JPH08201463A - Surface charge measuring apparatus - Google Patents

Abstract

PURPOSE: To provide an apparatus for measuring the quantity of charges on the surface of a sample accurately with high resolution regardless of the material of a sample. CONSTITUTION: The surface charge measuring apparatus comprises a conductive probe 2 fixed to a cantilever resilient piece, and a sensor 4 for detecting the displacement of the probe 2 wherein the probe 2 searches the surface of a sample and measures the quantity of charges on the surface. The surface charge measuring apparatus further comprises a mechanism 5 for inching the resilient piece, a memory section 21 for storing the displacement detected by the displacement sensor 4, a section 6 for operating the height of the surface of sample based on the displacement detected by the displacement sensor 4, and a control section 20 for reading out the displacement corresponding to the height of the surface of sample 1 from the memory section 21 based on the operation results from the operating section and presenting the displacement thus read out at a display section 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface charge measuring device for measuring the surface charge of various samples.

[0002]

2. Description of the Related Art Conventionally, as this type of surface charge measuring instrument, the one disclosed in Japanese Patent Laid-Open No. 2732776/1993 is known.

As shown in FIG. 6, the surface charge measuring device disclosed in the above publication includes a probe 101 attached to a surface 100a to be measured of a sample 100 at the tip of a cantilever 102 cantilevered by a holder 111. , The surface to be measured 100a between the probe 101 and Z
The distance in the axial direction is larger than the range of action of the atomic force, and the piezo stage 112 is movably supported so as to be in the range of the Coulomb force, and the amount of bending of the cantilever 102 based on the Coulomb force acting on the probe 101. Based on the measurement result of the non-contact optical displacement measuring system 103 and the non-contact optical displacement measuring system (optical sensor) 103 for measuring the unevenness of the surface to be measured 100a in a non-contact manner. A charge detection unit 113 for measuring the charge amount of the measured surface 100a of the sample 100 based on the amount of deflection detected by the amount detection unit 104 is provided.

The deflection amount detecting means 104 includes a laser power source 121, a laser diode (LD) 122, a beam splitter 123, a condensing lens 124, a photodetector 125, and 1.
26, a diaphragm 127, and the like.

[0005]

By the way, the sample 100 is used.
It is necessary to measure the surface charge amount of the device at a constant height from the surface to be measured 100a. However, in the case of the above-described conventional surface charge measuring instrument, since the height of the surface to be measured 100a is measured by the non-contact optical displacement measuring system 103, a sample sensitive to light such as a selenium-based charged body is measured. If 100,
When the sample 100 is irradiated with light, the amount of surface charge changes, which causes a problem that accurate measurement cannot be performed.

In addition, in this type of surface charge measuring instrument, in the case of the conventional surface charge measuring instrument shown in FIG. The spatial resolution of the non-contact optical displacement measuring system 103 is about several μm, and there is a problem that the spatial resolution is insufficient.

Further, in the case of the conventional surface charge measuring instrument, since the deflection amount detecting means 104 and the non-contact optical displacement measuring system 103 are separated from each other, it is necessary to correct the positions of both measuring portions. However, there is a problem that a measurement error is likely to occur due to the displacement of the measurement site.

An object of the present invention is to solve the above problems and to provide a surface charge measuring device capable of measuring the surface charge amount of a sample with high resolution and high accuracy without being affected by the material of the sample.

[0009]

According to the first aspect of the present invention,
A surface having a conductive probe attached to a cantilever-supported elastic piece and a displacement sensor for detecting the amount of displacement of the probe, and a surface for measuring the surface charge amount by exploring the sample surface with the probe. In the charge measuring device, a fine movement mechanism that finely moves the elastic piece in the height direction, a storage unit that stores the displacement amount detected by the displacement sensor, and the height of the sample surface based on the displacement amount detected by the displacement sensor. It is characterized in that it has a computing unit for computing and a control unit for reading out a displacement amount according to the height of the sample surface from the storage unit based on the computation result of this computing unit and displaying it on the display unit.

According to a second aspect of the present invention, there is provided a conductive probe attached to a cantilever-supported elastic piece, and a displacement sensor for detecting a displacement amount of the probe. In a surface charge measuring device for exploring the surface and measuring the amount of surface charge, a fine movement mechanism for finely moving the elastic piece in the height direction, a setting unit for setting the fine movement of the elastic piece by the fine movement mechanism to a minimum, and this setting. A storage unit that stores a displacement amount detected by the displacement sensor according to the minimum fine movement of the fine movement mechanism based on the setting by the unit, and a calculation unit that calculates the height of the sample surface based on the displacement amount detected by the displacement sensor. And a control unit for reading a displacement amount corresponding to the height of the sample surface from the storage unit based on the calculation result of the calculation unit and displaying the displacement amount on the display unit.

According to a third aspect of the present invention, there is provided a conductive probe mounted on a cantilever-supported elastic piece, and a displacement sensor for detecting a displacement amount of the probe, and the sample is sampled by the probe. In a surface charge measuring device for exploring the surface and measuring the amount of surface charge, a fine movement mechanism for finely moving the elastic piece in the height direction, a setting unit for setting the fine movement of the elastic piece by the fine movement mechanism to a minimum, and the sample. A bias circuit that applies a potential difference between the surface and the probe; a storage unit that stores the amount of displacement detected by the displacement sensor in accordance with the minimum fine movement of the fine movement mechanism based on the setting by the setting unit; A calculation unit for calculating the height of the sample surface based on the displacement amount detected by the displacement sensor and the potential difference by the bias circuit, and a displacement according to the height of the sample surface from the storage unit based on the calculation result of this calculation unit. Read quantity It is characterized in that a control unit to be subjected to the display of the display unit.

[0012]

In the fine movement mechanism of the surface charge measuring instrument according to the first aspect of the present invention, the elastic piece is finely moved in the height direction to displace the probe and the probe is used to probe the surface of the sample. The displacement sensor detects the amount of displacement of the probe in the height direction. The storage unit stores the displacement amount detected by the displacement sensor, and the calculation unit calculates the height of the sample surface based on the displacement amount detected by the displacement sensor. The control unit is
Based on the calculation result of the calculation unit, the displacement amount according to the height of the sample surface is read from the storage unit and provided for display on the display unit. By such an operation, the surface charge amount of the sample can be measured with high resolution and high accuracy without being affected by the sample material.

According to the surface charge measuring device of claim 2,
The position of the probe at the time of measuring the surface charge amount of the sample is obtained by exhibiting the same operation as that of the surface charge measuring device according to claim 1 and setting the operation of the fine movement mechanism to a minimum by the setting unit. The position where the Coulomb force is not affected can be set, and the measurement speed of the surface charge amount of the sample becomes high.

According to the surface charge measuring device of claim 3,
A bias circuit that exerts a function similar to that of the surface charge measuring device according to claim 2 and that provides a potential difference between the sample surface and the probe corresponds to a potential difference by the bias circuit from the sample surface. The surface charge amount of the sample can be measured at a position higher by just that much, which enables more stable measurement.

The present invention will be described in more detail below. In the surface charge measuring device of the present invention, as shown in FIG. 1, one end of a spring member 3 which is an elastic piece is held by a fine movement mechanism 5, and the other end of this spring member 3 supports a conductive probe 2. To do. The sample 1 has a front surface facing the probe 2 and a back surface grounded. The electrostatic force from the sample 1 is converted into the bending amount of the spring member 3, the displacement sensor 4 detects the bending amount, and sends this to the computing unit 6 and the storage unit 21.

Further, the control unit 20 controls the fine movement mechanism 5 so as to change the distance between the probe 2 and the sample 1, and
A change in the output of the calculation unit 6 is detected, and the amount of bending is read from the storage unit 21 and displayed on the display unit 14 based on the control amount of the fine movement mechanism 5 and the output from the displacement sensor 4 at this time. The arithmetic unit 6 is composed of a simple differentiating circuit and a comparator, and sequentially detects the change amount of the output of the displacement sensor 4 and outputs it to the control unit 20.

The measurement of the charge amount on the surface of the sample 1 is influenced by the height L from the surface of the sample 1. Therefore, it is necessary to accurately detect the height L of the surface and measure it at a constant height L. . Therefore,
The fine movement mechanism 5 is operated by the control unit 20 to bring the probe 2 held by the spring member 3 close to the surface of the sample 1. At this time, a Coulomb force acts between the probe 2 and the sample 1 to bend the spring member 3. The displacement of this amount of bending is detected by the displacement sensor 4. FIG. 2 is a displacement curve showing the relationship between the amount of fine movement when the probe 2 is brought close to the surface of the sample 1 and the amount of bending of the spring member 3 at this time. The distance between the probe 2 and the sample 1 becomes narrower by approaching the surface of the sample 1, so that the Coulomb force increases and the amount of bending increases.
When they are brought closer, they collide with the sample 1 at the position of the surface of the sample 1, and thereafter, the sample 1 is displaced by the repulsive force generated from the surface.

The storage unit 21 stores the series of operations in association with the control amount and the deflection amount of the fine movement mechanism 5, and the control unit 20 further stores the fine movement mechanism 5 at the collision position with the surface of the sample 1. Of the sample 1 by reading the control amount and the deflection amount at the collision position, obtaining a measurement point from them, and reading the deflection amount corresponding to the height L of the measurement point from the storage unit 21 on the display unit 14. The amount of charge on the surface of can be measured. The calculation unit 6 has a function of detecting the collision position.

[0019]

Embodiments of the present invention will be described below in detail.

[First Embodiment] (Structure) FIG. 3 shows a surface charge measuring instrument according to a first embodiment of the present invention. This surface charge measuring device includes a base portion 7 formed in a substantially U shape, and a displacement sensor 4 and a fine movement mechanism 5 are provided above the base portion 7.
The Z stage 9 is arranged below the base 7. The Z stage 9 is composed of a cross roller stage and is configured to move the XY stage 8 and the sample 1 slightly in the Z direction while facing the displacement sensor 4.

The XY stage 8 is composed of a tube scanner made of a piezoelectric element or a laminated PZT formed in a tripod shape, and holds the sample 1 on the upper surface so that the sample 1 can be finely moved in the X and Y directions. There is.

One end of the spring member 3 is held by the fine movement mechanism 5, the other end side is made to face above the sample 1, and the probe 2 is held at the other end side of the spring member 3. There is.

The spring member 3 is made of a conductive elastic material such as a thin piece of phosphor bronze having a thickness of several μm to several hundred μm, and the probe 2 is formed by sharpening the diamond tip. Then, in order to make it more conductive, the ion-implanted ion-implanted material is fixed to the spring member 3 with an adhesive or the like.

Further, the probe 2 and the spring member 3 may be formed by a semiconductor manufacturing process, and in order to have conductivity, gold vapor-deposited surface may be used.

The fine movement mechanism 5 comprises a finely movable piezoelectric element. The displacement sensor 4 is a commercially available optical displacement sensor or capacitance displacement sensor, and is arranged at a position where the displacement of the probe 2 can be measured, that is, above the probe 2. The differentiating circuit 12 connected to the displacement sensor 4 is composed of a differentiating circuit or a differential circuit that differentiates the signal from the displacement sensor 4. The drive circuit 11 for driving the XY stage 8 and the drive circuit 13 for driving the fine movement mechanism 5 can be configured by a simple amplifier circuit, and XY is issued by a command from the control means 10.
The stage 8 and the fine movement mechanism 5 are each operated.

The control means 10 operates the drive circuit 11 and the drive circuit 13 by the CPU corresponding to the control section 20 of FIG. 1, and outputs the output of the displacement sensor 4 to the control means 1.
0 is stored in a memory corresponding to the storage unit 21 shown in FIG. 1, and the output signal of the differentiating circuit 12 is taken into an arithmetic circuit corresponding to the arithmetic unit 21 shown in FIG. Based on this, the stored data in the memory is output to the display unit 14 for display.

(Operation) In order to measure the charge on the surface of the sample 1,
The Z stage 9 is operated by the command of the control means 10 to bring the probe 2 close to the sample 1, and the amount of bending of the spring member 3 due to the Coulomb force between the probe 2 and the sample 1 is stored in the memory of the control means 10. This amount of deflection depends not only on the influence of the amount of electric charge on the sample surface but also on the distance between the probe 2 and the sample surface, so it is necessary to accurately detect the position of the sample surface. Therefore, the probe 2
The displacement position of the spring member 3 and the fine movement mechanism 5 at this time are detected by the displacement sensor 4 and the differentiating circuit 12 at the collision position between the and the sample 1.
The position of the sample surface is accurately detected by adding the control amounts of. The differentiating circuit 12 has a function of detecting an output change of the displacement sensor 4 due to the collision of the sample surface and the probe 2, and at the collision point, the differential value of the output of the displacement sensor 4 changes from minus to plus. We are using. An arithmetic circuit mounted on the control means 10 calculates a sample surface position that is more accurate than the collision position of the probe 2, and the control unit reads the data of the bending amount stored earlier than the memory corresponding to the calculation result. Is displayed on the display unit 14. In order to measure the surface charge distribution of the sample 1, it is necessary to detect the charge amount while sequentially moving the sample 1 in the X direction and the Y direction. Therefore, the XY stage 8 is sequentially moved to sequentially detect charges, and the detection result is two-dimensionally displayed on the display unit 14.

(Effect) According to the surface charge measuring device of the present embodiment, the sample surface position can be detected more accurately than the collision position of the sample 1, so that the distribution of the charge amount on the sample surface can be measured with high accuracy.

[Second Embodiment] (Structure) A surface charge measuring device according to a second embodiment of the present invention is shown in FIG.
As shown in FIG. 3, in addition to the structure of the surface charge measuring device of the first embodiment shown in FIG. 3, a setting unit 15 composed of a key switch or a variable resistor is connected to the control means 10.

(Operation) When the operation of the fine movement mechanism 5 is executed many times like the charge distribution measurement on the sample surface to perform the charge measurement, the probe 2 must be pulled up to a position where the Coulomb force does not affect each measurement. No, the measurement speed becomes slow. Therefore, in the surface charge measuring device of the second embodiment, the probe 2 is set by the setting unit 15 with reference to the collision position with the sample surface detected during charge measurement so as to minimize the operation of the fine movement mechanism 5. Is set and the fine movement mechanism 5 is controlled. In this case, the setting unit 15 sets the pull-up amount of the probe 2 to be higher than the charge measurement point.
Other actions are similar to those of the first embodiment.

(Effect) According to the surface charge measuring device of the present embodiment, the fine movement mechanism 5 has a minimum movement, and therefore, there is an advantage that the measurement speed of the charge distribution measurement on the sample surface becomes high.

[Third Embodiment] (Structure) FIG. 5 shows the structure of a surface charge measuring device according to a third embodiment of the present invention. The surface charge measuring device according to the third embodiment has substantially the same structure as the surface charge measuring device according to the second embodiment shown in FIG. 4, except that a bias circuit 17 composed of a constant voltage source circuit is added, and a displacement sensor. The output of 4 is the calculation unit 6 and the control means 1
It is characterized in that it is sent to 0A and that the control means 10A is equipped with a memory.

The bias circuit 17 has one electrode connected to the bottom of the sample 1 and the other electrode connected to the probe 2 via the spring member 3 having conductivity. The calculation unit 6 can be configured by a comparator or the like, and performs a comparison calculation between the output potential of the bias circuit 17 and the output of the displacement sensor 4, and the result is the control means 1.
It is designed to be sent to 0A. The other configuration is the second
It is similar to the embodiment.

(Operation) In the surface charge measuring instrument of the third embodiment, in order to avoid the collision between the sample 1 and the probe 2, the bias circuit 17 gives a potential difference between them. This potential difference becomes a Coulomb force acting between the sample 1 and the probe 2,
The actual collision position of the probe 2 may be lower than the collision position when no potential difference is applied. Therefore, the bias circuit 17 applies a potential difference between the sample 1 and the probe 2, the fine movement mechanism 5 finely moves the probe 2, and the displacement sensor 4 detects the displacement of the probe 2 and the displacement amount of the probe 2. By comparing the potential difference by the bias circuit 17 in the calculation unit 6, the height L of the sample surface can be detected at a position higher than the sample surface by the potential difference. Due to this action, the sample surface position can be apparently detected without lowering the probe to the actual collision position, and a measurement point can be determined with this position as a reference to measure the amount of charge on the sample surface.

(Effect) According to the surface charge measuring instrument of the third embodiment, since the charge amount can be measured without the sample 1 and the probe 2 colliding with each other, the sample surface is not damaged and is not affected by the collision. Since there is no discharge of electric charge, the amount of electric charge on the sample surface can be measured repeatedly in a stable state.

[0036]

According to the first aspect of the present invention, it is possible to provide a surface charge measuring instrument capable of measuring the surface charge amount of this sample with high resolution and accuracy without being affected by the material of the sample.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, it is possible to provide a surface charge measuring instrument capable of increasing the measurement speed of the surface charge amount of the sample. it can.

According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, it is possible to provide a surface charge measuring instrument capable of more stable measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a surface charge measuring device of the present invention.

FIG. 2 is a graph showing a displacement curve showing the relationship between the amount of fine movement by the fine movement mechanism and the amount of bending of the spring member in the surface charge measuring device of the present invention.

FIG. 3 is a block diagram showing the configuration of a first embodiment of the surface charge measuring instrument of the present invention.

FIG. 4 is a block diagram showing a configuration of a second embodiment of the surface charge measuring instrument of the present invention.

FIG. 5 is a block diagram showing the configuration of a third embodiment of the surface charge measuring instrument of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 sample 2 probe 3 spring member 4 displacement sensor 5 fine movement mechanism 6 computing unit 10 control unit 14 display unit 15 setting unit 17 bias circuit 20 control unit 21 storage unit

Claims (3)

[Claims] 1. A surface-charged probe having a conductive probe attached to a cantilever-supported elastic piece and a displacement sensor for detecting the amount of displacement of the probe, the probe surface exploring the sample surface. In a surface charge measuring device for measuring the amount, a fine movement mechanism for finely moving the elastic piece in the height direction, a storage unit for storing the displacement amount detected by the displacement sensor, and a sample based on the displacement amount detected by the displacement sensor. It has a calculation unit for calculating the height of the surface, and a control unit for reading the displacement amount according to the height of the sample surface from the storage unit based on the calculation result of this calculation unit and displaying it on the display unit. A surface charge measuring instrument. 2. A surface charge which is provided with a conductive probe attached to a cantilever-supported elastic piece and a displacement sensor for detecting the amount of displacement of the probe, the probe being used to probe the surface of the sample. In a surface charge measuring device for measuring an amount, a fine movement mechanism for finely moving the elastic piece in the height direction, a setting unit for setting the fine movement of the elastic piece by the fine movement mechanism to a minimum, and a fine movement based on the setting by the setting unit. A storage unit that stores the amount of displacement detected by the displacement sensor in accordance with the smallest fine movement of the mechanism,
A calculation unit that calculates the height of the sample surface based on the displacement amount detected by the displacement sensor, and a displacement amount corresponding to the height of the sample surface is read from the storage unit based on the calculation result of this calculation unit and displayed on the display unit. A surface charge measuring instrument, comprising: 3. A surface charge is provided which has a conductive probe attached to a cantilevered elastic piece and a displacement sensor for detecting the displacement of the probe, the probe probeing the sample surface. In a surface charge measuring device for measuring the amount, a fine movement mechanism for finely moving the elastic piece in the height direction, a setting unit for setting the fine movement of the elastic piece by the fine movement mechanism to a minimum, the sample surface and the probe. A bias circuit that applies a potential difference between
Based on a storage unit that stores a displacement amount detected by the displacement sensor along with the minimum fine movement of the fine movement mechanism based on the setting by the setting unit, and a displacement amount detected by the displacement sensor and a potential difference by the bias circuit. It has a calculation unit for calculating the height of the sample surface, and a control unit for reading the displacement amount according to the height of the sample surface from the storage unit based on the calculation result of this calculation unit and displaying it on the display unit. And a surface charge measuring instrument.