CN116148912A - A Radiation Dose Measurement Method Based on Floating Gate Structure Semiconductor Transistor - Google Patents

Abstract

The invention provides a radiation dose measuring method based on a semiconductor transistor with a floating gate structure, which mainly solves the technical problem that the radiation dose of the semiconductor transistor with the floating gate structure cannot be accurately measured in the prior art. According to the method, the transistor to be measured is subjected to measurement after charging, the method for measuring after irradiation is used for obtaining the difference value between the threshold voltage of the transistor to be measured after irradiation and the threshold voltage of the transistor to be measured before irradiation based on a constant current method, the difference value of the threshold voltage under different radiation doses is obtained according to the method, and finally the change curve of the difference value of the threshold voltage of the transistor to be measured along with the accumulation of the radiation doses is obtained through calculation. The floating gate device is programmed and erased for multiple times, so that the measuring range of radiation dose is greatly improved, and the radiation process is precisely controlled.

Description

A Radiation Dose Measurement Method Based on Floating Gate Structure Semiconductor Transistor

technical field

The invention relates to a radiation dose measurement method in the aerospace application field, in particular to a radiation dose measurement method based on a semiconductor transistor with a floating gate structure.

Background technique

The concept of the floating gate was first mentioned by D.Kahng and S.M.Sze in 1967, and it was applied to the non-volatile memory device of the MIMIS structure. The floating gate is to add a layer of Poly-Si layer in the MOS structure, and the Poly-Si layer can capture Electrons, thereby affecting performance parameters such as the threshold voltage of the device, based on this structure, many floating gate structures suitable for detectors have been developed. When the floating gate structure is applied to the memory, the device is mainly divided into two states, namely the programmed state (Programmed) and the erased state (Erased), and the determination of the state is determined by the magnitude of the current under its operating voltage. However, when the floating gate structure is applied to a radiation dosimeter (ie, a detector), the above two states are no longer considered.

Previous research has been on space radiation dosimeters using MOS devices with P-type thick gate oxide structures as radiation-sensitive probes, and little research has been done on radiation detection technology based on floating gate structure devices as radiation-sensitive probes. However, a MOS semiconductor device with a P-type thick gate oxide structure is used as a radiation-sensitive probe, and the application environment of this type of radiation dosimeter is limited due to mutual constraints between the measurement range and the response sensitivity.

With the rapid development of semiconductor technology, it is found that the radiation dose online monitoring system based on floating gate transistors has better radiation response linearity, can greatly increase the range of radiation dose, and then realize accurate monitoring, and the above The conclusion is crucial to the development of a new generation of total dose detectors. However, because there is no accurate measurement method for the radiation dose of the floating gate transistor at present, it is impossible to effectively evaluate the performance of the radiation dosimeter applied thereto.

Contents of the invention

The object of the present invention is to provide a radiation dose measurement method based on a semiconductor transistor with a floating gate structure, so as to solve the technical problem that the radiation dose of the semiconductor transistor with a floating gate structure cannot be accurately measured in the prior art.

To achieve the above object, the technical scheme of the present invention is as follows:

A radiation dose measurement method based on a semiconductor transistor with a floating gate structure, which is special in that it includes the following steps:

Step 1, charging the transistor to be tested to make it in a programming state, and using a semiconductor parameter testing device to measure and obtain a first characteristic curve; the transistor to be tested is a semiconductor transistor with a floating gate structure; the first characteristic curve refers to the initial Id-Vgs transfer characteristic curve of the transistor under test before irradiation;

Step 2, selecting a current value Id from the first characteristic curve described in step 1, and then obtaining _{the corresponding gate voltage V T} of the transistor to be tested under this current value;

Step 3, short-circuit all the pins of the transistor to be tested in the programming state in step 1, place it in the radiation field for the first irradiation, take it out, and use the semiconductor parameter testing device to measure to obtain the second characteristic curve; The second characteristic curve refers to the Id-Vgs transfer characteristic curve of the transistor to be measured after irradiation;

Step 4, selecting the same current value Id as in step 2 from the second characteristic curve described in step 3, and then obtaining the gate voltage V _T corresponding to the current value of the transistor to be tested after being irradiated;

Step 5, combining the gate voltage V _{T initial} of step 2 and the gate voltage V _T of step 4 to obtain the difference ΔV _T1 of the gate voltage of the transistor to be tested, wherein, ΔV _T1 = V _{T initial} - V _{T post} ; The difference ΔV _T1 of the gate voltage is the difference of the threshold voltage of the transistor to be tested after the first irradiation, and this difference is used as a physical parameter characterizing the radiation dose of the transistor to be tested;

Step 6: Perform an erase operation on the transistor to be tested to remove the charge in the transistor to be tested, and repeat the radiation measurement N times according to the method from step 1 to step 5, and obtain the difference of the threshold voltage of the transistor to be tested after irradiation ΔV _T2 , ΔV _T3 ... ΔV _TN , where N≥5;

Step 7: Calculate the cumulative radiation dose after each irradiation and the threshold voltage difference ΔV _T1 , ΔV _T2 , ΔV _T3 ... ΔV _TN after each irradiation according to the number of times the transistor to be tested is irradiated. The variation curve of the difference value of the threshold voltage of the transistor to be tested and the radiation dose accumulation value is obtained, and then the radiation dose measurement of the semiconductor transistor with a floating gate structure is completed.

Further, in step 1, the charging operation is to connect the source and gate of the transistor to be tested with an external voltage, and ground the source and substrate of the transistor to be tested, so that the transistor to be tested is charged, and wait for 0.1s~ After 10s, the external voltage is removed, and the charging operation is completed.

Further, the applied voltage is 5-10V.

Further, in step 2, the current value Id ranges from 1 to 10 μA.

Further, in step 3, the radiation field is ^{a 60} Co-γ-ray radiation field or an X-ray radiation field.

Further, in step 3, the radiation dose of the radiation field D=5krad(Si).

Further, in step 6, the erasing operation is to apply a low voltage to the gate of the transistor to be tested, and ground the source, drain and substrate, so that the charge in the transistor to be tested is 0, and the low voltage It is -5 ~ -10V.

Further, in step 6, the value of N is 10.

Compared with the prior art, the present invention has the following beneficial effects:

1. The radiation dose measurement method of the present invention is based on the fact that the loss of charge on the semiconductor transistor with a floating gate structure will cause the characteristic parameters of the device to change, and the variation of the characteristic parameters will form a corresponding relationship with the radiation dose. The method of measuring after charging and measuring after irradiation is based on the constant current method to obtain the difference between the threshold voltage of the transistor to be tested after irradiation and before irradiation, and according to this method to obtain the difference of threshold voltage under different radiation doses, and finally calculate The change curve of the threshold voltage difference of the transistor under test with the radiation dose accumulation. The invention performs multiple programming and erasing on the floating gate device, thereby greatly improving the measurement range of the radiation dose, and further precisely controlling the radiation process.

2. In the radiation dose measurement method of the present invention, no power is applied when the transistor to be tested is irradiated, so the power consumption is low and the test cost is low.

3. The radiation dose measurement method of the present invention is based on the detection technology of the radiation dosimeter with strong applicability and easy implementation, so as to obtain the radiation dose test information of the semiconductor transistor with floating gate structure. The method is theoretical guidance for developing domestic floating gate dosimeter, The establishment of methods and techniques is of positive significance.

Description of drawings

FIG. 1 is a curve showing the variation of the threshold voltage difference of a semiconductor transistor based on a floating gate structure with the cumulative dose of radiation in an embodiment of the present invention.

Detailed ways

The design principle of the present invention is: when the floating gate structure is applied to the radiation dosimeter, the floating gate is in a pre-charged state, and the charge control in the initial floating gate adopts methods such as FN tunneling or hot carrier injection, which are Under the influence of radiation, the charge stored on the floating gate is lost, resulting in a change in the characteristic parameters of the device, and the variation of the characteristic parameters will form a corresponding relationship with the radiation dose, thereby realizing the measurement of the radiation dose. The invention measures the semiconductor transistor with a floating gate structure, the transistor is a semiconductor device based on a standard process line, easy to read circuit integration, and the semiconductor transistor with a floating gate structure can be programmed and erased many times, thereby greatly improving Radiation dose measurement range, wider use environment.

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The invention provides a radiation dose measurement method based on a floating gate structure semiconductor transistor, which specifically includes the following steps:

Step 1, charge the transistor to be tested to make it in the programming state, and use the semiconductor parameter testing device to measure the first characteristic curve; the transistor to be tested is a semiconductor transistor with a floating gate structure; the first characteristic curve refers to the The initial Id-Vgs transfer characteristic curve of the transistor before irradiation.

In this embodiment, the charging operation is to connect the source and gate of the transistor to be tested to an external voltage, and the external voltage is generally 5-10V. Ground the source and substrate of the transistor to be tested so that the transistor to be tested is charged. When the transistor to be tested accumulates enough electrons, the external voltage is removed. Generally, the charging operation is completed after the external voltage is removed after 0.1s to 10s.

Step 2. Select a current value Id from the first characteristic curve in step 1. The current value Id ranges from 1 to 10 μA. Any current value can also be selected according to the Id-Vgs transfer characteristic curve. In this embodiment, the current value Id=10 μA, and the gate voltage V _{T initial} corresponding to the current value of the transistor to be tested can be obtained by combining the current value with the Id-Vgs transfer characteristic curve.

Step 3, short-circuit all the pins of the transistor to be tested in the programming state in step 1, and place it in a radiation field where the radiation dose is D=5krad (Si) and take it out after the first irradiation, using semiconductor parameters The second characteristic curve is obtained through measurement by the test device; the second characteristic curve refers to the Id-Vgs transfer characteristic curve of the transistor to be tested after irradiation.

In this embodiment, the radiation field is ^{a 60} Co-γ ray radiation field or an X-ray radiation field, and other types of ray radiation fields can also be selected according to actual conditions. The radiation dose D=5krad(Si) is the most sensitive radiation dose point of the transistor under test, that is, at this dose point, the threshold voltage drift of the transistor under test is the largest. If other semiconductor transistors are measured, the radiation dose of the radiation field should be set according to the actual needs and the most sensitive radiation dose point of the semiconductor transistor.

Step 4: Select the same current value Id as in step 2 (ie Id=10 μA) from the second characteristic curve in step 3, and then obtain the gate voltage V _T corresponding to the current value of the transistor to be tested after irradiation.

Step 5, combine the gate voltage V _T1 of step 2 and the gate voltage V _T of step 4 to obtain the difference ΔV _T1 of the gate voltage of the transistor to be tested, wherein, ΔV _T1 = V _T1 - V _{T after} ; The difference ΔV _T1 of the pole voltage is the difference of the threshold voltage of the transistor to be tested after the first irradiation, and this difference is taken as a physical parameter characterizing the radiation dose of the transistor to be tested.

Step 6: Perform an erase operation on the transistor to be tested to remove the charge in the transistor to be tested, and repeat N times of radiation measurement according to the method from step 1 to step 5, and obtain the difference in threshold voltage of the transistor to be tested after N times of radiation Values ΔV _T2 , ΔV _{T3 .} . . ΔV _TN , where N≥5.

In this step, the erasing operation is to apply a low voltage to the gate of the transistor to be tested, and ground the source, drain and substrate, so that the charge in the transistor to be tested is 0, and the low voltage is -5~-10V. In this embodiment, the value of N is 10, that is, 10 radiation dose measurements are performed on the transistor to be tested, and the radiation dose cumulative value for the 10th time is 50 krad(Si). Every time before the next radiation dose measurement, the transistor to be tested needs to be erased, and then charged to make it in the programming state before irradiating. After the last radiation measurement, there is no need to To perform an erase operation, only the test data needs to be read.

Step 7: Calculate the cumulative radiation dose after each irradiation according to the number of times the transistor to be tested is irradiated, and then combine the threshold voltage difference ΔV _T1 , ΔV _T2 , ΔV _T3 , ΔV _T4 , ΔV _T5 after each irradiation, ΔV _T6 , ΔV _T7 , ΔV _T8 , ΔV _T9 , ΔV _T10 , you can calculate the change curve of the difference between the threshold voltage of the transistor to be tested and the cumulative value of radiation dose (as shown in Figure 1), and then complete the floating gate structure semiconductor Radiation Dosimetry of Transistors.

In this embodiment, the change curve of the threshold voltage difference of the transistor to be tested and the radiation dose cumulative value can be expressed as: ΔV _TN =A·Dose ⁿ

In the formula, ΔV _TN is the threshold voltage drift, that is, the difference between the threshold voltage of the transistor to be tested; Dose is the radiation dose, A is a constant, and the n value represents the response linearity, and 0≤n≤1, the closer the n value is to 1, The higher the linearity, the lower it is.

After obtaining the change curve of the difference between the threshold voltage of the transistor to be tested and the cumulative radiation dose, any such semiconductor transistor can be placed in an unknown radiation field, based on the above change curve and the semiconductor transistor obtained by the Id-Vgs transfer characteristic curve The difference of the threshold voltage of the semiconductor transistor can be implemented to obtain the radiation dose of the radiation field where the semiconductor transistor is located.

The radiation dose measurement method of the present invention is based on the detection technology of radiation dosimeters with strong applicability and easy implementation, so as to obtain the radiation dose test information of floating gate structure devices, and the method provides theoretical guidance, methods and techniques for developing domestic floating gate dosimeters The establishment is positive.

Above, although the embodiments of the present invention have been shown and described, for those skilled in the art, as long as they are within the scope of the spirit of the present invention, changes and modifications to the above embodiments should be regarded as Fall into the protection scope of the present invention.

Claims (8)

1. A radiation dose measurement method based on a floating gate structure semiconductor transistor, characterized in that, comprising the following steps: Step 1, charging the transistor to be tested to make it in a programming state, and using a semiconductor parameter testing device to measure and obtain a first characteristic curve; the transistor to be tested is a semiconductor transistor with a floating gate structure; the first characteristic curve refers to the initial Id-Vgs transfer characteristic curve of the transistor under test before irradiation; Step 2, selecting a current value Id from the first characteristic curve described in step 1, and then obtaining _{the corresponding gate voltage V T} of the transistor to be tested under this current value; Step 3, short-circuit all the pins of the transistor to be tested in the programming state in step 1, place it in the radiation field for the first irradiation, take it out, and use the semiconductor parameter testing device to measure and obtain the second characteristic curve; The second characteristic curve refers to the Id-Vgs transfer characteristic curve of the transistor to be measured after irradiation; Step 4, selecting the same current value Id as in step 2 from the second characteristic curve described in step 3, and then obtaining the gate voltage V _T corresponding to the current value of the transistor to be tested after being irradiated; Step 5, combining the gate voltage V _T1 of step 2 and the gate voltage V _T1 of step 4 to obtain the difference ΔV _T1 of the threshold voltage of the transistor to be tested after the first irradiation, where ΔV _T1 =V _{T11 After -V T} ; ΔV _T1 is used as a physical parameter characterizing the radiation dose of the transistor to be tested; Step 6: Perform an erase operation on the transistor to be tested to remove the charge in the transistor to be tested, and repeat the radiation measurement N times according to the method from step 1 to step 5, and obtain the difference of the threshold voltage of the transistor to be tested after irradiation ΔV _T2 , ΔV _T3 ... ΔV _TN , where N≥5; Step 7: Calculate the radiation dose cumulative value after each irradiation according to the number of times the transistor to be tested is irradiated, and then combine the threshold voltage difference ΔV _T1 , ΔV _T2 , ΔV _T3 ... ΔV _TN after each irradiation to obtain The variation curve of the difference value of the threshold voltage of the transistor to be tested and the cumulative value of the radiation dose is used to complete the radiation dose measurement of the semiconductor transistor with a floating gate structure. 2. the radiation dose measurement method based on floating gate structure semiconductor transistor according to claim 1, is characterized in that: In step 1, the charging operation is to connect the source and gate of the transistor to be tested with an external voltage, and ground the source and substrate of the transistor to be tested, so that the transistor to be tested is charged, and then shift after 0.1s to 10s. Remove the external voltage to complete the charging operation. 3. the radiation dose measurement method based on floating gate structure semiconductor transistor according to claim 2, is characterized in that: The applied voltage is 5-10V. 4. the radiation dose measurement method based on floating gate structure semiconductor transistor according to claim 3, is characterized in that: In step 2, the current value Id ranges from 1 to 10 μA. 5. the radiation dose measurement method based on floating gate structure semiconductor transistor according to claim 4, is characterized in that: In step 3, the radiation field is ^{a 60} Co-γ-ray radiation field or an X-ray radiation field. 6. the radiation dose measurement method based on floating gate structure semiconductor transistor according to claim 5, is characterized in that: In step 3, the radiation dose of the radiation field D=5krad(Si). 7. the radiation dose measurement method based on floating gate structure semiconductor transistor according to claim 6, is characterized in that: In step 6, the erasing operation is to apply a low voltage to the gate of the transistor to be tested, and ground the source, drain and substrate, so that the charge in the transistor to be tested is 0; the low voltage is -5 ~-10V. 8. the radiation dose measurement method based on floating gate structure semiconductor transistor according to claim 7, In step 6, the value of N is 10.

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