A characterization test method for ionizing radiation damage to silicon-on-insulator field-effect transistors

Abstract

The present invention relates to a method for characterizing and testing ionizing radiation damage to silicon-on-insulator (SOI) field-effect transistors (FETs). This method belongs to the technical field of quantitative radiation damage testing for semiconductor devices and addresses the technical problem of inaccurate measurement of the peak recombination current before and after total-dose radiation exposure in SOI devices. The method includes testing positive-gate and back-gate transfer characteristic curves, testing the relationship curve between body-terminal recombination current and back-gate voltage, testing total-dose radiation effects and post-irradiation parameters, extracting back-gate depletion voltage using a mid-band voltage method, determining the peak recombination current increment, separating oxide trap charges, and fitting and extracting the average surface density of the trapped charges. This characterization and testing method is used to quantitatively reveal the average surface density of radiation-induced oxide trap charges and interface traps in SOI FETs.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantitative testing of radiation damage of semiconductor devices, and in particular relates to a characterization testing method for ionizing radiation damage of silicon-on-insulator field effect transistors. Background Art

[0002] With the rapid development of aerospace technology and humanity's continued advancement in space exploration, the performance and reliability of aerospace-grade electronic devices have become crucial. In the space radiation environment, electronic devices are exposed to various rays and high-energy particles, which can cause ionizing radiation damage, affecting their performance and even causing device failure. Therefore, semiconductor devices with excellent radiation resistance have become a key research and application priority.

[0003] As a typical semiconductor device, silicon-on-insulator (SOI) field-effect transistors (FETs) have attracted widespread attention due to their excellent radiation resistance. The radiation resistance of SOI FETs primarily stems from their unique structural design. In the SOI structure, the presence of a buried oxide layer prevents electrons generated in the substrate region from being effectively collected, while full dielectric isolation completely eliminates pnpn latch-up within the transistor, giving the structure excellent resistance to single-particle and transient radiation. However, the presence of the buried oxide layer also introduces a large amount of trapped charge, affecting the normal operation of the device. The total dose effect has become a key issue that needs to be addressed in the application of SOI devices in radiation environments. To further investigate the mechanism of radiation effects, it is necessary to accurately assess the degree of damage to ionizing radiation on FETs. This is of great significance for optimizing device design and improving their reliability in extreme environments.

[0004] Existing test methods have some shortcomings in quantitatively characterizing ionizing radiation damage to silicon-on-insulator field-effect transistors. Limited by the variation of the subthreshold slope, the traditional mid-band voltage method is no longer accurate in separating interface trap charges under high-dose rate radiation. The DC current-voltage technology based on indirect recombination theory is an effective method for extracting radiation-induced charge separation. This method uses a more accurate fitting parameter extraction method to avoid simplified functional calculations. It extracts the peak value of the body-end recombination current and the corresponding back-gate voltage when the channel surface is depleted, and then separates the radiation-induced charge. However, this method also has problems. There are interface traps of different energy levels at the Si / SiO2 interface, which leads to the scanning of I B -V BG The curve peak is flattened or has multiple peak characteristics, which makes it impossible to obtain accurate back gate depletion voltage and body-end recombination current peak. Excessive or small source / drain-body PN junction voltage may also increase the uncertainty of the body-end recombination current peak. Summary of the Invention

[0005] In order to overcome the deficiency of inaccurate measurement of the peak value of the composite current before and after the total dose radiation of silicon-on-insulator process devices, the present invention proposes a characterization test method for ionizing radiation damage of silicon-on-insulator process field effect transistors.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A characterization and testing method for ionizing radiation damage to silicon-on-insulator field-effect transistors includes the following steps:

[0008] Step 1: Test the positive gate and back gate transfer characteristic curves of the silicon-on-insulator process effect transistor before irradiation to obtain the positive gate inversion voltage.

[0009] Step 2: Fix the inversion voltage obtained in step 1 at the positive gate terminal, fix the body terminal to 0V, apply the same positive bias voltage to the source and drain terminals, determine the back gate scanning voltage range and scanning step length, and obtain the body terminal recombination current I under the source / drain-body voltage before irradiation. B With the back gate voltage V BG The changing relationship curve.

[0010] Step 3: Conduct the total dose radiation effect test of the silicon-on-insulator field effect transistor, repeat steps 1 and 2, and obtain the transfer characteristic curve after irradiation and I B -V BG Relationship curve.

[0011] Step 4: Use the mid-band voltage method to calculate the mid-band current I before and after irradiation using the transfer characteristic curves obtained in steps 1 and 3. mg , the mid-band current I before and after irradiation is obtained mg The back gate depletion voltage V before and after irradiation is obtained by the back gate transfer characteristic curve BG,mg .

[0012] Step 5: Compare the back gate depletion voltage V before and after irradiation obtained in step 4 BG,mg By I B -V BG The peak value of the composite current I before and after irradiation is obtained from the relationship curve B-peak , and subtract it from the baseline current value to obtain ΔI before and after irradiation B-peak .

[0013] Step 6: V before and after irradiation obtained in step 4 and step 5 BG,mg and ΔI B-peak The average trapped charge density generated by ionizing radiation is quantitatively extracted by equations (2) and (3), completing the characterization test of ionizing radiation damage of silicon-on-insulator field-effect transistors.

[0014]

[0015] In formula (2), ΔV BG,mg V before and after irradiation BG,mg The difference, ΔN ot represents the average surface density of oxide trap charges in the buried oxide layer, C box Represents the buried oxide capacitance per unit area.

[0016]

[0017] In formula (3), q is the electron charge, A is the interface area, and the product of the channel length and the channel width is taken. N it is the average surface density of back gate interface traps, c ns with c ps are the capture rate coefficients of electrons and holes, respectively, n i is the intrinsic carrier concentration, n i =10 -10 cm -3 , V PN is the bias voltage of the source / drain-body junction, k and T represent the Boltzmann constant and temperature respectively, E TI represents the interface trap equivalent energy level.

[0018] The characterization test method for ionizing radiation damage of silicon-on-insulator field effect transistors mentioned above, in step 2, source / drain-body terminal V PN The bias voltage range is:

[0019] 0.4V <V PN <0.7V

[0020] The source PN junction and the drain PN junction are both forward biased, and their voltages are as small as possible to satisfy the Boltzmann statistical distribution close to the thermal equilibrium state.

[0021] In the above-mentioned characterization test method for ionizing radiation damage of silicon-on-insulator field-effect transistors, the total dose radiation test device in step 3 can be a gamma-ray or X-ray irradiation device.

[0022] In the above-mentioned characterization test method for ionizing radiation damage of silicon-on-insulator field effect transistor, the current I mg The calculation formula is as follows:

[0023]

[0024] In formula (1), G Mmax is the maximum transconductance, V DS is the drain-source voltage in the linear region, β=q / kT, where t boxis the buried oxide thickness of the back-gate transistor, ε s With ε ox Represent the dielectric constants of silicon and oxide, L D represents the Debye length, and N represents the doping concentration of the body region.

[0025] In the above-mentioned characterization test method for ionizing radiation damage of silicon-on-insulator field effect transistors, the baseline current value in step 5 represents the recombination current I that does not change with the back gate voltage scan. B value.

[0026] In the above-mentioned characterization and testing method for ionizing radiation damage of silicon-on-insulator field effect transistors, in step 6 of extracting the oxide trap charge density, the buried oxide capacitance C box The calculation formula is as follows:

[0027]

[0028] In formula (4), ε ox is the dielectric constant of oxide, t box is the buried oxide thickness of the back-gate transistor;

[0029] In the above-mentioned characterization test method for ionizing radiation damage of silicon-on-insulator field effect transistor, in step 6, the interface trap density is extracted according to different V PN and ΔI B-peak The discrete relationship is established by custom function fitting to obtain the parameter E TI With N it .

[0030] The beneficial effects of the present invention are:

[0031] A characterization test method for ionizing radiation damage to silicon-on-insulator field-effect transistors (SOI field-effect transistors) combines theoretical models with experimental data to accurately analyze the damage mechanism of ionizing radiation on SOI field-effect transistors, thereby improving the scientific nature and accuracy of test results.

[0032] A characterization test method for ionizing radiation damage in silicon-on-insulator field-effect transistors (FETs) is developed. This method addresses issues such as inaccurate recombination current peaks by combining the mid-band voltage method with the DC current-voltage method. A reasonable source / drain-body junction voltage range is provided to effectively extract the back-gate depletion voltage, increasing accuracy and applicability.

[0033] A characterization and testing method for ionizing radiation damage to silicon-on-insulator field-effect transistors helps improve the design and manufacturing process of devices and enhance their reliability in space radiation environments. It has significant application value and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a longitudinal cross-sectional view of a silicon-on-insulator field effect transistor with a double buried oxide layer structure;

[0035] Figure 2 The test results of positive gate transfer characteristic curve of silicon-on-insulator field effect transistor before irradiation are shown;

[0036] Figure 3 The back-gate transfer characteristic curve test results of silicon-on-insulator field-effect transistors after 3000krad (Si) dose irradiation are shown in Figure 2.

[0037] Figure 4 The following are the test results of the body-terminal recombination current and back-gate voltage curves of the silicon-on-insulator field-effect transistor after 3000 krad (Si) dose irradiation. The labels 1, 2, 3, 4, 5, and 6 are the body-terminal recombination current and back-gate voltage curves when the source-drain-body junction voltage is 0.56V, 0.55V, 0.54V, 0.53V, 0.52V, and 0.51V, respectively.

[0038] Figure 5 Figure 3 shows the discrete relationship between the peak increment of the body-side recombination current and the forward-biased source / drain-body junction voltage after irradiation with a dose of 3000 krad (Si). The points in the figure are the experimental results of the peak increment of the recombination current at different source / drain-body junction voltages, and the lines are the fitting results of the extracted interface trap charge.

[0039] Figure 6 The average surface density of trapped charges at each dose point of the isolated silicon-on-insulator field-effect transistor is shown in Figure 7. Labels 7 and 8 represent the extracted oxide trap charge density and interface trap charge density, respectively.

[0040] Figure 7 This is a flow chart of the characterization test method of Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Example 1

[0043] A characterization test method for ionizing radiation damage in silicon-on-insulator field-effect transistors (SOIs) is a radiation-induced trapped charge separation technique that combines the mid-band voltage method with the DC current-voltage method. It can quantitatively reveal the average surface density of radiation-induced oxide trap charges and interface traps in SOIs. The specific operation includes the following steps (see the process for details). Figure 7 ):

[0044] Step 1: Use the B1500A semiconductor parameter analyzer to test the forward gate and back gate transfer characteristic curves of the silicon-on-insulator process field effect transistor before irradiation. The device under test is a silicon-on-insulator process n-type field effect transistor with a double buried oxide layer structure, with a channel width and a channel length of 5μm and 0.18μm respectively. Its longitudinal cross-section is shown in FIG. Figure 1 As shown. Figure 2 This is the positive gate transfer characteristic curve of the silicon-on-insulator field effect transistor before irradiation, and the positive gate inversion voltage is 1.8V.

[0045] Step 2: Fix the inversion voltage of 1.8V at the positive gate terminal, fix the body terminal to 0V, apply the same positive bias voltage to the source and drain terminals, and the source / drain-body terminal V PN The bias voltage range is 0.4V to 0.7V. Both the source-body PN junction and the drain-body PN junction are kept forward biased, and their voltage is as small as possible to meet the Boltzmann statistical distribution close to the thermal equilibrium state. PN The bias voltage is changed every 0.01V, ranging from 0.51V to 0.56V.

[0046] Determine the back gate scanning voltage range and scanning step size, back gate voltage V BG The scanning range was -15~25V with a scanning step of 0.5V, and the body terminal composite current I was obtained at different source / drain-body voltages. B With the back gate voltage V BG The changing relationship curve.

[0047] Step 3: Conduct a total dose radiation effect test on silicon-on-insulator field effect transistors. Use a γ-ray or X-ray irradiation device to repeat steps 1 and 2 to obtain the positive gate back gate transfer characteristic curve and I B -V BG Relationship curve, Figure 3 The figure shows the test results of the back-gate transfer characteristic curve of the silicon-on-insulator field effect transistor after irradiation with a dose of 3000 krad (Si). Figure 4 Shown in the figure are the test results of the body-terminal recombination current and back-gate voltage curves of the silicon-on-insulator process field effect transistor after 3000krad (Si) dose irradiation.

[0048] Step 4: Calculate the mid-band current I using the mid-band voltage method using the transfer characteristic curves obtained in steps 1 and 3. mg , where the middle band current I mg The calculation formula is as follows:

[0049]

[0050] In formula (1), G Mmax is the maximum transconductance, VDS is the drain-source voltage in the linear region, β=q / kT, where t box is the buried oxide thickness of the back-gate transistor, ε s With ε ox Represent the dielectric constants of silicon and oxide, L D represents the Debye length, N represents the body doping concentration, q is the electron charge, k and T represent the Boltzmann constant and temperature, respectively.

[0051] Through Figure 3 The calculation of the back-gate transfer characteristic curve of the silicon-on-insulator field effect transistor after irradiation with a dose of 3000 krad (Si) can obtain the mid-band current I mg =1.244*10 -14 A, the mid-band current I obtained after irradiation mg The back gate depletion voltage V after 3000krad (Si) irradiation is obtained through the back gate transfer characteristic curve. BG,mg =-6.576V.

[0052] Step 5: Compare the back gate depletion voltage V before and after irradiation obtained in step 4 BG,mg By I B -V BG The peak value of the composite current I before and after irradiation is obtained from the relationship curve B-peak , and subtract it from the baseline current value to obtain the composite current peak increment ΔI before and after irradiation. B-peak , where the baseline current value represents the recombination current I that does not change with the back gate voltage scan B value.

[0053] Step 6: V obtained in step 4 and step 5 BG,mg and ΔI B-peak The average trapped charge density generated by ionizing radiation is quantitatively extracted by equations (2) and (3), completing the characterization test of ionizing radiation damage of silicon-on-insulator field-effect transistors.

[0054]

[0055] In formula (2), ΔV BG,mg V before and after irradiation BG,mg The difference, ΔN ot represents the average surface density of oxide trap charges in the buried oxide layer, C box1 Represents the buried oxide capacitance per unit area.

[0056]

[0057] In formula (3), q is the electron charge, A is the interface area, and the product of the channel length and the channel width is taken. N it is the average surface density of back gate interface traps, c ns with c ps are the capture rate coefficients of electrons and holes, respectively, n i is the intrinsic carrier concentration, n i =10 -10 cm -3 , V PN is the bias voltage of the source / drain-body junction, k and T represent the Boltzmann constant and temperature respectively, and E TI represents the interface trap equivalent energy level.

[0058] In the extraction of interface trap charge density, according to different V PN and ΔI B-peak The discrete relationship is established by custom function fitting to obtain the parameter E TI With N it , Figure 5 The figure shows the discrete relationship between the peak increment of the body-end recombination current and the forward biased source / drain-body junction voltage after 3000krad (Si) dose irradiation. The average surface density of interface traps N can be obtained by fitting the curve. it =7.62426*10 11 cm -2 , the equivalent interface trap energy level E TI =0.22809eV.

[0059] In step 6, the oxide trap charge density is extracted, and the buried oxide capacitance C box1 The calculation formula is as follows:

[0060]

[0061] In formula (4), ε ox is the dielectric constant of oxide, t box1 is the thickness of the buried oxide BOX1 layer of the back-gate transistor;

[0062] By combining the mid-band voltage method with the DC current voltage method, the following can be separated: Figure 6 The average surface density of trapped charges at various dose points of the silicon-on-insulator field-effect transistor shown in the figure completes the quantitative test of the ionizing radiation damage to the device, which shows that this method is objective and reasonable.

Claims

1. A characterization test method for ionizing radiation damage of silicon-on-insulator field-effect transistors, characterized in that: The following steps are involved: Step 1, positive gate and back gate transfer characteristic curve test: Before irradiation, the positive gate and back gate transfer characteristic curves of the silicon-on-insulator field effect transistor are tested using a semiconductor parameter analyzer to obtain the positive gate inversion voltage of the silicon-on-insulator field effect transistor; Step 2: Test the relationship curve between the body-end recombination current and the back gate voltage: fix the positive gate inversion voltage obtained in step 1 at the positive gate end, fix the body end to 0V, and apply the same positive bias voltage to the source and drain ends; set the back gate scanning voltage range and scanning step length to obtain the body-end recombination current I under the source / drain-body voltage before irradiation. B With the back gate voltage V BG Changing relationship curve; Step 3: Total dose radiation effect test and post-irradiation parameter test: Using a total dose radiation test device, perform total dose irradiation on the silicon-on-insulator field effect transistor according to the set total irradiation dose; The total dose radiation effect of silicon-on-insulator field-effect transistors was tested to obtain the forward gate and back gate transfer characteristic curves after irradiation, and the body terminal recombination current I under different source / drain-body voltages. B With the back gate voltage V BG Changing relationship curve; Step 4: Extract the back gate depletion voltage using the mid-band voltage method: Based on the forward gate and back gate transfer characteristic curves before and after irradiation, the mid-band current I before and after irradiation is obtained using the mid-band voltage method. mg ; Combined with the back gate subthreshold curve, the back gate depletion voltage V before and after irradiation is obtained BG,mg ; Step 5: Calculate the peak value increment of the recombination current: Based on the back gate depletion voltage V before and after irradiation BG,mg , and I before and after irradiation B -V BG Relationship curve, calculate the composite current peak value I before and after irradiation B-peak Combined with the baseline current value, calculate the composite current peak increment ΔI before and after irradiation B-peak ; Step 6: Separate the oxide trap charges and extract the average surface density of the trapped charges by fitting: Use a combination of the mid-band voltage method and the DC current-voltage method to extract the average surface density of the trapped charges at each dose point of the silicon-on-insulator field-effect transistor, completing the characterization test of the ionizing radiation damage of the silicon-on-insulator field-effect transistor.

2. The characterization test method according to claim 1, characterized in that: The silicon-on-insulator field effect transistor is a silicon-on-insulator n-type field effect transistor with a double buried oxide layer structure, and the channel width and channel length are 5 μm and 0.18 μm respectively.

3. The characterization test method according to claim 1, characterized in that: In step 2, the back gate scanning voltage range and scanning step length are set, and the back gate voltage V BG The scanning range was -15 to 25 V, with a scanning step of 0.5 V, and the body terminal composite current I was obtained under different source / drain-body voltages before irradiation. B With the back gate voltage V BG The changing relationship curve.

4. The characterization test method according to claim 1, characterized in that: In step 3, the total dose radiation test device adopts an X-ray irradiation device.

5. The characterization test method according to claim 1, characterized in that: The step 4 further includes: obtaining the mid-band current I before and after irradiation mg , the calculation formula is: In formula (1), G Mmax is the maximum transconductance, V DS is the drain-source voltage in the linear region, β=q / kT, where t box is the thickness of the buried oxide BOX layer of the back-gate transistor, ε s With ε ox Represent the dielectric constants of silicon and oxide, L D represents the Debye length, N represents the body region doping concentration, q is the electron charge, and n i is the intrinsic carrier concentration, k and T represent the Boltzmann constant and temperature, respectively.

6. The characterization test method according to claim 1, characterized in that: The composite current peak increment ΔI before and after irradiation B-peak The peak value of the composite current before and after irradiation is I B-peak Subtract the baseline current value.

7. The characterization test method according to claim 1, characterized in that: The step 6 further comprises: The average surface density of trapped charges at each dose point of the silicon-on-insulator field-effect transistor includes: the average surface density of oxide trapped charges in the buried oxide layer and the average surface density of back gate interface traps; The average surface density of oxide trap charges in the buried oxide layer is extracted and calculated as follows: In formula (2), ΔV BG,mg V before and after irradiation BG,mg The difference, ΔN ot represents the average surface density of oxide trap charges in the buried oxide layer, C box represents the buried oxide capacitance per unit area, and q is the electron charge; The average surface density of back gate interface traps is extracted and calculated as follows: In formula (3), q is the electron charge, A is the interface area, and the product of the channel length and the channel width is taken. N it is the average surface density of back gate interface traps, c ns with c ps are the capture rate coefficients of electrons and holes, respectively, n i is the intrinsic carrier concentration, n i =10 -10 cm -3 , V PN is the bias voltage of the source / drain-body junction, k and T represent the Boltzmann constant and temperature respectively, E TI represents the interface trap equivalent energy level.

8. The characterization test method according to claim 7, characterized in that: In the extraction of the average surface density of oxide trap charges in the buried oxide layer, the buried oxide capacitance C box The calculation formula is as follows: In formula (4), ε ox is the dielectric constant of oxide, t box is the thickness of the buried oxide BOX layer of the back-gate transistor.

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