JPH11281543A - Sample stage and particle size-measuring apparatus using the sample stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly readjust an up-down positional deviation of a face to be measured by moving a sample-holding plate so that the position information obtained by a position determination means becomes a predetermined true position. SOLUTION: When an angle of a face to be measured is shifted from when an optimum focal position is set, two keen position detectors PSD 142, 144 are arranged so as to correctly obtain a positional information. A position is determined with taking into consideration an angle information of the face to be measured which is obtained from an output voltage difference C of the detectors. The obtained angle information is compared by a CPU 246 with the angle when the optimum focal position is set. When the obtained angle information is judged to be shifted from a predetermined angle, a position of the face to be measured when regularly reflecting is estimated from the angle information and an output voltage A of the PSD 142, and set as a true position of the face to be measured. On the contrary, when the angle information is judged not to contain errors, a temporary position information is set as a true position information. The obtained position information and the position information when the optimum focal position is set are compared by the CPU 246. If the obtained position information is judged to error, a control circuit 138 makes a rectangular movement means 148 move a sample-holding plate 128 in a Z direction so that the position information determined by the CPU 246 becomes the optimum focal position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample stage and a particle size measuring apparatus using the same, and more particularly to an improvement in a mechanism for controlling the vertical position of the sample stage.

[0002]

2. Description of the Related Art Conventionally, for measuring a particle diameter on the order of nanometer on a silicon wafer on which a pattern is not formed, for example,
Various particle size measuring devices are used.

[0003] As shown in FIG.
0 is the light source 12 for emitting the laser light L1, and the laser light L
1, a sample stage 18 on which a sample 16 such as a silicon wafer is loaded, a condenser 22 for condensing Rayleigh scattered light L2 of laser light L1 from fine particles 19 on a detector 20, A detection circuit 24 is provided for measuring the particle diameter from the intensity change of the scattered light obtained by the detector 20. By configuring the particle size measuring device 10 in this manner, the diameter of the fine particles 19 attached to the sample 16 such as a silicon wafer can be measured.

When detecting the fine particles 19 as foreign matter on the silicon wafer, it is necessary to scan the convergent laser beam L1 in an arbitrary direction on the surface to be measured, that is, in the XY directions. To this end, the sample stage 18 includes a sample holding plate 28 on which the sample 16 is loaded, an X-axis motor 30, a Y-axis motor 32,
Drive circuits 34 and 36 and a control circuit 38 are provided. Then, the control circuit 38 gives instructions to the drive circuits 34 and 36 to control the operations of the X-axis motor 30 and the Y-axis motor 32, thereby moving the sample 16 on the sample holding plate 28 in the XY directions. Thus, the laser beam L1 is scanned in the XY directions. Note that the regular reflection light L3 has a structure to exit the light collector 22.

[0005]

The fine particles 19
In order to detect the Rayleigh scattered light L2, the surface to be measured must be focused. For this reason, in general,
Prior to the measurement, a specific portion of the surface to be measured was focused.

However, after the focusing, the particle size measuring apparatus 10 using the conventional sample stage 18 generally performs detection while moving the sample stage 18 only in the X and Y directions. If the surface has undulation or the accuracy of the sample stage 18 is poor, the vertical position of the surface to be measured is shifted from the optimum focus position in the Z direction during scanning. For this reason, it is necessary to perform the measurement in a state where the focus is not on the surface to be measured, or to manually perform a delicate readjustment for focusing by stopping the measurement,
It was troublesome.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to accurately readjust even if the vertical position of the surface to be measured is shifted from a predetermined position. It is an object of the present invention to provide a sample stage which can easily perform the measurement and a particle size measuring device using the same.

[0008]

In order to achieve the above-mentioned object, a sample stage according to the present invention comprises a parallel moving means for moving a sample holding plate for holding a sample in a direction parallel to a surface to be measured of the sample. In the sample stage provided with the above, a right angle moving means, a position detecting means, an angle detecting means, a position determining means, and a stage control means are provided.

The right-angle moving means is capable of moving the sample holding plate in a direction perpendicular to the surface to be measured. The position detecting means is for receiving reflected light from the surface to be measured and obtaining temporary position information of the surface to be measured from the light receiving position of the reflected light. The angle detecting means is for receiving the reflected light and obtaining angle information of the surface to be measured from a light receiving position of the reflected light.

The position determining means compares the angle information obtained by the angle detecting means with predetermined angle information. If it is determined that there is no error, the position information obtained by the position detecting means is used as the true position. Information, and when it is determined that there is an error, the position information obtained by the position detecting means is calibrated based on the error to be true position information. The “predetermined angle information” here refers to, for example, the angle of the surface to be measured at the time of setting the optimum focus position.

The stage control means moves the sample holding plate by the right-angle moving means so that the position information obtained by the position determining means becomes a predetermined position. In order to achieve the above object, a sample stage according to the present invention is characterized in that a sample holding plate for holding a sample is provided at a right angle with a sample stage provided with a parallel moving means capable of moving the sample holding plate in parallel to a measured surface of the sample. It is characterized by comprising a moving means, an angle changing means, an angle detecting means, a position detecting means, and a stage control means.

The right-angle moving means is capable of moving the sample holding plate in a direction perpendicular to the surface to be measured. The angle changing means can change the angle of the sample holding plate. The angle detection means is for receiving reflected light from the surface to be measured and obtaining angle information of the surface to be measured from a light receiving position of the reflected light.

The position detecting means is for receiving the reflected light and obtaining position information of the surface to be measured from the light receiving position of the reflected light. The stage control means, so that the angle information obtained by the angle detection means is a predetermined angle,
After the sample holding plate is tilted by the angle changing unit, the sample holding plate is moved by the right-angle moving unit so that the position information obtained by the position detecting unit becomes a predetermined position.

In the sample stage, a reflected beam from the surface to be measured is divided into two parts, one of which is incident on the position detecting means and the other is incident on the angle detecting means. It is preferable to provide In order to achieve the above object, a particle size measuring apparatus according to the present invention is characterized in that the sample stage according to the present invention includes a particle size measuring means. The particle size measuring means detects the Rayleigh scattered light from the particles while irradiating the surface to be measured with the convergent laser light and scans the particles, and measures the particle size from the intensity of the scattered light from the particles.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 2 is a diagram showing a schematic configuration of a particle size measuring apparatus according to a first embodiment of the present invention. The portions corresponding to those in FIG. 1 are denoted by reference numeral 100, and description thereof is omitted. A particle size measuring device 110 shown in FIG.
14, the detector 120, the condenser 122, and the detection circuit 1
24, an X-axis motor 130, a Y-axis motor 132, and drive circuits 134 and 136 as horizontal moving means.

The convex lens 114 converges the laser beam L1 from the light source 112 and irradiates the laser beam L1 onto the surface to be measured of the sample 116 (for example, the incident angle is 45 degrees with respect to the surface to be measured). The condenser 122 is composed of, for example, an elliptical mirror, and condenses the Rayleigh scattered light L2 of the converged laser light L1 from the surface to be measured to one point and collects it at the detector 120.

The detector 120 comprises, for example, a photomultiplier tube (PMT), detects the Rayleigh scattered light L2 from the condenser 124, and converts it into an electric signal proportional to the scattered light intensity. The X-axis motor 130 and the Y-axis motor 132
For example, the sample holding plate 128 includes a stepping motor.
Can be moved within a certain range in the X and Y directions.

By configuring the particle size measuring device 110 as described above, the diameter of the fine particles 119 attached to the sample 126 such as a silicon wafer can be measured. A feature of the present invention is that even when the vertical position of the surface to be measured is shifted from the optimum focus position, it can be easily readjusted accurately. First, a vertical movement unit 140 is provided.

The vertical moving means 140 includes, for example, a Z-axis motor 148 composed of, for example, a stepping motor and a driving circuit 150, and can move the sample holding plate 128 in the Z direction within a certain range according to an instruction from the control circuit 138. Things. Further, in the present embodiment, as shown in FIG. 3, the beam splitter 141, the position detecting means 142, the angle detecting means 144, the determining means 146, the voltage data storing means 147, and the control circuit 13 which is a stage controlling means.
8 is provided.

As shown in the figure, the beam splitter 141 splits the reflected light L3 of the laser light L1 from the surface to be measured into two parts, one light L4 to the position detecting means 142, and the other light L5 to the position detecting means 142. The light is incident on the angle detecting means 144. The position detecting means 142 includes, for example, a position sensitive detector (hereinafter, referred to as a PSD 142), receives the reflected light L4, and outputs a voltage A corresponding to the light receiving position of the reflected light L4.

The angle detecting means 144 is, for example, a PSD (hereinafter referred to as PSD 144) similar to the position detecting means 144.
), And receives the reflected light L5.
And outputs a voltage B corresponding to the light receiving position. The position determining unit 146 includes, for example, a CPU (hereinafter, referred to as a CPU 146).
By comparing the output voltage A of the PSD 142 with the voltage A-position characteristic of the standard sample stored in the voltage data storage unit 147, temporary position information of the surface to be measured is obtained.

The CPU 146 calculates the difference between the output voltage A of the PSD 142 and the output voltage B of the PSD 144 (A−B =
By comparing C) with the voltage difference C-angle characteristic of the standard sample stored in the voltage data storage unit 147,
Obtain angle information of the surface to be measured. Also, this CPU 146
Determines the position of the measured surface from the obtained angle information of the measured surface. That is, the CPU 146 compares the obtained angle information with the angle at the time of setting the optimum focus position, and when it is determined that there is no error, the temporary position information is used as true position information as it is.

On the other hand, when it is determined that the obtained angle information deviates from the angle at the time of the setting, the angle information and the output voltage A of the PSD 142 are used to determine the angle of the surface to be measured at the time of regular reflection. Estimate the position and use this as the true position.
In this case, the temporary position information is invalidated. Then, the control circuit 138 moves the sample holding plate 128 in the Z direction by the Z-axis motor 148 and the right-angle moving means such as the drive circuit 150 so that the position information determined by the CPU 146 becomes the optimum focus position. Let it.

Note that, as shown in FIG.
The light receiving positions of the PSDs 142 and 144 are P1 to P4 when the angle of the incident surface is the same even when the sample 116 mounted on the sample holding plate (not shown) is moved in the Z direction. It is arranged to move similarly to P3. Thereby, even if the sample 116 is moved in the Z direction,
If the angles of the incident surfaces are the same, these output voltages A, B
Changes in the same way, the voltage difference C is also constant,
If the angle of the incident surface changes, the voltage difference C also changes.

The particle size measuring apparatus 110 according to the first embodiment of the present invention is configured as described above, and its operation will be described below with reference to FIG. First, using a standard sample,
Comparison data such as the relationship between the output voltage A of one PSD 142 and the position and the relationship between the voltage difference C and the angle are obtained (step 100). That is, each time the standard sample having a uniform angle on the surface to be measured is moved in the Z direction by a predetermined distance, for example, 2 μm, the output voltage A of the PSD 142 is measured, and this is taken as the voltage A-position characteristic of the standard sample. The data is stored in the data storage unit 147.

Each time the standard sample whose angle of the surface to be measured is changed by a predetermined angle, for example, 2 °, the PSD1 is changed.
The voltage difference C is measured from the output voltage A of the P.42 and the output voltage B of the PSD 144, and is stored in the data storage unit 147 as a voltage difference C-angle characteristic of the standard sample. Next,
Position information and angle information of the surface to be measured when the optimum focus position is adjusted using the sample to be measured are set (step 10).
2). After the setting, the measurement of the Rayleigh scattered light measurement for measuring the particle size is started (step 104).

By the way, for example, when only one position detecting means, for example, PSD 142 is provided, the state of the sample is poor and the surface to be measured has undulation, the precision of the stage is poor, and the angle of the surface to be measured during the movement of the stage is reduced. May be shifted by θ from the angle at the time of setting. Then, since the traveling direction of the reflected light L3 changes as shown in FIG. 6, the light receiving position of the reflected light L4 by the PSD 142 changes from P4 to P5. Then, since the output voltage A also changes, an error may occur between the theoretical position and the actual position.

Therefore, in this embodiment, as described above, even if the angle of the surface to be measured deviates from the time when the optimum focus position is set, 2P
SDs 142 and 144 are arranged, and the position is determined in consideration of the angle information of the measured surface obtained from the output voltage difference C.

That is, as shown in FIG.
46 obtains temporary position information of the surface to be measured by comparing the output voltage A of the PSD 142 with the voltage A-position characteristic of the standard sample stored in the voltage data storage means 147 (step 106). Also, this CPU 146
By comparing the difference between the output voltage A of the PSD 142 and the output voltage B of the PSD 144, and the voltage difference C, with the voltage difference C-angle characteristic of the standard sample stored in the voltage data storage unit 147, Get angle information.

The CPU 146 determines the position of the measured surface from the obtained angle information of the measured surface. That is, the CPU 146 compares the obtained angle information with the angle at the time of setting the optimum focus position (step 108), and when it is determined that the obtained angle information is deviated from the predetermined angle, this angle information is determined. From the information and the output voltage A of the PSD 142, the position of the surface to be measured when specularly reflected is estimated, and this is set as the true position of the surface to be measured (step 110).

On the other hand, when it is determined that there is no error,
The temporary position information is used as true position information as it is (step 112). Then, the CPU 146 compares the obtained position information with the position information at the time of setting the optimum focus position (step 114). When it is determined that there is an error, the control circuit 138 returns to the position information determined by the CPU 146. But,
The sample holding plate 128 is moved in the Z direction by the right-angle moving means so as to be at the optimum focus position (step 116).

Thereafter, measurement of the next provisional position information and angle information on the surface to be measured is started (step 106). On the other hand, when it is determined that there is no error, measurement of the temporary position information and angle information of the next surface to be measured is started immediately (step 106). These processes are repeated during the measurement. In the present embodiment, the stage control is not limited to the stage movement in the XY directions. The stage is moved in the Z direction by a right-angle moving means such as a Z-axis motor, and the inclination of the surface to be measured is changed. Even in this case, by performing the processing of steps 206 to 216, the position of the surface to be measured can be easily adjusted to the optimum focus position at the time of setting again accurately as described above.

As described above, according to the particle size measuring apparatus 110 according to the first embodiment of the present invention, the position of the surface to be measured can be adjusted during the stage movement by the horizontal movement means or the stage movement by the right angle movement means. Is shifted from the optimal focus position,
Accurate positional information can be obtained even when the angle of the surface to be measured is constant as well as when it changes, so that the position of the surface to be measured can be easily adjusted again to the optimum focus position. it can. As a result, regardless of the state of the surface to be measured and the accuracy of the sample stage, the Rayleigh scattered light detection for measuring the particle diameter can be performed while always maintaining the optimum focus position, thereby improving the measurement accuracy result. it can.

Second Embodiment FIG. 7 shows a schematic configuration of a sample stage according to a second embodiment of the present invention, and FIG. 8 shows a schematic configuration of a sample stage according to the second embodiment of the present invention. , Respectively.
Parts corresponding to those in FIGS. 2 and 3 are denoted by reference numeral 100, and description thereof is omitted. In the present embodiment, FIG.
As shown in FIG.

The angle changing means comprises, for example, a stepping motor 252 and its driving circuit 254, and a sample holding plate 228 on which a sample 216 such as a silicon wafer is mounted.
Can be changed within a certain angle range. Then, the control circuit 238 first detects the two PSDs 242, 2
Based on the angle information obtained from the voltage difference C of FIG. 44 (see FIG. 8), the stepping motor 252 is set so that the angle information becomes a predetermined angle, for example, the angle of the surface to be measured when the optimum focus position is set. The sample holding plate 218 is inclined by an angle changing means such as the drive circuit 254.

After the angle adjustment, this control circuit 238
The sample holding plate 218 is moved in the Z direction by the right-angle moving means or the like so that the position information obtained in D242 becomes the position at the time of setting the optimum focus position. The particle size measuring device 210 according to the second embodiment of the present invention is configured as outlined above,
The operation will be described below with reference to FIG. First, using the standard sample, comparison data such as the relationship between the output voltage A and the position of one PSD 242 and the relationship between the voltage difference C and the angle is obtained (step 200).

That is, every time a standard sample having a uniform angle on the measurement surface is moved in the Z direction by a predetermined distance, for example, 2 μm, the output voltage A of the PSD 242 is measured, and this is measured as the voltage A-position of the standard sample. The data is stored in the data storage unit 247 as a characteristic. The voltage difference C is measured every time the standard sample whose angle of the surface to be measured is changed by a predetermined angle, for example, 2 °, is stored in the data storage unit 247 as a voltage difference C-angle characteristic of the standard sample. . Next,
Position information and angle information of the surface to be measured when the optimum focus position is adjusted using the sample to be measured are set (step 20).
2). After the setting, Rayleigh scattered light measurement for particle size measurement is performed (step 204).

Here, the CPU 246 compares the difference C between the output voltage A of the PSD 242 and the output voltage B of the PSD 244 with the voltage difference C-angle characteristic of the standard sample stored in the voltage data storage means 247. Then, angle information of the surface to be measured is obtained (step 206). And CPU2
46 compares the obtained angle information with the angle of the surface to be measured at the time of setting the optimum focus position (step 208), and when it is determined that the obtained angle information is shifted from the angle at the time of setting, The control circuit 238 controls the sample holding plate 2 by the angle changing means so that the obtained angle information becomes the angle at the time of setting.
18 is tilted (step 210).

After the angle adjustment, the CPU 246 sets the PSD 24
2 is compared with the voltage A-position characteristic of the standard sample stored in the voltage data storage means 247 to obtain position information on the surface to be measured (step 21).
2). Next, the CPU 246 sets the obtained position information and
The position information at the time of setting is compared (step 214), and when it is determined that there is no error, the next angle information of the surface to be measured is measured immediately (step 206).

On the other hand, when it is determined that there is an error,
The sample holding plate 218 is moved in the Z direction by the right-angle moving means so that the position information from the PSD 242 obtained after the angle adjustment becomes the position information at the time of setting. Thereafter, the next measurement of the angle information of the surface to be measured is performed (the step 20).
6). These processes are repeated during the measurement.

As described above, even if the angle of the surface to be measured is shifted from the setting during the stage movement, the angle of the surface to be measured is adjusted to the same angle as that at the time of setting, and then the PSD 14 is adjusted.
Since the position information is obtained from the position 2, the position information of the surface to be measured can be obtained accurately.

As described above, according to the particle size measuring apparatus 210 according to the second embodiment of the present invention, after adjusting the angle of the surface to be measured to the same angle as at the time of setting, the position information from the PSD 142 is obtained. Since the position information is obtained, the position information of the surface to be measured can be accurately obtained similarly to the particle diameter measuring device 110 according to the first embodiment of the present invention. Even in the case of displacement in the Z direction, it is easy to adjust the position of the surface to be measured to the optimum focus position again accurately. Accordingly, the Rayleigh scattered light measurement for measuring the particle diameter can be performed while always maintaining the optimum focus position regardless of the state of the surface to be measured and the accuracy of the sample stage, so that the measurement accuracy can be improved. .

In each configuration described above, an example was described in which the sample stage according to the present embodiment was used as a sample stage of a particle size measuring apparatus. However, the present invention is not limited to this. For example, a scanning electron microscope (SEM) And the like may be used for a sample stage of any device. In the present embodiment,
Although an example in which a silicon wafer is used as a sample has been described, the invention is not limited to this, and another material may be used. In the present embodiment, the position information is PS
Although the example obtained from the output voltage A of D142 has been described,
The output voltage B of the PSD 144 is not limited to this.
You may get more. That is, the temporary position information of the surface to be measured can be obtained from the output voltage of one of the two PSDs 142 and 144.

[0044]

As described above, according to the sample stage of the present invention, the position information is obtained by considering the angle of the surface to be measured by the angle detecting means and the position determining means. Even when the angle of the measured surface changes during the movement, it is easy to accurately obtain the position information of the measured surface. Thereby, even if the position of the measured surface is shifted from the optimal focus position during the stage movement,
It is easy to adjust the position of the surface to be measured again to the optimum focal position accurately. Further, according to the particle size measuring apparatus according to the present invention, since the sample stage according to the present invention is used as the sample stage, regardless of the state of the surface to be measured and the precision of the sample stage, the optimum focus position is always set. Since the Rayleigh scattered light measurement for measuring the particle size can be performed while maintaining the measurement, the measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a schematic configuration of a conventional particle size measuring device.

FIG. 2 is an explanatory diagram of a schematic configuration of a particle size measuring device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a schematic configuration of a sample stage according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of an arrangement of the PSD shown in FIG. 3;

FIG. 5 is a flowchart showing a processing procedure of position adjustment by the sample stage shown in FIG. 3;

6 is an explanatory diagram of the operation of the PSD shown in FIG.

FIG. 7 is an explanatory diagram of a schematic configuration of a particle size measuring device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of a schematic configuration of a sample stage according to a second embodiment of the present invention.

9 is a flowchart showing a processing procedure of position adjustment by the sample stage shown in FIG.

[Explanation of symbols]

 110 particle size measuring device 116 silicon wafer (sample) 118 sample stage 128 sample holding plate 130 X-axis motor (horizontal moving means) 132 Y-axis motor (horizontal moving means) 134, 136 drive circuit (horizontal moving means) 138 control circuit ( Stage control means) 142 PSD (Position detecting means) 144 PSD (Angle detecting means) 146 CPU (Position determining means) 148 Z-axis motor (Right angle moving means) 150 Drive circuit (Right angle moving means) L1 Convergent laser light L3 Regular reflection light (reflected light)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichiro Watanabe 2967 Ishikawacho, Hachioji-shi, Tokyo 5 Japan Spectroscopy Corporation

Claims (4)

[Claims] 1. A sample stage provided with a parallel moving means capable of moving a sample holding plate for holding a sample in a direction parallel to a surface to be measured of the sample, wherein the sample holding plate is moved in a direction perpendicular to the surface to be measured. Movable right-angle moving means, a position detecting means for receiving reflected light from the measured surface, and obtaining temporary position information of the measured surface from a light receiving position of the reflected light, and receiving the reflected light An angle detector for obtaining angle information of the surface to be measured from the light receiving position of the reflected light, and comparing the angle information obtained by the angle detector with predetermined angle information, when it is determined that there is no error, The position information obtained by the position detecting means is used as true position information as it is, and when it is determined that there is an error, the position information obtained by the position detecting means is calibrated based on the error to be true position information. Position determining means, and the position determining means Location information such that a predetermined position, the sample stage, characterized in that and a stage control means for moving the sample holding plate by the right-angle moving means. 2. A sample stage provided with a parallel moving means capable of moving a sample holding plate holding a sample in parallel with a surface to be measured of the sample, wherein the sample holding plate is moved in a direction perpendicular to the surface to be measured. A right-angle moving means, an angle changing means capable of changing an angle of the sample holding plate, and a device for receiving reflected light from the measured surface and obtaining angle information of the measured surface from a light receiving position of the reflected light. Angle detecting means, receiving the reflected light, from the light receiving position of the reflected light, position detecting means for obtaining the position information of the surface to be measured, the angle information obtained by the angle detecting means is a predetermined angle After tilting the sample holding plate by the angle changing means, the stage control for moving the sample holding plate by the right-angle moving means so that the position information obtained by the position detecting means becomes a predetermined position. Having means and A sample stage characterized by the following. 3. The sample stage according to claim 1, wherein the reflected light from the surface to be measured is split into two, one of which is incident on the position detecting means, and the other light is subjected to the angle detection. A sample stage provided with a beam splitter for allowing the beam to enter the means. 4. The sample stage according to claim 1, wherein the surface to be measured is irradiated with a converging laser beam to detect Rayleigh scattered light from the particle while scanning the surface, and the intensity of the particle is determined based on the scattered light intensity. A particle size measuring device comprising a particle size measuring means for measuring the particle size of the particles.