JP2511809B2 - Surface shape measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface profile measuring device which is capable of measuring the surface profile (that is, surface irregularities) of an object to be measured over a wide area with extremely high accuracy and at high speed by using an optical sensor. .

[0002]

2. Description of the Related Art Conventionally, as a non-contact method for measuring the surface shape (surface irregularities, that is, change in height) of an object to be measured, an optical sensor has been used in JP-A-51-124944. Then, a method of irradiating a light beam while moving it in the XY direction orthogonal to the surface of the object to be measured and measuring the position by the reflected light point image has been proposed.

Further, in this publication, an optical sensor for measuring the height of this unevenness is advanced and retracted in the height direction in accordance with the unevenness of the surface of the object to be measured so that the output of the optical sensor becomes zero. A technique for measuring the amount of advance / retreat and detecting it as the amount of unevenness has also been proposed.

Further, in Japanese Patent Laid-Open No. 50-98864, the sensor is raised in a direction in which the difference between the height signal from the surface of the object to be measured detected by the sensor and the sensor stored in advance approaches zero. A technique has also been proposed in which the sensor output is made to be a constant value by advancing and retreating in the vertical direction and the amount of advancing and retreating of this sensor is detected as the amount of irregularities on the surface of the object to be measured.

[0005]

However, in such a conventional method, the sensor is advanced and retracted in the height direction of the article surface so that the output of the sensor becomes zero or a constant value.
Although this amount of advance / retreat is used as the measurement value of the height of the article surface, even if the sensor is moved forward / backward according to the height of the object surface while moving the object under measurement on the XY table, continuous measurement is performed. When the movement of the object to be measured is fast or when the unevenness of the surface of the article changes suddenly, it is extremely difficult to control it so that it moves exactly back and forth by exactly matching the unevenness of the surface. The faster the movement of an object, the more difficult it was to accurately follow the movement of the sensor. For this reason, the control error of advancing and retracting the sensor is directly expressed as a measurement error, which is a serious defect when it is desired to perform measurement in an extremely minute order. Therefore, in order to reduce this control error, the moving speed of the object to be measured must be sufficiently slowed, or the movement of the object to be measured must be stopped for intermittent measurement instead of continuous measurement. It was difficult to perform high-speed continuous measurement and high-precision measurement on the order.

It is an object of the present invention to solve the above problems and to provide a surface profile measuring apparatus capable of high-speed continuous measurement of a minute order and highly accurate measurement.

[0007]

In order to solve the above-mentioned problems, the surface profile measuring apparatus of the present invention detects an X-direction moving table for moving an object to be measured in the X-direction and a moving amount of the X-direction moving table. An X-direction movement amount detector, a Y-direction movement table that moves an object to be measured in a Y direction orthogonal to the X direction, a Y-direction movement amount detector that detects a movement amount of the Y-direction movement table, By irradiating the light beam on the surface of the object to be measured and detecting the position of the reflected light spot,
An optical sensor that outputs a height signal of the surface of the object to be measured, and Z that moves the optical sensor in the Z direction perpendicular to the XY plane.
A direction movement table, a Z direction movement amount detector for detecting the movement amount of the Z direction movement table, a storage device for storing a height signal output value from the optical sensor at a certain time, and a storage device for storing the height signal output value. Compared this value and the height signal from the optical sensor, in the direction where the difference between the two approaches zero,
A Z-direction movement control device that outputs a control signal for moving the Z-direction movement table, and the optical sensor when the difference between the value stored in the storage device and the height signal from the optical sensor approaches zero. And an adder for outputting a value obtained by adding the movement amount from the Z-direction movement amount detector as a surface height measurement value.

[0008]

Thus, in the surface profile measuring apparatus of the present invention, while moving the object to be measured on the XY plane, the difference between the height signal of the optical sensor and the value stored in the storage device at a certain time point. The optical sensor is controlled to move in the Z direction so that
The optical sensor output and the Z-direction movement amount when the difference between the two approaches zero are added. Therefore, even if the follow-up movement of the optical sensor does not completely match the irregularities on the surface of the object to be measured, the mismatch is canceled by the addition of the Z-direction movement amount and the optical sensor output.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 5 show an embodiment of the present invention. In the figure, 1 is a flat plate-like base on which the object to be measured W is installed, and this base 1 can be moved on the X-direction moving table 2 in the horizontal direction (X-axis direction) by a pulse motor 3. The X-direction moving table 2 is movable on a Y-direction moving table 4 orthogonal to the X direction in the vertical direction (Y-axis direction) by a pulse motor 5.

These base 1, X-direction moving table 2,
Since the Y-direction moving table 4 is set vertically, the object to be measured W is vertically installed on the surface of the base 1.
The object to be measured is installed vertically because when it is placed horizontally like a thin plate, it is flexibly deformed by its own weight, and the surface shape may change delicately depending on the method of supporting it. In the case of the object to be measured which is not likely to be deformed, the base 1, the tables 2 and 4 may be horizontal.

An optical sensor 6 is installed in front of the base 1 so as to be movable on a Z-direction moving table 13 by a motor 14 in the Z-axis direction orthogonal to the XY plane. As shown in FIG. 2, the optical sensor 6 includes a light source 61 that emits a light beam having a good directivity, an irradiation lens 62 that narrows down this light beam and irradiates the surface of the object to be measured W, and an optical axis of the irradiation lens 62. An image forming lens 63 that forms an image of the reflected light spot on the light receiving surface 64a of the light receiving element 64 by forming an angle with the optical axis to narrow the reflected light flux from the light spot on the surface of the object to be measured W, and the reflected light. Points are in the Z direction on the surface of the object to be measured W (direction orthogonal to the XY plane).
Is arranged so that the light receiving surface 64a (see FIG. 4) coincides with the locus when it changes depending on the displacement of the two signals i ₁ , i corresponding to the position of the image of the reflected light spot on the light receiving surface 64a.
_From the two outputs i ₁ and i _{2 of} the light receiving element 64 which outputs ₂ and the light receiving element 64, the change Z ₁ of the height of the surface of the object to be measured W is Z ₁ = K · (i ₁ −i ₂ ) / ( i ₁ + i ₂ ) (where K is a constant).

As shown in FIG. 3, when the surface shape of the object W to be measured is displaced in the Z direction (direction orthogonal to the XY plane),
The light beam from the irradiation lens 62 is reflected on the surface, and the image Q of the reflected light spot imaged by the imaging lens 63 is displaced in the Z'direction corresponding to the displacement in the Z direction.

In order to detect the displacement of the image Q of the reflected light spot in the Z'direction, as described above, the light receiving surface 64a of the light receiving element 64 is in the Z'direction, that is, the locus of the image Q of the reflected light spot. Matched. As the light receiving element 64, for example, as shown in FIG. 4, a one-dimensional diffusion type PIN diode for converting the displacement in the Z ′ direction into an electric signal is used.

The optical sensor 6 shown in FIG. 3 shows an optical system of the type used when the object W to be measured is a scattering surface, and the object W to be measured is a mirror surface. For this, an optical sensor of the type in which the irradiation light flux and the reflected light flux are symmetrical with respect to the normal line of the surface of the object to be measured W is used because of the specular reflection.

The X-direction and Y-direction movement amounts X and Y by the X-direction movement table 2 and the Y-direction movement table 4 respectively receive the drive outputs of the X driver 8 and the Y driver 9 for driving the pulse motors 3 and 5, respectively. X direction movement amount detector 10,
It is detected by the Y-direction movement amount detector 11.

Optical sensor 6 by Z-direction moving table 13
The Z-direction movement amount Z of He- is not frequency-stabilized He-
This is performed by the Z-direction movement amount detector 15 which is an interferometric length measuring device using a Ne laser. The signal processor 12 is configured as shown in FIG.

In FIG. 5, reference numeral 124 is a storage device for storing the height signal output value from the optical sensor 6 at a certain time. 125 is the value stored in the storage device 124,
The Z-direction movement control device compares the height signal from the optical sensor 6 and outputs a control signal for moving the Z-direction movement table 13 to the Z driver 16 in a direction in which the difference between the two approaches zero.

Reference numeral 126 denotes a height signal from the optical sensor 6 and the Z-direction movement amount detector 1 when the difference between the value stored in the storage device 124 and the height signal from the optical sensor 6 approaches zero.
The addition device outputs a value obtained by adding the movement amount from 5 as a surface height measurement value. A control device 127 controls each of these operations.

Therefore, the object to be measured W is installed on the base 1, and the X-direction moving table 2 and the Y-direction moving table 4 move the base 1 in the XY plane, while the optical sensor 6 is used.
The light beam of the light source 61 is applied to the surface of the object W to be measured.
The signals i ₁ and i ₂ are output from the light receiving element 64, and the calculator 65 receives the signals i ₁ and i ₂ and receives the Z of the surface of the object to be measured W.
The height Z _{1 in the} direction is calculated.

When the height of the surface of the object to be measured W changes due to the movement of the object to be measured W in the XY directions, the height signal Z ₁ of the optical sensor 6 tries to change, but the storage device 124 is always present.
The height Z of the optical sensor 6 is controlled by the Z-direction movement control device 125 so that the difference between the output and the output (stored output value at a certain time point) approaches zero. As a result, the optical sensor 6 is moved by the Z table 13 in the direction following the unevenness of the surface (for this reason, the light receiving surface 64 of the light receiving element 64 in FIG.
The image Q of the reflected light spot is always brought close to the center line L _{0 of} a).

The height signal from the optical sensor 6 when approaching zero and the Z-direction movement amount from the Z-direction movement amount detector 15 are added by the adding device 126. If the tracking of the optical sensor 6 in the Z direction with respect to the unevenness of the object W to be measured is completely the same, the Z direction movement control amount of the optical sensor 6 itself is used as the measured value representing the height of the surface of the object W to be measured. However, in reality, is the movement speed in the XY direction extremely slow?
Alternatively, unless stopped, it is impossible to perfectly match the movement amount of the optical sensor 6 with the change in the unevenness of the surface of the object to be measured, and also when the unevenness of the surface of the object to be measured W changes suddenly, It is impossible to perfectly match the movement amount of the optical sensor 6 with the change in the unevenness of the surface of the object to be measured.

However, the height signal of the optical sensor 6 is deviated by an error in the Z direction following the unevenness, and the output of the Z direction movement amount detector 15 is opposite to the deviation of the optical sensor 6 by the same amount. Since they are deviated in the direction, the tracking error is canceled by the addition of both adding devices 126. As a result,
Even if the optical sensor 6 does not follow the unevenness of the surface of the object to be measured in the Z direction, the measurement can always be performed with extremely high accuracy.
In this way, since compensation is performed by addition, it is possible to perform highly accurate measurement while moving the XY table at high speed.

Moreover, the optical sensor 6 moves in the Z direction following the irregularities on the surface of the object to be measured W, and the difference from the output at a certain time stored in the storage device 124 of the optical sensor 6 becomes zero. Since the distance to the measured object W is large, the center line L of the PIN diode is always maintained even if the amount of change in the unevenness of the surface of the object to be measured W is large.
_{Since the} light image is controlled so as to be close to _0, it does not stick out of the measurement range, and high-precision measurement is always performed. When the object to be measured is fixed to the base 1, it may deviate from the vertically fixed position.

Therefore, the signal processor 12 stores the heights of the three points on the surface of the object W to be measured in the Z direction by the output of the optical sensor 6, and the three points have the same height in the Z direction. When the object W is virtually replaced as described above, if the height of the other arbitrary point in the Z direction is output, the shape can be obtained without depending on the fixing method of the object. You can
It is also possible to output the position of the contour line in the Z direction from the height in the Z direction.

[0025]

As described above, according to the present invention, while the optical sensor 6 is moved in the Z direction so as to follow the unevenness of the surface of the object to be measured, the output of the optical sensor 6 and a certain time point stored in the storage device. The optical sensor 6 so that the difference from the value at
To move out of the measurement range even if there is a large change in the unevenness, and to follow the output of the optical sensor 6 and the Z-direction movement amount when the difference between the two approaches zero. Since the surface height measurement value is a value obtained by canceling out the error, high-precision measurement is possible even if the follow-up of the optical sensor 6 does not completely match the unevenness of the surface of the object to be measured, and moreover, the Z direction. Since it can be measured before the following to the perfect match,
It enables extremely high speed continuous measurement.

[Brief description of drawings]

FIG. 1 is a perspective view showing a mechanical portion of a surface profile measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of a circuit unit in FIG.

FIG. 3 is a diagram showing the principle of measurement by an optical sensor.

FIG. 4 is an explanatory diagram showing an example of a light receiving element.

5 is a block diagram showing a specific configuration of the signal processor of FIG.

[Explanation of symbols]

 W DUT 1 Base 2 X-direction movement table 4 Y-direction movement table 6 Optical sensor 10 X-direction movement amount detector 11 Y-direction movement amount detector 12 Signal processor 13 Z-direction movement table 15 Z-direction movement amount detector 124 storage device

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-51-124944 (JP, A) JP-A-50-98864 (JP, A) JP-A-50-1766 (JP, A) JP-A-56- 125608 (JP, A) JP 50-103366 (JP, A) Actually developed 51-57667 (JP, U) JP-B 1-23041 (JP, B2) JP-B 7-26824 (JP, B2) Japanese Patent Publication Sho-57-52222 (JP, B2)

Claims (1)

(57) [Claims] 1. An X-direction movement table for moving an object to be measured in the X-direction, an X-direction movement amount detector for detecting an amount of movement of the X-direction movement table, and a Y-direction orthogonal to the X-direction. Y to move in the direction
Direction moving table, Y direction moving amount detector for detecting the moving amount of the Y direction moving table, and the object to be measured by irradiating the surface of the object to be measured with a light beam and detecting the position of its reflected light point. An optical sensor that outputs a surface height signal, a Z-direction moving table that moves the optical sensor in the Z direction perpendicular to the XY plane, and a Z-direction moving amount that detects a moving amount of the Z-direction moving table. A detector, a storage device that stores a height signal output value at a certain time from the optical sensor, and this value stored in the storage device, and a height signal from the optical sensor are compared, A Z-direction movement control device that outputs a control signal for moving the Z-direction movement table in a direction in which the difference between the two approaches zero, and the difference between the value stored in the storage device and the height signal from the optical sensor. Before when approaches zero A surface shape measuring device comprising: an addition device that outputs a value obtained by adding the height signal from the photo sensor and the movement amount from the Z direction movement amount detector as a surface height measurement value.