vds, which is a voltage between the two.

Next, the thermal resistance measurement operation in the first embodiment will be described.
FIG. 2 is a flowchart of thermal resistance measurement operation processing according to the embodiment.
FIG. 3 is an explanatory diagram of the thermal resistance measurement operation of the embodiment.

When performing the thermal resistance measurement, first, the thermal resistance measurement device 10 enters a measurement standby state in the first phase PH1 (= time t0 to time t1) (step S11).
Specifically, in the first phase PH1, which is the period from time t0 to time t1 in FIG. 3, adjustment is performed so that the heating power source 12 is activated and a constant heating voltage can be applied.

  In this case, the temperature characteristic and temperature coefficient of the voltage between the third terminal T3 and the second terminal with respect to the current flowing from the third terminal T3 to the second terminal when measuring the thermal resistance of the GaN transistor TR, that is, with respect to the source-drain current Isd. It is assumed that the temperature characteristic of the source-drain voltage Vsd and its temperature coefficient K (K factor) are acquired in advance.

  Subsequently, in the second phase PH2 (= time t1 to time t2), the thermal resistance measurement apparatus 10 uses the measurement current constant current source 11 to move from the third terminal T3 to the second terminal T2 of the GaN transistor TR. That is, a measurement current Im flows from the source terminal s to the drain terminal d of the GaN transistor TR.

  When a predetermined time Δt1 when the current amount of the measurement current I becomes stable after the measurement current Im starts to flow, the drain-source voltage Vds is measured by the drain-source voltage measuring instrument 18 (step S1). S12).

FIG. 4 is an explanatory diagram of the relationship between the normalized drain-source voltage and the junction temperature.
The measured drain-source voltage Vds is defined as a voltage Vm1.
The relationship between the drain-source voltage Vds and the junction temperature at this time is as shown in FIG.
Then, after measuring the drain-source voltage Vds, the measurement current Im is kept flowing.

  Here, the amount of current Im for measurement is set to a minute current that does not heat the GaN transistor TR, which is a semiconductor element, that is, does not change the temperature of the GaN transistor TR.

Further, in the thermal resistance measuring apparatus 10, the heating switch 13 is turned on (closed) in the third phase PH3 (= time t2 to time t3).
As a result, the predetermined voltage VH is applied to the second terminal T2 of the GaN transistor TR, that is, the drain terminal d.

As a result, the voltage VH−Vf obtained by subtracting the forward voltage Vf of the backflow prevention diode from the voltage VH is applied to the first terminal T1 of the GaN transistor TR, that is, the gate terminal g, via the backflow prevention diode 14. .
When the voltage applied to the first terminal T1 of the GaN transistor TR becomes equal to or higher than the threshold voltage of the GaN transistor TR, the GaN transistor TR is turned on (closed state).

  At this time, the voltage between the first terminal T1 and the third terminal T3 of the GaN transistor TR, that is, the gate-source voltage Vgs is measured by the gate-source voltage measuring instrument 17 (step S13).

  At the time of measuring the gate-source voltage Vgs, the heating current IH flows from the drain terminal d toward the source terminal s, and the measurement current Im flows from the source terminal s toward the drain terminal d. Therefore, effectively, the maximum current flowing from the drain terminal d, which is the second terminal T2, to the source terminal s, which is the third terminal T3, is IH−Im which is the difference between these currents.

Therefore, the power consumption PW in the GaN transistor TR is obtained by the following equation (step S14).
PW = VH · (IH-Im)

Further, in the thermal resistance measuring device 10, the heating switch 13 is turned off (opened) in the fourth phase PH4 (= time t3 to time t4).
As a result, voltage application by the heating power supply 12 to the GaN transistor TR is cut off, so that the potential of the first terminal T1, that is, the gate terminal g, is at the ground level via the bias resistor 15, and the first transistor GaN transistor TR When the voltage applied to the terminal T1 becomes less than the threshold voltage of the GaN transistor TR, the GaN transistor TR is turned off (opened).

Then, the current flowing from the second terminal T2 to the third terminal T3 converges to the measurement current Im.
Thereafter, the temperature drop due to the stop of heating can be ignored (within a predetermined range), and when a predetermined time Δt2 at which the current amount of the measurement current Im can be regarded as being stable has elapsed, the drain-source voltage Vds is reduced to the drain-source voltage. The voltage is measured by the source-to-source voltage measuring device 18. The measured drain-source voltage Vds is set as the voltage Vm2 (step S15).

At this time, since the junction temperature of the GaN transistor TR is increased by the heating current IH,
Vm1 ≠ Vm2 (∴ | Vm1-Vm2 | ≠ 0)
It has become.

Therefore, the voltage difference ΔVm, which is the difference between the voltage Vm1 and the voltage Vm2, is calculated by the following equation (step S16).
ΔVm = Vm1-Vm2

Thereby, based on the differential voltage ΔVm and the temperature coefficient K (K factor), the junction temperature which is the difference between the junction temperature (Tj1) of the GaN transistor TR before heating and the junction temperature (Tj2) of the GaN transistor TR after heating. The difference ΔTj is calculated by the following equation (step S17).
ΔTj = Tj1-Tj2

Based on the junction temperature difference ΔTj and the power consumption PW, the thermal resistance RT of the GaN transistor TR is calculated by the following equation (step S18).
RT = ΔTj / PW

  In the fifth phase PH5 (= time t4 to time t5), the thermal resistance measuring device 10 is in a standby state, the GaN transistor TR is gradually cooled by heat radiation, and the second terminal T2 to the third terminal T3. The drain-source voltage Vds, which is the voltage between them, gradually converges to the voltage Vm1 (step S19).

  In the thermal resistance measuring apparatus 10, in the sixth phase PH6 (= time t5 to hour time t6), the heating power supply 12 is turned off (step S20), and the thermal resistance measurement ends.

As described above, according to the first embodiment, the measurement current Im used for the temperature measurement (Vds method) before and after the heating of the semiconductor device flows from the source terminal s to the drain terminal d side, and the heating current Since IH flows from the drain terminal d to the source terminal s side, it can be easily discriminated whether it is the measurement current Im or the heating current IH, and the temperature of the semiconductor device after heating can be determined within a desired temperature range. The junction temperature can be measured in the interior, and the accuracy of the thermal resistance measurement can be improved.
In addition to the configuration of the conventional semiconductor device, a simple configuration in which a constant current source (a constant current source for measurement and a constant current source for heating) and a heating switch are provided can be provided.

[2] Second Embodiment FIG. 5 is an explanatory diagram of a schematic configuration of a thermal resistance measuring apparatus according to a second embodiment.
In FIG. 5, the thermal resistance measuring device 10 </ b> A of the second embodiment is different from the thermal resistance measuring device 10 of the first embodiment of FIG. 1 in that the cathode of the backflow preventing diode 14 and the bias resistor 15 are connected at the cathode. Is connected, and a gate protection diode (zener diode) 21 whose anode is grounded is connected.
It is known that the breakdown voltage (gate breakdown voltage) of the gate terminal g is low when the GaN transistor TR as a semiconductor element is compared with a MOSFET based on silicon (Si).

  Therefore, when a voltage equal to or higher than the protection voltage is applied to the gate terminal g in order to protect the gate terminal g which is the first terminal T1, the gate protection diode (zener diode) 21 is connected to the gate terminal g of the GaN transistor TR. Operates so as to keep the voltage at a constant (kener voltage).

  Therefore, according to the second embodiment, the gate terminal g which is the first terminal T1 of the GaN transistor TR can be reliably protected.

[3] Third Embodiment FIG. 6 is a schematic configuration explanatory diagram of a thermal resistance measurement apparatus according to a third embodiment.
In FIG. 6, the thermal resistance measurement device 10 </ b> B of the third embodiment is different from the thermal resistance measurement device 10 of the first embodiment of FIG. 1 in that a measurement current constant current source 11, a heating power source 12, and a heating switch 13. And a controller 22 for controlling the heating current constant current source 16 and receiving the measurement results from the gate-source voltage measuring device 17 and the drain-source voltage measuring device 18 and performing a thermal resistance measurement process. is there.

According to this configuration, the same effects as those of the first embodiment can be obtained, and a series of operations in the thermal resistance measurement described in the first embodiment can be automatically performed.
Therefore, the thermal resistance can be automatically measured with a simple configuration with high accuracy.

Although the embodiments of the present invention have been described, these embodiments are presented as examples, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
For example, in the above description, a GaN transistor has been described as a semiconductor element. However, the present invention can be similarly applied to other semiconductor elements such as a SiC transistor.

  DESCRIPTION OF SYMBOLS 10, 10A, 10B ... Thermal resistance measuring apparatus, 11 ... Constant current source for measurement currents, 12 ... Heating power supply, 13 ... Heating switch, 14 ... Backflow prevention diode, 15 ... Bias resistance, 16 ... Constant for heating current Current source, 17 ... gate-source voltage measuring device (second voltage measuring unit), 18 ... drain-source voltage measuring device (voltage measuring unit), 21 ... gate protection diode, 22 ... controller, Vds ... drain- Source-to-source voltage, Vgs ... Gate-source voltage, Im ... Measurement current, IH ... Heating current, PW ... Power consumption, T1 ... First terminal (gate terminal g), T2 ... Second terminal (drain terminal d) , T3 ... third terminal to third terminal, TR ... GaN transistor (semiconductor element), Vm1 ... voltage (drain-source voltage before heating), Vm2 ... voltage (drain-source voltage after heating) ΔTj: Junction temperature difference, ΔVm: Difference voltage.

Claims (5)

A semiconductor device having a first terminal, a second terminal, and a third terminal as control terminals, and capable of flowing a current according to a control state of the first terminal in a bidirectional manner between the second terminal and the third terminal. A thermal resistance measuring device for measuring the thermal resistance of an element,
A table that stores in advance a relationship between a voltage between the second terminal and the third terminal and a junction temperature of the semiconductor element in a state in which a current flows from the second terminal toward the third terminal;
The semiconductor element is heated by a heating current flowing from the second terminal toward the third terminal, and a measurement current flows from the third terminal toward the second terminal before and after the heating. A voltage measuring unit for measuring a voltage between the second terminal and the third terminal;
A thermal resistance calculation unit that calculates a thermal resistance value of the semiconductor element based on the voltage difference before and after the heating measured by the voltage measurement unit and the table;
Thermal resistance measuring device with A first constant current circuit for flowing the measurement current;
A second constant current circuit for flowing the heating current;
A second voltage measuring circuit for measuring a voltage between the first terminal and the third terminal in a state where the temperature measurement current and the heating current are flowing;
A power consumption calculation unit that calculates power consumption of the semiconductor element based on the voltage measured by the second voltage measurement circuit, the current value of the measurement current, and the current value of the heating current;
The thermal resistance calculator calculates a thermal resistance value of the semiconductor element based on the power consumption;
The thermal resistance measuring device according to claim 1. A cathode is connected to the first terminal, an anode is connected to the third terminal, and a terminal protection diode is provided to prevent an applied voltage of the first terminal from exceeding a predetermined voltage.
The thermal resistance device according to claim 1 or 2. The semiconductor element is a GaN semiconductor element,
The first terminal is a gate terminal;
The second terminal is a drain terminal;
The third terminal is a source terminal;
The thermal resistance measuring device according to any one of claims 1 to 3. A semiconductor device having a first terminal, a second terminal, and a third terminal as control terminals, and capable of flowing a current according to a control state of the first terminal in a bidirectional manner between the second terminal and the third terminal. There is a thermal resistance measurement method executed by a thermal resistance measurement device that measures the thermal resistance of an element,
The thermal resistance measuring apparatus previously determines a relationship between a voltage between the second terminal and the third terminal and a junction temperature of the semiconductor element in a state where a current flows from the second terminal toward the third terminal. With a memorized table,
The semiconductor element is heated by a heating current flowing from the second terminal toward the third terminal, and only a measurement current flows from the third terminal toward the second terminal before and after the heating. A voltage measuring process of measuring a voltage between the second terminal and the third terminal;
A voltage difference calculation process for calculating a voltage difference measured before and after the heating measured in the voltage measurement process;
A thermal resistance calculation step of calculating a thermal resistance value of the semiconductor element based on the voltage difference and the table;
A method for measuring thermal resistance.

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