JPH0989550A - High-accuracy surface configuration measuring method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To markedly enlarge a measuring range along height by inputting a signal of the difference between a detected physical quantity and a target value to a drive mechanism, and operating a coarse adjustment mechanism so that the amount of displacement of a driven mechanism is held constant. SOLUTION: The distance between a probe 1 and a subject 12 for measurement is detected from physical quantities such as tunnel current, electrostatic capacity, interatomic force, and optical, acoustic, and dynamical variations. A signal of the difference between each of the detected physical quantities and a desired value for keeping the physical quantity constant is input to a coarse adjustment mechanism 3 and a fine adjustment mechanism 2. As a result, the mechanisms 3, 2 are controlled simultaneously, so the mechanism 3 whose response speed is lower than that of the mechanism 2 operates to correspond to measurements of the components with larger amplitude of a surface configuration. Therefore, the mechanism 3 is operated in such a way as to hold the amount of variation of the mechanism 2 constant, so as to enable a measuring range along height to be significantly increased without lowering measuring resolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention requires a large measurement range in the height direction and high precision measurement such as surface roughness measurement of machine parts and machined surfaces and shape / dimension measurement of fine parts. This invention is useful when applied to the measurement of surface shape.

[0002]

2. Description of the Related Art Conventionally, a stylus type surface roughness measuring method, an optical type surface roughness measuring method, a scanning tunneling microscope (STM), an intermolecular force microscope (AFM), a laser have been used for highly accurate surface shape measurement. A microscope is used.

[0003]

However, the above-mentioned prior art has the following problems. That is, in the stylus type surface roughness measurement method, the measurement resolution is determined for each measurement magnification, and when measuring an object with a large step or a large roughness value, the measurement magnification is lowered, that is, If the measurement range in the height direction of the cross-section curve is increased, the measurement resolution will decrease accordingly. Further, in the optical surface roughness measuring method, the measuring range in the height direction of the sectional curve is as small as about 3 μm. Furthermore, in the scanning tunnel microscope and the intermolecular force microscope, the measuring range in the height direction is about 10 μm at the maximum. However, these measurement methods have a problem that the measurement range in the height direction is small, although the measurement resolution has high accuracy of the order of nanometers. Further, in the laser microscope, the measurement resolution is about 10 nm at the maximum, and there is a problem that the measurement resolution is low.

The present invention has been made in view of the above problems of the conventional method, and has a high precision resolution of several nanometers,
Moreover, it is an object of the present invention to provide a high-accuracy surface shape measuring method and its apparatus, which has a large measuring range in the height direction of several tens of μm or more.

[0005]

In order to solve the above problems, the present invention provides the method according to claim 1 in which the distance between the surface of the object to be measured and the probe is determined by the tunnel current, the electrostatic capacity, and the interatomic distance. Detected as force, optical change, acoustic change, mechanical change or other physical quantity, the probe or the object to be measured is in the in-plane direction of the surface of the object to be measured, specifically, the direction parallel to the surface of the non-object to be measured. The probe is moved in the (X-axis direction), and the probe is moved in the out-of-plane direction of the measured object surface, specifically, in the direction perpendicular to the surface (Z-axis direction) so that the physical quantity has a constant value. By detecting the displacement of the drive mechanism for moving,
In the high-accuracy surface shape measuring method for measuring the shape of the surface of the object to be measured, the drive mechanism is used with a coarse movement mechanism having a large movement amount and a low movement resolution, and a fine movement mechanism having a small movement amount and a high movement resolution. , A signal consisting of the difference between the physical quantity detected by the probe and a target value for keeping the physical quantity constant is input to the coarse movement mechanism and the fine movement mechanism, and the coarse movement mechanism and the fine movement mechanism are coordinated almost at the same time. By controlling
We propose a high-accuracy surface profile measuring method that activates the coarse movement mechanism so that the displacement of the fine movement mechanism becomes almost constant.

As a concrete means for achieving the invention, in the invention described in claim 2, as shown in FIGS. 1 and 2, the distance between the surface of the object to be measured 12 and the probe 1 is set as follows. Means for detecting tunnel current, electrostatic capacitance, atomic force, optical change, acoustic change, mechanical change and other physical quantities, and moving the probe or the object to be measured in the in-plane direction of the surface of the object to be measured. In the high-precision surface profile measuring device including a moving mechanism for moving the probe and a drive mechanism for moving the probe in the out-of-plane direction of the surface of the object to be measured so that the physical quantity has a constant value, a large moving amount and a moving resolution Of the coarse movement mechanism 3 having a low movement speed (especially low response speed) and the fine movement mechanism 2 having a small movement amount and a high movement resolution (especially high response speed) and the drive mechanism for the probe 1 and the probe 1. The detected physical quantity and physical quantity By inputting a signal consisting of a difference from a target value for keeping it constant to the coarse movement mechanism 3 and the fine movement mechanism 2 and controlling the coarse movement mechanism 3 and the fine movement mechanism 2 almost simultaneously, the fine movement mechanism 2 Control means for activating the coarse movement mechanism 3 so that the amount of displacement is substantially constant, and displacement detection means 8/9 for detecting the displacements of the fine movement mechanism 2 and the coarse movement mechanism 3. We propose a precision surface profile measuring device.

Here, the relative relationship between the coarse movement mechanism 3 and the fine movement mechanism 2 having a large (small) movement amount, a low (high) movement resolution, and a slow (fast) response speed is merely shown.

In this case, in order to facilitate the control of the coarse movement mechanism 3 and the fine movement mechanism 2 in a coordinated manner at substantially the same time, the fine movement mechanism 2 having a fast response speed with the probe 1 attached to the tip thereof.
Is preferably attached to the free end side of the coarse movement mechanism 3 having a slow response speed. More specifically, for example, the piezoelectric elements 4a and 4b as displacement generating means and the parallel springs 3a and 3a formed of elastic hinges are connected in two stages in series. A piezoelectric device having a coarse movement mechanism 3 including a displacement enlargement means 30 for enlarging and a coarse movement mechanism 3 attached to, for example, the free end side of the displacement enlargement means 30 and having the probe 1 attached to the tip thereof. It is preferable that the fine movement mechanism 2 is composed of an element.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, the distance between the probe 1 and the object 12 to be measured can be calculated by using tunnel current, electrostatic capacitance, atomic force, optical change, acoustic change, mechanical change, etc. A signal, which is detected by a physical quantity and is a difference between the physical quantity detected by the probe 1 and a target value for keeping the physical quantity constant, is input to the coarse movement mechanism 3 and the fine movement mechanism 2. As a result, the coarse movement mechanism 3 and the fine movement mechanism 2 are controlled at the same time, so that the coarse movement mechanism 3 having a slower response speed than the fine movement mechanism 2 does not respond to the measurement of a component having a large amplitude in the surface shape. The fast fine movement mechanism 2 makes a movement corresponding to the measurement of a minute amplitude component. Therefore, the coarse movement mechanism 3 is operated so that the displacement amount of the fine movement mechanism 2 is always substantially constant, and the measurement range in the height direction can be dramatically increased without lowering the measurement resolution. Become.

Embodiments of the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. It's just FIG. 1 is a schematic configuration diagram of a surface profile measuring apparatus showing an embodiment of the present invention. As shown in the figure, the probe 1 is attached to the fine movement mechanism 2, and the fine movement mechanism 2 is attached to the lower surface of the coarse movement mechanism 3. Further, the fine movement mechanism 2 uses a piezoelectric element having a maximum displacement of 15 μm, and is configured to be finely displaced in the vertical direction.

The probe 1 attached to the lower end of the piezoelectric element 2 uses a tungsten needle having a sharpened tip. The coarse movement mechanism 3 includes a displacement portion composed of a pair of piezoelectric elements 4a and 4b arranged vertically and in parallel, and the piezoelectric elements 4a and 4a.
As the displacement magnifying means 30 for magnifying the displacement of 4b, parallel springs 3a and 3a, which are elastic hinges driven by the displacement of the piezoelectric elements 4a and 4b, are connected in two stages in series. Piezoelectric elements 4a, 4 by 3a
The displacement of b can be magnified to obtain a maximum displacement of 60 μm. More specifically, the parallel springs 3a, 3a
Is composed of elastic hinges 31A and 31B extending horizontally from the upper and lower sides of the vertical fixed wall 30 and a vertical displacement wall 32 vertically connecting the free end sides of the corresponding upper and lower elastic hinges 31A and 31B. On the other hand, the piezoelectric elements 4a and 4b are interposed between the horizontal fixed arm 34 extending horizontally from the vertical fixed wall 36 and the lower elastic hinge 31A.

As a result, the elastic hinge 31A receives the vertical displacement of the piezoelectric elements 4a and 4b, and the displacement is expanded, and the vertical displacement wall 32 is expanded and displaced in the vertical direction.
It is transmitted to the fine movement mechanism 2 and the probe 1 provided on the lower surface side of 2. Reference numeral 50 denotes a Z-axis stage that moves the coarse movement mechanism 3 up and down, which is configured by the base plate 5 and the micrometer head 6, and is configured so that the coarse movement mechanism 3 can be moved up and down in accordance with the rotation of the micrometer head 6. The Z-axis stage 50 is fixed to the column 7.

In the lower left corner of the base plate 5 in the figure,
The displacement gauge 8 is attached, and the tip of the displacement portion is brought into contact with the upper surface of the tongue piece 32A extending horizontally from the lower side portion of the vertical displacement wall 32 so that the vertical displacement of the coarse movement mechanism 3 can be efficiently measured. ing. Since it is difficult to directly measure the displacement of the fine movement mechanism 2, the same applied voltage is applied to each of the fine movement mechanism 2 and the displacement observation piezoelectric element 10, so that the piezoelectric element of the fine movement mechanism 2 and the displacement observation piezoelectric element 10 are applied. Indicates the same displacement, and therefore the displacement of the fine movement mechanism 2 can be monitored by measuring the displacement of the displacement observing piezoelectric element 10 with the displacement meter 9. The fine movement mechanism 2 and the displacement observing piezoelectric element 10 having the same characteristics are required for accurate monitoring.

The object to be measured 12 is mounted on a feed table 11 which is movable in the arrow direction (horizontal direction orthogonal to the Z axis) in the figure, and the object to be measured 12 is tunneled between the object 1 and the probe 1. A bias voltage 13 for generating a current is applied.
Further, a control circuit 14 for controlling the piezoelectric elements of the fine movement mechanism 2 and the piezoelectric elements 4a, 4b of the coarse movement mechanism 3 and a high voltage amplifier 15 for driving the piezoelectric elements are connected.

Next, FIG. 2 is a control block diagram of a controller incorporated in the surface profile measuring apparatus. The operation of this embodiment will be described with reference to FIG. FIG.
In the figure, C is the control target value of the fine movement mechanism 2, B is the control target value of the coarse movement mechanism 3, and A is the surface shape of the DUT 12. Here, 16 is a conversion coefficient setting circuit for the tunnel current flowing between the probe 1 and the DUT 12 and the distance between the probe 1 and the DUT 12, and a current / voltage for converting the tunnel current into a voltage. It includes a conversion circuit (I / V amplifier) and a logarithmic conversion circuit. Reference numeral 17 is an integrator, 15a is a high voltage amplifier for driving the piezoelectric elements of the fine movement mechanism 2, 15b is a high voltage amplifier for driving the piezoelectric elements 4a and 4b of the coarse movement mechanism 3, Df
And Dc represent displacement outputs of the fine movement mechanism 2 and the coarse movement mechanism 3.

In the measurement, first, the Z-axis stage 50 is moved by the micrometer head 6 and adjusted so that the distance between the probe 1 and the object 12 to be measured falls within the operating range of the coarse movement mechanism 3. A tunnel current is generated between the device under test and the device under test 12. The tunnel current detected by the probe 1 passes through the conversion coefficient setting circuit 16 and becomes a voltage signal proportional to the distance between the DUT 12 and the probe 1.

The difference between this voltage signal and the target value C of the fine movement mechanism 2 is integrated by the integrator 17, and the piezoelectric element of the fine movement mechanism 2 is driven via the high voltage amplifier 15a for driving the piezoelectric element. As a result, the expansion / contraction amount of the piezoelectric element of the fine movement mechanism 2 is controlled so that the difference between the output voltages of the target value C and 16 becomes zero, and the distance between the DUT 12 and the probe 1 is always kept substantially constant. You will be drunk. On the other hand, the output signal E of the integrator 17 is the coarse movement mechanism 3
Is also given to.

As a result, the difference between E and the target value B of the coarse movement mechanism 3 is input to the integrator 18, and the displacement of the coarse movement mechanism 3 is controlled. As for the value of B, the piezoelectric element of the fine movement mechanism 2 has an input voltage of 10
Since the extension is 15 μm with respect to 0 V, the gain is set to 5 V in consideration of the gain of the piezoelectric element driving high-voltage amplifier 15a which is 10 times. As a result, the displacement of the coarse movement mechanism 3 is controlled so that the extension of the fine movement mechanism 2 always maintains 7.5 μm.

In this state, when the feed table 11 is moved in the X axis direction, the fine movement mechanism 2 and the coarse movement mechanism 3 are controlled by the control circuit 14 according to the surface shape of the object 12 to be measured, and the surface shape is Dc + Df. To be detected.

FIG. 3 shows the result of measuring the shape of the standard piece for calibrating the stylus type surface roughness measuring instrument with the configuration of the above-mentioned embodiment. In the figure, (a) shows the measurement result by the stylus type surface roughness measuring instrument, and (b) shows the sum of the displacements of the coarse movement mechanism 3 and the fine movement mechanism 2, that is, the measurement result of the surface shape by the apparatus of this embodiment. Indicates. Further, (c) and (d) show the displacements of the coarse movement mechanism 3 and the fine movement mechanism 2, in other words, the values of Dc and Df, respectively.

From FIG. 3, it can be seen that the measurement results obtained by the apparatus of this embodiment and the stylus type surface roughness measuring device are in good agreement including the amplitude. It can also be understood that the apparatus of the present embodiment effectively captures minute displacements that could not be captured by the measuring method using the stylus type surface roughness measuring device. Therefore, it can be said that the measuring device is effectively functioning.

FIG. 4 shows the result of measuring the surface of the object to be measured 12 obtained by milling an aluminum alloy with the configuration of the above embodiment. The processing conditions are: spindle rotation speed 67 rpm,
The table feed is 80 mm / min. (A) shows the measurement result by the stylus type surface roughness measuring device, and (b) shows the measurement result by the apparatus of the present embodiment. The maximum height of the cross-sectional shape is about 30 μm, and both are in good agreement. The maximum height of this cross-sectional shape is the maximum displacement of the fine movement mechanism 2 of 15μ.
Since m is exceeded, it can be seen that the measurement is effectively performed by the control function in which the coarse movement mechanism 3 and the fine movement mechanism 2 cooperate with each other.

Further, the stylus type surface roughness measuring device has variations in the measurement of the deep narrow groove width portion, but the present invention can also effectively measure such a portion. In the present embodiment, the distance between the probe 1 and the object to be measured 12 is detected as a tunnel current, but the distance between the probe 1 and the object to be measured 12 is calculated as follows. Even if it is detected as an interatomic force, an electrostatic capacitance, an optical change, an acoustic change, or a mechanical change between them, the same measurement as in this embodiment can be performed. In that case, the conversion coefficient circuit 16 of FIG.
However, it is only a conversion coefficient between each of these physical quantities and the distance between the probe 1 and the object to be measured 12, and other configurations can be set to be the same.

[0024]

As described above in detail, according to the present invention, the distance between the probe and the object to be measured is set to some physical quantity (tunnel current, capacitance, atomic force, optical change, Acoustic change, mechanical change, etc.), and a signal consisting of a difference from a target value for keeping the physical quantity detected by the probe constant is input to the coarse movement mechanism and the fine movement mechanism. Since the coarse movement mechanism and the fine movement mechanism are controlled at the same time, the coarse movement mechanism, which has a slower response speed than the fine movement mechanism, has a small response for the measurement of a component with a large amplitude in the surface shape. The movement will correspond to the measurement of various amplitude components. Therefore, the coarse movement mechanism operates so that the displacement amount of the fine movement mechanism is always almost constant, and it is possible to dramatically increase the measurement range in the height direction without lowering the measurement resolution. Is.

Further, according to the present invention, since the frequency characteristic of the probe drive system can be enhanced, the surface profile measurement can be speeded up and the disturbance resistance characteristic can be improved. It can also be applied to process measurement.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a surface shape measuring apparatus showing an embodiment of the present invention.

FIG. 2 is a control block diagram of a control device incorporated in the surface profile measuring apparatus of FIG.

3A and 3B show the shape measurement results of a calibration standard piece by the measuring apparatus of FIG. 1 and a known stylus-type surface roughness measuring instrument. FIG. 3A is a stylus-type surface roughness measuring instrument, and FIG. The sum of the displacements of the mechanism and the fine movement mechanism, that is, the measurement result of the surface shape by the apparatus of this embodiment is shown. Further, (c) and (d) show displacement values of the coarse movement mechanism and the fine movement mechanism, respectively.

4A and 4B show measurement results obtained by measuring the surface of an object to be measured by milling an aluminum alloy material, where FIG. 4A is a measurement result obtained by a stylus-type surface roughness measuring instrument, and FIG. 4B is a measurement result obtained by the apparatus of this embodiment. The results are shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Probe 2 Fine movement mechanism 3 Coarse movement mechanism 4a, 4b Piezoelectric element 8, 9 Displacement meter 11 Feeding table 12 Measured object 14 Control circuit

Claims (4)

[Claims] 1. The probe detects the distance between the surface of the object to be measured and the probe as a tunnel current, electrostatic capacitance, atomic force, optical change, acoustic change, mechanical change or other physical quantity, Or of the drive mechanism for moving the measured object in the in-plane direction of the measured object surface, and moving the probe in the out-of-plane direction of the measured object surface so that the physical quantity becomes a constant value. In a high-precision surface shape measuring method for measuring the shape of the surface of the object to be measured by detecting a displacement, the drive mechanism is a coarse movement mechanism having a relatively large movement amount and a low movement resolution, and relatively. A fine movement mechanism having a small movement amount and high movement resolution is used, and a signal composed of a difference between the physical quantity detected by the probe and a target value for keeping the physical quantity constant is supplied to the coarse movement mechanism and the fine movement mechanism. Input the coarse movement mechanism and fine movement mechanism Precision surface shape measuring method, wherein by controlling, amount of displacement of the fine movement mechanism is to actuate the coarse feed mechanism to be substantially constant. 2. A means for detecting the distance between the surface of the object to be measured and the probe as a physical quantity such as tunnel current, electrostatic capacity, atomic force, optical change, acoustic change, mechanical change, or the like, Moving means for moving the probe or the object to be measured in the in-plane direction of the surface of the object to be measured, and a drive mechanism for moving the probe out of the surface of the object to be measured so that the physical quantity has a constant value. In a high-precision surface profile measuring device equipped with, a coarse movement mechanism having a relatively large movement amount and a low movement resolution,
A signal that is composed of a drive mechanism of the probe, which is composed of a fine movement mechanism having a relatively small movement amount and high movement resolution, and a difference between the physical quantity detected by the probe and a target value for keeping the physical quantity constant. Control means for inputting to the coarse movement mechanism and the fine movement mechanism to control the coarse movement mechanism and the fine movement mechanism almost at the same time to operate the coarse movement mechanism such that the displacement amount of the fine movement mechanism is always substantially constant, A high-accuracy surface profile measuring device comprising: a displacement detecting means for detecting displacements of the fine moving mechanism and the coarse moving mechanism. 3. The high-accuracy surface profile measurement according to claim 2, wherein a fine movement mechanism having a fast response speed, the tip of which is attached to the fine movement mechanism, is attached to a coarse movement mechanism having a slow response speed. apparatus. 4. A coarse movement mechanism comprising a piezoelectric element that generates a displacement and a displacement enlargement means that enlarges the displacement of the piezoelectric element; and a coarse movement mechanism attached to the displacement enlargement means side of the coarse movement mechanism, and
3. A high precision surface profile measuring apparatus according to claim 2, further comprising a fine movement mechanism including a piezoelectric element having the tip attached to the tip.