Impurity detection method, test plate, and detection device

Abstract

Provided is a detection method for detecting impurities contained in a liquid. The detection method employs a test plate (10) that includes a substrate (11) and a plurality of detection regions (20) formed on the surface of the substrate (11), wherein each of the detection regions (20) is composed of a first electrode (21) formed on the surface of the substrate (11) and a second electrode (22) formed on the surface of the substrate (11), separated from the first electrode (21). By applying an AC voltage between the first electrode (21) and the second electrode (22) and measuring the impedance, for each detection region (20), detection regions (20) in which an impurity (30) is present are identified and the impurity (30) is detected.

Description

Method for detecting impurities, test plate, and detection device

[0001] The present invention relates to the detection of impurities contained in a liquid, and in particular to a method for detecting impurities and a test plate and a detection device used to carry out the method.

[0002] Liquids such as ultrapure water, organic solvents such as isopropyl alcohol, and aqueous solutions of various acids and bases are used in the manufacture of semiconductor devices and pharmaceuticals. These liquids require significant reductions in impurity content, while also controlling the nature and quantity of impurities. For example, ultrapure water is used to clean semiconductor wafers in semiconductor device manufacturing, and the particles contained in this water have a direct impact on the yield of semiconductor products. Therefore, strict control of both the particle size and concentration of particles contained in the ultrapure water used for cleaning semiconductor wafers is required. For example, the particle concentration, i.e., the number of particles contained in a unit volume of ultrapure water, must be controlled to a specified value or less. Furthermore, the concentration of particle precursors (PPs), which are dissolved in solvents such as ultrapure water but precipitate as particles upon evaporation of the solvent, must also be controlled.

[0003] A known method for detecting particles in ultrapure water is the light scattering method, which irradiates laser light and detects scattered light from particles. This method has been put to practical use as a particle counter (particle measuring instrument) for detecting the number of particles in a liquid. Light scattering allows for online detection of particles with a particle size of, for example, 20 nm or larger. Another method involves centrifugal filtration, using a membrane that allows water but not particles to pass through. The membrane is then trapped on a filter, and the surface of the filter is observed with an optical microscope or a scanning electron microscope (SEM) to detect the particles. Direct microscopy detects particles with a particle size of, for example, 10 nm or larger, and the particle concentration in the ultrapure water can be calculated from the number of particles and the amount of water passing through the filter membrane. When using an SEM, the elemental composition of the particles can also be determined by detecting characteristic X-rays. Because particle precursors in a liquid do not scatter light and pass through the filter membrane, the concentration of particle precursors cannot be determined by light scattering or direct microscopy. A method that can also detect fine particle precursors is the spray drying method, in which a liquid to be measured, such as ultrapure water, is sprayed into the air to vaporize it, and the fine particles that remain floating without vaporizing are counted. According to the spray drying method, by using a condensation particle counter (CPC) to count the fine particles, fine particles with a particle size of, for example, about 3 nm or more can be detected, and fine particle precursors can also be detected because they remain as fine particles upon vaporization. This spray drying method enables online fine particle counting. Another example of the spray drying method is a method in which a liquid to be measured is sprayed onto a solid surface, such as a wafer, to vaporize it, and the fine particles remaining on the solid surface are detected using an optical microscope or SEM.

[0004] As mentioned above, one method for detecting particles present on the surface of a silicon semiconductor wafer or the like is to observe using an SEM. This method allows the position of particles on the wafer, for example, particles with a diameter of about a few nanometers, to be determined, and the elements that make up each particle can be determined by detecting the characteristic X-rays generated during SEM observation. Another method involves scanning the wafer surface with light and detecting reflected or scattered light to determine the location and density of particles, which can detect particles with a diameter of 10 or more nanometers. By scanning the wafer surface with laser light and detecting Raman light due to the surface-enhanced Raman effect, particles with a diameter of a few nanometers or more present on the wafer surface can be detected and their composition determined.

[0005] When particles are present in a liquid or on a solid surface, the particles have an inherent dielectric constant, which changes the capacitance value obtained by performing impedance measurements on electrodes placed near the particles. In particular, the complex dielectric constant and its frequency dependence of the particles are determined depending on the type and composition of the particles. Therefore, the type and composition of the particles can be evaluated by performing complex impedance measurements and analyzing the frequency change. In such methods for detecting particles using impedance measurements, a pair of electrodes are placed across a liquid, and an AC voltage is applied between the electrodes to measure the complex impedance between the electrodes. Methods based on impedance measurements are used, for example, to identify biological cells dispersed in a liquid. When used to identify biological cells, the method is called dielectric cytometry.

[0006] In Patent Document 1, in order to accurately measure the physical properties of a sample in a solution, particularly the physical properties of biological cells, by complex impedance measurement, a plurality of first electrodes are arranged in an array (matrix) on the bottom surface of a solution bath that contains the solution, a second electrode is arranged so as to be immersed in the solution, and the surface area of ​​the part of the first electrode that is exposed to the solution bath is set to 0.1 μm 2 100 μm or more 2The following publication discloses detecting a sample in a solution by a change in dielectric constant. This method allows the physical properties of a sample present near a first electrode to be measured. Patent Document 2 also discloses arranging a plurality of capacitance sensor elements in a matrix on a substrate surface and arranging a counter electrode facing the substrate surface, detecting a cell based on a change in capacitance value observed at the capacitance sensor electrode when the cell is present near the capacitance sensor electrode, and detecting the size of the cell based on the range of capacitance sensor elements in which a change in capacitance value is observed.

[0007] Patent Document 3 discloses a system for non-contact measurement of changes in capacitance caused by a measurement object such as a liquid, in which a capacitance-type sensor is configured by a sensor unit having electrodes provided on both surfaces of a substrate to form capacitance, and a container for placing the measurement object. The capacitance-type sensor is positioned so that when the measurement object is placed in the container, one electrode is close to the container but does not come into contact with the measurement object across the container, and the capacitance value of the sensor is measured in this state.

[0008] International Publication No. 2019 / 240202 International Publication No. 2020 / 059355 Japanese Patent Application Laid-Open No. 2019-117070

[0009] Among the methods for detecting impurities such as fine particles contained in a liquid, the light scattering method and direct microscopy method cannot detect fine particle precursors that become fine particles after evaporation or drying. Furthermore, when observing a solid surface such as a wafer using an optical microscope or SEM to detect fine particles present on the solid surface, if the particle diameter of the fine particles to be detected is small, the observation magnification must be increased, which increases the time required to scan the solid surface and therefore increases the time required to determine the number of fine particles.

[0010] An object of the present invention is to provide a detection method capable of detecting minute amounts of impurities such as fine particles contained in a liquid in a short period of time, and a test plate and detection device used to implement this detection method.

[0011] The detection method of the present invention is a method for detecting impurities contained in a liquid, and uses a test plate having a substrate and a plurality of detection regions formed on the surface of the substrate, each of the detection regions being composed of a first electrode formed on the surface of the substrate and a second electrode formed on the surface of the substrate at a distance from the first electrode.An AC voltage is applied between the first electrode and the second electrode for each detection region to perform impedance measurements, thereby identifying the detection region in which the impurities are present and detecting the impurities.

[0012] The test plate of the present invention is a test plate used to detect impurities contained in a liquid, and comprises a substrate and a plurality of detection areas formed on the surface of the substrate, each of the detection areas being composed of a first electrode formed on the surface of the substrate and a second electrode formed on the surface of the substrate at a distance from the first electrode.

[0013] The detection device of the present invention is a detection device for detecting impurities contained in a liquid, and includes the test plate of the present invention, an oscillator circuit that generates an AC voltage, and a sensor that detects current. By applying an AC voltage between the first electrode and the second electrode and performing impedance measurement, the detection area where the impurities are present is identified and the impurities are detected.

[0014] According to the present invention, minute amounts of impurities such as fine particles and fine particle precursors contained in a liquid can be detected in a short period of time.

[0015] FIG. 1A is a plan view showing the main parts of a test plate used in one embodiment of the detection method. FIG. 1B is a perspective view illustrating the detection regions of the test plate. FIG. 1C is a cross-sectional view of the test plate. FIGS. 1D and 1E are plan and perspective views, respectively, showing the state in which impurities are attached to the test plate. FIG. 1F is a diagram illustrating the principle of impurity detection using the test plate. FIG. 2 is a diagram illustrating a detection device including a test plate in which detection regions are arranged in a matrix. FIG. 3 is a diagram illustrating an example of a specific circuit configuration of the detection device. FIGS. 4A and 4B are plan views showing the main parts of a test plate with a different configuration, and FIG. 4C is a diagram illustrating another example of a specific circuit configuration of the detection device. FIGS. 5A, 5B, and 5C are diagrams illustrating how to use the test plate. FIG. 6 is a graph illustrating the results of Example 1. FIG. 7 is a graph illustrating the results of Example 2.

[0016] Next, an embodiment of the present invention will be described with reference to the drawings. The detection method according to the present invention is a method for detecting impurities contained in a liquid. The liquid to be detected for impurities may be pure water, ultrapure water, an organic solvent, or a solution of some kind of chemical. The impurities may be particles that remain in a solid phase in the liquid, or particle precursors that are dissolved in the liquid but precipitate and remain when the liquid evaporates. The detection method according to the present invention is characterized by the use of a test plate having multiple detection regions on its surface. Therefore, the test plate will be described first. FIGS. 1A to 1F are diagrams illustrating a detection method according to one embodiment. FIG. 1A is a plan view showing the main parts of the test plate, FIG. 1B is a perspective view illustrating the detection regions, FIG. 1C is a cross-sectional view of the test plate, FIGS. 1D and 1E are plan and perspective views, respectively, showing the state in which impurities are attached, and FIG. 1F is a diagram illustrating the principle of impurity detection using the test plate.

[0017] The test plate 10 includes a substrate 11, such as a silicon semiconductor substrate, and as shown in FIG. 1A , multiple detection regions 20 are provided on the surface of the test plate 10. While FIG. 1A shows three detection regions 20, the test plate 10 may actually include more detection regions 20. Each detection region 20 includes a first electrode 21 formed on the surface of the substrate 11 and a second electrode 22 formed on the surface of the substrate 11 at a distance from the first electrode 21. The substrate 11 is exposed between the electrodes 21 and 22. The electrodes 21 and 22 are formed of metals such as aluminum (Al), titanium (Ti), gold (Au), platinum (Pt), silver (Ag), and copper (Cu). FIG. 1B shows an enlarged view of the detection region 20. Both electrodes 21 and 22 have a rectangular shape with a uniform thickness. If the distance between the electrodes 21 and 22 is d, the area of ​​each of the opposing side surfaces of the electrodes 21 and 22 is S, and the dielectric constant is ε, the capacitance C between the electrodes 21 and 22 can be approximated by equation (1).

[0018] C=ε・S / d (1)

[0019] As shown in FIG. 1C , the substrate 11 has insulating layers 13 and 14 stacked on one surface of the semiconductor layer 12. The top surface of the insulating layer 14 in the figure is the surface of the substrate 11, and electrodes 21 and 22 are formed thereon. Wiring 23 and 24 are embedded in the substrate 11, electrically connecting to the electrodes 21 and 22, respectively. More specifically, the wiring 23 and 24 are located at the interface between the insulating layers 13 and 14 and electrically connected to the electrodes 21 and 22 through vias 25 and 26 formed in the insulating layer 14. The insulating layers 13 and 14 may be made of, for example, silicon oxide or silicon nitride. The wiring 23 and 24 may be made of, for example, aluminum, titanium, gold, platinum, silver, or copper, while the vias 25 and 26 may be made of, for example, aluminum, tungsten, or titanium. A protective layer may be provided on the surface of the test plate 10, including the surfaces of the electrodes 21 and 22. Silicon oxide, silicon nitride, or the like may be used for the protective layer. The test plate 10 can be manufactured using known semiconductor device manufacturing techniques.

[0020] FIG. 1D is a plan view of the test plate 10, similar to FIG. 1A, showing the state in which an impurity 30 is attached to the central detection region 20. Similarly, FIG. 1E is a perspective view of the detection region 20, similar to FIG. 1B, showing the state in which an impurity 30 is attached to the detection region 20. Because the impurity 30 has a specific dielectric constant ε depending on its composition, the presence of the impurity in the detection region 20 changes the capacitance C between the first electrode 21 and the second electrode 22 in that detection region 20 compared to when the impurity is not present. Since the change in capacitance C can be detected by impedance measurement performed by applying an AC voltage, the detection method according to the present invention applies an AC voltage between the electrodes 21 and 22 for each detection region 20 of the test plate 10 to perform impedance measurement, and determines whether or not an impurity 30 is attached to the surface of the test plate 10 in the detection region 20 based on the measurement result or change in the measurement result. By sequentially performing impedance measurements on multiple detection regions 20, it is possible to identify which detection region 20 has the impurity 30 attached. In this embodiment, the impurities 30 are detected by measuring the impedance between the electrodes 21 and 22, so the distance between the electrodes 21 and 22 is preferably set according to the particle size of the impurities 30 to be detected. The distance between the electrodes 21 and 22 is, for example, about 10 nm to 500 μm, but when attempting to detect fine particles with particle sizes of about several tens of nanometers as impurities, the distance is set to, for example, 10 nm to 100 nm.

[0021] Regarding the impurities 30, which are fine particles, the complex dielectric constant and its frequency dependence of the impurities 30 depend on the type and composition of the impurities 30. Therefore, by performing complex impedance measurements while changing the frequency of an AC voltage and analyzing the frequency change, the type and composition of the impurities 30 can be evaluated. Furthermore, if it is possible to identify which of the multiple detection regions 20 on the test plate 10 the impurities 30 are attached to, the shape of the impurities 30 can be determined in a short time by observing the test plate 10 with, for example, an optical microscope or SEM. Furthermore, the elements constituting the impurities 30 can be determined by analyzing the energy of X-rays generated during SEM observation. Since the position of the impurities 30 on the test plate 10 is known, the composition of the impurities 30 can also be determined by pinpointing the position and performing Raman spectroscopy or infrared spectroscopy.

[0022] FIG. 1F illustrates the principle of impurity detection using the test plate 10 and shows the circuit configuration for impedance measurement. An oscillator circuit 41 with a controllable oscillation frequency is provided. One terminal of the oscillator circuit 41 is connected to a first electrode 21 in the detection area 20, and a second electrode 22 in the same detection area 20 is connected to one input of a measurement unit 42. The other terminal of the oscillator circuit 41 is connected to the other input of the measurement unit 42. The measurement unit 42 has the function of measuring the current flowing from the oscillator circuit 41 through the first electrode 21 and the second electrode 22 to the measurement unit 42 and then returning to the oscillator circuit 41. The impedance between the electrodes 21 and 22 can be measured from the output voltage of the oscillator circuit 41 and the current flowing through the measurement unit 42. A control unit 43 is provided to process the measurement results from the measurement unit 42 and controls the oscillation frequency of the oscillator circuit 41.

[0023] In the test plate 10, a plurality of detection regions 20 are arranged, for example, in a matrix, i.e., constituting a matrix. FIG. 2 shows an example of the configuration of a detection device including a test plate 10 in which a plurality of detection regions 20 are arranged in a matrix. In the example shown in FIG. 2, the detection regions 20 are arranged in a matrix of 16 rows and 16 columns, but it is also possible to increase the number of detection regions 20 provided on the test plate 10. Shift register circuits 51 and 52 are provided to sequentially select the detection regions 20 in the matrix. A measurement unit 42 is provided in common to a plurality of columns in the matrix. One end of an oscillation circuit 41 is connected to the measurement unit 42, and the other end of the oscillation circuit 41 is grounded. FIG. 3 shows a specific circuit configuration of this test device.

[0024] The measuring unit 42 includes a common voltage application line 61 connected to one end of the oscillator circuit 41, a voltage sensor 62 provided between the common voltage application line 61 and a ground point to measure the output voltage of the oscillator circuit 41, a current measurement line 63, a current sensor 64 provided between the current measurement line 63 and a ground point to detect the current flowing therethrough, and a selection transistor 65. The selection transistors 65 are provided corresponding to each column of the matrix of the test plate 10. In the test plate 10, a word line 53 is provided for each row of the matrix, and a voltage application line 54 and a bit line 55 are provided for each column. Each detection region 20 is provided with a selection transistor 27. The selection transistor 27 is embedded in the substrate 11 of the test plate 10. In each detection region 20, the gate of the selection transistor 27 is connected to the word line 53 of the corresponding row, one of the drain and source of the selection transistor 27 is connected to the first electrode 21, and the other is connected to the bit line 55 of the corresponding column. Therefore, when an enable signal is input via word line 53, selection transistor 27 electrically connects first electrode 21 to bit line 55 of the corresponding column. Second electrode 22 is connected to voltage application line 54 of the corresponding column. Voltage application line 54 of each column is connected to common voltage application line 61 in measurement unit 42.

[0025] The shift register circuit 52 and the measurement unit 42 are connected by selection lines 56 provided for each column of the matrix of the test plate 10. Each bit line 55 extends into the measurement unit 42. In the measurement unit 42, the gate of the selection transistor 65 for each column is connected to the selection line 56 for the corresponding column from the shift register circuit 52. When an enable signal is input via the selection line 56, the selection transistor 65 electrically connects the bit line 55 of the corresponding column to a current measurement line 63. With this circuit configuration, a specific detection area 20 in the matrix of the test plate 10 is selected by specifying a row and column using the shift register circuits 51 and 52. In the selected detection area 20, a voltage generated by the oscillation circuit 41 is applied between the second electrode 22 and the first electrode 21, and the resulting current flows from the bit line 55 to the current measurement line 63. A current sensor 64 is provided on the current measurement line 63, allowing impedance measurement.

[0026] In the examples shown in FIGS. 2 and 3 , a second electrode 22 is provided for each detection region 20. However, because the second electrodes 22 are constantly connected to the oscillator circuit 41 via the voltage application line 54 and the common voltage application line 61, a common second electrode 22 can also be provided for the detection regions 20 belonging to the same column of the matrix of the test plate 10. In this case, the second electrode 22 is provided extending in the column direction across multiple detection regions 20. FIGS. 4A to 4C are diagrams illustrating a case in which a common second electrode 22 is provided for each column of the test plate 10. FIG. 4A is a plan view similar to FIG. 1A , depicting the main parts of the test plate 10; FIG. 4B is a plan view similar to FIG. 1D , depicting the main parts of the test plate 10 with impurities 30 attached; and FIG. 4C is a diagram similar to FIG. 3 depicting the configuration of the main parts of a detection device including the test plate 10.

[0027] As described above, the detection method according to the present invention first determines whether or not the impurity 30 is present between the first electrode 21 and the second electrode 22 provided on the surface of the test plate 10. Here, a method for using the test plate 10 to enable detection of the impurity 30 will be described. Figures 5A to 5C are diagrams illustrating the method for using the test plate 10.

[0028] In the method shown in FIG. 5A , a liquid 70 containing impurities 30 is dropped onto the test plate 10. Impurities can be detected by performing impedance measurements in this state. However, to prevent the influence of the size of the dropped droplets, a drying process is preferably performed after the dropping to vaporize the liquid 70 and leave only the impurities 30 on the test plate. In the drying process, the test plate 10 may be kept at room temperature to vaporize the liquid, or the test plate 10 may be heated to promote liquid vaporization. The dropped liquid 70 may have previously undergone a process of extracting or concentrating the impurities 30. Since the microparticle precursors do not vaporize, the microparticle precursors can be detected as impurities 30 by performing a drying process. If a test plate 10 having detection regions 20 arranged in a matrix is ​​used, and the amount of impurities in the liquid 70 is so small that the number of detection regions 20 in which impurities 30 are detected can be considered the number of impurities 30, the concentration of impurities 30 in the liquid 70 or the number per unit volume can be calculated from the amount of liquid dropped and the number of detection regions 20 in which impurities are detected.

[0029] 5B, a liquid 70 containing impurities 30 is sprayed above the test plate 10, and the liquid 70 is vaporized in the atmosphere, while the impurities 30 alone fall and are collected on the test plate 10. This method also makes it possible to detect the particle precursors, and the concentration of the impurities 30 in the liquid 70 or the number of impurities 30 per unit volume can be calculated from the amount of sprayed liquid 70 and the number of detected impurities 30.

[0030] 5C , for example, the test plate 10 is attached to the bottom of a tank that stores the liquid 70 so that the liquid comes into direct contact with the test plate 10. This method cannot detect the particle precursors as impurities 30, but it can detect impurities when the impurities dissolve in the liquid and the dielectric constant of the liquid 70 changes.

[0031] The surface of the test plate 10 is flat except for the first electrode 21 and the second electrode 22, and no through-holes or the like are open on the surface of the test plate 10. Therefore, after the test plate 10 has been used to detect impurities 30 in the liquid 70, it can be washed and used again to detect impurities 30. This is a major advantage of the method based on the present invention compared to the fact that filtration membranes for capturing fine particles cannot basically be reused.

[0032] Next, the present invention will be described in more detail with reference to examples.

[0033] Example 1 In Example 1, the capacitance C between the electrodes 21 and 22 was measured when a liquid containing impurities and a liquid not containing impurities were dropped onto the test plate 10 as shown in FIG. 5A. Several types of test plates 10 were used, each with a different distance d between the electrodes 21 and 22 ranging from 10 μm to 200 μm. Liquids containing impurities were used, each containing 1% and 9% magnesium oxide (MgO) dispersed in ultrapure water. Ultrapure water was used as the liquid not containing impurities. The results are shown in FIG. 6.

[0034] As can be seen from Figure 6, the capacitance value changed depending on whether or not the liquid contained impurities, and if so, the concentration of the impurities. The capacitance C observed between the electrodes 21 and 22 generally increased as the distance d between the electrodes 21 and 22 decreased, and was also larger when the liquid contained impurities than when it did not. Considering the difference in capacitance from when no impurities were present, this difference increased as the impurity concentration in the liquid increased. This shows that by bringing the liquid into contact with the test plate 10, it is possible to detect whether or not the liquid contained impurity particles, and also to evaluate the concentration of the impurity particles.

[0035] Example 2 In Example 2, the capacitance C between the electrodes 21 and 22 was measured when a liquid containing impurities and a liquid not containing impurities were dropped onto the test plate 10 as shown in FIG. 5A . The test plate 10 used was different from that used in Example 1, and multiple types of test plates were used, each with a distance d between the electrodes 21 and 22 ranging from 2 μm to 100 μm. The liquid containing impurities was a liquid in which magnesium oxide (MgO) was dispersed in ultrapure water to a concentration of 1% by mass. The liquid not containing impurities was ultrapure water. As control data, the capacitance C between the electrodes 21 and 22 was also measured when no liquid was dropped. The results are shown in FIG. 7 .

[0036] 7, the capacitance C between the electrodes 21 and 22 changes when the liquid is dropped, and this change increases when the distance d between the electrodes 21 and 22 is small and when the liquid contains impurities. Furthermore, when the distance d between the electrodes 21 and 22 is 2 μm, the capacitance C changes depending on whether or not there are impurities in the liquid, which indicates that impurity particles with a particle size of at least 2 μm can be detected.

[0037] REFERENCE SIGNS LIST 10 Test plate 11 Substrate 12 Semiconductor layer 13, 14 Insulating layer 20 Detection area 21, 22 Electrodes 23, 24 Wiring 30 Impurity 41 Oscillation circuit 42 Measuring unit 43 Control device 51, 52 Shift register circuit 70 Liquid

Claims

1. A detection method for detecting impurities contained in a liquid, comprising: a test plate having a substrate and a plurality of detection regions formed on the surface of the substrate, each of the detection regions being composed of a first electrode formed on the surface of the substrate and a second electrode formed on the surface of the substrate at a distance from the first electrode; and applying an AC voltage between the first electrode and the second electrode for each detection region to perform impedance measurement, thereby identifying the detection region in which an impurity is present and detecting the impurity.

2. The detection method according to claim 1, wherein the impurities are detected while the liquid is in contact with the surface of the test plate.

3. The detection method according to claim 1, wherein the liquid is brought into contact with the surface of the test plate, and then the liquid is vaporized before the impurities are detected.

4. The detection method according to claim 1, wherein the liquid is vaporized by spraying, and the remaining impurities are captured on the surface of the test plate before the impurities are detected.

5. The detection method according to any one of claims 1 to 4, wherein the plurality of detection regions are arranged in a matrix on the test plate, and the detection region in which the impurity is present is identified by sequentially selecting rows and columns in the matrix to select the plurality of detection regions in the matrix one by one and performing the impedance measurement.

6. A detection method according to any one of claims 1 to 4, wherein the impedance measurement is carried out while changing the frequency of the AC voltage.

7. A test plate used to detect impurities contained in a liquid, comprising: a substrate; and a plurality of detection areas formed on the surface of the substrate, each of the detection areas comprising a first electrode formed on the surface of the substrate and a second electrode formed on the surface of the substrate at a distance from the first electrode.

8. The test plate according to claim 7, wherein the plurality of detection regions are arranged in a matrix on the surface of the substrate.

9. The test plate according to claim 7 or 8, wherein wiring connected to said first electrode and wiring connected to said second electrode are embedded in said substrate.

10. The test plate according to claim 8, wherein the second electrode is provided in common to a plurality of the detection regions arranged in a column direction on the surface of the substrate.

11. The test plate according to claim 8 or 10, wherein the test plate includes word lines provided for each row and bit lines provided for each column, and each detection region includes a select transistor whose gate is connected to the corresponding word line and electrically connects the first electrode to the corresponding bit line.

12. A detection device for detecting impurities contained in a liquid, comprising the test plate according to claim 7, an oscillator circuit for generating an AC voltage, and a sensor for detecting a current, wherein the detection device applies an AC voltage between the first electrode and the second electrode to measure the impedance, thereby identifying the detection region where the impurities are present and detecting the impurities.

13. A detection device for detecting impurities contained in a liquid, comprising the test plate according to claim 8, a first shift register circuit and a second shift register circuit for selecting rows and columns in the matrix, respectively, an oscillation circuit for generating an AC voltage, and a sensor for detecting current, wherein the first shift register circuit and the second shift register circuit select a plurality of detection regions in the matrix one by one and perform the impedance measurement, thereby identifying the detection region in which an impurity is present and detecting the impurity.

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