CN112098790B - MIS-HEMT (metal insulator semiconductor-high electron mobility transistor) -based energy distribution testing method and system for boundary trap - Google Patents

MIS-HEMT (metal insulator semiconductor-high electron mobility transistor) -based energy distribution testing method and system for boundary trap Download PDF

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CN112098790B
CN112098790B CN202010776999.4A CN202010776999A CN112098790B CN 112098790 B CN112098790 B CN 112098790B CN 202010776999 A CN202010776999 A CN 202010776999A CN 112098790 B CN112098790 B CN 112098790B
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hemt
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trap
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CN112098790A (en
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高汭
贺致远
陈义强
林晓玲
路国光
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China Electronic Product Reliability and Environmental Testing Research Institute
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/26—Testing of individual semiconductor devices
    • G01R31/2601—Apparatus or methods therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/26—Testing of individual semiconductor devices
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    • G01R31/2621—Circuits therefor for testing field effect transistors, i.e. FET's

Abstract

The invention relates to an MIS-HEMT boundary trap energy distribution testing method and system. Wherein the method comprises: applying positive voltage stress to the grid of the MIS-HEMT to charge until the charging is finished; fully discharging the MIS-HEMT through a plurality of discharge processes, wherein the following steps are performed in each discharge process: reducing a forward voltage stress applied to a gate of the MIS-HEMT; monitoring the discharge process of the MIS-HEMT by adopting a spot-Id sense technology to obtain the current of the MIS-HEMT; and determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount.

Description

MIS-HEMT (metal insulator semiconductor-high electron mobility transistor) -based energy distribution testing method and system for boundary trap
Technical Field
The invention relates to the technical field of semiconductor devices, in particular to an MIS-HEMT based energy distribution test system for a boundary trap.
Background
Wide bandgap semiconductor materials typified by GaN are new semiconductor materials that have been rapidly developed in recent years, following first-generation semiconductor materials typified by silicon and second-generation semiconductor materials typified by gallium arsenide (GaAs). However, the technology for manufacturing the power device by using the GaN material is still not mature enough at present, and the GaN material cannot replace a silicon-based power device on a large scale. The reason is mainly as follows: firstly, a common structure of a traditional GaN power device is a Metal-Insulator-Semiconductor High Electron Mobility Transistor (MIS-HEMT), and the traditional MIS-HEMT devices are depletion mode (D-mode) devices, so that when the power device fails in a power circuit, the grid voltage can not turn off the device; secondly, the leakage current of the gate of the conventional Schottky MIS-HEMT is large, which causes a large amount of energy loss. The MIS-HEMT device is a novel structure capable of effectively solving the two problems, the grid leakage is well controlled by inserting a layer of insulating medium between the grid and the 2DEG, and the preparation of an enhanced (E-Mode) device can be realized by adopting a groove grid structure [2]; however, the insulating dielectric layer can introduce a large amount of boundary traps (BorderTraps) into the MIS-HEMT, so that the reliability of the device is poor, and the device becomes a bottleneck restricting the large-scale application of the device. The research on the energy distribution of the boundary trap in the GaN MIS-HEMT has very important practical significance on MIS-HEMT process optimization and reliability improvement.
In the existing trap energy distribution test extraction technology, the discharge-based multi-pulse technology for rapid pulse measurement is difficult to cover the rated working voltage range of a power device, and the technology for extracting the trap position and energy distribution based on simulation and direct current slow measurement cannot extract a rapidly recoverable trap, so that the technology is not suitable for extracting the boundary trap energy distribution of GaN MIS-HEMT.
Disclosure of Invention
Based on the method, the invention provides the MIS-HEMT-based energy distribution test method and the MIS-HEMT-based energy distribution test system for the boundary trap, so that the requirement of measuring range is met, the test time is shortened, the escape of the rapidly recoverable trap is reduced, and the measurement accuracy is improved.
The invention provides an MIS-HEMT (High Electron Mobility Transistor) based energy distribution test method for boundary traps, which comprises the following steps:
applying positive voltage stress to the grid of the MIS-HEMT to charge until the charging is finished;
fully discharging the MIS-HEMT through a plurality of discharge processes, wherein the following steps are performed in each discharge process:
reducing a forward voltage stress applied to a gate of the MIS-HEMT;
monitoring the discharge process of the MIS-HEMT by adopting a spot-Id sense technology to obtain the current of the MIS-HEMT;
and determining a current change quantity according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift quantity of the MIS-HEMT according to the current change quantity.
In one embodiment, a forward voltage stress applied to a gate of the MIS-HEMT is reduced according to a preset voltage change amount.
In one embodiment, in each of the discharging processes, the forward voltage stress is periodically replaced with a test voltage while a drain voltage is supplied to a drain of the MIS-HEMT, and a source of the MIS-HEMT is grounded and a present current of the MIS-HEMT is detected.
In one embodiment, the test voltage range is (V) th -0.2,V th + 0.2), wherein, said V th Is the threshold voltage of the MIS-HEMT.
In one embodiment, the testing method further comprises:
calculating the accumulative density distribution of the boundary trap according to the threshold voltage drift amount;
and performing first-order differentiation on the accumulated density distribution of the boundary trap to obtain the energy distribution of the boundary trap of the MIS-HEMT.
In one embodiment, the formula for calculating the cumulative density distribution of the boundary traps is:
Figure BDA0002618801660000031
Figure BDA0002618801660000032
wherein N is trap Is the cumulative density distribution of the boundary traps,
Figure BDA0002618801660000033
is SiN x The dielectric capacitance of the dielectric layer is,
Figure BDA0002618801660000034
is SiN x Dielectric constant of dielectric layer, epsilon 0 Is a vacuum dielectric constant, <' > based on>
Figure BDA0002618801660000035
Is SiN x The thickness of the dielectric layer.
In one embodiment, the testing method further comprises: and judging that the MIS-HEMT is completely discharged and ending the detection process when judging that the maximum difference value is smaller than a preset value according to the maximum difference value among the multiple threshold voltage drift amounts acquired in the current discharging process.
In one embodiment, the discharge processes are of the same duration.
Based on the same inventive concept, the embodiment of the invention also provides an energy distribution testing system based on the boundary trap of the MIS-HEMT (Metal-Insulator-Semiconductor High Electron Mobility Transistor), which comprises,
the charging and discharging device is used for applying forward voltage stress to the grid electrode of the MIS-HEMT to charge in the charging process; and reducing a forward voltage stress applied to a gate of the MIS-HEMT during discharging; and
the detection device monitors the discharge process of the MIS-HEMT based on the spot-Id sense technology to obtain the current of the MIS-HEMT; and determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount.
In one embodiment, during each of the discharges, the detection device periodically provides a test voltage to replace the forward voltage stress while providing a drain voltage to the drain of the MIS-HEMT and grounding the source of the MIS-HEMT and detecting a present current of the MIS-HEMT.
In one embodiment, the detection device is further configured to calculate an accumulated density distribution of the boundary traps according to the threshold voltage drift amount, and perform first-order differentiation on the accumulated density distribution of the boundary traps to obtain an energy distribution of the boundary traps of the MIS-HEMT.
In one embodiment, the cumulative density distribution of the boundary traps is calculated by the formula:
Figure BDA0002618801660000041
Figure BDA0002618801660000042
wherein N is trap Is the cumulative density distribution of the boundary traps,
Figure BDA0002618801660000043
is SiN x The dielectric capacitance of the dielectric layer is,
Figure BDA0002618801660000044
is SiN x Dielectric constant of dielectric layer, epsilon 0 Is a vacuum dielectric constant, <' > based on>
Figure BDA0002618801660000045
Is SiN x The thickness of the dielectric layer.
In summary, the embodiment of the invention provides a method and a system for testing energy distribution of boundary traps of MIS-HEMT. Wherein the method comprises: applying positive voltage stress to the grid of the MIS-HEMT to charge until the charging is finished; fully discharging the MIS-HEMT through a plurality of discharge processes, wherein in each discharge process the following steps are performed: reducing a forward voltage stress applied to a gate of the MIS-HEMT; monitoring the discharge process of the MIS-HEMT by adopting a spot-Id sense technology to obtain the current of the MIS-HEMT; and determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount. According to the invention, a plurality of forward voltage stresses are sequentially applied in stages to fully discharge the MIS-HEMT, the discharge process of the MIS-HEMT is monitored by adopting a spot-Id sense technology in each discharge process, the current of the MIS-HEMT is obtained, then the current change amount is determined according to the current and the initial current of the MIS-HEMT, and the current threshold voltage drift amount of the MIS-HEMT is determined according to the current change amount, so that the test time is shortened, the escape of the boundary trap which can be quickly recovered in the process of measuring the threshold voltage drift amount is reduced, and the measurement range is met.
Drawings
Fig. 1 is a schematic flowchart of an energy distribution testing method for a boundary trap based on a MIS-HEMT according to an embodiment of the present invention;
fig. 2 is a schematic flowchart of another MIS-HEMT-based method for testing energy distribution of boundary traps according to the embodiment of the present invention;
FIG. 3 is a schematic diagram of signal connections at each end of an exemplary MIS-HEMT;
FIG. 4 is a schematic diagram of a Spot-Id sense test waveform provided in accordance with an embodiment of the present invention;
FIG. 5 is a waveform diagram illustrating a testing method according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of the physical mechanism of the testing method provided by the embodiment of the invention;
FIG. 7 (a) is a graph of test results provided by an embodiment of the present invention, and FIG. 7 (b) is a graph of Δ V provided by an embodiment of the present invention th A plot of the relationship to overdrive voltage;
fig. 8 (a) is a graph of the cumulative density of boundary traps provided by an embodiment of the present invention, and fig. 8 (b) is a graph of the energy distribution of the density of boundary traps provided by an embodiment of the present invention;
fig. 9 is an electrical structural diagram of an energy distribution testing system of a boundary trap based on a MIS-HEMT according to an embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be connected to the other element through intervening elements. Further, "connection" in the following embodiments is understood to mean "electrical connection", "communication connection", or the like, if there is a transfer of electrical signals or data between the connected objects.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.
Referring to fig. 1 and fig. 2, an embodiment of the invention provides a method for testing energy distribution of boundary traps based on a MIS-HEMT (Metal-Insulator-Semiconductor High Electron Mobility Transistor), including:
step S110, applying forward voltage stress to the grid of the MIS-HEMT to charge until the charging is finished;
step S120, fully discharging the MIS-HEMT through a plurality of discharging processes, and executing the following steps in each discharging process:
step S121, reducing the forward voltage stress applied to the grid of the MIS-HEMT;
step S122, adopting spot-I d sense technology monitoring the MIS-HEThe discharging process of the MT acquires the current of the MIS-HEMT;
and step S123, determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount.
It will be appreciated that in the present embodiment, spot-I is used d Monitoring the discharge process of the MIS-HEMT by using a sense technology to obtain the current of the MIS-HEMT, namely the forward voltage stress V gmeasure Applied to a device under test, V th Is no longer the conventional dc slow I-V sweep but only at a selected measurement voltage V gmeasure Measuring the current value of a single point; and then determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount, thereby shortening the test time and reducing the escape of the rapidly recoverable boundary trap in the process of measuring the threshold voltage drift amount. In addition, the MIS-HEMT is fully discharged through a step-type discharging process, so that the threshold voltage drift amount between every two adjacent energy levels is obtained, and the limitation of a voltage range on measuring equipment can be eliminated.
Referring to FIG. 3, assuming the MIS-HEMT in this embodiment is N-type, V is applied to the gate of the MIS-HEMT during the test dicharge，i (ii) a While providing a drain voltage to the drain of the MIS-HEMT and grounding the source of the MIS-HEMT. Referring to FIG. 4, FIG. 4 shows a test waveform of spot-Id sense, i.e. the measurement voltage V is controlled with a predetermined period and duration gmeasure And a drain voltage V d So as to intermittently obtain the drain current I d I.e., the current flowing through the MIS-HEMT. In addition, the drain bias voltage is kept at 0V during the charging phase and 0.1V during the testing phase.
Further, in the present embodiment, the duration of each measurement process is set to 1ms, that is, the measurement voltage V is continuously applied, in consideration of the response delay of the gate and the time required for the recovery of the rapidly recoverable trap gmeasure Is 1 millisecond in duration.
In one embodiment, a forward voltage stress applied to a gate of the MIS-HEMT is reduced according to a preset voltage change amount. As shown in FIG. 5, in the present embodiment, it is assumed that the forward voltage stress applied during charging is V gstress Stress of forward voltage of V gstress Last for 5 to 1000 seconds. Under the applied stress V gstress After reaching 1ks, the charging state is changed into the discharging state, and the voltage is changed by delta V according to the preset voltage g Determining a forward voltage stress V required to be applied to the gate of the MIS-HEMT by a first discharge process dicharge，1 ＝V gstress -ΔV g . Then based on V dicharge，1 Using spot-I in the first discharge phase d Detecting the current by using a sense technology, determining a current change quantity according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift quantity of the MIS-HEMT according to the current change quantity; determining a forward voltage stress V required to be applied to the gate of the MIS-HEMT by a second discharge process after the first discharge process is finished dicharge，2 ＝V dicharge，1 -ΔV g And calculating the corresponding threshold voltage drift amount in the second discharging process. And repeating the steps until the test process is finished. Furthermore, each V will be dicharge，i The discharge process is controlled to be 5-100 s to reduce the relatively high V dicharge，i The corresponding charging effect in the discharging process; for example, V in the present embodiment dicharge，i The corresponding discharge process duration is 100s.
It can be understood that the forward voltage stress applied to the gate of the MIS-HEMT is reduced in a stepwise manner, so that the Fermi level E is f Gradually decreasing, so that only the part of the boundary trap with the energy level position between the previous Fermi level and the current Fermi level can be discharged each time, and the threshold voltage drift amount in the corresponding energy level interval is obtained; as shown in FIG. 6, the forward voltage stress applied to the gate of the MIS-HEMT is represented by V dicharge，i Down to V dicharge，i+1 After a Fermi level E f Lowered to accommodate a shaded region whose solid boundary traps now have energies above E f To giveFor sufficient discharge time, all boundary traps in the shadow region should be able to discharge by tunneling through the AlGaN barrier or by trap-assisted conduction. With V dicharge，i And continuously decreasing to obtain the threshold voltage drift amount of a new energy interval, and finally obtaining the threshold voltage drift amount corresponding to all boundary traps in the gate dielectric layer within the whole voltage range.
In one embodiment, the testing method further comprises:
calculating the accumulative density distribution of the boundary trap according to the threshold voltage drift amount;
and performing first-order differentiation on the accumulated density distribution of the boundary trap to obtain the energy distribution of the boundary trap of the MIS-HEMT.
The formula for calculating the cumulative density distribution of the boundary traps is as follows:
Figure BDA0002618801660000091
Figure BDA0002618801660000092
wherein N is trap Is the cumulative density distribution of the boundary traps,
Figure BDA0002618801660000093
is SiN x The dielectric capacitance of the dielectric layer is,
Figure BDA0002618801660000094
is SiN x Dielectric constant of dielectric layer, epsilon 0 Is a vacuum dielectric constant, <' > based on>
Figure BDA0002618801660000095
Is SiN x The thickness of the dielectric layer.
Since the spatial distribution of boundary traps is unknown, and traps located in the AlGaN barrier and AlGaN/GaN interface may also induce Δ ν th Thus is atThe concept of effective trap density is used in this work. The trap is assumed to be in SiN x At the/AlGaN interface and an effective density is required to characterize the distribution of traps throughout the gate dielectric layer.
Referring to FIG. 7, the forward voltage stress applied to the gate of the MIS-HEMT during charging is V gstress Then varied by a preset voltage variation Δ V g Is gradually decreased to obtain V dicharge，i (ii) a It should be noted here that Δ V cannot be adjusted g Set too small to ensure at all V dicharge，i Discharging is dominant under driving. From the graph (a) in FIG. 7, it can be seen that Δ V is observed after applying 10V 1ks stress th 2.37V is achieved; then, the gate voltage is reduced to V dicharge，1 After =9V, Δ V due to boundary trap discharge th And begins to decrease. Δ V as the discharge process progresses th Gradually decreases as shown in "\9633;" in fig. 7 (a). Note that since the first discharge time is already 5s, at V dicharge，i Corresponding last measured value to V dicharge，i+1 Δ V between corresponding first measured values th A sudden drop occurs indicating that most of the boundary traps are close to SiN x the/AlGaN interface and discharges within 5 seconds. Duration T of discharge process dicharge After reaching a predetermined value (here 100 seconds to avoid further collapse and to ensure that the discharge process is dominant) dicharge Continue to decline and a similar Δ V can be observed th The law of change with time. By measuring Δ V at the end of the discharge time th Value relative to the corresponding overdrive voltage
Figure BDA0002618801660000101
Drawing, which can be obtained in relation to +>
Figure BDA0002618801660000102
Δ V of th Curve, as shown by "# in plot (b) in fig. 7.
Let E f All boundary traps above are empty and E f The lower boundary traps are all filled, the trap energy is equalIn E f Based on which it can be obtained from simulation calculations
Figure BDA0002618801660000103
FIG. 8 shows the relationship of (1). Combine equations (1) and (2) and +>
Figure BDA0002618801660000104
Figure BDA0002618801660000105
E c Is SiN x Bottom of conduction band of AlGaN interface), the accumulated trap density N is calculated trap ～E c -E trap Distribution, as shown in (a) of fig. 8. In obtaining N trap After distribution, can be from N trap The first order differential of the above gives the energy density distribution D trap As shown in fig. 8 (b). In general, at E c -E trap From-1.78 eV to-0.26 eV with E trap Is close to E c ，D trap The value becomes higher. Furthermore, in E c -E trap Two distinct peaks were observed at-0.46 eV and-0.3 eV, and the peak densities thereof were 2.91X 1011 and 8.93X 1011 cm-2. EV-1, respectively.
In one embodiment, the discharge processes are of the same duration. In the embodiment, the forward voltage stress applied to the MIS-HEMT is reduced in a stepwise manner according to the interval of the preset duration time of the discharge process; for example, each discharge process lasts 100s, and within this 100s, a spot-I is used d The sense technology obtains a plurality of single-point currents, and correspondingly calculates the corresponding threshold voltage drift amount. In addition, the time lengths of the plurality of discharging processes may also be different or partially the same, which is not limited in this embodiment.
In one embodiment, the testing method further comprises: and judging that the MIS-HEMT is completely discharged and ending the detection process when judging that the maximum difference value is smaller than a preset value according to the maximum difference value among the multiple threshold voltage drift amounts acquired in the current discharging process. I.e. when passing V dicharge，i Becomes V dicharge，i+1 And corresponding Δ V th If the value of (c) is small, it is determined that the discharge has been completed.
In one embodiment, the test voltage range is (V) th -0.2,V th + 0.2), wherein said V th Is the threshold voltage of the MIS-HEMT. In addition, the test voltage may be set in the vicinity of the operating voltage of the MIS-HEMT.
Based on the same inventive concept, the embodiment of the invention also provides an energy distribution test system of the boundary trap based on the MIS-HEMT. Referring to fig. 9, the testing system includes a charging and discharging device 910 and a detecting device 920.
The charging and discharging device 910 is used for applying a forward voltage stress to the gate of the MIS-HEMT to charge in a charging process; and reducing a forward voltage stress applied to the gate of the MIS-HEMT during discharging.
The detection device 920 monitors the discharge process of the MIS-HEMT based on a spot-Id sense technology to obtain the current of the MIS-HEMT; and determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount.
In this example, spot-I was used d Monitoring the discharge process of the MIS-HEMT by using a sense technology to obtain the current of the MIS-HEMT, namely the forward voltage stress V gmeasure Applied to a device under test, V th Is no longer the conventional dc slow I-V sweep but only at a selected measurement voltage V gmeasure Measuring a current value of a single point; and then determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount, thereby shortening the test time and reducing the escape of the rapidly recoverable boundary trap in the process of measuring the threshold voltage drift amount. In addition, the MIS-HEMT is fully discharged through a plurality of stepped discharging processes, so that the threshold voltage drift amount between every two adjacent energy levels is obtained, and the problem of high current leakage current caused by the MIS-HEMT can be solvedThe voltage range is limited to the measurement equipment.
In one embodiment, during each of the discharging processes, the detection device periodically provides a test voltage to replace the forward voltage stress while providing a drain voltage to the drain of the MIS-HEMT and grounding the source of the MIS-HEMT and detecting the present current of the MIS-HEMT.
In this embodiment, assuming that the MIS-HEMT is N-type, V is applied to the gate of the MIS-HEMT during the test dicharge，i (ii) a While providing a drain voltage to the drain of the MIS-HEMT and grounding the source of the MIS-HEMT. The test waveform of the spot-Id sense is as shown in FIG. 3, namely, the measuring voltage V is controlled by the preset period and the duration gmeasure And a drain voltage V d So as to intermittently obtain the drain current I d I.e. the current flowing through the MIS-HEMT. In addition, the drain bias voltage is kept at 0V during the charging phase and 0.1V during the testing phase.
Further, in the present embodiment, the duration of each measurement process is set to 1ms, that is, the measurement voltage V is continuously applied, in consideration of the response delay of the gate and the time required for the recovery of the rapidly recoverable trap gmeasure Is 1 millisecond in duration.
The embodiment gradually reduces the voltage applied to the gate of the MIS-HEMT by a step-down manner according to a preset voltage change amount. Assuming that the forward voltage stress applied during charging is V gstress Stress of forward voltage of V gstress Last for 5-1000 s. Under the applied stress V gstress After reaching 1ks, the change amount of the voltage Δ V is changed from the charging state to the discharging state according to the predetermined voltage g Determining a forward voltage stress V required to be applied to the gate of the MIS-HEMT by a first discharge process dicharge，1 ＝V gstress -ΔV g . Then based on V dicharge，1 Using spot-I in the first discharge phase d The sense technology detects the current, then determines the current change amount according to the current and the initial current of the MIS-HEMT, and determines the current threshold voltage drift of the MIS-HEMT according to the current change amountAn amount; after the first discharge process is finished, determining that the second discharge process needs to apply the forward voltage stress V on the grid electrode of the MIS-HEMT dicharge，2 ＝V dicharge，1 -ΔV g And calculating the corresponding threshold voltage drift amount in the second discharging process. And the rest is done in sequence until the test process is finished. Furthermore, each V will be dicharge，i The discharge process is controlled to be 5-100 s to reduce the relatively high V dicrge，i The corresponding charging effect in the discharging process; for example, V in the present embodiment dicharge，i The corresponding discharge process duration is 100s.
It can be understood that, by the way of reducing the voltage in a stepwise manner, the fermi level is gradually reduced, so that only the part of the boundary traps of which the energy level positions are between the previous fermi level and the current fermi level can be discharged each time, and the threshold voltage drift amount in the corresponding energy level interval is obtained; as shown in FIG. 5, the forward voltage stress applied to the gate of the MIS-HEMT is represented by V dicharge，i Down to V dicharge，i+1 After a Fermi level E f Lowered to accommodate a shaded region whose solid boundary traps now have energies above E f Given sufficient discharge time, all boundary traps in the shaded region should be able to discharge either by tunneling the AlGaN barrier or by trap-assisted conduction. With V dicharge，i And continuously decreasing to obtain the threshold voltage drift amount of a new energy interval, and finally obtaining the threshold voltage drift amount corresponding to all boundary traps in the gate dielectric layer within the whole voltage range.
In one embodiment, the detecting device 920 is further configured to calculate an accumulated density distribution of the boundary traps according to the threshold voltage drift amount, and perform first differentiation on the accumulated density distribution of the boundary traps to obtain an energy distribution of the boundary traps of the MIS-HEMT.
The formula for calculating the accumulative density distribution of the boundary traps is as follows:
Figure BDA0002618801660000131
Figure BDA0002618801660000132
wherein N is trap Is the cumulative density distribution of the boundary traps,
Figure BDA0002618801660000133
is SiN x The dielectric capacitance of the dielectric layer is,
Figure BDA0002618801660000134
is SiN x Dielectric constant of dielectric layer, epsilon 0 Is a vacuum dielectric constant, is greater than or equal to>
Figure BDA0002618801660000135
Is SiN x The thickness of the dielectric layer. />
It is understood that since the spatial distribution of boundary traps is unknown, traps located in the AlGaN barrier and AlGaN/GaN interface may also induce Δ V th The concept of effective trap density is therefore used in this work. The trap is assumed to be in SiN x At the/AlGaN interface and an effective density is required to characterize the distribution of traps throughout the gate dielectric layer.
From the above analysis of FIG. 6, most of the boundary traps are close to SiN x the/AlGaN interface and discharges within 5 seconds. Duration T of discharge process dicharge After reaching the predetermined value, V dicharge Continue to decline and a similar Δ V can be observed th Law of change over time. By measuring Δ V at the end of the discharge time th Value relative to the corresponding overdrive voltage
Figure BDA0002618801660000141
Drawing, which can be obtained in relation to +>
Figure BDA0002618801660000142
Δ V of th The curves are shown in the figure, and,
suppose E f All boundary traps above are empty and E f The lower boundary traps are filled, the trap energy is equal to E f Based on which it can be obtained from simulation calculation
Figure BDA0002618801660000143
The relationship (c) is as shown in FIG. 7. Combining equations (1) and (2) and +>
Figure BDA0002618801660000144
Figure BDA0002618801660000145
E c Is SiN x Bottom of conduction band of AlGaN interface), the accumulated trap density N is calculated trap ～E c -E trap The distribution is as shown in the graph (a) in fig. 7. In obtaining N trap After distribution, can be from N trap The first order differential of the above gives the energy density distribution D trap As shown in fig. 7 (b). In general, at E c -E trap Ranging from-1.78 eV to-0.26 eV with E trap Close to E c ，D trap The value becomes higher. Furthermore, in E c -E trap Two distinct peaks were observed at-0.46 eV and-0.3 eV, and the peak densities thereof were 2.91X 1011 and 8.93X 1011 cm-2. EV-1, respectively.
In summary, the embodiment of the invention provides a method and a system for testing energy distribution of boundary traps of MIS-HEMT. Wherein the method comprises: applying positive voltage stress to the grid of the MIS-HEMT to charge until the charging is finished; fully discharging the MIS-HEMT through a plurality of discharge processes, wherein the following steps are performed in each discharge process: reducing a forward voltage stress applied to a gate of the MIS-HEMT; monitoring the discharge process of the MIS-HEMT by adopting a spot-Id sense technology to obtain the current of the MIS-HEMT; and determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount. According to the invention, a plurality of forward voltage stresses are sequentially applied in stages to fully discharge the MIS-HEMT, the discharge process of the MIS-HEMT is monitored by adopting a spot-Id sense technology in each discharge process, the current of the MIS-HEMT is obtained, then the current change quantity is determined according to the current and the initial current of the MIS-HEMT, and the current threshold voltage drift quantity of the MIS-HEMT is determined according to the current change quantity, so that the test time is shortened, the escape of the rapidly recoverable boundary trap in the process of measuring the threshold voltage drift quantity is reduced, and the measurement range is met.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.
All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (12)

1. A method for testing energy distribution of boundary traps based on MIS-HEMT (Metal-Insulator-Semiconductor High Electron Mobility Transistor) is characterized by comprising the following steps:
applying positive voltage stress to the grid of the MIS-HEMT to charge until the charging is finished;
fully discharging the MIS-HEMT through a plurality of discharging processes, and executing the following steps in each discharging process:
reducing a forward voltage stress applied to a gate of the MIS-HEMT;
monitoring the discharge process of the MIS-HEMT by adopting a spot-Id sense technology to obtain the current of the MIS-HEMT;
and determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount.
2. The method of claim 1, wherein a forward voltage stress applied to the gate of the MIS-HEMT is reduced according to a predetermined voltage change amount.
3. The test method of claim 1, wherein during each of the discharges, the forward voltage stress is periodically replaced with a test voltage while a drain voltage is provided to a drain of the MIS-HEMT, and a source of the MIS-HEMT is grounded and a present current of the MIS-HEMT is detected.
4. The test method of claim 3, wherein the test voltage range is (V) th -0.2,V th + 0.2), wherein, said V th Is the threshold voltage of the MIS-HEMT.
5. The test method of claim 1, further comprising:
calculating the accumulative density distribution of the boundary trap according to the threshold voltage drift amount;
and performing first order differentiation on the accumulated density distribution of the boundary trap to obtain the energy distribution of the boundary trap of the MIS-HEMT.
6. The test method of claim 5, wherein the cumulative density distribution of the boundary traps is calculated by the formula:
Figure FDA0004057579150000021
Figure FDA0004057579150000022
wherein N is trap Is the cumulative density distribution of the boundary traps,
Figure FDA0004057579150000023
is SiN x Medium capacitance of the medium layer is greater or less>
Figure FDA0004057579150000024
Is SiN x Dielectric constant of dielectric layer, epsilon 0 Is a vacuum dielectric constant, is greater than or equal to>
Figure FDA0004057579150000025
Is SiN x Thickness of dielectric layer, Δ V th Is the threshold voltage shift amount.
7. The testing method of claim 1, further comprising: and judging that the MIS-HEMT is completely discharged and ending the detection process when judging that the maximum difference value is smaller than a preset value according to the maximum difference value among the multiple threshold voltage drift amounts acquired in the current discharging process.
8. The test method of claim 1, wherein a plurality of the discharge events are of the same duration.
9. An energy distribution test system based on MIS-HEMT (Metal-Insulator-Semiconductor High Electron Mobility Transistor) boundary traps is characterized by comprising,
the charging and discharging device is used for applying forward voltage stress to the grid electrode of the MIS-HEMT to charge in the charging process; and reducing a forward voltage stress applied to a gate of the MIS-HEMT during discharging; and
the detection device monitors the discharge process of the MIS-HEMT based on a spot-Id sense technology to obtain the current of the MIS-HEMT; and determining a current change amount according to the current and the initial current of the MIS-HEMT, and determining the current threshold voltage drift amount of the MIS-HEMT according to the current change amount.
10. The test system of claim 9 wherein during each of the discharges, the detection means periodically provides a test voltage to replace the forward voltage stress while providing a drain voltage to the drain of the MIS-HEMT and grounding the source of the MIS-HEMT and detecting a present current of the MIS-HEMT.
11. The test system of claim 9, wherein the detection device is further configured to calculate a cumulative density distribution of the boundary traps according to the threshold voltage shift amount, and perform a first order differentiation on the cumulative density distribution of the boundary traps to obtain an energy distribution of the boundary traps of the MIS-HEMT.
12. The test system of claim 11, wherein the formula for calculating the cumulative density distribution of boundary traps is:
Figure FDA0004057579150000031
Figure FDA0004057579150000032
wherein N is trap Is the cumulative density distribution of the boundary traps,
Figure FDA0004057579150000033
is SiN x Medium capacitance of the medium layer is greater or less>
Figure FDA0004057579150000034
Is SiN x Dielectric constant of dielectric layer, epsilon 0 Is a vacuum dielectric constant, <' > based on>
Figure FDA0004057579150000035
Is SiN x Thickness of dielectric layer, Δ V th Is the threshold voltage shift amount. />
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