A method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation

Abstract

The present invention discloses a method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation, comprising the steps of: (1) performing an initial threshold voltage test on the MOSFET device; (2) irradiating the above-mentioned MOSFET device with an electron beam to accelerate the aging of the device; (3) gradually increasing the irradiation dose in a set step size, testing and recording the threshold voltage of the device after different irradiation doses; (4) performing negative high-temperature gate bias accelerated aging on the MOSFET device to obtain the threshold voltage offset ΔV of the device under the specified high-temperature gate bias accelerated stress condition A th(A) ; (5) according to the threshold voltage offset obtained in step (2) being ΔV th(A) , the corresponding irradiation dose D A ; (6) electron beam irradiation accelerated aging with an irradiation dose of D A can be used to replace the negative high-temperature gate bias accelerated stress condition A to perform a rapid reliability test on the device. The present invention can rapidly detect the reliability of the MOSFET gate oxide layer and has wide applications.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and particularly relates to a method for detecting the reliability of MOSFET gate oxide layers by electron beam irradiation. Background Art

[0002] As a MOS device whose operating state is controlled by a gate, the gate oxide reliability of a power MOSFET device is crucial, and usually a high-temperature gate bias test is used to evaluate it. By detecting the drift amount (ΔV th ) of the threshold voltage V of the MOSFET device during the test, the high-temperature gate bias stability of the device's gate oxide is measured. th

[0003] Under positive high-temperature gate bias stress, a positive DC bias voltage is applied to the gate, and traps in the MOSFET gate oxide layer capture electrons, causing the threshold voltage to rise. Under negative high-temperature gate bias stress, a negative DC bias voltage is applied to the gate, and traps in the MOSFET gate oxide layer capture holes, causing the threshold voltage to decrease.

[0004] However, as a traditional method for detecting the reliability of the MSOFET gate oxide layer, the high-temperature gate bias aging test usually requires a long time. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for detecting the reliability of MOSFET gate oxide layers by electron beam irradiation, so as to achieve rapid detection of the reliability of MOSFET device gate oxide layers.

[0006] The present invention is implemented by the following technical solutions:

[0007] A method for detecting the reliability of MOSFET gate oxide layers by electron beam irradiation includes the following steps:

[0008] (1) Test the threshold voltage and gate oxide capacitance of the MOSFET device: Conduct a transfer characteristic test on the device, and take the gate voltage corresponding to the set drain current as the threshold voltage;

[0009] (2) Perform electron irradiation treatment on the MOSFET device, and test the threshold voltage of the device after different irradiation doses;

[0010] (3) Gradually increase the irradiation dose in a set step, and test and record the threshold voltage of the device after different irradiation doses;

[0011] (4) Perform negative high-temperature gate bias accelerated aging on the MOSFET device, record the change relationship of the device's threshold voltage with the accelerated aging time under this stress, and obtain the threshold voltage offset amount ΔV of the device under the specified high-temperature gate bias accelerated stress condition A th(A) ;

[0012] (5) According to the relationship between the device threshold voltage and the irradiation dose obtained in step (2), the threshold voltage offset is ΔV th(A) corresponding to the irradiation dose D A ;

[0013] (6) Electron beam irradiation with an irradiation dose of D A is used for accelerated aging to replace the negative high-temperature gate bias accelerated stress condition A for rapid reliability testing of the device, and is used for spot checks during the device manufacturing process.

[0014] A further improvement of the present invention is that the MOSFET device types include silicon and silicon carbide devices, and the conductive channel is an N-type channel or a P-type channel.

[0015] A further improvement of the present invention is that in step (1), the MOSFET device is a power MOSFET device.

[0016] A further improvement of the present invention is that the power MOSFET device includes a packaged single-device, a module, and an unpackaged bare die device.

[0017] A further improvement of the present invention is that in step (1), the initial threshold voltage of the MOSFET device is measured.

[0018] A further improvement of the present invention is that in step (2), the energy of the electron irradiation is 5 - 15 MeV.

[0019] A further improvement of the present invention is that in step (3), the irradiation dose step size is set to 0.01 - 50 kGy.

[0020] A further improvement of the present invention is that the smaller the step size, the more accurate the relationship between the change in the device threshold voltage and the irradiation dose.

[0021] A further improvement of the present invention is that in step (5), the threshold voltage drift caused by electron beam irradiation and negative high-temperature gate bias is due to the injection or generation of electrons / holes in the gate oxide layer, and the trapping of charges by traps in the gate oxide causes the device threshold voltage to drift.

[0022] The present invention has at least the following beneficial technical effects:

[0023] A method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation provided by the present invention can be used for the reliability detection of the device gate oxide layer. This detection method uses electron beam irradiation as an accelerated aging method for the device gate oxide layer to replace the traditional negative high-temperature gate bias aging test and accelerate the device accelerated aging process. This method can be used in the sampling detection process of device manufacturing, which can greatly improve the device spot check efficiency and is convenient for scientific and industrial promotion and use. Description of the Drawings

[0024] Figure 1 It is the flowchart of the method of the present invention.

[0025] Figure 2 It is a schematic diagram of the SiC MOSFET device structure tested in Embodiment 1 of the present invention.

[0026] Figure 3 It is a graph showing the variation of the threshold voltage of the SiC MOSFET device tested in Embodiment 1 of the present invention with the time of high-temperature gate bias stress.

[0027] Figure 4 It is a graph showing the variation of the threshold voltage of the SiC MOSFET device tested in Embodiment 1 of the present invention with the electron irradiation dose.

[0028] Figure 5 It is a schematic diagram of the Si MOSFET device structure tested in Embodiment 2 of the present invention.

[0029] Figure 6 It is a graph showing the variation of the threshold voltage of the Si MOSFET device tested in Embodiment 2 of the present invention with the time of high-temperature gate bias stress.

[0030] Figure 7 It is a graph showing the variation of the threshold voltage of the Si MOSFET device tested in Embodiment 2 of the present invention with the electron irradiation dose. Detailed implementation manners

[0031] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. Hereinafter, the present invention will be described in detail with reference to the drawings and in combination with the embodiments.

[0032] As Figure 1 shown, a method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation provided by the present invention includes the following steps:

[0033] (1) Perform a threshold voltage test on the MOSFET device and record the initial threshold voltage value of the device; perform a transfer characteristic test on the device, and take the gate voltage corresponding to a specific drain current as the threshold voltage (for example, set the drain-source electrode voltage V DS = 10V to perform a transfer characteristic curve test, and select the gate voltage corresponding to a drain current of 1 mA as the threshold voltage of the device).

[0034] (2) Irradiate the above MOSFET device with an electron beam to accelerate device aging and cause the device threshold voltage to degrade;

[0035] (3) Gradually increase the irradiation dose in set steps, and test and record the threshold voltage of the device after different irradiation doses;

[0036] (4) Conduct high-temperature gate bias accelerated aging on the MOSFET device, record the change relationship of the device threshold voltage with the accelerated aging time under this stress, and obtain the change amount ΔV of the device threshold voltage under the specified high-temperature gate bias accelerated stress condition A th(A) ;

[0037] (5) According to the relationship between the device threshold voltage and the irradiation dose obtained in step (2), obtain that the threshold voltage offset is ΔV th(A) corresponding to the irradiation dose D A ;

[0038] (6) Electron beam irradiation accelerated aging with an irradiation dose of D A can be used to replace the high-temperature gate bias accelerated stress condition A to conduct rapid reliability tests on the device and for spot checks during the device manufacturing process.

[0039] The main function of step (1) is: to test and obtain the initial threshold voltage of the MOSFET device. In subsequent steps, the same method as in step (1) is used to test the threshold voltage.

[0040] The main function of step (2) is: The ionization effect of electron beam irradiation can generate electron-hole pairs in the MOSFET gate oxide layer, which are then trapped by the traps in the gate oxide layer, increasing the fixed charges in the MOSFET device gate oxide layer and reducing the device threshold voltage. This is the same as the effect of injecting charges into the gate oxide layer by the electrical stress in the negative high-temperature gate bias test, but the efficiency of generating electron-hole pairs by electron irradiation in the gate oxide layer is much higher.

[0041] In step (2), the energy of the electron beam is 5 - 15 MeV. If the electron energy is too low, the penetration depth is small and the ionization effect is weak, which cannot meet the requirements; if the electron energy is too high, it will cause damage to the sample. Therefore, electrons with appropriate energy need to be selected according to the sample material to irradiate the sample.

[0042] The main function of step (3) is: to obtain the relationship between the device threshold voltage and the irradiation dose, and use it to replace the high-temperature gate bias aging test to conduct reliability tests on the MOSFET device.

[0043] In step (3), the irradiation dose starts from 0 and gradually increases the irradiation dose of the device in set steps. The irradiation dose step can be set to 0.01 - 50 kGy. The smaller the step, the more accurate the relationship between the change in the device threshold voltage and the irradiation dose.

[0044] The main function of step (4) is: to obtain the threshold voltage offset ΔV of the MOSFET device under the specified high-temperature gate bias test condition A th(A) .

[0045] In step (5), the threshold voltage drift caused by electron beam irradiation and high-temperature gate bias is due to the injection or generation of electrons / holes in the gate oxide layer. The trapping of charges by traps in the gate oxide causes the device threshold voltage to drift. Therefore, electron beam irradiation can be used to replace high-temperature gate bias as a method for accelerating aging to evaluate the reliability of the device gate oxide layer against the threshold voltage drift of the device.

[0046] In step (5), the irradiation dose D A is used to test the device instead of the high-temperature gate bias condition A, and it can be used in the sampling inspection process of devices manufactured by the same process to improve the device sampling inspection efficiency.

[0047] Example 1

[0048] In Example 1, a 1200V SiC MOSFET single device is selected, and the structural schematic diagram of the device is as Figure 2 shown.

[0049] (1) Before the accelerated aging treatment, first test the initial threshold voltage of the device: Apply a voltage V DS = 10V between the drain and source electrodes to test the device transfer characteristics, and select the gate voltage V DS when the drain current I GS = 1mA, which is 2.48V, as the initial threshold voltage of the device;

[0050] (2) Select an electron beam with an energy of 10 MeV to irradiate the device, and the irradiation dose rate is 250 kGy / min.

[0051] (3) Gradually increase the irradiation dose of the device, and test the threshold voltage of the device when the total irradiation dose is 1 kGy, 5 kGy, 10 kGy, 50 kGy, 100 kGy, and 200 kGy respectively. The change in the threshold voltage of the MOSFET device with the irradiation dose is as Figure 3 shown.

[0052] (4) Select a temperature T = 175 °C and a gate voltage V GS = -40V stress to conduct an accelerated aging test on the device, and record the relationship between the device threshold voltage and the accelerated stress time, as Figure 4 shown. At a temperature T = 175 °C and a gate voltage VGS Under the stress condition A with temperature T = 175°C, gate voltage V = -40V, and time t = 5000s, the threshold voltage drift ΔV of the device th = -3.3V.

[0053] (5) In Figure 4 the irradiation dose D corresponding to the threshold voltage drift ΔV th = -3.3V is A = 23.2kGy.

[0054] (6) The electron beam irradiation treatment with an available irradiation dose D A = 23.2kGy can be used to replace the stress condition A: temperature T = 175°C, gate voltage V GS = -40V, and time t = 5000s to conduct the reliability test on the MOSFET device.

[0055] Example 2

[0056] In Example 2, a 950V Si MOSFET single device was selected, and the structural schematic diagram of the device is as Figure 5 shown.

[0057] (1) Before the accelerated aging treatment, first test the initial threshold voltage of the device: Apply a voltage V DS = 10V between the drain and source electrodes to test the transfer characteristics of the device, and select the gate voltage V DS = 2.99V when the drain current I GS = 1mA as the initial threshold voltage of the device;

[0058] (2) Use an electron beam with an energy of 10MeV to irradiate the device, and the irradiation dose rate is 250kGy / min.

[0059] (3) Gradually increase the irradiation dose of the device, and test the threshold voltage of the device when the total irradiation doses are 1kGy, 5kGy, 10kGy, 50kGy, 100kGy, and 200kGy respectively. The change of the threshold voltage of the MOSFET device with the irradiation dose is as Figure 6 shown.

[0060] (4) Select the stress condition A with temperature T = 225°C, gate voltage V GS = -50V to conduct the accelerated aging test on the device, and record the relationship between the threshold voltage of the device and the accelerated stress time, as Figure 4 shown. Under the stress condition A with temperature T = 225°C, gate voltage V GS = -50V, and time t = 5000s, the threshold voltage drift ΔV of the device th = -0.44V.

[0061] (5) In Figure 7Among them, the irradiation dose corresponding to the threshold voltage drift amount ΔV th =-0.44V is D A =0.19 kGy.

[0062] (6) The available irradiation dose is D A =0.19 kGy, and electron beam irradiation treatment can be used to replace stress condition A: temperature T = 225 °C, gate voltage V GS =-50V, time t = 5000 s to conduct reliability tests on MOSFET devices.

[0063] In summary, a method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation provided by the present invention has simple steps and high efficiency, and can be used for the spot check process of device manufacturing.

[0064] The above are only limited embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification made within the spirit and principle of the present invention is within the protection scope of the present invention.

Claims

1. A method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation, characterized in that It includes the following steps: (1) Perform threshold voltage and gate oxide capacitance tests on the MOSFET device: Conduct transfer characteristic tests on the device, and take the gate voltage corresponding to the set drain current as the threshold voltage; (2) Perform electron irradiation treatment on the MOSFET device, and test the threshold voltage of the device after different irradiation doses; (3) Gradually increase the irradiation dose in a set step size, and test and record the threshold voltage of the device after different irradiation doses; (4) Perform negative high-temperature gate bias accelerated aging on the MOSFET device, record the variation relationship of the device threshold voltage with the accelerated aging time under this stress, and obtain the threshold voltage offset ΔV of the device under the specified high-temperature gate bias accelerated stress condition A th(A) ; (5) According to the relationship between the device threshold voltage and the irradiation dose obtained in step (2), the threshold voltage offset is obtained as ΔV th(A) corresponding to the irradiation dose D A ; (6) Electron beam irradiation with an irradiation dose of D A is used for accelerated aging by irradiation to quickly perform a reliability test on the device instead of the negative high-temperature gate bias acceleration stress condition A, and is used for spot checks during the manufacturing process of the device.

2. The method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation according to claim 1, characterized in that, The MOSFET device types include silicon and silicon carbide devices, and the conductive channel is an N-type channel or a P-type channel.

3. A method for detecting the reliability of the gate oxide layer of a MOSFET by electron beam irradiation according to claim 1, characterized in that, In step (1), the MOSFET device is a power MOSFET device.

4. A method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation according to claim 3, characterized in that, The power MOSFET device includes a packaged single-tube device, a module, and an unpackaged bare die device.

5. A method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation according to claim 1, characterized in that, In step (1), the initial threshold voltage of the MOSFET device is obtained through testing.

6. The method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation according to claim 1, wherein In step (2), the energy of electron irradiation is 5 - 15 MeV.

7. A method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation according to claim 1, characterized in that, In step (3), the irradiation dose step size is set to 0.01 - 50 kGy.

8. A method for detecting the reliability of the gate oxide layer of a MOSFET by electron beam irradiation according to claim 7, characterized in that, The smaller the step size, the more accurate the relationship between the change in the device threshold voltage and the irradiation dose.

9. The method for detecting the reliability of the MOSFET gate oxide layer by electron beam irradiation according to claim 1, wherein In step (5), the threshold voltage drift caused by electron beam irradiation and high-temperature gate bias is due to the injection or generation of electrons / holes in the gate oxide layer, and the trapping of charges by traps in the gate oxide causes the threshold voltage drift of the device.

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