JP3095801B2 - Surface charge distribution measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As one of conventional surface charge distribution measuring devices, a vibrating capacitance type electrometer is widely used in various fields.

In this vibration capacitance type electrometer, the amount of electric charge is measured by an AC signal generated by vibrating a sensor electrode (probe) near a surface to be measured.

[0004] Further, in the above-mentioned vibration capacitance type electrometer, there is one in which a tip of a probe is sharpened in order to improve a spatial resolution.

[0005]

The vibration capacitance type electrometer of the former type has a problem that the spatial resolution is only about sub-millimeter. Furthermore, even in the latter case where the tip of the probe is sharpened, its spatial resolution is about 0.1 mm,
There is a problem that it is insufficient.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a surface charge distribution measuring device capable of obtaining a high spatial resolution of 1 μm or less.

[0007]

Means for Solving the Problems] inventions of this application, a cantilever is cantilevered holder, the tip of the cantilever, and the conductive material probes such as metal mounted toward the surface to be measured, The probe is moved and maintained with respect to the probe such that the distance in the Z-axis direction between the two is greater than the range of action of the atomic force and within the range of action of the Coulomb force. Moving means for relatively moving in the Y-axis direction, potential applying means for applying a modulated potential to the probe, and determining a modulation frequency f at which the vibration amplitude of the cantilever becomes maximum when the modulation frequency is changed. The above object is achieved by a surface charge distribution measuring device comprising: a charge detecting means for detecting a charge amount on a surface to be measured from the modulation frequency f.

Further, the second invention of this application relates to a cantilever supported by a holder in a cantilever manner, a probe made of a conductive material such as metal attached to the tip of the cantilever toward a surface to be measured, and On the other hand, the surface to be measured is moved and maintained such that the distance between the two in the Z-axis direction is larger than the range of action of the atomic force and is within the range of action of Coulomb force, and in the X and Y directions. Moving means for relatively moving the probe, fixed potential applying means for applying a fixed frequency potential to the probe, and detecting a charge amount on the surface to be measured from a phase delay of oscillation of the cantilever when applying a potential to the probe. The above object is attained by a surface charge distribution measuring device having a charge detecting means that performs the measurement.

The third invention of the present application is directed to a cantilever supported by a holder in a cantilever manner, a probe made of a conductive material such as metal attached to the tip of the cantilever toward a surface to be measured, and a probe for the probe. On the other hand, the surface to be measured is moved and maintained such that the distance between the two in the Z-axis direction is larger than the range of action of the atomic force and is within the range of action of Coulomb force, and in the X and Y directions. A moving means for relatively moving the probe, a fixed potential applying means for applying a fixed frequency potential to the probe, and a change in a vibration center position of the cantilever vibration when applying a potential to the probe, the electric charge on the surface to be measured. The above object is achieved by a surface charge distribution measuring device having a charge detecting means for detecting an amount.

In any one of the first to third inventions ,
A non-contact measurement of irregularities in the Z-axis direction of the surface to be measured is provided, and a displacement measuring unit having a memory for storing the measured value is provided, and the moving unit is based on the measured value stored by the displacement measuring unit. When measuring the surface charge, a reference value of the distance between the probe and the surface to be measured may be set.

[0011]

According to the first aspect of the present invention, a probe made of a conductive material such as a metal, which is out of the range of action of the electron force and in the range of action of Coulomb force, is supported by the cantilever and modulated by the probe. The potential is applied to vibrate, and the amount of charge on the surface to be measured is detected from the modulation frequency f at which the vibration amplitude at this time becomes maximum. Therefore, the charge amount can be measured without being affected by external vibrations or the like without detecting the amount of deflection of the cantilever.

According to a second aspect of the present invention 2 provides the potential of the fixed frequency to the cantilever, can be detected from the phase delay of the fixed vibration without being affected the amount of charge of the surface to be measured to an external vibration or the like it can.

According to the third invention of claim 3, giving the potential of the fixed frequency to the cantilever is vibrated, a change in the vibration center position, without being affected the amount of charge of the surface to be measured to an external vibration or the like Can be detected.

According to the fourth aspect of the present invention , the Z of the surface to be measured is
By measuring the unevenness in the axial direction in a non-contact manner in advance, the surface to be measured can be scanned with the probe based on the measured value, thereby enabling more accurate measurement.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a surface charge distribution measuring apparatus 10 according to the first embodiment of the present invention includes a cantilever 14 supported by a holder 12 at a cantilever, and a measured surface 16 guide mounted towards the
A conductive material probe 5 8, the conductive material probe 5 8
The surface 16 to be measured is moved so that the distance between them in the Z-axis direction (vertical direction in the figure) is larger than the range of action of the interelectron force and within the range of action of the Coulomb force, while maintaining the Coulomb force between the X, Y, and piezo stage 20 for relatively moving the Z-axis direction, and the conductive material pro <br/> over Bed 5 8 and the surface to be measured 16 cantilever And a deflection detecting means 22 for detecting the deflection amount of the conductive material 14 through the holder 12.
Frequency synthesizer for providing a modulated potential to the
And a detecting unit 3 in the deflection detecting means 22.
Lock to which the output signal of 2 (hereinafter referred to as signal 2) is input
The in-amp 62 and the non-contact optical displacement measurement system 44 (described later)
First analyzer for analyzing these signals (hereinafter referred to as signal 1)
Analyze signals from 36A and lock-in amplifier 62
And a second analyzer 36B for changing the modulation frequency.
When the vibration amplitude of the cantilever 14 is maximum,
Is determined , based on this modulation frequency f ,
Charge detection means 2 for detecting the amount of charge on the surface 16 to be measured
And 4.

The element of the deflection detecting means 22 includes a laser diode 26 for irradiating a laser beam on the surface of the cantilever 14 on the side opposite to the probe 18, and a part of the laser beam from the laser diode 26 for receiving the laser beam. A first light detector 28 for detecting the light intensity of the laser light, a second light detector 30 for receiving the reflected light of the laser light at the tip of the cantilever 14 and detecting the light intensity; It consists divider 32A and the amplifier 32B, the detection the second output B of the photodetector and calculating the ratio B / a of the output a of the first photodetector 28, and amplifies and outputs the operation result Part 32
And is provided. Here, it is desirable that the upper surface of the tip of the cantilever be coated with an LD light reflecting coating.

The reference numeral 50 in FIG.
, A beam splitter 52 for splitting light emitted from the laser diode 26 in the direction of the first photodetector 28, and a condensing lens 53 for condensing laser light from the laser diode 26. , 54 denote openings arranged on the entrance side of the second photodetector 30, each of which is included in the deflection detecting means 22.

The charge detecting means 24 includes the detecting unit 32
Signal from the inputs the lock-in an amplifier 62, the second inputting signals through the lock-in amplifier 62
An analysis portion 36B of the outputs a control signal to the piezo stage 2 0, and the control unit 38 which analyzes the signal of the second analysis unit 36 B is input, the analysis result of the signal in the second analysis portion 36 B and A position signal of the piezo stage 20 is input from the control unit 38, and a signal processing unit 40 that outputs a signal of the charge amount for each of the XY coordinates, and a signal processing unit that displays the charge amount based on the signal from the signal processing unit 40 And one display section 42.

The switch circuit 34 has information on the surface 16 to be measured in the Z-axis direction, that is, a measurement signal from a non-contact optical displacement measuring system 44 for measuring the unevenness of the surface 16 to be measured. The unevenness information of the measurement surface 16 in the Z-axis direction is input.

The charge detecting means 24 includes the first
A memory 46 for storing a signal from the non-contact optical displacement measurement system 44 input to the control unit 38 via the analyzing unit 36A together with the XY coordinate signal, and a second display unit 48 for displaying the contents of the memory 46 Are provided.

Here, the non-contact light displacement measuring system 44 is
Although a detailed description is omitted because it is publicly known, for example, a high-precision shape measurement method using an optical skid method is used.

Next, the operation of the above embodiment will be described.

The measurement is performed in a state where the piezo stage 20 is fixed in the X and Y directions. The measurement is performed in two steps of measuring the unevenness of the surface 16 to be measured by the non-contact optical displacement measuring system 44 and measuring the charge amount.

First, the measurement of the unevenness of the surface 16 to be measured will be described.

The unevenness of the surface 16 to be measured is measured by the non-contact optical displacement measuring system 44, and the signal is transmitted to the switch circuit 34.
Output to

The first analysis unit 36A is operated to parse the signal from the non-contact optical displacement measuring system 44, and outputs the result to the control unit 38.

As a result, the unevenness information that has passed through the first analysis unit 36A is stored in the memory 46 together with the XY coordinate signal sent from the control unit 38 to the piezo stage 20. At the same time, the contents stored in the memory 46 are displayed on the second display unit 48.

In this embodiment, a conductive material probe 58 is used.
Give a modulated potential from the frequency synthesizer 60
This causes the cantilever 14 to vibrate,
When the number is changed, the vibration amplitude of the cantilever 14 becomes
The modulation frequency f with the maximum calculated Me, from the modulation frequency f
It is used to detect the amount of charge of the measurement surface 16, then the deflection based on the detected value by the detecting unit 22 will be described in detail the process of measuring the charge.

The amount of deflection of the cantilever 14 is proportional to the Coulomb force between the surface 16 to be measured and the probe 18.

Since the incident angle of the laser beam from the laser diode 26 to the cantilever 14 is constant, the direction of the reflected light changes as the cantilever 14 bends.

The reflected light is received by the second photodetector 30 through the opening 54 and becomes an output signal B, which is output by the detector 3
Enter 2 Here, when the amount of deflection of the cantilever 14 changes, the amount of light passing through the opening 54 changes.
The intensity of the output signal B changes. When the light receiving area of the second photodetector 30 is smaller than the light beam diameter, the opening 54 can be omitted.

On the other hand, a part of the output light from the laser diode 26 is guided to the first photodetector 28 by the beam splitter 52, where the light intensity is detected, and becomes the output A to the detection unit 32. Is entered.

The divider 32A of the detection unit 32 calculates B / A, and outputs the signal to the lock-in amplifier 6 via the amplifier 32B.
Output to 2 . The reason why B / A is used as a signal is to remove the influence of the light intensity fluctuation of the laser diode 26 itself and perform accurate measurement.

The lock-in amplifier 62, detection unit 32 and
The signal from the frequency synthesizer 60 is converted to a second analysis unit 3
6 Output to B.

The second analysis unit 36 B simultaneously frequency Singh
Based on the signals from the synthesizers 60, it is operated to process the signal 2 and outputs the result to the control unit 38.

At this time, for example, as shown in FIG.
Assuming that the distance between the position measured by the non-contact displacement measuring system 44 and the probe 18 in the Y-axis direction is Y0 (known), the memory 46
The piezo stage 20 is moved by the control unit 38 in advance so that a predetermined position of the surface 16 to be measured is set to the reference point Z0 using the information as the reference point Z0.

Next, the piezo stage 20 is moved in the Z-axis direction so that the B / A signal 2 that has passed through the analysis unit 36 becomes constant.
Then, the frequency synthesizer 6 is connected to the conductive material probe 58.
When a modulated potential is applied through 0, the cantilever 14
Vibrates.

Accordingly, the laser light reflected at the tip of the cantilever 14 changes its reflection state, so that the output change of the second photodetector 30 can be obtained as a change amount ΔB.

[0040] Here, the relationship between the output B of the bend and the second optical detector 30 of the cantilever 14 is made as shown in Figure 3.

From FIG. 3 , it can be seen that the state when the bending of the cantilever 14 is zero can be set to any point of C1 to C5 in FIG. 3 depending on the position of the second photodetector 30.

[0042] In this embodiment, for example, so as to obtain a curve C3 in FIG. 3, to set the position of the opening 54 and the second photodetector 30. On the curve C3, the output B of the second photodetector 30 in the range up to the point a for the bending of the cantilever 14
Is in a substantially linear state.

On the other hand , the unevenness information of the surface 16 to be measured measured by the non- contact optical displacement measuring system 44 is stored in the memory 46 in advance. A control signal is output so that the distance in the Z-axis direction with respect to 18 is constant (start point), and the state is maintained. Therefore, the cantilever 14 at the starting point
, The magnitude of the vibration amplitude of the cantilever 14 is reflected in ΔB / A.

At this time, the vibrating cantilever 1
4, the diameter of the condenser lens 53, the diameter of the opening 54, the distance between the laser diode 26 and the probe 18, the probe 18, so as not to exceed the substantially linear portion of the curve C 3 in FIG. And the distance between the second photodetector 30 and the like are set in advance.

As described above, the modulation frequency is changed by the frequency synthesizer 30, and the modulation frequency f at which the vibration amplitude of the cantilever 14 becomes maximum is obtained from ΔB / A. At this time, the modulation frequency f from the frequency synthesizer 30 is input to the lock-in amplifier 62 as a reference signal, and of the ΔB / A signal components, only the signal near the modulation frequency f is narrowed by the lock-in amplifier 62. Amplify and detect. Therefore, it is possible to detect only a desired signal with good S / N without being affected by noise due to external vibration or the like.

This modulation frequency f is close to the natural frequency f0 of the cantilever 14, but when an attractive force based on the Coulomb force between the probe 18 and the surface 16 to be measured is applied, the modulation frequency f becomes higher. Will be shifted.

[0047] Therefore, the amount of deviation Δf = f-f0, it is possible to know the Coulomb force or surface charge amount, and the results
The information is displayed on the first display unit 42.

The measurement as described above is performed on the piezo stage 20.
May be moved at appropriate intervals in the X and Y directions to sequentially measure and display the unevenness and the charge amount in the XY plane. The memory 46 stores (Yo / y +
1) It suffices to have a capacity for storing the contents of X, Y, and Z of the point, measure the charge, display it on the first display unit,
After moving the Y-axis by y, the unevenness is measured, and when the information is displayed on the second display unit, the measurement may be performed while the contents are sequentially rewritten. Alternatively, if the capacity of the memory 46 is increased, the unevenness may be measured first over the entire XY plane and stored, and then the charge may be measured. The position of the measurement position and the conductive material probe 5 8 of the non-contact displacement measurement system 44 has been described for the case where remembering intervals in the Y-axis direction, which may be the X-axis direction, in view of the memory It is clear that the intermediate axis may be used.

In the embodiment shown in FIG. 1, the piezo stage 20 is moved in the Z-axis direction so that the amount of deflection of the cantilever 14 becomes a constant value, and then the amount of charge is measured. The present invention is not limited to this, and the piezo stage 20 includes the non-contact optical displacement measuring system 4.
4 may be moved in the Z-axis direction only based on the unevenness information of the surface 16 to be measured, and the charge amount may be detected based on the output signal intensity of the detection unit 32.

The above you施例is seeking charge amount of the surface to be measured 16 from the difference between the natural frequency f0 of the modulation frequency f and the cantilever 14, while the arrangement of FIG. 1, the charge in other ways The amount may be determined.

The second invention is described below. For example, the modulation frequency f at which ΔB / A is maximum in the measurement process of the above-described embodiment is fixed by the lock-in amplifier 62, and the lock-in amplifier 62 controls the ΔB / A of the reference signal from the frequency synthesizer 60. The phase delay of the detection signal may be detected, and the charge amount may be detected based on the detection.

The third invention will be described below. In the embodiment of FIG. 1 described above, the modulation frequency f is obtained, but the change in the vibration center position of the cantilever 14 is obtained from the signal 2 of ΔB / A by using the lock-in amplifier 62.
From this change, the charge amount of the surface 16 to be measured may be obtained. In this case, the reference vibration center is
In the case of the C3 curve in FIG. 4 , the point a is set, the Z axis is moved so that the ΔB / A output signal of the lock-in amplifier 62 is minimized, and the vibration center position change is performed based on the Z axis direction movement amount signal. What is necessary is just to obtain the amount and measure the charge amount. Further, a change in the movement center position may be obtained by using a light-receiving position detection type photodetector as the second photodetector. In this case, the output of the light receiving position detection type photodetector may be used as it is without using the lock-in amplifier. In this case, there is an advantage that the measurement time is short.

The use of the lock-in amplifier 62 according to the first , second and third inventions has the advantage that stable measurement can be performed without being affected by external noise.

In each of the above embodiments, the unevenness of the surface 16 to be measured is determined in advance by the non-contact optical displacement measuring system 44. It is not necessary to measure the unevenness by the optical displacement measurement system 44.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment according to the first, second , and third inventions.

FIG. 2 is a cross-sectional view showing a measurement process performed by the apparatus of the embodiment shown in FIG.

Figure 3 is a graph showing the relationship between the output of the bend and the second optical detector of the cantilever in the embodiment of FIG.

[Explanation of symbols]

10 : Surface charge distribution measuring device, 12: Holder, 14:
Cantilever, 16: surface to be measured , 20 : piezo stage, 22: deflection detecting means, 24: charge detecting means, 26
... Laser diode, 28 ... First photodetector, 30 ... Second photodetector, 38 ... Control unit, 44 ... Non-contact light displacement measuring system, 46 ... Memory, 56 ... Light-receiving position detection type photodetector,
58: Conductive material probe, 60: Frequency synthesizer.

Continuation of the front page (56) References JP-U 4-73809 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 29/14 G01R 29/12 G01R 29/24 G01N 37 / 00 H01J 37/28 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A cantilever supported by a holder in a cantilever manner, a conductive material probe attached to a tip of the cantilever toward a surface to be measured, and the surface to be measured with respect to the probe is disposed between the both. Moving means for moving and maintaining the distance in the Z-axis direction larger than the range of action of the atomic force and within the range of action of the Coulomb force, and for relative movement in the X and Y axes; Potential applying means for applying a potential modulated to the probe, and when the modulation frequency is changed, a modulation frequency f at which the oscillation amplitude of the cantilever becomes maximum is determined, and the charge amount of the surface to be measured is determined from the modulation frequency f. A surface charge distribution measuring device, comprising: a charge detecting means for detecting. 2. A cantilever supported by a holder in a cantilever manner, a conductive material probe attached to a tip of the cantilever toward a surface to be measured, and the surface to be measured with respect to the probe. Moving means for moving and maintaining the distance in the Z-axis direction larger than the range of action of the atomic force and within the range of action of the Coulomb force, and for relative movement in the X and Y axes; A fixed potential applying means for applying a fixed frequency potential to the probe; and a charge detecting means for detecting a charge amount of the surface to be measured from a phase delay of oscillation of the cantilever at the time of applying the potential to the probe. Surface charge distribution measuring device. 3. A cantilever supported by a holder in a cantilever manner, a conductive material probe attached to a tip of the cantilever toward a surface to be measured, and the surface to be measured with respect to the probe. Moving means for moving and maintaining the distance in the Z-axis direction larger than the range of action of the atomic force and within the range of action of the Coulomb force, and for relative movement in the X and Y axes; Fixed electric potential applying means for applying an electric potential of a fixed frequency to the probe; and electric charge detecting means for detecting the electric charge on the surface to be measured from a change in the vibration center position of the vibration of the cantilever when applying an electric potential to the probe. Surface charge distribution measuring device. 4. In any of claims 1 to 3, wherein while measuring the Z axis direction of the unevenness of the surface to be measured without contact, comprising a displacement measuring means having a memory for storing the measured value, the mobile Means for setting a reference value of the distance between the probe and the surface to be measured at the time of measuring the surface charge based on the measured value stored by the displacement measuring means; .