SEB measuring device and SEB measuring method

Abstract

The present invention comprises a plurality of voltage generation circuits (1, 2, 3) which are provided in an environment to be irradiated with neutron rays and which are connected in parallel. Each of the voltage generation circuits comprises: a first circuit in which a MOSFET (21, 22, 23) and a diode (D1, D2, D3) are connected in series; and a second circuit which is connected to both ends of the MOSFET and in which a DC limiting capacitor (C1, C2, C3) and a voltage measurement resistor are connected in series. One end of the first circuit is supplied with a predetermined voltage, and the other end thereof is grounded. The present invention comprises: a measurement unit 12 for measuring voltages generated in the voltage measurement resistors; and a calculation unit 13 for calculating an SEB generation rate on the basis of the measured voltages.

Description

[Technical Field]

[0001] The present invention relates to an SEB measurement device and an SEB measurement method. [Background technology]

[0002] When high-energy particles (mainly protons) contained in cosmic radiation collide with oxygen or nitrogen atomic nuclei in the Earth's atmosphere, neutron rays are generated and rain down on the ground. Neutron rays cause malfunctions (soft errors) in electronic devices on the ground. Neutron rays are known to cause SEB (Single Event Burnout), which burns out circuit elements such as MOSFETs (Field Effect Transistors) and diodes. In order to suppress SEB in electronic devices, it is necessary to measure the SEB generation rate of the circuit elements that make up the electronic devices.

[0003] Patent Document 1 discloses a method for measuring the SEB generation rate by preparing a measurement circuit in which multiple sets of series connections of diodes (semiconductor elements) and fuses are connected in parallel, and installing this measurement circuit in a neutron irradiation chamber. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Asai, Sugimoto, Nashiyama, Iide, Shiba,Matsuda, Miyazaki, “Terrestrial neutron-induced single-event burnoutin SiC power diodes”, 2011 12th European Conference on Radiation and Its Effectson Components and Systems. Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, when a diode is destroyed due to the occurrence of SEB, a reverse current flows through the destroyed diode, causing the fuse connected in series to melt. The incidence of SEB can be measured based on the number of blown fuses.

[0006] Furthermore, since the circuit is interrupted when the fuse blows, no current flows through the destroyed diode after the fuse blows. Therefore, the SEB occurrence rate can be measured using the remaining normal diodes. However, fuses do not blow instantly when an overcurrent flows, but rather take a certain amount of time to blow. Therefore, it may not be possible to measure the occurrence of SEB during the time it takes for the fuse to blow, which can lead to a large statistical error.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide an SEB measuring device and an SEB measuring method that are capable of measuring the SEB incidence rate with high accuracy. [Means for solving the problem]

[0008] An SEB measurement device according to one embodiment of the present invention is installed in an environment where neutron rays are irradiated, and includes a plurality of voltage generation circuits connected in parallel to each other, each voltage generation circuit including a first circuit in which a semiconductor element and a current suppression element are connected in series, and a second circuit connected across the semiconductor element and in which a DC limiting capacitor and a voltage measurement resistor are connected in series, one end of the first circuit is supplied with a predetermined voltage and the other end is grounded, and the device further includes a measurement unit that measures the voltage generated in the voltage measurement resistor, and a calculation unit that calculates the SEB occurrence rate based on the measured voltage.

[0009] An SEB measurement method according to one aspect of the present invention includes a plurality of voltage generation circuits, each of which is installed in an environment where neutron rays are irradiated, and which includes a first circuit in which a semiconductor element and a current suppression element are connected in series, and a second circuit connected across the semiconductor element and in which a DC limiting capacitor and a voltage measurement resistor are connected in series. The method includes the steps of: supplying a predetermined voltage to the semiconductor element; measuring the voltage generated in the voltage measurement resistor; and calculating an SEB occurrence rate based on the voltage generated in the voltage measurement resistor. [Effects of the Invention]

[0010] According to the present invention, it is possible to measure the incidence of SEB with high accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a circuit diagram showing the configuration of an SEB measuring device according to an embodiment. [Figure 2] FIG. 2 is a circuit diagram showing the configuration of the SEB measuring device according to the first modification. [Figure 3] FIG. 3 is a circuit diagram showing the configuration of an SEB measuring device according to a second modification. [Figure 4] FIG. 4 is an explanatory diagram showing the experimental results when a neutron irradiation experiment was carried out. [Figure 5] FIG. 5 is a block diagram showing the hardware configuration of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Description of the embodiment] An embodiment will be described below. Fig. 1 is a circuit diagram showing the configuration of an SEB measuring device according to an embodiment. As shown in Fig. 1, an SEB measuring device 100 according to an embodiment includes a plurality of (three in the figure) voltage generating circuits 1, 2, and 3, a power supply 11, a measuring unit 12, and a calculating unit 13.

[0013] The voltage generating circuit 1 has a series-connected circuit (first circuit) of an N-type MOSFET 21 (field-effect transistor) and a current blocking diode D1 (hereinafter abbreviated as "diode D1"). The MOSFET 21 is an example of a semiconductor element. The diode D1 is an example of a current blocking element.

[0014] The drain d1 of the MOSFET 21 is connected to a voltage supply terminal T1 (details will be described later). The gate g1 and source s1 of the MOSFET 21 are connected to the cathode of a diode D1. The anode of the diode D1 is grounded. That is, a predetermined voltage is supplied to one end of a first circuit in which a semiconductor element (MOSFET 21) and a diode D1 are connected in series via the voltage supply terminal T1, and the other end is grounded.

[0015] The predetermined voltage may be, for example, the maximum voltage (rated voltage) at which the MOSFET 21 can be safely used. The diode D1 is an example of a current blocking element that blocks current flowing from the MOSFET 21 to the ground.

[0016] The voltage generating circuit 1 has a series-connected circuit (second circuit) of a DC limiting capacitor C1 (hereinafter abbreviated as "capacitor C1") and a voltage measuring resistor formed by connecting a first resistor R11 and a second resistor R12 in series. One end of the capacitor C1 is connected to the drain d1 of the MOSFET 21, and one end of the second resistor R12 is connected to the source s1 of the MOSFET 21.

[0017] That is, a series connection circuit (second circuit) of the capacitor C1 and voltage measurement resistors (R11, R12) is connected to both ends of a semiconductor element (MOSFET 21). A connection terminal T11 of the first resistor R11 and the second resistor R12 is connected to the measurement unit 12. A voltage supply terminal T1 is connected to the power supply 11.

[0018] The voltage generation circuits 2 and 3 have the same configuration as the voltage generation circuit 1. That is, the voltage generation circuit 2 includes an N-type MOSFET 22 having a drain d2, a source s2, and a gate g2, a diode D2, a DC limiting capacitor C2, a first resistor R21, a second resistor R22, and a connection terminal T12. The voltage generation circuit 3 includes an N-type MOSFET 23 having a drain d3, a source s3, and a gate g3, a diode D3, a DC limiting capacitor C3, a first resistor R31, a second resistor R32, and a connection terminal T13. The connection terminals T12 and T13 are connected to the measurement unit 12.

[0019] The multiple voltage generation circuits 1, 2, and 3 are connected in parallel to one another. Each of the voltage generation circuits 1, 2, and 3 is provided in a neutron irradiation chamber 31. The neutron irradiation chamber 31 is a space capable of actively generating neutron beams, and neutron beams can be irradiated onto the MOSFETs 21, 22, and 23 provided in each of the voltage generation circuits 1, 2, and 3. In other words, the voltage generation circuits 1, 2, and 3 are provided in an environment where they are irradiated with neutron beams. Note that, although an example in which N-type MOSFETs 21, 22, and 23 are used as field effect transistors will be described in this embodiment, P-type MOSFETs may also be used.

[0020] The diodes D1, D2, and D3 have a reverse bias rated voltage set so that they will not be destroyed even when irradiated with neutron rays.

[0021] The power supply 11 generates a DC voltage. The power supply 11 supplies the rated voltage of each of the MOSFETs 21, 22, and 23 to the voltage supply terminal T1. Therefore, for example, when SEB occurs at the gate g1 of the MOSFET 21 and a voltage is generated between the gate g1 and the source s1, conduction occurs between the drain d1 and the source s1. The same applies to the MOSFETs 22 and 23.

[0022] The measuring unit 12 measures the voltages generated at the connection terminals T11, T12, and T13. That is, the measuring unit 12 measures the voltage generated across the voltage measurement resistor. In a steady state where no SEB occurs in the MOSFET 21, no current flows in the second circuit (the series-connected circuit of C1, R11, and R12), so the voltage at the connection terminal T11 is zero (the potential is at the ground level). When an SEB occurs in the MOSFET 21 and the drain d1 to source s1 of the MOSFET 21 become conductive, a current flows in the second circuit (details will be described later), and a voltage generated across the second resistor R12 is generated at the connection terminal T11. The same applies to the MOSFETs 22 and 23.

[0023] The measuring unit 12 can detect whether or not SEB has occurred in each of the voltage generating circuits 1, 2, and 3 by monitoring the voltages at the connection terminals T11, T12, and T13.

[0024] The calculation unit 13 calculates the rate of occurrence of SEB occurring in the semiconductor elements (MOSFETs 21, 22, 23) based on the voltages of the connection terminals T11, T12, and T13 measured by the measurement unit 12.

[0025] Next, the operation of the SEB measurement device 100 according to this embodiment will be described. As shown in Fig. 1, the voltage generation circuits 1, 2, and 3 are installed in a neutron irradiation chamber 31. In this state, a predetermined voltage (for example, a rated voltage) is supplied to the voltage supply terminal T1 by the power supply 11. Since the MOSFET 21 is in a non-conductive state, no current flows through the first circuit including the MOSFET 21 and the diode D1. The same applies to the MOSFETs 22 and 23.

[0026] That is, as indicated by the solid arrow L1 in FIG. 1, the rated voltage is supplied to the drains d1, d2, and d3 of the MOSFETs 21, 22, and 23, but since the MOSFETs 21, 22, and 23 are turned off, no current flows through the first circuit.

[0027] Furthermore, a current flows transiently through the second circuit including the capacitor C1, the first resistor R11, and the second resistor R12 for a period until the capacitor C1 is charged, and then the current is cut off. The same applies to the MOSFETs 22 and 23.

[0028] In this state, the voltages at the connection terminals T11, T12, and T13 are zero. If an SEB occurs in the MOSFET 22 due to neutron irradiation, for example, conduction occurs between the drain d2 and the source s2 of the MOSFET 22, causing an overcurrent to flow. As a result, the MOSFET 22 is destroyed.

[0029] As a result, the charge stored in capacitor C2 is discharged via drain d2 to source s2 of MOSFET 22. That is, current flows along the path from the positive pole of capacitor C1 → MOSFET 22 → second resistor R22 → first resistor R21 → negative pole of capacitor C1. As a result, a voltage obtained by dividing the charging voltage of capacitor C2 by the first resistor R21 and the second resistor R22 is generated at connection terminal T12. The generated voltage is measured by measuring unit 12, and it is detected that SEB has occurred in MOSFET 22.

[0030] The calculation unit 13 calculates the incidence of SEB based on the SEB detected by the measurement unit 12.

[0031] Furthermore, in the MOSFET 22 in which an SEB has occurred, conduction continues between the drain d2 and the source s2. However, because a diode D2, which is a current blocking element, is provided between the MOSFET 22 and ground, the voltage supply terminal T1 is not connected to ground. That is, as indicated by the dashed arrow L2 in FIG. 1, although the rated voltage is supplied to the source s2 of the MOSFET 22, the presence of the diode D2 prevents current from flowing through the first circuit including the MOSFET 22 and the diode D2. Therefore, SEB measurement can be continued for the MOSFETs 21 and 23 in which no SEB has occurred. This makes it possible to measure the SEB occurrence rate over a long period of time without requiring work such as fuse replacement.

[0032] 4 is an explanatory diagram showing the neutron beam (amount of charged particles) irradiated until SEB occurred when four MOSFETs (No. 1 to No. 4) were installed in the neutron irradiation chamber 31 and a neutron irradiation experiment was conducted. From FIG. 4, it can be seen that the occurrence of SEB and the irradiated neutron beam could be measured in all four MOSFETs (No. 1 to No. 4).

[0033] As described above, the SEB measuring device 100 according to this embodiment is installed in an environment where it is irradiated with neutron rays, and includes a plurality of voltage generating circuits 1, 2, and 3 connected in parallel to one another. Each of the voltage generating circuits 1, 2, and 3 includes a first circuit in which a semiconductor element (e.g., MOSFETs 21, 22, and 23) and a current suppressing element (e.g., diodes D1, D2, and D3) are connected in series, and a second circuit connected across the semiconductor element and in which a DC limiting capacitor (C1, C2, and C3) and a voltage measuring resistor are connected in series. One end of the first circuit is supplied with a predetermined voltage, and the other end is grounded. The first circuit further includes a measuring unit 12 that measures the voltage generated in the voltage measuring resistor, and a calculating unit 13 that calculates the SEB occurrence rate based on the measured voltage.

[0034] According to this embodiment, current suppression elements such as diodes D1, D2, and D3 are provided between semiconductor elements such as MOSFETs 21, 22, and 23 and the ground, so that even if the semiconductor elements become conductive due to the occurrence of SEB, the power supply voltage can be prevented from being connected to the ground.

[0035] Therefore, even if SEB occurs in one semiconductor element, it is possible to continue measuring the SEB occurrence rate using other semiconductor elements.

[0036] That is, to measure the SEB occurrence rate of a MOSFET, it is necessary to measure many SEBs and perform statistical calculations. If a diode is not installed between the MOSFET and ground, an overcurrent will flow through the MOSFET every time an SEB occurs, destroying it, and the MOSFET will need to be replaced with a new one every time destruction occurs. Furthermore, because radiation remains in the neutron irradiation chamber 31, replacement of the MOSFET must wait until the radiation subsides. In this embodiment, by installing a current suppression element such as a diode, the MOSFET in which an SEB occurs will not be destroyed, and SEB measurement can continue.

[0037] Furthermore, the voltage generating circuits 1, 2, and 3 do not use fuses that require a certain amount of time to blow after an overcurrent flows, thereby avoiding the problem of large statistical errors. Semiconductor elements such as MOSFETs 21, 22, and 23 are less expensive than high-speed fuses that have a short blow time, so costs can be reduced.

[0038] The second circuit is provided with a series-connected circuit of a first resistor and a second resistor, and the measuring unit 12 measures the voltage at connection terminals T11, T12, and T13, which are the connection points between the first resistor and the second resistor. Therefore, even if the voltage value generated in the second circuit is high, it is possible to extract and measure the voltage divided by the first resistor and the second resistor.

[0039] Since the MOSFETs 21, 22, and 23 are used as semiconductor elements, conduction can be established between the drain and source when an SEB occurs, making it possible to quickly detect the occurrence of an SEB.

[0040] [Explanation of the first modified example] Next, a first modified example of the above-described embodiment will be described. Fig. 2 is a circuit diagram showing the configuration of an SEB measuring device 101 according to the first modified example. As shown in Fig. 2, the SEB measuring device 101 according to the first modified example includes a plurality of voltage generating circuits 1, 2, and 3, a power supply 11, a measuring unit 12, and a calculating unit 13, similar to the above-described Fig. 1.

[0041] The first modification differs in that capacitors C11, C12, and C13 (current inhibition capacitors, current inhibition elements) are provided instead of the diodes D1, D2, and D3 shown in Fig. 1 as current inhibition elements. By providing capacitors C11, C12, and C13, when the MOSFETs 21, 22, and 23 become conductive due to the occurrence of an SEB, the MOSFETs 21, 22, and 23 are disconnected from the ground. Therefore, even if an SEB occurs in one MOSFET (semiconductor element), the measurement of the SEB occurrence rate can be continued using the other MOSFETs.

[0042] [Explanation of the second modified example] Next, a second modified example will be described. Fig. 3 is a circuit diagram showing the configuration of an SEB measuring device 102 according to the second modified example. As shown in Fig. 3, the SEB measuring device 102 according to the second modified example includes a plurality of voltage generating circuits 1, 2, and 3, a power supply 11, a measuring unit 12, and a calculating unit 13, similar to the above-mentioned Fig. 1.

[0043] The second modification differs in that SEB detection diodes D11, D12, and D13 are provided as semiconductor elements instead of the MOSFETs 21, 22, and 23 shown in Fig. 1. That is, the cathodes of the SEB detection diodes D11, D12, and D13 are connected to the voltage supply terminal T1, and the anodes are connected to the cathodes of the diodes D1, D2, and D3.

[0044] Furthermore, the reverse bias rated voltage of each of the SEB detection diodes D11, D12, and D13 is set so that an SEB occurs when neutrons are irradiated. That is, in each of the SEB detection diodes D11, D12, and D13, a reverse current flows from the cathode to the anode when an SEB occurs.

[0045] In the second modification, even if a reverse current flows through the SEB detection diodes D11, D12, and D13 due to the occurrence of an SEB, the diodes D1, D2, and D3 provided as current suppression elements can prevent the voltage supply terminal T1 from being connected to ground. Therefore, it is possible to avoid the SEB detection diodes D11, D12, and D13 from being destroyed, and even if an SEB occurs in one SEB detection diode (semiconductor element), it is possible to continue measuring the SEB occurrence rate using the other SEB detection diodes.

[0046] The measurement unit 12 and calculation unit 13 of the embodiment described above can be implemented, for example, by a general-purpose computer system including a CPU (Central Processing Unit, processor) 901, a memory 902, a storage 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), a communication device 904, an input device 905, and an output device 906, as shown in Fig. 5. The memory 902 and storage 903 are storage devices. In this computer system, the CPU 901 executes a predetermined program loaded onto the memory 902, thereby realizing the functions of the measurement unit 12 and the calculation unit 13.

[0047] The measurement unit 12 and the calculation unit 13 may be implemented in one computer or in multiple computers. Furthermore, the measurement unit 12 and the calculation unit 13 may be virtual machines implemented in a computer.

[0048] The programs for the measurement unit 12 and the calculation unit 13 can be stored on a computer-readable recording medium such as an HDD, SSD, USB (Universal Serial Bus) memory, CD (Compact Disc), or DVD (Digital Versatile Disc), or can be distributed via a network.

[0049] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention. [Explanation of symbols]

[0050] 1, 2, 3 Voltage generation circuit 11 Power supply 12 Measuring part 13 Arithmetic section 21, 22, 23 MOSFET (field effect transistor, semiconductor element) 31 Neutron irradiation room 100, 101, 102 SEB measuring device C1, C2, C3 DC limiting capacitors C11, C12, C13 Capacitors (current blocking capacitors, current blocking elements) D1, D2, D3 Diodes (current blocking diodes, current blocking elements) D11, D12, D13 SEB detection diode (semiconductor element) R11, R21, R31 First resistor (voltage measurement resistor) R21, R22, R23 Second resistor (voltage measurement resistor) T1 Voltage supply terminal T11, T12, T13 connection terminals

Claims

1. The device is installed in an environment where it is irradiated with neutron rays and includes a plurality of voltage generating circuits connected in parallel with each other, Each voltage generating circuit is a first circuit in which a semiconductor element and a current suppressing element are connected in series; a second circuit connected to both ends of the semiconductor element and including a DC limiting capacitor and a voltage measuring resistor connected in series; a predetermined voltage is supplied to one end of the first circuit, and the other end is grounded; Furthermore, a measurement unit that measures a voltage generated across the voltage measurement resistor; a calculation unit that calculates an SEB occurrence rate based on the measured voltage; and An SEB measurement device equipped with:

2. The semiconductor element is a field effect transistor or an SEB detection diode. The SEB measurement device according to claim 1 .

3. The SEB detection diode has a reverse bias rated voltage set so that an SEB occurs when neutron rays are irradiated. The SEB measurement device according to claim 2 .

4. 4. The SEB measuring device according to claim 1, wherein the current blocking element is a current blocking diode or a current blocking capacitor.

5. The current suppression diode has a reverse bias rated voltage set so that SEB does not occur when neutron rays are irradiated. The SEB measurement device according to claim 4.

6. The voltage measurement resistor is formed by connecting a first resistor and a second resistor in series, and the measurement unit measures the voltage generated in the first resistor or the second resistor. The SEB measurement device according to claim 1 .

7. a step of supplying a predetermined voltage to a semiconductor element of a plurality of voltage generating circuits, the voltage generating circuits being installed in an environment where neutron rays are irradiated and including a first circuit in which a semiconductor element and a current suppressing element are connected in series, and a second circuit connected to both ends of the semiconductor element and in which a DC limiting capacitor and a voltage measuring resistor are connected in series; measuring a voltage generated across the voltage measuring resistor; calculating an SEB occurrence rate based on the voltage generated across the voltage measuring resistor; The SEB measurement method includes:

Images