JP2009222548A - Surface potential measurement method and surface potentiometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform quick and high-accuracy mesurement of the potential, at a plurality of measuring points on the sample surface. <P>SOLUTION: In this surface potentiometer 1, on the first measuring point among the plurality of measuring points set on the sample 9 surface 91, a relation between an electrode potential and a displacement current is obtained, while changing the electrode potential of a vibration electrode 12; and a plurality of relations are obtained, while changing a distance between the vibration electrode 12 and the sample 9 surface 91. Successively, a reference current (is), which is a displacement current from a sample holding part 11 independent of the distance between the vibration electrode 12 and the sample 9 surface 91 is determined, from the plurality of relations between the electrode potential and the displacement current. On all the second and after measuring points, an electrode potential, when the displacement current from the sample holding part 11 becomes equal to the reference current (is), is obtained as surface potential of the sample 9. As a result, measurement of the surface potential at the plurality of measuring points set on the sample 9 surface 91 can be performed quickly and with high accuracy. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for measuring the surface potential of a sample.

  Conventionally, a non-contact type surface potential meter has been used to measure the surface potential of a substrate mounted with a photosensitive drum or IC of a copying machine, and one of such surface potential meters is called an alternating current method. There is a method. In the alternating current method, a vibrating electrode is brought close to a sample, and a surface potential is obtained based on a current from the vibrating electrode caused by a change in capacitance between the vibrating electrode and the sample. For example, in Patent Document 1, the distance between the vibrating electrode and the sample is estimated by detecting a change in the current from the vibrating electrode when the potential of the vibrating electrode is changed, and the current from the vibrating electrode is 0. Then, the surface potential of the sample is obtained by correcting the potential of the vibrating electrode based on the estimated distance.

  In recent years, the alternating current method has also been applied to the measurement of the potential of the insulating film surface in a semiconductor substrate on which an insulating film such as an oxide film is formed. For example, in the surface potential meter of Patent Document 2, the vibrating electrode is vibrated in a state where a sample which is a semiconductor substrate is placed on a conductive surface provided in the sample placing portion, and the potential of the vibrating electrode is changed while the vibrating electrode is changed. The relationship between the potential of the current and the current from the conductive surface of the sample mounting portion is acquired. Then, a plurality of the above relationships are acquired while changing the distance between the vibrating electrode and the sample, and the reference potential of the vibrating electrode that does not depend on the distance between the vibrating electrode and the sample is obtained from the plurality of relationships, A surface potential of the sample is obtained based on the reference potential.

In the surface potential meter of Patent Document 2, the surface potential is obtained by using the current from the sample mounting portion, thereby removing the influence of the stray capacitance between the vibrating electrode and the surrounding structure and improving the measurement accuracy. Is planned. Further, by obtaining the surface potential based on a plurality of relationships between the potential of the vibrating electrode and the current from the sample mounting portion, fluctuations in measurement accuracy due to the distance between the vibrating electrode and the sample can be prevented.
Japanese Patent Laid-Open No. 9-211046 JP 2007-240393 A

  By the way, in the surface potential meter of Patent Document 2, in the measurement of the surface potential at one measurement point on the sample, a plurality of combinations of the potential of the vibrating electrode and the current from the sample mounting portion are changed while changing the potential of the vibrating electrode. (That is, the relationship between the potential and the current) is acquired, and further, the acquisition of the plurality of combinations is repeated by changing the distance between the vibrating electrode and the sample. For this reason, when a large number of measurement points are set on the semiconductor substrate, a relatively long measurement time is required to obtain the surface potential at all the measurement points.

  The present invention has been made in view of the above problems, and an object thereof is to perform potential measurement at a plurality of measurement points on the surface of a sample quickly and with high accuracy.

  The invention according to claim 1 is a surface potential measuring method for measuring a surface potential of a sample, wherein a) a step of holding a flat plate-like sample on a sample holder, and b) set on the surface of the sample. A step of causing the electrode to face one measurement point included in the plurality of measurement points in a non-contact manner; and c) the sample from the electrode by the piezoelectric element of the vibration unit connected to one of the electrode and the sample holding unit. The electrode is vibrated relative to the sample in the vibration direction toward the holding unit, and the relationship between the electrode potential and the displacement current from the electrode or the sample holding unit is acquired while changing the electrode potential of the electrode. And d) a step of repeating the step c) by changing the measurement condition for changing the relationship between the electrode potential and the displacement current, and e) a plurality of measurement conditions acquired by the step c) and the step d). Electrode potential and displacement corresponding to A step of obtaining a combination of an electrode potential and a displacement current that does not depend on the plurality of measurement conditions from a plurality of relationships with the flow, and storing the displacement current of the combination as a reference current; and f) based on the electrode potential of the combination Obtaining a surface potential at the one measurement point; and g) moving the electrode parallel to the surface of the sample so as to oppose other measurement points included in the plurality of measurement points; h ) Changing the electrode potential of the electrode, and obtaining a surface potential at the other measurement point based on the electrode potential when the displacement current from the electrode or the sample holder becomes equal to the reference current; Prepare.

  The invention according to claim 2 is the surface potential measuring method according to claim 1, wherein the step g) and the step h) are repeated until the measurement for all of the plurality of measurement points is completed.

  The invention according to claim 3 is a surface potential measuring method for measuring the surface potential of a sample, wherein a) a step of holding a flat sample on a sample holder, and b) a non-electrode on the surface of the sample. And c) relative to the sample in a vibration direction from the electrode toward the sample holding portion by the piezoelectric element of the vibrating portion connected to one of the electrode and the sample holding portion. And obtaining the relationship between the electrode potential of the electrode and the displacement current from the electrode or the sample holder while changing the electrode potential of the electrode, and d) the relationship between the electrode potential and the displacement current A step of repeating the step c) by changing the measurement condition for changing the pressure, and e) a plurality of relationships between the electrode potential and the displacement current corresponding to the plurality of measurement conditions acquired by the step c) and the step d) From the plurality of measurements. Obtaining a combination of an electrode potential and a displacement current independent of conditions and storing the displacement current of the combination as a reference current; and f) moving the electrode parallel to the surface of the sample to move the electrode to the surface. A step of facing one measurement point included in the plurality of measurement points above, and g) when the electrode potential of the electrode is changed and the displacement current from the electrode or the sample holder becomes equal to the reference current Obtaining a surface potential at the one measurement point based on the electrode potential; h) repeating the step f) and the step g) for other measurement points included in the plurality of measurement points; Is provided.

  The invention according to claim 4 is the surface potential measurement method according to any one of claims 1 to 3, wherein the step e) includes e1) an electrode potential and displacement current corresponding to the plurality of measurement conditions. A step of obtaining a temporary combination of an electrode potential and a displacement current that does not depend on the plurality of measurement conditions from the plurality of relationships, and e2) the electrode potential of the temporary combination is the step c) and the step d) And the provisional combination is the combination of the electrode potential and displacement current independent of the plurality of measurement conditions, and the electrode potential of the temporary combination is the step c) and The step c) and the step d) while changing the electrode potential of the electrode within a range including the electrode potential of the temporary combination when the electrode potential is outside the change range of the electrode potential in the step d). To obtain again a plurality of relationships between electrode potentials and displacement currents corresponding to a plurality of measurement conditions, and from the plurality of relationships between electrode potentials and displacement currents obtained again, electrodes that do not depend on the plurality of measurement conditions Determining the combination of potential and displacement current.

  A fifth aspect of the present invention is the surface potential measurement method according to any one of the first to fourth aspects, wherein the displacement current is acquired from the sample holder.

  The invention according to claim 6 is the surface potential measurement method according to any one of claims 1 to 5, wherein in the step d), the measurement condition is between the electrode and the surface of the sample. The distance is changed.

  The invention according to claim 7 is the surface potential measuring method according to any one of claims 1 to 6, wherein the steps a) to h) are sequentially performed on a plurality of samples.

  The invention according to claim 8 is a surface potentiometer for measuring the surface potential of a sample, a sample holding portion for holding a flat sample, an electrode facing the surface of the sample in a non-contact manner, and a piezoelectric A vibrating portion that vibrates the electrode relative to the sample in a vibrating direction from the electrode toward the sample holding portion by an element; an electrode potential of the electrode when the electrode is vibrated relatively; and the electrode Alternatively, a processing unit that obtains a displacement current from the sample holding unit, a surface potential calculation unit that obtains a surface potential of the sample based on the electrode potential and the displacement current, and the electrode parallel to the surface of the sample A plurality of movement mechanisms configured to move relative to the sample, and the vibration unit, the processing unit, the surface potential calculation unit, and the movement mechanism. At the measuring point A control unit that measures the surface potential of the sample; and b) the electrode is opposed to one measurement point included in the plurality of measurement points set on the surface of the sample in a non-contact manner. C) causing the electrode to vibrate relative to the sample in the vibration direction by the piezoelectric element of the vibration unit connected to one of the electrode and the sample holding unit, and Obtaining the relationship between the electrode potential and the displacement current from the electrode or the sample holder while changing, and d) changing the measurement condition for changing the relationship between the electrode potential and the displacement current, and the step c) An electrode potential independent of the plurality of measurement conditions from a plurality of relationships between the electrode potential corresponding to the plurality of measurement conditions and the displacement current obtained by the repeating step, e) the step c), and the step d) Pair with displacement current Obtaining a combination and storing the displacement current of the combination as a reference current; f) obtaining a surface potential at the one measurement point based on the electrode potential of the combination; and g) attaching the electrode to the sample. A step of moving parallel to the surface and facing another measurement point included in the plurality of measurement points; h) changing an electrode potential of the electrode, and a displacement current from the electrode or the sample holder is A step of acquiring a surface potential at the other measurement point based on the electrode potential when the current becomes equal to the reference current.

  In the present invention, potential measurement at a plurality of measurement points on the surface of a sample can be performed quickly and with high accuracy.

  FIG. 1 is a diagram showing a configuration of a surface electrometer 1 according to an embodiment of the present invention. As shown in FIG. 1, the surface potential meter 1 is a device that measures the surface potential of a flat sample 9 that is a semiconductor substrate by a vibration capacitance method that is one of AC methods.

  The surface electrometer 1 is positioned above the sample holding unit 11, a sample holding unit 11 that holds the sample 9 by suction, a moving mechanism 16 that moves the sample holding unit 11 horizontally (that is, parallel to the surface 91 of the sample 9). In addition, the vibrating electrode 12 that faces the surface 91 of the sample 9 in a non-contact manner, and has a piezoelectric element (that is, a piezoelectric actuator) and is attached to the opposite side of the vibrating electrode 12 from the sample holding portion 11, Elevating mechanism 14 that moves up and down 12, processing unit 2 that is a set of circuits and devices that process various electrical signals, computer 3 that is a surface potential calculation unit that determines the surface potential of sample 9, vibration unit 13, and processing The control part 4 which controls the part 2, the computer 3, and the moving mechanism 16 is provided. In the surface potential meter 1, the control unit 4 controls the vibration unit 13, the processing unit 2, the computer 3, and the moving mechanism 16, thereby measuring the surface potential at a plurality of measurement points set on the surface 91 of the sample 9. Is done.

  The sample holder 11 has a conductive surface 111 on which the sample 9 is placed so that the back surface of the sample 9 is in contact, and the vibrating electrode 12 faces the surface 91 and the conductive surface 111 of the sample 9 in a non-contact manner. To do. The area of the conductive surface 111 is sufficiently larger than the area of the tip of the vibrating electrode 12.

  The moving mechanism 16 includes a first moving mechanism 161 that moves the sample holder 11 in the left-right direction in FIG. 1 and a second moving mechanism 162 that moves the sample holder 11 in the depth direction in FIG. In the first moving mechanism 161, a ball screw (not shown) is connected to the motor 1611, and the motor 1611 rotates, whereby the second moving mechanism 162 moves along the guide rail 1612 in the left-right direction in FIG. The second moving mechanism 162 has the same configuration as that of the first moving mechanism 161. When the motor 1621 rotates, the sample holder 11 moves along the guide rail 1622 in the depth direction in FIG. Move to. In the surface electrometer 1, a desired portion on the surface 91 of the sample 9 is opposed to the vibrating electrode 12 by moving the sample 9 together with the sample holding unit 11 by the moving mechanism 16. In other words, the moving mechanism 16 is a moving mechanism that moves the vibrating electrode 12 relative to the sample 9 in parallel with the surface 91 of the sample 9.

  The vibrating electrode 12 is connected to the vibrating portion 13 via the insulating portion 131, and the vibration direction from the vibrating electrode 12 toward the sample 9 and the sample holding portion 11 is applied by applying an AC driving voltage to the piezoelectric actuator of the vibrating portion 13. The vibrating electrode 12 vibrates. The vibrating unit 13 is connected to the lifting mechanism 14, and the lifting unit 14 is driven to move the vibrating unit 13 up and down to change the vibration direction distance between the vibrating electrode 12 and the surface 91 of the sample 9. In other words, the elevating mechanism 14 is a distance changing mechanism that changes the distance between the vibrating electrode 12 and the surface 91 of the sample 9 by moving the vibrating electrode 12 relative to the sample 9 in the vibrating direction. is there. The periphery of the vibrating electrode 12 and the periphery of the sample holding unit 11 are covered with a cover 151, and the cover 151 and the sample holding unit 11 are supported by a vibration isolation member 152.

  The processing unit 2 converts a minute current from the conductive surface 111 of the sample holding unit 11 into a voltage and amplifies the preamplifier 21, an amplifier 22 that further amplifies a signal from the preamplifier 21, and a vibration signal to the vibration unit 13. An oscillator 23 to be applied, a synchronous detection circuit 24 to which signals from the oscillator 23 and the amplifier 22 are input, and a control circuit 25 including an operational amplifier 251 are provided. The current acquired from the conductive surface 111 of the sample holder 11 is mainly an alternating current generated due to a change in capacitance between the vibrating electrode 12 and the sample 9 due to vibration of the vibrating electrode 12. In the following description, this is referred to as “displacement current”.

  In the preamplifier 21, the voltage converted from the current value is amplified to about 10 to the power of 10 and further amplified to about 10 to the power of 10 in the amplifier 22. Thereby, for example, a current of 10 fA (femtoampere) is led to the operational amplifier 251 as a voltage of about 1 mV. The potential from the control circuit 25 is applied to the vibrating electrode 12. A voltage indicating the displacement current from the amplifier 22 and a signal from the oscillator 23 are input to the synchronous detection circuit 24, and the amplitude of the displacement current is output from the synchronous detection circuit 24 as the magnitude of the displacement current, and the operational amplifier 251 of the control circuit 25. Is input to the inverting input terminal (−).

  The non-inverting input terminal (+) of the operational amplifier 251 receives a current designation voltage that designates the magnitude of the displacement current from the computer 3, so that the input voltage from the synchronous detection circuit 24 becomes equal to the current designation voltage. The operational amplifier 251 applies a potential to the vibrating electrode 12. That is, feedback control using the operational amplifier 251 is performed by the processing unit 2, and the potential of the vibrating electrode 12 (hereinafter referred to as “electrode potential”) having the displacement current value from the conductive surface 111 as a specified current value is acquired. The The potential determined by the control circuit 25 is directly acquired by the computer 3.

  In the surface potential meter 1, the surface potential of the sample 9 can be measured by a plurality of types of measurement methods. In the following, first, among the plurality of types of measurement methods, the first measurement method will be described. . FIG. A and FIG. B is a diagram showing a flow of measurement of the surface potential of the sample 9 by the surface potential meter 1. FIG. When the surface potential of the sample 9 is measured, first, the sample 9 is held by the sample holding unit 11 with the back surface in contact with the sample holding unit 11 (step S11). Subsequently, when the moving mechanism 16 is controlled by the control unit 4, the sample 9 moves in the horizontal direction together with the sample holding unit 11, and the vibrating electrode 12 is placed at a plurality of measurement points set on the surface 91 of the sample 9. It is opposed to one included measurement point (hereinafter referred to as “first measurement point”) in a non-contact manner (step S12). Then, the distance between the vibrating electrode 12 and the surface 91 of the sample 9 is set to a predetermined value by the elevating mechanism 14 (step S13).

  Next, under the control of the control unit 4, a drive voltage is applied to the piezo actuator of the vibration unit 13, and the vibration electrode 12 starts to vibrate in the vibration direction (that is, the direction from the vibration electrode 12 to the sample 9) (step). S14) After the vibration of the vibrating electrode 12 is stabilized at a predetermined amplitude, a preset current designation voltage is input from the computer 3 to the control circuit 25 (step S15). As a result, the electrode potential of the vibrating electrode 12 is changed by feedback control so that the value of the displacement current from the sample holding unit 11 (that is, the maximum value of the absolute value of the current) becomes the value indicated by the current designation voltage. The electrode potential obtained in (1) is input to the computer 3. In other words, one combination of the electrode potential of the vibrating electrode 12 when the vibrating electrode 12 is vibrated relative to the sample 9 and the displacement current from the conductive surface 111 of the sample holding unit 11 is acquired ( Step S16).

  When the combination of the electrode potential and the displacement current is acquired, the process returns to step S15 (step S17), the current designation voltage is changed, and the electrode potential is acquired again (steps S15 and S16). In the surface electrometer 1, the current designation voltage is changed and the electrode potential is acquired a plurality of times (in this embodiment, 9 times), whereby the relationship between the electrode potential and the displacement current from the sample holder 11 ( That is, a plurality of combinations of electrode potential and displacement current are acquired (steps S15 to S17). In other words, the relationship between the electrode potential and the displacement current is acquired while changing the electrode potential of the vibrating electrode 12.

  When the relationship between the electrode potential and the displacement current is acquired by the operation of the processing unit 2 while the distance between the vibrating electrode 12 and the sample 9 is kept constant, the lifting mechanism 14 is controlled by the control unit 4. As a result, after the distance between the vibrating electrode 12 and the surface 91 of the sample 9 is changed by a predetermined magnitude (steps S18 and S181), the process returns to step S15 to change the current designation voltage and acquire the electrode potential. The relationship between the electrode potential and the displacement current is acquired again by repeating a plurality of times (steps S15 to S17). Then, by changing the distance between the vibrating electrode 12 and the surface 91 of the sample 9 and acquiring the relationship between the electrode potential and the displacement current a predetermined number of times, a plurality of relationships between the electrode potential and the displacement current are obtained. Obtained (steps S15 to S18, S181).

  FIG. 3 is a diagram illustrating the relationship between the electrode potential and the current designation voltage (that is, the relationship between the electrode potential and the displacement current). A square dot indicates a combination (discrete relationship) of a current designation voltage and an electrode potential obtained by keeping the distance between the vibrating electrode 12 and the surface 91 of the sample 9 constant, and a solid line 811 is It is a straight line obtained from a square dot by the least square method, and shows a continuous linear relationship between the electrode potential and the displacement current. Triangular dots indicate combinations of the current designation voltage and electrode potential when the distance between the vibrating electrode 12 and the surface of the sample 9 is smaller than in the case of square dots, and the round dots indicate vibrating electrodes. 12 shows a combination of the specified current voltage and the electrode potential when the distance between the surface 12 of the sample 9 and the surface 91 of the sample 9 is further reduced. A broken line 812 is a straight line derived from a triangular dot, and an alternate long and short dash line 813 is a straight line derived from a round dot. That is, the straight lines 811 to 813 indicate three relationships between the electrode potential and the displacement current corresponding to the three values of the distance between the vibrating electrode 12 and the surface 91 of the sample 9.

  As shown by the straight lines 811 to 813 in FIG. 3, the relationship between the electrode potential and the displacement current is linear, and the inclination increases as the distance between the vibrating electrode 12 and the surface 91 of the sample 9 increases. As described above, in the surface potential meter 1, the distance between the vibrating electrode 12 and the surface 91 of the sample 9 is a measurement condition for changing the relationship between the electrode potential and the displacement current, and the lifting mechanism 14 (that is, The measurement condition is changed by the measurement condition changing mechanism), and the acquisition of the relationship between the electrode potential and the displacement current is repeated.

  The straight lines 811 to 813 shown in FIG. 3 intersect at one point 814, and another straight line when the distance between the vibrating electrode 12 and the surface 91 of the sample 9 is further changed also passes through the point 814. As described above, since the point 814 does not depend on the distance between the vibrating electrode 12 and the surface 91 of the sample 9, the displacement current due to the change in capacitance between the vibrating electrode 12 and the sample 9 is actually detected at the point 814. It is thought that this did not occur. That is, at the point 814, the displacement from the conductive surface 111 is caused by various factors such as the shape of the vibrating electrode 12, noise generated in the circuit, and a change in the circuit due to the contact state between the sample 9 and the conductive surface 111 of the sample holder 11. Although the current does not become 0, it is considered that the displacement current does not include an alternating current generated due to a change in capacitance between the vibrating electrode 12 and the sample 9.

  In the surface potential meter 1, based on a plurality of discrete relationships between the electrode potential and the displacement current acquired by the steps shown in steps S <b> 15 to S <b> 18 and S <b> 181 described above, Straight lines 811 to 813 indicating a plurality of continuous relationships between electrode potentials and displacement currents corresponding to a plurality of distances (that is, a plurality of measurement conditions) are obtained, and further, intersection points 814 of the plurality of straight lines 811 to 813 are obtained. A combination of an electrode potential and a displacement current (indicating current designation voltage) independent of the distance between the vibrating electrode 12 shown and the surface 91 of the sample 9 is required. Then, the electrode potential and displacement current of the combination are stored in the computer 3 as the reference potential Vs and the reference current is (step S19).

  In the surface electrometer 1, as described above, since it is considered that a displacement current due to a change in capacitance between the vibrating electrode 12 and the sample 9 does not actually occur at the point 814 in FIG. It can be estimated that there is no potential difference between the vibrating electrode 12 having Vs and the first measurement point of the sample 9 facing the vibrating electrode 12. Accordingly, since it can be estimated that the surface potential of the sample 9 at the first measurement point facing the vibrating electrode 12 is equal to the reference potential Vs, in the computer 3, the reference potential Vs is the surface potential of the sample 9 at the first measurement point. (Step S20). In the surface potential meter 1, since the accurate electrode potential is directly acquired by the processing unit 2 and sent to the computer 3, the accuracy of the required reference potential Vs and reference current is and the measurement of the surface potential of the sample 9 are measured. Accuracy can be improved.

  4 is a diagram showing another example of processing for obtaining the reference potential Vs and the reference current is in the surface electrometer 1. FIG. An example in which the reference potential Vs is not included in the change range of the electrode potential in steps S15 to S17 in A (that is, the change range of the electrode potential corresponding to the change range of the displacement current specified by the current designation voltage) is shown. Yes. Similar to the case of FIG. 3, straight lines 821, 822 and 823 in FIG. 4 indicate a plurality of continuous potentials of the electrode potential and the displacement current obtained by changing the distance between the vibrating electrode 12 and the sample 9. These lines show a relationship, and these straight lines intersect at a point 824. As described above, even when the absolute value of the reference potential Vs is relatively large, as shown in FIG. 4, the intersections of a plurality of straight lines 821 to 823 indicating a plurality of continuous relationships between the electrode potential and the displacement current. By obtaining 824, the reference potential Vs and the reference current is can be obtained as the electrode potential and displacement current at the intersection 824, and the surface potential can also be measured.

  When the surface potential at the first measurement point is acquired, the moving mechanism 16 is controlled by the control unit 4 so that the sample 9 moves horizontally with the sample holding unit 11 (that is, parallel to the surface 91 of the sample 9). Then, the vibrating electrode 12 faces the second measurement point (that is, other measurement points included in the plurality of measurement points set on the surface 91 of the sample 9) in a non-contact manner (step S21). In the surface potential meter 1, the measurement of the surface potential at the second and subsequent measurement points is performed using the reference current is obtained at the first measurement point.

  FIG. 5 shows the relationship between the vibrating electrode and the surface of the sample obtained by the same steps as in steps S15 to S18, S181, and S19 described above at each of a plurality (593 points) of measurement points set on the surface of the sample. It is a figure which shows the displacement current (namely, it is a current corresponding to the reference current is calculated | required in step S19, and only hereafter is referred to as a "reference current") for reference, without depending on the distance between them. The horizontal axis in FIG. 5 indicates the number assigned to the measurement point, and the vertical axis indicates the reference current at each measurement point. As shown in FIG. 5, since the reference currents at a plurality of measurement points on the surface of the sample are almost equal, the reference current obtained at one measurement point can be used as the reference current at each measurement point. it can.

  When the vibrating electrode 12 shown in FIG. 1 faces the second measurement point, a current designation voltage corresponding to the reference current is is input from the computer 3 to the control circuit 25 (step S22). Thereby, the electrode potential of the vibrating electrode 12 is changed by feedback control so that the displacement current from the sample holder 11 becomes equal to the reference current is. As described above, when the displacement current from the sample holder 11 is equal to the reference current is, the displacement current due to the change in capacitance between the vibrating electrode 12 and the sample 9 does not actually occur, and the vibrating electrode It can be estimated that there is no potential difference between 12 and the measurement point of the sample 9 facing the vibration electrode 12. Therefore, the electrode potential of the vibrating electrode 12 finally obtained by the feedback control (that is, the electrode potential when the displacement current becomes equal to the reference current is) is calculated by the computer 3 on the sample 9 at the second measurement point. It is acquired and output as a surface potential (step S23).

  When the surface potential at the second measurement point is acquired, it is confirmed whether or not there is a next measurement point (step S24). If there is a next measurement point, the sample 9 moves and the vibrating electrode 12 moves. Opposes the next measurement point in a non-contact manner (step S25). Then, the electrode potential of the vibrating electrode 12 is controlled by feedback control so that the displacement current from the sample holding unit 11 becomes equal to the reference current is (that is, the value indicated by the current designation voltage input to the control circuit 25 in step S22). The electrode potential when the displacement current is changed and becomes equal to the reference current is is acquired and output as the surface potential of the sample 9 (step S26).

  Subsequently, returning to step S24, it is confirmed whether or not there is a next measurement point (step S24). If there is a next measurement point, the movement of the sample 9 and the acquisition of the surface potential (as described above) After steps S25 and S26) are performed, the process returns to step S24 again. In the surface potential meter 1, steps S <b> 24 to S <b> 26 are repeated until the measurement of the surface potential for all of the plurality of measurement points set on the surface 91 of the sample 9 is completed (that is, for the measurement points not yet measured). Steps S24 to S26 are sequentially performed).

  As described above, in the surface electrometer 1, the distance between the vibrating electrode 12 and the surface 91 of the sample 9 is set at the first measurement point among the plurality of measurement points set on the surface 91 of the sample 9. A reference current is, which is a displacement current from the sample holder 11 that does not depend, is obtained. Then, as shown in steps S21 to S23, the surface potential at the second measurement point uses the reference current is to input the current designation voltage input to the control circuit 25 and the surface 91 of the vibrating electrode 12 and the sample 9. Is quickly measured without changing the distance between the first electrode and the second electrode, and is obtained with high accuracy without depending on the distance between the vibrating electrode 12 and the surface 91 of the sample 9. As a result, measurement of the surface potential at a plurality of measurement points set on the surface 91 of the sample 9 can be performed quickly and with high accuracy based on the electrode potential and the displacement current.

  In the surface potential meter 1, the surface potentials at all the third and subsequent measurement points on the surface 91 of the sample 9 are obtained quickly and with high accuracy using the reference current is as shown in steps S24 to S26. It is done. Thereby, the surface potential at a plurality of measurement points set on the surface 91 of the sample 9 can be measured more quickly.

  As described above, in the surface potential meter 1, the vibration electrode 12 facing the surface 91 of the sample 9 is vibrated, and the displacement current from the conductive surface 111 of the sample holder 11 that holds the sample 9 and the electrode potential of the vibration electrode 12 are detected. The surface potential is determined based on As a result, it is possible to measure the surface potential with high accuracy while suppressing the influence of stray capacitance between the vibrating electrode 12 and the surrounding cover 151 and the like (that is, noise components due to stray capacitance).

  Further, in the acquisition of the reference potential Vs and the reference current is in steps S15 to S18, S181, and S19, the distance between the vibrating electrode 12 and the surface 91 of the sample 9 changes the relationship between the electrode potential and the displacement current. It is a condition. Thereby, the measurement conditions can be easily changed mechanically, and as a result, acquisition of the reference potential Vs and the reference current is can be facilitated.

  In the surface potential meter 1, the surface potential of a plurality of samples 9 is usually measured sequentially, and FIG. A and FIG. Steps S11 to S18, S181, and S19 to S26 shown in B are sequentially performed on the plurality of samples 9. As described above, the reference current is is almost constant on the surface of one sample, but the circuit changes due to the contact state between the sample and the conductive surface 111 of the sample holder 11, the change in the surface state of the sample, etc. Due to factors, multiple samples may differ from each other. Therefore, by acquiring the reference current is at the first measurement point (step S19) in each of the plurality of samples, the surface potential of the plurality of samples can be measured quickly and with high accuracy.

  Further, in the surface potential meter 1, when the surface potential measurement is performed again for the sample 9 carried out from the surface potential meter 1 after the surface potential measurement, even if it is the same sample 9, It is preferable that the reference current is is acquired again in steps S11 to S18, S181, and S19 with respect to the sample 9 that has been carried in again, and the surface potential is remeasured using the new reference current is. Thereby, the influence of the change of the circuit, etc. due to the contact state between the sample 9 and the conductive surface 111 of the sample holder 11 can be eliminated, and the surface potential of the sample 9 can be measured with high accuracy for the second time.

  Next, a second method for measuring the surface potential with the surface potential meter 1 will be described. FIG. A and FIG. B is a diagram showing a part of the flow of surface potential measurement by the second measurement method. In the second measurement method, FIG. After the same steps as steps S11 to S18 and S181 shown in A are performed, FIG. A and FIG. Steps S31 to S37, S371, and S38 shown in FIG. Steps S20 to S26 shown in B are performed. In addition, FIG. In FIG. 2A, in order to facilitate understanding of the figure, FIG. Steps S18 and S181 shown in FIG.

  In the second measurement method, first, the sample 9 held by the sample holder 11 moves in the horizontal direction so that the vibrating electrode 12 faces the first measurement point in a non-contact manner, and then the vibrating electrode 12 and the sample 9 are moved. The distance from the surface 91 is set to a predetermined value, and the vibration electrode 12 starts to vibrate in the vibration direction (steps S11 to S14). Subsequently, the current designation voltage is input to the control circuit 25, the electrode potential is changed by feedback control, and one combination of the electrode potential and the displacement current is acquired (steps S15 and S16). Then, the process returns to step S15 (step S17), and the current designation voltage is changed and the electrode potential is acquired a plurality of times, thereby acquiring the relationship between the electrode potential and the displacement current (steps S15 to S17).

  When the relationship between the electrode potential and the displacement current is acquired, the distance between the vibrating electrode 12 and the surface 91 of the sample 9 is changed by a predetermined size (steps S18 and S181), and then the process returns to step S15. Then, the change of the current designation voltage and the acquisition of the electrode potential are repeated a plurality of times, and the relationship between the electrode potential and the displacement current is acquired again (steps S15 to S17). Then, the change of the distance between the vibrating electrode 12 and the surface 91 of the sample 9 and the acquisition of the relationship between the electrode potential and the displacement current are repeated a predetermined number of times, whereby a plurality of discrete values of the electrode potential and the displacement current are obtained. Are acquired (steps S15 to S18, S181).

  In the second measurement method, when a plurality of discrete relationships between the electrode potential and the displacement current are obtained, a plurality of distances between the vibrating electrode 12 and the surface 91 of the sample 9 (that is, based on the relationship) A straight line (see FIGS. 3 and 4) indicating a plurality of continuous relationships between the electrode potential and the displacement current corresponding to a plurality of measurement conditions) is obtained, and further, an intersection of the plurality of straight lines (see FIGS. 3 and 4). A temporary combination of the electrode potential and the displacement current that does not depend on the distance between the vibrating electrode 12 and the surface 91 of the sample 9 is obtained (step S31). Hereinafter, the electrode potential and displacement current of the temporary combination are referred to as “temporary reference potential” and “temporary reference current”, respectively.

  Next, the temporary reference potential is shown in FIG. It is determined whether or not it is included in the change range of the electrode potential in steps S15 to S17 in A (that is, the change range of the electrode potential corresponding to the change range of the displacement current specified by the current designation voltage) (step S32). . When the temporary reference potential is included in the change range of the electrode potential (that is, as shown in FIG. 3, the electrode potential at the intersection 814 of the plurality of straight lines 811 to 813 is the current specified voltage and the electrode potential related to each straight line. And the temporary reference potential and the temporary reference current are stored in the computer 3 as the reference potential Vs and the reference current is, respectively (step S33). Similarly to the first measurement method, steps S20 to S26 are performed.

  On the other hand, when the temporary reference potential is outside the change range of the electrode potential in steps S15 to S17 (that is, as shown in FIG. 4, the electrode potential at the intersection 824 of the plurality of straight lines 821 to 823 is the current designation related to each straight line. When the dot electrode potential is smaller than the minimum value or larger than the maximum value, the computer 3 designates a temporary reference current or a value near the temporary reference current to the control circuit 25. A current designation voltage to be input is input (step S34). Then, similarly to step S16, the electrode potential is changed by feedback control, and one combination of the temporary reference potential and the electrode potential near the temporary reference current and the displacement current is acquired (step S35). Subsequently, the process returns to step S34 (step S36). Similar to steps S15 to S17, the electrode potential is changed while changing the current designation voltage so that the electrode potential corresponding to the current designation voltage is changed within the range including the temporary reference potential. The step of acquiring the potential is performed a predetermined number of times, thereby acquiring the relationship between the electrode potential and the displacement current (steps S34 to S36).

  When the relationship between the electrode potential and the displacement current is acquired, the distance between the vibrating electrode 12 and the surface 91 of the sample 9 (that is, the measurement condition) is changed by a predetermined magnitude as in steps S18 and S181. After that (steps S37 and S371), the process returns to step S34 to acquire the electrode potential while changing the current designation voltage so that the electrode potential corresponding to the current designation voltage is changed within a range including the temporary reference potential. Is repeated a plurality of times, and the relationship between the electrode potential and the displacement current is acquired again (steps S34 to S36). In the second measurement method, the change of the distance between the vibrating electrode 12 and the surface 91 of the sample 9 and the acquisition of the relationship between the electrode potential and the displacement current are repeated a predetermined number of times, so that steps S15 to S18, Similar to S181, a plurality of discrete relationships between the electrode potential and the displacement current are acquired (steps S34 to S37, S371).

  In the surface potential meter 1, as shown in FIG. 7, the vibrating electrode 12 and the sample are based on the plurality of discrete relationships between the electrode potential and the displacement current acquired by the steps shown in steps S 34 to S 37 and S 371 described above. The straight lines 831 to 833 indicating a plurality of continuous relationships between the electrode potential and the displacement current corresponding to the plurality of distances between the nine surfaces 91 are obtained. An intersection 834 of a plurality of straight lines 831 to 833 is within the dot distribution range indicating the combination of the current designation voltage and the electrode potential related to each straight line (that is, within the change range of the electrode potential in steps S34 to S36). The combination of the obtained electrode potential and displacement current indicated by the intersection 834 is stored in the computer 3 as the reference potential Vs and the reference current is independent of the distance between the vibrating electrode 12 and the surface 91 of the sample 9 (step S38).

  When the reference potential Vs and the reference current is are obtained, the reference potential Vs is output as the surface potential of the sample 9 at the first measurement point, and the sample 9 moves so that the vibrating electrode 12 is not in contact with the second measurement point. The electrode potential when the displacement current from the sample holding unit 11 is equal to the reference current is is acquired and output as the surface potential of the sample 9 at the second measurement point (steps S20 to S23). Thereafter, until the measurement of the surface potential for all of the plurality of measurement points set on the surface 91 of the sample 9 is completed, the sample 9 is moved so that the vibrating electrode 12 faces the next measurement point, and the displacement current becomes the reference The process of acquiring the electrode potential when it becomes equal to the current is as the surface potential is repeated (steps S24 to S26).

  As described above, in the second measurement method, the reference current is is obtained at the first measurement point among the plurality of measurement points set on the surface 91 of the sample 9, as in the first measurement method. The measurement of the surface potential at the second measurement point is performed quickly and with high accuracy using the reference current is. As a result, the surface potential at a plurality of measurement points set on the surface 91 of the sample 9 can be measured quickly and with high accuracy. In addition, the measurement of the surface potential at all the measurement points except the first measurement point is performed quickly and with high accuracy using the reference current is, so that a plurality of measurement points set on the surface 91 of the sample 9 is obtained. The surface potential can be measured more quickly.

  In the second measurement method, in particular, the reference potential Vs and the reference current is are within the change range of the electrode potential when the relationship between the electrode potential and the displacement current is acquired (steps S15 to S17 or steps S34 to S36). Desired. Therefore, compared to the case where the reference potential Vs is obtained outside the change range of the electrode potential, when obtaining a continuous relationship from the discrete relationship between the electrode potential and the displacement current (that is, between the electrode potential and the displacement current). In the graph indicating the relationship, when calculating a reference potential Vs and a reference current is, even when a slight error exists (when a straight line indicating a continuous relationship is obtained from dots indicating a discrete relationship) It is possible to prevent the error from being enlarged and included, and to obtain the reference potential Vs and the reference current is with high accuracy. As a result, the surface potential at a plurality of measurement points set on the surface 91 of the sample 9 can be measured with higher accuracy.

  When the surface potential measurement of the plurality of samples 9 is sequentially performed by the second measurement method, the acquisition of the reference current is at the first measurement point (step S33 or step S38) is performed for each of the plurality of samples. Thus, the surface potentials of a plurality of samples can be measured quickly and with high accuracy.

  Next, a third method for measuring the surface potential with the surface potential meter 1 will be described. FIG. A and FIG. B is a diagram showing a flow of surface potential measurement by the third measurement method. The third measurement method is substantially the same as the first measurement method described above, and FIG. Step S41 is performed instead of Step S12 shown in FIG. The only difference is that step S42 is performed instead of steps S20 and S21 shown in B.

  In the third measurement method, the sample 9 held by the sample holder 11 moves in the horizontal direction, so that the vibrating electrode 12 is set to one reference point set on the surface 91 of the sample 9 (that is, a plurality of measurement points). It is a point that is not one of the points, for example, it faces the center of the surface 91 of the sample 9 without contact (steps S11 and S41). And FIG. A and FIG. Steps S13 to S18, S181, and S19 shown in B are performed, and the reference potential Vs and the reference current is are obtained at the reference point.

  Subsequently, the vibrating electrode 12 faces the first measurement point among the plurality of measurement points set on the surface 91 of the sample 9 in a non-contact manner (Step S42), and Steps S22 and S23 are performed and the first measurement point is performed. The surface potential of the sample 9 at the measurement point is obtained. Thereafter, steps S24 to S26 are repeated, and the surface potentials at a plurality of measurement points of the sample 9 are sequentially measured.

  In the third measurement method, the reference current is is obtained at one point (reference point) different from the measurement point on the surface 91 of the sample 9, and the surface potential at a plurality of measurement points set on the surface 91 of the sample 9 is obtained. Is measured using the reference current is, as in the first measurement method. As a result, the surface potential at a plurality of measurement points set on the surface 91 of the sample 9 can be measured quickly and with high accuracy. In addition, the surface potential is measured at all the measurement points at a plurality of measurement points set on the surface 91 of the sample 9 by measuring the surface potential quickly and with high accuracy using the reference current is. It can be done more quickly.

  When the surface potential measurement of the plurality of samples 9 is sequentially performed by the third measurement method, the reference current is is acquired at the reference point in each of the plurality of samples, thereby obtaining the surface potential of the plurality of samples. Measurement can be performed quickly and with high accuracy.

  In the surface potential meter 1, the surface potential may be measured by combining the above-described second measurement method with the third measurement method. That is, in the second measurement method, after the temporary reference potential and the temporary reference current are obtained at a reference point different from the measurement point, the reference potential and the reference current may be obtained.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the said embodiment, A various change is possible.

  In the surface potential meter 1, for example, when a known error is included in the value of the electrode potential acquired by the computer 3, the surface potential at the first measurement point in step S <b> 20 of the first and second measurement methods. Is obtained by removing the known error from the reference potential Vs (that is, based on the reference potential Vs). Similarly, in steps S23 and S26, the surface potential of the sample 9 at the measurement point is acquired based on the electrode potential when the displacement current becomes equal to the reference current is.

  The vibrating electrode 12 only needs to vibrate relative to the sample 9 and the sample holding unit 11. For example, the vibrating unit 13 having a piezoelectric actuator is connected to the lower side of the sample holding unit 11, and the vibrating electrode 12 is fixed. The sample holder 11 may vibrate in a state where it is in contact. That is, the vibration unit 13 may be connected to one of the vibration electrode 12 and the sample holding unit 11. In the processing unit 2, the displacement current from the vibration electrode 12 generated by the vibration of the vibration electrode 12 may be acquired by connecting the preamplifier 21 and the amplifier 22 to the vibration electrode 12. In this case, the reference potential Vs and the reference current is are obtained based on the displacement current from the vibrating electrode 12 and the electrode potential of the vibrating electrode 12, and the surface potential of the sample 9 is obtained.

  In the measurement of the surface potential with the surface potential meter 1, FIG. Instead of changing the distance between the vibrating electrode 12 and the surface 91 of the sample 9 in steps S18 and S181 of A, the amplitude of the vibrating electrode 12 is changed as a measurement condition for changing the relationship between the electrode potential and the displacement current. May be. Further, the vibration frequency of the vibrating electrode 12 may be changed as the measurement condition. In these cases, the measurement conditions can be easily changed electrically.

  In the surface electrometer 1, the displacement current is specified by the current designation voltage, and the electrode potential is controlled to be the displacement current designated by the feedback control. A displacement current may be acquired. Although it is preferable that the number of the plurality of straight lines indicating the relationship between the displacement current and the electrode potential used for calculating the reference potential Vs and the reference current is is large, two straight lines under two measurement conditions are obtained on the measurement principle. Only by this, the surface potential of the sample 9 can be obtained. In addition, a straight line under each measurement condition can be obtained from a combination of two electrode potentials and a displacement current. Further, the measurement range of the surface potential of the sample 9 measured by the surface potential meter is not limited to the range shown in FIG. 3 and FIG. 4. For example, the surface potential meter is used for measuring the surface potential of several kV. May be.

  Since the surface electrometer according to the above embodiment has high measurement accuracy, it is suitable for measurement of a semiconductor substrate that requires measurement of a minute surface potential, but the sample 9 to be measured is not limited to a semiconductor substrate, It may be an insulator or a conductor having an insulating film formed on the surface.

It is a figure which shows the structure of the surface electrometer which concerns on one embodiment. It is a figure which shows the flow of a measurement of the surface potential of a sample. It is a figure which shows the flow of a measurement of the surface potential of a sample. It is a figure which shows the relationship between an electrode potential and an electric current designation | designated voltage. It is a figure which shows the relationship between an electrode potential and an electric current designation | designated voltage. It is a figure which shows the reference current in a some measurement point. It is a figure which shows a part of flow of the surface potential measurement by a 2nd measuring method. It is a figure which shows a part of flow of the surface potential measurement by a 2nd measuring method. It is a figure which shows the relationship between an electrode potential and an electric current designation | designated voltage. It is a figure which shows a part of flow of the surface potential measurement by a 3rd measuring method. It is a figure which shows a part of flow of the surface potential measurement by a 3rd measuring method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface electrometer 2 Processing part 3 Computer 4 Control part 9 Sample 11 Sample holding part 12 Vibrating electrode 13 Vibrating part 16 Movement mechanism 91 Surface S11-S26, S31-S38, S41, S42, S181, S371 Step

Claims (8)

A surface potential measurement method for measuring a surface potential of a sample,
a) a step of holding a flat sample in the sample holder;
b) a step of contacting the electrode in a non-contact manner to one measurement point included in a plurality of measurement points set on the surface of the sample;
c) causing the electrode to vibrate relative to the sample in a vibration direction from the electrode toward the sample holding unit by a piezoelectric element of a vibrating unit connected to one of the electrode and the sample holding unit; Obtaining the relationship between the electrode potential and the displacement current from the electrode or the sample holder while changing the electrode potential;
d) changing the measurement conditions for changing the relationship between the electrode potential and the displacement current and repeating the step c);
e) Combination of electrode potential and displacement current independent of the plurality of measurement conditions from a plurality of relations between electrode potentials and displacement currents corresponding to the plurality of measurement conditions acquired in the steps c) and d) And storing the displacement current of the combination as a reference current;
f) obtaining a surface potential at the one measurement point based on the combined electrode potential;
g) moving the electrode parallel to the surface of the sample to oppose other measurement points included in the plurality of measurement points;
h) changing the electrode potential of the electrode, and obtaining the surface potential at the other measurement point based on the electrode potential when the displacement current from the electrode or the sample holder becomes equal to the reference current; ,
A surface potential measuring method comprising: The surface potential measurement method according to claim 1,
The method of measuring surface potential, wherein the step g) and the step h) are repeated until the measurement for all of the plurality of measurement points is completed. A surface potential measurement method for measuring a surface potential of a sample,
a) a step of holding a flat sample in the sample holder;
b) making the electrode face the surface of the sample in a non-contact manner;
c) causing the electrode to vibrate relative to the sample in a vibration direction from the electrode toward the sample holding unit by a piezoelectric element of a vibrating unit connected to one of the electrode and the sample holding unit; Obtaining the relationship between the electrode potential of the electrode and the displacement current from the electrode or the sample holder while changing the electrode potential;
d) changing the measurement conditions for changing the relationship between the electrode potential and the displacement current and repeating the step c);
e) Combination of electrode potential and displacement current independent of the plurality of measurement conditions from a plurality of relations between electrode potential and displacement current corresponding to the plurality of measurement conditions obtained in the steps c) and d) And storing the displacement current of the combination as a reference current;
f) moving the electrode in parallel to the surface of the sample to oppose the electrode to one measurement point included in a plurality of measurement points on the surface;
g) changing the electrode potential of the electrode, and obtaining the surface potential at the one measurement point based on the electrode potential when the displacement current from the electrode or the sample holder becomes equal to the reference current; ,
h) repeating the step f) and the step g) for other measurement points included in the plurality of measurement points;
A surface potential measuring method comprising: A surface potential measuring method according to any one of claims 1 to 3,
Step e)
e1) obtaining a temporary combination of electrode potential and displacement current independent of the plurality of measurement conditions from the plurality of relationships between the electrode potential and displacement current corresponding to the plurality of measurement conditions;
e2) When the electrode potential of the temporary combination is included in the change range of the electrode potential in the step c) and the step d), the temporary potential does not depend on the plurality of measurement conditions and the displacement current When the electrode potential of the temporary combination is outside the range of change in the electrode potential in the step c) and the step d), the electrode potential of the electrode is changed to the electrode potential of the temporary combination. The relationship between the electrode potential and the displacement current corresponding to a plurality of measurement conditions is obtained again by performing the step c) and the step d) while changing within the range to include, and the electrode potential and the displacement current obtained again. Obtaining the combination of electrode potential and displacement current that does not depend on the plurality of measurement conditions from the plurality of relationships;
A surface potential measuring method comprising: The surface potential measurement method according to any one of claims 1 to 4,
The surface potential measurement method, wherein the displacement current is acquired from the sample holder. The surface potential measuring method according to any one of claims 1 to 5,
In the step d), the surface potential measuring method is characterized in that the distance between the electrode and the surface of the sample is changed as the measurement condition. The surface potential measuring method according to any one of claims 1 to 6,
The method of measuring a surface potential, wherein the steps a) to h) are sequentially performed on a plurality of samples. A surface potentiometer for measuring the surface potential of a sample,
A sample holder for holding a flat sample;
An electrode facing the surface of the sample without contact;
A vibrating unit that vibrates the electrode relative to the sample in a vibrating direction from the electrode toward the sample holding unit by a piezoelectric element;
A processing unit for obtaining an electrode potential of the electrode when the electrode is relatively vibrated and a displacement current from the electrode or the sample holding unit;
A surface potential calculator for determining the surface potential of the sample based on the electrode potential and the displacement current;
A moving mechanism for moving the electrode relative to the sample parallel to the surface of the sample;
A control unit that measures surface potentials at a plurality of measurement points set on the surface of the sample by controlling the vibration unit, the processing unit, the surface potential calculation unit, and the moving mechanism;
With
The control unit is
b) a step of causing an electrode to contact non-contact with one measurement point included in the plurality of measurement points set on the surface of the sample;
c) The piezoelectric element of the vibration unit connected to one of the electrode and the sample holding unit is vibrated relatively in the vibration direction with respect to the sample while changing the electrode potential of the electrode. Obtaining a relationship between an electrode potential and a displacement current from the electrode or the sample holder;
d) changing the measurement conditions for changing the relationship between the electrode potential and the displacement current and repeating the step c);
e) From the plurality of relationships between the electrode potential and the displacement current corresponding to the plurality of measurement conditions acquired in the step c) and the step d), the relationship between the electrode potential and the displacement current independent of the plurality of measurement conditions. Obtaining a combination and storing the displacement current of the combination as a reference current;
f) obtaining a surface potential at the one measurement point based on the combined electrode potential;
g) moving the electrode parallel to the surface of the sample to oppose other measurement points included in the plurality of measurement points;
h) changing the electrode potential of the electrode, and obtaining the surface potential at the other measurement point based on the electrode potential when the displacement current from the electrode or the sample holder becomes equal to the reference current; ,
A surface electrometer characterized by performing the following.

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