JPH05312538A - Three-dimensional shape measuring instrument - Google Patents

Abstract

PURPOSE:To correct the straightness of a stage and measure the shape of an object to be measured with high accuracy by detecting the difference in height between the object and a plane mirror for reference and inclination of the plane mirror for reference with an optical probe. CONSTITUTION:The inclination of a plane mirror 3 for reference can be found from the position of a beam detected by means of a position detector (PSD), because the position of the light transmitted through the half mirror 62c of an optical probe 6 changes. The part of the light reflected by the mirror 62c interferes with the light from a mirror 63a of a measuring optical path after advancing an optical path from a PSD 65 to a photodiode 71 through the mirror 62c. Since the photodiode 71 outputs the variation of the height difference between an object 4 to be measured and the mirror 3 as interference signals, the height difference is found by integrating the interference signals. Since the movement of a movable stage section 2 is measured with a laser length measuring instrument 5, a controller 8 finds the surface shape of the object 4 by combining the position of the section 2 and the height difference obtained from the probe 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional shape measuring apparatus for measuring the surface shape of an object by utilizing the interference of laser light, and particularly, for measuring by measuring an object to be measured or an optical probe. The present invention relates to an apparatus capable of highly accurately measuring a shape by detecting an error caused by the straightness of a sweeping means at that time.

[0002]

2. Description of the Related Art FIG. 2A is a schematic diagram showing an example of a conventional three-dimensional shape measuring apparatus. An object to be measured is placed on a stage, and one point on the surface is measured by an optical probe as a height. The surface shape was obtained by measuring, moving the stage, and sweeping the measured object.

[0003]

However, in the three-dimensional shape measuring apparatus shown in the above prior art, when the stage moves from the state of FIG. 2A to the next measuring point,
When the object to be measured moves in parallel in the height direction as shown in FIG. 2B, or when the object moves in a tilted manner as shown in FIG. 2C, the optical probe is measured. The surface shape of the object and the straightness of the stage were measured as a value, and an accurate shape could not be measured.

The present invention has been made in view of the above problems of the prior art. The object to be measured and the reference plane are placed on the same stage, the measurement points are swept, and the difference in height and the reference plane are set. The object of the present invention is to provide a three-dimensional shape measuring apparatus capable of correcting the straightness of the stage and measuring the shape with high accuracy by simultaneously measuring the inclination of the.

[0005]

The structure of the present invention for solving the above-mentioned problems is a stage for placing an object to be measured and sweeping a shape measuring point, and an object to be measured placed on this stage. A plane mirror serving as a reference plane that moves in the same way,
An optical probe for detecting the height difference between the DUT and the reference plane mirror, an angle detector for detecting the inclination of the reference plane mirror with respect to the movement of the stage, and a movement of the stage. From the output of the position detector, the optical probe, the angle detector, and the position detector.
A distance between two points for detecting a difference between the angle of inclination of the reference plane mirror detected by the angle detector and the height between the DUT and the reference plane mirror. The straightness of the stage is corrected by subtracting from the output of the optical probe as a value of the product of and the value due to the influence of the inclination in the sweep of the stage.

[0006]

According to the present invention, even if the stage moves vertically or inclined with respect to the feed direction, by measuring the difference in height between the reference plane mirror and the object to be measured, the vertical movement of the stage can be reduced. Not affected, and by measuring the tilt of the reference plane mirror and removing the effect from the height difference,
The effect of tilting and moving the stage can be eliminated, and accurate surface shape can be measured.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a three-dimensional shape measuring apparatus of the present invention. In FIG. 1, 1 is a stage, 2 is a movable part of the stage 1, and a reference plane mirror 3 is provided on the movable part 2.
And the object to be measured 4 is mounted. Reference numeral 5 is a laser length measuring device as a position detector for measuring the movement of the movable part 2. 6 is an optical probe for detecting the difference in height between the object to be measured and the reference plane mirror, 61 is a laser light source for interference measurement, 62a,
62b is a half mirror, 63a and 63b are mirrors, 64
Reference numerals a, 64b, and 64c are focus error detection optical systems each including a lens, a cylindrical lens, and a four-division photodiode, and detect a focus error of an objective lens 67b described later. Reference numerals 65a and 65b are polarization beam splitters (hereinafter simply referred to as PBS), 66a and 66b are quarter-wave plates for converting the polarization state, 67a and 67b are objective lenses, 68 is a lens actuator, and 69 is a focus error detection optical system. Actuator drive circuit for returning the signal from the lens to the lens actuator to adjust the focal position,
Is a position detector (Position Sensitive Device: hereinafter referred to as PSD) for detecting the position of light as an angle detector for detecting the inclination of the reference plane mirror 3 with respect to the movement of the stage 1, and 71 is an interference signal. Is a photodiode for detecting. Reference numeral 7 indicates the movement of the stage 1, and the height data by the interference signal of the optical probe 6 (photodiode 71) and the stage movable portion 2 by the PSD 70.
Is a control device for obtaining the shape of the DUT 4 from the tilt of the laser measuring device 5 and the position of the movable stage 2 by the laser length measuring device 5.

In such a structure, the laser light source 61
The light emitted from is split into two directions by the half mirror 62a. The reflected light enters the measuring optical path and is reflected by the mirror 63.
Part of the light passes through the half mirror 62b via a, and the PBS
The object to be measured 4 is irradiated with and reflected by the object 65 through the objective lens 67b. The reflected light passes through the objective lens 67b and the quarter wave plate 66b, and is reflected by the PBS.
Reflected by 65b, mirror 63b → PBS 65b → 1 /
After passing through the four-wave plate 66b and the objective lens 67b, the DUT 4 is irradiated again and reflected. The reflected light passes through the objective lens 67b → a quarter wave plate 66b → PBS 65b,
Part of the light passes through the half mirror 62b and is reflected by the mirror 63a. Part of the light passes through the half mirror 62a and enters the photodiode 71. In addition, in the double path from the incidence to the exit of the PBS 65b, the incident light and the outgoing light have the same optical path even if the DUT 4 is tilted.

The light reflected by the half mirror 62b is incident on a focus error detection optical system including a lens 64a, a cylindrical lens 64b, and a four-divided photodiode 64c, and is fed back to a lens actuator 68 by an actuator drive circuit 69, so that it is constantly reflected. The objective lens 67b is brought into a focused state.

The light emitted from the laser light source 61 that has passed through the half mirror 62a is incident on the reference optical path, and is reflected by the PBS 65a.
-> 1/4 wavelength plate 66a-> It passes through the objective lens 67a and is incident on the reference plane mirror 3 and reflected. The reflected light is
Objective lens 67a → quarter wave plate 66a → PBS 65a
→ half mirror 62c → PBS 65a → quarter wave plate 6
6a → Passes through the objective lens 67a and is incident again on the reference plane mirror 67a and is reflected. A part of the reflected light passes through the objective lens 67a, the quarter-wave plate 66a, and the PBS 65a, and partially passes through the half mirror 62c to enter the PSD 70. Although the configuration of the double-pass optical system is the same as that of the measurement optical path, when the reference plane mirror 3 is tilted, the position of the light passing through the half mirror 62c changes, so the PSD 7
The tilt (direction and angle) can be determined from the position of the beam detected at zero.

The light partially reflected by the half mirror 62c takes the optical path of the PBS 65a → half mirror 62a → photodiode 71 and interferes with the light from the measurement optical path. The photodiode 71 outputs, as an interference signal, a change in height difference between the DUT and the reference plane focused by the objective lenses 67b and 67a.
The height difference is integrated.

Even if the movable stage 2 moves in a direction perpendicular to the feed of the stage 1, the optical probe 6 measures it as a difference in height between the DUT 4 and the reference plane mirror 3. Therefore, it is not affected. When the movable stage 2 tilts with respect to the feed of the stage 1, the controller 8 multiplies the product of the tilt angle detected by the PSD 70 and the distance between the objective lenses 67a and 67b by
By subtracting from the height difference obtained by the optical probe 6, the influence of tilting movement can be removed.

Since the movement of the movable stage 2 is measured by the laser length measuring device 5, the surface shape of the DUT 4 is controlled by the controller 8 by matching the difference between the position and the height obtained by the optical probe 6. Required at.

The surface shape result thus obtained measures the height difference between the reference flat mirror 3 and the DUT 4 even if the stage 1 moves vertically or inclined with respect to the feed direction. Therefore, the influence of the movement of the stage 1 in the vertical direction is not influenced, and the influence is removed from the difference in height by measuring the inclination of the reference plane mirror 3 to remove the influence of the stage 1.
The effect of tilting and moving can be eliminated, and the accuracy is high.

In the above embodiment, PS for detecting the inclination of the reference plane mirror 3 with respect to the movement of the stage 1
Instead of D70, the optical probe 6 and the photoelectric autocollimator may be integrated, and the photoelectric autocollimator may measure the inclination of the reference plane mirror 3 to eliminate the influence of the inclination of the feed of the stage 1. In this case, PSD
Since it is not necessary to allocate the power of the reference light to 70, an interference signal having a high S / N can be obtained. Also, due to the optical system of the photoelectric autocollimator, regardless of the performance of PSD,
The tilt can be detected with high sensitivity.

[0016]

As described above in detail with reference to the embodiments, according to the present invention, even if the stage moves vertically or inclined with respect to the feed direction, the height of the reference plane and the height of the object to be measured can be increased. By measuring the difference in the vertical direction of the stage, and by measuring the inclination of the reference plane and removing the effect from the difference in height, the stage moved tilted. It is possible to realize a three-dimensional shape measuring apparatus capable of removing the influence and measuring the surface shape with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a three-dimensional shape measuring apparatus of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a conventional three-dimensional shape measuring apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 stage 2 stage movable part 3 reference plane mirror 4 object to be measured 5 laser length measuring device 6 optical probe 8 control device 61 laser light source 62a, 62b, 62c half mirror 63a, 63b mirror 64a lens 64b cylindrical lens 64c four-division photodiode 65a, 65b Polarization beam splitter (PBS) 66a, 66b 1/4 wavelength plate 67a, 67b Objective lens 68 Lens actuator 69 Actuator drive circuit 70 Position detector (PSD) 71 Photodiode

Claims (1)

[Claims] 1. A stage for mounting an object to be measured and sweeping a shape measuring point, a flat mirror serving as a reference surface which is mounted on the stage and moves in the same manner as the object to be measured, and the object to be measured. And an optical probe for detecting a height difference between the reference plane mirror, an angle detector for detecting the inclination of the reference plane mirror with respect to the movement of the stage, and a position detector for detecting the movement of the stage. And a control device that obtains the three-dimensional shape of the object to be measured from the outputs of the optical probe, the angle detector, and the position detector, and the angle of inclination of the reference plane mirror detected by the angle detector. By subtracting the product of the distance between two points for detecting the difference in height between the object to be measured and the reference plane mirror as the value due to the influence of the tilt in the sweep of the stage from the output of the optical probe, The above A three-dimensional shape measuring device characterized in that the straightness of the image is corrected.