WO2020088002A1 - Novel method for extracting degraded average activation energy of algan/gan hemt device - Google Patents

Abstract

Disclosed is a novel method for extracting degraded average activation energy of an AlGaN/GaN HEMT device. The steps of the method comprise: extracting dynamic conduction impedance in the device by means of a dynamic impedance extracting circuit; fitting the extracted dynamic conduction impedance curve and extracting the slope of the fitted curve; respectively calculating a conduction loss and a switching loss of the device in a switching circuit, and converting the loss into a temperature rise caused by the loss when the device operates; establishing a relationship model between the activation energy and the dynamic conduction impedance R_dson; finally obtaining the degraded average activation energy of the device. For the first time, the present invention associates the dynamic conduction impedance of the AlGaN/GaNHEMT device with the degraded average activation energy of the device, and the dynamic conduction impedance of the HEMT device can be extracted by means of a built circuit. This method is used for extracting the degraded average activation energy of the HEMT device simply and quickly, is simple in apparatus, and can also be used for guiding the design of subsequent switching circuits to reduce the influence of device defects.

Description

Novel extraction method for average activation energy of degraded AlGaN / GaN HEMT devices Technical field

The invention relates to a novel extraction method of average activation energy of degraded AlGaN / GaN HEMT devices.

Background technique

AlGaN / GaN HEMT devices are a new generation of wide bandgap semiconductor devices after silicon-based and silicon carbide-based MOSFETs. They have unmatched superior performance on silicon and lower cost than silicon carbide. Because AlGaN and GaN materials have the characteristics of wide band gap, polarization effect and conduction band discontinuity, the prepared AlGaN / GaN HEMT device has high frequency, high withstand voltage, large current, high temperature resistance, strong anti-interference Field effect transistors with superior electrical performance. In particular, the forbidden bandwidth of the interlayer material of the HEMT device and the high dielectric constant can control the junction capacitance to a very low level. The input capacitance (C _iss ), output capacitance (C _oss ) and feedback capacitance of the AlGaN / GaN HEMT device (C _rss ) is usually in the order of tens of pF, tens of pF, and several pF, which is much lower than the order of thousands of pF, hundreds of pF, and hundreds of pF of silicon-based and silicon carbide-based MOSFETs, so the performance at high frequencies Outstanding performance.

The spontaneous polarization of AlGaN / GaN materials and the discontinuity of piezoelectric polarization and conduction band caused by the difference in lattice constants form a high-density two-dimensional electron gas with a natural bulk density of the order of 10 ¹⁹ , making its conductivity The through impedance is very low. Unfortunately, AlGaN / GaN HEMT devices have various reliability issues during continuous operation, especially under high off-state voltage and high switching frequency operating conditions. When the HEMT device is operated at a high drain voltage and a high switching frequency, a local electric field of up to several MV / cm will activate the AlGaN barrier layer, GaN buffer layer, and defects at the AlGaN / GaN interface and AlGaN surface The activated defect will trap some electrons of the two-dimensional electron gas (2DEG) in the channel, resulting in undesirable degradation of the dynamic state resistance (R _dson ).

At present, the high-density defects generated by the growth of GaN and AlGaN materials continue to plague the development of the industry, so that the problem of increased dynamic on-resistance in AlGaN / GaN HEMT devices cannot be completely eliminated. Therefore, in addition to physical-based characterization methods, we also need to develop new application-based characterization methods to study the problem of dynamic on-resistance increase and correlate it with the activation energy of device defects in the deep physical sense to discover The relationship between the activation energy of the device defect and the application circuit, so that new methods based on back-end applications can be found to circumvent the problem of increased dynamic on-resistance.

Many studies have used different methods to characterize the activation energy of defects in AlGaN / GaN HEMT devices. For example, Klein et al. Used the optical quenching measurement method to study the deep level defects in GaN-based metal semiconductor field effect transistors (MSFETs) and extracted their activation energy using the spectral dependence of the defects; Zhang et al. Used pulsed drain voltage measurement The method characterized the acceptor state defects at the AlGaN / GaN interface. In addition, the activation energy of defects in AlGaN / GaN HEMT devices can also be obtained by high-resolution transmission electron microscopy, capacitive mode deep-level transient spectroscopy, and deep-level spectroscopy. Although these methods can obtain accurate numerical results through physical or numerical analysis, these methods are based on wafer-level measurement, which is also very complicated to operate, and the equipment is also very expensive. In addition, these methods cannot intuitively understand how defects affect the performance of AlGaN / GaN HEMT devices in switching power converters. Therefore, it is very important to measure the capture effect of the HEMT device in the actual switching circuit.

Summary of the invention

The object of the present invention is to provide a novel extraction method for the average activation energy of degraded AlGaN / GaN HEMT devices.

The object of the present invention is achieved by the following technical solutions:

A new method for extracting the average activation energy of degraded AlGaN / GaN HEMT devices, the steps include:

(1) Extract the dynamic on-resistance R _dson in the AlGaN / GaN HEMT device through the dynamic impedance extraction circuit;

(2) Fit the extracted dynamic on-resistance curve and extract the slope of the fitted curve;

(3) Calculate the conduction loss P _CON and the switching loss P _{SW of the} AlGaN / GaN HEMT device in the switching circuit separately;

(4) Convert the conduction loss P _CON and the switching loss P _SW into the temperature rise ΔT caused by the loss when the AlGaN / GaN HEMT device is in operation;

(5) Establish the relationship model between the activation energy and the dynamic on-resistance R _dson , and obtain the average activation energy of the degraded AlGaN / GaN HEMT device.

Preferably, in step (2), the dynamic on-resistance is normalized and then fitted to the curve. The normalized way is to normalize the dynamic on-resistance of the AlGaN / GaN HEMT device under test and its DC on-resistance Change.

Preferably, the calculation method of the conduction loss P _CON of the AlGaN / GaN HEMT device in the switching circuit in step (3) is:

P _CON = K _th K _D I _rms ² R _dson (1)

Where R _dson is the on-resistance, including DC on-resistance and dynamic on-resistance, which can be accurately extracted by the circuit proposed in FIG. 1 of the present invention, and its value is equal to the voltage drop at point B when the AlGaN / GaN HEMT device is turned on The forward voltage drop to D ₁ and D ₂ is divided by the current I _{ds conducted} by the device; k _th is the proportional coefficient of the device's on-resistance with temperature (relative to 25 ° C); k _D is dynamic The proportional coefficient of the on-resistance relative to the increase of the on-resistance of the DC; I _rms is the effective value of the on-current of the AlGaN / GaN HEMT device, which can be actually captured by the oscilloscope.

Preferably, the calculation method for the switching loss P _SW of the AlGaN / GaN HEMT device in the switching circuit in step (3) is:

Where I _ds is the real-time output current through the AlGaN / GaN HEMT device, V _ds is the real-time voltage loaded on the drain of the device, and dt includes the _on time t _on and off time t _{off respectively} , which can be obtained by the actual capture of the oscilloscope ; C _oss is the output capacitance of the AlGaN / GaN HEMT device; f _s is the operating frequency of the AlGaN / GaN HEMT device.

Preferably, the temperature rise ΔT is calculated as:

ΔT ＝ (1 + k) I _rms ² R _dson R _θJA (3)

Where k = P _sw / P _CON (4)

Where k is the ratio of switching loss converted to conduction loss, and R _θJA is the thermal resistance of the device from junction to air.

Preferably, the relationship model between the activation energy and the dynamic on-resistance R _dson in step (5) is:

Where γ ₁ and γ ₂ are the electric field acceleration factors of the AlGaN barrier layer and the GaN buffer layer, E is the electric field, k _B is the Boltzmann constant, and T is the junction temperature of the device. Slope is the rate of change of the related physical variable. The related physical variable used here is the normalized dynamic on-resistance, so slope is transformed into slope (R _dson ). Ea is the activation energy of defects in the device.

The beneficial effects of the present invention are as follows:

(1) The present invention relates for the first time the dynamic on-resistance of AlGaN / GaN HEMT devices to the average activation energy of device degradation, and the dynamic on-resistance of HEMT devices can be extracted by the built circuit, the extraction method is simple and quick, and the equipment is simple .

(2) This method can extract the average activation energy of wafer-level AlGaN / GaN HEMT devices before packaging and finished device degradation after packaging.

(3) This method can be used to explain the reason why the dynamic on-resistance of AlGaN / GaN HEMT devices changes with the drain voltage of the device, and guide the design of subsequent switching circuits to reduce the impact of device defects.

(4) Through this method, it is possible to propose an operating mode that is more conducive to the application of AlGaN / GaN HEMT devices in high-frequency circuits, thereby reducing the problem of increased dynamic on-resistance. Through the method of the present invention, it is found that, under the condition of a specific operating frequency and input voltage, in order to reduce the problem of increasing the dynamic on-resistance, the duty ratio of the operation can be increased as much as possible, thereby reducing the influence of the off-state high voltage. In addition, the critical discontinuous operation mode (QRM) or other soft-switching operation methods that can reduce the voltage value in the off state are beneficial to reduce the problem of increased dynamic on-resistance.

BRIEF DESCRIPTION

Figure 1 is a flow diagram of a new method for extracting the average activation energy of degraded AlGaN / GaN HEMT devices.

FIG. 2 is a circuit diagram for extracting the dynamic on-resistance of the AlGaN / GaN HEMT device used in Embodiment 1 of the present invention.

Fig. 3 is the normalized dynamic on-resistance test result and curve fitting diagram.

detailed description

Example 1

The novel extraction method for the average activation energy of the degraded AlGaN / GaN HEMT device includes the following steps:

(1) Extract the dynamic on-resistance R _dson in the AlGaN / GaN HEMT device through the dynamic impedance extraction circuit;

(2) After normalizing the dynamic on-resistance of the tested AlGaN / GaN HEMT device and its DC on-resistance, fitting the extracted dynamic on-resistance curve, extracting the slope of the fitted curve, the fitted curve is as shown in the figure As shown in Fig. 2, the X axis in Fig. 2: the drain loading voltage of the tested AlGaN / GaN HEMT device, and the Y axis: the normalized dynamic on-resistance. The normalized way is to test the AlGaN / GaN HEMT device under test The dynamic on-resistance is normalized to its DC on-resistance; test conditions: operating frequency is 100kHz, duty cycle is 80%, drain loading voltage is from 50V to 600V; fitting curve shows that it exists when 200V drain loading voltage An inflection point, the cause of this inflection point can be explained by the level of different activation energy levels;

(3) Calculate the conduction loss P _CON and the switching loss P _{SW of the} AlGaN / GaN HEMT device in the switching circuit separately;

P _CON = K _th K _D I _rms ² R _dson (1)

In formula (1), I _rms is the effective value of the on-current of the AlGaN / GaN HEMT device, R _dson is the on-resistance, in the formula (2), I _ds is the real-time output current through the AlGaN / GaN HEMT device, and V _ds is loading device in real time the drain voltage, dt respectively comprising on-time t _on and turn-off time t _off, C _oss is the output capacitance of AlGaN / GaN HEMT devices, f _s is the operating frequency AlGaN / GaN HEMT devices.

(4) Convert the conduction loss P _CON and the switching loss P _SW into the temperature rise ΔT caused by the loss when the AlGaN / GaN HEMT device is in operation;

ΔT ＝ (1 + k) I _rms ² R _dson R _θJA (3)

k ＝ P _sw / P _CON (4)

In equation (3), k is the ratio of switching loss converted into conduction loss, and R _θJA is the thermal resistance of the device from junction to air.

(5) Establish the relationship model between the activation energy and the dynamic on-resistance R _dson , and obtain the average activation energy of the degraded AlGaN / GaN HEMT device.

The modeling process is as follows:

a: The standard Arrhenius theorem:

Where A is the exponential pre-factor, k _B is the Boltzmann constant, E _a is the activation energy of the defect in the device, and T is the junction temperature of the device.

b: The Arrhenius equation is converted into:

Where γ is the acceleration factor of the electric field, E is the electric field, and slope is the rate of change of the related physical variable

c. Calculate the conduction loss and switching loss of AlGaN / GaN HEMT device and convert it into conduction loss according to the ratio:

T _rise = (P _CON + P _SW ) R _θJA = (1 + k) I _rms ² R _dson R _θJA

Where T _rise is temperature rise, P _CON is the conduction loss of AlGaN / GaN HEMT device, P _SW is the switching loss of AlGaN / GaN HEMT device, and k is the ratio of switching loss converted into conduction loss. I _rms is the effective value of the device's on-current, R _dson is the on-resistance, and R _θJA is the device's junction-to-air thermal resistance.

d. Convert the conduction loss after conversion into temperature rise:

ΔT = (1 + k) I _rms ² ΔR _dson R _θJA

e. Obtain the relationship model between activation energy and dynamic on-resistance:

In the formula, γ ₁ and γ ₂ are the electric field acceleration factors of the AlGaN barrier layer and the GaN buffer layer, respectively; because slope is the rate of change of the related physical variable, the related physical variable used here is the normalized dynamic on-resistance, so slope changes to slope (R _dson ).

The dynamic impedance extraction circuit of the AlGaN / GaN HEMT device used in this embodiment includes: the AlGaN / GaN HEMT device to be tested, the power input unit V _Bulk of the AlGaN / GaN HEMT device to be tested, the resistive load R _LOAD , the constant current Unit I ₁ , constant current unit I ₁ power supply input unit VCC, isolation diodes D ₁ and D ₂ , freewheeling diode D ₃ , anti-reverse diode D ₅ , clamping and freewheeling diode ZD ₁ , drive unit, damping resistor R ₁ and R ₂ , the load resistance R _t , the power supply input unit V _Bulk supplies the drain of the AlGaN / GaN HEMT device, and a resistive load is also connected in series between the V _Bulk and the drain of the AlGaN / GaN HEMT device R _LOAD , the source of the AlGaN / GaN HEMT device is grounded, the drive unit provides the required drive input control signal for the AlGaN / GaN HEMT device, the power supply input unit VCC is connected to the anode of the anti-reverse diode D ₅ , and the anti-reverse diode D I ₁ is connected to the positive electrode, negative electrode and the constant current unit I is _a constant current unit ₅ is connected to the positive electrode of the D _2, D ₂ connected to the positive negative electrode D _1, D ₁ is connected to the negative electrode AlGaN / GaN HEMT devices Drain level, one end of R _{t is} connected to the positive pole of D ₂ and the other end is grounded , D negative and D ₃ is connected to the positive _2, D positive electrode and R _{3 2} are connected, R ₂ other end, negative electrode and the D ZD ₁ positive electrode ₁ is connected, ZD positive for R ₁ is _a connection, R & lt _one another One end is grounded.

This circuit uses a dual diode isolation (DDI) method to obtain higher measurement accuracy. In particular, all the functional devices in this circuit use devices with low parasitic capacitance, which improves the high frequency response. For example, the dual isolation diodes D ₁ and D ₂ select UF4007 (1A / 1000V), whose parasitic capacitance is less than 40pF when the voltage stress is below 10V, and its reverse recovery time (trr) is less than 100ns. At the same time, the clamp and freewheeling diodes D ₃ and ZD ₁ select 1N4148 (150mA / 100V) and general Zener diode (5V / 0.5W), and their parasitic capacitance is only 0.9pF when the voltage stress is below 10V, while the t _rr is less than 5ns. In addition, the constant current I _{1 is} composed of a 5V constant voltage source and a constant current diode of 3mA or lower. The constant current diode is actually a junction transistor with a short gate-source, so it can achieve a constant current in a wide voltage range.

Other published circuits can also be used to extract the dynamic on-resistance in AlGaN / GaN HEMT devices.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, changes, modifications, substitutions, combinations, The simplifications should all be equivalent replacement methods, which are all included in the protection scope of the present invention.

Claims (6)

1. A new method for extracting the average activation energy of degraded AlGaN / GaN HEMT devices, the steps include:

   (1) Extract the dynamic on-resistance R _dson in the AlGaN / GaN HEMT device through the dynamic impedance extraction circuit;

   (2) Fit the extracted dynamic on-resistance curve and extract the slope of the fitted curve;

   (3) Calculate the conduction loss P _CON and the switching loss P _{SW of the} AlGaN / GaN HEMT device in the switching circuit separately;

   (4) Convert the conduction loss P _CON and the switching loss P _SW into the temperature rise ΔT caused by the loss when the AlGaN / GaN HEMT device is in operation;

   (5) Establish the relationship model between the activation energy and the dynamic on-resistance R _dson , and obtain the average activation energy of the degraded AlGaN / GaN HEMT device.
2. The novel extraction method for the average activation energy of the degraded AlGaN / GaN HEMT device according to claim 1, characterized in that: in step (2), the dynamic on-resistance is normalized and the curve is fitted, the normalized The method is to normalize the dynamic on-resistance of the tested AlGaN / GaN HEMT device and its DC on-resistance.
3. The new method for extracting the average activation energy of the degraded AlGaN / GaN HEMT device according to claim 2, characterized in that: the calculation method of the conduction loss P _CON of the AlGaN / GaN HEMT device in the switching circuit in step (3) is :

   P _CON = K _th K _D I _rms ² R _dson (1)

   Where R _dson is the on-resistance, including DC on-resistance and dynamic on-resistance; k _th is the proportional coefficient of the device's on-resistance with temperature; k _D is the proportional coefficient of the dynamic on-resistance relative to the increase of the DC on-resistance ; I _rms is the effective value of the on-current of the AlGaN / GaN HEMT device, which can be actually captured by the oscilloscope.
4. The new method for extracting the average activation energy of the degraded AlGaN / GaN HEMT device according to claim 3, characterized in that the calculation method of the switching loss P _SW in the switching circuit of the AlGaN / GaN HEMT device in step (3) is :

   

   In the formula, I _ds is the real-time output current through the AlGaN / GaN HEMT device, V _ds is the real-time voltage loaded on the drain of the device, and dt includes the _on- time t _on and off-time t _{off respectively} , and this time is actually captured by the oscilloscope; C _oss is the output capacitance of the AlGaN / GaN HEMT device; f _s is the operating frequency of the AlGaN / GaN HEMT device.
5. The novel extraction method for the average activation energy of the degraded AlGaN / GaN HEMT device according to claim 4, characterized in that the temperature rise ΔT is calculated as:

   ΔT ＝ (1 + k) I _rms ² R _dson R _θJA (3)

   Where k = P _sw / P _CON (4)

   Where k is the ratio of switching loss converted to conduction loss, and R _θJA is the thermal resistance of the device from junction to air.
6. The novel method for extracting the average activation energy of the degraded AlGaN / GaN HEMT device according to claim 5, characterized in that the relation model between the activation energy and the dynamic on-resistance R _dson in step (5) is:

   

   Where γ ₁ and γ ₂ are the electric field acceleration factors of the AlGaN barrier layer and the GaN buffer layer, E is the electric field, k _B is the Boltzmann constant, T is the junction temperature of the device, and slope is the rate of change of the related physical variable The physical variable used for the relationship is the normalized dynamic on-resistance, so slope is transformed into slope (R _dson ), and Ea is the activation energy of the defect in the device.

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