Systems, methods, and non-transitory computer-readable media for dynamically assessing degradation of semiconductor devices

Abstract

A method for dynamically evaluating degradation of a semiconductor device is provided. The method includes determining a threshold voltage of the semiconductor device, calculating a leakage current limit based on the determined threshold voltage, measuring a leakage current of the semiconductor device, and comparing the measured leakage current to the calculated leakage current limit to evaluate degradation of the semiconductor device. The threshold voltage Vth is determined by inserting a sequence of sub-threshold drive pulses of different amplitudes into a drive signal applied to the device, such that the device operates in a sub-threshold region during the sub-threshold drive pulses. Dynamic threshold voltage and varying operating temperature can be taken into account when monitoring the leakage current. Better protection and more effective prevention of system failure can be obtained without affecting normal operation.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to evaluating reliability of semiconductor devices, and more particularly, to systems, methods, and non-transitory computer-readable media for dynamically evaluating reliability of gallium nitride (GaN) semiconductor devices. BACKGROUND

[0002] GaN-based switching devices have been widely used in high frequency power conversion systems due to low power loss and fast switching speed. Component degradation evaluation is an important measure to prevent system failure. One way to detect degradation of a transistor is to monitor its gate-source leakage current Igss and compare the measured value with a preset limit. When the measured value exceeds the limit, the transistor is considered to be degraded. Factors such as dynamic threshold voltage and varying operating temperature can affect the measurement of leakage current.

[0003] Devices from different production batches can have different threshold voltages, resulting in large variations in gate-source leakage current.

[0004] The preset gate-source leakage current limit can be too high to provide adequate protection against system failure.

[0005] Therefore, for certain applications in the field, it is desirable to dynamically monitor gate-source leakage current based on dynamic threshold voltage and varying operating temperature. Furthermore, since degradation is a long-term process, it is desirable to perform monitoring of gate-source leakage current occasionally along the operational lifetime of the device without causing any impact to normal operation. SUMMARY

[0006] According to a first aspect of the disclosure, there is provided a system for dynamically evaluating degradation of a gallium nitride (GaN)-based semiconductor device. The system comprises: a driver circuit configured to apply a drive signal to the DUT; a controller configured to control the driver to insert a sequence of sub-threshold drive pulses of different amplitudes into the drive signal such that the DUT operates in a sub-threshold region during the sub-threshold drive pulses; a first current sensing circuit configured to measure a drain-source current Ids of the device for each of the sub-threshold drive pulses to obtain a measured drain-source current sequence corresponding to the sequence of sub-threshold drive pulses; a second current sensing circuit configured to measure a leakage current of the device. The controller is further configured to: measure a gate-source voltage Vgs of the device for each of the sub-threshold drive pulses to obtain a measured gate-source voltage sequence corresponding to the sequence of sub-threshold drive pulses; receive the measured drain-source current sequence from the first current sensing circuit; determine a threshold voltage Vth of the device based on the measured gate-source voltage sequence and the measured drain-source current sequence; calculate a leakage current limit based on the determined threshold voltage; receive the measured leakage current from the second current sensing circuit; and compare the measured leakage current with the calculated leakage current limit to evaluate degradation of the device.

[0007] The system further comprises a temperature sensing circuit configured to measure an operating temperature of the device; and wherein the controller is further configured to: receive the measured operating temperature from the temperature sensing circuit; adjust the calculated leakage current limit based on the measured operating temperature; and compare the measured leakage current with the adjusted leakage current limit to evaluate degradation of the device.

[0008] According to a second aspect of the disclosure, there is provided a method for dynamically evaluating degradation of a gallium nitride (GaN)-based semiconductor device. The method comprises: determining a threshold voltage Vth of the device; calculating a leakage current limit based on the determined threshold voltage; measuring a leakage current of the device; and comparing the measured leakage current with the calculated leakage current limit to evaluate degradation of the device. The threshold voltage Vth is determined by: inserting a sequence of sub-threshold drive pulses of different amplitudes into a drive signal applied to the device such that the device operates in a sub-threshold region during the sub-threshold drive pulses; sensing a gate-source voltage Vgs of the device for each of the sub-threshold drive pulses to obtain a gate-source voltage sequence corresponding to the sequence of sub-threshold drive pulses; sensing a drain-source current Ids of the device for each of the sub-threshold drive pulses to obtain a drain-source current sequence corresponding to the sequence of sub-threshold drive pulses; and determining the threshold voltage Vth of the switching element based on the sensed gate-source voltage sequence and the sensed drain-source current sequence. The method further comprises: measuring an operating temperature of the device; adjusting the calculated leakage current limit based on the measured operating temperature;

[0009] and comparing the measured leakage current with the adjusted leakage current limit to assess degradation of the device.

[0010] According to a third aspect of the disclosure, there is provided a non-transitory computer readable medium storing a program causing a computer to execute the above-described method for dynamically assessing degradation of a gallium nitride (GaN)-based semiconductor device.

[0011] By means of the system, method and non-volatile computer readable storage medium provided by the invention, dynamic threshold voltages and varying operating temperatures can be taken into account when monitoring leakage current. Thus, better protection and more effective prevention of system failure can be obtained. Furthermore, since the sub-threshold drive pulses can be set to have a much shorter pulse width than the normal drive signal pulses, the impact of the assessment process on normal operation is negligible. BRIEF DESCRIPTION OF DRAWINGS

[0012] Aspects of the disclosure can be readily understood by considering the following detailed description in conjunction with the accompanying drawings. The drawings can not be drawn to scale. That is, the dimensions of the various features can be arbitrarily increased or decreased for the figure for clarity. Manufacturing processes and tolerances can cause differences between the processes as described in the disclosure and the actual system. Common reference numerals can be used throughout the figures and the embodiments to indicate the same or similar components.

[0013] Figure 1 A block diagram showing a system for dynamically assessing degradation of a semiconductor device according to an exemplary embodiment of the disclosure.

[0014] Figure 2 A circuit diagram showing a system for dynamically assessing degradation of a semiconductor device according to an exemplary embodiment of the disclosure.

[0015] Figures 3A to 3C An exemplary waveform of a drive signal pulse used in dynamically assessing degradation of a semiconductor device according to an exemplary embodiment of the disclosure.

[0016] Figure 4 A block diagram showing a system for dynamically assessing degradation of a semiconductor device according to another exemplary embodiment of the disclosure.

[0017] Figure 5 A circuit diagram showing a system for dynamically assessing degradation of a semiconductor device according to another exemplary embodiment of the disclosure.

[0018] Figure 6 A flowchart showing a method for dynamically assessing degradation of a semiconductor device according to one embodiment of the disclosure.

[0019] Figure 7 A flowchart showing steps of determining a threshold voltage according to one embodiment of the disclosure.

[0020] Figure 8 A schematic diagram showing a connection state between a computer-readable storage medium and a system for dynamically assessing degradation of a semiconductor device according to another exemplary embodiment of the disclosure. DETAILED DESCRIPTION

[0021] In the following description, preferred examples of the disclosure will be set forth as embodiments that should be viewed as illustrative rather than limiting.

[0022] Certain details can be omitted in order not to obscure the disclosure; however, the disclosure is written to enable practitioners of ordinary skill in the art to practice the teachings herein without undue experimentation.

[0023] It should be understood that other embodiments might be utilized, and structural changes might be made without departing from the scope of the present disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising" or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited by context, the terms "connected," "coupled," and "mounted," and variations thereof, are used broadly and encompass direct and indirect connections, couplings, and mountings.

[0024] Figure 1 and 2 A block diagram and a circuit diagram of a system 100 for dynamically assessing degradation of a semiconductor device 110 according to exemplary embodiments of the disclosure are shown. Referring to Figure 1 , the system 100 can include a driver circuit 120, a first current sense circuit 130, a second current sense circuit 140, a controller 150, and a temperature sense circuit 160.

[0025] The semiconductor device 110 can be a GaN transistor including a source terminal S, a gate terminal G, and a drain terminal D. In some embodiments, the GaN transistor is a high electron mobility transistor (HEMT). In some embodiments, the GaN transistor is an enhancement mode transistor. In some embodiments, the GaN switching device is a depletion mode transistor. In some embodiments, the semiconductor device is a high voltage vertical GaN switching device, and thus the type of semiconductor device 110 used in the disclosure is not limited thereto.

[0026] The driver circuit 120 has an input terminal electrically coupled to a driver control node 1501 of the controller 150 and an output terminal electrically coupled to the device 110 through the first current sense circuit 130.

[0027] The first current sensing circuit 130 has a first conductive terminal electrically coupled to the output terminal of the driver circuit 120; a second conductive terminal electrically coupled to the gate terminal G of the device 110; and a third conductive terminal electrically coupled to the leakage current sensing node 1502 of the controller 150.

[0028] The controller 150 further has a gate-source voltage sensing node 1503 electrically coupled to the gate terminal of the device 110.

[0029] The second current sensing circuit 140 has a first conductive terminal electrically coupled to the source terminal S of the device 110 and a second conductive terminal electrically coupled to the drain-source current sensing node 1504 of the controller 150.

[0030] The temperature sensing circuit 160 has conductive terminals electrically coupled to the temperature sensing node 1505 of the controller 150.

[0031] To dynamically assess the degradation of semiconductor device 110, controller 150 may be configured to generate control signal Vctrl to control driver circuit 120 to insert subthreshold drive pulse sequences Vsubth of different amplitudes into drive signal Vdrv applied to device 110 by driver circuit 120, such that device 110 operates in the subthreshold region during the subthreshold drive pulses.

[0032] The first current sensing circuit 130 can be configured to target the drain of each measuring device 110 in a subthreshold drive pulse.

[0033] -Source current Ids, to obtain the measured drain-source current sequence corresponding to the subthreshold drive pulse sequence.

[0034] The second current sensing circuit 140 may be configured to measure the leakage current Igss of the device 110. In some embodiments, the second current sensing circuit 140 may be configured to measure the leakage current Igss when the device 110 is operating at a standard operating voltage (e.g., 6 volts).

[0035] The controller 150 may be further configured to measure the gate-source voltage Vgs of each measuring device 110 in the subthreshold drive pulse to obtain a measured gate-source voltage sequence corresponding to the subthreshold drive pulse sequence; receive a measured drain-source current sequence from the first current sensing circuit 130; and based on the measured gate-source voltage sequence and the measured drain current sequence...

[0036] - The threshold voltage Vth of the source current sequence determination device 110.

[0037] In some embodiments, the controller 150 can be further configured to calculate a leakage current limit based on the determined threshold voltage; receive a measured leakage current from the second current sense circuit 140; and compare the measured leakage current to the calculated leakage current limit to assess degradation of the device 110.

[0038] The temperature sense circuit 160 can be configured to measure an operating temperature of the device 110.

[0039] In some embodiments, the controller 150 can be further configured to receive a measured operating temperature from the temperature sense circuit 160; adjust the calculated leakage current limit based on the measured operating temperature; and compare the measured leakage current to the adjusted leakage current limit to assess degradation of the device 110.

[0040] Reference Figure 2 The driver circuit 120 can include a first transistor Ql having a drain electrically connected to a voltage source VCC, a source electrically connected to an output terminal of the driver circuit, and a gate electrically connected to an input terminal of the driver circuit. The driver circuit can further include a second transistor Q2 having a drain electrically connected to the output terminal of the driver circuit, a source electrically connected to ground, and a gate electrically connected to the input terminal of the driver circuit.

[0041] The first current sense circuit 130 can include a first current sense resistor Rl having a first end electrically connected to a first conductive terminal of the first current sense circuit 130 and a second end electrically connected to a second conductive terminal of the first current sense circuit 130. The first current sense circuit 130 can further include a first current limiting resistor R2 having a first end electrically connected to the first end of the first current sense resistor Rl. The first current sense circuit 130 can further include a second current limiting resistor R3 having a first end electrically connected to the second end of the first current sense resistor Rl. The first current sense circuit 130 can further include an operational amplifier Al having a non-inverting terminal electrically connected to a second end of the first current limiting resistor R2, an inverting terminal electrically connected to a second end of the second current limiting resistor R3, and an output terminal electrically connected to a third conductive terminal of the first current sense circuit 130. The first current sense circuit 130 can further include a feedback resistor R4 having a first end electrically connected to the inverting terminal of the operational amplifier and a second end electrically connected to the output terminal of the operational amplifier.

[0042] The second current sense circuit 140 can include a second current sense resistor R5 having a first end electrically connected to a first conductive terminal of the second current sense circuit 140 and a second end electrically connected to a second conductive terminal of the second current sense circuit 140.

[0043] Preferably, each of the sub-threshold drive pulses has a pulse width that is much shorter than a pulse width of the drive signal.

[0044] For example, the pulse width of the sub-threshold drive pulses can be in a range from 1 / 1000 to 1 / 10 of the pulse width of the drive signal.

[0045] Figures 3A to 3C An exemplary waveform of drive signal pulses for use in dynamically evaluating degradation of a semiconductor device according to an exemplary embodiment of the disclosure. Referring to Figure 3A Each of the sub-threshold drive pulses is located at a rising edge of a drive signal pulse. Referring to Figure 3B Each of the sub-threshold drive pulses is located at a falling edge of a drive signal pulse. Referring to Figure 3C Each of the sub-threshold drive pulses is located between two drive signal pulses.

[0046] Figure 4 and 5 A block diagram and circuit diagram of a system 200 for dynamically evaluating degradation of a semiconductor device 110 according to another exemplary embodiment of the disclosure is shown. The system 200 is similar to the system 100, except that it has a different first current sense circuit 230. For brevity, Figure 1 and Figure 4 The same elements in

[0047] As shown in Figure 4 The first current sense circuit 230 has a first conductive terminal electrically coupled to an output terminal of the driver circuit 120 and a gate terminal of the device 110. That is, the output terminal of the driver circuit 120 is directly coupled to the device 110. The first current sense circuit 230 further has a second conductive terminal electrically coupled to a leakage current sense node 1502 of the controller 150; and a control terminal electrically coupled to a driver control node 1501 of the controller 150.

[0048] Referring to Figure 5The first current sense circuit 230 can have a third transistor Q3 having a drain electrically connected to the voltage source VCC, a source electrically connected to the second conductive terminal of the first current sense circuit 230, and a gate electrically connected to the control terminal of the first current sense circuit 230. The first current sense circuit 230 can further have a first current sense resistor R6 having a first end electrically connected to the first conductive terminal of the first current sense circuit 230 and a second end electrically connected to the second conductive terminal of the first current sense circuit 230.

[0049] Figure 6 A flowchart of a method for dynamically evaluating degradation of a semiconductor device according to one embodiment of the disclosure is shown. The method can include the following steps:

[0050] S602: determining a threshold voltage Vth of the device;

[0051] S604: calculating a leakage current limit based on the determined threshold voltage;

[0052] S606: measuring a leakage current of the device; and

[0053] S608: comparing the measured leakage current with the calculated leakage current limit to evaluate the degradation of the device.

[0054] Referring to Figure 7 In step S602, the threshold voltage Vth is determined by:

[0055] S6022: inserting a sequence of sub-threshold drive pulses of different amplitudes into a drive signal applied to the device such that the device operates in a sub-threshold region during the sub-threshold drive pulses;

[0056] S6024: sensing a gate-source voltage Vgs of the device for each of the sub-threshold drive pulses to obtain a sequence of gate-source voltages corresponding to the sequence of sub-threshold drive pulses;

[0057] S6026: sensing a drain-source current Ids of the device for each of the sub-threshold drive pulses to obtain a sequence of drain-source currents corresponding to the sequence of sub-threshold drive pulses; and

[0058] S6028: determining the threshold voltage Vth of the switching element based on the sensed sequence of gate-source voltages and the sensed sequence of drain-source currents.

[0059] Referring back to Figure 6 Optionally, the method can further include the following step:

[0060] S610: measuring an operating temperature of the device;

[0061] S612: adjusting the calculated leakage current limit based on the measured operating temperature; and

[0062] S614: comparing the measured leakage current to the adjusted leakage current limit to assess degradation of the device.

[0063] Referring to Figure 8 Embodiments of the present disclosure further provide a non-transitory computer-readable storage medium 800 containing a computer program 801. In some embodiments, the computer program 801, when executed by the controller 150 in the system 100 / 200, causes the system 100 / 200 to perform the above method for dynamically assessing degradation of a semiconductor device.

[0064] The embodiments are chosen and described so that best illustrates the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application in its various embodiments and with various modifications as are suited to the particular use contemplated. While the methods disclosed herein have been described with reference to particular operations performed in a particular order, it will be understood that these operations can be combined, sub-divided, or re-ordered to form equivalent methods without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of operations are not limiting. While the systems disclosed herein have been described with reference to particular structures, shapes, materials, compositions of matter, and relationships, these descriptions and illustrations are not intended to be limiting. Modifications can be made to adapt a particular situation to the teachings of the present disclosure. All such modifications are intended to be within the scope of claims.

Claims

1. A system for dynamically assessing degradation of a gallium nitride (GaN)-based semiconductor device, comprising: comprises: a driver circuit configured to apply a drive signal to the device; a controller configured to control the driver circuit to insert a sequence of sub-threshold drive pulses of different amplitudes into the drive signal such that the device operates in a sub-threshold region during the sub-threshold drive pulses; a first current sense circuit configured to measure a drain-source current Ids of the device for each of the sub-threshold drive pulses to obtain a measured drain-source current sequence corresponding to the sequence of sub-threshold drive pulses; a second current sense circuit configured to measure a leakage current of the device; wherein the controller is further configured to: measure a gate-source voltage Vgs of the device for each of the sub-threshold drive pulses to obtain a measured gate-source voltage sequence corresponding to the sequence of sub-threshold drive pulses; receive the measured drain-source current sequence from the first current sense circuit; determine a threshold voltage Vth of the device based on the measured gate-source voltage sequence and the measured drain-source current sequence; calculate a leakage current limit based on the determined threshold voltage; receive a measured leakage current from the second current sense circuit; and compare the measured leakage current to the calculated leakage current limit to assess degradation of the device. further comprising a temperature sense circuit configured to measure an operating temperature of the device; and wherein the controller is further configured to:

2. The system of claim 1, wherein, receive a measured operating temperature from the temperature sense circuit; adjust the calculated leakage current limit based on the measured operating temperature; and compare the measured leakage current to the adjusted leakage current limit to assess degradation of the device. each of the sub-threshold drive pulses is located at a rising edge of a drive signal pulse.

3. The system of claim 1 or 2, wherein, each of the sub-threshold drive pulses is located at a falling edge of a drive signal pulse.

4. The system of claim 1 or 2, wherein, each of the sub-threshold drive pulses is located between two drive signal pulses.

5. The system of claim 1 or 2, wherein, the driver circuit has an input terminal electrically coupled to a driver control node of the controller and an output terminal electrically coupled to the first current sense circuit.

6. The system of claim 1 or 2, wherein, the driver circuit comprises:

7. The system of claim 6, wherein, a first transistor having a drain electrically connected to a voltage source, a source electrically connected to the output terminal of the driver circuit, and a gate electrically connected to the input terminal of the driver circuit; and a second transistor having a drain electrically connected to the output terminal of the driver circuit, a source electrically connected to ground, and a gate electrically connected to the input terminal of the driver circuit. the first current sense circuit has a first conductive terminal electrically coupled to the output terminal of the driver circuit; a second conductive terminal electrically coupled to a gate terminal of the device; and a third conductive terminal electrically coupled to a leakage current sense node of the controller.

8. The system of claim 6, wherein, the first current sense circuit comprises: a first current sense resistor having a first end electrically connected to the first conductive terminal of the first current sense circuit and a second end electrically connected to the second conductive terminal of the first current sense circuit; and 9. The system of claim 8, wherein, a second current sense resistor having a first end electrically connected to the third conductive terminal of the first current sense circuit and a second end electrically connected to ground. ​ a first current sense resistor having a first end electrically connected to the first end of the first current sense resistor and a second end electrically connected to the second end of the first current sense resistor; a second current sense resistor having a first end electrically connected to the first end of the first current sense resistor and a second end electrically connected to the second end of the first current sense resistor; an operational amplifier having a non-inverting terminal electrically connected to a second end of the first current sense resistor, an inverting terminal electrically connected to a second end of the second current sense resistor, and an output terminal electrically connected to the third conductive terminal of the first current sense circuit; and a feedback resistor having a first end electrically connected to the inverting terminal of the operational amplifier and a second end electrically connected to the output terminal of the operational amplifier. the first current sense circuit has a first conductive terminal electrically coupled to the output terminal of the driver circuit and a gate terminal of the device; a second conductive terminal electrically coupled to a leakage current sense node of the controller; 10. The system of claim 6, wherein, and a control terminal electrically coupled to the driver control node of the controller. the first current sense circuit includes:

11. The system of claim 10, wherein, a third transistor having a drain electrically connected to the voltage source, a source electrically connected to the second conductive terminal of the first current sense circuit, and a gate electrically connected to the control terminal of the first current sense circuit; and a first current sense resistor having a first end electrically connected to the first conductive terminal of the first current sense circuit and a second end electrically connected to the second conductive terminal of the first current sense circuit. the controller has a gate-source voltage sense node electrically coupled to a gate terminal of the device. the second current sense circuit has a first conductive terminal electrically coupled to a source terminal of the device and a second conductive terminal electrically coupled to a drain-source current sense node of the controller.

12. The system of claim 6, wherein, the second current sense circuit includes a second current sense resistor having a first end electrically connected to the first conductive terminal of the second current sense circuit and a second end electrically connected to the second conductive terminal of the second current sense circuit.

13. The system of claim 6, wherein, the temperature sense circuit has a conductive terminal electrically coupled to a temperature sense node of the controller.

14. The system of claim 13, wherein, includes:

15. The system of claim 2, wherein, determining a threshold voltage Vth of the device; 16. A method for dynamically assessing degradation of a gallium nitride (GaN)-based semiconductor device, comprising: calculating a leakage current limit based on the determined threshold voltage; measuring a leakage current of the device; and comparing the measured leakage current to the calculated leakage current limit to assess degradation of the device; wherein the threshold voltage Vth is determined by: inserting a sequence of sub-threshold drive pulses of different amplitudes into a drive signal applied to the device such that the device operates in a sub-threshold region during the sub-threshold drive pulses; sensing a gate-source voltage Vgs of the device for each of the sub-threshold drive pulses to obtain a sequence of gate-source voltages corresponding to the sequence of sub-threshold drive pulses; sensing a drain-source current Ids of the device for each of the sub-threshold drive pulses to obtain a sequence of drain-source currents corresponding to the sequence of sub-threshold drive pulses; and and ​ ​ determining the threshold voltage Vth of the switching element based on the sensed gate-source voltage sequence and the sensed drain-source current sequence.

17. The method of claim 16, wherein, further comprising measuring an operating temperature of the device; adjusting the calculated leakage current limit based on the measured operating temperature; and comparing the measured leakage current to the adjusted leakage current limit to assess degradation of the device.

18. The method according to claim 16 or 17, characterized in that, the sub-threshold drive pulse sequence is inserted at a rising edge of the drive signal pulse sequence, respectively.

19. The method of claim 16 or 17, wherein, the sub-threshold drive pulse sequence is inserted at a falling edge of the drive signal pulse sequence, respectively.

20. The method of claim 16 or 17, wherein, the sub-threshold drive pulse sequence is inserted at a time gap between the drive signal pulse sequence, respectively.

21. A non-transitory computer readable medium storing a program causing a computer to perform the method of claim 16.

22. The non-transitory computer-readable medium of claim 21, wherein, the method further comprising: measuring an operating temperature of the device; adjusting the calculated leakage current limit based on the measured operating temperature; and comparing the measured leakage current to the adjusted leakage current limit to assess degradation of the device.

23. The non-transitory computer-readable medium of claim 21 or 22, wherein, the sub-threshold drive pulse sequence is inserted at a rising edge of the drive signal pulse sequence, respectively.

24. The non-transitory computer-readable medium of claim 21 or 22, wherein, the sub-threshold drive pulse sequence is inserted at a falling edge of the drive signal pulse sequence, respectively.

25. The non-transitory computer-readable medium of claim 21 or 22, wherein, the sub-threshold drive pulse sequence is inserted at a time gap between the drive signal pulse sequence, respectively.

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