JP2000121535A - Scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an overshooting by moving a probe in the direction of Z axis being vertical to the sample surface and in the direction of X axis being in parallel with the sample surface and adding damping elements to the operation of a control means for changing the traveling direction of the probe so that a vibration state is achieved by an excitation member. SOLUTION: The microscope is provided with piezoelectric drive members 17 and 18 for X and Y directions, a semiconductor laser 21, a four-division photo detector 22, and the like, thus detecting the displacement of a probe 11 by the lever method. In addition, the microscope is provided with an oscillation circuit 27, a digital signal processor(DSP) 28, a personal computer(PC) 29, and the like, thus controlling relative move ment with respect to the sample surface of the probe 11. The probe 11 is supported by a support 12, and the support 12 is subjected to twist vibration by a vibrator 14. When the tip part of the probe excessively approaches the sample surface or is excessively separated from the sample surface, the traveling direction of the probe 11 is changed by an angle servo and a damping element is added to the angle servo to prevent the overshooting of the probe 11 from being repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning probe microscope, and more particularly, to information on only a change in force applied to a tip of a probe without detecting the direction in which the force is applied. The present invention relates to a scanning probe microscope that traces the surface of a sample by using a scanning probe microscope.

[0002]

2. Description of the Related Art In the industrial field where a scanning probe microscope is widely used in recent years, for example, in the field of semiconductors, it is necessary to measure not only a flat shape but also a side surface shape of a convex or concave portion of a sample surface which is almost vertical. Sex is increasing. However, in the conventional scanning probe microscope, when the side surface shape of the convex portion or the concave portion on the sample surface becomes nearly vertical, it is difficult to observe the side surface shape, and the side shape cannot be accurately observed.

The reason is that in the conventional scanning probe microscope, the interaction between the probe and the sample is made while scanning the probe at a constant speed in a direction (X direction or Y direction) parallel to the sample surface. This is because the probe is moved in the Z direction so as to be constant, and the change in the relative distance between the sample and the probe is fed back only in the vertical direction (Z direction) perpendicular to the sample surface. As a result of such feedback control, the number of data must be reduced on the steep side wall of the convex portion or concave portion on the sample surface. Further, in order for the probe to climb over the steep side wall, it is necessary to move the probe rapidly in the vertical direction (Z direction), and therefore, the feedback of the probe is unstable at the corner of the steep side wall. As a result, the sample surface could not be traced accurately.

As a solution to this problem, there has been a report on a scanning probe microscope for observing the shape of the side wall of a sample using a boot probe having a flared tip (see, for example, Yves Martin and H. et al.). Krmar Wickra
masinghe, Appl. Phys. Lett. 64 (19), 9 May 1994, "
Method forimaging sidewalls by atomic force micros
copy "). In this report, the boot probe is vibrated in the vertical and horizontal directions, the force acting on the probe from each direction is measured, and the values are fed back in the vertical and horizontal directions, respectively. The surface of a simple sample is traced.

[0005]

SUMMARY OF THE INVENTION
In the method of observing the shape of the side wall of the sample using a boot probe having a flared tip, the configuration of the apparatus must be complicated because the probe is vibrated vertically and horizontally. In addition, since the forces acting on the probe are separately detected in the vertical and horizontal directions and are fed back in two directions, the feedback control system is also complicated.

The present inventor has solved the problem of the prior art and traced the sample surface by only slightly vibrating the probe in one direction. In other words, we invented a scanning probe microscope that traces the surface of a sample using information on only the change in the force without detecting from which direction the force applied to the tip of the probe is acting. A patent application was filed as Japanese Patent Application No. 363129 (prior application invention).

According to the present invention, a probe which receives an interaction force from a sample surface and the probe and the sample are relatively 3
Driving means for moving the probe in a three-dimensional manner, exciting means for exciting the probe in the torsion direction, detecting means for detecting the vibration state of the probe, and the vibration state of the probe detected by the detecting means becomes a predetermined vibration state of the probe. And a control means for determining the relative movement direction between the probe and the sample and controlling the driving means based on the movement direction.

[0008] The control means is brought into a predetermined vibration state including a case where a difference occurs between the vibration state of the probe detected by the detection means and the vibration state of the probe detected before moving to the current position. Thus, the relative movement direction between the probe and the sample is determined. Then, the driving unit is controlled so as to relatively move the probe and the sample in the determined moving direction.

[0009] However, the prior invention has the following problems. That is, when tracing the sample surface with the probe, overshoot is repeated, and the overshoot amount does not converge to a small value. This situation is shown in FIG. In FIG. 7A, the horizontal axis represents a direction parallel to the sample surface (X-axis direction), and the vertical axis represents a direction perpendicular to the sample surface (Z-axis direction). In the figure, the side wall of the sample is located at the position of the Z axis, and the tip of the probe 11b is located at a position separated from the side wall of the sample by one, that is,
-1 is to be controlled.

As an initial condition, it is assumed that the probe 11b is traveling in the X-axis direction along the horizontal plane of the sample. In other words, the starting point of the probe is at the position of the coordinates (-1, 0), and the direction of the probe drive vector at that time is oriented horizontally to the side wall of the sample. From this time, since the probe 11b starts approaching the sample side wall, the probe drive vector is rotated counterclockwise by the control operation. Then, it starts approaching the target value again at the position of the coordinates (-1, 0.4), and then overshoots the target value and starts changing its direction again. As is clear from FIG. 7A, the trajectory of the probe 11b continues to overshoot the target value and does not converge to the target value. However, even in this tracing method, the probe was able to trace the sample surface while repeating overshoot. Further, since this overshoot amount is proportional to the moving distance from the position where the moving direction of the probe is determined to the position where the next new moving direction is determined, there is no practical problem by reducing this moving distance. It can be suppressed to a small extent. But,
If the moving distance is set to be small, there is a problem that the scanning speed is reduced. There has also been a demand for converging the overshoot to a small value to make scanning more stable.

The present invention has been made in order to solve such problems, and is a scanning probe microscope according to the invention of the prior application, which has no overshoot of the probe and has good followability to the sample surface. It is an object to provide a reliable product.

[0012]

A first means for solving the above-mentioned problems is that a probe and a probe or a sample are placed in a first direction (Z-axis direction) substantially perpendicular to the sample surface and substantially parallel to the sample surface. A driving unit for moving the probe in a suitable second direction (X-axis direction), an excitation member for exciting the probe, detection means for detecting the vibration state of the probe, and a vibration state of the probe detected by the detection means. The scanning direction of the probe or the sample to change the moving direction of the probe or the sample so that the vibration state of the probe or the sample is moved in the moving direction. A scanning probe microscope (Claim 1) characterized by adding elements.

Here, the damping element is an element that works to reduce the absolute value of the component of the probe drive vector perpendicular to the sample surface. In this means, since the damping element is added, the amount of movement of the probe in the direction perpendicular to the sample surface is smaller than in the case where the damping element is not added, thereby preventing overshoot. Since the magnitude of the output of the damping element can be set independently of the control gain, it is possible to prevent the response from being significantly reduced by the addition of the damping element.

[0014] A second means for solving the above-mentioned problems is as follows.
In the first means, the control means determines a change amount of the probe moving direction angle temporarily according to a difference between the vibration state of the probe detected by the detection means and a predetermined reference vibration state. And a damping element, in accordance with the difference between the vibration state of the probe detected by the detection means and the predetermined reference vibration state, to the amount of change in the direction of movement of the probe or sample, which is temporarily determined. The present invention is characterized in that the absolute value of the rotation angle to be added is determined (claim 2).

In the present means, as described as an example in the description of the invention of the prior application, the control means performs the primary control in accordance with the difference between the vibration state of the probe detected by the detection means and the predetermined reference vibration state. Next, the amount of change in the moving direction angle of the probe or the sample is determined (the moving amount is kept constant). The damping element is configured to rotate the probe or the sample in the moving direction angle in accordance with a difference between the vibration state of the probe detected by the detection means and the predetermined reference vibration state. Determine the absolute value of the angle. Therefore, only by calculating the difference between the vibration state of the probe detected by the detection means and the predetermined reference vibration state and the moving direction of the probe or the sample, the final deflection amount of the moving direction angle can be obtained. Thus, stable control can be performed efficiently. The sign of the rotation angle to be added to the temporarily determined change amount of the probe or sample movement direction angle is determined so as to reduce the direction component of the probe or sample movement direction perpendicular to the sample surface.

A third means for solving the above-mentioned problem is as follows.
In the second means, the absolute value of the rotation angle to be added to the amount of change in the direction of movement of the probe or sample is determined temporarily, the difference between the vibration state of the probe and the predetermined reference vibration state The present invention is characterized in that it is determined so as to increase as the value decreases.

In this means, as the difference between the vibration state of the probe and the predetermined reference vibration state becomes smaller, that is, as the distance between the probe and the sample becomes closer to the target value, the magnitude of the damping becomes larger. Thus, the relative position between the probe and the sample can be made closer to the target value.

A fourth means for solving the above-mentioned problem is as follows:
In any one of the second means to the third means, when the moving direction of the probe with respect to the sample determined by the control means is a direction away from the sample surface, the damping element has a rotation angle in the moving direction. Is increased (claim 4).

In this means, when the moving direction of the probe with respect to the sample is a direction moving away from the sample surface, the probe can be brought into a predetermined vibration state earlier by further increasing the change in the moving direction of the probe. .

A fifth means for solving the above-mentioned problems is any one of the second means to the fourth means, wherein the moving direction of the probe with respect to the sample determined by the control means is different from the second means. In the case of the direction approaching the sample surface, the damping element reduces the amount of change in the moving direction angle (claim 5).

In the present means, when the moving direction of the probe with respect to the sample determined by the control means becomes a direction approaching the sample surface, the change in the moving direction of the probe is reduced, so that the probe is quickly moved to a predetermined position. It can be made to vibrate.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a scanning probe microscope which is an example of an embodiment of the present invention. The probe 11 is supported by a support 12, and the support 12 is supported by a clip 13 on two vibrators 14 and 14 ′ (1) provided on a surface facing the clip 13.
4 ′ is not shown), and the clip 13 is held on the free end side of the Z-direction piezoelectric drive member 15. The other end of the Z-direction piezoelectric drive member 15 is
It is fixed to the block 16. The block 16 is supported by one ends of the X-direction piezoelectric driving member 17 and the Y-direction piezoelectric driving member 18, and the other ends of the X-direction piezoelectric driving member 17 and the Y-direction piezoelectric driving member 18 are respectively connected to a frame 19.
, The frame 19 is supported by three micrometers 20.

This scanning probe microscope has a probe 1
The displacement of 1 is detected by the optical lever method. Therefore, the semiconductor laser 21 which is a light emitting member fixed to the block 16 is used.
And a four-divided photodetector 22 for detecting the position of the light spot of the reflected light from the probe 11, and a mirror 23 fixed to the support 12 of the probe 11 via an arm. Light incident on the probe 11 and reflected light from the probe 11 are once reflected by the mirror 23.

The scanning probe microscope according to the present embodiment has a signal processing circuit 24,
Lock-in amplifier 25, A / D converter 26, oscillation circuit 2
7, a digital signal processor (DSP) 28, a personal computer (PC) 29, a display device 30 such as a CRT, D / A converters 31, 32, 33, and a drive circuit 34.

Under the control of the DSP 28, the oscillating circuit 27 supplies an excitation signal (sine wave signal) having a frequency close to the resonance frequency of the torsional vibration of the probe 11 to the vibrators 14, 14 ', and transmits the excitation signal to a reference signal. To the lock-in amplifier 25. The lock-in amplifier 25 outputs a signal having a level proportional to the amplitude of the same frequency component as the frequency of the excitation signal given to the oscillators 14 and 14 ′ from the oscillation circuit 27. This signal is converted by the A / D converter 26 into A
/ D converted and supplied to the DSP 28.

The DSP 28 basically includes an oscillation circuit 27
Control the operation of the vibrators 14 and 14 ′ through
Based on the detected value of the amplitude of the vibration from the / D converter 26,
A drive signal is given to each of the X, Y, and Z-direction piezoelectric drive members 15, 17, and 18 via the D / A converters 31, 32, and 33 and the drive circuit 34, and the relative movement of the probe 11 with respect to the sample surface is controlled. Control. The DSP 28 converts the data indicating the shape of the sample surface obtained at this time (in this embodiment, a sequentially obtained probe drive vector described later) into the DSP 28.
28 is stored in a memory (not shown). The data in the memory of the DSP 28 is taken into the personal computer 29 and displayed on the display device 30 as an image.

FIG. 2 shows a detailed view of the probe 11 and its vibrating section. The vibrators 14 and 14 ′ and the ball 35 are fixed inside the clip 13. And the probe 11
Is held by the elastic force of the clip 13 and pressed against the vibrators 14 and 14 ′ and the ball 16. That is, the support 12 is provided with the vibrators 14, 14 '.
And three points of contact with the ball 16.

The vibrators 14, 14 'expand and contract alternately in the horizontal direction in the figure. That is, when the vibrator 14 expands, the vibrator 14 'contracts, and when the vibrator 14 contracts, the vibrator 14'
Grows. As a result, the support 12 receives torsional vibration about the point of contact with the ball 35, and this is transmitted to the probe 11.

When the probe 11 is excited at a frequency substantially equal to the resonance frequency, the probe 11 is in a torsional resonance state, and periodically rotates left and right about the axis 11d. Also,
When the probe 11 is in torsional resonance, the probe 11b
Causes the moment of inertia to increase sharply due to the interaction force from the sample or the like. When the moment of inertia increases,
Since the resonance frequency in the torsional direction is low, the probe 11
The mirror part 11a deviates from its own torsional resonance state,
The angle range swung around 1d becomes smaller. Hereinafter, the amount of angle of the mirror 11a to be swung is referred to as the amplitude in the torsion direction.

FIG. 3 is a diagram schematically showing the state of the magnitude of the amplitude in the torsional direction of the probe 11 and the movement of the probe in the scanning probe microscope according to the embodiment of the present invention. The magnitude of the amplitude in the torsional direction of the probe 11 is
It means that it is large according to the length of the arrow. This scanning probe microscope performs feedback control according to the amplitude in the torsional direction, and moves the probe 11 according to the shape of the convex portion 42 of the sample.

This feedback control is performed as follows in accordance with the flowchart shown in FIG. Note that the probe drive vector is one control time unit (S3 to S
A vector indicating the amount V of movement of the probe at the time of performing step 6), and is a two-dimensional vector indicated by V (V _X , V _Z ).

First, as step S1, torsional resonance is caused in the probe 11 at a position far from the horizontal portion 41 of the sample. Then, as step S2, the probe 11b of the probe 11 is brought close to the horizontal portion 41 of the sample until the amplitude in the torsional direction is determined in advance. In this manner, the magnitude of the amplitude of the probe 11 in the torsional direction when the approach of the probe 11 to the sample surface is completed is determined by the length of the arrow 44 at the position where the measurement start time t = 0 in FIG. Is indicated by The magnitude of the amplitude of the probe 11 in the torsional direction at the time t = 0 is treated as a target value.

Then, in step S3, the probe 11 is first moved at a predetermined probe movement vector 45. At time t = 1 after the movement, a deviation between the target value and the magnitude of the current amplitude is calculated as a step S4, and an arithmetic processing for determining the probe drive belt is performed as a step S5. However, in this case, since the torsional amplitude of the probe 11 is not different from that at the time point t = 0, there is no difference from the target value of the amplitude. Therefore, steps S4, S5
The new probe drive vector obtained by the above becomes the same as the probe drive vector 45.

Then, the probe drive vector 45 is used as a new probe drive vector in step S6 to obtain DS.
It is stored in the memory in P26. Thereafter, the process returns to the step S3, and the probe 11b is driven to the point indicated by the probe drive vector 56 again.

When the time t = 2 after the movement, the probe 11 approaches the convex portion 42 of the sample, so that the distance between the probe 11b and the sample becomes shorter. Therefore, an interaction between the sample side wall and the probe portion 11b (for example, in this case, an effect by Van der Waals force) acts, and the amplitude of the probe 11 in the torsional direction decreases. Then, as described above, in step S4, it is determined how much the amplitude in the torsional direction at that time has changed from the target value. Incidentally, when the deviation between the twist direction of the amplitude A at each time point and the target amplitude value A _S and .DELTA.A (A-A _S), as described above, in step S5, for example, by the following equation, the probe-driving Determine the direction in which to rotate the vector. θ ₁ = −Tan ⁻¹ (G · ΔA) (4)

Here, θ ₁ is an angle for changing the direction of the probe drive vector in the next step, and G is a gain. The probe drive vector 56 at the next time t = 3 is obtained by rotating the probe drive vector at the current time t = 2 by θ ₁ obtained by the above equation (4). In the invention of the prior application, the probe driving vector at the time t = n is represented by V _n (V _Xn , V _Yn ).
Assuming that the probe driving vector at the next time point t = n + 1 is V _{n + 1} (V _{X (n + 1)} , V _{Y (n + 1)} ), V _{n + 1} becomes θ in the following equation. _It can be obtained by substituting ₁ .

[0037]

(Equation 1)

The probe drive vector 4 thus obtained
5 is obtained by rotating the probe drive vector 45 obtained at the time t = n by the servo angle θ.

However, with such a control, as described above, the movement of the probe repeatedly overshoots. Therefore, in the present invention, a damping operation is added when the moving direction of the probe is determined. An example of this embodiment will be described below.

FIG. 4A is a diagram in which the sample surface tracing method (angle servo) in this control method is considered in four phases. The figure shows a state where the tip of the probe traces the vertical sample surface,
The set value arrow indicates a set locus (X = -1 line in FIG. 7) to which the tip of the probe should move. In the figure, phase I and phase II show the case where the tip of the probe is too close to the sample surface, and the case where the amplitude of the probe is smaller than the target value or the phase delay of vibration is larger than the target value. Conversely, phase III and phase IV indicate cases where the tip of the probe is too far from the sample surface, where the probe amplitude is larger than the target value or the phase delay of vibration is smaller than the target value. It is.

In phase I and phase IV, when the probe drive vector is directed toward the sample surface, that is, when the probe is approaching the sample surface, the phase II and phase III indicate that the probe drive vector is This is the case where the probe faces in the opposite direction to the sample surface direction, that is, the case where the probe is moving away from the sample surface.

FIG. 4B shows that, in each of the four phases, the direction in which the probe movement direction is changed by the angle servo and the direction in which the probe moves are changed to the angle servo in order to prevent repetitive overshoot of the probe. The direction which is changed by the added damping element is shown. In phases I and II, the direction of the angle servo is counterclockwise. That is, control is performed to rotate the probe drive vector counterclockwise. In phases III and IV, the direction of the angle servo is clockwise. That is, control is performed to rotate the probe drive vector clockwise.

On the other hand, the damping element rotates the probe drive vector clockwise in phases II and III so that the probe drive vector rotates counterclockwise in phase I and phase IV. It is added to make it. Moreover, it is more effective if the size of the damping element takes a large value in a region close to the target value.

In the present embodiment, in step S5 described above, the size of such a damping element is determined, and the probe drive vector is determined taking this into account.
An example of a method of determining the rotation amount of the probe drive vector and the size of the damping element by the angle servo will be described with reference to FIG.
5, the horizontal axis represents the difference .DELTA.A = A-A _S of amplitude A and the amplitude of the set value A _S of the probe, the vertical axis rotation amount theta ₁ of the probe drive vector by the angle servo probe by the damping element indicating the amount of rotation theta _d of the needle drive vector.

In FIG. 5, the rotation amount θ ₁ of the probe drive vector by the angle servo is determined by the above equation (4), and the gain G is set to 1.
(The presumed movement of the probe is to move the sample surface when looking to the right in the moving direction.)

Further, as the rotation amount θ _d of the probe driving vector due to the damping element, θ _d = ± Tan ⁻¹ 1 / ΔA (6) is used. However, the sign is + in phases I and IV, and-in phases II and III.

When the probe drive vector is set in a direction in which the probe amplitude moves away from the set value, the sign is the same as the rotation amount θ ₁ of the probe drive vector by the angle servo. Are set so as to be different from each other. In this way, when the moving direction of the probe determined by the angle servo is a direction away from the sample surface, the damping element increases the rotation angle in the moving direction, and is determined by the angle servo. When the moving direction of the probe is a direction approaching the sample surface, the damping element functions to reduce the amount of change in the moving direction angle. Therefore, the probe can be scanned while maintaining the distance between the probe and the sample surface such that the amplitude of the probe becomes the set value earlier.

In the phases I and II, the rotation amount θ ₁ of the probe drive vector by the angle servo becomes plus,
The probe drive vector is rotated counterclockwise. Phase III, in the IV, the rotation amount theta ₁ of the probe drive vector by the angle servo becomes negative, the probe drive vector is rotated clockwise. In each case, Δ
As the absolute value of A increases, the absolute value of θ ₁ also increases, and the correction amount of the probe drive vector increases as the deviation increases.
However, the absolute value of the rotation amount θ ₁ of the probe drive vector is 90
The probe does not go back because it does not exceed 戻 り.

In the equation (6), the sign of the rotation amount θ _d of the probe driving vector by the damping element is the phase I, IV
And the probe drive vector is rotated counterclockwise. Further, the phase becomes negative in phases II and III, and the probe drive vector is rotated clockwise.

The final rotation amount of the probe drive vector is given by θ = θ ₁ + k · θ _d (7) Here, k is a gain. By substituting θ given by equation (7) into equation (5), a new probe drive vector is determined. According to the equations (6) and (7), the rotation amount θ of the probe movement vector determined by the angle servo is increased in the phases I and III, and is decreased in the phases II and IV. You can see that. This relationship is shown in FIG.

FIG. 7B shows the result of simulating the trajectory of the angle servo when damping is given by such a function. Compared with FIG. 7A, the stability of the servo is clearly improved.

In this scanning probe microscope, in order to output an image of the sample surface, the probe drive vector is stored for each position where the rotation amount θ ₁ of the probe drive vector is obtained. Then, when displaying an image, the stored probe drive vector is read out to the PC 29 to perform image processing. The result of the processing is displayed on the display device 30.

As described above, in the present embodiment,
Unlike the conventional scanning probe microscope, the sample and the probe 1
In addition to feeding back the change in the interaction with the sample 1b only in the vertical direction (Z direction) perpendicular to the sample surface, XZ
Feedback is provided in the direction of movement of the probe 11b in a plane parallel to the plane. Therefore, the number of data can be increased even on the steep side wall of the convex portion or the concave portion of the sample surface, and the feedback of the probe portion 11b even when the probe portion 11b gets over the steep side wall. Control can be stabilized, and the probe 11b can accurately trace the sample surface. Therefore, high-precision measurement can be performed on the side surface of the convex portion or the concave portion on the sample surface.

In the above-described embodiment, damping is given in all phases in order to treat dumping in a unified manner.
You may give only to IV. Although various functions can be used for the damping function, it is preferable to use a function that takes a large value when the change between the target value and the actual value is small as in this embodiment.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, when the correction amount θ of the angle is obtained by the arc tangent, the angle θ becomes ± 90 ° or less, and there is an advantage that the probe does not return. However, when the surface of the observation target has very sharp irregularities, the correction amount θ If the specimen surface can be traced more accurately by extending the angle to ± 180 °, the obtained correction amount θ can be obtained by multiplying θ obtained by using the arc tangent by a predetermined number, in this case, a number from 1 to 2. ± 1
It is within 80 degrees. Further, the gains G, G
_d is a proportional control that simply multiplies the deviation by a coefficient,
Here, a PID control or the like may be performed by adding a differential term or an integral term in consideration of a frequency component.

In the above-described embodiment, the correction amount θ is obtained using the arc tangent. However, a value obtained by multiplying the deviation by a certain value may be used as the correction amount θ. in this case,
The time for calculating the arc tangent is not required, and the tip can be fed back faster.
However, if the deviation is large, the correction amount θ becomes 90 ° or more, and the probe may return or become 180 ° or more, and the feedback may not be meaningful. In this case, upper and lower limit values may be provided for the correction amount so that the correction amount falls within the range.

Further, in this embodiment, the amplitude of the probe is used as a quantity representing the vibration state of the probe.
A phase difference between the phase of the probe vibration detected by the detection means and the phase of the vibration of the excitation member may be used. Also in this case, a control method that is almost the same as that described in the above embodiment can be used.

In the above description, the scanning probe microscope in which the probe is moved has been described as an example. However, the same method can be applied to the scanning probe microscope in which the sample is moved. Can very easily understand what modifications should be made to apply the items described above to a sample moving scanning probe microscope.

Although the above-described embodiment is an example in which the present invention is applied to an atomic force microscope, the present invention relates to a scanning capacitance microscope, a scanning electrostatic force microscope, a scanning magnetic force microscope, and a scanning magnetic force microscope. The present invention can also be applied to various other types of scanning probe microscopes such as a tunneling microscope.

[0060]

As described above, according to the first aspect of the present invention, since the damping element is added, the amount of movement of the probe in the direction perpendicular to the sample surface is reduced. , It is smaller than when no damping element is added, thereby preventing overshoot.

According to the second aspect of the present invention, only by calculating the difference between the vibration state of the probe detected by the detecting means and the predetermined reference vibration state and the moving direction of the probe, the final moving direction can be calculated. The change amount of the angle can be obtained, and stable control can be performed efficiently.

According to the third aspect of the present invention, since the magnitude of the damping increases as the position of the probe approaches the target value, the probe position can be efficiently brought closer to the target value.

In the invention according to claim 4, when the moving direction of the probe with respect to the sample is a direction moving away from the surface of the sample, the change in the moving direction of the probe is further increased so that the probe is quickly brought into a predetermined vibration state. Can be done.

In the invention according to claim 5, when the moving direction of the probe with respect to the sample determined by the control means is a direction approaching the sample surface, the change in the moving direction of the probe is reduced, so that the probe is moved earlier. The probe can be brought into a predetermined vibration state.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a scanning probe microscope as an example of an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a probe and a vibration unit in the scanning probe microscope shown in FIG.

FIG. 3 is a diagram schematically showing the state of the magnitude of the amplitude of the probe in the torsional direction and the movement of the probe in the scanning probe microscope according to the embodiment of the present invention.

FIG. 4 is a diagram showing phases in which a probe traces a sample surface, and output directions of angular servo and damping in each phase.

FIG. 5 is a diagram illustrating an example of an angle servo output and a calculation result of a damping amount.

FIG. 6 is a schematic flowchart showing a control operation of a digital signal processor (DSP) in the scanning probe microscope according to the embodiments of the present invention.

FIG. 7 is a graph showing an example of a simulation result of a control state of a probe according to the invention of the prior application and the invention of the present application.

[Explanation of symbols]

11 probe, 12 support, 13 clip, 1
4, 14 ': vibrator, 15: piezoelectric drive member for Z direction, 1
6 ... Block, 17 ... X direction piezoelectric drive member, 18 ... Y
Directional piezoelectric drive member, 19: frame, 20: micrometer, 21: semiconductor laser, 22: four-segment photodetector, 23: mirror, 24: signal processing circuit, 25
... lock-in amplifier, 26 ... A / D converter, 27 ... oscillation circuit, 28 ... digital signal processor (DSP),
29 personal computer (PC), 30 display device, 31, 32, 33 D / A converter, 34 drive circuit, 35 ball, 41, 43 sample horizontal part, 42
Convex part of the sample, 44... Probe amplitude (reference value), 45.
Tip movement vector

Claims (5)

[Claims] A probe, a drive unit for moving the probe or the sample in a first direction (Z-axis direction) substantially perpendicular to the sample surface and in a second direction (X-axis direction) substantially parallel to the sample surface;
An exciting member for exciting the probe, a detecting means for detecting a vibration state of the probe, and changing a moving direction of the probe or the sample so that the vibration state of the probe detected by the detecting means becomes a predetermined vibration state. In a scanning probe microscope equipped with control means for controlling the drive unit to move the probe or sample in the direction, the operation of the control means,
A scanning probe microscope characterized by adding a damping element. 2. The scanning probe microscope according to claim 1, wherein the control means controls the probe or the sample according to a difference between the vibration state of the probe detected by the detection means and a predetermined reference vibration state. The damping element determines the amount of change in the moving direction angle, and the damping element determines the moving direction angle of the probe or the sample in accordance with the difference between the vibration state of the probe detected by the detection means and the predetermined reference vibration state. A scanning probe microscope for determining a rotation angle to be added to a change amount. 3. The scanning probe microscope according to claim 2, wherein the magnitude of the rotation angle added to the amount of change in the movement direction angle of the probe or the sample is determined by a vibration state of the probe and the predetermined reference vibration state. A scanning probe microscope characterized in that the difference is determined so as to increase as the difference from the probe probe decreases. 4. The scanning probe microscope according to claim 2, wherein the moving direction of the probe with respect to the sample determined by the control means is a direction away from the sample surface. In the scanning probe microscope, the damping element increases a change amount of the moving direction angle. 5. One of claims 2 to 4
In the scanning probe microscope according to the item, when the moving direction of the probe with respect to the sample determined by the control means is a direction approaching the sample surface, the damping element, the moving direction angle of the A fixed-displacement probe microscope characterized by reducing the amount of change.