JP2003177084A - Method for improving position accuracy in piezo stage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the position accuracy of a piezo stage. <P>SOLUTION: In method for improving the position accuracy of the piezo stage, the drive range of the piezo stage is specified, and the repetitive drive within the drive range is made in advance before the actual use. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the positional accuracy of a piezo stage, and more particularly to improving hysteresis and creep.

[0002]

2. Description of the Related Art In recent years, a near-field optical microscope, which is an optical microscope having a spatial resolution exceeding the diffraction limit, has been developed, and its application is expected as a microscope capable of observing a region below a light wavelength by a principle different from conventional ones. Has been done.

The measurement by the near-field optical microscope is carried out by utilizing the evanescent wave generated on the surface of the object. For example, when light is incident on a minute sample placed on a flat substrate at an angle that causes total internal reflection from the back surface of the substrate, all of the propagating light is reflected, but a surface called an evanescent wave near the surface of the substrate and the sample. Waves are generated. This surface wave is localized in a region within a light wavelength from the surface of the substrate and the sample.

When the probe processed into a sharp shape is gradually brought close to and brought into contact with the region of the evanescent wave generated on the sample surface, the evanescent wave is scattered. Since the intensity of this scattered light depends on the distance between the probe tip and the sample surface, scanning the sample surface while keeping the scattered light intensity constant gives information that accurately reflects the unevenness of the sample surface. To be At this time, scanning in the direction of the sample surface and control of the distance between the probe tip and the sample surface perpendicular thereto are performed by fixing the probe at a fixed position and driving the piezo stage on which the sample is placed.

In addition to such a near-field microscope, a probe microscope typified by an atomic force microscope, a scanning tunneling microscope, and the like measures minute irregularities on the sample surface, and therefore nanoscale minute positioning is possible. A piezo stage is often used.

[0006]

However, due to hysteresis and creep, the piezo stage is misaligned if it reciprocates in the same range a plurality of times.
There was a problem in absolute accuracy and reproducibility because it slipped even when trying to fix it in place. Especially in the probe microscope,
Since the stage is driven in an extremely small range on the nano scale, the problem is greatly affected.

As a method of solving this, there is a method of mounting a position sensor having a required accuracy, but there is a problem that the device becomes large and the response is delayed because it takes time to measure the position. . The present invention has been made in view of the above problems of the conventional art, and an object thereof is to improve the positional accuracy of the piezo stage.

[0008]

In order to achieve the above-mentioned object, a method for improving the positional accuracy of a piezo stage according to the present invention specifies a drive range of the piezo stage and actually uses repetitive drive within the drive range. It is characterized in that it is done in advance.

In the method, it is preferable that the repetitive driving is performed by repeatedly applying the maximum value and the minimum value of the applied voltage corresponding to the driving range.
Further, in the above method, a drive range is designated by the XY axes, the X-axis drive range is repeatedly driven in the X-axis direction from the start point of the designated XY drive range, and the Y-axis drive range is driven in the Y-axis direction from the start point. It is preferable to repeatedly drive.
Further, in the above method, it is preferable that the drive range is designated by the XY axes, and the drive is repeatedly performed from the start point of the designated XY drive range toward the end point on the diagonal line of the surface formed by the XY drive range. Further, in the above method, it is preferable that the drive range is designated by the XY axes and the comb-shaped drive is repeatedly performed from the starting point of the designated XY drive range so as to cover the entire XY drive range.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of a sample measuring unit of the above-mentioned near-field optical microscope. In the figure, the probe 10 is fixed at a fixed position, while the piezo stage 14 on which the sample table 12 is installed can be driven in the XYZ directions by an applied voltage according to an instruction from a stage controller (not shown).

In order to keep the distance between the surface of the sample 16 placed on the sample table 12 and the tip of the probe 10 constant when scanning the sample surface in the XY directions, as described above, depending on the unevenness of the sample. Feedback control in the Z direction is performed on the piezo stage 14 so that the scattered light intensity of the evanescent wave is constant. Then, when scanning the sample surface, Z
Asperity information on the sample surface can be obtained from the history information of the stage movement in the axial direction.

However, the piezo stage has a hysteresis characteristic, and for example, when the stage is driven along the X axis from a starting point to an ending point of a predetermined driving range, and then the stage is driven back to the original starting point. The applied voltage-displacement curve results in the displacement not matching for the same applied voltage as shown in FIG.

Further, the piezo stage has a creep characteristic, and even if the stage controller gives an instruction to stop the driving of the piezo stage, for example, displacement occurs from the original position with the passage of time as shown in FIG. . Therefore, these phenomena limit the positional accuracy of the piezo stage, and thus the accuracy of the unevenness information on the sample surface. For example, in a probe microscope or the like that performs measurement on the nanoscale, the limitation of the position accuracy due to these factors is actually a big problem.

As a result of intensive studies made by the present inventors to solve this problem, as a result of repeating driving within a specified driving range before actual measurement, It was found that the hysteresis and creep of the stage during measurement can be significantly suppressed.

That is, for example, as shown in FIG. 4, by repeatedly and repeatedly applying the maximum applied voltage and the minimum applied voltage within a designated drive range, the position of the piezo stage is stabilized and the position accuracy is greatly improved. To be done. The number of repetitions is
Depending on the case, a clear effect can be recognized by performing the process about 5 times, and an increase in the number of times improves the positional accuracy.

Therefore, if, for example, the driving range of the stage is set and then repeatedly driven within the driving range by an instruction of a measurer or automatically, and then the measurement is started, if the driving range is about 10 times, for example. Since it does not require a long time, it is possible to greatly improve the position accuracy with a simple operation and without requiring a large-scale device. In addition, when changing the setting of the driving range, it is necessary to redo the above-mentioned operation again. However, if the setting of the driving range is not changed once before the measurement, the measurement is continued with the position accuracy improved. be able to.

When the drive range of the stage is designated by the XY axes, the following method can be cited as a repetitive drive for improving the position accuracy. The first method is shown in FIG.
As shown in (A), after the drive range is first designated, the stage is driven to the starting point of the designated XY drive range, and then the X-axis driving range is repeatedly driven in the X-axis direction, and the stage is driven to the starting point. After that, the driving range of the Y axis is repeatedly driven in the Y axis direction. This stabilizes the position accuracy during use in both the X and Y axis directions.

In the second method, as shown in FIG. 5B, after the drive range is designated, the stage is driven to the starting point of the designated XY drive range, and then the XY drive range is formed. This is a method of repeatedly driving on the diagonal line of the surface toward the end point.

In the third method, as shown in FIG. 5C, the drive range is first designated, the stage is driven to the starting point of the designated XY drive range, and then the entire XY drive range is covered. This is a method of repeatedly performing comb-like driving.

The method for improving the positional accuracy of the piezo stage according to the present invention has been described above. When the sample is fixed to such a stage, the fixing means described below is preferably used.

[0021]Sample fixing means on stage Position accuracy at the nano level is required, such as the proximity described above.
For probe microscopes such as field optical microscopes,
As a method of fixing the sample on the stage such as
Using frictional friction, sticking with double-sided tape
Know how to attach it, and how to absorb it with grease etc.
Has been.

However, the method of stopping by using mechanical friction is effective only for the stage and the sample having a large friction coefficient,
Any other combination will cause the sample to slip. In addition, if inertial force is applied due to abrupt movement of the stage, the position will shift.

On the other hand, in the method using a double-sided tape or grease, an adhesive material or the like adheres to the sample and contaminates the sample. Also, the double-sided tape and grease are consumed, so it is necessary to supply them for each measurement.

Therefore, a gel-like adsorbent is used as a sample fixing stage for the purpose of providing a sample fixing means capable of surely fixing the sample to the stage and not contaminating the sample at the time of fixing. The characteristic sample fixing stage will be described below.

FIG. 6 shows a usage state of a sample fixing stage using a gel-like adsorbent. As shown in the figure, a sample fixing stage 22 made of a gel-like adsorbent is installed on a stage 20 such as a piezo stage. The sample 24 is placed and fixed on the fixing stage 22. The gel-like adsorbent has an excellent adsorbing ability, and the contact portion between the sample and the gel is in close contact, so that the sample is sufficiently fixed. Also,
Since the gel does not substantially adhere to the sample, it does not stain the sample and is easily removable.

Examples of the gel-like adsorbent include mats and solids that increase the coefficient of friction, and more specifically, silicone gel, silicone rubber, and gels of other organic polymer cross-linking materials.

If a transparent gel-like adsorbent is used, it is possible to perform visual observation and microscopic observation from below the sample. Alternatively, as shown in FIG. 7, by arranging the gel-like adsorbent only on the edge side of the sample, the visual observation and the microscopic observation from the lower side of the sample are possible.

Further, by electrically contacting the fixing stage with the sample using a conductive gel-like adsorbent,
It is applicable to M and the like. As such a conductive gel-like adsorbent, a metal component is dispersed at high density in a resin (polyolefin-based, polyester-based, fluorine-based, etc.),
An example is a highly conductive plastic sheet (for example, one having a volume resistivity value of the order of 10 ⁻³ to 10 ⁻⁴ Ω · cm).

If the sample fixing stage described above is used, the sample can be securely fixed to the stage without being contaminated, and the sample can be easily attached and detached.

[0030]

As described above, according to the method of the present invention, the repeated driving within the designated driving range is performed before the actual use, so that the hysteresis and the creep are significantly suppressed. To be As a result, it is possible to improve the positional accuracy of the stage without requiring a large-scale device and without requiring much time for positioning.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a sample measuring unit of a near-field optical microscope.

FIG. 2 is a graph showing a hysteresis characteristic of a piezo stage.

FIG. 3 is a graph showing creep characteristics of a piezo stage.

FIG. 4 is an explanatory diagram showing an embodiment of the method of the present invention.

FIG. 5 is an explanatory diagram showing an embodiment of the method of the present invention.

FIG. 6 is an explanatory diagram showing a usage mode of a sample fixing stage using a gel-like adsorbent.

FIG. 7 is an explanatory diagram showing a usage mode of a sample fixing stage using a gel-like adsorbent.

[Explanation of symbols]

10 probes 12 sample table 14 Piezo Stage 16 samples 20 stages 22 Sample fixing stage 24 samples

Claims (5)

[Claims] 1. A method for improving the positional accuracy of a piezo stage, characterized in that a drive range of the piezo stage is designated and repetitive driving within the drive range is performed in advance before actual use. 2. The method for improving the positional accuracy of a piezo stage according to claim 1, wherein the repetitive driving is performed by repeatedly applying a maximum value and a minimum value of an applied voltage corresponding to the driving range. . 3. The method according to claim 1, wherein a drive range is designated by the XY axes, the X-axis drive range is repeatedly driven in the X-axis direction from the designated XY drive range starting point, and the Y-axis starts from the starting point. A method for improving the positional accuracy of a piezo stage, which comprises repeatedly driving a Y-axis drive range in a direction. 4. The method according to claim 1, wherein a driving range is designated by XY axes, and the driving is repeatedly performed from a starting point of the designated XY driving range toward an end point on a diagonal line of a plane formed by the XY driving range. A method for improving the positional accuracy of a piezo stage, characterized by: 5. The method according to claim 1, wherein a drive range is designated by the XY axes, and the comb-shaped drive is repeated so as to cover the entire XY drive range from the starting point of the designated XY drive range. Method for improving the position accuracy of the piezo stage.