JP3069931B2 - Surface shape measuring method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for measuring a three-dimensional shape of a sub-millimeter-order portion such as a trench structure of a semiconductor device, an outer shape of a bearing for a micromachine or a micromotor, and an inner surface shape of an ink nozzle in an ink jet printer. More particularly, the present invention relates to a contact-type surface shape measuring method and device using a stylus in contact with a surface to be measured.

[0002]

2. Description of the Related Art With the miniaturization, integration, and precision of equipment, fine processing is often performed, and the surface shape of minute parts is measured to confirm the processing accuracy. Is required.
The method of measuring the uneven shape of the surface of the object to be measured is roughly classified into a contact type and a non-contact type. Conventionally, a contact-type surface shape measurement method moves a stylus along a surface to be measured while pressing the stylus against the surface to be measured, and mechanically, optically, or electrically displaces the stylus or a load applied thereto. The unevenness on the surface is detected. According to this contact-type surface shape measuring method, there is a feature that the measurement can be performed with a simple mechanism and the operation becomes easy. In addition, the non-contact type surface shape measurement method electromagnetically detects the distance between the probe and the surface to be measured, and moves the probe so that the distance is kept constant. , And the unevenness of the surface is measured from the amount of movement of the probe at that time. A scanning tunneling microscope is known as a typical non-contact type surface measuring apparatus by such a method. Using that technique, it is possible to measure extremely fine irregularities.

[0003]

However, in the case of the conventional contact-type surface shape measuring method or apparatus, it is necessary to maintain the contact when the stylus is moved along the surface to be measured. Therefore, it is necessary to apply a relatively large measuring load to the stylus. For example, even when the stylus is displaced in accordance with surface irregularities and the surface shape is measured from the displacement, a pressing pressure of at least 1 g or more must be applied in order to improve the followability of the stylus. To detect surface irregularities from a change in the load applied to the stylus, a larger pressing pressure is required. When such a pressing pressure is applied, when the stylus is thin, the stylus bends, so that it becomes difficult to measure the load or the displacement.
Therefore, the stylus and its support need to have high rigidity, and its diameter cannot be reduced to 1 mm or less. Therefore, in the conventional one, the diameter is 1mm
It is almost impossible to measure the shape of the inner surface of the following deep hole or the side surface of the deep groove having a width of 1 mm or less. Also,
Since the measurement is performed by enlarging the load or the displacement of the stylus, the effect of the dimensional change of the mechanism due to the temperature change and the characteristic change of various sensors becomes large, and there is a problem that the accuracy cannot be prevented from decreasing.

On the other hand, in the case of a non-contact type surface shape measuring method or apparatus, the probe can be made thin because the probe does not contact the surface to be measured. However,
If gas or liquid is interposed between the probe and the surface to be measured, the gas or liquid is affected by the inclusions, so that it is difficult to use the gas or liquid in a factory with a bad measurement environment. Also, since the clearance between the probe and the surface to be measured must be extremely small, it is necessary to make the scanning speed of the probe extremely low in order not to make them contact. Therefore, it is not suitable for the measurement of industrial products having dimensions of about sub-millimeters or more. Further, since the probe scanning mechanism and the like are complicated and large, it is difficult to apply the method to the measurement of the inner surface shape of the hole.

The present invention has been made in view of such circumstances, and has an object to measure a surface shape of a sub-millimeter minute portion such as an inner surface shape of a hole having a diameter of 1 mm or less. To provide a simple method and apparatus.

[0006]

According to the present invention, in order to achieve this object, a stylus is vibrated at a constant amplitude in a direction in which it comes into contact with a surface to be measured, and a ratio of a contact time to a vibration period of the stylus is measured. Thus, the distance between the center of vibration of the stylus and the surface to be measured is calculated. The contact between the stylus and the surface to be measured is detected by electrical conduction therebetween. The center of vibration of the stylus is relative to the surface to be measured along a predetermined path or such that the ratio of the contact time between the stylus and the surface to be measured to the vibration period of the stylus is constant. Moved to Then, the movement amount of the stylus vibration center at that time is recorded.

[0007]

[Function] When the stylus vibrating at a constant amplitude is brought closer to the surface to be measured, the contact time is short when the center of vibration of the stylus is far from the surface to be measured. The time gets longer. Therefore, the distance from the center of vibration of the stylus to the surface to be measured is determined by the contact time. Then, if the center of vibration of the stylus is relatively moved along a predetermined path, a change in the distance of the measurement target surface with respect to the path is obtained. That is, the uneven shape of the measurement target surface is measured. Also, if the center of vibration of the stylus is relatively moved along the surface to be measured while the ratio of the contact time between the stylus and the surface to be measured to the vibration period of the stylus is kept constant, The distance between the center of vibration of the stylus and the surface to be measured is always kept constant. Therefore, the uneven shape of the surface to be measured is determined from the amount of movement of the stylus for maintaining the state. Then, since the contact between the stylus and the surface to be measured is detected by electrical conduction therebetween, the contact pressure may be small. Therefore, the stylus can be made thin,
The surface shape can be measured even in a minute area.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In the drawing, FIG. 1 is a configuration diagram showing a principle of a measuring apparatus for performing a surface shape measuring method according to the present invention. As is apparent from this figure, the stylus 1 is moved by the piezo actuator 2 which is a stylus vibrating device.
Oscillates at a constant period and a constant amplitude in one X-axis direction in a horizontal plane around the neutral position. On the other hand, the measuring object 3 is set on the Z-axis table 4 so that the measuring object surface 3a is substantially vertical. The Z-axis table 4 is moved by the Z-axis feed mechanism 5
It is driven at a constant speed in the Z-axis direction perpendicular to the axis. Thus, the stylus 1 moves along a path parallel to the Z axis, that is, a predetermined path substantially parallel to the measurement target surface 3a,
It is configured to move relatively to the measurement target 3. Therefore, the Z-axis feed mechanism 5 is a moving device that relatively moves the stylus 1 with respect to the measurement target surface 3a. The relative movement amount of the stylus 1 by the Z-axis feed mechanism 5 is sent to the computer 6.

The stylus 1 and the measuring object 3 are both conductive. A voltage is applied between the stylus 1 and the measurement target 3 from a power supply provided in the conduction time detection circuit 7. The conduction time detection circuit 7 outputs a constant signal while the contact between the stylus 1 and the measuring object 3 is conducted. The output signal is guided to the computer 6. In the computer 6, a predetermined calculation is performed based on a vibration cycle of the stylus 1 set in the actuator 2 and an output signal from the conduction time detection circuit 7. Then, the calculation result and the relative movement amount of the stylus 1 are recorded in an internal memory and output to the printer 8 and the CRT display 9. That is, the computer 6 serves as both an arithmetic device and a recording device.

Next, the operation of the thus configured surface profile measuring apparatus will be described. Now, it is assumed that the stylus 1 is oscillating in the X-axis direction in a sine wave shape as shown in FIG. At this time, assuming that the measurement target surface 3a is separated from the vibration center of the stylus 1 by a distance s, the stylus 1 contacts the measurement target surface 3a while the vibration displacement of the stylus 1 is larger than the distance s. Will be. When they are in contact with each other, electrical continuity is provided therebetween, and when they are apart from each other, electrical continuity is provided between them. Therefore, at this time, a conduction / non-conduction signal as shown in FIG. 3B is output from the conduction time detecting circuit 7 for detecting the electrical conduction between the stylus 1 and the measuring object 3. You. The duration of the conduction signal, that is, the contact time between the stylus 1 and the measurement target 3 increases as the distance s between the vibration center of the stylus 1 and the measurement target surface 3a decreases. When this contact time is determined as the duty cycle of the waveform representing the conduction state, that is, the ratio of the conduction time to the stylus oscillation cycle, the duty cycle is determined by the distance between the oscillation center of the stylus 1 and the surface 3a to be measured. It changes as shown in FIG. 3 depending on s. That is, the distance s is larger than the vibration amplitude of the stylus 1,
When the stylus 1 does not contact the measurement target surface 3a, the duty cycle is 0, and the duty cycle increases as the center of vibration of the stylus 1 approaches the measurement target surface 3a. When the stylus 1 does not separate from the measurement target surface 3a even when vibration is applied, the duty cycle becomes 1. Therefore, the position of the measurement target surface 3a with respect to the vibration center of the stylus 1 can be known by calculating the duty cycle, that is, the ratio of the conduction time to the stylus vibration period.

In the computer 6, this duty cycle is calculated based on the output signal from the conduction time detecting circuit 7 and the oscillation cycle of the stylus 1 set in the actuator 2. And its duty cycle,
A calibration graph as shown in FIG. 3 stored as a map is compared, and a distance s at that time is obtained. In this way, the distance s between the center of vibration of the stylus 1 and the measurement target surface 3a is measured. During this time, the measurement object 3 is Z
It is moved in the Z-axis direction by the shaft feed mechanism 5. And
The movement amount of the measuring object 3 in the Z-axis direction output from the Z-axis feed mechanism 5 is recorded together with the measured distance s. Thereby, the unevenness at each position in the Z-axis direction of the measurement target surface 3a is measured. Next, the stylus 1 or the measuring object 3 is moved in the Y-axis direction perpendicular to the XZ plane,
Perform a similar measurement. By repeating such measurement, the three-dimensional shape of the measurement target surface 3a can be obtained.

As described above, according to this surface shape measuring apparatus, the shape of the surface 3a to be measured is measured by the contact state between the stylus 1 and the surface 3a to be measured, and is affected by inclusions therebetween. There are few things. In addition, since the distance between the center of vibration of the stylus 1 and the measurement target surface 3a is measured from the contact time between the stylus 1 vibrating at a constant amplitude and the measurement target surface 3a, it is necessary to use a load sensor or the like. In addition, the influence of a temperature change or the like can be reduced. Therefore, highly accurate measurement is possible. Since the contact between the stylus 1 and the measurement target surface 3a is detected by electrical continuity, the stylus 1 may be deformed by the contact. That is, the stylus 1 can be extremely thin. Therefore, it is also possible to measure the inner shape of the small-diameter hole. Further, by making the stylus 1 easily deformable, an impact in a case where there is a sudden change in unevenness is absorbed, so that high-speed measurement is also possible. When the measuring object 3 is electrically non-conductive, this measuring method cannot be used as it is, but in that case,
An extremely thin conductive film may be formed on the measurement target surface 3a by sputtering or the like. By doing so, it becomes possible to measure the shape of the surface of the measuring object 3 irrespective of the conductivity.

By the way, in the surface shape measuring apparatus of the above embodiment, the measuring range is limited to the range of the vibration amplitude of the stylus 1. In addition, to increase the sensitivity, it is necessary to reduce the amplitude, so that the measurement range is further reduced. Also, for the conversion from duty cycle to distance, a calibration graph as in FIG. 3 must be used. In order to solve these problems, it is effective to configure a measurement system having a shape as shown in FIG. In this surface profile measuring device, the entire stylus 1 and the piezo actuator 2 as a vibrating device are moved by the X-axis driving mechanism
It is adapted to be moved in the axial direction. In addition, the ratio of the electrical conduction time between the stylus 1 and the measurement target surface 3a to the stylus oscillation cycle, that is, the duty cycle, is measured by the duty cycle measurement device 11 including the conduction time detection circuit 7 in the above-described embodiment. The X-axis drive mechanism 10 is controlled by an output signal from the duty cycle measuring device 11. When such a system is configured and the stylus system is moved so that the measured duty cycle maintains a constant value, the center of vibration of the stylus 1 is always kept at a fixed distance from the surface 3a to be measured. Will be. Therefore, the position of the measurement target surface 3a can be known from the movement amount. In that case, since both are in a proportional relationship, there is no need for conversion. In addition, since only the positional relationship where the duty cycle is constant is used, the measurement range is independent of the vibration amplitude of the stylus 1. Therefore, it is possible to measure a large change in surface position with high sensitivity. This X-axis drive mechanism 1
By moving the stylus 0 and the stylus system including the stylus 1 and its vibrating device as a whole in the Z-axis direction, it is possible to measure the unevenness of the measurement target surface 3a along the Z-axis direction. .

FIG. 5 is a block diagram showing an embodiment in which the system shown in FIG. 4 is incorporated in the surface profile measuring apparatus shown in FIG. As in the embodiment of FIG. 1, the stylus 1 is vibrated in the X-axis direction by a piezo actuator 2.
The measuring object 3 is moved by the X-axis table 12 and the Z-axis table 4 in the X-axis direction, which is the direction of contact with the stylus 1, and in the Z-axis direction, which is the feed direction. The Z-axis table 4 is driven at a constant speed by a Z-axis feed mechanism 5, which is a first moving device. The amount of movement of the measurement target 3 by the Z-axis feed mechanism 5 is input to a computer 6 as a main controller as a Z-axis position of a measurement point. The X-axis table 12 is driven by an X-axis drive mechanism 10 as a second moving device. The amount of change in the distance between the stylus 1 and the measurement target surface 3a by the X-axis drive mechanism 10 is input to the computer 6 as the X-axis position of the measurement location. The contact state between the stylus 1 and the surface 3a to be measured is input to the computer 6 as data in the form of a duty cycle by the duty cycle measuring device 11. The computer 6 performs processing such as time averaging of the duty cycle and comparison with a reference value, and the like.
Output command value to The X-axis driving mechanism 10 receives the command signal and drives the X-axis table 12 to keep the distance between the center of vibration of the stylus 1 and the measurement target 3 constant. Simultaneously with this series of operations, the X-axis drive mechanism 10 and the Z-axis feed mechanism 5
The data of the X-axis position and the Z-axis position are taken into the computer 6, and the surface shape curve of the measuring object 3 is output from these data to the printer 8 and the CRT display 9 as a measurement result.

FIG. 6 shows the stylus 1 and the surface 3 to be measured when the vibration waveform is a sine wave having a frequency of 100 Hz and an amplitude of about 3 μm.
9 shows a calculated value and an experimental value of a change in the duty cycle of the conduction signal with respect to a change in the position relative to a. The time constant of the duty cycle averaging is about 1 second. From this figure, it can be seen that the displacement measurement can be performed as designed except where the duty cycle is extremely small and large. If a triangular wave is used as the vibration waveform, this relationship becomes almost linear. If the measurement is performed under these conditions so that the duty cycle is about 0.3, the deformation of the stylus 1 or its support due to the contact between the stylus 1 and the surface 3a to be measured is about 0.5 μm.
m, and a diameter of 100 μm as the stylus 1 and its support,
When a cemented carbide alloy having a length of 1 mm is used, the measured load is about 3 mN (0.3 gf). That is, the measurement load may be extremely small. Therefore, the diameter of the stylus 1 and its support can be reduced, and the shape of the inner surface of the deep hole or the side surface of the deep groove on the order of submillimeters can be measured. In the experiment of FIG. 6, the average of the duty cycle measurement value was performed using an analog low-pass filter, but the conduction time was measured for each cycle and the average value was obtained by digital calculation. Can also. By doing so, the number of samples for duty cycle averaging can be set freely regardless of the vibration frequency, so that the system can be made more flexible. The higher the excitation frequency of the stylus 1, the faster the measurement becomes possible, but the upper limit is limited by the resonance frequency of the stylus 1 including the support.

FIG. 7 is a schematic diagram showing a state where the inner surface shape of the hole is measured by the surface shape measuring device of FIG.
In this case, the measuring object 3 having the hole 13 is set on the turntable 14 such that the longitudinal direction of the hole 13 is substantially in the Z-axis direction. The rotary table 14 is driven to rotate around the Z axis at a constant speed by a rotary mechanism 15, and the amount of rotation is input to the computer 6. The stylus 1 is inserted into the hole 13 and the hole 13
When vibrating in the X-axis direction by the piezo actuator 2 in a state of being close to the inner surface of
The stylus 1 vibrates in the radial direction of the hole 13 and comes into contact with the inner surface of the hole 13 with the vibration. The contact state is measured by the duty cycle measuring device 11 and input to the computer 6. Then, the X-axis drive mechanism 10 is driven by a command value output from the computer 6, and the distance between the stylus 1 and the inner surface of the hole 13 is controlled to be constant. Thus, the position of the inner surface of the hole 13 in the X-axis direction is detected based on the movement amount of the measurement target 3 at that time. During this time, the measurement object 3 is rotated, so that the hole 1
The irregular shape in the circumferential direction of the inner surface of No. 3 is measured. Further, since the measurement target 3 is also moved in the Z-axis direction, the unevenness of the inner surface along the longitudinal direction of the hole 13 is also measured. in this way,
By relatively rotating the stylus 1 and the measurement target 3 along the longitudinal direction of the hole 13,
The shape of the entire inner surface of the hole 13 is measured. As described above, since the stylus 1 is extremely thin,
As long as the length of the stylus 1 is within the range, it is also possible to measure the inner surface shape of a fine hole that cannot pass through a stylus support such as an ink nozzle of an ink jet printer. Actually, a prototype of such a surface shape measuring device was manufactured,
Measurement of the inner surface shape of the mm hole confirmed that satisfactory results were obtained.

In the above embodiment, the object 3 is moved with the center of vibration of the stylus 1 kept constant. However, the stylus 1 may be moved. Further, the stylus 1 is vibrated in a direction perpendicular to the longitudinal direction. For example, when measuring the side surface of the measurement target 3 as shown in FIG. 1 or FIG. It is also possible to have an angle and vibrate in the longitudinal direction. In that case, the position of the measurement target surface 3a may be corrected based on the angle of the stylus 1.

[0018]

As is clear from the above description, according to the present invention, the following effects can be obtained. 1) Since it is a contact-type measurement method, even if a gas, a liquid, or the like is interposed between the stylus and the surface to be measured, it is hardly affected by the inclusion. Therefore, it can be used even in a factory where the measurement environment is poor. 2) Since the contact is detected by electrical continuity, the measurement load may be smaller than the detection by displacement or force. Moreover, since only the conduction needs to be detected, the stylus can be made very thin. Therefore, the present invention can be applied to shape measurement of a narrow portion such as the inside of a small hole. 3) Variation, which is a problem in the continuity measurement, can be reduced by calculating the duty cycle as an average value with an appropriate time constant. 4) Since a wide range of about 10 to 90% of the vibration amplitude can be mechanically received, the device is not damaged even if there is a sudden change in unevenness. Therefore, application to field-oriented measurement such as high-speed measurement is possible. 5) A voltage may be applied to detect electrical conduction,
There is no need for a special sensor such as a load sensor or an enlargement mechanism for expanding the detection value. Therefore, the structure is simplified, and the configuration can be made at a low cost. In addition, the accuracy does not decrease due to a temperature change or the like. Thus, according to the present invention, it is possible to measure the surface shape of various components having a fine three-dimensional structure with high accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a surface shape measuring apparatus according to the present invention.

FIG. 2 is a first explanatory diagram for explaining the principle of the measuring device.

FIG. 3 is a second explanatory diagram for explaining the principle.

FIG. 4 is a configuration diagram showing a preferred system used in the surface shape measuring device according to the present invention.

FIG. 5 is a configuration diagram showing an embodiment in which the system of FIG. 4 is applied to the surface profile measuring device of FIG. 1;

FIG. 6 is a graph showing a theoretical value and an experimental value of a duty cycle change in the surface profile measuring device of FIG. 5;

FIG. 7 is an explanatory diagram showing a state when measuring the inner surface shape of a hole using the surface shape measuring device of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 stylus 2 piezo actuator (stylus vibrator) 3 measurement object 3 a measurement target surface 4 Z-axis table 5 Z-axis feed mechanism (first moving device) 6 computer (computing device, recording device) 7 conduction time detection Circuit 10 X-axis drive mechanism (second moving device) 11 Duty cycle measuring device 12 X-axis table 13 Hole 14 Rotary table 15 Rotary mechanism

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B ^7/ 00-7/34 G01B 21/00-21/32

Claims (6)

(57) [Claims] 1. A stylus is vibrated at a constant amplitude in the direction of an angle with respect to a surface to be measured in the vicinity of the surface to be measured, and the contact between the stylus and the surface to be measured is detected by electrical conduction. From the ratio of the conduction time to the vibration cycle of the stylus,
By calculating the distance between the center of vibration of the stylus and the surface to be measured, and moving the center of vibration of the stylus along a predetermined path while recording the distance, the unevenness of the surface to be measured is obtained. A method for measuring a surface shape, comprising determining a shape. 2. A stylus is vibrated at a constant amplitude in the direction at an angle to the surface to be measured in the vicinity of the surface to be measured, and the contact between the stylus and the surface to be measured is detected by electrical conduction. The distance between the center of vibration of the stylus and the surface to be measured is changed so that the ratio of the conduction time to the vibration cycle of the stylus is constant. Moving the surface of the object to determine the uneven shape of the surface to be measured. 3. The inner shape of the hole is measured by inserting the stylus into the hole, vibrating in the radial direction of the hole and moving the probe in the longitudinal direction. Item 3. The surface shape measuring method according to item 1 or 2. 4. A stylus vibrating device for vibrating a stylus at a constant amplitude, and a center of vibration of the stylus is relatively moved along a predetermined path substantially parallel to a surface to be measured, and the amount of movement is set to A moving device that outputs, a conduction time detection circuit that applies a voltage between the stylus and the surface to be measured, and detects an electric conduction time due to the contact thereof, An arithmetic unit for calculating a distance from the vibration center of the stylus to the surface to be measured at that time based on a ratio to a vibration period; and a relative movement amount which is then output from the moving device based on the calculated distance. And a recording device for recording together with the information. 5. A stylus vibrating device for vibrating a stylus with a constant amplitude, and a first means for relatively moving a center of vibration of the stylus in a direction substantially parallel to a surface to be measured and outputting a moving amount thereof. A moving device that changes the distance between the center of vibration of the stylus and the surface to be measured, and outputs the amount of change, and a voltage between the stylus and the surface to be measured. A conduction time detection circuit that detects the electrical conduction time due to the contact between the contact points, an arithmetic device that calculates the ratio between the detected conduction time and the vibration cycle of the stylus, and the ratio becomes constant. A surface shape measuring device comprising: a driving circuit for driving the second moving device as described above; and a recording device for recording output values of the first and second moving devices at that time. 6. The surface shape measuring device according to claim 4, further comprising a rotation mechanism that can rotate the stylus relatively to the measurement target surface.