Method for acquiring equivalent silicon layer thickness and single event upset LET threshold value of device

Abstract

The invention relates to a method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold value of a device, belongs to the technical field of space radiation effect simulation experiment and radiation hardening, and solves the technical problem that the equivalent silicon layer thickness and the single event upset LET threshold value of the device are difficult to obtain. The acquisition method comprises the following steps: calculating average proton energy and an LET value and a range in silicon; acquiring a relation curve between the single event upset cross section of the device and the average proton energy; extracting the upper and lower limits of energy corresponding to the single event upset section peak of the low-energy proton of the device; calculating the equivalent silicon layer thickness of the device based on the energy lower limit; calculating a proton range, energy and an LET value in the sensitive volume of the device based on the energy upper limit; calculating a proton range, energy and an LET value in the sensitive volume based on the proton which is higher than and closest to the energy upper limit; and a step of obtaining an LET threshold value of single event upset of the device. According to the method, the equivalent silicon layer thickness and the single event upset LET threshold value of the device can be accurately obtained.

Description

Technical Field

[0001] The invention belongs to the field of space radiation effect simulation experiment technology and radiation resistance reinforcement technology, and specifically relates to a method for obtaining a device equivalent silicon layer thickness and a single event upset LET threshold. Background Art

[0002] Heavy ions and protons are the main sources of single-particle effects in electronic devices in space radiation environments. In device heavy ion single-particle effect experiments, it is usually necessary to fit the Weibull function based on the device heavy ion single-particle flip cross-section experimental data to evaluate the device's ability to resist single particles and estimate the device's on-orbit single-particle flip rate. Because the lower the heavy ion LET value is in the space radiation environment, the higher the flux is. Therefore, the determination of the device heavy ion single-particle flip LET threshold is particularly important for function fitting and on-orbit estimation. The LET threshold refers to the minimum LET value required for the device to have a single-particle effect. It is difficult to directly obtain this value through heavy ion single-particle effect experimental data. If it is obtained based on Weibull function fitting of heavy ion single-particle effect experimental data, there will be a large error. On the other hand, with the development of device technology, there are multiple metal wiring layers of several microns to tens of microns above the sensitive area of ​​the upright device, and there is a silicon substrate of several hundred microns above the sensitive area of ​​the flip-chip device, which will lead to a significant difference between the effective LET value of the heavy ions in the sensitive area of ​​the device and the LET value on the device surface. However, experimenters usually lack understanding of the specific process information of the device, as well as the information of the metal wiring layer and substrate above the sensitive volume of the device. This makes it difficult to accurately determine the effective LET value of the heavy ions reaching the sensitive volume of the device in heavy ion single particle effect experiments. This will introduce a greater source of error for heavy ion experimental data with a shorter range.

[0003] Therefore, based on the above problems and current situation, it is necessary to develop a new method to obtain the equivalent silicon layer thickness of the device and the LET threshold of the single-particle upset. As the device technology develops to the nanoscale, the critical charge of the device single-particle upset is reduced to below 1fc, and the LET threshold is as low as 0.1MeV.cm 2 / mg. Since the LET value of proton direct ionization does not exceed 0.55MeV.cm 2 / mg, with low energy loss, it can effectively pass through the device's multi-layer metal wiring layer or the thick substrate of the flip-chip device to reach the device's sensitive volume. For nanodevices, low-energy protons with energy less than 1MeV in the sensitive volume can trigger high-cross-section single-particle flips through direct ionization. Based on this, a method for determining the equivalent silicon layer thickness above the device's sensitive volume and the single-particle flip LET threshold based on low-energy proton experimental data is proposed, which has practical significance for scientifically evaluating the device's resistance to heavy ion single-particle performance and achieving accurate estimation of the on-orbit error rate.

[0004] The Chinese invention patent with publication number CN100538378C discloses a method for obtaining the relationship between the single particle effect cross section and the heavy ion linear energy transfer. The invention provides an experimental method for testing the heavy ion single particle effect cross section of the device based on a heavy ion accelerator; the Chinese invention patent with publication number CN112230081A discloses a method for calculating the equivalent LET value of a pulsed laser single particle effect experiment. The invention provides a method for using pulsed laser single particle experimental data to calculate the equivalent single particle effect cross section of heavy ions with different LET values. The Chinese invention patent with publication number CN113109859A discloses a method for obtaining a low LET value heavy ion single particle flip cross section. The invention provides a method for obtaining a low LET value single particle flip cross section using low energy proton experimental data. None of these three patents involve a method for obtaining the equivalent silicon layer thickness above the device sensitive volume and the single particle flip LET threshold through low energy proton experimental data. Summary of the invention

[0005] In order to overcome the problem that the equivalent silicon layer thickness of a device and the single event upset LET threshold are difficult to obtain, the present invention proposes a method for obtaining the equivalent silicon layer thickness of a device and the single event upset LET threshold.

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

[0007] A method for obtaining the equivalent silicon layer thickness of a device and a single event upset LET threshold comprises the following steps:

[0008] Step S1, calculate the average proton energy and LET value and range in silicon

[0009] Based on the device information, the proton accelerator and initial proton energy are selected. The SRIM software is used to calculate the average proton energy reaching the device surface after the initial proton energy passes through aluminum foils of different thicknesses, as well as the LET value and range in silicon.

[0010] Step S2, obtaining the relationship curve between the single event upset cross section and the average proton energy of the device

[0011] Conduct low-energy proton single-particle effect experiments on the device and obtain the relationship curve between the single-particle flip cross-section of the device and the average proton energy.

[0012] Step S3: extract the energy upper and lower limits corresponding to the low-energy proton single-particle upturn cross-section peak of the device

[0013] Based on the experimental data of low-energy proton single-particle effect of the device, the low-energy proton single-particle flip cross-section peak of the device is extracted, and the upper and lower limits of the proton energy corresponding to the cross-section peak are recorded.

[0014] Step S4, calculating the equivalent silicon layer thickness of the device

[0015] Based on the energy lower limit corresponding to the low-energy proton single particle upturn cross-section peak and the silicon range corresponding to the energy lower limit, the equivalent silicon layer thickness above the device sensitive volume, that is, the device equivalent silicon layer thickness, is calculated.

[0016] Step S5, obtaining the proton range, energy and LET value of the proton with the upper energy limit reaching the sensitive volume of the device

[0017] Based on the energy upper limit corresponding to the low-energy proton single particle upturn cross-section peak, the range in silicon corresponding to the energy upper limit, and the equivalent silicon layer thickness of the device, the proton range, energy and LET value reaching the sensitive volume of the device are calculated.

[0018] Step S6, obtaining the proton range, energy and LET value of the proton that is higher than and closest to the energy upper limit and reaches the sensitive volume of the device

[0019] Based on the proton energy that is higher than the single-particle upset cross-section peak energy upper limit and closest to the energy upper limit, the corresponding range in silicon, and the equivalent silicon layer thickness of the device, the proton range, energy and LET value reaching the sensitive volume of the device are calculated.

[0020] Step S7, obtaining the LET threshold of the single event upset of the device

[0021] The LET value of the proton at the energy upper limit in the device sensitive volume obtained in step S5 and the LET value of the proton above and closest to the energy upper limit in the device sensitive volume obtained in step S6 are averaged to obtain the device single event upset LET threshold.

[0022] The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the above device, the step S2 further comprises:

[0023] In the experiment, based on the calculation results of step S1, the initial energy protons are made to pass through energy-reducing sheets of different thicknesses to reach the device surface, so as to obtain different average proton energies on the device surface. The single particle upset cross sections of the device are measured in order from high to low according to the proton energy. The calculation formula of the single particle upset cross section σ is as follows:

[0024]

[0025] Where σ is the single-event upset cross section, N is the number of single-event upsets, F is the incident proton fluence, and M is the device storage capacity.

[0026] The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the above device, the step S4 further comprises:

[0027] The equivalent silicon layer thickness of the device is: the silicon range corresponding to the lower limit of the low-energy proton single particle upturn cross-section peak energy minus the thickness of the device sensitive volume.

[0028] The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the above-mentioned device, the sensitive volume thickness of the device is 1 micron.

[0029] The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the above device, the step S5 further comprises:

[0030] According to the energy upper limit corresponding to the low-energy proton single particle upset cross section peak, based on the calculation result of step S1, the silicon range corresponding to the energy upper limit is obtained.

[0031] The silicon range corresponding to the energy upper limit is subtracted from the thickness of the equivalent silicon layer of the device to obtain the silicon range of protons reaching the sensitive volume of the device.

[0032] The proton energy and LET values ​​corresponding to the silicon range of protons in the sensitive volume are calculated using the SRIM software.

[0033] The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the above device, the step S6 further comprises:

[0034] The proton energy that is higher than the upper limit of the single event upset cross section peak energy and closest to the upper limit of the energy is extracted, and based on the calculation result of step S1, the silicon range corresponding to the energy is obtained.

[0035] The silicon mid-range corresponding to the proton energy that is higher than the single particle upside down cross-section peak energy upper limit and closest to the energy upper limit is subtracted from the thickness of the device's equivalent silicon layer to obtain the proton silicon mid-range that reaches the device's sensitive volume.

[0036] The proton energy and LET values ​​corresponding to the silicon range of protons in the sensitive volume are calculated using the SRIM software.

[0037] The beneficial effects of the present invention are:

[0038] A method for obtaining the equivalent silicon layer thickness of a device and the single-event upset LET threshold can obtain the equivalent silicon layer thickness above the sensitive volume of the device without longitudinal sectioning and scanning electron microscope analysis of the device, thereby accurately determining the effective LET value of heavy ions in the sensitive volume of the device and improving the accuracy of heavy ion experimental data.

[0039] A method for obtaining the equivalent silicon layer thickness and single-particle flip LET threshold of a device can accurately obtain the single-particle flip LET threshold of the device based on a low-energy proton single-particle effect experiment of a nanodevice, thereby reducing the dependence on the beam conditions of a heavy ion accelerator and effectively improving the Weibull function fitting accuracy of heavy ion experimental data. This method has important practical significance for scientifically evaluating the device's resistance to heavy ion single-particle performance and achieving accurate prediction of the on-orbit error rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of the acquisition method of Embodiment 2 of the present invention;

[0041] Figure 2 It is the relationship curve between the low-energy proton single-particle upside-down cross section of the device and the average proton energy on the device surface. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Embodiment 1

[0044] The invention discloses a method for obtaining the equivalent silicon layer thickness of a device and a single-particle flip (LET) threshold value, comprising: calculating the average proton energy reaching the device surface after the initial proton energy passes through aluminum foils of different thicknesses, the LET value in silicon and the range; carrying out a low-energy proton single-particle effect experiment, and measuring the relationship curve between the single-particle flip cross section and the average proton energy of a nano device; extracting the proton energy range and the upper and lower energy limits corresponding to the low-energy proton single-particle flip cross section peak of the device; based on the silicon mid-range corresponding to the cross section peak energy lower limit, subtracting the device sensitive volume thickness, and obtaining the equivalent silicon layer thickness above the device sensitive volume; based on the silicon mid-range corresponding to the cross section peak energy upper limit, subtracting the equivalent silicon layer thickness, and calculating the proton range, energy and corresponding LET value reaching the device sensitive volume; extracting the proton energy and silicon mid-range that are higher than the cross section peak energy upper limit and closest to the energy upper limit, subtracting the equivalent silicon layer thickness, and calculating the proton range, energy and corresponding LET value reaching the device sensitive volume; averaging the above two LET values ​​to obtain the device single-particle flip (LET) threshold value. This method can effectively improve the accuracy of device heavy ion single-particle effect experimental data and on-orbit estimation accuracy. It specifically includes the following steps:

[0045] Step S1, select the proton accelerator and initial proton energy, and use SRIM software to calculate the average proton energy reaching the device surface and the LET value and range in silicon after the initial proton energy passes through aluminum foils of different thicknesses. Specifically:

[0046] Based on the preliminary understanding of the device information, a suitable proton accelerator and initial proton energy are selected to carry out low-energy proton single-particle effect experiments on nanodevices.

[0047] Step S2, based on the proton accelerator, conduct a low-energy proton single-particle effect experiment on nano-devices to obtain a curve of the relationship between the single-particle flip cross section of the device and the average proton energy. Specifically:

[0048] In the experiment, based on the calculation results of step S1, the initial energy protons are made to pass through energy-reducing sheets of different thicknesses to reach the device surface, so as to obtain different average proton energies on the device surface. The single particle upside-down cross sections of the device are measured in order from high to low proton energies. The calculation formula of the single particle upside-down cross section σ is as follows:

[0049]

[0050] Where σ is the single-event upset cross section of the device, N is the number of single-event upsets, F is the incident proton flux, and M is the device storage capacity.

[0051] Step S3, extracting the low-energy proton single-particle upturn cross-section peak of the device, and recording the proton energy range and energy upper and lower limits corresponding to the cross-section peak.

[0052] Step S4, based on the energy lower limit corresponding to the low-energy proton single-particle upturn cross-section peak and the silicon range corresponding to the energy lower limit calculated in step S1, calculate the equivalent silicon layer thickness above the device sensitive volume. Specifically:

[0053] The equivalent silicon layer thickness above the device sensitive volume can be obtained by subtracting 1 micron from the silicon range corresponding to the lower limit of the low-energy proton single-particle upturn cross-section peak energy calculated in step S1.

[0054] Step S5, based on the energy upper limit corresponding to the low-energy proton single particle upset cross section peak and the range in silicon, combined with the equivalent silicon layer thickness of step S4, calculate the proton range, energy and corresponding LET value reaching the device sensitive volume. Specifically:

[0055] 5.1) According to the energy upper limit corresponding to the low-energy proton single particle upset cross section peak, the silicon range corresponding to the energy upper limit is obtained based on the calculation result of step S1.

[0056] 5.2) Subtract the equivalent silicon layer thickness obtained in step S4 from the silicon range corresponding to the energy upper limit to obtain the silicon range of the protons reaching the sensitive volume of the device.

[0057] 5.3) Using SRIM software, calculate the proton energy and proton LET value corresponding to the proton silicon range within the sensitive volume in 5.2).

[0058] Step S6, extract the proton energy and silicon range that is higher than the single-particle upset cross-section peak energy upper limit and closest to the energy upper limit, and calculate the proton range, energy and corresponding LET value reaching the device sensitive volume in combination with the equivalent silicon layer thickness in step S4. Specifically:

[0059] 6.1) Extract the proton energy that is higher than the upper limit of the single-particle upset cross-section peak energy and closest to the upper limit of the energy, and obtain the silicon range corresponding to the energy based on the calculation result of step S1.

[0060] 6.2) Subtract the equivalent silicon layer thickness obtained in step S4 from the silicon mid-range in 6.1) to obtain the proton silicon mid-range reaching the device sensitive volume.

[0061] 6.3) Using SRIM software, calculate the proton energy and proton LET value corresponding to the proton silicon range within the sensitive volume in 6.2).

[0062] Step S7, averaging the proton LET value calculated and obtained in step S5 and the proton LET value calculated and obtained in step S6, so as to obtain the LET threshold of the single event upset of the device.

[0063] Embodiment 2

[0064] Figure 1 The present invention is a flow chart of a method for obtaining the equivalent silicon layer thickness and single event upset LET threshold of a device based on the low-energy proton experimental data of the device, combined with Figure 1 , the steps of this method are described in detail.

[0065] Step S1, the device is a normal device, a low-energy proton accelerator is selected, the initial proton energy is selected as 1.2 MeV, and the SRIM software is used to calculate the average proton energy reaching the device surface after the 1.2 MeV proton passes through aluminum foils of different thicknesses, as well as the LET value and range in silicon. Table 1 shows the average proton energy after the initial proton energy of 1.2 MeV passes through aluminum foils of different thicknesses and the corresponding LET value and range in silicon.

[0066] Table 1

[0067]

[0068] Step S2, conduct a low-energy proton single-particle effect experiment, use energy-reducing sheets of different thicknesses to achieve rapid switching of proton energy, and measure the relationship curve between the single-particle flip cross section of the device and the average proton energy from high to low energy, until no single-particle flip occurs. Figure 2 .

[0069] Step S3, extracting the low-energy proton single particle upset cross-section peak of the device, and recording the proton energy range corresponding to the cross-section peak as 0.67MeV to 0.83MeV, with an upper energy limit of 0.83MeV and a lower energy limit of 0.67MeV.

[0070] Step S4, in step S1, the range in silicon corresponding to the lower limit of the peak energy of the low-energy proton single particle upturn cross section of 0.67 MeV in Table 1 corresponds to 9.0 microns, minus the thickness of the device sensitive volume of 1 micron, the equivalent silicon layer thickness above the device sensitive volume can be obtained as 8 microns.

[0071] Step S5, the range in silicon corresponding to the upper limit of the low-energy proton single-particle upset cross section peak energy of 0.83 MeV in Table 1 is 12.4 microns. Subtracting the equivalent silicon layer thickness of the device in step S4 of 8 microns, the range in silicon of the protons reaching the sensitive area of ​​the device is 4.4 microns. Using SRIM software, the proton energy corresponding to the range of 4.4 microns is calculated to be 0.40 MeV, and the corresponding LET value is 0.284 MeV.cm 2 / mg.

[0072] Step S6, extract the proton energy that is higher than the upper limit of the single-particle upset cross-section peak energy and closest to the upper limit of the energy, which is 0.88 MeV. In Table 1, the range in silicon corresponding to this energy is 13.5 microns. Subtract the equivalent silicon layer thickness of 8 microns obtained in step S4, and the range of the proton in silicon that reaches the sensitive area of ​​the device is 5.5 microns. Using SRIM software, the proton energy corresponding to the range of 5.5 microns is calculated to be 0.47 MeV, and the corresponding LET value is 0.264 MeV.cm 2 / mg.

[0073] Step S7: convert the proton LET value 0.286 MeV.cm obtained in step S5 into 2 / mg and the proton LET value obtained in step S6 is 0.264MeV.cm 2 / mg is averaged to obtain the LET threshold of the single-particle upset of the device as 0.275MeV.cm 2 / mg.

Claims

1. A method for obtaining the equivalent silicon layer thickness of a device and the single event upset LET threshold, characterized in that: The following steps are involved: Step S1, calculate the average proton energy and the LET value and range in silicon: Based on the device information, the proton accelerator and initial proton energy were selected, and the average proton energy reaching the device surface, the LET value and the range in silicon were calculated using SRIM software after the initial proton energy passed through aluminum foils of different thicknesses. Step S2, obtaining the relationship curve between the single event upset cross section and the average proton energy of the device: Conduct low-energy proton single-particle effect experiments on devices and obtain the relationship curve between the single-particle flip cross section of the device and the average proton energy; Step S3, extracting the energy upper and lower limits corresponding to the low-energy proton single-particle upturn cross-section peak of the device: Based on the experimental data of low-energy proton single-particle effect of the device, the cross-section peak of low-energy proton single-particle flipping of the device is extracted, and the upper and lower limits of the proton energy corresponding to the cross-section peak are recorded; Step S4, calculating the equivalent silicon layer thickness of the device: Based on the energy lower limit corresponding to the low-energy proton single particle upturn cross section peak and the silicon range corresponding to the energy lower limit, the equivalent silicon layer thickness above the device sensitive volume is calculated, that is, the device equivalent silicon layer thickness; Step S5, obtaining the proton range, energy and LET value of the proton with the energy upper limit reaching the sensitive volume of the device: based on the energy upper limit corresponding to the low-energy proton single particle upturn cross section peak, the silicon range corresponding to the energy upper limit, and the device equivalent silicon layer thickness, obtaining the proton range, energy and LET value reaching the sensitive volume of the device; Step S6, obtaining the proton range, energy and LET value of the proton that is higher than and closest to the energy upper limit and reaches the sensitive volume of the device: Based on the proton energy that is higher than the upper limit of the single-particle upset cross-section peak energy and closest to the upper limit of the energy, the corresponding range in silicon, and the equivalent silicon layer thickness of the device, the proton range, energy and LET value reaching the sensitive volume of the device are calculated; Step S7, obtaining the LET threshold of the single event upset of the device: The LET value of the proton at the energy upper limit in the device sensitive volume obtained in step S5 and the LET value of the proton above and closest to the energy upper limit in the device sensitive volume obtained in step S6 are averaged to obtain the device single event upset LET threshold.

2. The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the device according to claim 1, characterized in that: The step S2 further comprises: In the experiment, based on the calculation results of step S1, the initial energy protons are made to pass through energy-reducing sheets of different thicknesses to reach the device surface, so as to obtain different average proton energies on the device surface. The single particle upset cross sections of the device are measured in order from high to low according to the proton energy. The calculation formula of the single particle upset cross section σ is as follows: Where σ is the single-event upset cross section, N is the number of single-event upsets, F is the incident proton fluence, and M is the device storage capacity.

3. The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the device according to claim 1, characterized in that: The step S4 further comprises: The equivalent silicon layer thickness of the device is: the silicon range corresponding to the lower limit of the low-energy proton single-particle upturn cross-section peak energy, Subtract the thickness of the device sensitive volume.

4. The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the device according to claim 1, characterized in that: The thickness of the sensitive volume of the device is 1 micron.

5. The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the device according to claim 1, characterized in that: The step S5 further comprises: According to the energy upper limit corresponding to the low-energy proton single particle upset cross section peak, based on the calculation result of step S1, the silicon range corresponding to the energy upper limit is obtained; The silicon range corresponding to the energy upper limit is subtracted from the thickness of the device's equivalent silicon layer to obtain the silicon range of the protons reaching the device's sensitive volume; The proton energy and LET values ​​corresponding to the silicon range of protons in the sensitive volume are calculated using the SRIM software.

6. The method for obtaining the equivalent silicon layer thickness and the single event upset LET threshold of the device according to claim 1, characterized in that: The step S6 further comprises: Extract the proton energy that is higher than the upper limit of the single-particle upset cross-section peak energy and closest to the upper limit of the energy, and obtain the silicon range corresponding to the energy based on the calculation result of step S1; The silicon mid-range corresponding to the proton energy that is higher than the single-particle upturn cross-section peak energy upper limit and closest to the energy upper limit is subtracted from the device equivalent silicon layer thickness to obtain the proton silicon mid-range that reaches the device sensitive volume; The proton energy and LET values ​​corresponding to the silicon range of protons in the sensitive volume are calculated using the SRIM software.

Images