JP2936489B2 - Tilt correction method and fine shape measurement method using the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a tilt of a sample surface in a measuring device that scans a probe on the sample surface and measures the shape of the sample surface.

[Summary of the Invention]

By rotating the probe in the scanning direction or the mounting direction of the sample, the scanning direction of the probe and the direction that does not always exist on the sample surface coincide with each other, thereby correcting the inclination of the sample surface and moving the probe to the sample surface. It is intended to improve the accuracy and efficiency of shape measurement in a measuring device that scans the above and measures the shape of the sample surface.

[Conventional technology]

For example, while keeping the distance between the sample surface and the probe constant using the tunnel effect, the probe is scanned in the in-plane direction along the sample surface, and the sample surface information is obtained from the height information of the probe at this time. (Scanning Tunneling Microscope) to Obtain Three-Dimensional Fine Shapes
In order to correct the tilt of the measurement image due to the tilt of the sample surface, a high-pass filter is incorporated in the portion that captures the height information of the probe, while eliminating the gradual increase and decrease of the capture information due to the tilt of the sample, Attempts have been made to adopt a method of taking in only information due to irregularities in the fine shape of the sample surface, a method of correcting the tilt by performing data processing of the taken-in information later.

[Problems to be solved by the invention]

However, in the method using a high-pass filter, there is a possibility that information of a gently fine shape on the sample surface may be lost.In addition, at the starting point of each scanning line, which is a turning point of the scanning of the probe, the inclination of the sample surface may be reduced. The gradual increase / decrease of the captured information changes rapidly in the opposite direction, and this effect cannot be eliminated by the high-pass filter, but rather disturbs the measurement image, and thus obtains a precise fine shape of the sample surface. It becomes difficult.

Further, in the method of performing data processing later, a large amount of time is spent for the processing, so that not only efficiency is extremely deteriorated, but also simultaneous observation of obtaining an observation image simultaneously with measurement becomes impossible.

[Means for solving the problem]

The above problem naturally occurs because the sample surface is inclined with respect to the scanning direction of the probe. Therefore, if the inclination of the sample surface with respect to the scanning direction of the probe is eliminated by some means, the above problem can be solved. However, providing a sample tilt correction table or the like for correcting the tilt of the sample surface not only complicates the function of the measuring device, but also requires a great deal of labor and time to correct the tilt accurately. And is very difficult in practice.

Therefore, even if a certain plane is inclined with respect to the horizontal plane, there is always a straight line parallel to the horizontal plane on that plane, and when scanning in the XY plane with STM etc., one screen When performing minute scanning, pay attention to the fact that scanning is repeated many times in the X-axis direction, but only one scanning is performed in the Y-axis direction. By rotating the direction, the X-axis scanning direction of the probe is made coincident with the direction without inclination always present on the sample surface, and furthermore, during one scanning time in the Y-axis direction, that is, during one screen scanning time, It is a method of measuring the fine shape of the sample surface by incorporating an extremely weak high-pass filter that can eliminate the increase and decrease of the height information of the probe caused by the inclination of the sample surface in the Y-axis scanning direction that occurs only once. .

[Action]

According to the above method, the means for rotating the scanning direction of the probe or the mounting direction of the sample and having almost no influence on the height information of the probe to be taken in are provided without providing a complicated mechanism and performing a large amount of correction work. By using a simple means of incorporating a high-pass filter having no sample, the inclination of the sample surface can be extremely easily corrected, and accurate measurement and simultaneous observation of the fine shape of the sample surface become possible.

〔Example〕

In the present embodiment, in particular, a method of correcting the inclination of the sample surface in an STM apparatus in which the probe is scanned in the in-plane direction using a piezoelectric element and a three-dimensional fine shape of the sample surface is obtained from height information of the probe at this time. This will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows an apparatus configuration applied to a first embodiment of the present invention.

The X-axis direction scanning signal X generated from the X-axis scanning signal generator 1 is divided into two systems, one of which is input to a COS signal modulator 5, and the other of which is obtained by inverting a signal with an inverting amplifier 3 and
Input to N signal modulator 6. The Y-axis direction scanning signal Y generated from the Y-axis scanning signal generator 2 is divided into two systems and input to the COS signal modulator 7 and the SIN signal modulator 8 as they are. The reference voltage generator 4 generates a reference voltage θ corresponding to an angle at which the in-plane scanning direction of the probe 16 is to be rotated,
Reference voltage θ according to the angle generated from reference voltage generator 4
Are divided into four systems and input as reference voltages for the COS signal modulators 5 and 7 and the SIN signal modulators 6 and 8, respectively. The COS signal modulators 5 and 7 modulate the input signals X and Y with the COS function of the reference voltage θ, and output signals XCOS θ and YCOS θ, respectively. The SIN signal modulators 6 and 8 modulate the input signals -X and Y with the SIN function of the reference voltage θ, and output signals -XSINθ and YSINθ, respectively.

The signal XCOSθ output from the COS signal modulator 5 is the signal YSINθ output from the SIN signal modulator 8 is input to the adder 9, and the addition signal YSINθ + XCOS output from the adder 9
θ is amplified at a desired amplification factor by the high-voltage amplifier 11, applied to the X-axis electrode 14 of the cylindrical piezoelectric element 13 which is an example of an in-plane scanning mechanism, and attached to the tip of the cylindrical piezoelectric element 13. The probe 16 is scanned in the X direction along the surface of the sample 17 arranged so as to face the probe 16.

The signal −XSINθ output from the SIN signal modulator 6 and COS
The signal YCOSθ output from the signal modulator 7 is input to the adder 10 and the added signal YCOSθ−XS output from the adder 10 is output.
IN θ is amplified at a desired amplification factor by a high-voltage amplifier 12, applied to the Y-axis electrode 15 of the cylindrical piezoelectric element 13, and the probe 16 attached to the tip of the cylindrical piezoelectric element 13 is connected to the probe 16. Scanning is performed in the Y direction along the surface of the sample 17 arranged so as to be opposed.

With the above-described configuration, the X-axis direction scanning signal X and the Y-axis direction scanning signal Y are converted into signals θ corresponding to angles at which the in-plane scanning direction of the probe 16 is rotated, respectively. YSINθ + XCOSθ and YCOSθ−XSINθ can be converted, and the probe 16 is scanned according to the signal YSINθ + XCOSθ in the X-axis direction and YCOSθ−XSINθ in the Y-axis direction. The in-plane scanning direction of the needle 16 is rotated to the right around the point where the X and Y signals are zero, so that the in-plane scanning direction of the probe 16 can be rotated to an arbitrary angle. Further, as a part of the configuration of the STM device, the distance between the sample 17 and the probe 16 is controlled to be constant at a portion not shown, and the height information of the probe 16 is It is taken in as shape information and is imaged.

In addition, a very weak high-pass filter, that is, a filter that cuts only signals at extremely low frequencies, is incorporated in the height information capturing section of the probe 16, so that all signals other than extremely long-period tilt signals pass through. It is designed to be imaged.

Here, in the STM apparatus, generally, the X-axis scanning signal generator 1 and the Y-axis scanning signal generator 2 show the scanning trajectory in FIG. 3 showing an in-plane scanning trajectory and a rotation example thereof. The reference voltage generator 4 generates an angle signal θ so that the probe scan trajectory 21 before rotation is changed to the probe scan trajectory after rotation. It will change like 22.

Now, in such an apparatus configuration, when the X-axis scanning signal generator 1 and the Y-axis scanning signal generator 2 generate scanning signals X and Y, respectively, the probe 16 moves the surface of the sample 17 in accordance with the scanning signals. Are scanned in-plane along the line. At this time, if the surface of the sample 17 is inclined compared to a plane orthogonal to the probe 16, the height of the probe 16 changes according to the surface shape of the sample 17 and its inclination. In this state, the sample 17 of the probe 16 is actually
The reference voltage generator 4 performs in-plane scanning along the surface of
While changing the direction of in-plane scanning along the surface of the sample 17 of the probe 16 by sequentially changing the angle signal θ generated from the Is observed, the range of change in the direction of in-plane scanning along the surface of the sample 17 of the probe 16 due to the angle signal θ generated from the reference voltage generator 4 is 180 ° C.
Within the range, there is always a point where the inclination of the observation image in the horizontal direction, that is, the X-axis direction disappears. At this time, the scanning direction of the probe 16 with the scanning signal X from the X-axis scanning signal generator 1 is
This means that there is no direction that is always present on the surface of 17. Thereafter, it is only necessary to continue the measurement with the angle signal θ from the reference voltage generator 4 fixed.

As described above, no special technique is required, and the tilt of the sample 17 is adjusted by an extremely easy method of rotating the in-plane scanning direction of the probe 16 so as to eliminate the horizontal tilt while observing the observation image at the start of measurement. Correction will be performed.

(Second Embodiment) FIG. 2 shows an apparatus configuration applied to the second embodiment of the present invention. However, since the inclination correction method is almost the same as that of the first embodiment, only different parts will be described. .

In the first embodiment, by changing the direction of in-plane scanning along the surface of the sample 17 of the probe 16 by rotationally converting the scanning signal, scanning by the scanning signal X from the X-axis scanning signal generator 1 is performed. And the direction without inclination that is always present on the surface of the sample 17 is matched. In the second embodiment, the sample on which the sample 17 is mounted is determined by the angle signal θ from the reference voltage generator 4. By rotating the rotary stage 18, the direction of scanning by the scanning signal X from the X-axis scanning signal generation 1 is made to coincide with the direction without inclination that always exists on the surface of the sample 17, and all others are the same. .

〔The invention's effect〕

As described above, by using the method of the present invention, it is possible to perform the inclination correction of the sample very easily, and thereby it is possible to accurately measure the fine shape of the sample surface in real time, High precision and high speed measurement are realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an apparatus applied to the first embodiment of the present invention, and FIG. 2 is an explanatory view of an apparatus applied to the second embodiment of the present invention. FIG. 3 is a diagram showing an in-plane scanning locus and an example of its rotation. 1 X-axis scanning signal generator 2 Y-axis scanning signal generator 3 Inverting amplifier 4 Reference voltage (angle signal) generator 5, 4 COS signal modulator 6, 8 SIN signal Modulator 9,10 Adder 11,12 High voltage amplifier 13 Cylindrical piezoelectric element 14 X-axis electrode 15 Y-axis electrode 16 Tip 17 Sample 18 Sample rotation stage 19: In-plane scanning area before rotation 20: In-plane scanning area after rotation 21: Probe scanning locus before rotation 22: Probe scanning locus after rotation

Claims (2)

(57) [Claims] When scanning one screen in the XY plane, the scanning direction of the probe or the mounting direction of the sample is rotated,
The X-axis scanning direction of the probe is made to coincide with the direction in which the sample surface is not tilted, and Y is generated once in one scanning time in the Y-axis direction.
A tilt correction method comprising correcting a tilt of a sample surface by incorporating a high-pass filter capable of eliminating an increase or a decrease in height information of a probe caused by a tilt of the sample surface in an axial scanning direction. 2. A fine shape measuring method for scanning a probe in an in-plane direction and obtaining a fine shape of a sample surface from height information of the probe at this time, in which one screen is scanned in an XY plane. Rotating the scanning direction of the probe or the mounting direction of the sample,
The X-axis scanning direction of the probe is made to coincide with the direction in which the sample surface is not tilted, and Y is generated once in one scanning time in the Y-axis direction.
A fine shape measurement method for correcting the tilt of the sample surface by incorporating a high-pass filter capable of eliminating an increase or decrease in height information of the probe caused by the tilt of the sample surface in the axial scanning direction.