JP2003148951A - Method and instrument for measuring surface roughness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an instrument that eliminate dispersion of a measured value for surface roughness caused by measuring instruments. SOLUTION: This surface roughness measuring instrument is provided with a pair of fixed rails 1, 2 fixed to a base, laid rails 3, 4 laid between the fixed rails 1, 2, and a stage 5 supported on the laid rails 3, 4. The stage 5 is moved while selecting properly linear moving to a direction along the fixed rails 1, 2 accompanied to moving of the laid rails 3, 4 or rotational moving on the rails 3, 4, or combining the both, so as to measure the surface roughness of the a measuring object mounted on the stage 5. Measurement-required positions of the measuring object are moved to a measuring position measured by a surface roughness measuring sensor 6 respectively, without moving the stage 5 to a direction along the laid rails 3, 4 on the rails 4, 4.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface roughness measuring method and a measuring apparatus.

[0002]

2. Description of the Related Art For example, as shown in FIG. 1, a surface roughness measuring device (hereinafter also simply referred to as a measuring device) for measuring the surface roughness of an object to be measured such as a semiconductor substrate may be parallel to each other. A pair of Y-axis rails 1 and 2 fixed directly on the base 7, and a pair of Xs installed between the pair of Y-axis rails 1 and 2 so as to be orthogonal to the pair of Y-axis rails 1 and 2.
Axial rails 3, 4, a stage 5 supported on the X-axis rails 3, 4, and a surface roughness measuring sensor 6 (hereinafter, simply referred to as a measuring sensor) for measuring the surface roughness of a measurement object on the stage 5. (Also referred to as) (specifically, for example, HRP (High Resolution Profiler; KLA Ten
trade name of cor company)).

In such a surface roughness measuring device, the stage 5 is moved in plane so that the measurement-required portion of the measurement object on the stage 5 is located below the measurement sensor 6, and the surface of the measurement-required portion is moved. Measure the roughness. At this time, stage 5
In order to move the upper measurement object in the Y-axis direction (the arrow A direction and the arrow B direction in FIG. 1), the X-axis rails 3 and 4 installed on the Y-axis rail are attached to the Y-axis rails 1 and 2. The stage 5 supported by the X-axis rails 3 and 4 is moved along with the movement along the direction. On the other hand, in order to move the measurement object on the stage 5 in the X-axis direction (direction of arrow C and arrow D in FIG. 1), the stage 5 is moved in the direction along the X-axis rails 3, 4.

[0004]

However, when the surface roughness is measured by using the above measuring device, there is a problem that the measured value becomes larger than the actual surface roughness as the distance from the center of the stage 5 increases. However, this problem does not occur in the measurement value when the stage 5 is moved along the Y-axis rails 1 and 2 for measurement, and the X-axis rails 3,
It occurs only when moved along 4 and measured. Therefore, it is considered that such variations are caused by the measuring device, not by the actual surface state of the measuring object.

The present invention has been made to solve the above problems, and provides a surface roughness measuring method and a measuring device for eliminating the variation in the measured value of the surface roughness due to the measuring device. The purpose is to do.

[0006]

A surface roughness measuring method according to the present invention comprises a pair of fixed rails fixed to a base so as to be substantially parallel to each other, and a guide rail installed between the fixed rails. An erection rail that can be moved linearly,
A stage supported on the erection rail, capable of rotating movement and linear movement guided by the erection rail, and a surface roughness measurement for measuring the surface roughness of a measurement target placed on the stage. A surface roughness measuring method using a measuring device including a sensor, wherein the stage is rotationally moved on the erection rail, and linearly moved along with the erection rail being guided by the fixed rail. Are moved or appropriately selected or combined to move the measurement-required portion of the measurement object to a position where the surface roughness measuring sensor can measure.

Further, according to the surface roughness measuring method of the present invention, an object to be measured is placed on a stage supported on a fixed rail fixed to a base, and the stage is rotated and moved along the fixed rail. It is characterized in that the measurement-required portions of the measurement object are respectively moved to the measurable positions by the surface roughness measuring sensor by moving them by appropriately selecting or combining with linear movement.

Further, the surface roughness measuring device of the present invention comprises a fixed rail fixed to a base, a fixed rail supported on the fixed rail without interposing other rails, a rotational movement and a guide to the fixed rail. It is characterized by comprising a stage capable of linear movement and a surface roughness measuring sensor for measuring the surface roughness of a measuring object placed on the stage.

In the surface roughness measuring method of the present invention, a pair of fixed rails fixed to the base so as to be substantially parallel to each other and a fixed rail are installed between the fixed rails and linearly moved by being guided by the fixed rails. A possible installation rail, a stage supported on the installation rail, capable of rotational movement and linear movement guided by the installation rail, and a surface roughness of a measurement target placed on the stage. A surface roughness measuring method using a measuring device provided with a surface roughness measuring sensor for measuring, wherein a measured value when the surface roughness of a measuring object is measured by moving the stage in a direction along the erection rail. Is characterized in that a correction based on an analysis result obtained by previously analyzing the distribution tendency of is applied to a newly measured measurement value.

Further, the surface roughness measuring device of the present invention comprises a pair of fixed rails fixed to the base so as to be substantially parallel to each other, and installed between the fixed rails and guided by the fixed rails to move linearly. A possible installation rail, a stage supported on the installation rail, capable of rotational movement and linear movement guided by the installation rail, and a surface roughness of a measurement target placed on the stage. A surface roughness measuring sensor to be measured, and a correction based on an analysis result obtained by pre-analyzing a distribution tendency of measured values when the surface roughness of the measurement target is measured by moving the stage in the direction along the erection rail, It is characterized in that it further comprises a correction means for newly measuring the measured value.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, the structure of the surface roughness measuring apparatus 50 for carrying out the surface roughness measuring method according to the present invention will be described.

As shown in FIG. 1, the surface roughness measuring apparatus 50 of the present embodiment has a pair of Ys directly fixed on the base 7.
Axial rails (fixed rails) 1 and a pair of X-axis rails (erection rails) 3, which are erected between the pair of Y-axis rails 1 and 2 so as to be orthogonal to the pair of Y-axis rails 1 and 2. 4 and
A stage 5 supported on the X-axis rails 3, 4; a surface roughness measuring sensor 6 for measuring the surface roughness of an object to be measured on the stage 5; and an optical flat as a reference for leveling the stage 5. 12 and 12, and is generally configured.

Of these, the Y-axis rails 1 and 2 are fixed on the base 7 substantially in the longitudinal direction so as to be parallel to each other.

On the other hand, the X-axis rails 3 and 4 are always kept parallel to each other and at a constant distance because one ends of the X-axis rails 3 and 4 are connected by the connecting members 8 and 9, respectively.
It is installed between the Y-axis rails 1 and 2 via these connecting members 8 and 9. These connecting members 8 and 9 are guided by the Y-axis rails 1 and 2 and are movable in the Y-axis direction (the arrow A direction and the arrow B direction in FIG. 1). Then, the X-axis rails 3 and 4 are driven (via the connecting members 8 and 9) by the Y-axis motor 10 provided on the base 7 (for example, the side of the Y-axis rail 2), for example. Guided by 2, Y
Move in the axial direction.

The stage 5 is supported on the X-axis rails 3 and 4 via its base portion 5a, and is rotated horizontally (in both directions) with respect to the base portion 5a by the driving of a rotary drive device (not shown). To do. To move the stage 5 in the Y-axis direction, the X-axis rails 3, 4 supporting the stage 5 are used.
Should be moved in the Y-axis direction along the Y-axis rails 1 and 2. Further, the stage 5 is driven by an X-axis motor 11 provided on the connecting member 9, for example, so that the X-axis rails 3,
It moves in the X-axis direction (arrow C direction and arrow D direction in FIG. 1) guided by 4.

The surface roughness measuring sensor 6 is fixed to a pedestal 6a fixed to a base 7. This stand 6a
Is, for example, substantially L-shaped, and is arranged such that one side thereof is in the vertical direction and the other side is above and horizontal to the one side. The surface roughness measuring sensor 6 is fixed to the top end of the pedestal 6a.
The surface roughness measuring sensor 6 is composed of, for example, a stylus that comes into contact with the upper surface of the measurement target placed on the stage 5, a capacitor, and an electromagnet. Then, the surface roughness of the measurement object is detected using the principle of the parallel plate capacitor.
That is, C = ε ₀ S / d, where C is the capacitance of the capacitor, S is the area, d is the distance between the capacitor and the measurement object, and ε ₀ is the vacuum dielectric constant. That is, d = ε ₀ S /
It can be expressed as C. By substituting the vacuum permittivity ε ₀ and the area S of the capacitor (both are constant) and the detected value C of the capacitance into this equation, the distance d between the capacitor and the measurement object at each measurement point can be obtained. You can Further, the surface roughness can be calculated based on the amount of variation of the obtained distance d within the surface of the measurement object or the amount of deviation from the reference value.

The optical flat 12 is a flat plate made of glass and is provided below the stage 5 so as to be substantially parallel to the stage 5. On the other hand, a sensor (not shown) that detects the upper surface of the optical flat 12 is provided on the lower surface of the stage 5, and the tilt of the stage 5 is adjusted so as to be parallel to the upper surface of the optical flat 12 based on the detection value of the sensor. It is designed to perform correction control. Alternatively, the measurement data is corrected (correction for eliminating the fluctuation of the measurement value due to the fluctuation of the inclination of the stage 5) based on the detection value of the sensor. Therefore, in any case, it is possible to eliminate the fluctuation of the measurement value due to the fluctuation of the inclination of the stage 5.

The present inventor has determined that the measured value of the surface roughness along the X-axis direction when measured by the conventional method is the stage 5
As a result of studying the cause that the distance increases from the center of the upper measurement object, the X-axis rails 3, 4 move as the stage 5 moves on the X-axis rails 3, 4, as shown in FIG. It was thought that the cause was that the amount of deflection of the was changed. That is, when the stage 5 is located at the central portion in the longitudinal direction of the X-axis rails 3 and 4 (FIG. 3A), the amount of bending of the X-axis rails 3 and 4 is maximum, and the stage 5 has both ends (see FIG. 3 (b) or FIG.
It was considered that the amount of flexure gradually decreased as it moved to (c)). In FIG. 3, the change amount of the lower end line L of the X-axis rails 3 and 4 (that is, the change amount of the bending amount) is exaggerated for easy understanding. Then, as described below, as a result of measuring the surface roughness by the surface roughness measuring method according to the present invention, it was found that there is no variation in the measured values due to the measuring device.

Next, the surface roughness measuring method according to the present invention will be described.

In this surface roughness measuring method, the stage 5
By appropriately selecting or combining the rotational movement on the X-axis rails 3 and 4 and the linear movement in the direction along the Y-axis rails 1 and 2 via the X-axis rails 3 and 4, The measurement-required portions of the measurement object are moved to positions where the surface roughness measuring sensor 6 can measure them. That is,
The stage 5 is moved so as to satisfy the following conditions.
That is, the stage 5 is rotationally moved so that the measurement-required portion of the measurement target reaches a straight line that is parallel to the Y-axis direction and that passes through the measurable position by the surface roughness measurement sensor 6, while measuring the surface roughness. The stage 5 is linearly moved so that the measurement-required portion of the measurement object reaches the position where the sensor 6 can measure the object. As a result of moving the stage 5 in this way, the surface roughness is measured when the measurement-required portion of the measurement object is located at the position where the surface roughness measurement sensor 6 can measure. By repeating the movement of the stage 5 and the measurement by the surface roughness measuring sensor 6 at each measurement-required location, the in-plane surface roughness of the measurement object can be measured. Therefore, the stage 5 is attached to the X-axis rails 3, 4
It is not necessary to move it in the direction along the X-axis rails 3 and 4 above. In addition, the rotation angle required for the movement of the measurement data (the rotation angle of the stage 5 with respect to the reference rotation phase)
Then, by converting the coordinate value on the XY plane according to the linear movement distance (movement distance of the stage 5 with respect to the reference Y-axis direction position), the data can be easily handled.

Example FIG. 2 shows the result of measuring the surface roughness of a mirror-polished silicon wafer (measurement object) having a diameter of 200 mm by applying the surface roughness measuring method of the above embodiment (RMS (Root Mean Square Deviation of the Surf
ace; root mean square roughness) (unit: nm)) was plotted. As a measuring device, KLA Tencor HRP-3
20 (having a stylus with a radius of curvature of the tip shape of 2 μm) was used, and the measurement range by the surface roughness measuring sensor 6 was 250 μm × 250 μm. The measurement point has, for example, the center of the mirror-polished silicon wafer as the origin, and the coordinates (X (mm), Y (mm)) on the XY plane including the wafer surface =
(-90,0) (P1 in FIG. 2), (X, Y) = (-5
0,0) (P2 in FIG. 2), (X, Y) = (0,0) (P3 in FIG. 2), (X, Y) = (50,0) (P in FIG. 2)
4), (X, Y) = (90,0) (P5 in FIG. 2),
(X, Y) = (0, −90) (P6 in FIG. 2), (X,
Y) = (0, −50) (P7 in FIG. 2), (X, Y) =
(0,50) (P8 in FIG. 2), (X, Y) = (0,9)
0) (P9 in FIG. 2) for the convenience of 9 points. In the case of FIG. 2A, among the measurement points, P1 and P2 were measured after rotating the stage 5 counterclockwise by 270 degrees and linearly moving in the Y-axis direction. Regarding P6 and P7,
Measurement was performed after rotating the stage 5 counterclockwise 180 degrees and linearly moving in the Y-axis direction. For P4 and P5, rotate the stage 5 90 degrees counterclockwise and
It was measured after linearly moving in the axial direction. Also, P3, P
For 8 and P9, the stage 5 was only linearly moved in the Y-axis direction and then measured. As a result, as shown in FIG. 2 (a), there was almost no variation in the measured values at each measuring point. Further, in the case of FIG. 2B, among the measurement points, P1,
For P2, the stage 5 was rotated clockwise by 90 degrees and linearly moved in the Y-axis direction, and then measured. Also, P
For 6 and P7, the stage 5 was rotated clockwise by 180 degrees and linearly moved in the Y-axis direction, and then measured. For P4 and P5, move stage 5 clockwise
The measurement was performed after rotating 70 degrees and linearly moving in the Y-axis direction. Further, P3, P8, and P9 were measured after the stage 5 was only linearly moved in the Y-axis direction. Also in this case, similarly, as shown in FIG. 2B, there was almost no variation in measured values at each measurement point.

<Comparative Example> Next, a comparative example will be described. Figure 4
Conventional surface roughness measuring method (P1, P2, P3, P4, P
5 moves the stage 5 along the X-axis rails 3 and 4 for measurement, and P6, P7, (P3), P8, and P9 measure the stage 5 by moving the stage 5 in the Y-axis direction. FIG. 5 is a plot of the results of measuring the surface roughness of a mirror-polished silicon wafer (Ra (Roughness Average; centerline average roughness) in addition to the above RMS), and FIG. 5 is a diagram showing specific numerical values thereof. . It should be noted that RMS and Ra show similar tendencies only with a slight difference in their absolute values. As is clear from FIGS. 4 and 5,
Only with respect to the measured values when the stage 5 is moved along the X-axis rails 3 and 4, there is a variation that tends to increase as the distance from the center increases. Specifically, when the stage is moved along the X-axis rail, the RMS greatly fluctuates from about 0.36 nm to about 0.72 nm as shown in FIG. However, when moving along the Y-axis rail, there is almost no change from about 0.33 nm to about 0.36 nm.

From the comparison between the embodiment and the comparative example,
When the surface roughness is measured by moving the stage 5 along the X-axis rails 3 and 4, variations in the amount of bending of the X-axis rails 3 and 4 in response to changes in the position of the stage 5 cause variations in the measured values. Is apparently occurring. That is, since a material having high rigidity, such as stainless steel, is used for the portion of the stage 5 to which the load is applied, such as the X-axis rails 3 and 4, the amount of bending due to the load is originally extremely small. It can be seen that this is a problem in the case of a measurement in which even a minute measurement error such as Angstrom order cannot be ignored. On the other hand, since the Y-axis rails 1 and 2 are directly fixed on the base 7, they do not bend, and therefore the stage 5 is moved along the Y-axis rails 1 and 2 to reduce the surface roughness. When measured, it is considered that there is no variation in measured values due to the measuring device.

As described above, according to the surface roughness measuring method of this embodiment, the stage 5 is rotationally moved on the X-axis rails 3 and 4, and the Y-axis is moved via the X-axis rails 3 and 4. By appropriately selecting or combining and moving linearly in the direction along the rails 1 and 2, the measurement required points of the measuring object are moved to the measurable positions by the surface roughness measuring sensor 6, respectively, and each measurement is performed. Since the surface roughness of the required portion is measured, it is not necessary to move the stage 5 on the X-axis rails 3 and 4 in the direction along the X-axis rails 3 and 4. Therefore, the measurement data does not vary due to the variation in the bending amount of the X-axis rails 3 and 4.

In the above embodiment, the semiconductor substrate (for example, a mirror-polished silicon wafer) is used for measurement, but it may be used for other purposes as long as the surface roughness needs to be measured. Further, in the above embodiment,
Although the example of performing the measurement without moving the stage 5 along the X-axis rails 3 and 4 has been described, the present invention is not limited to this, and for example, the stage 5 may be moved in the direction along the X-axis rails 3 and 4. The newly measured measurement value may be corrected based on the analysis result obtained by previously analyzing the distribution tendency of the measurement value when the surface roughness of the measurement target is measured. That is, when the surface roughness is measured by moving the stage 5 in the direction along the X-axis rails 3 and 4, the measurement point is the stage 5
By analyzing how the measured value increases as it moves away from the center of the, the error in the measured value at each measuring point due to the change in the amount of bending of the X-axis rails 3 and 4 (hereinafter,
(Also referred to as device-induced error) is calculated, and the calculated device-induced error is subtracted from the actual measurement value at each measurement point to obtain a proper measurement value without device-induced error. be able to. Further, the surface roughness measuring device 50 may be provided with a function of automatically performing such a correction (that is, the measuring device 50 may include the correction means according to the present invention). In addition, the surface roughness measuring device 50 of the above-described embodiment is provided with the Y-axis rails 1 and 2.
Although the configuration including both the X-axis rails 3 and 4 has been exemplified,
The present invention is not limited to this. For example, the stage 5 does not have the X-axis rails 3 and 4, and the stage 5 is supported on the Y-axis rails 1 and 2 and rotationally moves on the Y-axis rails 1 and 2. Rail 1,
It is also possible to use a surface roughness measuring device configured to be capable of linear movement guided by 2. That is, the object to be measured is placed on the stage 5 in this case, and the object to be measured is moved by appropriately selecting or combining the stage 5 with rotational movement and linear movement along the Y-axis rails 1 and 2. The surface roughness may be measured by moving each of the measurement-requiring points to the position where the surface roughness measuring sensor 6 can measure. Alternatively, simply by increasing the rigidity of the X-axis rails 3 and 4, the bending amount of the X-axis rails 3 and 4 does not change regardless of the position of the stage 5 that is guided and moved by the X-axis rails 3 and 4. You may do it.

[0027]

According to the surface roughness measuring method and the measuring apparatus of the present invention, it is possible to eliminate the variation in the measured values due to the measuring apparatus and perform the proper measurement.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface roughness measuring device, in which (a) is a plan view and (b) is a front view.

FIG. 2 is a diagram showing a tendency of in-plane distribution of measured values when the surface roughness of a semiconductor substrate is measured by the surface roughness measuring method of the present invention.

FIG. 3 is a schematic diagram showing a change in a bending amount of an erection rail according to a moving position of a stage.

FIG. 4 is a diagram showing a tendency of in-plane distribution of measured values when the surface roughness of a semiconductor substrate is measured by a conventional surface roughness measuring method.

FIG. 5 is a diagram showing measured values when the surface roughness of a semiconductor substrate is measured by a conventional surface roughness measuring method.

[Explanation of symbols]

1, 2 Y-axis rail (fixed rail) 3,4 X-axis rail (construction rail) 5 stages 6 Surface roughness measurement sensor

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Claims (5)

[Claims] 1. A pair of fixed rails, which are fixed to a base so as to be substantially parallel to each other, an erection rail that is installed between the fixed rails and is linearly movable by being guided by the fixed rail, and on the erection rail. A stage that is supported by and is capable of rotating movement and linear movement guided by the erection rail;
A surface roughness measuring method using a measuring device equipped with a surface roughness measuring sensor for measuring the surface roughness of a measuring object placed on the stage, comprising rotating the stage on the erection rail. By appropriately selecting or combining the movement and the linear movement accompanying the movement of the erection rail guided by the fixed rail, the measurement target points of the measurement target are respectively measured by the surface roughness measuring sensor. A method for measuring surface roughness, which comprises moving to a feasible position. 2. An object to be measured is placed on a stage supported on a fixed rail fixed to a base, and the stage is moved by appropriately selecting or combining rotational movement and linear movement along the fixed rail. The surface roughness measuring method is characterized in that the measurement-required portion of the measurement object is moved to a measurable position by the surface roughness measuring sensor. 3. A fixed rail fixed to a base, a stage supported on the fixed rail without interposing other rails, and capable of rotational movement and linear movement guided by the fixed rail, A surface roughness measuring device, comprising: a surface roughness measuring sensor for measuring the surface roughness of a measuring object placed on a stage. 4. A pair of fixed rails fixed to a base so as to be substantially parallel to each other, an erection rail that is erected between the fixed rails and is linearly movable by being guided by the fixed rails, and on the erection rail. A stage that is supported by and is capable of rotating movement and linear movement guided by the erection rail;
A surface roughness measuring method using a measuring device equipped with a surface roughness measuring sensor for measuring the surface roughness of a measuring object placed on the stage, wherein the stage is moved in a direction along the erection rail. A method for measuring surface roughness, characterized in that a newly measured measurement value is subjected to correction based on an analysis result obtained by previously analyzing a distribution tendency of measurement values when the surface roughness of a measurement target is measured. 5. A pair of fixed rails, which are fixed to a base so as to be substantially parallel to each other, an erection rail that is erected between the fixed rails and is linearly movable by being guided by the fixed rail, and on the erection rail. A stage that is supported by and is capable of rotating movement and linear movement guided by the erection rail;
A surface roughness measuring sensor for measuring the surface roughness of the measuring object placed on the stage, and a case of measuring the surface roughness of the measuring object by moving the stage in the direction along the erection rail. A surface roughness measuring device comprising: a correction unit that applies a correction based on an analysis result of a distribution of measured values in advance to a newly measured measured value.