JP2005283540A - Scanning probe microscope and method for measuring sample surface shape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning probe microscope that can easily scan a probe in XY directions, can perform control for bringing the probe closer to a sample surface, and can measure the undercut structural section of a sample. <P>SOLUTION: A means for inclining the travel axis of the probe for bringing the probe closer to the sample surface is composed of an XY scanning body 22 and a Z scanning support 23. Then, the lower surface section of the XY scanning body 22 is formed into an arc shape curved inside, the upper surface of the Z scanning support 23 is formed into an arc shape sliding along the lower surface section of the XY scanning body 22, and the Z scanning support 23 is slidably suspended along the lower surface section of the XY scanning body 22. A cantilever 13 is arranged so that the tip of the probe 12, whose tip is fixed, is positioned at the center of a circle formed by the arc on the lower surface section of the XY scanning body 22, the angle formed by the direction of the cantilever 13 and a surface in parallel with the sample surface is maintained to be the same, and the direction of the cantilever 13 can be inverted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a scanning probe microscope that measures the three-dimensional surface structure of a sample with nanometer accuracy, and a sample surface shape measuring method using the scanning probe microscope.

  Technological innovations are constantly being made in the miniaturization technology of semiconductor integrated circuit elements and wiring, and the minimum processing dimension has now progressed to a level of less than 100 nm. The technology that supports the microfabrication is an etching technology. By the etching technique, innumerable trenches (deep grooves) are formed in the semiconductor integrated circuit, and contact holes having a large aspect ratio (depth / opening diameter) are formed. The side walls of such trenches and contact holes are almost vertical.

  When such a vertical side wall is excessively etched, the side wall has an undercut or overhang structure. Excessive etching is a measure of defective or unstable etching processes, except when undercut or overhang structures are actively used as device structures. Therefore, the stability of the etching process can be monitored by observing the presence or degree of the undercut or overhang structure.

  However, the cross-sectional structure of the undercut or overhang structure cannot be observed with a conventional scanning probe microscope in which a probe is inserted from above the sample. In the case of observing, there is no other way than observing the cross section with a scanning electron microscope after cutting out the cross section with a FIB (Focused Ion Beam) apparatus, for example. However, since this method is a method of observing a sample by destroying it, it cannot be applied for the purpose of monitoring the manufacturing process. Therefore, the scanning probe microscope needs to be able to measure the undercut structure portion.

  Patent Documents 1 and 2 disclose an example of a scanning probe microscope in which an undercut structure portion of a sample can be observed by tilting the probe or the sample. If the probe or sample is tilted, the tilt becomes relatively gentle, so that the undercut structure portion can be observed. However, in the scanning probe microscopes disclosed in Patent Document 1 and Patent Document 2, while the probe is in contact with or almost in contact with the surface of the sample, the sample surface shape is scanned while scanning in a direction parallel to the surface of the sample. Measure.

  When the sample surface is scanned with the probe in contact with or almost in contact with the sample surface, if there is a steep mountain or groove climbing slope in the scanning direction, a large amount of friction is generated between the probe and the sample surface. The tip of the probe was bent or slipped due to the friction. Therefore, the information on the surface shape of the sample measured at that time has to be large in error. In addition, the probe often breaks due to bending due to friction.

Further, Patent Document 3 discloses an example of a scanning probe microscope that has improved the drawbacks that a measurement error increases and a probe breaks. According to the method for measuring the surface shape of the sample of the scanning probe microscope, the scanning of the probe in a plane along the surface of the sample is performed at a position away from the surface of the sample, and the probe is moved from that position to the sample surface. The surface shape of the sample is measured by approaching the surface. Therefore, the probe does not bend or slide and is not broken. However, Document 3 does not describe anything about measuring the undercut structure portion by inclining the probe or the sample.
JP 2000-97840 A (paragraphs [0009] to [0014], FIGS. 5 and 7) JP 2000-275260 A (paragraph [0010] to paragraph [0055], FIGS. 1 to 5) JP 2003-227788 A (paragraph [0018] to paragraph [0042], FIGS. 1 to 9)

  Therefore, if the measuring method described in Patent Document 3 is applied to the scanning probe microscope described in Patent Document 1 or Patent Document 2, the disadvantages of the scanning probe microscope described in Patent Document 1 or Patent Document 2 are eliminated. be able to. However, if the measurement method described in Patent Document 3 is applied to the scanning probe microscope described in Patent Document 1 or Patent Document 2 as it is, the following problem occurs.

  In the scanning probe microscopes described in Patent Document 1 and Patent Document 2, an angle formed between an XY plane (a surface along the surface of the sample) and a Z direction (a direction in which the probe approaches or separates from the surface of the sample) (usually , Vertical) is a structure that remains fixed even when the probe or sample is tilted. Therefore, if the probe is to approach the surface of the sample obliquely from above, it is necessary to simultaneously perform control for driving in the X direction and control for driving in the Z direction, which complicates the control. Further, when the Z direction is aligned with the direction in which the probe moves obliquely, the X direction deviates from the surface along the surface of the sample, so that the control of scanning on the surface along the surface of the sample becomes complicated.

  In view of the above-described problems of the prior art, the object of the present invention is to perform scanning on the XY plane of the probe at a position separated from the surface of the sample, and bring the probe closer to the surface of the sample from the separated position. A scanning probe microscope equipped with a surface shape measuring method for measuring the surface shape of a sample, which can easily control scanning of the probe in the XY directions and control the probe to approach the surface of the sample. An object of the present invention is to provide a scanning probe microscope capable of measuring an undercut structure portion.

  In order to solve the above-mentioned problem, in the invention according to claim 1, the scanning probe microscope includes a sample stage on which a sample to be measured is placed, a direction parallel to the upper surface of the sample stage, and a direction approaching or retracting. And a cantilever with a probe fixed to the tip of the cantilever, and the probe and the cantilever in a predetermined direction parallel to the sample surface at a position separated from the sample surface by a predetermined distance or more. XY direction probe moving means to be moved in the direction of movement, and in a state where movement of the probe and cantilever by the XY direction probe moving means is stopped, the probe is moved in a direction to approach or retract the sample surface. Z-direction probe moving means, force detection means for detecting a force received from the surface of the sample when the probe approaches the surface of the sample, and a method in which the Z-direction probe moving means moves the probe And a Z-direction axis inclining means for inclining the probe movement Z-direction axis with respect to the normal direction of the plane parallel to the surface of the sample, with the straight line passing through the tip of the probe as the axis of the probe movement Z-direction. The configuration.

  In the scanning probe microscope according to the first aspect of the present invention, the XY direction probe moving means scans the probe in the XY direction at a position separated from the surface of the sample by a predetermined distance or more. Therefore, the probe does not receive frictional force or hits a crest on the surface of the sample during scanning in the XY directions, so that the probe is not broken.

  The Z-direction probe moving means brings the probe close to the surface of the sample in a state where the XY-direction probe moving means is not operating. The force detecting means detects the atomic force received from the surface of the sample when the probe approaches the surface of the sample, and determines the surface position of the sample when the force reaches a predetermined value. That is, after the movement in the XY directions is stopped, the probe is brought close to the surface of the sample from above the sample to measure the surface shape of the sample. Therefore, since the probe does not receive the frictional force accompanying the scanning in the XY directions, the probe does not bend even on a steep slope on the surface of the sample, and the surface shape of the sample can be measured with high accuracy. Can do.

  Further, the Z direction axis tilting means tilts the direction in which the Z direction probe moving means moves the probe. Therefore, the probe can approach the surface of the sample not only from directly above the surface of the sample but also from obliquely above. As a result, the shape of the undercut structure portion on the surface of the sample can be measured.

  According to a second aspect of the present invention, the Z direction axis tilting means in the scanning probe microscope according to the first aspect is configured to tilt the probe moving Z direction axis so as to rotate about the tip of the probe. did. Therefore, the tip position of the probe does not change even if the inclination angle of the probe movement Z direction axis is changed. Therefore, even when measuring the shape of the surface of the same part of the sample surface by changing the tilt angle of the probe movement Z-direction axis, the probe can be easily and accurately aligned. Will be able to do.

  In the invention according to claim 3, the scanning probe microscope is configured such that the angle formed by the direction in which the cantilever faces and the plane parallel to the surface of the sample is formed in the configuration of the scanning probe microscope according to claim 1 or 2. A cantilever direction reversing means for reversing the direction of the cantilever while keeping the same is provided.

  In the scanning probe microscope according to claim 3, when the cantilever direction reversing means reverses the direction of the cantilever when the probe moving Z direction axis is inclined, the probe is moved before and after the reversal. The tilt angle approaching the sample surface is reversed. Accordingly, not only the undercut structure portion opened in a specific direction but also the surface shape of the undercut structure portion opened in the opposite direction can be measured.

  According to a fourth aspect of the present invention, in the scanning probe microscope according to any one of the first to third aspects, the Z-direction axis tilting means is moved by the XY-direction probe moving means, An XY scanning body having a curved arc-shaped cross-section lower surface, and an XY scanning body having an arc-shaped cross-sectional upper surface that slides on the curved arc-shaped cross-section of the XY scanning body. A Z scanning support suspended on the lower surface slidably along the arc, and a cantilever support suspended on the lower surface of the Z scanning support so as to be movable by a Z-direction probe moving means; It comprised so that it might be equipped with. Further, the cantilever is fixed to the cantilever support so that the tip of the probe fixed to the tip is located at the center of a circle formed by the arc of the bottom cross section of the XY scanning body. .

  In the scanning probe microscope according to claim 4, since the upper surface of the Z scanning support slides in a state where the upper surface of the Z scanning support slides on the curved arc of the lower surface of the XY scanning body, the Z scanning support does not move around the center of the arc. Rotate as a point. Here, the cantilever is fixed to the cantilever support so that the tip of the probe is positioned at a fixed point of rotation. Accordingly, the probe movement Z-direction axis is tilted around the tip of the probe by sliding the Z-scan support along the curved lower surface of the XY scan. Further, even if the Z scanning support is tilted to tilt the probe movement Z direction axis, the Z direction probe moving means is tilted at the same time, but the XY scanning body is not tilted. Therefore, the movement control of the probe in the tilted Z direction can be easily performed only by the Z direction probe moving means, and the XY direction does not deviate from the surface along the surface of the sample.

  In the invention of claim 5, the XY scanning body in the scanning probe microscope of claim 4 is moved by the XY direction probe moving means, and the XY scanning support body is in a plane in the XY direction. And an XY scanning rotator having a lower surface with an arc-shaped cross section that is suspended at least 180 degrees and is curved inward. The rotation axis of the XY scanning rotator was made to coincide with the probe movement Z direction axis when the probe movement Z direction axis was a normal direction of a plane parallel to the surface of the sample.

  In the scanning probe microscope according to claim 5, when the XY scanning rotator is rotated 180 degrees, the direction of the cantilever is reversed. At this time, the rotation axis of the XY scanning rotator is set to coincide with the probe movement Z direction axis when the probe movement Z direction axis is the normal direction of the plane parallel to the surface of the sample. The direction of the cantilever can be reversed without changing the tip position of the needle.

  According to a sixth aspect of the present invention, in the scanning probe microscope according to any one of the first to fifth aspects, a method for measuring the sample surface shape is the probe movement Z direction axis on the surface of the sample. In the normal direction of the parallel plane, the probe is moved by a predetermined minute distance from a predetermined initial position in a predetermined XY direction by the XY direction probe moving means to be stopped, and the movement in the XY direction is stopped. The normal incidence measurement step for measuring the sample surface shape by bringing the probe close to the surface of the sample while stopping the movement in the XY direction at each position to be performed, and the normal direction measurement step for the probe The measurement is returned to the initial position where the measurement is started, the probe movement Z direction axis is inclined with respect to the normal direction of the plane parallel to the surface of the sample, and the probe is moved in the predetermined XY direction by the XY direction probe moving means. Move from the position by a predetermined minute distance At each position where the movement in the XY direction stops, the incidence of the sample surface is measured by moving the probe close to the surface of the sample while stopping the movement in the XY direction. A measurement step, a surface shape data merging step for obtaining surface shape data from data obtained by merging the sample surface shape data measured in the normal incidence measurement step and the sample surface shape data measured in the oblique incidence measurement step It was configured as follows.

  The sample surface shape measurement method according to claim 6, wherein the sample surface shape data is obtained by combining the sample surface shape data measured in the normal incidence measurement step and the sample surface shape data measured in the oblique incidence measurement step. Therefore, a more accurate sample surface shape including the undercut structure portion can be measured.

  According to the seventh aspect of the present invention, the sample surface shape measurement method is the sample surface shape measurement method according to the sixth aspect of the present invention, and after performing the oblique incidence measurement step, the probe is further measured in the normal direction. The measurement is returned to the initial position where measurement is started in step, the direction of the cantilever and the probe movement Z direction axis are reversed by the cantilever reversing means, and the probe is moved to the predetermined initial position in the predetermined XY direction by the XY direction probe moving means. The sample is moved by the predetermined minute distance from the stop and stopped, and at each position where the movement in the XY direction stops, the probe is brought close to the surface of the sample while the movement in the XY direction is stopped. A reverse tilt incidence measurement step for measuring the surface shape is performed. In the surface shape data merging step, the sample surface shape data measured in the normal incidence measurement step is To the measured sample surface shape data in the incident measurement step, and to obtain the sample surface shape data by further addition merged with data of the sample surface shape data measured by reverse oblique incidence measuring step.

  In the sample surface shape measurement method according to claim 7, in addition to the sample surface shape data measured in the normal incidence measurement step and the sample surface shape data measured in the gradient incidence measurement step, Since the sample surface shape data is obtained based on the data obtained by merging the measured sample surface shape data, the sample surface shape including the undercut structure portion opened in both directions as well as in one direction can be measured more accurately.

  According to the scanning probe microscope of any one of claims 1 to 5, even if there are steep peaks and valleys on the surface of the sample, the probe does not bend or break, and a highly accurate sample can be obtained. Surface shape can be measured. Further, the moving axis for bringing the probe closer to the surface of the sample can be inclined, and the shape of the undercut structure portion on the surface of the sample can be measured. Further, even if the movement axis for bringing the probe closer to the surface of the sample is tilted, the control for moving the probe is not complicated.

  According to the sample surface shape measuring method according to claim 6 or 7, the sample surface shape is measured by bringing the probe close to the surface along a plurality of inclination angles, and the sample surface obtained by the measurement is measured. Since the shape data is merged, the sample surface shape including the undercut structure portion can be measured with high accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

  First, the configuration of functional blocks of the scanning probe microscope and the principle of surface shape measurement will be described. FIG. 1 is a diagram showing a configuration example of functional blocks of a scanning probe microscope according to an embodiment of the present invention.

  In FIG. 1, an XY sample stage 10 is a mounting table for mounting a sample 11 to be measured on its upper surface, and moves roughly in the XY direction. The scanning control circuit 36 controls the coarse movement of the XY sample stage 10 and drives the piezoelectric element X, the piezoelectric element Y, and the piezoelectric element Z. The piezoelectric element X, the piezoelectric element Y, and the piezoelectric element Z move the cantilever 13 in the X direction, the Y direction, and the Z direction, respectively. Here, the X direction and the Y direction are directions parallel to the upper surface of the XY sample stage 10, that is, the surface of the sample 11, and the Z direction is a direction in which the probe 12 approaches or retracts from the surface of the sample 11.

  One end of the cantilever 13 is cantilevered by the piezoelectric element X, the piezoelectric element Y, and the piezoelectric element Z, and the probe 12 is fixed to the other open end. The excitation piezoelectric element 14 is fixed to the cantilever 13 on the side where the cantilever 13 is supported, and is driven by a high-frequency signal from the oscillator 30 to vibrate the cantilever 13.

  The laser light emitting element 31, the position detector 32, and the force detection circuit 33 constitute a so-called optical lever type force detector. When the probe 12 approaches the surface of the sample 11, the probe 12 receives an atomic force from the sample 11, and the cantilever 13 is bent by the atomic force. The laser light emitted from the laser light emitting element 31 and reflected by the cantilever 13 is displaced in its light receiving position by the bending of the cantilever 13. The position detector 32 detects the light receiving position. The force detection circuit 33 receives the output of the position detector 32, obtains the amount of displacement of the light receiving position, and outputs a signal corresponding to the force received by the probe 12.

  The lock-in amplifier 34 receives the output of the force detection circuit 33 and the output of the oscillator 30 and plays a role of detecting the gradient of the force received by the probe, as will be described later. The servo circuit 35 drives the piezoelectric element Z according to the output of the lock-in amplifier 34 and the instruction data from the control unit 37, and controls the position of the probe in the Z direction.

  The control unit 37 is a computer including an arithmetic processing unit (not shown), a storage device including a semiconductor memory and a disk device, and an input / output device such as a keyboard and a liquid crystal display device, and further includes a servo circuit 35 and a scanning control circuit. 36 interface. Then, the servo circuit 35 and the XY scanning control circuit 25 are appropriately controlled according to the program stored in the storage device. Further, the force gradient signal detected by the lock-in amplifier 40 is appropriately converted into digital data and is captured and stored in the storage device.

  Next, the principle of detecting the surface of the sample 11 will be described.

  When the probe 12 receives a force from the surface of the sample 11, the cantilever 13 bends. At this time, since the cantilever 13 can be regarded as an elastic body, the amount of bending thereof is proportional to the force received by the probe 12. Therefore, the output of the force detection circuit 33 corresponds to the force received by the probe 12. Therefore, the surface position of the sample 11 can be determined when the output of the force detection circuit 33 reaches a predetermined value.

  As described above, the surface position of the sample 11 can be detected by the output of the force detection circuit 33. In the present embodiment, the sample 11 is measured by measuring the gradient of the atomic force on the surface of the sample 11. Use a method to detect the surface position of the. The method of detecting the surface of the sample 11 by the atomic force gradient can detect the surface with a force several orders of magnitude smaller than the method of detecting the surface of the sample 11 by the atomic force itself. The burden is reduced, and the phenomenon that the probe is bent or slipped can be avoided.

  It is known that the gradient of atomic force is obtained by utilizing the phenomenon that the resonance frequency of the cantilever shifts. Therefore, a high frequency signal having a frequency slightly different from the resonance frequency of the cantilever 13 is oscillated by the oscillator 30, and the excitation piezoelectric element 14 is driven by the high frequency signal. The cantilever 13 is vibrated by the vibrating piezoelectric element 14 and vibrates in the Z direction with an amplitude of about several nm to several tens of nm.

  Thus, when the probe 12 is brought close to the surface of the sample 11 while the cantilever 13 is oscillating, the resonance frequency shifts due to the gradient of the atomic force. Therefore, the vibration amplitude of the cantilever 13 changes, and the changed amount is captured as the output of the lock-in amplifier 34. The output of the lock-in amplifier 34 corresponds to the gradient of the atomic force that the probe 21 receives. Therefore, when the atomic force gradient reaches a predetermined value, it can be determined that the probe 12 has reached the surface of the sample 11.

  In FIG. 1, the output of the lock-in amplifier 34 is input to the servo circuit 35. The servo circuit 35 takes the difference between the value input from the lock-in amplifier 34 and the predetermined value input from the control unit 37, and drives the piezoelectric element Z until the difference becomes zero. Therefore, the probe 12 approaches the surface of the sample 11 until the output of the servo circuit 35 becomes zero, and when the output of the servo circuit 35 becomes zero, the approach is stopped and the position thereof is changed to the surface of the sample 11. Judge as position.

  Next, a configuration in which the probe 12 is inclined in the direction in which the probe 12 approaches or retracts from the surface of the sample 11 will be described. FIG. 2 is a schematic diagram showing an example of the configuration for scanning the probe and the configuration for tilting the Z-direction axis in the present embodiment.

  In the present embodiment, the X-direction axis and the Y-direction axis are set in a direction parallel to the upper surface of the XY sample stage 10, that is, the surface of the sample 11, but the Z-direction axis is the probe 12 on the surface of the sample 11. It is set in a direction parallel to the approaching or retracting direction. Therefore, the coordinate system in the present embodiment is not necessarily an orthogonal coordinate system, and the direction of the Z-direction axis may change every time the surface shape of the sample 11 is measured. Here, among the settable Z direction axes, the Z direction axis passing through the tip of the probe is particularly referred to as a probe movement Z direction axis.

  In FIG. 2, an XY scanning body 22 is a structure that scans the probe 12 in the X direction and the Y direction. The XY scanning body 22 is suspended from a housing of a scanning probe microscope (not shown), and the X scanning piezoelectric element 20 and the Y scanning. The piezoelectric element 21 is moved in the X direction and the Y direction, respectively. The lower surface of the XY scanning body 22 has an arc shape whose cross section is curved inward. The Z scanning support 23 has an upper surface with an arcuate cross section that slides on the lower surface of the curved arcuate cross section of the XY scanning body 22, and is along the lower surface of the curved arcuate cross section of the XY scanning body 22. And is slidably suspended. Therefore, the Z scanning support 23 is inclined with the center of the circle formed by the circular arc of the bottom cross section of the XY scanning body 22 as a fixed point.

  The lower surface of the Z scanning support 23 is formed to be a surface perpendicular to the diameter direction of the circle formed by the circular arc of the lower cross section of the XY scanning member 22, and the Z scanning piezoelectric element 24 and the cantilever support 25 are formed on the lower surface thereof. The Z scanning piezoelectric element 24 is provided to move the cantilever support 25 in a direction perpendicular to the lower surface of the Z scanning support 23. Therefore, the direction in which the cantilever support 25 is moved is the Z direction.

  One end of the cantilever 13 is fixed to the cantilever support 25, and the other end is an open end. Further, the probe 12 is fixed to a surface facing the surface of the sample 11 at the open end of the cantilever 13. At this time, the cantilever 13 is fixed to the cantilever support 25 at a position where the tip of the probe 12 is positioned at the center of a circle formed by the arc of the lower surface cross section of the XY scanning body 22.

  As described above, the XY scanning body 22 and the Z scanning support body 23 are configured, and the cantilever 13 and the cantilever support body 25 are arranged and configured with respect to the Z scanning support body 23, whereby the probe 12 moves in the Z direction. Direction, that is, the probe movement Z-direction axis (dashed line indicated by reference numeral 15 in FIG. 2) is inclined at an angle θ with respect to the normal direction of the surface of the sample (dashed line indicated by reference numeral 16 in FIG. 2). Can be made. Therefore, since the probe 12 can be made to approach the surface of the sample 11 from obliquely above the sample 11, the surface shape of the undercut structure portion can be measured. In addition, since the tip of the probe 12 is the center point for inclining the probe movement Z direction axis, the position of the tip does not change even if the inclination angle θ is changed.

  Next, a configuration in which the direction of the cantilever 13, that is, the probe movement Z-direction axis (dashed line 15) is reversed by 180 degrees with respect to the normal direction of the sample surface (dashed line 16) will be described. 3A and 3B are schematic views showing an example of the configuration of the XY scanning body for reversing the direction of the cantilever. FIG. 3A is a cross-sectional view of the XY scanning body, and FIG. 3B is a top view of the XY scanning body. It is.

  As shown in FIGS. 3A and 3B, the XY scanning body 22 is mainly composed of an XY scanning support body 221 and an XY scanning rotating body 222. The XY scanning support 221 is suspended from a housing of a scanning probe microscope (not shown) and is moved in the X direction and the Y direction by the X scanning piezoelectric element 20 and the Y scanning piezoelectric element 21, respectively. Further, the XY scanning rotator 222 is suspended from the XY scanning support 221 so as to be rotatable at least 180 degrees in a plane in the XY direction, and has an arc-shaped cross-section lower surface curved inward. A Z scanning support 23 (see FIG. 2) is suspended from the lower surface of the arcuate cross section curved inwardly.

  The XY scanning support body 221 is formed in a disc shape, and an engaging protrusion 221a is formed on the peripheral edge thereof. On the other hand, the XY scanning rotator 222 is formed of a thick disk, and a lower surface thereof is formed with a concave portion having an arcuate cross section that is curved inward, and an upper portion thereof accommodates the entire XY scanning support 221. Possible cylindrical recesses are formed. The XY scanning support 221 is accommodated in the recess, and the space above the engagement protrusion 221a is closed by the locking ring 223. The locking ring 223 is fixed to the inner wall surface of the recess of the XY scanning rotator 222. A ball bearing 224 is disposed at a portion where the XY scanning support 221 contacts the XY scanning rotator 223 and the locking ring 223 so as to reduce friction during rotation.

  By configuring the XY scanning body 22 as described above, the XY scanning rotating body 222 can be freely rotated. Therefore, the Z scanning support 23, the cantilever support 25 and the cantilever 13 suspended from the XY scanning rotator 222 are rotated simultaneously with the rotation of the XY scanning rotator 222. Therefore, the cantilever 13 can be inverted 180 degrees. In order to securely stop the XY scanning rotator 222 at a position where the XY scanning rotator 222 is reversed by 180 degrees, a locking mechanism may be provided as appropriate at positions of 0 degrees and 180 degrees.

  Next, a sample surface shape measuring method using the scanning probe microscope of the present embodiment will be described with reference to FIGS. 4 and 5. Here, FIG. 4 is a diagram showing the movement trajectory of the probe at the time of measuring the sample surface shape. FIG. 4A shows the probe movement when the axis of the probe movement Z direction is the normal direction of the XY plane. FIG. 5B is a diagram showing the movement locus of the probe when the probe movement Z direction axis is inclined with respect to the normal direction of the XY plane. FIG. 5 shows surface shape data when the probe movement Z direction axis is the normal direction of the XY plane and when the probe movement Z direction axis is inclined with respect to the normal direction of the XY plane. It is a figure for demonstrating the calculation method of.

  In FIG. 4A, first, the probe movement Z direction axis is set to the normal direction of the XY plane, and the surface shape of the sample 11 is measured. Then, the probe is set at an initial position that is separated from the surface of the sample 11 by a predetermined distance, and the probe is made to approach the surface of the sample along the probe movement Z-direction axis from the initial position (S1). The movement of the probe is performed by the Z scanning piezoelectric element 24 driven by the servo circuit 35 (see FIG. 1). At this time, the X scanning piezoelectric element 20 and the Y scanning piezoelectric element 21 are at rest.

When the servo circuit 35 stops driving the Z-scanning piezoelectric element 24, it is determined that the probe 12 has reached the surface position of the sample 11. The surface position can be obtained from the movement distance ΔZ of the probe 12 at that time. As shown in FIG. 5, when the coordinates of the initial position P are (X ₀ , Z ₀ ) and the movement distance at the time of measuring the surface position of the sample 11 is ΔZ, the coordinates of the surface position S are (X ₀ , Z ₀ -ΔZ).

  When the measurement of the surface position of the sample 11 is completed, the probe 12 is retracted by a predetermined distance (S2), and the probe is moved by ΔX in the X direction by the X scanning piezoelectric element 20 (S3). Then, steps S1 to S3 are repeated a predetermined number of times with the position after the movement as the initial position. Thus, the surface shape data about the cross section scanned in the X direction is acquired.

Next, the probe 12 is returned to the initial initial position, and as shown in FIG. 4B, the probe movement Z direction axis is inclined by a predetermined angle θ with respect to the normal direction of the XY plane. Then, the probe 12 is moved closer to the surface of the sample 11 from the initial position (S11), and the surface position of the sample is measured. At this time, assuming that the coordinates of the initial position P are (X ₀ , Z ₀ ) and the movement distance of the probe 12 is ΔZ ′, the coordinates of the surface position S ′ are (X ₀ + ΔZ′sin θ, Z ₀ −ΔZ ′ + cos θ). )

  When the measurement of the surface position of the sample 11 is completed, the probe 12 is retracted by a predetermined distance (S12), and the probe is moved by ΔX in the X direction by the X scanning piezoelectric element 20 (S13). Then, steps S11 to S13 are repeated a predetermined number of times with the position after the movement as the initial position. In this way, surface shape data is acquired for the cross section scanned in the X direction when the probe movement Z direction axis is tilted at a predetermined angle θ with respect to the normal direction of the XY plane. In this case, since the probe approaches the surface of the sample 11 from obliquely above, the undercut structure portion of the side wall opened to the right side can be measured in FIG.

  Further, the direction of the cantilever 13 is reversed, and the surface shape data is acquired in the same manner as in FIG. In this case, the probe movement Z-direction axis is a direction reversed symmetrically with respect to the normal line of the XY plane. Therefore, in this case, in the case of FIG. 4B, the undercut structure portion of the side wall opened to the left side can be measured.

  As shown in FIG. 5, the surface shape data obtained as described above is obtained as data of different point sequences, such as data of a dot sequence of white circles and data of a dot sequence of black circles. The data is data that complement each other, and when they are merged, more accurate surface shape data can be obtained. In the present embodiment, the tip position of the probe 12 does not move even if the probe movement Z direction axis is tilted or the direction of the cantilever 13 is reversed. Therefore, it is only necessary to merge these data.

  If the tip position of the probe is shifted due to a mechanical error when the probe movement Z direction axis is tilted or the direction of the cantilever 13 is reversed, the surface of the probe is moved according to the data of different point sequences. After creating shape data and pattern matching, the data are merged.

  As described above, according to the method for measuring the surface of the sample in the present embodiment, the shape of the surface of the sample having the undercut structure can be measured with higher accuracy.

It is the figure which showed the structural example of the functional block of the scanning probe microscope which concerns on embodiment of this invention. It is the schematic diagram which showed an example of the structure for scanning a probe and the structure for inclining a Z direction axis | shaft in this embodiment. It is the model which showed an example of the structure of the XY scanning body for reversing the direction of a cantilever, (a) is sectional drawing of an XY scanning body, (b) is a top view of an XY scanning body. It is the figure which showed the movement locus | trajectory of the probe at the time of sample surface shape measurement, (a) is the figure which showed the movement locus | trajectory of the probe when the probe movement Z direction axis | shaft is made into the normal line direction of XY plane. FIG. 6B is a diagram showing a probe trajectory when the probe movement Z-direction axis is inclined with respect to the normal direction of the XY plane. A method of calculating surface shape data will be described for each of the case where the probe movement Z direction axis is the normal direction of the XY plane and the case where the probe movement Z direction axis is inclined with respect to the normal direction of the XY plane. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 XY sample stage 11 Sample 12 Probe 13 Cantilever 14 Excitation piezoelectric element 20 X scanning piezoelectric element 21 Y scanning piezoelectric element 22 XY scanning body 23 Z scanning support body 24 Z scanning piezoelectric element 25 Cantilever support body 30 Oscillator 31 Laser emission Element 32 Position detector 33 Force detection circuit 34 Block-in amplifier 35 Servo circuit 36 Scan control circuit 37 Control unit 221 XY scan support 222 XY scan rotator 223 Locking ring

Claims (7)

A sample stage on which a sample to be measured is placed;
A cantilever provided movably in a direction parallel to the upper surface of the sample stage and in a direction approaching or retracting, and a probe fixed to the tip thereof;
XY direction probe moving means for moving the probe and the cantilever in a predetermined direction parallel to the surface of the sample at a position where the probe is separated from the surface of the sample by a predetermined distance or more;
Z-direction probe moving means for moving the probe toward or away from the surface of the sample while movement of the probe and the cantilever by the XY direction probe moving means is stopped; ,
Force detecting means for detecting a force received from the surface of the sample when the probe approaches the surface of the sample;
The Z-direction probe moving means is a straight line in the direction in which the probe is moved, and a straight line passing through the tip of the probe is defined as a probe movement Z-direction axis, and the probe movement Z-direction axis is parallel to the surface of the sample. And a Z-direction axis tilting means for tilting with respect to the normal direction of the smooth surface. The scanning probe microscope according to claim 1, wherein the Z-direction axis tilting unit tilts the probe movement Z-direction axis so as to rotate about the tip of the probe. The cantilever direction reversing means for reversing the direction of the cantilever while maintaining the same angle formed by the direction of the cantilever and a plane parallel to the surface of the sample is provided. Scanning probe microscope. The Z-direction axis tilting means is
An XY scanning body that has been moved by the XY direction probe moving means and has a lower surface with an arcuate cross section curved inward;
The upper surface of the arcuate cross section that slides on the lower surface of the curved arcuate cross section of the XY scanning body is suspended from the lower surface of the curved arcuate cross section of the XY scanning body so as to be slidable along the arc. Z scanning support,
A cantilever support suspended on the lower surface of the Z scanning support so as to be movable by the Z-direction probe moving means;
The cantilever is fixed to the cantilever support so that the tip of the probe fixed to the tip of the cantilever is positioned at the center of a circle formed by an arc of the bottom cross-section of the XY scanning body. The scanning probe microscope according to claim 1, wherein the scanning probe microscope is characterized in that: The XY scanning body is
An XY scanning support moved by the XY direction probe moving means;
An XY scanning rotator suspended from the XY scanning support so as to be rotatable at least 180 degrees in a plane in the XY direction, and having a lower surface with an arcuate cross section curved inwardly,
The rotation axis of the XY scanning rotator coincides with the probe movement Z-direction axis when the probe movement Z-direction axis is a normal direction of a plane parallel to the surface of the sample. Item 5. A scanning probe microscope according to Item 4. A method for measuring a sample surface shape in a scanning probe microscope according to any one of claims 1 to 5,
The probe movement Z direction axis is a normal direction of a plane parallel to the surface of the sample, and the probe is moved in a predetermined minute distance from a predetermined initial position in a predetermined XY direction by the XY direction probe moving means. At each position where the movement in the XY direction stops, the probe is brought close to the surface of the sample while stopping the movement in the XY direction at each position where the movement in the XY direction stops. A normal incidence measurement step for measuring, and
The probe is returned to the initial position where measurement was started in the normal incidence measurement step, the probe movement Z-direction axis is inclined with respect to the normal direction of a plane parallel to the surface of the sample, and the XY-direction probe The probe is moved by the moving means in the predetermined XY direction from the predetermined initial position by the predetermined minute distance to stop, and at each position where the movement in the XY direction stops, the probe moves in the XY direction. An oblique incidence measurement step for measuring the surface shape of the sample by moving the probe closer to the surface of the sample while stopping the movement,
Surface shape data for obtaining the surface shape data of the sample from data obtained by combining the surface shape data of the sample measured in the normal incidence measurement step and the surface shape data of the sample measured in the inclined incidence measurement step A method for measuring a sample surface shape, comprising: performing a merging step. It is a measuring method of the sample surface shape according to claim 6,
After performing the oblique incidence measurement step,
The probe is returned to the initial position where the measurement was started in the normal direction measurement step, the direction of the cantilever and the probe movement Z direction axis are reversed by the cantilever reversing means, and the XY direction probe moving means is The probe is stopped by moving the probe in the predetermined XY direction by the predetermined minute distance from the predetermined initial position, and the movement in the XY direction is stopped at each position where the movement in the XY direction stops. While performing the reverse tilt incidence measurement step of measuring the surface shape of the sample by bringing the probe close to the surface of the sample,
In the surface shape data merging step, the reverse tilt incidence measurement is performed on the surface shape data of the sample measured in the normal incidence measurement step and the surface shape data of the sample measured in the tilt incident measurement step. A sample surface shape measurement method, wherein the surface shape data of the sample is obtained from data obtained by further adding and merging the surface shape data of the sample measured in the step.

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