JP2003247929A - Scanning probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for finding a minute sample scattered widely on a substrate in a short time and provide a method for securely moving the sample to an arbitrary position on the substrate by a probe of a scanning probe microscope with reduced damages of the probe and the sample. <P>SOLUTION: A mechanism for finding the sample is formed by performing raster scanning by predetermined high magnification ratio image frame when reaching a predetermined position and condition while performing raster scanning at low magnification ratio. Moreover, a signal (Z signal) indicating a height just below the probe during moving, a signal (error signal) proportional to a deviation amount from an initially set value of force in Z direction which acts on the probe and the substrate just below the probe or the sample, and a signal (friction signal) in the horizontal direction which acts between the sample and the substrate just below the probe or the sample are detected to form a mechanism which displays a time series signal and an instantaneous value signal of these signals and converts the error signal into reaction force in Z direction and the friction signal into reaction force in XY directions through an operation lever to inform a worker of them. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention finds a fine sample on a measurement screen of a scanning probe microscope, and based on the screen, a scanning type with a sample moving mechanism for moving the sample to a predetermined position. The present invention relates to a scanning probe microscope that processes a sample surface using a probe microscope and a probe.

[0002]

2. Description of the Related Art A conventional scanning probe microscope has a main purpose of observing an image of a sample, and there is a disadvantage in moving or arranging a plurality of observed samples to arbitrary places. For example, carbon nanotube, DN on the substrate
When A, fine particles, etc. were dispersed, it took a lot of time to quickly find these particles and move them to a predetermined position or arrange them. Further, it is difficult to align (contact) with a fine sample due to non-linearity of the piezo element used in the scanner, hysteresis and thermal drift of the sample position. In order to improve the nonlinearity and hysteresis of these piezo elements, S.Desogus, S.Lany,
R. Nerino, GB Picotto, etc. adopted a method in which a linear element such as a capacitance sensor was installed in the piezo scanner and the voltage applied to the piezo scanner was closed-loop controlled to match the reading amount of the element. (J.Vac.Sc
i.Technol. B12 (3), 1665-1668, 1994
However, this method complicates the device, and since the 3-axis sensor is attached to the piezo scanner, the self-weight of the sensor increases and the responsiveness of the piezo scanner deteriorates.
In addition, since a fine sample cannot be observed during movement, some alternative means is necessary.

M. Finch, V. Chi, of the University of North Carolina
RMFalvo, M. Washburn, R. Superfine et al.
CM SIGGRAPH, New York, 1995. pp. 13-18.) Describes a nanomanipulator controlling an atomic force microscope (AFM). In addition, 3rdTecn of the United States is AF
The image measured by M is taken in, the image is reproduced by computer graphics, a virtual probe is displayed on the image, and when this probe comes into contact with the sample of the computer graphic image, the lever operated by the operator is simulated. We have developed a device that generates a reaction force signal and informs the operator (registered trademark
NanoManipulatorDP-100). However, these methods did not reflect the interaction in which the AFM probe was actually in contact with a fine sample, and the reliability of sample movement did not increase, and the operability was improved.

[0004]

When a fine sample is moved to a predetermined position using a scanning probe microscope, first, the moving sample is found, the position of the moving destination is confirmed, the sample is touched,
It is necessary to move the sample. The first problem in this series of operations is that the moving sample is widely dispersed on the substrate and it takes time to find it. For example, dispersed on the substrate, diameter 0.0
When searching for fine particles of about 5 μm from the 100 μm section,
For XY, 5000 or more scanning lines are required. In this case, if the measurement area is set to 10 μm, 100 images need to be measured, and a great amount of time is required for the measurement for discovering the sample. The second problem is that the piezo scanner currently used in the scanning probe microscope is a non-linear element, and the position changes temporally due to hysteresis and creep, or the sample position changes due to thermal effects. In addition, it is difficult to contact a fine sample at one time. The third problem is that it is not possible to observe the moving sample, so when the moving sample comes off or encounters an obstacle, how to detach it or avoid the obstacle is asked to the operator. Multiple sources of signaling are required.

The present invention provides a means for discovering a fine sample widely dispersed on a substrate in a short time, and a scanning probe microscope for surely moving the fine sample or processing the sample surface at an accurate position. It is provided.

[0006]

In order to solve the first problem and the problem of the second problem, the present invention performs a predetermined high magnification at a predetermined position or under a predetermined condition while performing raster scanning at a low magnification. A mechanism (raster scanning / sample finding / probe stop mechanism) that stops the probe when a target sample is discovered or comes into contact with the sample by performing raster scanning in the image frame was created. In order to solve the third problem, a signal (Z signal) indicating the height immediately below the probe during movement and deviation of the force in the Z direction acting on the probe and the substrate or sample immediately below the probe from the initial setting position A signal proportional to the amount (error signal) and a horizontal force signal (friction signal) acting between the sample and the substrate directly under the probe or the sample are detected, and these signals are time-series signals and instantaneous position signals. Or a mechanism for notifying the operator of an error signal as a Z-direction reaction force and a friction signal as an XY-direction reaction force via an operation lever.

[0007]

When a sample is moved to a predetermined position by using a scanning probe microscope, a series of operations such as finding the sample, confirming the position to move to, contacting the sample and moving the sample are required. In order to find a moving sample, scanning is conventionally performed in a wide area (usually several μm square to 100 μm square) (screen 1). From this image, the approximate position of the sample to be moved is visually confirmed, the probe is moved to that position, and measurement is performed at high magnification (screen 2).

It is often the case that the shape of the sample cannot be confirmed visually or that the resolution is insufficient. In this case, a raster scanning / sample finding / probe stop mechanism, which will be described in detail in the following embodiments, is used.

Next, the outline of the destination position is determined on the screen 1, the probe is moved to that position, and measurement is performed at high magnification (screen 3). Next, the route for moving the sample is entered on the screen 1. Then, the unevenness information such as the maximum height from the sample surface is displayed along the moving route.

Next, the probe to be moved is brought into contact with the sample based on the position information on the screen 1. At this time, the probe may directly move in the air to the sample position, or may trace a sample surface and move straight. However, it is difficult to contact the target sample at one time because of the hysteresis and thermal drift of the piezo scanner. In this case, it is possible to easily contact the fine sample by using the raster scanning / sample finding / probe stop mechanism described in detail in the following embodiments. Measurement is performed at a high magnification (usually 0.1 μm or less) around the contact point to obtain a detailed image (screen 4) of the moving sample.

The position where the sample is pushed is determined on the screen 4, and the movement of the sample is started along the path. At the time of this movement, a height signal, an error signal, or a friction signal is displayed, and the moving speed is adjusted so that these are below the set values. After the sample arrives at the destination, high-magnification measurement of the screen after the movement is performed again to confirm the form after the movement (screen 5).

The above is the outline of the operation of moving the sample. In the embodiment of the invention, the raster scanning / sample finding / probe stop mechanism and each height signal, error signal or friction signal during sample movement are used. This will be described in more detail.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION <Device Configuration> An embodiment of the present invention will be described below with reference to a schematic diagram (FIG. 1) of a sample moving / processing scanning probe microscope of the present invention.

From FIG. 1, it can be seen that the Z coarse movement mechanism [1] has X.
The YZ scanner [2] is fixed, and the cantilever part [4] is attached via the piezoelectric diaphragm [3]. The cantilever part is the sample [5] fixed to the sample table [6].
Is facing. The back surface of the cantilever [4] is irradiated with the laser beam [7], and the reflected light is incident on the 4-division position detector [8]. The signals from the upper and lower sensors of the 4-division position detector are preamplifiers [1
0] and set the force in the Z direction (△ 1 force Se
The difference signal (error signal) from t) is Z servo system [12]
Entered in. The output signal (Z direction height signal) is amplified by the high voltage amplifier [13], the Z axis of the XYZ scanner [2] expands and contracts, and the distance between the probe and sample is controlled so that the amount of deflection of the cantilever becomes constant. Has been done. On the other hand, the signals from the left and right sensors of the four-division position detector are amplified by the preamplifier [9] to become friction signals.

These Z height signal (), error signal (), and friction signal () are converted into digital signals by analog / digital converters (A / D converters) [20, 21, 22], respectively. Instantaneous value (Fig. 2A)
This value is displayed on the display [42] as time series data (FIG. 2B) displayed in time series from the start of sample movement. Alternatively, a mechanism has been created in which an error signal is converted into a reaction force in the Z direction and a friction signal is converted into a reaction force in the XY direction-after digital-analog conversion [43], the worker operating the operation lever [44] is notified by the reaction force. Further, when the sample is moved using the operation lever [44], the values of the Z height signal, the error signal, and the friction signal are the set values (Δ1 ′ height Set, If it exceeds Δ2 error Set and Δ3 friction Set), XY scan controller [1
4], the increase of the triangular wave for XY scanning is stopped, and the movement of the probe is stopped until the Z height signal, the error signal, and the friction signal are below the set values.

In XY scanning, a triangular wave for raster scanning is input to a digital / analog converter in an XY controller, and its output is applied to a high voltage amplifier [15] to drive an XY piezo scanner. A shape image is displayed by the Z height signal and the XY raster signal, an error signal image is displayed by the error signal and the XY raster signal, and a friction image is displayed by the friction signal and the XY raster signal on the display [42]. Further, the scanning stop signal () holds the XY voltage values at an arbitrary position of the triangular wave, and fixes the probe at a predetermined position. The scanning stop signal automatically stops the XY scanning when the Z height signal, the error signal, and the friction signal exceed the set values.

<Raster scanning / sample finding / probe stop> FIG. 3A is a screen capture diagram of the raster scanning / sample finding / probe stop operation, and FIG. 3B is a time series of the output voltage of the XY scan controller [14]. It is a display example. The raster scanning / sample finding / probe stop operation will be described below. In order to find fine samples widely dispersed on the substrate, FIG.
This is an operation for scanning a low magnification (wide area) shown in A, and when the needle tip detects an object supposed to be a sample, scans the periphery thereof at a high magnification (narrow area) to facilitate the discovery of a fine sample. As shown in FIG. 3A, it is assumed that the image frame of a wide area is L and the number of scanning lines is N. Also, the narrow area for high-magnification measurement is 1, and the number of scans is n. Further, the offset amount of the scanning start point from the initial scanning line position is O = pnxL / N. First, scan a low magnification (wide area) with an offset amount of zero, and the instantaneous value of the Z height directly below the probe becomes higher than the set value, or the instantaneous value of the error signal immediately below the probe becomes larger than the set value. Alternatively, if the instantaneous value of the friction signal directly below the probe becomes larger than the set value, the trigger signal ()
The trigger generation position is set to the center of the screen, and a high-magnification image with the number of scanning lines n is measured in a narrow area l. After that, the operation returns to the trigger generation point and the interrupted low magnification scanning is continued. If the sample is not found even after scanning N lines, the offset amount is O = (1/2) (L /
N), and N low-magnification scans are performed again. If still not found, the offset amount is sequentially O = (1/4) (L /
N), O = (3/4) (L / N) ... And low-magnification scanning is performed again N times to search for a fine sample. FIG. 3B shows a triangular wave waveform for low-magnification / high-magnification XY scanning. By using this method, fine samples widely dispersed on the substrate can be automatically found at high magnification in a short time.

Next, a method of contacting the sample and stopping the probe at that position when the target sample is found from the image measured at high magnification by the above method will be described. 2-3 raster scanning is performed in the low-magnification image area L to reach the trigger generation point, and high-magnification scanning is started. Here, the raster scanning is stopped by setting a point where the Z height signal, the error signal, or the friction signal exceeds the set value as a new sample contact position. In this moving method, rasterization is performed to approach the sample, so that linearity correction can be performed, and since high-magnification measurement is performed again, the probe can be accurately brought into contact with the sample.

<Application of Raster Scanning to Processing> This raster scanning method can also be applied to processing of a sample surface. A method of performing mechanical processing or electrical processing on a substrate using an AFM probe is proposed in, for example, Japanese Patent Application No. 5-49713. However, until now, when processing the character “A” as shown in FIG. 4A, the character A was directly created with a single stroke. If this method is used, the characters will be distorted due to the influence of the nonlinearity and hysteresis of the piezo scanner. Therefore, as shown in FIG. 4B, a method of processing the sample surface when reaching a predetermined position while performing raster scanning was applied. Explaining the electric processing as an example, first, the image contour L1 to be processed and the number N1 of raster lines are determined. Next, during a certain period during which the probe is moving on the scanning line (FIG. 4B: t
In 1), a voltage is applied between the probe and the sample to process the sample surface. In the method of processing while performing raster scanning, since the probe repeats constant scanning, linearity correction can be performed for each scanning line, and processing at an accurate position is possible. ) <Each signal monitor during sample movement> Next, a description will be given when the sample is moved. The movement of the sample is usually controlled so that the force between the probe and the sample is constant (contact mode), and the sample is moved to a predetermined location. From the screen 1 and the screen 5 described in the section of action, the moving destination place and the moving direction of the sample are determined, and the moving route is determined and displayed on the screen 1. After the probe comes into contact with the sample, the center of gravity of the sample is calculated from the shape of the high-magnification screen, and the position to press the sample (Fig. 5A) based on the moving direction of the sample and the center of gravity is shown on the image display. After moving the probe to that position, the sample is pressed to start moving. The current position of the probe is calculated from the voltage applied to the XY piezo scanner when the screen 1 is measured and displayed on the screen 1. When the moving speed of the probe becomes constant where the substrate is smooth, the friction signal initially becomes large due to static friction and then becomes constant immediately as shown in FIG. 5B. The error signal and Z height signal are also constant. However, when the sample hits an obstacle such as a step, the friction signal and the error signal increase as shown in FIG. 2B, and the Z height signal increases with a delay. In this case, in order not to damage the probe or damage the sample, the movement is stopped until the above signal returns below the error signal set value, and a reaction force proportional to the increased friction signal and error signal is generated on the operation lever. Then, let the operator experience it or display it on the screen to slow down the moving speed.

Next, a method of avoiding when the sample is blocked by an obstacle such as a protrusion will be described. When the sample hits an obstacle such as a step (Fig. 2B), the friction signal and the error signal increase, and the Z height signal increases with a delay, and when the three signals continue to increase, the sample changes to the obstacle. It is likely that you have come into contact. In this case, stop moving once and move from the current moving direction to + /
The pressing direction to the sample is changed in the range of −45 degrees (FIG. 6), and the changes of the three signals are observed. The three signals start moving again in the direction of returning to the constant value before the obstacle contact.
When the movement starts normally, the direction is corrected and the movement in the intended direction on the screen 1 is performed again.

Next, how to deal with the case where the sample comes off the probe for some reason will be described. When moving normally, the friction signal shows a constant value. However, if the sample comes off the probe for some reason, the area that moves in contact with the substrate decreases, and the frictional force suddenly decreases as shown in FIG. In this case, the movement is stopped, the high-magnification measurement is performed at that point, the position and shape of the sample are reconfirmed, the pressing position on the sample is obtained again, and the movement is restarted.

[0022]

The effects of the present invention are listed below. 1. It became easy to find fine samples dispersed over a wide area on the substrate. 2. It became easy for the probe to come into contact with a fine sample dispersed over a wide area on the substrate. 3. Since the height signal, the friction signal and the error signal can be observed during the movement of the sample, the state of the moving sample can be easily estimated and the certainty of the sample movement is improved. 4. Since the height signal, friction signal, and error signal set values are determined while the sample is moving and the movement is interrupted when the set values are exceeded, the force above the set value does not work between the probe, sample, and substrate. Damage to the cantilever and damage to the sample and substrate were reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a system of the present invention.

FIG. 2A is a display example of height signals, error signals, and instantaneous values of friction signals, and FIG. 2B is a display example of time series values of Z height signals, error signals, and friction signals. (When you hit an obstacle at the right end)

FIG. 3A is a diagram of a scanning line by a raster scanning / sample finding / probe stop mechanism. (B) is a voltage-time diagram for raster scanning / sample discovery / probe stop mechanism.

FIG. 4A is a processing example by one-stroke writing scanning, and FIG. 4B is a processing example by raster scanning.

5A is a display example of a pressing position of a sample, and FIG. 5B is a display example of time series values of a Z height signal, an error signal, and a friction signal.
(At the start of sample movement)

FIG. 6 is an example of avoidance when the sample hits an obstacle.

FIG. 7 is a display example of time series values of a Z height signal, an error signal, and a friction signal. (When the sample comes off)

[Explanation of symbols]

1 Z coarse movement mechanism 2 XYZ fine movement scanner 3 Piezo diaphragm 4 Cantilever part 5 samples 6 sample table 7 laser beam 8 4-division position detector 9 preamplifier 10 preamplifier 11 Error amplifier 12 Z servo system 13 High-voltage amplifier 14 XY scanning controller 15 High-voltage amplifier 16, 17, 18 comparator 20, 21, 22 Analog-to-digital converter 30 bus lines 41 Computer 42 indicator 43 Digital-to-analog converter 44 Operation lever

Claims (8)

[Claims] 1. A scanning probe microscope which moves a sample after scanning the vicinity of the sample surface with a cantilever with a fine probe and obtaining the shape and physical property information of the sample surface from the deflection signal of the cantilever. At, the amount of deviation of the force acting between the sample and the probe from the initial setting (error signal)
The scanning probe microscope is characterized in that it has a mechanism for detecting a signal and displaying a signal proportional to the shift amount on a display, and a mechanism for transmitting the signal to the operation lever as a reaction force perpendicular to the sample surface (Z direction). 2. The scanning probe microscope according to claim 1, further comprising a mechanism for automatically adjusting a moving speed of the sample so that the displacement amount falls within a set range. 3. A scanning probe microscope that moves a sample after scanning the vicinity of the sample surface with a cantilever having a fine probe and obtaining the shape and physical property information of the sample surface from the deflection signal of the cantilever. In (1), a mechanism for detecting a frictional force acting between the sample and the probe while moving the sample and displaying a signal (friction signal) proportional to the frictional force on a display,
A scanning probe microscope characterized in that the operating lever has a mechanism for transmitting a reaction force parallel to the sample surface (XY direction). 4. The scanning probe microscope according to claim 3, further comprising a mechanism for automatically adjusting a moving speed of the sample so that the friction amount falls within a set range. 5. A sample cantilever with a fine probe (cantilever) scans the vicinity of the sample surface, obtains the sample surface shape and physical property information from the deflection signal of the cantilever, and then moves the sample or processes the sample surface. In a scanning probe microscope to be performed, a wide area image is captured while performing raster scanning at a low magnification for the purpose of discovering fine samples widely dispersed on the substrate, and the height signal immediately under the probe and the error signal and friction during scanning are acquired. When the signal exceeds a predetermined set value, a trigger signal is generated, a high-magnification image is taken at the point where the trigger signal is received, and it returns to the trigger point again and raster scanning is performed at a low magnification. Scanning probe microscope. 6. After low-magnification raster scanning, 1/2, 1/4 and 3 / between rasters for the purpose of interpolating scanning between rasters.
6. The scanning probe according to claim 5, wherein an initial offset position based on the bisection method is added to the scanning start position to detect a fine sample buried between the rasters while performing low magnification raster scanning. microscope. 7. A sample cantilever with a fine probe (cantilever) scans the vicinity of the sample surface, obtains the shape and physical property information of the sample surface from the deflection signal of the cantilever, and then moves the sample or processes the sample surface. In the scanning probe microscope to be performed, after determining the moving position and moving direction of the sample based on the measured low-magnification measurement screen, if an obstacle is encountered when moving the sample, the direction of pushing the sample with the probe is A scanning probe microscope characterized in that signals, error signals, and friction signals are changed so as to approach the state before encountering an obstacle to avoid the obstacle. 8. A sample cantilever with a fine probe (cantilever) scans the vicinity of the sample surface, obtains the sample surface shape and physical property information from the deflection signal of the cantilever, and then moves the sample or processes the sample surface. In the scanning probe microscope to be performed, after determining the moving position and moving direction of the sample based on the measured low-magnification measurement screen, the deviation of the moving sample from the probe is detected from the change of the friction signal. Scanning probe microscope.