JPH0814481B2 - Object surface condition access system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an object surface state access system, and more particularly to an object surface state access system suitable for accessing a wide area with atomic order resolution.

[Conventional technology]

An apparatus for measuring the surface state of a target object by detecting a minute current flowing between the target object and the probe is
Depending on the distance between the sample and the probe, it is called a topographic eye and scanning tunneling current microscope (STM). Of these, STM has high resolution and is capable of observing the surface of the atomic order. For STM, see, for example, U.S. Pat. No. 4,434,393 or Surf Science 126 (1983), page 236.
244 (Surface Science126 (1983) pp.236-244), Surf Science 152/153 (1985) pp. 17-26
Page (Surface Science 152/153 (1985) pp.17-26).

[Problems to be solved by the invention]

The above-mentioned prior art is a case where the target object is fixed and the measurement range is small because the target object surface is scanned by the fine movement mechanism of the probe, and the purpose is to inspect for defects such as film defects generated by the MBE device or the like. Has a problem that the formed film cannot be sufficiently evaluated because the measurement range is limited.

Further, when the above conventional technique is applied to an information storage device, there is a problem that the storage capacity becomes insufficient because the scanning range is very small.

Therefore, an object of the present invention is to provide a system capable of accessing the surface state of an object in a wide area with a resolution of atomic order.

[Means for solving problems]

The above-mentioned purpose is to mount either the target object or the probe fine movement mechanism on the XYZ coarse movement mechanism (stage) that can move in three directions orthogonal to the target object, has a long stroke, and is equipped with highly accurate positioning control means. Then, after the relative positioning of the sample surface and the probe is performed by this stage, the fine movement scanning is performed by the probe to access the surface state, and the control means of the probe fine movement mechanism is operated while the stage is fixed. A means (observation mode) for obtaining information on the surface state of the target object by scanning the probe, and when the relative position between the probe and the target object is moved in the target object plane direction by the stage, the probe is at the same position as the target object. This is achieved by providing a control means (moving mode) for following while keeping the above.

[Action]

When it is necessary to access the surface state of the target object over a region wider than the range of movement of the probe by the fine movement mechanism, probe position control and XYZ stage position control must be linked. Therefore, after the probe scans and measures the moving range at a certain position on the target object surface, the probe position in the vertical direction is fixed to the target object surface.
At the same time, the control means for in-plane movement of the probe is switched so that the minute current flowing through the probe can be positioned so as to be constant.

Next, the XYZ stage carrying the target object or probe is moved. At this time, the probe moves following the target object and returns to the measurement scanning start point within the movement range of the probe. Since the movement of the stage is finished and fixed, the vertical position control means of the probe is restored again.
After that, similarly, in this state, the surface of the target object is scanned and measured.

Further, when the stage moves, the sample may move in the vertical direction due to its guiding accuracy, and in this case, it is necessary to control the probe in the vertical direction. Therefore, when the probe follows the target object, it is necessary to scan the probe in a minute area at high speed to measure the surface state, and recognize the shape to allow the probe to follow the movement of the sample.

If the movement accuracy of the target object and probe is very good, the state data of the vicinity of the positioning before and after the movement is stored, and after moving the sample and the probe by applying the same target signal, the relative position of both is moved. It is effective to correct the deviation by comparing the state data and position the probe in the same positional relationship as before the movement.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a plan view of this embodiment, and FIG. 2 is a front view. As shown in the figure, 1 is a Y-axis actuator of the coarse movement mechanism (stage), 2 is a Y-axis rod, 3 is a rod for avoiding interference between the X-axis direction and the Y-axis direction, 4 is a target object mount, and 5 is a top. Table, 6 is X-axis actuator,
7 is an X axis rod, 8 is an X table, 9 is a base, 10 is an X
Axis mirror, 11 Y axis mirror, 12 wedge Z axis drive mechanism, 13 Z axis actuator, 14 Y table, 15 Y
A shaft slide guide mechanism, 16 is a fine movement mechanism, 17 is a probe (probe), 18 is a mount, and 19 is a roller. Here, the fine movement mechanism 16, the probe 17, and the mount 18 are not shown in FIG. The operation of the XY stage type positioning device disclosed in FIG. 1 will be described below. The sample, which is the object to be measured, is mounted on the sample mount 4. And when positioning in the X-axis direction, X
Axial actuator 6 generates thrust and drives x-table 8 via X-axis rod 7. Here, the x-axis actuator may be a linear motor or a rotary motor to which a transmission means such as a ball screw is added. The movement amount of the X table is detected by an X-axis mirror 10 attached to the top table 5 and a precision position detecting means (not shown) such as a laser measuring system, and a control circuit for inputting the operation amount to the X-axis actuator 6. Feed back (not shown). Similarly, when the target object is positioned in the Y-axis direction, the thrust force generated by the Y-axis actuator 1 is transmitted to the Y-axis rod 2 and the rollers arranged so as to sandwich the rod 3 so as not to interfere with the movement of the X-axis. The y-table 14 is driven via 19 and rod 3. The amount of movement of the Y table is detected by the Y-axis mirror 11 and the laser measuring system (not shown), and is fed back to the Y-axis control circuit (not shown). Here, the movement direction of the Y table is guided by a slide guide mechanism 15 provided on the X table 8 and having a slider such as a louron. 15a and 15b are used for suppressing pitching, and 15c is used for suppressing yawing.

Further, the target object is vertically positioned by moving the wedge-shaped Z-axis drive mechanism 12 by the Z-axis actuator 13 and moving the top table 5 up and down.

By mounting the target object on the XY stage that is movable in the three-axis directions as described above, the sample can be positioned at one point within the movement range of the fine movement mechanism.

The XYZ stage disclosed in this embodiment may include a rolling guide mechanism, a static pressure levitation guide mechanism, a magnetic levitation guide mechanism, etc. as the guide mechanism. Further, the arrangement of the actuators may be such that the actuators of each shaft are directly attached to the lower side of each driven table. or,
As the position detecting means of each table, a detector such as a linear scale or an encoder may be used in addition to the laser length measurement of this embodiment.

On the other hand, the fine movement mechanism 16 is attached to the pedestal 18, and the probe 17 attached to the tip of the fine movement mechanism is positioned on the target object in angstrom order. Fig. 3 shows the fine movement mechanism
16 shows in detail, 21 is a displacement element for x-axis fine movement (for example, a piezoelectric element such as PZT or an electrostrictive element), 22
Is a y-axis fine movement displacement element, 23 is a z-axis fine movement displacement element, 24 is an x-axis joint, 25 is a y-axis joint, 26 is a z-axis joint, 27 is a block, and 28 is a fine movement mechanism base. The probe 17 is driven via a joint by a displacement element provided for each axis.

FIG. 4 is a block diagram showing an embodiment of the control means of the XYZ stage of the present apparatus. Reference numeral 31 is a target value generation circuit, 32 is a comparison circuit, 33 is a stabilization compensation circuit, and 34 is an actuator. A driving amplifier, 35 is an actuator, 36 is a table, and 37 is a position detector. This block diagram is X
It is common to each axis, Y axis, and Z axis control means. Target value generation circuit 31
Output is compared with the position of the table 36 detected by the position detector 37 by the comparison circuit 32, the obtained deviation is stabilized by the stabilization compensating circuit 33, and then amplified by the amplifier 34, and then the actuator 35. Is input to. Actuator 35 generates thrust according to the entered value and
Drive 36 to position.

FIG. 5 is a block diagram showing the first embodiment of the control means of the fine movement mechanism of the present apparatus, and 41 is an x-axis (or y-axis) target value generation circuit. 42 is a switching circuit, 42
Reference numeral 42a indicates a circuit terminal in the observation mode and reference numeral 42b indicates a circuit terminal in the movement mode. 43 is an x-axis (y-axis) fine movement displacement element drive amplifier, 44 is an x-axis (y-axis) fine movement displacement element, 45 is a probe, 46 is a z-axis target value generation circuit, 47 is a comparison circuit, and 48 is an integrator , 49 is a hold circuit, 50 is a switching circuit, 50a is a circuit terminal in observation mode, 50b is a movement mode circuit terminal, 51 is a displacement element drive amplifier for Z-axis fine movement, 52 is a displacement element for Z-axis fine movement, and 53 is between probe sample. A minute current detection circuit, 54 is an amplifier, and 55 is a tracking control circuit.

In this embodiment, when the target object is fixed and the surface of the sample is observed by scanning the probe, the observation mode is set, the sample is moved by the XY stage, and the probe is moved within the fine movement mechanism moving range. If you are moving to the move mode.

In the observation mode, the probe is scanned in the x-axis or y-axis direction while controlling the voltage applied to the Z-axis fine movement displacement element so that the minute current between the probe target objects becomes constant. The Z-axis target value generation circuit 46 and the signal detected by the detector 53 for the minute current between the probe samples and amplified by the amplifier 54 are compared by the comparison circuit 47 and integrated by the integrator 48. , The Z-axis fine movement displacement element 52 is amplified by the Z-axis fine movement displacement element drive amplifier 51 via the observation mode circuit terminal 50a.
Drive. On the other hand, the x-axis (or y-axis) target value generation circuit 41
The target value generated from is amplified by the displacement element drive amplifier 43 for x-axis (y-axis) fine movement via the observation mode circuit terminal 42a,
The x-axis (y-axis) fine displacement element is driven. Then, the probe is scanned in the x-axis (y-axis) direction. At this time, the distance between the probe target objects changes depending on the surface state of the target object, and the minute current changes. At this time, since the displacement element for Z-axis fine movement is controlled so that the minute current is constant,
By measuring the voltage applied to the displacement element, the surface state of the target object can be observed, and by scanning in the x-axis and y-axis directions, information on the three-dimensional surface state of the target object can be obtained.

When the surface of the target object is relatively smooth, the voltage applied to the Z-axis fine movement displacement element is constant (that is, the average gear gap between the probe target objects is constant), and the x-axis and Information on the surface state of the target object can be obtained by scanning in the y-axis direction and detecting a minute current between the probe target objects.

By the way, the atomic spacing of a silicon crystal (Si (111) 7 × 7 structure) is about 4Å (angstrom), and in order to observe these atomic arrangement states with high resolution, the scanning range of the probe, that is, the stroke of the fine movement mechanism. In one example, the limit is about 1000Å (0.1 μm). In this case, for example, the resolution of 12 bits is 0.24Å. Therefore,
0.1 μm maximum due to full stroke scanning of fine movement mechanism
Observation on all sides is possible once.

On the other hand, in the movement mode, when it is necessary to observe a wide area (for example, several μm to several mm square) that cannot be covered by the scanning range of the fine movement mechanism, the scanning ranges of the fine movement mechanism are connected one after another to cover a large area. Used for scanning. A method of connecting the scanning areas will be described with reference to FIG.

FIG. 6 is a diagram showing the surface area of the target object 70.
Indicates a region scanned first by the fine movement mechanism, and B indicates a region connected to the region A and scanned next. Further, although the regions are connected one after another, these displays are omitted. Also, the area C
Indicates the area covered by the stroke of the XY stage.

First, for example, the scan of the first minute area A is performed as O → P.
→ Q → R → …… → S in order to create an observation image.
Next, in the area A, the adjacent area B to be scanned next
The probe is moved to the scanning start point O ′ (in the present embodiment, the area shifted in the X direction) by the fine movement mechanism. Next, in the above-described embodiment, the stage is moved in the minus (-) direction of X within the stroke range of the fine movement mechanism. At this time, the fine movement mechanism is controlled so that the probe holds the same position of the target object. To do.

In the first embodiment, the probe is placed in the adjacent region B.
When the minute current between the probe target objects becomes constant by moving to the scanning start point O'of
The voltage applied to the displacement element 52 for fine axis movement is held. At the same time, the x-axis and y-axis drive circuits are switched to the movement mode, and the minute current is constant (that is, the distance between the probe target objects is constant).
The x-axis and y-axis fine displacement elements are driven and controlled so that

FIG. 7 is a diagram showing the principle of causing the probe 17 to follow the movement of the XY stage in the first embodiment, and FIG. 8 is a flow chart showing the operation of the first embodiment. Is. In FIG. 7, reference numeral 70 is an enlarged view of the surface of the target object fixed on the XY stage. The broken line indicates that the sample surface is (-Δ
x) indicates a state of being moved. In Figure 7, when the Giyatsupu probe and the target object at the scan start point O 'of the area B and h _0, Giyatsupu after the stage has moved (-Δx) becomes (h ₀ + Δh). At this time, the tracking control circuit is used to determine the direction in which the probe should move in the plane.
At 55, the probe is slightly vibrated (vibration width Δw) in the plane, and the inclination of the unevenness on the surface of the target object is determined from the direction of the change of the minute current. Based on the result, the moving direction of the probe is determined. For example, in FIG. 7, the gear is Δh
Since it has increased,
It is sufficient to move the probe in the (X) direction and continue the correction until the gear becomes h ₀ .

As a result, even if the target object is moved by the XY stage, the probe continues to follow a certain point in the target object, and when the scanning mode is switched again and scanning is performed,
Data that is continuously connected to the previous scan data is obtained,
Therefore, the surface condition of the target object in a wide area can be observed.

Further, FIG. 9 is a control system block diagram of the second embodiment in the follow-up mode of the fine movement mechanism of this apparatus, and FIG. 10 is a flow chart showing the operation thereof. In FIG. 9, 61 is a reference surface data generation circuit, 62 is a comparison circuit,
63 is a matching circuit, 64 is an X-axis (Y-axis) amplifier, and 65 is X
An axis (Y-axis) displacement element, 66 is a probe, 67 is a minute range scanning signal generation circuit, 68 is a surface shape detection circuit, and 69 is a sample movement amount by the XY stage. Also, the vertical displacement element is
The surface shape data is obtained by controlling the minute current generated between the sample and the probe to be constant and inputting the displacement of the displacement element according to the surface shape to the surface shape detection circuit 68. Next, regarding the control method of the displacement element in the horizontal plane, the signal generated by the minute range scanning signal generation circuit 67 drives the displacement element 65 through the amplifier 64 to drive the probe 66 to a certain set minute range. Is scanned at high speed, and the surface shape detection circuit 68 obtains the shape data of the surface of the target object.
In the reference surface data generation circuit 61, the area B in FIG.
Target object surface data in the vicinity of the scanning start point O'of is stored. Here, when the target object moves by the XY stage, this sample movement amount 69 becomes a disturbance in this control system. Therefore, the surface shape data obtained by high-speed scanning deviates from the reference data. The comparison circuit 62 calculates this deviation amount, and the probe 66 is passed through the amplifier 64 and the displacement element 65.
By moving the, the probe can follow a certain position of the sample.

Further, FIG. 11 is a control system block diagram of the third embodiment of the control system in the follow-up mode of the present apparatus, and FIG. 12 is a flow chart showing its operation. In this embodiment, the same signal (required movement amount l ₀ ) is input to the XY stage and the probe fine movement mechanism in the follow-up mode. The input signal drives the stage and the probe by the same distance through the respective amplifiers and motors. However, in reality, since the positioning resolution of the stage is insufficient (for example, about 0.01 μm even when it is very good) as compared with the fine movement mechanism, the movement amount of the stage and the movement amount of the probe do not match. So after moving,
The position of the probe is corrected by detecting the surface shape near the positioning and comparing it with the reference data. As a result, even if the stage is moved, the probe can move while maintaining the same position, and the surface shape of a wide range of the target object can be measured.

Further, all of the above embodiments are examples in which the target object is mounted on the XYZ stage side, and the fine movement mechanism including the probe is fixed, but how can the coarse movement function of the XYZ 3 axes be applied to the target object side or the probe fine movement mechanism side? It is needless to say that the present invention can be applied even if they are shared. For example, a fine movement mechanism including a probe may be mounted on an XYZ stage and a target object may be fixed. Alternatively, the probe fine movement mechanism side may include only the Z-axis coarse movement function, and the target object may be mounted on the XY coarse movement stage.

Further, in the above-mentioned embodiment, the case where the observation of the surface state (particularly the shape) of the target object is mainly used is explained, but also when the information storage device utilizing the state of the target object surface is used, Of course, the present invention can be applied. Figure 13 shows some examples of methods for storing information on the surface of a target object. In FIG. 13, (1) is a method of providing ultra-small pits or micro-projections on the surface of the target object 70 by physical or chemical means, (2) is a method of adsorbing ultrafine particles 71, and (3) is This is a method of utilizing the difference in work function of the thin film 72. In addition, 17 shows a probe. The information recorded by the above method can be detected by measuring the minute current between the probe target objects as described above. According to this method, extremely high-density storage can be performed, and a wide area can be utilized by applying the present invention, so that an extremely large-capacity storage device can be expected to be realized.

〔The invention's effect〕

As described above, according to the present invention, either the target object or the probe fine movement mechanism has a relatively long stroke.
It is mounted on an XYZ stage, and after the target object surface and the probe are positioned relative to each other by this stage, the surface can be observed over a wide area by observing the surface by fine scanning of the probe. Further, according to the present invention, since the control system for continuously connecting the moving ranges of the fine movement mechanism is provided,
This has the effect that the surface of the object to be measured can be continuously observed over a wide area.

[Brief description of drawings]

FIG. 1 is a top view of the apparatus of one embodiment of the present invention, FIG. 2 is a side view, FIG. 3 is a detailed view of the fine movement mechanism of the present invention, and FIG. 4 is a control block diagram of the XYZ stage of the present invention. FIG. 5 is a control block diagram of the first embodiment of the present invention, FIG. 6 is a diagram showing a region of a target object surface, FIG. 7 is a diagram showing a target object surface and a probe, and FIG. 9 is a flow chart showing the control system of the first embodiment, FIG. 9 is a control block diagram of the second embodiment, FIG. 10 is a flow chart showing the control system of the second embodiment, and FIG. 11 is the third. Control block diagram of Example, No. 12
The figure shows a flow chart representing the control system of the third embodiment,
FIG. 13 is an example of the information reporting method. 1 ... y-axis actuator, 2 ... y-axis rod, 3 ...
Rod, 4 ... Target object mount, 5 ... Top table, 6 ... X-axis actuator, 7 ... X-axis rod, 8
... x table, 9 ... base, 10 ... x-axis mirror, 11
…… Y-axis mirror, 12 …… Wedge-shaped Z-axis drive mechanism, 13 ……
z-axis actuator, 14 ... y table, 15 ... y-axis slide guide mechanism, 16 ... fine movement mechanism, 17 ... probe, 18 ...
… Frame, 19 …… Roller, 21 …… Displacement element for x-axis fine movement, 22
...... Y-axis fine movement displacement element, 23 …… Z-axis fine movement displacement element,
24 …… x-axis joint, 25 …… y-axis joint, 26 …… z-axis joint, 27
...... Block, 28 ...... Fine movement mechanism base, 31 ...... Target value generation circuit, 32 ...... Comparison circuit, 33 ...... Stabilization compensation circuit, 34 ...
... actuator drive amplifier, 35 ... actuator, 36 ... table, 37 ... position detector, 41 ... x-axis (y-axis) target value generation circuit, 42 ... switching circuit, 43 ... x-axis (y Axis) Displacement element drive amplifier for fine movement, 44 ... x axis (y
Axis) Fine movement displacement element, 45 …… probe, 46 …… z axis target value generation circuit, 47 …… comparison circuit, 48 …… integrator, 49 …… hold circuit, 50 …… switching circuit, 51 …… z Displacement element drive amplifier for fine axis movement, 52 ...... Displacement element for z axis fine movement, 53 ...... Micro current detection circuit between probe target objects, 54 ...... Amplifier, 55 ...
... Tracking control circuit, 61 ... Reference surface data generation circuit, 62 ...
… Comparison circuit, 63 …… Butting circuit, 64 …… x axis (y
Axis) amplifier, 65 ... x-axis (y-axis) displacement element, 66 ... Probe, 67 ... Micro range scanning signal generation circuit, 68 ... Surface shape detection circuit, 69 ... Target object movement amount, 70 ... Target object,
71 …… Ultrafine particles, 72 …… Thin films.

Claims (4)

[Claims] 1. A probe fine movement mechanism for moving a probe in a minute range in three orthogonal directions and a control means therefor, and a detection means for detecting a minute current flowing when a voltage is applied to the probe and brought close to a target object. In an object surface state access system including an XYZ coarse movement mechanism for positioning the relative position between the probe fine movement mechanism and the target object with a relatively long stroke in orthogonal three axis directions, and a control means therefor, a coarse movement mechanism is provided. In a fixed state, the fine movement mechanism scans the probe in two directions along the surface of the target object (xy directions) and at the same time detects the current flowing through the probe, or detects the target object in the direction perpendicular to the target object (z direction). The observation mode control means for obtaining information on the surface state of the target object by finely controlling the probe in accordance with the unevenness of the surface and the coarse movement mechanism in the X or Y direction. An object surface characterized by having a movement mode control means for controlling the fine movement mechanism to follow the movement of the coarse movement mechanism so that the probe holds the same position on the target object surface while moving within the stroke of the fine movement mechanism. State access system. 2. The movement mode control means according to claim 1, after the scanning of the minute area A by the fine movement mechanism is completed, the probe is placed in an area where the minute area A and the next minute area B to be scanned overlap. The probe moves following the movement of the coarse movement mechanism while holding the voltage applied to the Z-axis fine movement displacement element and controlling the xy position of the probe by the fine movement mechanism so that the minute current between the probe samples becomes constant. An object surface state access system characterized by the following. 3. The movement mode control means according to claim 1, after the fine movement mechanism finishes scanning the minute area A, sets the probe in the overlapping area of the minute area A and the next minute area B to be scanned. The amount of probe deviation was determined by comparing the reference surface condition data obtained as a result of scanning the fine movement mechanism around the next scanning start point with the surface condition data obtained by scanning the fine movement mechanism while the coarse movement mechanism was operating. An object surface state access system characterized in that a probe follows the movement of a coarse movement mechanism while performing correction control by a fine movement mechanism. 4. The moving mode control means according to claim 1, after the scanning of the minute area A by the fine movement mechanism is finished, the movement mode control means places the probe in an area where the minute area A and the next minute area B overlap. After moving, scan the vicinity of the next scanning start point with the fine movement mechanism to obtain reference surface state data, move the fine movement mechanism and the coarse movement mechanism by the required movement amount, and then obtain the surface state obtained by scanning with the fine movement mechanism. An object surface state access system, characterized in that a displacement amount of a probe is obtained by comparing data and the reference surface state data, and a position is corrected by a fine movement mechanism.