JP2002014025A - Probe scanning control device, scanning probe microscope by the same, probe scanning control method, and measuring method by the scanning control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a probe scanning control device, scanning probe microscope by the same, probe scanning control method, and measuring method by the scanning control method, capable of detecting a solid-shaped sample where the angle of inclination changes, with fixed resolution in the direction of the shape of the sample. SOLUTION: Sampling is performed by controlling intervals in such a way that the follow distance of the probe in the direction of the shape of the sample may be constant between sampling points divided at regular intervals in the direction of the shape of the sample.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning control device for a probe, a scanning probe microscope using the scanning control device, a scanning control method for a probe, and a measuring method using the scanning control method. The present invention relates to the technical field of SPM (scanning probe microscope) for acquiring information on a measurement sample by scanning.

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (hereinafter abbreviated as STM) capable of directly observing the electronic structure of a conductor has been developed [G. Binning et al. Phys. Re
v. Lett, 49, 57 (1982)]
(Atomic force microscope), SCM (scanning capacity microscope), S
Microscope devices, such as NOM (near-field optical microscope), which obtain various information and its distribution by scanning a probe having a sharp tip, have been developed one after another. At present, these microscope groups are collectively referred to as scanning probe microscopes (SPM), and have been widely used as means for observing microstructures having resolution at the atomic and molecular levels.

Heretofore, these SPM devices have been used as surface observation devices for a cleaved surface of a crystal such as metal or mica graphite or a planar sample such as a silicon substrate.
However, at present, industrial application is expected as a means for observing a three-dimensional structure such as a wiring structure created by a semiconductor process and a microstructure created by a micromachine technology.

[0004] The operation of a general SPM device will be described below.
The operation of the AFM will be briefly described. In order to measure the surface shape of a flat sample, a sharp probe is supported by an elastic body called a cantilever, and the tip of the probe is pressed against the sample with a predetermined force. Since the cantilever acts as a leaf spring, the pressing force can be determined by detecting the amount of deflection of the cantilever. Using an xy stage operating in a plane parallel to the sample surface, the sample and the probe are relatively linearly scanned at a constant speed. During scanning, a z-stage that moves perpendicular to the sample surface is used, and the distance between the probe and the sample surface is controlled so that the pressing force is constant, that is, the deflection of the cantilever is constant. Follow. By sampling the control amount of the z stage at equal time intervals, a linear cross-sectional profile of the surface shape can be obtained. Furthermore, in a plane parallel to the sample surface,
By repeating the above operation in a so-called raster shape, a two-dimensional distribution of the sample shape is obtained.

[0005] During the measurement, for example, by applying a bias voltage to the sample using a conductive probe and measuring the current, the distribution of conductivity on the sample surface can be known. When light is incident on the sample surface from the probe in a state where the probe having the aperture is brought close to the near-field region and the scattered light is measured, SNOM results. In the STM, the same distance control is performed by making the tunnel current flowing between the probe and the sample constant, and the measurement is performed.

[0006]

Conventionally, in the case where the entire sample plane is inclined with respect to the scanning plane, the problem that the sampling interval in the sample plane changes due to local unevenness of the sample, for example, is described in, As disclosed in Japanese Unexamined Patent Publication No. Hei 6-147821, a method of sampling at equal intervals in the sample plane direction has been proposed. However, the three-dimensional structure as described above has a structure with a large spatial frequency compared to the distribution of the observation target on the sample surface, that is, a fine structure (surface structure) such as a surface shape on a large shape (sample shape). Therefore, when the SPM apparatus having such a general configuration is used as a surface observation unit, another problem occurs. This will be described below with reference to the drawings.

For the purpose of explanation, consider a case in which a sample 112 having a semicircular three-dimensional shape is divided into six parts as shown in FIG. 3, a measured amount is sampled at seven points, and surface measurement is performed by a conventional SPM apparatus. By performing interval control in the interval control direction 203 while scanning in the scanning direction 202,
Are sampled at equal intervals. The distance between the sampling points in the scanning direction is d _h, and hereinafter, the sampling distance 301 in the scanning direction.

In the figure, d _r1 to d _r3 are the distances that the probe actually follows along the shape of the sample 112 between the sampling points, and this is hereinafter referred to as a sample shape direction sampling distance 302. relationship from d _r1 d _r3 and d _h is a _{d r1> d r2> d r3} > d h, not at regular intervals in the even sample shape direction and sampled at regular intervals in the scanning direction, is larger inclination angle About
The sampling interval in the sample shape direction becomes large. This is not a major problem in measuring a sample that can be regarded as a plane as in the past, but when performing surface measurement on a three-dimensional shape as described above, the inclination angle of the observed three-dimensional surface with respect to the scanning direction is measured. The change causes a problem that the sampling rate in the sample shape direction changes, that is, the resolution of the surface measurement changes.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and provides a probe scanning control apparatus capable of detecting a three-dimensional sample whose inclination angle changes with respect to the scanning direction with a constant resolution in the sample shape direction. It is an object of the present invention to provide a scanning probe microscope using a control device, a method for controlling scanning of a probe, and a measuring method using the scanning control method.

[0010]

In order to achieve the above object, the present invention provides a probe scanning control device configured as described in the following (1) to (10), a scanning probe microscope using the scanning control device, And a scanning control method of the probe, and a measuring method by the scanning control method. (1) In a probe scanning control device for detecting information on a sample by scanning the probe relative to the sample, the follow-up distance of the probe in the sample shape direction is divided at equal intervals in the sample shape direction. A scanning control apparatus for a probe, comprising: an interval control unit that performs sampling so as to be constant between the respective sampling points. (2) The interval control means calculates a sampling rate so that the distance that the probe follows the sample shape direction between each sampling point is constant, and the calculation result of the sampling rate calculation means is (1) characterized by having at least sampling means for sampling measurement information based on
3. The scanning control device for a probe according to claim 1. (3) The sampling rate calculation means has a spatial frequency limiting means for limiting a spatial frequency of a shape on a sample regarded as the tracked distance.
3. The scanning control device for a probe according to claim 1. (4) In a scanning probe microscope having a probe for scanning a probe relative to a sample to detect information on the sample, the scanning of the probe may be performed according to any one of the above (1) to (3). A scanning probe microscope configured to be controlled by a scanning control device. (5) Sampling rate storage means for storing a sampling rate between each sampling point calculated by the sampling rate calculation circuit; The scanning probe microscope according to the above (4), further comprising information synthesizing means for synthesizing a dimensional distribution. (6) In the probe scanning control method for detecting information on the sample by scanning the probe relative to the sample, the follow-up distance of the probe in the sample shape direction is divided at equal intervals in the sample shape direction. A method of controlling the scanning of a probe, wherein the sampling is performed by controlling the interval so as to be constant between the respective sampling points. (7) The interval control is characterized in that a sampling rate is calculated so that a distance followed by a probe in a sample shape direction between each sampling point is constant, and measurement information is sampled based on the sampling rate. The scanning control method for a probe according to the above (6), wherein (8) The method of controlling scanning of a probe according to the above (7), wherein, when calculating the sampling rate, a spatial frequency of a shape on the measurement sample regarded as the tracked distance is limited. (9) In a measuring method for measuring a surface shape of a sample using a probe that scans relative to the sample, scanning of the probe is controlled by the scanning control method according to any one of the above (6) to (8). A method for measuring surface information of a sample, characterized by the following. (10) The sample according to (9), wherein a sampling rate between the sampling points is stored, and a two-dimensional distribution of the measurement information is synthesized using the stored sampling rate between the sampling points. A measurement method for measuring surface information of objects.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention,
In the scanning probe microscope which measures the sample surface by applying the above configuration and causing the probe to follow the sample surface, sampling is performed so that the follow distance in the sample shape direction of the probe between the sampling points is constant. By doing
For surface measurement of a sample with a three-dimensional shape in which the inclination angle between the scanning direction and the sample shape direction changes, the surface measurement can be performed with the same resolution as in the case of measuring a planar sample. be able to. In addition, by limiting the frequency of the signal for calculating the follow-up distance of the probe, it is possible to set the spatial frequency to be handled as the sample shape. Furthermore, two-dimensional synthesis of measurement information in the scanning plane can be performed with reference to the sampling time interval.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 is a schematic diagram for explaining the principle of the present invention. In FIG.
By performing the interval control in the interval control direction 203 while scanning in the direction 2, sampling is performed at equal intervals for the distance that the probe actually follows the sample 112, that is, the sample shape direction sampling distance 302.

Hereinafter, the apparatus of this embodiment and its operation will be described. As shown in FIG. 1, a probe 111 including an elastic body 109 and a probe 110 is arranged so as to face the surface of the sample 112. The probe 111 is fixed, and the sample 112 is attached to the xyz drive stage 108. The probe 111 is formed by a semiconductor process and has a configuration shown in FIG. In the probe 111, the probe 110 is supported by an elastic body 109 made of Si. On the surface of the elastic body 109,
By implanting As, a piezoresistive layer 501 is formed as shown in FIG. 5, and the resistance value changes according to the stress generated by the deformation of the elastic body.

The displacement detection circuit 102 applies a bias voltage to the elastic body 109 of the probe 111 as shown in FIG.
By detecting the value of the flowing current, the amount of deflection of the elastic body 109 is detected and sent to the position control amount calculation circuit 103. Elastic body 1
Since 09 functions as a leaf spring, its deflection amount is proportional to the probe pushing force when it is sufficiently small. The position control amount calculation circuit 103 calculates the distance control amount between the probe 110 and the sample 112 so that the probe pressing force is constant, that is, the deflection amount of the elastic body 109 is constant, and the position control circuit 106, The signal is sent to the sampling rate calculation circuit 104 and the sampling circuit 105. Further, the probe 110 and the sample 1
The relative scanning amount in the plane with the position 12 is sent to the position control circuit 106 and the sampling rate calculation circuit 104. The position control circuit 106 controls the xyz drive stage 108 according to the instructed control amount, and changes the relative position between the probe 110 and the sample 112.

Here, the sampling rate calculation circuit 10
4 will be described. The input interval control amount is
First, the light passes through a low-pass filter having a preset cutoff frequency. Then, this output signal and the scan signal by differentiating each interval control direction velocity V _h and obtains the scanning direction velocity V _v. Since the scanning direction and the interval control direction is orthogonal, the sample shape direction velocity V _s is Becomes

Next, this V _s is integrated. Assuming that a predetermined sampling distance in the sample shape direction is d _r and the immediately preceding sampling time is t _s−1 , At time t _s , a trigger signal is output to the sampling circuit 105 and the sampling rate storage circuit 106.

The sampling circuit 105 receives the trigger signal and acquires the position control amount at that time. The sampling rate storage circuit 106 stores sampling time intervals. The measurement operation is performed on the L × L square range using the apparatus having the above configuration. Scanning is performed linearly for the length L, and a line profile of the surface shape is obtained as shown in FIG. This line profile is a spatial frequency determined from the cutoff frequency of the low-pass filter and the scanning speed, The measurement is performed at the same resolution in the sample shape direction having the following spatial frequency.

Next, in a direction perpendicular to the probe 110 and the sample 112 and the scanning direction are relatively moved by d _r, performs the same measuring operation. This is repeated to scan the entire L × L measurement range. Further, the scanning direction is rotated by 90 degrees, and the same measurement operation is performed. With the above operation, a line profile group can be acquired in two orthogonal directions over the entire scanning range.

Next, the measurement results are synthesized two-dimensionally. First,
The synthesis is performed for the entire measurement range. The number of pixels of the two-dimensional data to be synthesized can be determined as appropriate. Use pixels. The sampling points in the two scanning directions obtained by the operations up to this point are not equally spaced in each scanning direction. Time interval and scanning speed V _{h of} each sampling point stored in the sampling rate storage circuit
Since the position of each sampling point is known from the distance d _r between each scan, the information of the sampling point closest to each pixel is used as the information of the pixel. The two-dimensional data obtained in this way has an error of a displacement between a sampling point and a pixel, but can be used as an overall image. Also, of course, another combining method such as a weighted averaging process according to the distance from each pixel may be used.

In this embodiment, the displacement of the probe 110 is detected by the piezoresistive layer 50 due to the deflection of the elastic body 109.
The resistance change of 1 was used.
Other displacement detecting means may be used. In the present embodiment, an example of an apparatus configuration as an atomic force microscope for measuring the surface shape of the sample 113 has been described. However, by simultaneously detecting different physical quantities during scanning, for example, a near-field optical microscope, a static The present invention is also applicable to other scanning probe microscope devices such as a capacitance microscope.

[0021]

As described above, according to the present invention, a probe scanning control device capable of detecting a three-dimensional sample whose inclination angle changes with a constant resolution in the sample shape direction, and the scanning control device Scanning probe microscope with device,
And a scanning control method of the probe and a measuring method by the scanning control method. Further, according to the present invention, by configuring so as to limit the frequency of the signal for calculating the following distance of the probe, it is possible to set the spatial frequency to be handled as the sample shape. Further, according to the present invention, two-dimensional synthesis of measurement information in a scanning plane can be enabled with reference to a sampling time interval.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a surface observation device according to an embodiment of the present invention.

FIG. 2 is a view for explaining a measurement operation in the embodiment of the present invention.

FIG. 3 is a diagram illustrating a problem to be solved in the present invention.

FIG. 4 illustrates the principle of the present invention.

FIG. 5 is a diagram illustrating a configuration of a probe according to an embodiment of the present invention.

[Explanation of symbols]

 101: housing 102: displacement detection circuit 103: position control amount calculation circuit 104: sampling rate calculation circuit 105: sampling circuit 106: position control circuit 107: information synthesis circuit 108: xyz drive stage 109: elastic body 110: probe 111: Probe 112: Sample 201: Sampling point 202: Scanning direction 203: Interval control direction 301: Sampling distance in scanning direction 302: Sampling distance in sample shape direction 501: Piezoresistive layer

Claims (10)

[Claims] 1. A scanning control apparatus for a probe for scanning a probe relative to a sample to detect information on the sample, wherein the follow-up distance of the probe in the sample shape direction is equal to the sample shape direction. A scanning control device for a probe, comprising interval control means for performing sampling so as to be constant between the respective sampling points divided by (1). 2. A sampling rate calculating means for calculating a sampling rate so that a distance followed by a probe in a sample shape direction between each sampling point is constant, and a calculation by said sampling rate calculating means. Based on the results,
The scanning control apparatus for a probe according to claim 1, further comprising: sampling means for sampling measurement information. 3. The probe scanning control apparatus according to claim 2, wherein said sampling rate calculating means includes a spatial frequency limiting means for limiting a spatial frequency of a shape on the sample regarded as the tracked distance. . 4. A scanning probe microscope having a probe for scanning a probe relative to a sample to detect information on the sample, wherein the scanning of the probe is performed according to any one of claims 1 to 3. A scanning probe microscope configured to be controlled by the scanning control device. 5. Sampling rate storage means for storing a sampling rate between each sampling point calculated by the sampling rate calculation circuit; and measurement information using the sampling rate between each sampling point stored in the sampling rate storage means. 2
5. The scanning probe microscope according to claim 4, further comprising information synthesizing means for synthesizing a dimensional distribution. 6. A scanning control method for a probe for scanning a probe relative to a sample to detect information on the sample, wherein a follow-up distance of the probe in the sample shape direction is equal to the sample shape direction. A scanning control method of a probe, characterized in that sampling is performed by controlling an interval so as to be constant between each sampling point divided by (1). 7. The interval control according to claim 1, wherein a sampling rate is calculated so that a distance that the probe follows the sample shape direction between each sampling point is constant, and the measurement information is sampled based on the sampling rate. 7. The scanning control method for a probe according to claim 6, wherein: 8. The probe scanning control method according to claim 7, wherein, when calculating the sampling rate, a spatial frequency of a shape on the measurement sample regarded as the tracked distance is limited. 9. A method for measuring the surface shape of a sample using a probe that scans relative to the sample, wherein the scanning of the probe is controlled by the scanning control method according to claim 6. A method for measuring surface information of a sample, characterized in that: 10. The method according to claim 9, wherein a sampling rate between the sampling points is stored, and a two-dimensional distribution of the measurement information is synthesized using the stored sampling rate between the sampling points. A measuring method for measuring surface information of a sample.