JPH0726824B2 - Surface shape measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field of the Present Invention> The present invention uses an optical sensor to measure the surface shape (that is, surface irregularities) of an object to be measured over a large area with extremely high accuracy and at high speed. The present invention relates to a surface shape measuring device capable of measuring.

<Prior Art> Conventionally, as a method for non-contact measurement of the surface shape (concavity and convexity of the surface, that is, change in height) of an object to be measured, there has been disclosed
Japanese Patent Laid-Open No. 51-124944 proposes a method of irradiating a light flux beam while moving it in an XY direction orthogonal to the surface of an object to be measured using an optical sensor, and measuring the position of the emitted light point image. ing.

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

Further, in JP-A-50-98864, the sensor is moved in the height direction 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 constant value stored in advance approaches zero. A technique has also been proposed in which the output of the sensor is advanced and retracted to a constant value, and the amount of advance / retreat of the sensor is detected as the amount of unevenness on the surface of the object to be measured.

<Problems to be Solved by the Present Invention> 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, and this advance / retreat amount is adjusted. Although the measured value of the height of the article surface is used, even if the sensor is moved forward and backward according to the height of the surface of the object to be measured while moving the object to be measured on the XY table, the movement of the object to be measured is moved. When the speed is high 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, and the movement of the measured object It was impossible to keep up with the progress of the sensor as the speed increased. 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.

Further, in a minute order, it is impossible to perform highly accurate measurement due to the straightness error in the movement on the XY table.

The present invention solves such a problem, and provides a surface profile measuring apparatus that enables high-speed continuous measurement of a minute order and highly accurate measurement even if there is a straightness error in the XY plane. It is an object.

<Means for Solving the Problems> In order to solve the problems, in the surface profile measuring apparatus of the present invention, an X-direction moving table that moves an object to be measured in the X direction, and a movement amount of the X-direction moving table. X-direction movement amount detector for detecting X, and X for moving the DUT in the Y-direction orthogonal to the X-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. When the detector and the object to be measured are optical flat,
A movement table displacement amount setting device in which a height signal output from the optical sensor is stored in advance in association with a movement amount output from the X direction movement amount detector and the Y direction movement amount detector; A storage device that stores the height signal output value from the optical sensor at a certain point of time, this value stored in the storage device, and the height signal from the optical sensor are compared, and the difference between the two is zero. And a Z-direction movement control device that outputs a control signal for moving the Z-direction movement table in a direction approaching to, the difference between the value stored in the storage device and the height signal from the optical sensor approaches zero. When the height signal from the optical sensor and the movement amount from the Z-direction movement amount detector at the time are added, a deviation amount set in the movement table deviation amount setting device from the addition result of the addition device Is the amount of movement in the X direction And a subtraction device that outputs a value obtained by subtracting the movement amount output from the detector and the Y-direction movement amount detector as a surface height measurement value.

<Operation> Therefore, in the surface profile measuring apparatus of the present invention, the difference between the height signal of the optical sensor and the constant value of the storage device approaches zero while moving the object to be measured on the XY plane. The optical sensor is controlled to move in the Z direction, and the Z direction movement amount and the optical sensor output are added. Therefore, even if the follow-up movement of the optical sensor does not completely match the unevenness of 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, and the movement of the X- and Y-direction moving table is canceled. Due to Z
The displacement in the direction is measured and stored in advance with the optical flat as a reference, and the stored value is subtracted from the added value as a correction amount.

<Embodiment of the present invention> 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-shaped base on which the object to be measured w is mounted, 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 in the vertical direction (Y-axis direction) by a pulse motor 5 on a Y-direction moving table 4 which is orthogonal to the X direction.

Since the base 1, the X-direction moving table 2, and the Y-direction moving table 4 are 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.

In front of the base 1, the optical sensor 6 has a Z-direction moving table 13
The motor 14 is installed so as to be movable 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 good directivity, an irradiation lens 62 that narrows this light beam and irradiates the surface of the object to be measured W, and an optical axis of the 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 and focusing the reflected light flux from the light spot on the surface of the object w to be measured; The light receiving surface 64a (see FIG. 4) is arranged so that the light receiving surface 64a (see FIG. 4) coincides with the locus when the point changes due to the displacement of the surface of the object to be measured W in two directions (directions orthogonal to the XY plane). Two signals i depending on the position of the image of the reflected light spot at
_The light receiving element 64 that outputs ₁ , i ₂ and the two changes i ₁ and i _{2 of} the light receiving element 64 are used to change the height Z ₁ of the surface of the object to be measured W. And a computing unit 65 that computes as.

As shown in FIG. 3, when the surface shape of the object to be measured W is displaced in the Z direction (direction orthogonal to the XY plane), the light flux from the irradiation lens 62 is reflected on the surface and is formed by the imaging lens 63. The image Q of the reflected light spot to be imaged 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, the light receiving surface 64a of the light receiving element 64 is made to coincide with the axis trace of the image Q of the reflected light spot in the Z'direction, as described above. There is.

As the light receiving element 64, for example, as shown in FIG.
A one-dimensional diffused PIN diode is used that converts directional displacement into an electrical signal.

The optical sensor 6 shown in FIG. 3 shows an optical system of a type used for measurement when the object to be measured W is a scattering surface, and when the object to be measured W is a mirror surface. Since the light is reflected specularly, 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.

X by moving table 2 in X direction and moving table 4 in Y direction
The movement amounts X and Y in the Y and Y directions are the X direction movement amount detector 10 and the Y direction movement amount detector 11 that receive the drive outputs of the X driver 8 and the Y driver 9 that drive the pulse motors 3 and 5, respectively. Detected by.

The Z-direction movement amount Z of the optical sensor 6 by the Z-direction movement table 13 is performed by the Z-direction movement amount detector 15 which is an interferometer and uses an He-Ne laser whose frequency is not stabilized.

The signal processor 12 is constructed 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 and the optical sensor 6
The Z-direction movement control device outputs a control signal for moving the Z-direction movement table 13 to the Z driver 16 in the direction in which the difference between the height signal from the Z direction is close to zero.

Reference numeral 126 denotes a height signal from the optical sensor 6 and a movement amount from the Z-direction movement detector 15 when the difference between the value stored in the storage device 124 and the height signal from the optical sensor 6 approaches zero. It is an adding device for adding and.

Reference numeral 128 denotes a height signal output from the optical sensor in association with the movement amount output from the X-direction movement amount detector and the Y-direction movement amount detector when the measured object is an optical flat. It is a moving table deviation amount setting device stored and set in advance.

129 subtracts the displacement amount set in the displacement table displacement amount setting device from the addition result of the addition device in association with the displacement amount output from the X direction displacement amount detector and the Y direction displacement amount detector. This is a subtraction device that outputs the calculated value 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 are used to fix the base 1
While moving on the XY plane, the light beam of the light source 61 of the optical sensor 6 is applied to the surface of the object to be measured W.

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 height Z ₁ of the surface of the object to be measured W in the Z 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 X-Y directions, the optical sensor 6 and the height signal Z ₁ try to change, but the output of the storage device 124 is always constant (constant). value)
The height Z of the optical sensor 6 is controlled by the Z-direction movement control device 125 so as to be equal to. 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 made to be close to the center line l _{0 of} a).

At this time, the Z-direction movement amount from the Z-direction movement amount detector 15 and the height from the optical sensor 6 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 to be measured W is completely the same, the Z direction movement control amount of the optical sensor 6 itself is taken as the measured value representing the height of the surface of the object to be measured W. However, in reality, unless the moving speed in the X-Y directions is extremely slow or it is not stopped, it is impossible to perfectly match the moving amount of the optical sensor 6 with the change in the unevenness of the surface of the object to be measured. Even if the irregularities on the surface of the object to be measured W change rapidly, it is impossible to perfectly match the movement amount of the optical sensor 6 with the irregularities on the surface of the object to be measured.

Therefore, the height signal of the optical sensor 6 is deviated by the error due to the unevenness, and the output of the Z-direction movement amount detector 15 is deviated by the same amount in the direction opposite to the deviation of the optical sensor 6. Therefore, the follow-up error is canceled by the addition by the adding device 126 of both. As a result, even if the unevenness of the surface of the object to be measured in the Z direction of the optical sensor 6 is imperfect, the measurement can always be performed with extremely high accuracy, and since the compensation is made by addition in this way, the XY table is moved at high speed. While it is possible to measure.

Moreover, the optical sensor 6 moves in the Z direction following the unevenness of the surface of the object to be measured W so that the difference between the output of the optical sensor 6 and the output at a certain time stored in the storage device 124 approaches zero. Therefore, even if the amount of change in the unevenness of the surface of the object to be measured W is large, the light image is controlled so as to always come close to the center l _{0 of the} PIN diode. Highly accurate measurements are always made.

In this measurement, the X, Y table 2 shown in FIG.
The displacement of the height in the Z direction becomes a problem due to the movement itself of 4 in the X and Y directions. Therefore, when the object to be measured is an optical flat, it is output from the optical sensor 6 in association with the movement amounts X and Y output from the X-direction movement amount detector 10 and the Y-direction movement amount detector 11. The height signal Z ₁ to be stored is previously stored in the moving table displacement amount setting device 128.

That is, the output of the optical sensor 6 when the optical flat is measured indicates the amount of deviation in the Z direction for each movement position in the X and Y table movement. This displacement amount is preset in the moving table displacement amount setting device 128 for the entire XY plane.

Then, the shift amount set in the movement table shift amount setting device 12 is associated with the X-direction movement amount and the Y-direction movement amount, and subtracted by the subtraction device 129 from the addition result of the addition device 126. As a result, even if the X-Y direction moving table deviates from the ideal movement in the X-Y plane, a measurement error does not occur, and as a result, the straightness error of the X and Y direction moving tables is canceled and the ultra-high movement is achieved. High-precision shape measurement can be performed as well as using a precision moving table.

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 uses three Z points on the surface of the object to be measured W.
The height in the direction is memorized by the output of the optical sensor 6, and the object W to be measured is virtually replaced so that the heights in the Z direction of these three points have the same value. If the height is output in the Z direction, the shape can be obtained without depending on how the object to be measured is fixed.

It is also possible to output the position of the contour line in the Z direction from the height in the Z direction.

<Effects of the Present Invention> As described above, according to the present invention, since the deviation in the Z direction due to the movement of the XY table is preset and subtracted from the measurement result, the influence of the XY plane movement error is eliminated. Therefore, extremely high precision measurement is possible.

[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 portion thereof, and FIG.
FIG. 4 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, and FIG. 5 is a block diagram showing a concrete configuration of the signal processor of FIG. W ... DUT, 1 ... Base, 2 ... X-direction moving table, 4 ... Y-direction moving table, 6 ... Optical sensor, 10 ...
… X direction movement amount detector, 11 …… Y direction movement amount detector, 12
...... Signal processor, 13 …… Z direction moving table, 15 …… Z
Directional movement amount detector, 124 ... storage device, 128 ... deviation amount setting device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-47209 (JP, A) JP-A-50-98864 (JP, A) JP-A-51-124944 (JP, A)

Claims (1)

[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 object to be measured. 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. When the detector and the object to be measured are optical flat,
A movement table displacement amount setting device in which a height signal output from the optical sensor is stored in advance in association with a movement amount output from the X direction movement amount detector and the Y direction movement amount detector; A storage device that stores the height signal output value from the optical sensor at a certain point of time, this value stored in the storage device, and the height signal from the optical sensor are compared, and the difference between the two is zero. And a Z-direction movement control device that outputs a control signal for moving the Z-direction movement table in a direction approaching to, the difference between the value stored in the storage device and the height signal from the optical sensor approaches zero. When the height signal from the optical sensor and the movement amount from the Z-direction movement amount detector at the time are added, a deviation amount set in the movement table deviation amount setting device from the addition result of the addition device Is the amount of movement in the X direction A surface shape measuring device comprising: a detector and a subtracting device that outputs a value subtracted in correspondence with the movement amount output from the Y-direction movement amount detector as a surface height measurement value.