JP6564494B1 - Surface resistance measuring method and surface resistance measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a surface resistance on a lower resistance side irrespective of a response speed of a charge detection device (surface potential meter). The resistance measurement value is not changed depending on the size of the object to be measured. A surface resistance measurement method includes forming a charged region in a partial region of a measured object, and forming a static eliminating region locally in a portion of the measured object that is different from the charged region. In this method, the movement of the charge formed from the charge region to the charge removal region or the potential generated thereby is detected by a charge detection device that is not in contact with the object to be measured. The surface resistance measuring device includes a charging device that forms a charged region in a partial region of the object to be measured, and a neutralization region that is a part of the measured object and is different from the charged region. Equipped with a charge removal device and a charge detection device capable of detecting the surface potential of the object to be measured, these devices are arranged in non-contact with the object to be measured. It is a device capable of detecting a potential. [Selection] Figure 1

Description

  The present invention relates to a method and apparatus for measuring the surface resistance of an object (measurement object) such as a semiconductor or an insulator without contacting the measurement object.

As one of methods for measuring the surface resistance of an object to be measured, there is a method described in Patent Document 1 or Non-Patent Document 1. In this method, a part of the object to be measured is charged to a predetermined potential, and the surface resistance is measured from the amount of charge moving or the moving speed outside the charged region. The potential measured by the surface potentiometer increases with the lapse of time from the start of charging, and eventually becomes the same as or lower than the potential of the charged region. The time from the start of charging until reaching a predetermined potential is shortened as the surface resistance is reduced, and the surface resistance can be estimated by measuring the time. This is the only method that can measure the surface resistance of the high resistance region from 10 ¹⁰ Ω (semiconductor) to 10 ¹⁵ Ω (insulator) in a non-contact manner.

However, in the above conventional method, since the measurement limit of the low-resistance is determined by the response speed of the surface potential meter to capture an increase in potential, such as the surface potential in a shorter time than the response speed is changed, 10 ¹⁰ It was impossible to measure a resistance region smaller than Ω. In addition, in the case of a measurement object having a low resistance that causes the surface potential to rise rapidly, the influence of capacitive coupling between the surface of the measurement object and the surrounding ground cannot be ignored, and the size of the measurement object is reduced. There is a problem that the measurement result of the surface resistance changes only by changing.

Japanese Patent No. 5510629

T. Sugimoto, K. Taguchi, “Non-contact surface thermally measurement for materials greater than 109Ω” Journal of Physics, Conference Series 646 (2015) 012041 doi: 10.1088 / 1742-6596 / 646/1/012041

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface resistance measurement method and a measurement apparatus capable of measuring the surface resistivity on the lower resistance side regardless of the response speed of a measuring instrument such as a surface electrometer or a charge detection device. It is in. Another object of the present invention is to provide a surface resistance measuring method and a measuring device for which the resistance measurement value does not change depending on the size of the object to be measured.

  According to the surface resistance measuring method of the present invention, a part of the surface of the object to be measured is charged to a predetermined potential to form a charged area, and the part of the surface of the object to be measured is different from the charged area. The area (area away from the charged area) is locally neutralized to form a neutralization area, and the charge detected in the charged area is detected by a charge detection device between the two areas and the measured charge is detected. This is a method for measuring the surface resistance of an object.

  The surface resistance measuring device of the present invention comprises a charging device for charging a part of the surface of the object to be measured to a predetermined potential, a part of the surface of the object to be measured, and a region different from the charging region. It is an apparatus provided with a static elimination device that locally eliminates static electricity and a charge detection device that detects charges moving from the charging area to the static elimination area. The charge detection device is disposed in a non-contact manner between the two regions. It is also possible to provide a distance sensor that can detect the distance (interval) between the surface of the object to be measured and the charge detection device, and a correction circuit that can cancel the measurement value error caused by the detected fluctuation. The charging device and the charge removal device may be an interlocking type that operates in an interlocked manner, or a switching type that can be switched to only one of the operations.

The surface resistance measuring method of the present invention has the following effects.
(1) A steady charge flow is formed from the charge region to the charge removal region, and the resulting surface potential does not change with time and becomes a constant value. Therefore, the surface resistance value is maintained regardless of the response speed of the charge detection device. The dependent surface potential can be measured.
(2) Since the flow of electric charge is steady, it is not affected by capacitive coupling between the object to be measured and the surrounding ground, and the measurement result does not change depending on the size of the object to be measured.
(3) Since the charge moving from the charge area to the charge removal area is measured between the two areas, measurement is possible even when the object to be measured moves, and in various lines such as the production line and inspection line of the object to be measured. Measurement is also possible.
(4) Even if the distance between the surface of the object to be measured and the charge detection device varies, the measurement value error caused by the variation can be corrected (cancelled), so that accurate measurement can be performed.

The surface resistance measuring device of the present invention has the following effects.
(1) Since a charge flow region and a charge removal region can be created to create a steady flow of electric charge between the two regions, the surface potential generated by the flow does not change with time and becomes a constant value. For this reason, it becomes possible to measure the surface potential depending on the surface resistance value regardless of the response speed of the charge detection device. In addition, since the electric charge flow can be made steady, it is not affected by capacitive coupling between the object to be measured and the surrounding ground, and the measurement result does not change depending on the size of the object to be measured. .
(2) When a distance sensor and a correction circuit capable of detecting the distance between the surface of the object to be measured and the charge detection device are provided, high accuracy that is not affected by the distance variation between the surface of the object to be measured and the charge detection device Can be measured.
(3) When the charging device and the charge removal device are switched, both devices can be used together or individually and can be used for various purposes.

The conceptual diagram which shows an example of the surface resistance measuring apparatus of this invention. The equivalent circuit explaining the measurement principle of this invention. The conceptual diagram which shows an example of the surface resistance measuring method of this invention. FIG. 3 is an experimental diagram of the surface resistance measurement method of the present invention. The relationship figure of the surface potential calculated by substituting the value which can be estimated from an experimental parameter in Formula (1) of embodiment, and the measured surface potential. FIG. 3 is a relationship diagram between the surface resistivity when the equivalent resistances R _c and R _b in FIG. 2 are changed and the surface potential measured by the surface resistance measurement method of the present invention.

(Embodiment of surface resistance measurement method)
In the surface resistance measuring method of the present invention, a part of the surface of one object to be measured is charged to a predetermined potential to form a charged area, which is a part of the surface of the object to be measured and separate from the charged area. This region (region away from the charged region) is locally neutralized to form a neutralization region, and a charge movement path from the charged region to the neutralization region is formed between the two regions. This is a method of detecting a potential generated by velocity or charge transfer.

  In the surface resistance measurement method, a charging region is formed by a charging device, a discharging region is formed by a discharging device, and a movement path is formed between both regions. The charge moving speed or the electric potential generated by the movement of the charge moving along the moving path is measured by the charge detecting device. In this case, all of the charging device, the charge eliminating device, and the charge detecting device are arranged in a non-contact manner away from the object to be measured. A corona charging electrode is used as the charging electrode of the charging device, a positive voltage is applied to the electrode, and positive ions are supplied to the surface of the object to be measured using corona discharge from the corona charging electrode. Then, a charged region is formed on a part of the surface. A corona charging electrode is also used as the discharging electrode of the discharging device, a negative polarity (reverse polarity to charging) voltage is applied to the electrode, and the corona discharge from the corona charging electrode is used for the measurement object. A neutralization region is formed on another part of the surface. At this time, the electric potential (surface potential of the object to be measured) generated by the movement of the charge along the movement path is measured with a surface potentiometer. The measurement is performed at an arbitrary sampling period, and the average value can be set as the surface potential. The voltage applied to the charging Rona charging electrode and the voltage applied to the discharging corona charging electrode may have opposite polarities.

  The object to be measured may be stationary or moving. It is desirable to keep the distance (interval) between the surface of the object to be measured and the charge detection device constant in both the stationary state and the moving state. It is also possible to detect and cancel (correct) the measurement value error caused by the detected fluctuation.

  The surface resistance measuring method of the present invention can be measured using the surface resistance measuring device of the present invention described below, but can also be measured using other devices. When the surface resistance measuring device of the present invention is used, it can be measured by an experimental preparation and an experimental method described in the following embodiment.

(Embodiment of surface resistance measuring device)
An example of the surface resistance measuring apparatus of the present invention is shown in FIG. The surface resistance measuring device 1 in FIG. 1 is arranged in a straight line in the order of the charging device 11, the charge detecting device 12, and the static eliminating device 13, and is in non-contact with a certain distance from the object to be measured 2. The charging device 11 is a device that forms the charging region 21 so that a part (region) of the DUT 2 has a constant voltage. The neutralization device 13 is a device that forms a static elimination region 23 by locally neutralizing a region other than the charged region in the DUT 2. The charge detection device 12 is a device that measures the movement of charge flowing into the intermediate region 22 connecting the charging region 21 and the charge removal region 23 or the potential generated thereby. Since the commercially available charge detection device 12 is represented by a surface electrometer, in this embodiment, a surface electrometer will be described as an example.

[Charging device]
The charging device 11 supplies charges having positive or negative ions to a part of the surface of the object to be measured 2 to generate a charged region 21 on a part of the surface of the object to be measured 2. Charges are supplied so as to maintain a constant potential. The charging device 11 is generally configured to supply positive ions to the surface of an object to be measured using corona discharge generated from a needle-like electrode (charging electrode) 11a (FIG. 3) to which a high voltage is applied. However, a configuration in which a radioactive substance is embedded at the tip of an electrode to which a voltage is applied may be used. Any configuration may be used as long as the charge is supplied from the electrode to which the voltage is applied so as to keep the charging region 21 at a constant potential.

[Staticizer]
The static eliminator 13 forms a static elimination region 23 at a part of the surface of the object to be measured (the object to be measured forming the charging region) 2 and does not overlap the charging region 21. A charge having a polarity opposite to the applied charge is applied to a part of the surface of the DUT 2 so that the potential of the charge removal region 23 becomes zero (including almost zero). Similar to the charging device 21, a device that uses corona discharge is generally used. For example, the charging device 21 includes a needle-like electrode (discharge electrode) 13 a (FIG. 3) and a ground electrode (grid electrode) 13 b (FIG. 3). is there. If possible, other methods such as radiation may be used for the static eliminator in the present invention.

[Surface potential meter]
The surface potential meter 12 measures the potential (charge) in the intermediate region 22 between the charging region 21 and the charge removal region 23. The measured potential is a value depending on the surface resistance of the DUT 2 for the following reason. Therefore, the surface potential of the device under test 2 whose surface resistance is already known is measured in advance, and separately from this measurement, the surface potential of the device under test 2 to be measured is measured, and the measured potential is the said known potential. It becomes possible to convert based on the surface resistance.

[Measurement principle]
FIG. 2 shows an equivalent circuit formed between the surface resistance measuring device 1 and the DUT 2 in FIG. In FIG. 2, V ₊ is a voltage applied to the charging electrode 11a (FIG. 3) serving as a charge supply source of the charging device 11 (FIG. 1), and R _c is the charging electrode 11a and the object 2 to be measured. It is equivalent resistance of the space between the charged region 21 (FIG. 1). R ₁ is the equivalent resistance from the charging region 21 (FIG. 1) to the measurement point of the intermediate region 22 (FIG. 1), and R ₂ is the equivalent resistance from the measurement point to the charge removal region 23 (FIG. 1). _Rb is the equivalent resistance of the space between the charge removal region 23 of the DUT 2 and the ground electrode 13b. In the equivalent circuit, since these equivalent resistances are all connected in series, the surface potential v (FIG. 2) in the intermediate region measured by the surface potential meter 12 (FIG. 1) is given by the following equation.

Surface potential v (FIG. 2) by adjusting the R _c or R _b, be converted into surface resistivity by becomes a value that depends on the surface resistance R ₁ and R ₂ of the object 2, for measuring the surface potential Indicates that this is possible.

[Experiment]
In order to demonstrate the above measurement principle, a prototype as shown in FIG. 3 was manufactured and arranged as shown in FIG. 4 to prepare for the experiment. As the charging device 11, a charging electrode (a fine needle having a tip curvature radius of about 20 μm) 11a connected to a DC positive high voltage power source capable of changing the voltage was used. The gap between the charging electrode 11a and the charging region 21 was set to 5.0 mm. As an example, the distance between the charging region 21 and the charge removal region 23 is about 50 mm. As the charge removal electrode 13, four needle-shaped charge removal electrodes 13a that are the same as the needle of the charging electrode 11a and a grounded grid electrode 13b having a mesh size of 2.0 mm were used. The gap between the static elimination electrode 13a and the ground electrode 13b was 3.0 mm, and the gap between the ground electrode 13b and the static elimination region 23 was 1.0 mm. A surface potential meter (SMC IZD10-110) was used as the charge detection device 12.

  After the preparation for the experiment in FIG. 4 is completed, a positive voltage +3.7 kV is applied to the charging electrode 11a, and positive ions are supplied to the surface of the DUT 2 using the corona discharge generated from the charging electrode 11a. As a result, a charged region 21 (FIG. 4) was formed. At the same time, a negative voltage of -4.3 kV is applied to the static elimination electrode 13a, and a charged region 21 is applied to another part of the surface of the object to be measured 2 by utilizing corona discharge generated from the static elimination electrode 13a. The charge removal region 23 having a potential of zero was formed by applying a charge (negative charge) having a reverse polarity to the charge applied to. The surface potential at this time was measured with the surface potential meter at a sampling period of 0.1 second, and the average value was output. In addition, when the surface resistance was too low and too high, no change was observed in the surface potential even when the charging / discharging operation was performed.

[Measurement object]
As the DUT 2, samples # 1 to # 7 shown in Table 1 were used. Those having a surface resistivity of 10 ⁵ to 10 ¹² Ω were prepared.

[Experimental result]
FIG. 5 shows the surface potential calculated by substituting a value that can be estimated from the experimental parameters into Equation (1) and the actually measured surface potential. The dotted line in FIG. 5 is the calculation result of the formula (1), and the horizontal axis is expressed by the surface resistivity. A square plot is the measurement result. When samples # 5 and # 7 in Table 1 were measured, the surface resistance was too large and the device displayed an error indicating that measurement was not possible. Among the samples in Table 1, the samples other than Samples # 5 and # 7 were within the measurement range, and the surface potential decreased as the surface resistivity decreased. The measured surface potential value almost coincided with the calculation result. Therefore, it was revealed that the resistivity of 10 ⁶ to 10 ¹⁰ Ω can be measured by the surface resistance measuring method of the present invention. It was also confirmed that the measurement results were the same regardless of the size of the object to be measured that was larger than the combined area of the charging region 21, the intermediate region 22, and the charge removal region 23.

In the calculation results shown in FIG. 5, the calculation is performed by substituting the equivalent resistances R _c and R _b with the parameters for which the experiment was performed. R _c and R _b can be adjusted by changing the applied voltage or electrode parameters. Therefore, when R _c and R _b are adjusted, how the measurable region changes is examined using equation (1) and is shown in FIG. It can be seen that the smaller the _Rc and _Rb are set, the more the measurable range (surface resistance range where the change in surface potential is large) is shifted to the low resistance side. Therefore, once the surface potential is measured at a predetermined R _c or R _b , the measurement result is fed back, R _c or R _b is adjusted, and the measurement is performed again. It becomes possible to accurately measure the surface resistivity. The adjustment of _Rc and _Rb can be adjusted by the number of corona discharge electrodes, the distance between the electrodes, or the applied voltage. When using radioactive materials, the radiation dose can be adjusted in addition to them. Any method can be used as long as the equivalent resistance can be adjusted.

  The experiment is performed when the object to be measured 2 is stationary, but the object to be measured 2 in the surface resistance measuring method of the present invention may be moving. It is desirable to keep the distance (interval) between the surface of the object to be measured 2 and the charge detection device 12 constant in both the stationary state and the moving state. It is also possible to detect and to cancel (correct) the measurement error caused by the detected fluctuation by the correction circuit. The correction circuit may be any correction circuit as long as the correction can be performed. When the DUT 2 moves, the moving speed may be within a time until a predetermined charge is charged in the charged region, for example, within 30 cm / sec. For the measurement of the movement speed of the charge moving from the charging area to the charge removal area, for example, the measurement is performed by the charge movement speed measuring device and the charge movement speed measuring method of the patent invention (Patent Document 1) previously developed by the present inventor. Can do.

  The surface resistance measuring device in the experiment has a charging device and a static eliminator separately. However, the surface resistance measuring device of the present invention can be operated so that the charging device and the static eliminator are operated simultaneously or separately. It may be switchable.

  The embodiments of the surface resistance measuring method and the surface resistance measuring device described above are merely examples. Both the measuring method and the measuring apparatus of the present invention can be changed within a range in which the above problem can be solved.

DESCRIPTION OF SYMBOLS 1 (Non-contact type) surface resistance measuring apparatus 2 Object to be measured 11 Charging apparatus 11a Charging electrode 12 Charge detection apparatus (surface potential meter)
13 Static elimination device 13a Electrostatic discharge electrode 13b Ground electrode (grid electrode)
21 Charging area (in the object to be measured) 22 Intermediate area (in the object to be measured) 23 Charge eliminating area (in the object to be measured)

Claims (11)

A method of measuring the surface resistance of an object to be measured with a measuring device that is not in contact with the surface of the object to be measured,
Form a charged area with a predetermined potential in a partial area of the object to be measured,
A static elimination region is locally formed in a part of the object to be measured and different from the charged region,
Detecting the moving speed of the electric charge moving from the charged area to the static eliminating area or the electric potential generated by the movement of the electric charge by a non-contact charge detecting device.
A surface resistance measuring method characterized by the above. In the surface resistance measuring method according to claim 1,
A charging device having a charging electrode is used to form a charging region, and a charge is supplied from the charging electrode to a part of the surface of the object to be measured to form a charging region, and the charge supplied from the charging electrode or Adjust the measurement area of the surface resistance by changing the electrode parameters,
A surface resistance measuring method characterized by the above. In the surface resistance measuring method according to claim 1,
A static eliminator equipped with a static elimination electrode is used to form the static elimination region, and a charge having a polarity opposite to that of the charge for charge is supplied from the static elimination electrode to a part of the surface of the object to be measured. Adjust the measurement area of the surface resistance by changing the charge supplied from the electrode for static elimination or the electrode parameters.
A surface resistance measuring method characterized by the above. In the surface resistance measuring method according to claim 2,
The charging electrode of the charging device is a corona charging electrode, and a corona discharge from the corona charging electrode supplies positive or negative ions to a part of the surface of the object to be measured to form a charged region. By adjusting the corona discharge current flowing through the charging electrode, the surface resistance measurement area can be adjusted.
A surface resistance measuring method characterized by the above. In the surface resistance measuring method according to claim 3,
The static eliminator is equipped with a static elimination electrode and a ground electrode, and the static elimination electrode is a corona charging electrode. By the corona discharge from the corona charging electrode, ions having the opposite polarity to the charge for charging are formed to form a static elimination region. Then, by adjusting the corona discharge current flowing through the corona charging electrode, the measurement area of the surface resistance can be adjusted,
A surface resistance measuring method characterized by the above. In the surface resistance measuring method according to any one of claims 1 to 5,
In advance, the surface potential of the object to be measured whose surface resistance is known is measured, and separately from this measurement, the surface potential of the object to be measured is measured by a charge detection device that is not in contact with the object to be measured. Is calculated based on the known surface resistance to obtain the surface resistance of the object to be measured.
A surface resistance measuring method characterized by the above. In the surface resistance measuring method according to any one of claims 1 to 6,
Forming a charged area and a static elimination area on a stationary object or a moving object;
A surface resistance measuring method characterized by the above. In the surface resistance measuring method according to any one of claims 1 to 7,
Detects a variation in the distance between the surface of the object to be measured and the charge detection device, and corrects a measurement error caused by the detected variation in the distance.
A surface resistance measuring method characterized by the above. A surface resistance measuring device capable of measuring the surface resistance of an object to be measured without contact with the surface of the object to be measured,
A charging device that forms a charged area having a predetermined potential in a partial area of the object to be measured, and a static elimination area that is a part of the object to be measured and is different from the charged area. Equipped with a static elimination device and a charge detection device capable of detecting the surface potential of the object to be measured,
The charging device, the charge removal device, and the charge detection device are arranged in contact with the object to be measured,
The charge detection device is capable of detecting the movement of electric charge flowing from the charged region charged by the charging device to the charge removal region discharged by the charge removal device or a potential generated thereby.
A surface resistance measuring device. In the surface resistance measuring device according to claim 9,
The charging device and the static eliminator can be switched to both operations or only one operation.
A surface resistance measuring device. In the surface resistance measuring device according to claim 9 or 10,
A distance sensor capable of detecting the distance between the surface of the object to be measured and the charge detection device, and a correction circuit capable of canceling a measurement error caused by the amount of displacement detected by the distance sensor,
A surface resistance measuring device.

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