JPS62105440A - Oscillation type stage device - Google Patents

Abstract

PURPOSE:To assure the oscillation with high oscillation level and amplitude by a small piezoelectric actuator and a small power supply by a method wherein an oscillation stage with mass and spring constant corresponding to the stage oscillation as a target of natural oscillation is utilized. CONSTITUTION:A piezoelectric actuator 38 impressed with AC high voltage from an AC high voltage power supply is expanded and contracted to reciprocate a stage 37. When the piezoelectric actuator 38 is driven at the resonance frequency decided by the mass of stage 37 and the spring constant, a large amplitude of stage which can not be obtained in the non-resonance state can be assured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention holds a stage with a leaf spring by means of a tension rope, and drives the stage simultaneously with the motor to vibrate. J, Unishik relates to IAG type storage device.

[Conventional technology]

Recently, there has been a growing need for high-resolution observation of defect structures on the surfaces of semiconductors such as Si and QaAs, high-density sintered bodies such as silicon nitride and silicon carbide, glass, and various metals in minute regions. It's coming. For example, semiconductor devices made of Si, QaAs, etc. have recently become more and more highly integrated, and even the slightest defect can lead to device failure, reducing yields. Need 1'l or high J.

In order to reduce the number of device failures due to the above defects and prevent deterioration of yield, it is necessary to enhance the inspection contents in the previous process, reject defective materials, and proceed with the modification of the starting materials.
In this process as well, care must be taken to sort out and remove defective materials so that defective materials are not used again. There are various defects on the surface of the f wafer, one of which is -1ag
There is a surface defect called e.

This defect is said to be minute irregularities of 0.5 to 2 nm. Conventionally, there has been no measuring means that can accurately detect this surface defect called l-1age. For this reason, it has relied exclusively on visual inspection by skilled personnel. However, since the above-mentioned inspection is performed manually, inspection errors are likely to occur, and since the inspection is a 100% check inspection, it requires a large amount of man-hours and labor.

By the way, the above-mentioned unevenness can be solved by focus i! using the critical angle method. There is a way to check using signals. According to this means, other means such as mirror interferometry using optical phase measurement, means using surface acoustic waves to detect the phase of surface occlusion light of 0th and 1st order light, or capacitance focus information are used. The f1 type has a feature that it has especially excellent lateral resolution compared to other methods, and its accuracy can be improved to 0.1 tim or less.

However, in order to put the above means into practical use as a measuring device,
For example, either an optical head such as a C-11 Beams 1 Yana or a stage with a sample scanned by moving one side in the XY direction in a horizontal plane with an accuracy of 0.11+ m or less in one evening. There is a need.

The purpose of this movement in the X and Y directions is to obtain one surface profile image. Therefore, the optical head or stage must be moved at high speed. In other words, it is necessary to vibrate at a constant frequency and at high speed. Note that moving the optical head causes unnecessary vibrations such as bending vibrations of the arm portion supporting the optical head, so the stage movement method is preferable.

Figure 8 shows t[constant frequency high 3! FIG. 3 is a diagram showing bJ and U when the wafer is vibrated and the top of the wafer is fixed. Into the figure
m, and the interval Lλ of the horizontal scanning lines 110 is 1-λ-〇, 1 tan, then the number of water instep running lines 11 is -F)-B/Lλ-100pn110.1pm=1000. For example, if vibration is made in the X direction at a frequency of 1 kHz, one screen will be formed in one second if no retrace is used.

Conventionally, stepping motors and D
D motors have been used.

However, due to its poor accuracy, piezoelectric actuators capable of highly accurate vibration drive have recently been used.

[Problem that the invention seeks to solve]

However, the vibration stage using the piezoelectric actuator as a drive source also has the following problems. Generally, the weight of the stage is quite large, so the resonant frequency determined by the weight of the stage and the spring constant of the vibration system is usually about 100 Hz at most. Therefore, it takes 10 seconds to obtain the profile of one screen. For this reason, a vibration actuator of about 100H2 is used in the X direction, and 7 actuators with a displacement of about 100H2 per 10 seconds are used in the Y direction. As a result, one profile is formed in 10 seconds.

However, the above bu[''Tsuno Ino 1 River, 1, I'),
If the surface direction accuracy of l put is 4 (゛, -2 accuracy is low i!lr?), then accordingly (
f11 Horn Phil formation 11. What you can do to shorten the % interval is
8.) C゛b <r1゜51 of the surface profile inspection device, the number 11z = - several hundred) At the frequency of 12, the number i, ', i Tsunomm (1) The displacement is 7
In order to realize the actual value using Kubu-Yueta, the number of laminated piezoelectric actuators must be increased. It is necessary to

However, when the number of laminated sheets is increased, the drive system (C) becomes larger and the drive system becomes larger. It is difficult to realize this, as there are problems such as the large-capacity version of 4 & Ryo.

Also, there is a problem of stabilizing the amplitude of the vibration strip.

If this point is not resolved, image distortion such as screen leakage will occur, reducing the accuracy of surface blower inspection.

Therefore, the present invention has been developed to provide a compact El'den)
An object of the present invention is to provide a vibrating stage device that can obtain vibrations having a required human-like frequency and amplitude using a compact power supply. Another object of the present invention is to provide a vibrating stage device that can always produce vibrations with stable amplitude. Another object of the present invention is to provide a vibrating stage device that can always apply an AC high voltage having a frequency matching the resonant frequency of the vibrating stage to an actuator.

[Means to solve problems]

The present invention has taken the following measures to solve the above problems and achieve the object.

(1) Natural frequency matches target stage frequency -
A vibration stage having a stage width and a spring constant selected as shown in FIG. 46 is provided, and a piezoelectric actuator is provided to provide a driving force for vibration to the vibration stage. Then, an AC voltage having a frequency equal to the natural frequency of the vibration stage is applied to this piezoelectric actuator. Note that it is desirable that the piezoelectric actuator be coupled to a vibrating stage or a stage fixing base via a spring member.

(2) Set the piezoelectric actuator to 8 to increase the driving force for vibration stage vibration.
A sensor is provided to detect the vibration of the vibration stage which vibrates in response to the vibration driving force given by the vibration drive force. A comparator is set up to compare the amplitude of the output signal of this sensor and the output M quasi-voltage of the constant voltage sensor and send out the difference output. A high voltage power source is provided that applies a drive voltage to the piezoelectric actuator according to the differential output.

(3) Provide a phase difference detector that compares the phase of the output 18 of the sensor with the phase of the oscillation output signal and sends out a phase difference output, and oscillates based on the phase difference output from this phase difference detector. An oscillator is provided that changes the frequency and supplies its oscillation output signal to the phase difference detector as a comparison input, and this 5F applies a driving voltage to the piezoelectric actuator according to the oscillation output signal of the oscillator. A high-voltage power source will be provided. (1
j. The sensor is preferably a piezoelectric element with a bimorph structure.

[Effect]

Since the IE electric actuator is driven at its natural frequency, the vibration stage vibrates with a displacement larger than the vibration displacement of the actuator itself.

In other words, at a specific resonance frequency, the minute vibrations of the actuator are magnified to obtain a large amplitude proportional to the Q of the resonance system, which can greatly contribute to expanding the profile screen size and increasing speed.

In addition, the X of the vibration stage is constantly detected by a sensor.
The actuator drive voltage is controlled so that the amount of vibration change in the Yh direction, that is, the detection signal amplitude always shows the same value.

Further, in accordance with the vibration frequency detected by the sensor, the AC frequency of the AC high voltage power supply for vibration driving follows the natural resonant frequency of the vibration stage with high accuracy.

The resonant frequency of a vibration stage is determined by the weight and spring constant of the stage, or by the effects of changes in the elastic constant of the spring used due to changes in ambient temperature, etc., and also by the effects of changes in the elastic constant of the spring used when an object is placed on the stage. Weight may change the resonant frequency. At this time, if there is a difference between the AC frequency applied to the actuators (1) and (2), sufficient vibration may not be obtained. However, since the resonant frequency of the stage is always detected and a high-voltage AC voltage having a frequency that follows this is applied to the actuator, stable vibration is produced.

〔Example〕

FIG. 1 is a plan view showing a first embodiment of the present invention. In FIG. 1, spring fixing parts 11 to 14 are installed on the base 10, which has a large vibration isolation effect, and both ends of the leaf spring 15 are fixed by the fixing parts 11 and 12.
．． [Both ends of the leaf spring 16 are fixed by 'l/l. s' of the pair of leaf springs 15 and 16 arranged opposite to each other.
Both ends of the Y-direction vibration stage 17 are inspected at the center part 5 part 1
7a and 17b are supported. Thus, Y 71j
The plane vibration stage 17 is elastically supported so as to be movable in the Y direction.

The displacement end of the piezoelectric actuator 18 is in contact with the end of the support part 17b of the vibration stage 17, which is connected to the plate spring 16. It is fixed by a fixing part 19 installed on the table.A displacement sensor 20 made of a bimorph type piezoelectric element is attached to one side of the leaf spring 15.Displacement sensor 20 made of this bimorph type piezoelectric element Compared to other sensors, the sensor has advantages such as being more compact in size, has a larger dynamic range, and has a better frequency response.

However, when driving at a frequency near or below 100 Hz, the output impedance is large, so the impedance conversion preamplifier 21 is placed near the displacement sensor 20. In this way, the output signal from the displacement sensor 20 is supplied from the terminal 22 through the impedance conversion preamplifier 21 to a displacement amount monitor and a control system for stable vibration.

On the Y-direction vibration stage 17, an X-direction vibration stage is provided using the vibration stage 17 as a base.

FIG. 2 is a plan view of the apparatus shown in FIG. 1, showing only the X-direction vibration stage with an oil outlet. As shown in FIG. 2, the X-direction vibration stage has the same configuration as the Y-direction vibration stage.

That is, on the Y-direction vibration stage 17 as a base,
Spring fixing parts 31 to 34 are installed, and the fixing part 31.
Both ends of a plate spring 35 are fixed to J: 32, and both ends of a plate spring 36 are fixed by a fixing portion 33.3/I. The pair of oppositely arranged leaf springs 35 and 36 are connected to the middle heat section of the X-direction vibration stage 37 at both ends of the support section 37 (],
37b is supported and held so as to be movable in the X direction. Vibration stage 3 coupled to the leaf spring 36
The displacement end of the laminated piezoelectric actuator 3B is in contact with the end of the support portion 37b. The base end of this laminated piezoelectric actuator 38 is fixed by a fixing part 39 installed on the Y-direction vibration stage 17. A displacement sensor 40 made of a bimorph piezoelectric element is attached to one side of the leaf spring 35. An impedance conversion preamplifier 41 is arranged near the displacement sensor 40, and the output signal from the displacement sensor 4o is passed through the impedance conversion preamplifier 41 to a terminal 42 to monitor the amount of displacement and to a control system for stable vibration. It will be supplied to

FIG. 3 is a schematic diagram of FIG. 2. Now, when an AC high voltage is applied to the piezoelectric actuator 38 by the AC high voltage power supply, the piezoelectric actuator 38 expands and contracts, and the stage reciprocates accordingly. When the piezoelectric actuator 38 is driven at a resonant frequency determined by the mass and spring constant of the stage 37, a large amplitude of the stage that cannot be obtained in a non-resonant state is observed. According to the results of experiments conducted by the present inventors, in the non-resonant state, only an amplitude of about 20 - can be obtained, whereas in the resonant state, although the piezoelectric actuator itself has an amplitude of 20 tur+, the stage 37 It was confirmed that an amplitude of about 50IIfn was generated.

FIG. 4 is a block diagram showing the configuration of the control system.

Although FIG. 4 shows only the vibration control system in one direction, for example, the Xh direction, the vibration control system in the Y/J directions is constructed in the same manner. As shown in FIG. 4, when an AC high voltage is applied to the alterator 38 from the AC high voltage power supply 43, vibration is excited.

The alternating current frequency in this case is a frequency that matches the resonant frequency determined by the vibration strip 37 and the spring constant. 13. In the vibrating stage device configured as shown in FIGS. 1 and 2, the weight of the stage 37 and the leaf spring 3
5.36 For adjusting the abrasive quality and how to apply tension to the leaf spring, etc., the resonant frequency of the stage 37 is from several Hz to several tens of Hz.
The frequency will be approximately 0Hz.

However, this resonant frequency is related to the X-horn plane vibration stage. In the YIj-direction vibration stage, the resonance frequency is calculated by adding the weight of the white of the eye, which takes into account the weight of the X-direction vibration stage mounted above it. However, the vibration of the stage in the Y direction from 4K is the 8th
When scanning as shown in the figure, a very slow swing lI
J roar, for example, a displacement of 100 houses in the Y direction takes several seconds to several tens of seconds.
It will take about seconds. Therefore, the frequency of the Y-direction vibration stage that is actually used is considerably lower than the resonance frequency of the X-direction vibration stage.

However, the necessity to monitor displacement in the Y direction and use the signal to accurately control the movement period of the Y-direction vibration stage is exactly the same as in the case of the X-direction. however,
As a sensor for monitoring displacement in the Y direction, it is preferable to use a highly accurate integral sensor, dual potentiometer, or capacitive sensor, rather than a piezoelectric element, which is a differential sensor.

In FIG. 4, a displacement sensor consisting of a piezoelectric element 4.
The output of 0 is amplified by an amplifier 41, and the peak value of the AC waveform is sent to a peak hold circuit 44 in bold at regular intervals. This hold value is compared with the reference voltage output from the constant voltage generator 45 in a comparator 46, and a difference output is sent out. A voltage proportional to this differential output is superimposed on the voltage of the high voltage power supply 43, and this is applied to the actuator. Using the above-mentioned path as one feedback loop, the electric power is controlled so that the axes between the small ship and the reference voltage L1- become zero. Regarding the Y direction, the reference voltage (1) can be output according to the specified time period -1. In this way, the circuit shown in FIG. 4 can stabilize the amplitude of the "C" stage when the voltage is applied.

Next, other embodiments of the present invention will be described.

FIG. 5 is a diagram showing a second embodiment of the present invention, and shows a qi surface corresponding to FIG. The second embodiment shown in FIG. 5 differs from the first embodiment in that an elastic member 50 made of, for example, a leaf spring or a coil spring is interposed between the piezoelectric actuator 38 and the vibration stage 37. 1!
/, : is a point. FIG. 6 is a schematic diagram of FIG. 5.

In this embodiment configured as above, since the elastic member is interposed between the piezoelectric actuator 3 and the vibration stage 37, even when the piezoelectric actuator 38 approaches the vibration point, 3. The contact surface with the vibration stage 37 does not separate. 3. Therefore, the vibration stage 37 vibrates smoothly, the vibration waveform becomes clean, and a large amplitude can be obtained without any amplitude restriction. In other words, the above-mentioned Without the elastic member, the piezoelectric actuator 38 and the vibration stage 37 would be in direct contact with each other, so that the contact surfaces may momentarily separate when approaching the resonance point.

For this reason, the vibration waveform may be disturbed or the amplitude may be limited, but according to this embodiment, such situations can be avoided. Therefore, it is effective in cases where highly accurate displacement is required. According to the experiments of the present inventors,
In the second embodiment, the displacement of the piezoelectric actuator 38 itself is 201I! It was confirmed that the vibration stage 38 generates an amplitude of 1100u when n. however,
In this second embodiment, care must be taken because the resonant frequency changes due to the intervening elastic member 50.

FIG. 7 is a diagram showing the main parts of the third embodiment of the present invention, and corresponds to FIG. 4. The third embodiment differs from the first embodiment in that, as shown in the figure, a phase difference detector 61 and an oscillator 62 are used to perform frequency control. The output signal of the displacement sensor 40 is amplified by the amplifier 41 and input to the phase difference detector 61. At the same time, an oscillation output signal from the oscillator 62 having a vibration frequency for driving the actuator is input to the phase difference detector 61 . Now, when the phase difference between both signals is zero and stable vibration is being performed, the output from the phase difference detector 61 is O. However, the resonant frequency of the vibration stage 37 is If there is a change in mounting or ambient temperature, etc., a phase difference will occur between the two signals.
This phase difference is detected by the phase difference detector 61 (S
An output corresponding to the phase difference is sent out. When this output is input to the oscillator 62, the frequency of the optical oscillation output signal H of the oscillator 62 changes to match the L oscillation frequency of the vibration stage. In other words, in this embodiment, in J3, the oscillator 62
The output frequency is automatically controlled so that it always matches the resonance frequency of the 11J stage 37.

Note that the present invention is not limited to the above embodiments.

For example, the control system for vibration stabilization may be a combination of the circuit shown in FIG. 4 and the circuit shown in FIG. 7. That is, the amplitude value and the frequency value of the output of the displacement sensor are used together for comprehensive control.

If this is done, the configuration will be slightly more complicated and the cost will be higher than in the previous embodiment, but the vibration of the vibration stage can be made more stable. That is, even if an AC voltage that follows the resonant frequency of the stage is applied, when an object to be tested is placed on the stage, the amplitude may fluctuate due to vibration damping. Furthermore, even if adjustment is performed using the applied voltage, if the Q of the vibration system is large, the change in amplitude may be too large and follow-up by the voltage may be inadequate. Therefore, a means for applying a high voltage power source having an AC frequency following the resonant frequency of the stage, and a means for applying a voltage so that the amplitude detected by the displacement sensor becomes constant (for Jl use, J : The most stable vibration can be obtained.Also, in the above embodiment, a bimorph type piezoelectric element was used as a displacement sensor, but a capacitance sensor, light 7],
Ivarl! You can also use ``nli,'' etc. Further, in the above embodiment, the elastic member 50 is interposed between the piezoelectric actuator 38 and the vibration stage 37, but the IJ may be interposed between the piezoelectric actuator 38 and the base 10. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

[Efficacy of invention Song Dynasty]

As described above, the present invention can provide a vibrating stage device that can generate vibrations with a required large frequency and amplitude using a small piezoelectric actuator and a small piezoelectric actuator. Further, it is possible to provide a vibrating stage device that can always obtain vibrations with stable amplitude. Furthermore, it is possible to provide a vibrating stage device that can always apply an AC high voltage having a frequency that matches the resonant frequency of the vibrating stage to the actuator.

[Brief explanation of drawings]

1 to 4 are diagrams showing a first embodiment of the present invention, FIG. 1 is a plan view showing the overall structure of the mechanical part of the vibration stage device, and FIG. 2 is a plan view of the X-direction vibration stage. 3 is a schematic diagram of FIG. 2, and FIG. 4 is a block diagram showing the configuration of a control system having vibration stabilizing means. 5 and 6 are diagrams showing a second embodiment of the present invention. FIG. 5 is a plan view showing the configuration of the main part, FIG. 6 is a schematic diagram of FIG. 5, and FIG. 7 is a main part of the main part. FIG. 3 is a block diagram showing the configuration of main parts of a third embodiment of the invention. FIG. 8 is a diagram for explaining the problems of the prior art. 10... Base, 11-14. 31-34... Spring fixing part, 15, 16. 35. 36... Leaf spring, 17...
・Y direction vibration stage, 37... X direction vibration stage, 18.38... Piezoelectric actuator, 19.39.
・Fixed part, 20.40 ・Displacement sensor, 21.41
・・・Preamplifier for impedance conversion, 22.42・
...Terminal, 50...Elastic member. Applicant's agent Patent attorney Atsushi Tsuboi W&1 Figure 4 Figure 2 Figure 6 Figure 7 Figure 8

Claims (5)

[Claims] (1) A vibration stage whose mass and spring constant are selected so that the natural frequency matches the target stage vibration frequency, a piezoelectric actuator provided to give vibration driving force to this vibration stage, and this piezoelectric A vibrating stage device comprising means for applying an alternating current voltage having a frequency equal to the natural frequency of the vibrating stage to an actuator. (2) The vibrating stage device according to claim 1, wherein the piezoelectric actuator is coupled to the vibrating stage and/or the stage base via a spring member. (3) A vibration stage, a piezoelectric actuator provided to apply a vibration driving force to the vibration stage, and a sensor that detects the amount of change in vibration of the vibration stage that vibrates due to the vibration driving force applied by the piezoelectric actuator. , a comparator that compares the amplitude of the output signal of this sensor with a reference voltage output from the constant voltage generator and sends out a difference output; and a drive voltage corresponding to the difference output output from this comparator to the piezoelectric generator. A vibrating stage device characterized by comprising a high voltage power supply applied to an actuator. (4) A vibration stage, a piezoelectric actuator provided to apply a vibration driving force to the vibration stage, and detecting the amount of change in vibration of the vibration stage vibrated by the vibration driving force applied by the piezoelectric actuator. A sensor, a phase difference detector that compares the phase of the output signal of this sensor with the phase of the oscillation output signal and sends out a phase difference output, and changes the oscillation frequency based on the phase difference output from this phase difference detector. oscillator that supplies an oscillation output signal to the phase difference detector as a comparison input; and a high-voltage power supply that applies a drive voltage to the piezoelectric actuator according to the oscillation output signal of the oscillator. stage equipment. (5) The vibrating stage device according to claim 3 or 4, wherein the sensor is a piezoelectric element having a bimorph structure.