JP4011506B2 - Scanning probe microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a scanning probe microscope represented by a scanning atomic force microscope (AFM), and in particular, obtains an accurate scanning image or observation data by improving the positional accuracy of main scanning. The present invention relates to a scanning probe microscope.
[0002]
[Prior art]
In scanning probe microscopes such as AFM, a cantilever with a probe attached to the tip of a cantilever is used to detect the fine structure and structure of the sample surface using the interaction between the sample surface and the probe. Used as a probe. When such a cantilever is used, if the probe is scanned on the sample surface, an attractive force or a repulsive force based on an atomic force is generated between the sample surface and the probe. Therefore, this atomic force can be detected as the amount of strain of the cantilever, and the sample stage can be finely moved in the Z-axis direction so that the amount of strain is constant, that is, the gap between the sample surface and the probe is constant. For example, the fine movement signal at that time or the detected distortion amount itself represents the surface shape, material or other characteristics of the sample.
[0003]
FIG. 10 is a block diagram showing a configuration of a signal processing system of a conventional scanning probe microscope.
[0004]
A sample 52 to be observed is placed on the three-dimensional sample stage 55. Above the sample 52, a probe 54 attached to the free end of the cantilever 53 is disposed to face the sample 52. The amount of distortion of the cantilever 53 is detected by the detection unit 50, and is input to the non-inverting input terminal (+) of the comparator 75 as a distortion signal S1 representing the gap between the sample surface and the probe 54. A target value signal regarding the distortion amount of the cantilever 53 is input from the target value setting unit 79 to the inverting input terminal (−) of the comparator 75.
[0005]
The error signal S2 output from the comparator 75 is input to the proportional integration (PI) control unit 76, and a signal obtained by synthesizing the error signal S2 and its integrated value is used as an actuator drive signal S3 that also serves as a scanning image signal. 70 and filter 80. The scanning signal generator 78 supplies the actuator driving amplifier 70 with a main scanning signal Sx and a sub scanning signal Sy for causing the probe 54 to scan the sample 52 in the X and Y directions. The detection unit 50, the comparator 75, the PI control unit 76, and the actuator drive amplifier 70 constitute a feedback circuit.
[0006]
The output signal of the filter 80 is supplied as a scanning image signal to the A / D converter 82 via the amplifier 81, where it is converted into a digital signal (image data) and stored in the image memory 83. The image forming unit 65 outputs an address signal and a read signal to the image memory 83 in synchronization with the clock signal output from the synchronization signal generator 85. The image data output from the image memory 83 in response to the address signal and the read signal is converted into an analog signal in the image forming unit 65 in response to the horizontal and vertical synchronization signals supplied from the synchronization signal generator 85. And output to the color monitor 63.
[0007]
As for this type of AFM apparatus, pages 495-499 of the journal “Design Engineering” (Vol.37, No10: October 2002) published by the Japan Society for Design Engineering (Non-Patent Document 1) Is discussed under the title of "Current Status of AFM and AFM Equipment for Wide-Range Observation".
[0008]
[Non-Patent Document 1]
“Design Engineering” (Vol.37, No10: October 2002) pp. 495-499 [0009]
[Problems to be solved by the invention]
FIGS. 11 and 12 are diagrams schematically showing the scanning range and scanning locus of the probe 54. The probe 54 ideally moves within the rectangular scanning range in the Y direction as shown in FIG. Sub scanning is gradually performed in the X direction while repeating main scanning. However, in actuality, due to the influence of the driving accuracy and assembly accuracy of the sample stage 55, a slight deviation occurs in the start point and end point of the main scanning. As shown in FIG. 12, when the main scanning position (start point and end point) is displaced, the scanning range may be a substantially parallelogram.
[0010]
In the image processing system, the main and sub-scanning positions of the probe 54 correspond to the main and sub-scanning positions of the display unit 63. For this reason, when the scanning range is a parallelogram as described above, a rectangular observation object 10 as shown in FIG. 12 is displayed on the display unit 63 as a scanning image as shown in FIG. As described above, there is a technical problem that the image is deformed into a diamond shape and an accurate scanning image cannot be obtained.
[0011]
An object of the present invention is to provide a scanning probe microscope that solves the above-described problems of the prior art and improves the position accuracy of main scanning so as to obtain an accurate scanning image and observation data.
[0012]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention scans a probe surface close to or in contact with a sample surface, and in a scanning probe microscope that measures the surface shape or physical quantity of the sample, the main scanning signal and the sub-scanning signal are obtained. Scanning signal generating means for generating, means for generating a main scanning position correction signal for correcting the position of the main scanning in the main scanning direction, and correcting the main scanning signal by superimposing the main scanning position correction signal on the main scanning signal. Means for generating, and means for main-scanning and sub-scanning the probe on the sample surface in response to the corrected main scanning signal and sub-scanning signal.
[0013]
According to the above feature, the position of the main scanning in the main scanning direction can be corrected. Therefore, if the main scanning position correction signal is set so that the positional deviation in the main scanning direction of the main scanning is canceled, the main scanning of the main scanning is performed. The position with respect to the direction is always constant. As a result, it becomes possible to accurately scan within a predetermined scanning range of the sample surface, and an accurate scanning image or observation data can be obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a signal processing system of a first embodiment of a scanning probe microscope according to the present invention. The same reference numerals as those described above represent the same or equivalent parts.
[0015]
A sample 52 to be observed is placed on the three-dimensional sample stage 55. Above the sample 52, a probe 54 attached to the free end of the cantilever 53 is disposed to face the sample 52. The amount of strain of the cantilever 53 is detected by the detector 50 and is input to the non-inverting input terminal (+) of the comparator 75 as a strain signal S1 representative of the gap between the sample surface and the probe 54. A target value signal regarding the distortion amount of the cantilever 53 is input from the target value setting unit 79 to the inverting input terminal (−) of the comparator 75.
[0016]
The error signal S2 output from the comparator 75 is input to the proportional integration (PI) control unit 76, and the error signal S2 and a signal obtained by synthesizing the error signal S2 are combined into an actuator drive amplifier as an actuator drive signal S3 that also serves as a scanning image signal. 70 and filter 80.
[0017]
The D / A converter 77 converts the digital main scanning position correction signal S4 output from the main scanning position correction unit 61 of the main control unit 60 into an analog main scanning position correction signal Sc. The correction amount by the main scanning position correction unit 61 is manually input from the input operation unit 62 by the operator.
[0018]
The scanning signal generator 78 outputs a main scanning signal Sx for causing the probe 54 to perform main scanning in the X direction on the sample surface and a sub scanning signal Sy for performing sub scanning in the Y direction. 2 and 3 are waveform diagrams of the main scanning signal Sx and the sub-scanning signal Sy, respectively. The main scanning signal Sx is superimposed on the main scanning position correction signal Sc in the adding circuit 74 and supplied to the actuator drive amplifier 70 as a corrected main scanning signal Sxc. The sub-scanning signal Sy is supplied to the actuator drive amplifier 70 as it is.
[0019]
The actuator drive amplifier 70 drives the three-dimensional sample stage 55 so that the probe 54 is main-scanned and sub-scanned on the sample surface in response to the corrected main scanning signal Sxc and sub-scanning signal Sy. The detection unit 50, the comparator 75, the PI control unit 76, and the actuator drive amplifier 70 constitute a feedback circuit.
[0020]
In such a configuration, the main scanning position correction signal Sc (S4) output from the main scanning position correction unit 61 of the main control unit 60 is an offset for correcting a shift of the main scanning position in the main scanning direction. As shown in FIG. 4, the signal gradually increases (or gradually decreases) as the sub-scanning position advances. Therefore, as shown in FIG. 5, the corrected main scanning signal Sxc output from the adder circuit 74 has the start point and end point positions in the main scanning direction (X direction) as the main scanning position advances in the sub scanning direction. Shifted to. For this reason, if the correction amount (shift amount) is adjusted in accordance with the shift amount of the main scanning signal, the main scanning position can be returned to the normal position.
[0021]
As described above, according to the present embodiment, the position of the main scanning in the main scanning direction can be corrected. Therefore, by setting the correction signal so that the positional deviation in the main scanning direction of the main scanning is canceled, The position in the main scanning direction is always constant. As a result, it becomes possible to accurately scan within a predetermined scanning range of the sample surface, and an accurate scanning image or observation data can be obtained.
[0022]
FIG. 6 is a block diagram showing the configuration of the signal processing system of the second embodiment of the scanning probe microscope according to the present invention, and the same reference numerals as those described above represent the same or equivalent parts.
[0023]
In the present embodiment, instead of the D / A converter 77, the sub-scan signal Sy is attenuated to generate the main scan position correction signal Sc, and this is added to the main scan signal Sx by the adder circuit 74. The main scanning position correction unit 61 outputs an attenuation rate instruction signal S5 in response to an operation signal input from the input operation 62 instead of the main scanning position correction signal S4. There is a feature in the point.
[0024]
That is, in the first embodiment described above, the main scanning position in the main scanning direction is obtained by adding the main scanning position correction signal Sc (S4) output from the main scanning position correction unit 61 of the main control unit 60 to the main scanning signal Sx. The main scanning position correction signal Sc is a signal that gradually increases (or gradually decreases) as the main scanning position advances in the sub-scanning direction (Y direction), as shown in FIG. 3 is substantially equal to a waveform obtained by scaling the sub-scan signal Sy in FIG. Therefore, in this embodiment, instead of independently generating the main scanning position correction signal Sc, the main scanning position correction signal Sc is generated by attenuating the sub scanning signal Sy by the attenuator 72.
[0025]
According to the present embodiment, since the main scanning position correction signal Sc can be generated simply by attenuating the sub-scanning signal Sy, the configuration is simplified compared to the first embodiment.
[0026]
FIG. 7 is a block diagram showing the configuration of the signal processing system of the third embodiment of the scanning probe microscope according to the present invention, and the same reference numerals as those described above represent the same or equivalent parts.
[0027]
In the first embodiment described above, the operator inputs the correction amount of the main scanning position from the input operation unit 62. Also in the second embodiment, the operator inputs the attenuation rate for the sub-scanning signal Sy from the input operation unit 62. explained. However, in the third embodiment described below, the main scanning position is automatically corrected by first performing a pre-scan to detect the amount of deviation of the main scanning position and automatically obtaining the correction amount. I am doing so.
[0028]
FIG. 8 is a diagram schematically showing the automatic correction method according to the present embodiment. First, a sample having a reference line Lref perpendicular to the main scanning direction is placed on the specimen stage 52 as a reference sample. Next, the main scan (Lx1, Lx2) is performed by the pre-scan unit 63 of the main control unit 60 in at least two places having different sub-scanning positions.
[0029]
At this time, line profiles Sref1 and Sref2 are obtained from the A / D converter 82 for each scanning position, as shown in FIG. The correction amount detection unit 62 of the main control unit 60 shifts the main scanning position based on the difference ΔX between the detection positions of the reference line Lref in the line profiles Sref1 and Sref2 and the difference ΔY between the main scanning positions Lx1 and Lx2. And a correction amount thereof is obtained and registered in the main scanning position correction unit 61. Thereafter, the main scanning position is corrected in the same procedure as in the first embodiment.
[0030]
In the above description, the application example to the first embodiment has been described. However, if the attenuation rate is controlled by the detected correction amount, the present invention can be similarly applied to the second embodiment.
[0031]
According to the present embodiment, the shift of the main scanning position in the main scanning direction can be automatically corrected without bothering the operator.
[0032]
【The invention's effect】
According to the present invention, the following effects are achieved.
(1) According to the present invention, since the position of the main scanning in the main scanning direction can be corrected, the main scanning position correction signal is set so that the positional deviation in the main scanning direction of the main scanning is canceled, thereby the main scanning. The position in the main scanning direction is always constant. As a result, it becomes possible to accurately scan within a predetermined scanning range of the sample surface, and an accurate scanning image or observation data can be obtained.
(2) If the main scanning position correction signal is generated by attenuating the sub-scanning signal, the main scanning position shift can be corrected with a simple configuration.
(3) If the amount of deviation of the main scanning position is first obtained by performing pre-scanning, and the amount of correction is obtained based on this amount of deviation, the deviation of the main scanning position can be automatically corrected.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a signal processing system of a first embodiment of a scanning probe microscope according to the present invention.
FIG. 2 is a diagram illustrating an example of a waveform diagram of a main scanning signal Sx.
FIG. 3 is a diagram illustrating an example of a waveform diagram of a sub-scanning signal Sy.
FIG. 4 is a diagram illustrating an example of a waveform diagram of a main scanning position correction signal Sc.
FIG. 5 is a diagram illustrating an example of a waveform diagram of a corrected main scanning signal Sxc.
FIG. 6 is a block diagram showing the configuration of a signal processing system of a second embodiment of the scanning probe microscope according to the present invention.
FIG. 7 is a block diagram showing a configuration of a signal processing system of a third embodiment of the scanning probe microscope according to the present invention.
FIG. 8 is a diagram (part 1) schematically illustrating a correction amount detection method according to a third embodiment.
FIG. 9 is a diagram (part 2) schematically representing a correction amount detection method according to a third embodiment.
FIG. 10 is a block diagram showing a configuration of a signal processing system of a conventional scanning probe microscope.
FIG. 11 is a diagram (No. 1) for describing problems of the conventional technology.
FIG. 12 is a diagram (No. 2) for describing problems in the prior art.
FIG. 13 is a diagram (No. 3) for describing a problem of the conventional technique.
FIG. 14 is a diagram (No. 4) for describing a problem of the conventional technique.
[Explanation of symbols]
52 ... Sample 53 ... Cantilever 54 ... Probe 55 ... Three-dimensional sample stage 70 ... Actuator drive amplifier 74 ... Differential amplifier 76 ... Proportional integral (PI) controller

Claims (4)

In a scanning probe microscope that measures the surface shape or physical quantity of a sample by scanning the probe surface close to or in contact with the sample surface,
Scanning signal generating means for generating a main scanning signal and a sub-scanning signal;
Means for generating a main scanning position correction signal for correcting the position of the main scanning in the main scanning direction as a function of the sub-scanning position ;
Means for generating a corrected main scanning signal by superimposing a main scanning position correction signal on the main scanning signal;
Means for main-scanning and sub-scanning the probe on the sample surface in response to the corrected main scanning signal and sub-scanning signal;
Scanning probe microscope comprising: a. The main scanning position level of the correction signal, scanning probe microscope according to claim 1, characterized in that increasing or decreasing in accordance with the progress of the sub-scanning position. Means, scanning probe microscope according to claim 1, characterized in that the sub-scanning signal is attenuated at a predetermined attenuation factor to generate the main scanning position correction signal for generating the main scanning position correction signal. In a scanning probe microscope that measures the surface shape or physical quantity of a sample by scanning the probe surface close to or in contact with the sample surface,
Scanning signal generating means for generating a main scanning signal and a sub-scanning signal;
Means for generating a main scanning position correction signal for correcting the position of the main scanning in the main scanning direction;
Means for generating a corrected main scanning signal by superimposing a main scanning position correction signal on the main scanning signal;
Means for main-scanning and sub-scanning the probe on the sample surface in response to the corrected main scanning signal and sub-scanning signal;
Pre-scanning means for performing main scanning in at least two different places with respect to the sub-scanning direction;
Means for detecting a correction amount of a main scanning position based on a plurality of line profiles obtained by the pre-scan;
Equipped with a,
The scanning probe microscope according to claim 1, wherein the means for generating the main scanning position correction signal generates a main scanning position correction signal corresponding to the correction amount.

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