JPWO2019038836A1 - Soft error inspection method, soft error inspection device and soft error inspection system - Google Patents

Abstract

The soft error inspection method for a semiconductor device includes a step of irradiating a logic circuit of the semiconductor device with an energy beam and a step of measuring a soft error of the semiconductor device irradiated with the energy beam. The above problem is solved by a soft error inspection method characterized in that the energy beam is intensity-modulated by a signal to which a periodic signal component and a noise component are added.

Description

The present invention relates to a soft error inspection method, a soft error inspection apparatus, and a soft error inspection system.

It is known that semiconductor devices such as LSIs (Large Scale Integration) cause malfunctions due to radiation, so-called soft errors. Such soft errors occur not only in mission-critical equipment such as infrastructure servers and spacons, but also in equipment that requires radiation resistance for space and medical use, FA (Factory Automation) equipment, communication base station equipment, etc. This is a problem for devices that cannot stop time.

In general, soft errors are difficult to inspect because no defects remain. Specifically, soft error inspection methods include running tests at high altitudes and tests using accelerators. The test using an accelerator is further divided into a method of irradiating the entire surface of the LSI chip with neutrons and ions and a method of locally irradiating condensing electrons and lasers. Of these methods, the laser evaluation method is superior in that it can be realized with a small-scale equipment because it does not need to be evacuated, and that a specific memory area can be evaluated individually.

Japanese Unexamined Patent Publication No. 2012-58247 Japanese Unexamined Patent Publication No. 2002-207068 Special Table 2010-534331A Special Table 2016-521352

By the way, soft errors include memory inversion in which information stored in a semiconductor memory is inverted, and malfunction in a logic circuit formed by a semiconductor. Specifically, when radiation is incident on the region where the logic circuit is formed, an electric charge is generated by the radiation, and the electric charge may cause voltage noise in the transistor forming the logic circuit. Since the logic circuit operates based on the input clock signal, if this voltage noise is erroneously recognized as a trigger signal, the erroneous operation propagates, leading to a malfunction. Such a phenomenon in which voltage noise is erroneously recognized as a trigger signal is called a single event transient (SET), and is known as a cause of malfunction of the logic unit due to a transient voltage change.

Therefore, when the semiconductor device is a logic circuit or the like, there is a demand for a soft error inspection method capable of inspecting soft errors by SET.

According to one aspect of the present embodiment, in the soft error inspection method for a semiconductor device, a step of irradiating the logic circuit of the semiconductor device with an energy beam and a soft error of the semiconductor device irradiated with the energy beam. The energy beam is intensity-modulated by a signal to which a periodic signal component and a noise component are added.

According to the disclosed soft error inspection method, it is possible to inspect soft errors by SET in a logic circuit or the like of a semiconductor device.

Explanatory drawing of soft error by SET (1) Explanatory drawing of soft error by SET (2) Structural drawing of the soft error inspection device according to the first embodiment Explanatory drawing of soft error inspection apparatus in 1st Embodiment Explanatory drawing of the signal used for the soft error check in the 1st Embodiment Flowchart of soft error inspection method in the first embodiment Explanatory drawing of soft error inspection apparatus in 2nd Embodiment Explanatory drawing of signals used for soft error inspection (1) Explanatory drawing of signals used for soft error inspection (2) Explanatory drawing of signals used for soft error inspection (3) Explanatory drawing of soft error inspection method in 2nd Embodiment Explanatory drawing of signals used for soft error inspection (4)

The embodiment for carrying out will be described below. The same members and the like are designated by the same reference numerals and the description thereof will be omitted.

[First Embodiment]
First, soft errors will be described. When the high-energy beam enters the inside of the LSI chip, it continues to advance while losing energy, and electron-hole pairs are generated along the track. When these charges move to the electrodes, they may cause voltage noise. Since the logic circuit operates based on the input clock signal, if this voltage noise is erroneously recognized as a trigger signal, a soft error will occur, leading to malfunction. The speed of the LSI chip tends to increase, but when the number of clocks increases and the LSI chip operates at high speed, the probability of erroneously recognizing the trigger signal increases. Therefore, it is presumed that the problem of soft error becomes more prominent as the speed of the LSI chip increases.

The largest cause of memory malfunction in an LSI chip is what is called a single event upset (SEU). SEU is a soft error in a static state where the stored information is inverted. On the other hand, SET is a soft error in a dynamic state of a logic circuit operating by a clock signal. Therefore, the SET soft error check is performed in a different way than the SEU soft error check. Further, since the SET soft error is a soft error in the dynamic state of the logic circuit, it is said that it is more difficult to detect than the SEU soft error.

In the present embodiment, in order to accelerate and evaluate the SET of a logic circuit composed of an internal node of a flip-flop and a clock node in the LSI chip, an energy beam such as an electron beam or a laser is focused to be focused on the LSI chip. Irradiate the local area. In silicon, in the case of electron irradiation, an electric charge is generated by an ionization action, but in the case of laser irradiation, an electric charge is generated by the effect of two-photon absorption. If the electric charge is taken into the transistor, it becomes voltage noise. Therefore, it is considered that the same SET elementary process is performed thereafter regardless of the type of the irradiated energy beam.

Specifically, in the case of a laser, when the LSI chip is irradiated with a laser, electron-hole pairs are generated by an excitation process called two-photon absorption, which absorbs two photons at the same time. If the energy due to photons exceeds the bandgap energy of Si, 1.12 eV, electron-hole pairs are generated by indirect transition. Voltage noise is generated by the electrons and holes generated in this way.

For example, in the case of the logic circuit shown in FIG. 1, it has a combination circuit 110 to which a plurality of logic circuits are connected and a flip-flop 120. In such a logic circuit, as shown in FIG. 2A, the input signal Din input to the flip-flop 120 is taken in at the rising edge of the clock signal CLK. For example, as shown in FIG. 1, when an energy beam is incident on the region 111 of the combinational circuit 110 and voltage noise is generated, the voltage noise propagates in the combinational circuit 110 as shown by the broken line arrow and is an input signal. It is input to the flip-flop 120 as a Din. If the signal due to this voltage noise does not match the rising edge of the clock signal CLK, it will not be captured in the flip-flop 120, so a soft error will not occur and the output signal DQ output from the flip-flop 120 will be normal. There is up to.

However, as shown in FIG. 2B, when the signal due to the generated voltage noise in the input signal Din coincides with the rising edge of the clock signal CLK, the signal due to the voltage noise is regarded as an erroneous trigger signal and the flip-flop 120 Will be taken in. In this case, the output signal DQ output from the flip-flop 120 is inverted, resulting in a soft error and an erroneous operation. Since such a SET soft error occurs in a state where the flip-flop is operating, it is difficult to inspect it.

By the way, a soft error due to SET is generated by natural radiation, which is an energy beam emitted in a natural environment. It is known that such natural radiation has uneven energy and intensity, and fluctuations exist. Therefore, if the LSI chip is irradiated with a laser with a single intensity or the like, it is not possible to accurately inspect soft errors by SET. For this reason, it is important to perform an inspection by irradiating a laser that simulates natural radiation in order to perform an accurate inspection.

Here, when the inventor examined natural radiation, he found that natural radiation has a component whose intensity fluctuates periodically and a component whose intensity fluctuates randomly such as noise. It was. In the present embodiment, the LSI chip is irradiated with a laser having a signal intensity distribution obtained by adding a signal component whose intensity fluctuates periodically and a noise component whose intensity fluctuates randomly, and a soft error is inspected by SET. Is to do. As a result, the soft error can be inspected by SET in a state close to the actual environment, so that the soft error can be inspected accurately. As the noise component, a high frequency having a frequency 10 times or more higher than the frequency of the signal component may be used instead of the white noise. This is because when the frequency is sufficiently high with respect to the signal component, it can be considered as being close to the noise component with respect to the signal component. In this case, the signal component may be described as the first frequency component, and the high frequency component that approximates the noise component may be described as the second frequency component.

(Soft error inspection device and soft error inspection system)
Next, the soft error inspection device according to the first embodiment will be described. FIG. 3 shows a soft error inspection device and a soft error inspection system according to the present embodiment. The soft error inspection device according to the present embodiment includes a scanning stage 20, a scanning control unit 21, an irradiation source 30, an irradiation control unit 31, a measuring device 40, a control unit 50, and the like. The control unit 50 has an information processing unit 51, a storage unit 52, and the like, and the display unit 53 and the input unit 54 are connected to each other.

The semiconductor device 10 which is a sample to be inspected is an LSI chip or the like. The semiconductor device 10 is installed on the scanning stage 20 and can be moved in two dimensions by the scanning stage 20, that is, in the X-axis direction and the Y-axis direction. The scanning stage 20 is controlled by the scanning control unit 21.

The irradiation source 30 emits a laser, which is an energy beam irradiated to the semiconductor device 10, and is controlled by the irradiation control unit 31. In the present embodiment, the case where the laser is emitted from the irradiation source 30 will be described, but charged particles such as electron beams may be emitted. When the semiconductor device 10 is a semiconductor device formed of silicon, since the wavelength region in which two-photon absorption occurs in silicon is 1100 nm to 2100 nm, a laser having a wavelength in this range is irradiated. For example, the wavelength of the laser emitted from the irradiation source 30 is about 1500 nm.

The measuring instrument 40 is a tester or the like, and is connected to the terminal of the semiconductor device 10, and can measure a change in information due to SET in the semiconductor device 10.

The control unit 50 controls the entire soft error inspection device and performs information processing operations related to the soft error inspection method according to the present embodiment. The information processing unit 51 is connected to a storage unit 52 for storing information, a display unit 53 for displaying necessary information, an input unit 54 for inputting information to the information processing unit 51, and the like. In the present embodiment, the soft error inspection system is capable of executing the soft error inspection method described below under the control of the control unit 50.

In the present embodiment, as shown in FIG. 4, inside the information processing unit 51, a first signal generation unit 61 that generates a signal component and a second signal generation unit 62 that generates a noise component And, a signal control unit 63 or the like that controls these intensities or the like may be provided. In this case, the signal component generated by the first signal generation unit 61 is, as shown in FIG. 5A, a periodic signal that fluctuates with an intensity equal to or lower than the threshold value at which a soft error occurs. It is a sine wave signal having a frequency of 100 MHz. The noise component generated in the second signal generation unit 62 is, for example, random noise, specifically white noise, as shown in FIG. 5B. Since the signal component generated by the first signal generating unit 61 does not exceed the threshold value at which the soft error occurs, the soft error is not added in the state where the noise component generated by the second signal generating unit 62 is not added. Does not occur.

In the present embodiment, a signal including a periodic component and a random component is included by adding a noise component generated by the second signal generation unit 62 to the signal component generated by the first signal generation unit 61. To generate. Based on such a signal, the irradiation control unit 31 generates a state simulating natural radiation by modulating the intensity of the laser emitted from the irradiation source 30. The intensity distribution due to natural radiation is not limited to space and polar regions, but differs depending on the environment in which the LSI chip is used. For this reason, it is possible to generate energy fluctuations similar to the state in which natural radiation is radiated in the environment in which it is used, and to enable an accurate accelerated test of soft errors by SET.

The pattern of natural radiation differs depending on the region and environment in which the electronic device on which the LSI chip is mounted is used. Therefore, the signal component generated by the first signal generation unit 61 and the noise component generated by the second signal generation unit 62 correspond to the area and environment in which the electronic device on which the LSI chip is mounted is used. The intensity of is controlled by the signal control unit 63.

(Soft error inspection method)
Next, the soft error inspection method in the present embodiment will be described with reference to FIG. The semiconductor device 10 which is an LSI chip to be inspected by the soft error inspection method in the present embodiment includes a logic circuit including a flip-flop, a logic circuit, and the like.

First, as shown in step 102 (S102), the semiconductor device 10 as a sample is installed on the scanning stage 20, and the irradiation conditions of the laser corresponding to natural radiation are set. Specifically, a laser irradiation condition corresponding to natural radiation such as the environment in which the semiconductor device 10 to be inspected is used is generated by adding a signal component and a noise component, and this signal is generated as a signal of the laser irradiation condition. Set as.

Next, as shown in step 104 (S104), with the logic circuit of the semiconductor device 10 installed on the scanning stage 20 being operated, the irradiation source is under the laser irradiation conditions set in step 102. The semiconductor device 10 is irradiated with a laser from 30.

Next, as shown in step 106 (S106), the semiconductor device 10 is inspected for soft errors by SET of the semiconductor device 10 installed on the scanning stage 20 while the semiconductor device 10 is irradiated with the laser.

As described above, in the soft error inspection method of the present embodiment, by irradiating the laser under conditions similar to natural radiation, it is possible to accurately perform an accelerated test of soft errors caused by SET caused by natural radiation. .. In the above, the case of a laser has been described as the energy beam generated by the irradiation source 30, but an electron beam or the like may be used.

[Second Embodiment]
Next, a second embodiment will be described. The present embodiment relates to a method of generating a modulated signal from a periodic signal component and a random noise component to generate a signal that is a laser irradiation condition so that a soft error pattern generated by natural radiation can be reproduced. It is a thing. In the present embodiment, as shown in FIG. 7, the information processing unit 51 includes a first signal generation unit 61, a second signal generation unit 62, a signal control unit 63, an output measurement unit 64, and a determination unit. It has 65, a threshold value adjusting unit 66, and the like.

The output measuring unit 64 determines whether or not the intensity distribution of the input laser exceeds the set threshold value. Specifically, in the input laser intensity distribution, when the laser intensity exceeds the threshold value, "1" is output at that timing. This threshold value is set to determine whether or not the strength is such that a soft error due to SET is generated.

In the present embodiment, the storage unit 52 stores the occurrence pattern of soft errors due to natural radiation. The pattern of occurrence of soft errors due to natural radiation can be obtained by measuring the intensity of natural radiation and the frequency of occurrence of soft errors in advance at a specific energy of natural radiation. The determination unit 65 compares the output in the output measurement unit 64 with the soft error occurrence pattern due to natural radiation stored in the storage unit 52, and determines the degree of the difference. When the difference is large, the signal control unit 63 adjusts the intensity of the noise component generated by the second signal generation unit 62 or the signal generated by the first signal generation unit 61 so that the difference becomes small. Adjust the frequency and intensity of the components.

As shown in FIG. 8, in the case of only the signal component generated by the first signal generation unit 61, the signal strength does not exceed the threshold value at which the soft error occurs. Therefore, even if the signal component generated by the first signal generation unit 61 is input to the output measurement unit 64, the output from the output measurement unit 64 is “0”.

On the other hand, if the intensity of the noise component generated in the second signal generation unit 62 added to the signal component generated in the first signal generation unit 61 is too strong, as shown in FIG. 9, almost all the time. The threshold is exceeded on the axis. Therefore, when such a signal is input to the output measuring unit 64, the output from the output measuring unit 64 becomes continuous.

Therefore, as shown in FIG. 10, the intensity of the noise component generated in the second signal generation unit 62 is adjusted so as to have a pattern similar to the soft error generation pattern due to natural radiation.

Next, a soft error inspection method according to the present embodiment will be described with reference to FIG.

First, as shown in step 202 (S202), in natural radiation of a certain energy, a signal for intensifying the intensity of the laser emitted from the irradiation source 30 is set. Specifically, as a signal component generated by the first signal generation unit 61, for example, a signal having a 100 MHz sine wave and a strength lower than the threshold value at which a soft error occurs is set. White noise is set as the noise component generated in the second signal generation unit 62.

Next, as shown in step 204 (S204), the intensity of the noise component generated in the second signal generation unit 62 is increased to a predetermined intensity.

Next, as shown in step 206 (S206), a signal obtained by adding a noise component generated by the second signal generation unit 62 to the signal component generated by the first signal generation unit 61 is added to the output measurement unit 64. Enter in. When the input signal exceeds the threshold value, the output measurement unit 64 outputs a value of "1" at that timing and measures this output.

Next, as shown in step 208 (S208), the determination unit 65 determines whether or not the laser irradiation by the signal input to the output measurement unit 64 simulates natural radiation. Specifically, the determination unit 65 compares the output from the output measurement unit 64 with the soft error occurrence pattern due to natural radiation stored in the storage unit 52, and whether the difference is within a predetermined range. Judge whether or not. When the difference between the output from the output measuring unit 64 and the soft error occurrence pattern due to natural radiation stored in the storage unit 52 is within a predetermined range, the laser based on the signal input to the output measuring unit 64 It is judged that the irradiation of is simulating natural radiation. If it is determined that the signal input to the output measuring unit 64 is for simulating natural radiation, the process proceeds to step 210, and the signal input to the output measuring unit 64 is not for simulating natural radiation. If it is determined, the process proceeds to step 212.

In step 210 (S210), the difference between the output from the output measuring unit 64 and the soft error occurrence pattern due to natural radiation stored in the storage unit 52 is adjusted to be small. Specifically, the intensity of the noise signal generated by the second signal generation unit 62 and the frequency and intensity of the signal component generated by the first signal generation unit 61 are adjusted. After that, the process proceeds to step 206, and these steps are repeated until it is determined that the signal input to the output measuring unit 64 simulates natural radiation.

In step 212 (S212), the energy of the signal component determined by the determination unit 65 that the signal input to the output measurement unit 64 is to simulate natural radiation, the intensity of the noise component, and the like. It is stored in the storage unit 52 as a simulated condition of line-of-sight radiation.

Next, in step 214 (S214), it is determined whether or not a laser simulation is required for natural radiation of another energy. If laser simulation of natural radiation of another energy is required, the process proceeds to step 202, and if natural radiation of another energy does not require laser simulation, the process proceeds to step 216. Examples of cases where it is necessary to simulate natural radiation of another energy by a laser include a case where it is necessary to reproduce the energy distribution of radiation.

Next, as shown in step 216 (S216), the semiconductor device 10 as a sample is placed on the scanning stage 20, selected from the simulated conditions stored in the storage unit 52, and irradiated to the semiconductor device 10. Enter as an irradiation condition.

Next, as shown in step 218 (S218), from the irradiation source 30 according to the irradiation conditions input in step 216 in a state where the logic circuit of the semiconductor device 10 installed on the scanning stage 20 is operated. Irradiate the semiconductor device 10 with a laser.

Next, as shown in step 220 (S220), the semiconductor device 10 is inspected for soft errors by SET of the semiconductor device 10 installed on the scanning stage 20 while the semiconductor device 10 is irradiated with the laser.

From the above, it is possible to obtain a laser irradiation condition simulating natural radiation corresponding to the environment in which the semiconductor device is used, irradiate the laser under this irradiation condition, and inspect the soft error by SET. As a result, it is possible to accurately inspect soft errors by SET in the environment where the semiconductor device is used. In the above, the case of a laser has been described as the energy beam generated by the irradiation source 30, but an electron beam or the like may be used.

Further, in the present embodiment, as shown in FIG. 12, a plurality of threshold values may be provided. Specifically, for example, the threshold values are set to th1, th2, th3, and th4 in ascending order of intensity. If the threshold value is th1 or more and does not exceed the threshold value th2, the output is "1". If the threshold value is th2 or more and does not exceed the threshold value th3, the output is "2". If the above value does not exceed the threshold value th4, the output is set to "3". By setting a plurality of threshold values in this way, the intensity distribution of natural radiation can be reproduced in detail.

Further, in the present embodiment, in step 210, instead of adjusting the output of the noise signal generated by the second signal generating unit 62, the threshold value adjusting unit 66 adjusts the value that becomes the threshold value. It may be a thing. Specifically, when the difference between the output from the output measuring unit 64 and the soft error occurrence pattern due to natural radiation stored in the storage unit 52 is large, the threshold value is set so that the difference becomes small. A value serving as a threshold value may be adjusted in the adjusting unit 66. Further, instead of the noise component, a high frequency having a frequency 10 times or more the signal component may be generated and used in the second signal generation unit 62.

The contents other than the above are the same as those in the first embodiment.

Although the embodiments have been described in detail above, the embodiments are not limited to the specific embodiments, and various modifications and changes can be made within the scope of the claims.

10 Semiconductor device 20 Scanning stage 30 Irradiation source 21 Scanning control unit 31 Irradiation control unit 40 Measuring instrument 51 Information processing unit 52 Storage unit 53 Display unit 54 Input unit 61 First signal generation unit 62 Second signal generation unit 63 Signal control Unit 64 Output measurement unit 65 Judgment unit 66 Threshold adjustment unit

Claims (10)

In the soft error inspection method for semiconductor devices
The process of irradiating the logic circuit of the semiconductor device with an energy beam,
The process of measuring the soft error of the semiconductor device irradiated with the energy beam, and
Have,
A soft error inspection method, characterized in that the energy beam is intensity-modulated by a signal to which a periodic signal component and a noise component are added. In the soft error inspection method for semiconductor devices
The process of irradiating the logic circuit of the semiconductor device with an energy beam,
The process of measuring the soft error of the semiconductor device irradiated with the energy beam, and
Have,
The energy beam is intensity-modulated by a signal obtained by adding a periodic first frequency component and a second frequency component having a frequency 10 times or more the frequency of the first frequency component. A characteristic soft error inspection method. The soft error inspection method according to claim 1 or 2, wherein the energy beam is a laser. The soft error measurement according to any one of claims 1 to 3, wherein the measurement of the soft error by SET of the semiconductor device is performed in a state where the logic circuit of the semiconductor device is operated. Soft error inspection method. The soft error inspection method according to any one of claims 1 to 4, wherein the intensity modulation of the energy beam corresponds to natural radiation. An irradiation source that emits an energy beam that irradiates a semiconductor device,
A measuring instrument that is connected to the semiconductor device and is irradiated with the energy beam to measure a soft error due to SET of the semiconductor device.
Have,
The energy beam is a soft error inspection apparatus characterized in that the energy beam is intensity-modulated by a signal obtained by adding a noise component to a periodic signal component. A first signal generator that generates the signal component,
A second signal generator that generates the noise component,
Have,
The frequency of the signal component generated in the first signal generation unit or the intensity of the noise component generated in the second signal generation unit is adjusted so that the intensity modulation of the energy beam corresponds to natural radiation. The soft error inspection device according to claim 6, wherein the soft error inspection device is characterized. An irradiation source that emits an energy beam that irradiates a semiconductor device,
A measuring instrument that is connected to the semiconductor device and is irradiated with the energy beam to measure a soft error due to SET of the semiconductor device.
Have,
The energy beam is intensity-modulated by a signal obtained by adding a periodic first frequency component and a second frequency component having a frequency 10 times or more the frequency of the first frequency component. A featured soft error inspection device. A first signal generator that generates the first frequency component,
A second signal generator that generates the second frequency component,
Have,
The intensity of the first frequency component generated in the first signal generation unit or the second frequency generated in the second signal generation unit so that the intensity modulation of the energy beam corresponds to natural radiation. The soft error inspection apparatus according to claim 8, wherein the strength of the component is adjusted. A soft error inspection system including the soft error inspection apparatus according to any one of claims 6 to 9, wherein the control is performed by a control unit.

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