Scanning probe microscope and scanning method using the same

To avoid applying overload on both a probe and a sample surface, and to reduce time for measuring irregular shapes on the sample surface in performing an intermittent measurement method, provided is a scanning probe microscope including: a cantilever having a probe attached thereto, the scanning probe microscope being configured to scan a sample surface by intermittently bringing the probe into contact with the sample surface; and a control device configured to perform a first operation of bringing the probe and the sample surface into contact with each other, and a second operation of separating the probe and the sample surface from each other after the first operation. The control device executes the second operation by thermally deforming the cantilever.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent Application No. JP 2018-057954, filed Mar. 26, 2018, the entire contents of which are incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scanning probe microscope and a scanning method using the same.

2. Description of the Related Art

In Japanese Patent Application Laid-open No. 2001-33373, there is disclosed a scanning probe microscope configured to continuously scan a probe, which is formed at a distal end of a cantilever, while maintaining the probe in contact with a sample, to thereby measure irregular shapes on a sample surface. It should be noted, however, that with the scanning probe microscope described in Japanese Patent Application Laid-open No. 2001-33373, the probe and the sample surface are always in contact with each other, and hence wearing down of the probe and damage to the sample may occur.

In contrast, in each of Japanese Patent Application Laid-open Nos. 2007-85764 and 2011-209073, there is proposed an intermittent measurement method of measuring irregular shapes of a sample surface by bringing a probe and the sample surface into contact with each other only at a plurality of preset measurement points on the sample surface to intermittently scan the sample surface. The “contact between the probe and the sample surface” in each of the patent documents refers to approaching to a distance at which a physical interaction occurs, and determining the contact based on a physical quantity of the interaction. Representative examples of the physical quantity include attractive force and repulsive force.

Specifically, in the intermittent measurement method, the probe is moved to approach the sample surface from above a predetermined measurement point, and the sample surface is intermittently scanned through repeated switching between a first step of bringing the probe into contact with the sample surface to measure a height of the probe, and a second step of separating the probe, which is in contact with the sample surface, from the sample surface and moving the probe to above a next measurement point after the first step. In actual measurement, a step of measuring a physical property between the probe and the sample, or a step of measuring the shape and the physical property at the same time is often performed between the first step and the second step.

As a result, in the above-mentioned intermittent measurement method, as compared to Japanese Patent Application Laid-open No. 2001-33373, the probe and the sample surface are brought into contact with each other only at the measurement points, with the result that minimal contact is required, and that wearing down of the probe and damage to the sample can be reduced.

Meanwhile, in the above-mentioned intermittent measurement method, an operation of separating the probe that is in contact with the sample surface is performed with a scanner using a piezoelectric element. However, the piezoelectric element has an inevitable lag in response, with the result that, in the piezoelectric element, no-response time occurs from when a signal for instructing start of the separating operation is acquired to when the separating operation is started, and the probe approaches the sample also in that time to apply a force of a set value or more. Therefore, in the intermittent measurement method, it is required to set an approach speed in consideration of the force of the set value or more, which is generated by the above-mentioned lag in response, and it is thus difficult to set an approach speed that is too fast. As a result, measurement time in which the irregular shapes on the sample surface are measured cannot be reduced, and hinders an increase in speed.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentioned circumstances, and therefore has an object to avoid applying overload on both a probe and a sample surface, and to reduce time for measuring irregular shapes on the sample surface in performing an intermittent measurement method.

According to one embodiment of the present invention, there is provided a scanning probe microscope including: a cantilever having a probe attached thereto, the scanning probe microscope being configured to scan a sample surface by intermittently bringing the probe into contact with the sample surface; and a control device configured to perform a first operation of bringing the probe and the sample surface into contact with each other, and a second operation of separating the probe and the sample surface from each other after the first operation, wherein the control device is configured to execute the second operation by thermally deforming the cantilever.

Further, in one embodiment of the present invention, in the above-mentioned scanning probe microscope, the control device includes a fine movement mechanism configured to relatively move the probe and the sample surface by using a piezoelectric element, and the control device is configured to execute the second operation by using both the thermal deformation of the cantilever and the fine movement mechanism.

Further, in one embodiment of the present invention, the above-mentioned scanning probe microscope further includes a first light illuminator configured to irradiate the cantilever with light, and the control device is configured to thermally deform the cantilever by controlling an illumination intensity of the light with which the first light illuminator irradiates the cantilever during the second operation.

Further, in one embodiment of the present invention, the above-mentioned scanning probe microscope further includes an optical lever displacement detector including a second light illuminator, which is configured to irradiate a first surface of the cantilever with laser light, to detect a displacement amount of the cantilever based on reflection of the laser light with which the second light illuminator irradiates the first surface, and the second light illuminator also serves as the first light illuminator.

Further, in one embodiment of the present invention, in the above-mentioned scanning probe microscope, the control device includes: a determiner configured to determine whether the probe and the sample surface are brought into contact with each other based on the displacement amount of the cantilever, which is detected by the optical lever displacement detector, during the first operation; and a controller configured to execute, after the determiner determines that the probe and the sample surface are brought into contact with each other, the second operation by setting an illumination intensity of the laser light of the second light illuminator weaker than an illumination intensity of the laser light in the first operation to thermally deform the cantilever.

Further, in one embodiment of the present invention, the above-mentioned scanning probe microscope further includes a light control element configured to control an illumination intensity of the laser light with which the second light illuminator irradiates the first surface, and the control device includes: a determiner configured to determine whether the probe and the sample surface are brought into contact with each other based on the displacement amount of the cantilever, which is detected by the optical lever displacement detector, during the first operation; and a controller configured to execute, after the determiner determines that the probe and the sample surface are brought into contact with each other, the second operation by controlling the light control element so that an illumination intensity of the laser light with which the second light illuminator irradiates the first surface is set weaker than an illumination intensity of the laser light in the first operation to thermally deform the cantilever.

Further, in one embodiment of the present invention, in the above-mentioned scanning probe microscope, the first surface of the cantilever has a coefficient of thermal expansion that is larger than a coefficient of thermal expansion of a second surface of the cantilever, which is on a side opposite to the first surface.

Further, in one embodiment of the present invention, in the above-mentioned scanning probe microscope, the cantilever includes a resistor, and the control device is configured to thermally deform the cantilever by energizing the resistor during the second operation.

Further, in one embodiment of the present invention, in the above-mentioned scanning probe microscope, the cantilever includes a piezoresistor, and the control device includes: a determiner configured to determine whether the probe and the sample surface are brought into contact with each other based on a value of resistance of the piezoresistor during the first operation; and a controller configured to execute, after the determiner determines that the probe and the sample surface are brought into contact with each other, the second operation by energizing and heating the piezoresistor to thermally deform the cantilever.

According to one embodiment of the present invention, there is provided a scanning method using a scanning probe microscope, the scanning probe microscope including a cantilever having a probe attached thereto to scan a sample surface by intermittently bringing the probe into contact with the sample surface, the scanning method including: a first operation step of bringing the probe and the sample surface into contact with each other; and a second operation step of separating the probe and the sample surface from each other after the first operation step, wherein the second operation step includes separating the probe and the sample surface from each other through use of thermal deformation of the cantilever.

As described above, according to the embodiments of the present invention, it is possible to avoid applying overload on both the probe and the sample surface, and to reduce time for measuring irregular shapes on the sample surface in performing the intermittent measurement method.

DESCRIPTION OF THE EMBODIMENTS

A scanning probe microscope according to an embodiment of the present invention is a scanning probe microscope using a probe scanning method called an “intermittent measurement method”, in which a probe is brought into contact with a sample surface to intermittently scan the sample surface with the probe.

Now, the scanning probe microscope according to an embodiment of the present invention is described with reference to the accompanying drawings. In the drawings, the same or similar parts are denoted by the same reference symbols, and duplicate description may be omitted. Moreover, a shape, a size, and the like of an element in the drawings may be emphasized for clearer description.

First Embodiment

FIG. 1is a diagram for illustrating an example of a schematic configuration of a scanning probe microscope A according to a first embodiment of the present invention. As illustrated inFIG. 1, the scanning probe microscope A includes a cantilever1, a movement driver2, a displacement detector3, a heating device4, and a control device5.

The cantilever1includes a probe1aat a distal end thereof. The cantilever1is fixed at a proximal end thereof, and the distal end is a free end. The cantilever1is an elastic lever member having a small spring constant K, and when the probe1aat the distal end and a surface (hereinafter referred to as the “sample surface”) of a sample S are brought into contact with each other, the cantilever1is deformed in accordance with a pressing force, with which the probe1aat the distal end presses the sample surface.

Moreover, when the probe1aat the distal end and the sample surface are brought into contact with each other, and when the sample surface is inclined, the cantilever1is twisted or deformed in accordance with the inclination of the sample surface, and support reaction of a support, which is a contact point between the probe1aat the distal end and the sample surface.

The movement driver2is a fine movement mechanism capable of moving the probe1aand the sample S relatively in three-dimensional directions. The movement driver2includes a Z-direction drive unit21(driver) and an XY scanner22(scanning unit).

A sample stage H is placed on the Z-direction drive unit21. The sample S is placed on the sample stage H to be opposed to the probe1aof the cantilever1.

The Z-direction drive unit21is configured to move the sample stage H in a direction (Z direction) perpendicular to a horizontal plane. The Z-direction drive unit21is a piezoelectric element, for example.

The Z-direction drive unit21is configured to move the sample stage H in the Z direction under control of the control device5, to thereby perform an operation of bringing the sample surface closer to the probe1a, or an operation of moving the sample S in a direction of being separated from the probe1a.

The XY scanner22is configured to move the probe1aand the sample S relatively with respect to XY directions under control of the control device5. InFIG. 1, a plane parallel to a surface of the sample stage H is the horizontal plane, and is herein defined as an “XY plane” by two orthogonal axes X and Y. For example, the XY scanner22is a piezoelectric element.

The Z-direction drive unit21and the XY scanner22may be arranged in any relationship as long as the configuration is capable of relatively scanning a three-dimensional shape for observation. In other words, the cantilever or the sample may be scanned.

The displacement detector3is configured to detect a deformation amount and a twist amount of the cantilever1. For example, the displacement detector3detects the deformation amount and the twist amount of the cantilever1with the use of an optical lever method.

The displacement detector3includes a light illuminator31and a photodetector32.

The light illuminator31is configured to irradiate a reflecting surface (not shown) formed on a back surface (first surface) F1of the cantilever1with laser light L1. The “back surface (first surface) F1” as used herein is a surface on a side opposite to a front surface (second surface) F2of the cantilever1, on which the probe1ais arranged.

The photodetector32is configured to receive laser light L2reflected by the above-mentioned reflecting surface. The photodetector32is a photodetector including quadrant receiving surfaces33configured to receive the laser light L2reflected by the reflecting surface. The laser light L2reflected by the reflecting surface of the cantilever1enters the plurality of receiving surfaces33, which are quarters of the photodetector32. For example, a position of the photodetector32is adjusted such that the laser light L2reflected by the reflecting surface of the cantilever1enters the receiving surfaces33at near the center thereof.

Now, a method of detecting the deformation amount and the twist amount of the cantilever1in the first embodiment is described with reference toFIG. 1andFIG. 2.FIG. 2is a perspective view of the sample S having a slope, and the cantilever1.

The cantilever1is displaced in any one or both of the Z direction and a Y direction when the probe1aand the sample surface are brought into contact with each other. In the first embodiment, the displacement of the cantilever1that occurs in the Z direction is referred to as the “deformation amount”, and the displacement of the cantilever1that occurs in the Y direction is referred to as the “twist amount”. For example, in initial conditions, an incident spot position of the laser light L2that is reflected under a state in which no force is applied on the probe1a, on the receiving surfaces33of the photodetector32, is a center position O of the receiving surfaces33. The “state in which no force is applied on the probe1a”is a state in which, because the probe1aand the sample surface are not in contact with each other, the cantilever is not deformed by a force at the time of contact, for example.

In a contact mode, when the probe1aand the sample surface are brought into contact with each other, the force is applied on the probe1a, with the result that the deformation amount and the twist amount are generated in the cantilever1. Therefore, a reflected spot position of the laser light L2reflected by the reflecting surface of the cantilever1having the deformation amount and the twist amount generated therein is displaced from the center position O. Thus, the scanning probe microscope A can detect a magnitude and a direction of the force applied on the probe1aby capturing a movement direction of the spot position on the receiving surfaces33of the photodetector32.

For example, inFIG. 1, when the twist amount is generated in the cantilever1, a change in spot position in an α direction can be captured on the receiving surfaces33of the photodetector32. Moreover, when the deformation amount is generated in the cantilever1, a change in spot position in a β direction can be captured on the receiving surfaces33.

In this case, an amount of change in spot position from the center position O depends on the twist amount and the deformation amount. Specifically, when the cantilever1is deformed in a +Z direction, the reflected spot of the laser light L2on the receiving surfaces33of the photodetector32is changed in a +β direction. Similarly, when the cantilever1is deformed in a −Z direction, the reflected spot of the laser light L2on the receiving surfaces33of the photodetector32is changed in a −β direction. Meanwhile, when the twist amount is generated in the cantilever1in a +Y direction, the reflected spot position of the laser light L2on the receiving surfaces33of the photodetector32is changed in a +α direction. Similarly, when the twist amount is generated in the cantilever1in a −Y direction, the reflected spot of the laser light L2on the receiving surfaces33of the photodetector32is changed in a −α direction.

The photodetector32outputs a first detection signal corresponding to the reflected spot position of the laser light L2in the ±Z directions of the receiving surfaces33to the control device5. In other words, the first detection signal is a DIF signal (deformation signal) corresponding to the deformation amount of the cantilever1. Moreover, the photodetector32outputs a second detection signal corresponding to the reflected spot position of the laser light L2in the ±Y directions of the receiving surfaces33to the control device5. In other words, the second detection signal is an FFM signal (twist signal) corresponding to the twist amount of the cantilever1.

Returning toFIG. 1, the heating device4is driven by the control device5to change a temperature of the cantilever1. The heating device4may have any configuration as long as the cantilever1can be heated, and a heating method thereof is not particularly limited. For example, the heating device4can heat the cantilever1by a method described below.

For example, as illustrated inFIG. 3, the heating device4may include a light illuminator4ato heat the front surface F2of the cantilever1by irradiating the front surface F2of the cantilever1with the laser light, an infrared ray, or other such light from the light illuminator4aon the basis of a signal (hereinafter referred to as a “heating signal”) from the control device5. The method of heating the cantilever1by irradiating the cantilever1with the light is hereinafter referred to as a “light heating method”.

Alternatively, as illustrated inFIG. 4, the heating device4may include a microwave illuminator4bcapable of applying microwave to heat the front surface F2of the cantilever1by irradiating the front surface F2of the cantilever1with the microwave from the microwave illuminator4bon the basis of the heating signal from the control device5. The method of heating the cantilever1by irradiating the cantilever1with the microwave is hereinafter referred to as a “microwave heating method”.

Still alternatively, as illustrated inFIG. 5, the heating device4may energize and heat the cantilever1by energizing the cantilever1. For example, the heating device4includes a resistor41c, a first electrode42c, a second electrode43c, and a voltage applicator44c.

The resistor41cis included in the cantilever1. For example, the resistor41cis a conductive member including a resistor capable of generating heat, and is formed on the cantilever1.

The first electrode42cis provided on the front surface F2of the cantilever1, and is electrically connected to a first end of the resistor41c.

The second electrode43cis provided on the front surface F2of the cantilever1, and is electrically connected to a second end of the resistor41c.

The voltage applicator44cis configured to generate heat by applying a predetermined voltage between the first electrode42cand the second electrode43cto allow an electric current to flow through the resistor41con the basis of the heating signal from the control device5. As a result, the cantilever1is heated.

Yet alternatively, as illustrated inFIG. 6, the heating device4may energize and heat the cantilever1by generating an induced current in the cantilever1by electromagnetic induction. For example, the heating device4includes a current circuit41d, a first electrode42d, a second electrode43d, and a voltage applicator44d.

The current circuit41dis a circuit including a resistor, and is provided to the cantilever1.

The first electrode42dis provided on the back surface F1side of the cantilever1.

The second electrode43dis provided on the front surface F2side of the cantilever1.

The voltage applicator44dis configured to cause the electric current to flow through the resistor by applying an AC voltage between the first electrode42cand the second electrode43con the basis of the heating signal from the control device5to generate the induced current in the current circuit41d. As a result, the front surface F2of the cantilever1is heated.

The first electrode42dand the second electrode43dmay each be an electromagnet instead of an electrode.

Next, the control device5in the first embodiment is described.

As illustrated inFIG. 1, the control device5includes a determiner6, a controller7, and a measurement unit8.

The determiner6is configured to determine whether the probe1ais brought into contact with the sample surface on the basis of the first detection signal and the second detection signal, which are output from the photodetector32. In the following description, the processing of determining whether the probe1ais brought into contact with the sample surface is referred to as “contact determination processing”.

Moreover, the determiner6is configured to determine whether the probe1ais separated from the sample surface on the basis of the first detection signal and the second detection signal, which are output from the photodetector32. In the following description, the processing of determining whether the probe1ais separated from the sample surface is referred to as “separation determination processing”.

The controller7is configured to control a relative movement amount between the probe1aand the sample S. The scanning probe microscope A according to an embodiment of the present invention uses the intermittent measurement method, in which the sample surface is intermittently scanned by bringing the probe1ainto contact with only a plurality of preset measurement points on the sample surface. Therefore, the controller7is configured to control each of the following operations: an approaching operation (first operation) of bringing the probe1acloser to a measurement position; a separating operation (second operation) of separating the probe1aand the sample S from each other; and a movement operation of moving the probe1ato above the next measurement position.

Now, a configuration of the controller7is described. The controller7includes a driver71and a heating controller72.

The driver71is configured to control the movement driver2to move the probe1aand the sample S relatively with respect to the three-dimensional directions.

Specifically, in order to bring the probe1aand the sample surface into contact with each other, the driver71outputs an approaching operation signal to the Z-direction drive unit21to elevate the sample S. As a result, the controller7can bring the probe1aand the sample surface closer to each other.

Moreover, in order to separate the probe1aand the sample surface from each other, the driver71outputs a separating operation signal to the Z-direction drive unit21to lower the sample S. As a result, the driver71can move the sample surface in the direction of being separated from the probe1a.

Further, the controller7outputs a drive signal to the XY scanner22to move the probe1ato a measurement descending position, which is located immediately above the next measurement position.

The heating controller72is configured to control output of the heating device4. Specifically, the heating controller72controls the output of the heating device4to control deformation of the cantilever1due to a change in temperature thereof. The deformation of the cantilever1due to the change in temperature thereof is referred to as “thermal deformation of the cantilever1”.

For example, the heating controller72outputs the heating signal to the heating device4to drive the heating device4. As a result, the front surface F2of the cantilever1is heated by the heating device4to thermally expand as the thermal deformation (that is, the cantilever1is deformed in the direction of being separated from the sample S). In contrast, the heating controller72stops outputting the heating signal to the heating device4to stop driving the heating device4. As a result, the heating of the cantilever1by the heating device4is stopped, and the front surface F2of the cantilever1is reduced in temperature to be contracted as the thermal deformation (that is, the cantilever1is deformed in the direction of approaching the sample S).

The measurement unit8is configured to measure irregular shapes on the sample surface under a state in which the probe1aand the sample surface are in contact with each other. For example, when it is determined in the contact determination processing that the probe1ais brought into contact with the sample surface, the measurement unit8measures a distance (hereinafter simply referred to as “relative distance”) by which the sample S is moved relatively to the probe1ain the approaching operation, to thereby measure the irregular shapes on the sample surface. For example, the measurement unit8may calculate the relative distance on the basis of a voltage value of the drive signal under the state in which the probe1aand the sample surface are in contact with each other. Alternatively, the measurement unit8may directly measure displacement of the sample stage H by a sensor (not shown), or may directly measure a height of the sample stage H by a sensor (not shown). Moreover, the operation of determining that the probe1ais brought into contact with the sample surface in the contact determination processing, and the operation of measuring the relative distance may be performed in parallel, to thereby measure irregular shapes on the sample surface on the basis of the relative distance at the time when it is determined that the probe1ais brought into contact with the sample surface.

Next, a flow of the intermittent measurement method of the scanning probe microscope A according to the first embodiment is described with reference toFIG. 7. As the initial conditions, a case is assumed in which the probe1ais positioned at a measurement descending position of a predetermined measurement point.

The driver71starts the approaching operation by outputting the approaching operation signal to the Z-direction drive unit21to elevate the sample stage H (Step S101).

When the approaching operation is started by the driver71, the determiner6executes the contact determination processing, in which it is determined whether the probe1ais brought into contact with the sample surface on the basis of the first detection signal and the second detection signal, which are output from the photodetector32(Step S102).

Now, the contact determination processing in the first embodiment is described.

When the deformation amount indicated by the first detection signal output from the photodetector32exceeds a first range, the determiner6determines that the probe1ais brought into contact with the sample surface. Moreover, when the twist amount indicated by the second detection signal output from the photodetector32exceeds a second range, the determiner6determines that the probe1ais brought into contact with the sample surface.

As described above, when at least one of a first condition, in which the deformation amount indicated by the first detection signal output from the photodetector32exceeds the first range, or a second condition, in which the twist amount indicated by the second detection signal output from the photodetector32exceeds the second range, is satisfied, the determiner6determines that the probe1ais brought into contact with the sample surface. Although there has been described above the example in which the first detection signal and the second detection signal are determined independently, the determination may be performed on the basis of a set value corresponding to characteristics. For example, “the square of the first detection signal” and “the square of the second detection signal” may be added to each other in the determiner6, and when a positive value of a square root of the sum is a predetermined value or more, it may be determined that the probe1ais brought into contact with the sample surface.

When it is determined in the above-mentioned contact determination processing that the probe1ais brought into contact with the sample surface, the driver71stops outputting the approaching operation signal to stop the approaching operation (Step S103). In this case, the probe1ais in contact with the sample surface, and hence the cantilever is twisted or deformed by a predetermined amount or more. Then, the measurement unit8measures the irregular shapes on the sample surface by measuring the relative distance under the state in which the approaching operation is stopped (Step S104). Alternatively, the operation of determining by the contact determination processing that the probe1ais brought into contact with the sample surface, and the operation of measuring the relative distance may be performed in parallel, and the irregular shapes on the sample surface may be measured on the basis of the relative distance at the time when it is determined that the probe1ais brought into contact with the sample surface.

When the measurement of the relative distance by the measurement unit8is complete, the controller7starts the separating operation, in which the sample S and the probe1aare separated from each other. Specifically, the heating controller72controls the output of the heating device4so as to thermally deform the cantilever1, to thereby start the separating operation (Step S105).

Specifically, in starting the separating operation, the heating controller72outputs a drive signal to the heating device4. When acquiring the drive signal from the heating controller72, the heating device4heats the front surface F2of the cantilever1. As a result, the front surface F2of the cantilever1is heated and expanded, and the cantilever1is thermally deformed to be warped upward (+Z) toward the back surface F1side. Therefore, the separating operation is started with this thermal deformation.

A response speed of the thermal deformation is far faster than a response speed of the piezoelectric element. In other words, a response speed of a separating operation (first separating operation) through the thermal deformation of the cantilever1is far faster than a response speed of a separating operation (second separating operation) by the Z-direction drive unit21(fine movement mechanism). Therefore, in the first embodiment, the separating operation is started through use of not the Z-direction drive unit21but the thermal deformation of the cantilever1, to thereby reduce measurement time of the irregular shapes on the sample surface.

At the same time with the start of the first separating operation through the thermal deformation of the cantilever1, the driver71starts the second separating operation, in which the sample S is moved in the direction of being separated from the probe1a, by outputting a separating operation signal to the Z-direction drive unit21(Step S106). Even when both of the separations are started simultaneously, the operation is performed as follows: the separation through the thermal deformation, which is fast in response, leads, and the separation with the fine movement mechanism, which is slow in response, follows. Both of the above-mentioned separating operations are executed for predetermined time, and are then ended (Step S107). The “predetermined time” is up to a timing when the Z fine movement mechanism responds by an amount that is equivalent to the deformation amount of the thermal deformation or more.

When the separating operation is stopped, the controller7outputs the drive signal to the XY scanner22, to thereby move the probe1ato the measurement descending position located immediately above the next measurement position (Step S108). Then, the controller7performs the operation of from Step S101to Step S108also at the next measurement position. In other words, the scanning probe microscope A performs the operation of from Step S101to Step S109for each measurement point on the sample S, to thereby intermittently scan the sample surface.

Next, effects of the first embodiment are described.

In the scanning probe microscope configured to perform the intermittent measurement method in the contact mode, the approaching operation and the separating operation are executed at each measurement position. Therefore, in the intermittent measurement method, an increase in measurement time of the irregular shapes becomes more problematic than in the method in which the probe are scanned continuously to measure the irregular shapes on the sample surface.

To address this problem, in the intermittent measurement method, in order to reduce the measurement time of the irregular shapes, it is required to perform the approaching operation and the separating operation at high speed. It should be noted, however, that in the related-art method in which the approaching operation and the separating operation are performed with the fine movement mechanism, that is, the piezoelectric element, delay in response of the piezoelectric element hinders the reduction in above-mentioned measurement time.

More specifically, generally in the intermittent measurement method, the separating operation is performed at a time point when the probe and the sample surface are brought into contact with each other during the approaching operation, and when a force applied on the cantilever reaches a target value (F0). It should be noted, however, that from when it is detected that the force applied on the cantilever reaches the target value to when the separating operation is actually started, that is, until when the probe and the sample surface start moving in the direction of being separated from each other, a time difference (delay in response) ΔT (msec) occurs. Therefore, a force F (nN) exceeding a force of the target value is generated, and the probe is further pressed into the sample surface by the force F. When an approach speed between the probe and the sample surface is represented by V (nm/msec), and the spring constant of the cantilever is represented by K (N/m), the force F (nN) can be expressed as the following relational expression (1) by the Hooke's law.
F(nN)=V(nm/msec)×ΔT(msec)×K(N/m)  (1)

As a method of reducing the measurement time of the irregular shapes in the intermittent measurement method, there is a method of simply increasing the approach speed V. It should be noted, however, that with that method, as is clear from the above-mentioned relational expression (1), when the approach speed V is increased, the force F is increased, and when a state in which F0<<F is established, damage to the probe or deformation of the sample may occur. Therefore, when it is attempted to suppress the force F to a predetermined value in order to prevent the damage to the probe and the deformation of the sample, the approach speed V cannot be increased, and the measurement time cannot be reduced with the related-art method.

For example, in the scanning probe microscope, it is assumed that a general cantilever having a spring constant of 40 N/m is used, and that a force (F+F0: provided that F>>F0) with which the damage to the probe or the deformation of the sample can be prevented is 10 nN or less. In this case, in the related-art method in which the approaching operation and the separating operation are performed by the piezoelectric element, an upper limit of a contact speed is estimated.

In general, in a case of a tube PZT piezoelectric element, a delay in response ΔT of about 0.2 msec occurs. Moreover, even with a stacked PZT piezoelectric element, which operates at high speed, a delay in response ΔT of about 0.04 msec occurs. Therefore, on the basis of the relational expression (1), an upper limit of the approach speed V is “1.25 nm/msec” for the tube PZT piezoelectric element, and “6.25 nm/msec” for the stacked PZT piezoelectric element.

In contrast, in the intermittent measurement method in the first embodiment, the separating operation is executed with the use of not the piezoelectric element but the thermal deformation of the cantilever1. In the scanning probe microscope A, time from when it was detected that the force applied on the cantilever1reached the target value to when the cantilever1was thermally deformed was 0.1 μsec in an Example. In other words, time from when it is detected that the force applied on the cantilever1reaches the target value to when the separating operation is actually started, that is, the delay in response ΔT is 0.1 μsec. Therefore, when a spring constant K=40 N/m, and when the force (F+F0: provided that F>>F0)=10 nN, the approach speed V=2,500 nm/msec, and the approaching operation can be performed at a speed that is 2,000 times the speed of the tube PZT piezoelectric element, and 400 times the speed of the stacked PZT piezoelectric element. As a result, the scanning probe microscope A can significantly reduce the measurement time as compared to the related art.

As described above, the scanning probe microscope A according to the first embodiment executes the separating operation by thermally deforming the cantilever1. As a result, the scanning probe microscope A can significantly reduce the measurement time as compared to the related art.

Alternatively, the scanning probe microscope A may execute the separating operation with the use of both the thermal deformation of the cantilever1and the fine movement mechanism (movement driver2). In the first embodiment, the cantilever1is thermally deformed to execute the first separating operation, and then the second separating operation by the fine movement mechanism is executed. However, the present invention is not limited thereto. For example, the first separating operation and the second separating operation may be executed simultaneously.

Moreover, the cantilever1may be formed of a single material (for example, Si), or the back surface F1and the front surface F2may be formed of materials having different expansion coefficients. For example, in the scanning probe microscope A, the front surface F2is thermally deformed by being heated, and hence the cantilever1may be configured such that a coefficient of thermal expansion of the front surface F2is larger than the expansion coefficient of the back surface F1, for example. The front surface F2may be set to have a coefficient of thermal expansion that is larger than that of the back surface F1through formation of a layer of a good conductor having a coefficient of thermal expansion that is larger than that of the back surface F1on the front surface F2of the cantilever1, for example. Specifically, the back surface F1is formed of Si, and the front surface F2is formed of A1.

Second Embodiment

Now, a scanning probe microscope B according to a second embodiment of the present invention is described with reference to the drawings. The scanning probe microscope B according to the second embodiment is different from that of the first embodiment in that, in performing the separating operation, the heating device4heats not the front surface F2but the back surface F1of the cantilever1.

FIG. 8is a diagram for illustrating an example of a schematic configuration of the scanning probe microscope B according to the second embodiment. As illustrated inFIG. 8, the scanning probe microscope B includes a cantilever1, a movement driver2, a displacement detector3, a heating device4B, and a control device5B.

The heating device4B is configured to heat the back surface F1of the cantilever1. The heating device4B may have any configuration as long as the cantilever1can be heated, and a heating method thereof is not particularly limited. For example, as in the first embodiment, the heating device4B may heat the back surface F1of the cantilever1by a light heating method or a microwave method. Alternatively, the heating device4B may energize and heat the front surface F2of the cantilever1. For example, the heating device4includes a resistor41c, a first electrode42c, a second electrode43c, and a voltage applicator44c. It should be noted, however, that in this case, the resistor41c, the first electrode42c, and the second electrode43care provided on the back surface F1of the cantilever1. Still alternatively, the heating device4B may energize and heat the cantilever1by generating an induced current in the front surface F2of the cantilever1by electromagnetic induction. For example, the heating device4includes a current circuit41d, a first electrode42d, a second electrode43d, and a voltage applicator44d. It should be noted, however, that in this case, the current circuit41dis provided on the back surface F1of the cantilever1.

Next, the control device5B in the second embodiment is described.

As illustrated inFIG. 8, the control device5B includes a determiner6, a controller7B, and a measurement unit8.

The controller7B is configured to control a relative movement amount between the probe1aand the sample S. As in the first embodiment, the scanning probe microscope B uses an intermittent measurement method, in which the sample surface is intermittently scanned by bringing the probe1ainto contact with only a plurality of preset measurement points on the sample surface. Therefore, the controller7B is configured to control each of the following operations: an approaching operation of bringing the probe1acloser to a measurement position; a separating operation of separating the probe1aand the sample S from each other; and a movement operation of moving the probe1ato above the next measurement position.

Now, a configuration of the controller7B in the second embodiment is described. The controller7B includes a driver71and a heating controller72B.

The heating controller72B is configured to control output of the heating device4B. Specifically, the heating controller72B controls the output of the heating device4B to control deformation of the cantilever1due to a change in temperature thereof.

For example, the heating controller72B outputs the heating signal to the heating device4B to drive the heating device4B. As a result, the back surface F1of the cantilever1is heated by the heating device4to thermally expand as the thermal deformation (that is, the cantilever1is deformed in the direction of approaching the sample S). In contrast, the heating controller72B stops outputting the heating signal to the heating device4B to stop driving the heating device4. As a result, the heating of the cantilever1by the heating device4B is stopped, and the front surface F2of the cantilever1is contracted as the thermal deformation (that is, the cantilever1is deformed in the direction of being separated from the sample S).

Now, a flow of the intermittent measurement method of the scanning probe microscope B according to the second embodiment is described with reference toFIG. 9. As the initial conditions, a case is assumed in which the probe1ais positioned at a measurement descending position of a predetermined measurement point.

First, before starting the approaching operation, the controller7B heats and thermally deforms the back surface F1of the cantilever1. In other words, the heating controller72B controls the output of the heating device4B so as to thermally deform the cantilever1(Step S201).

Specifically, the heating controller72B outputs a drive signal to the heating device4B. When acquiring the drive signal from the heating controller72B, the heating device4B heats the back surface F1of the cantilever1. As a result, the back surface F1of the cantilever1is heated and expanded, and the cantilever1is thermally deformed to be bent downward (−Z) toward the front surface F2side.

Under the state in which the cantilever1is thermally deformed downward (−Z) toward the front surface F2side, the driver71outputs an approaching operation signal to the Z-direction drive unit21to start the approaching operation (Step S202).

When the approaching operation is started by the driver71, the determiner6executes the contact determination processing, in which it is determined whether the probe1ais brought into contact with the sample surface, on the basis of the first detection signal and the second detection signal, which are output from the photodetector32(Step S203). The contact determination processing in the second embodiment is similar to that in the first embodiment, and hence description thereof is omitted.

When it is determined in the above-mentioned contact determination processing that the probe1ais brought into contact with the sample surface, the driver71stops outputting the approaching operation signal to stop the approaching operation (Step S204). In this case, the probe1ais in contact with the sample surface, and hence the cantilever is twisted or deformed by a predetermined amount or more. Then, the measurement unit8measures the relative distance under the state in which the approaching operation is stopped, to thereby measure the irregular shapes on the sample surface (Step S205).

When the measurement of the relative distance by the measurement unit8is complete, the controller7B controls the output of the heating device4B so as to stop heating the cantilever1, to thereby start the separating operation (Step S206).

Specifically, in starting the separating operation, the heating controller72B stops outputting the drive signal to the heating device4B. Therefore, when the drive signal from the heating controller72B disappears, the heating device4B stops heating the back surface F1of the cantilever1. As a result, the expanded back surface F1of the cantilever1is contracted, and the cantilever1is thermally deformed upward (+Z) toward the back surface F1side. Therefore, the separating operation (first separating operation) is started through the thermal deformation.

A response speed of the separating operation (first separating operation) through the thermal deformation of the cantilever1is far faster than a response speed of the separating operation (second separating operation) by the Z-direction drive unit21(fine movement mechanism). Therefore, in the second embodiment, the separating operation is started through use of not the Z-direction drive unit21but the thermal deformation of the cantilever1, which is caused by the reduction in temperature, to thereby reduce measurement time of the irregular shapes on the sample surface.

With the reduction in temperature of the back surface F1, the cantilever1is thermally deformed. At the same time with the start of the first separating operation with the thermal deformation, the driver71outputs the separating operation signal to the Z-direction drive unit21to start the second separating operation, in which the sample S is moved in the direction of being separated from the probe1a(Step S207). Even when both of the separation operations are started at the same time, separation through the thermal deformation, which is fast in response, leads, and the separation with the fine movement mechanism, which is slow in response, follows. Both of the above-mentioned separating operations are executed for the predetermined time, and are then ended (Step S208). The “predetermined time” is up to a timing when the Z fine movement mechanism responds by an amount that is equivalent to the deformation amount of the thermal deformation or more.

When the separating operation is stopped, the controller7B outputs the drive signal to the XY scanner22, to thereby move the probe1ato the measurement descending position located immediately above the next measurement position (Step S209). Then, the controller7B performs the operation of from Step S201to Step S209also at the next measurement position. In other words, the scanning probe microscope B performs the operation of from Step S201to Step S209for each measurement point on the sample S, to thereby intermittently scan the sample surface.

As described above, the scanning probe microscope B according to the second embodiment executes the separating operation by thermally deforming the cantilever1. As a result, the scanning probe microscope B attains an effect of significantly reducing the measurement time as in the first embodiment.

Moreover, in the scanning probe microscope B, the cantilever1may be configured such that the expansion coefficient of the back surface F1is larger than a coefficient of thermal expansion of the front surface F2, for example. As a result, the separating operation is enhanced not only by the thermal expansion due to temperature gradient of the heated back surface F1in the cantilever1but also by a bimetallic effect, and fast separating operation over a long distance can be performed. In this case, instead of heating the back surface F1of the cantilever1, the entire cantilever1may be heated.

Moreover, the cantilever1in the second embodiment may be formed of a single material (for example, Si), or the back surface F1and the front surface F2may be formed of materials having different expansion coefficients. For example, the cantilever1in the second embodiment may be configured such that a coefficient of thermal expansion of the back surface F1is larger than the expansion coefficient of the front surface F2. The back surface F1may be set to have a coefficient of thermal expansion that is larger than that of the front surface F2through formation of a layer of a good conductor having a coefficient of thermal expansion that is larger than that of the front surface F2on the back surface F1of the cantilever1, for example. Specifically, the back surface F1is formed of A1, and the front surface F2is formed of Si.

Moreover, when starting the separating operation, the heating controller72B stops outputting the drive signal to the heating device4B. However, the present invention is not limited thereto. For example, when starting the separating operation, instead of stopping outputting the heating device4B, the heating controller72B may lower the output of the heating device4B than during the approaching operation.

Third Embodiment

Now, a scanning probe microscope C according to a third embodiment of the present invention is described with reference to the drawings. The scanning probe microscope C according to the third embodiment is different from the embodiments described above in that the heating device4is not provided, and in that the cantilever1is thermally deformed by the light illuminator31.

FIG. 10is a diagram for illustrating an example of a schematic configuration of the scanning probe microscope C according to the third embodiment. As illustrated inFIG. 10, the scanning probe microscope C includes a cantilever1, a movement driver2, a displacement detector3, and a control device5C.

The control device5C includes a determiner6, a controller7C, and a measurement unit8.

The controller7C is configured to control an illumination intensity of the light illuminator31.

Moreover, the controller7C is configured to control a relative movement amount between the probe1aand the sample S. As in the first embodiment, the scanning probe microscope C uses an intermittent measurement method, in which the sample surface is intermittently scanned by bringing the probe1ainto contact with only a plurality of preset measurement points on the sample surface. Therefore, the controller7C is configured to control each of the following operations: an approaching operation of bringing the probe1acloser to the measurement position; a separating operation of separating the probe1aand the sample S from each other; and a movement operation of moving the probe1ato above the next measurement position.

Now, a configuration of the controller7C in the third embodiment is described. The controller7C includes a driver71and a laser controller72C.

The laser controller72C is configured to control output of the light illuminator31, to thereby control an illumination intensity of laser light L1applied by the light illuminator31. In this case, the light illuminator31irradiates the back surface (first surface) F1of the cantilever1with the laser light L1. Therefore, the back surface F1of the cantilever1is heated by the laser light L1. Thus, the laser controller72C can change a temperature of the back surface F1of the cantilever1to thermally deform the back surface F1by increasing or reducing the illumination intensity of the laser light L1. In other words, the laser controller72C controls the output of the light illuminator31to control the deformation of the cantilever1due to the change in temperature thereof.

Next, a flow of the intermittent measurement method of the scanning probe microscope C according to the third embodiment is described with reference toFIG. 11. As the initial conditions, a case is assumed in which the probe1ais positioned at a measurement descending position of a predetermined measurement point.

The laser controller72C controls the output of the light illuminator31to control the illumination intensity of the laser light L1applied by the light illuminator31to a first illumination intensity (Step S301). As a result, the laser light L1of the first illumination intensity, which is applied by the light illuminator31, is reflected by the back surface F1of the cantilever1to enter the receiving surfaces33of the photodetector32at near the center thereof. Further, the back surface F1of the cantilever1is heated by the laser light L1of the first illumination intensity, which is applied by the light illuminator31. As a result, the back surface F1of the cantilever1is heated and expanded, and the cantilever1is thermally deformed to be bent downward (−Z) toward the front surface F2side.

Under the state in which the cantilever1is thermally deformed downward (−Z) toward the front surface F2side, the driver71outputs an approaching operation signal to the Z-direction drive unit21to start the approaching operation (Step S302).

When the approaching operation is started by the driver71, the determiner6executes the contact determination processing, in which it is determined whether the probe1ais brought into contact with the sample surface, on the basis of the first detection signal and the second detection signal, which are output from the photodetector32(Step S303). The contact determination processing in the third embodiment is similar to that in the first embodiment, and hence description thereof is omitted.

When it is determined in the above-mentioned contact determination processing that the probe1ais brought into contact with the sample surface, the driver71stops outputting the approaching operation signal to stop the approaching operation (Step S304). In this case, the probe1ais in contact with the sample surface, and hence the cantilever is twisted or deformed by a predetermined amount or more. Then, the measurement unit8measures the relative distance under the state in which the approaching operation is stopped, to thereby measure the irregular shapes on the sample surface (Step S305).

When the measurement of the relative distance by the measurement unit8is complete, the laser controller72C controls the output of the light illuminator31to weaken the illumination intensity of the laser light L1, which is applied by the light illuminator31, from the first illumination intensity to a second illumination intensity. In other words, when starting the separating operation, the laser controller72C weakens the illumination intensity of the laser light L1, which is applied by the light illuminator31, from the first illumination intensity to the second illumination intensity. As a result, the back surface F1of the cantilever1that has been expanded is contracted with a reduction in temperature. In other words, the cantilever1is thermally deformed upward (+Z) toward the back surface F1side. Therefore, the separating operation (first separating operation) is started with this thermal deformation (Step S306).

A response speed of the separating operation (first separating operation) through the thermal deformation of the cantilever1is far faster than a response speed of the separating operation (second separating operation) by the Z-direction drive unit21(fine movement mechanism). Therefore, in the third embodiment, the separating operation is started through use of not the Z-direction drive unit21but the thermal deformation of the cantilever1, which is caused by the reduction in temperature, to thereby reduce measurement time of the irregular shapes on the sample surface.

With the reduction in temperature of the back surface F1, the cantilever1is thermally deformed. At the same time with the start of the first separating operation with the thermal deformation, the driver71outputs the separating operation signal to the Z-direction drive unit21to start the second separating operation, in which the sample S is moved in the direction of being separated from the probe1a(Step S307). Even when both of the separation operations are started at the same time, separation through the thermal deformation, which is fast in response, leads, and the separation with the fine movement mechanism, which is slow in response, follows. Both of the above-mentioned separating operations are executed for the predetermined time, and are then ended (Step S308). The “predetermined time” is up to a timing when the Z fine movement mechanism responds by an amount that is equivalent to the deformation amount of the thermal deformation or more.

When the separating operation is stopped, the controller7C outputs the drive signal to the XY scanner22, to thereby move the probe1ato the measurement descending position located immediately above the next measurement position (Step S309). Then, the controller7C performs the operation of from Step S301to Step S309also at the next measurement position. In other words, the scanning probe microscope C performs the operation of from Step S301to Step S309for each measurement point on the sample S, to thereby intermittently scan the sample surface.

As described above, the scanning probe microscope C according to the third embodiment executes the separating operation by thermally deforming the cantilever1. As a result, the scanning probe microscope C attains an effect of significantly reducing the measurement time as in the first embodiment.

Moreover, in the scanning probe microscope C according to the third embodiment, the heating device4is not provided, and the cantilever1is thermally deformed with the light illuminator31, which is an optical lever light source. In other words, in the scanning probe microscope C, the light illuminator31also serves as the light illuminator4afor heating to form both of an optical lever optical path and an optical path for heating the cantilever1. As a result, it is not required to add the heating device4to thermally deform the cantilever1, and cost is thus reduced.

Moreover, in the third embodiment, not a base of the cantilever1but the distal end of the cantilever1is heated with light. Therefore, the back surface F1of the cantilever1can be heated with a higher temperature, and hence large thermal deformation can be generated.

Moreover, when the cantilever1is irradiated with the laser light to heat the cantilever1, an amount of heat required to thermally deform the cantilever1by the heating is changed depending on the spring constant of the cantilever1. Therefore, the illumination intensity of the laser light, which is applied by the light illuminator4a, may be determined depending on the spring constant of the cantilever1.

Moreover, in the scanning probe microscope C, for example, the cantilever1may be configured such that the expansion coefficient of the back surface F1is larger than a coefficient of thermal expansion of the front surface F2. As a result, the separating operation is enhanced not only by the thermal expansion due to temperature gradient of the heated back surface F1in the cantilever1but also by the bimetallic effect, and fast separating operation over a long distance can be performed. In this case, instead of heating the back surface F1of the cantilever1, the entire cantilever1may be heated.

For example, the back surface F1may be set to have a coefficient of thermal expansion that is larger than that of the front surface F2through formation of a layer of a good conductor having a coefficient of thermal expansion that is larger than that of the elastic lever member on the back surface F1of the cantilever1.

Moreover, the back surface F1may be set to have a coefficient of thermal expansion that is larger than that of the front surface F2through formation of a layer of a good conductor having a coefficient of thermal expansion that is smaller than that of the elastic lever member on the front surface F2of the cantilever1.

Modification Example of Third Embodiment

As a modification example of the third embodiment, there may be included a light control element91configured to control the illumination intensity of the laser light L1with which the reflecting surface of the back surface (first surface) F1of the cantilever1is irradiated by the light illuminator31. In this case, the illumination intensity of the laser light L1is controlled by the light control element91, and hence the output of the light illuminator31may be constant. In other words, in the modification example of the third embodiment, it is not required to control the output of the light illuminator31by the laser controller72C as opposed to the third embodiment. A scanning probe microscope C′ according to the modification example of the third embodiment and the scanning probe microscope C according to the third embodiment are identical in that the heating device4is not provided, and in that the cantilever1is thermally deformed with the light illuminator31. It should be noted, however, that in the scanning probe microscope C according to the third embodiment, the output of the light illuminator31is controlled to change the illumination intensity of the laser light L1and thermally deform the cantilever1, while the scanning probe microscope C′ according to the modification example of the third embodiment is different in that the output of the light illuminator31is set constant, and in that the illumination intensity of the laser light L1is changed by the light control element91to thermally deform the cantilever1. Other operation of the intermittent measurement method of the scanning probe microscope C′ is similar to the operation of the intermittent measurement method of the scanning probe microscope C.

Specifically, as illustrated inFIG. 12, the scanning probe microscope C′ includes a cantilever1, a movement driver2, a displacement detector3, a light control element91, and a control device5C′.

The light control element91is configured to control the illumination intensity of the laser light L1with which the reflecting surface of the back surface (first surface) F1of the cantilever1is irradiated by the light illuminator31, and is an acousto-optic modulator or an electro-optic modulator, for example.

The control device5C′ includes a determiner6, a controller7C′, and a measurement unit8. The controller7C′ includes a driver71and a laser controller72C′.

The laser controller72C′ is configured to output a control signal to the light control element91, to thereby control and drive the light control element91and control the illumination intensity of the laser light L1. In other words, the light control element91can change the temperature of the back surface F1of the cantilever1to deform the back surface F1by increasing or reducing the intensity of the laser light L1, which is applied by the light illuminator31, in accordance with the control signal from the laser controller72C′. In this manner, the light control element91controls the intensity of the laser light L1, which is applied by the light illuminator31, to control the deformation of the cantilever1due to the change in temperature thereof.

Specifically, when executing the first separating operation after the determiner6determines that the probe1ais brought into contact with the sample surface, the light control element91weakens the illumination intensity of the laser light L1, which is applied by the light illuminator31, from the first illumination intensity to the second illumination intensity in accordance with the control signal from the laser controller72C′. As a result, the back surface F1of the cantilever1that has been expanded is contracted with a reduction in temperature. In other words, the cantilever1is thermally deformed upward (+Z) toward the back surface F1side. Therefore, as in the third embodiment, the first separating operation is started with this thermal deformation.

As a result, as compared to the third embodiment, the illumination intensity of the laser light L1, which is applied by the light illuminator31, can be controlled more easily.

Fourth Embodiment

Now, a scanning probe microscope D according to a fourth embodiment of the present invention is described with reference to the drawings. The scanning probe microscope D according to the fourth embodiment is an apparatus configured to detect displacement of the cantilever1by a self-sensing method using a piezoresistor, and is different from the embodiments described above in that the cantilever1is thermally deformed with the use of the above-mentioned piezoresistor provided to the cantilever1.

FIG. 13is a diagram for illustrating an example of a schematic configuration of the scanning probe microscope D according to the fourth embodiment. As illustrated inFIG. 13, the scanning probe microscope D includes a cantilever1, a movement driver2, a displacement detector3D, and a control device5D.

The displacement detector3D is provided to the cantilever1to detect displacement of the deformation amount of the cantilever1. The displacement detector3D is configured to detect the displacement of the cantilever1not by the optical lever method but on the basis of a value of resistance of the piezoresistor. Now, a configuration of the displacement detector3D is described with reference toFIG. 14.

As illustrated inFIG. 14, the displacement detector3D includes a piezoresistor31D, a first electrode32D, and a second electrode33D.

The piezoresistor31D is provided on the front surface F2of the cantilever1. The piezoresistor31D is changed in value of resistance depending on a displacement amount of the cantilever1.

The first electrode32D is provided on the front surface F2of the cantilever1, and is electrically connected to a first end of the piezoresistor31D. The first electrode32D is also electrically connected to the control device5D.

The second electrode33D is provided on the front surface F2of the cantilever1, and is electrically connected to a second end of the piezoresistor31D. The second electrode33D is also electrically connected to the control device5D.

Next, the control device5D in the fourth embodiment is described.

As illustrated inFIG. 13, the control device5D includes a determiner6D, a controller7D, and a measurement unit8.

The determiner6D is connected to each of the first electrode32D and the second electrode33D. The determiner6D is configured to determine whether the probe1ais brought into contact with the sample surface by detecting the change in value of resistance of the piezoresistor31D. In other words, the determiner6D is configured to perform the contact determination processing on the basis of the change in value of resistance of the piezoresistor31D.

Specifically, the determiner6D detects an electric current (hereinafter referred to as a “displacement detection current”) flowing through the piezoresistor31D when a voltage is applied between the first electrode32D and the second electrode33D, and determines whether the probe1ais brought into contact with the sample surface on the basis of the detected displacement detection current.

The controller7D applies a suitable voltage between the first electrode32D and the second electrode33D.

Moreover, the controller7D is configured to control a relative movement amount between the probe1aand the sample S. As in the first embodiment, the scanning probe microscope D uses an intermittent measurement method, in which the sample surface is intermittently scanned by bringing the probe1ainto contact with only a plurality of preset measurement points on the sample surface. Therefore, the controller7D is configured to control each of the following operations: an approaching operation of bringing the probe1acloser to the measurement position; a separating operation of separating the probe1aand the sample S from each other; and a movement operation of moving the probe1ato above the next measurement position.

Now, a configuration of the controller7D is described. The controller7D includes a driver71and an energization controller72D.

The energization controller72D is configured to energize the piezoresistor31D by applying the voltage between the first electrode32D and the second electrode33D. Moreover, the energization controller72D is configured to control the voltage to be applied between the first electrode32D and the second electrode33D, to thereby to able to control the electric current to flow through the piezoresistor31D. The piezoresistor31D generates heat by being energized by the energization controller72D. In other words, the front surface F2of the cantilever1is heated and thermally deformed by being energized by the piezoresistor31D. Therefore, the energization controller72D can change a temperature of the front surface F2of the cantilever1and thermally deform the front surface F2by changing the voltage to be applied between the first electrode32D and the second electrode33D. In other words, the energization controller72D is configured to control the voltage to be applied between the first electrode32D and the second electrode33D, to thereby control the deformation of the cantilever1due to the change in temperature thereof.

Now, a flow of the intermittent measurement method of the scanning probe microscope D according to the fourth embodiment is described with reference toFIG. 15. As the initial conditions, a case is assumed in which the probe1ais positioned at a measurement descending position of a predetermined measurement point.

The energization controller72D energizes the piezoresistor31D by applying a first voltage between the first electrode32D and the second electrode33D (Step S401). The purpose of energizing the piezoresistor31D by applying the first voltage is to generate the displacement detection current for detecting the displacement of the cantilever1, and not to thermally deform the cantilever1.

When the piezoresistor31D is energized, the driver71outputs the approaching operation signal to the Z-direction drive unit21to start the approaching operation (Step S402).

When the approaching operation is started by the driver71, the determiner6D executes the contact determination processing, in which the electric current flowing through the piezoresistor31D is detected as the displacement detection current, and it is determined whether the probe1ais brought into contact with the sample surface on the basis of a value of the detected displacement detection current (Step S403).

When the determiner6D determines that the probe1aand the sample surface are brought into contact with each other, the driver71stops outputting the approaching operation signal to stop the approaching operation (Step S404). In this case, the probe1ais in contact with the sample surface, and hence the cantilever is twisted or deformed by a predetermined amount or more. Then, the measurement unit8measures the irregular shapes on the sample surface by measuring the relative distance under the state in which the approaching operation is stopped (Step S405).

When the measurement of the relative distance by the measurement unit8is complete, the controller7D starts the separating operation, in which the sample S and the probe1aare separated from each other.

Specifically, the energization controller72D applies a second voltage, which is higher than the first voltage, between the first electrode32D and the second electrode33D to energize and heat the piezoresistor31D. As a result, an electric current that is larger than the displacement detection current is allowed to flow through the piezoresistor31D, and the piezoresistor31D generates heat. Therefore, the front surface F2of the cantilever1is heated by the heat generated by the piezoresistor31D, and is heated and expanded. As a result, the cantilever1is thermally deformed to be warped upward (+Z) toward the back surface F1side, and the separating operation is started (Step S406).

The response speed of the thermal deformation is far faster than the response speed of the piezoelectric element. In other words, the response speed of the separating operation (first separating operation) through the thermal deformation of the cantilever1is far faster than the response speed of the separating operation (second separating operation) by the Z-direction drive unit21(fine movement mechanism). Therefore, in the fourth embodiment, not the Z-direction drive unit21but the piezoresistor31D is energized and heated to thermally deform the self-sensing cantilever1and start the separating operation (first separating operation). As a result, the measurement time of the irregular shapes on the sample surface is reduced.

Simultaneously with the start of the first separating operation through the thermal deformation of the cantilever1, the driver71outputs the separating operation signal to the Z-direction drive unit21to start the second separating operation, in which the sample S is moved in the direction of being separated from the probe1a(Step S407). Even when both of the separations are started simultaneously, the operation is performed as follows: the separation through the thermal deformation, which is fast in response, leads, and the separation with the fine movement mechanism, which is slow in response, follows. Both of the above-mentioned separating operations are executed for the predetermined time, and are then ended (Step S408). The “predetermined time” is up to a timing when the Z fine movement mechanism responds by an amount that is equivalent to the deformation amount of the thermal deformation or more.

When the first separating operation and the second separating operation are stopped, the controller7D outputs the drive signal to the XY scanner22to move the probe1ato the measurement descending position located immediately above the next measurement position (Step S409). Then, the controller7D performs the operation of from Step S401to Step S409also at the next measurement position. In other words, the scanning probe microscope D performs the operation of from Step S401to Step S409for each measurement point on the sample S, to thereby intermittently scan the sample surface.

As described above, the scanning probe microscope D according to the fourth embodiment executes the separating operation by thermally deforming the cantilever1. As a result, the scanning probe microscope D provides an effect similar to the first embodiment that the measurement time is significantly reduced.

Moreover, the scanning probe microscope D according to the fourth embodiment is the apparatus configured to detect the displacement of the cantilever1by the self-sensing method using the piezoresistor, in which the heating device4is not provided, and the cantilever1is thermally deformed through energization and heating of the piezoresistor. As a result, it is not required to add the heating device4to thermally deform the cantilever1, and the cost is thus reduced.

Moreover, in the scanning probe microscope D, the cantilever1may be configured such that an expansion coefficient of the front surface F2is larger than a coefficient of thermal expansion of the back surface F1, for example. The front surface F2may be set to have a coefficient of thermal expansion that is larger than that of the back surface F1through formation of a layer of a good conductor having a coefficient of thermal expansion that is larger than that of the back surface F1on the front surface F2of the cantilever1, for example. The back surface F1is formed of Si, and the front surface F2is formed of A1, for example. Wiring of the displacement detector3D provided on the front surface F2may be formed of A1, for example.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configurations are not limited to those of the embodiments, and the present invention also encompasses design modifications and the like without departing from the gist of the present invention.