KR100270365B1 - High Speed Scanning Interferometer System - Google Patents

Abstract

A laser oscillator for generating a laser beam of a predetermined wavelength and a portion of the laser beam scanned from the laser oscillator so that the thickness of the thin film and the surface roughness can be measured at high speed by scanning the laser onto a panel and counting the number of interference fringes. An acoustic optical modulator that modulates a frequency, a reference light detector that detects a portion of the laser beam modulated by the acoustic optical modulator, as a reference light, and scans the rest of the laser beam modulated by the acoustic optical modulator into a measuring object mounted on a table An optical system for advancing as much as possible, a reflected light detecting device for detecting a laser beam reflected by the measurement object, a transmitted light detecting device for detecting a laser beam passing through the measurement object, and a reference light detecting device, a reflected light detecting device or a transmitted light detecting device The measured signal and count the interference fringes The present invention provides a high-speed scanning interferometer system including a data processing device for determining a device.

The optical system is a combination of a focusing lens, a scanning mirror rotating at high speed, a circumferential lens, and a flat mirror, and the reference light detector, the reflected light detector, and the transmitted light detector are made of a high speed photodiode with a fast response time. Is performed using a PROM or the like having a counting speed of 5 MHz or more.

Description

High Speed Scanning Interferometer System

The present invention relates to a high speed scanning interferometer system, and more particularly, to a high speed scanning interferometer system capable of measuring the thickness and surface roughness of a thin film at high speed by scanning a laser.

Generally, the fringe of equal chromatic order based on the principle of interference, in order to measure the thickness and surface roughness, which is a very important factor in the design and manufacture of optical components, wafers, glass products, thin films, etc. Fizeau interferometry is applied.

The orange pattern order and the interference interference method described above are suitable for measuring the surface roughness of the optical component and the thickness of the thin film.

In addition, holography and moire patterns are often applied to measure the change of coarse surface, and light scattering, stereoscopic microscope, and styling apparatus are applied to measure surface roughness smaller than 10 nm.

As described above, various conventional techniques can be achieved with accuracy in precise measurement of the thickness and surface roughness of a thin film in a laboratory or a laboratory having sufficient time and space.

However, since the manufacturing process of a product such as a flat panel display used in a notebook computer is very complicated, and each manufacturing process is performed at a high speed (within 15 seconds), the conventional technique as described above is used in the field (for example, It is impossible to measure the thickness and surface roughness of the panel).

That is, it takes more than one hour to measure the thickness and surface roughness of the glass panel (600 mm x 750 mm and 470 mm x 480 mm), which are used in flat panel display devices, by conventional techniques. It is not possible to measure the thickness or the surface roughness of the glass panel using the prior art in the manufacturing process proceeds at high speed.

Thus, until now, several samples are randomly taken and measured in the laboratory in order to control quality and select defective parts in the manufacturing process of products such as flat panel displays.

As described above, it is impossible to inspect defects of all parts in the manufacturing process that proceeds at a high speed, and thus, it is necessary to take a lot of time to find defects because inspection is performed by an arbitrary sampling method. When a defect is found, a large amount of parts are already moved through the process to the next process, resulting in high defect rates and waste of material.

In particular, the glass panel for manufacturing a display device used for a large screen, such as a PDP, because the size is large, it takes more time to measure, the cost of defects increases significantly.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-speed scanning interferometer system capable of measuring the thickness and surface roughness of a thin film at high speed by scanning a laser on a panel and counting the number of interference fringes. .

The high-speed scanning interferometer system of the present invention modulates a frequency of a part of the laser beam scanned from the laser oscillator through an acoustic optical modulator, detects a part of the modulated laser beam as reference light, and detects the remaining modulated laser beam as a focus lens and a scanning mirror. And an optical system made by combining a circumferential lens and a planar mirror to scan a measurement object through a predetermined optical path, and detect reflected light reflected from the measurement object and transmitted light passing through the measurement object, respectively, and mix with the reference light. The thickness of the workpiece and the surface roughness are measured by counting the number of interference fringes that occur.

In addition, the high-speed scanning interferometer system of the present invention includes a laser oscillator for generating a laser beam of a predetermined wavelength, an acoustic optical modulator for modulating a frequency of a portion of the laser beam scanned from the laser oscillator, and a modulated through the acoustic optical modulator. A reference light detection device for detecting a part of the laser beam as a reference light, an optical system for advancing the rest of the laser beam modulated by the acoustic optical modulator to be scanned into a measurement object mounted on a table, and a laser beam hit by the measurement object and being reflected A reflected light detecting device for detecting a light beam, a transmitted light detecting device for detecting a laser beam passing through a measurement object, and a signal detected from the reference light detecting device and the reflected light detecting device or a transmitted light detecting device as described above, and counting an interference fringe to And a data processing device for determining thickness or surface roughness.

The optical system is formed by combining a focus lens, a scanning mirror, a circumferential lens, a flat mirror, and the like, and the scanning mirror is installed to rotate at a predetermined speed.

The scanning mirror is made of a polygonal rotating mirror that rotates at a high speed (about 15,000 rpm or more).

The reference photodetector, the reflected photodetector, and the transmitted photodetector are made of a high speed photodiode with a fast response time, and the data processor is made of a PROM having a counting speed of 5 MHz or more.

According to the high-speed scanning interferometer system of the present invention made as described above, the thickness and the surface roughness are measured by counting the number of interference fringes by the phase difference between the reference light and the reflected light or transmitted light using a laser having coherence. It is possible to measure with the accuracy that corresponds to the wavelength of the laser, and because the measurement speed is fast, it is necessary to scan the whole surface of one panel according to the rotation speed of the scanning mirror, the selection of the high speed photodiode and the speed of the data processing device. It is possible to keep the time less than the time required for each manufacturing process, so that the entire inspection of the product is possible.

1 is a block diagram schematically showing one embodiment of a high speed scanning interferometer system according to the present invention;

Figure 2 is a side view schematically showing one embodiment of a high speed scanning interferometer system according to the present invention.

3 is a block diagram schematically showing one embodiment of a data processing apparatus according to the present invention;

4 is a flow chart showing a first mode of operation in one embodiment of a high speed scanning interferometer system in accordance with the present invention.

5 is a flow chart showing a second mode of operation in one embodiment of a high speed scanning interferometer system in accordance with the present invention.

6 is a plan view of a workpiece for explaining a state of scanning the workpiece by one embodiment of a high speed scanning interferometer system according to the present invention.

7 is a graph showing the relationship between the spot size and the equiphase plane with respect to the distance from the beam waist.

Fig. 8 is a graph showing the relationship between the laser beam transmission distance and the spot size when the focal length is 70 cm.

Fig. 9 is a graph showing the relationship between the laser beam transmission distance and the spot size when the focal length is 135 cm.

10 is a graph showing a relationship between a laser beam transmission distance and a beam waist spot size according to an embodiment of the high speed scanning interferometer system according to the present invention.

Next, the most preferred embodiment of the fast scanning interferometer system according to the present invention will be described in detail with reference to the drawings.

First, as shown in Figs. 1 and 2, one embodiment of the high-speed scanning interferometer system according to the present invention is a laser oscillator 2 for oscillating and outputting a laser beam of a predetermined wavelength and the output from the laser oscillator 2 described above. An acoustic optical modulator 4 for modulating or unmodulating the laser beam, and a reference light detecting device 10 for detecting a portion of the laser beam modulated by the acoustic optical modulator 4 as reference light And an optical system 20 which proceeds to scan the remainder of the laser beam modulated by the acoustooptic modulator 4 into the measurement object 7 loaded on the table 6, and hits the measurement object 7 with reflection. Reflected light detector 30 for detecting a laser beam to be detected, a transmitted light detector 40 for detecting a laser beam passing through the measurement object 7, the reference light detector 10 and the reflected light detector 30 described above Or the signal detected from the transmitted light detector 40 And a data processing device 50 for comparing and counting interference fringes to determine the thickness or surface roughness of the workpiece.

The laser oscillator 2 is preferably configured to oscillate and output a HeNe laser having a wavelength of 633 nm, which transmits a glass material (SiO 2) well and exhibits easy red color.

In the above, the laser oscillator 2 has been described as being configured to oscillate a laser of 633 nm wavelength, but the present invention is not limited thereto, and it is possible to use lasers of various wavelengths, and it is suitable according to the wavelength of the laser to be oscillated. It is preferable to select an apparatus suitable for the acoustic optical modulator 4, the reference light detector 10, the reflected light detector 30, the transmitted light detector 40, and the data processor 50 according to the wavelength of the laser.

The laser oscillator 2 is configured to operate in a single mode of TE mode (transverse electric mode) or TM mode (transverse magnetic mode) having polarization, and the power level ranges from 10 to 20 GHz continuous wave (CW). It is preferable to set it as.

The acoustooptic modulator 4 modulates a frequency of a part of the laser beam output from the laser oscillator 2 by applying an ultrasonic wave with varying intensity, and controls a control voltage to shift a modulated signal ( You can adjust the ratio between shift and unshift.

The acoustic optical modulator 4 is designed to correspond to a wavelength of 633 nm when the laser oscillator 2 is selected to oscillate a HeNe laser having a wavelength of 633 nm, and modulates the divergence angle of the laser beam. It is preferable to control at 6.5 ° to facilitate separation between and unmodulated signals.

The optical system 20 is formed by combining a focus lens 21, a scanning mirror 22, a circumferential lens 23, a flat mirror 24, and the like.

The optical system 20 is a modulated beam expander 25 and an unmodulated beam output from the laser oscillator 2 to enlarge a diameter of a laser beam that is modulated or unmodulated and radiated by the acoustic optical modulator 4. It further includes an enlarger 95.

In the modulated beam expander 25 and the non-modulated beam expander 95, the laser beam emitted by being modulated or unmodulated is enlarged so that the beam waist becomes 0.75 cm.

In general, it is known that the spatial resolution of measurement is closely related to the transmission of the laser beam, and Gaussian optics is effectively applied in the paraxial region.

According to Gaussian optics, the intensity (I) of the laser beam is given by Equation 1 below, and the relationship between the spot size and the equiphase surfaces for the distance z from the beam waist is shown in FIG. Same as

Where I is the laser beam intensity, I ₀ is the maximum intensity of the laser beam (intensity at the beam waist), u is the radius from the axis, and ω is the spot size of the laser beam.

When the laser beam is enlarged, such as transmission through the space, the spot size of the laser beam ω relative to the distance z from the beam waist is given by Equation 2 below, and the radius of curvature of the laser beam R is Is given by Equation 3 below, and the divergence angle θ of the laser beam is given by Equation 4 below.

Ω ₀ is the spot size in the beam waist, and λ is the wavelength of the laser beam.

Therefore, it can be seen that the divergence (enlargement) of the laser beam is proportional to the wavelength (λ) of the laser beam and inversely proportional to the spot size (ω) of the laser beam. Therefore, this applies to the design of the beam enlarger 25 described above.

In addition, in order to obtain the best spatial resolution, it is desirable to arrange the measurement object 7 at the focal point when the spot size ω of the laser beam is minimum.

In FIG. 8, the optical system is installed so that the focal length is 70 cm, and the spot size of the beam waist (ω ₀ ) is changed to 0.25 cm, 0.50 cm, 0.75 cm, and 1.00 cm. The spot size is measured and shown in a graph. In FIG. 9, an optical system is installed so that the focal length is 135 cm, and the spot size (ω ₀ ) of the beam waist is varied by 0.25 cm, 0.50 cm, 0.75 cm, and 1.00 cm in each case. The spot size of the laser beam is measured and plotted against the transmission distance.

It can be seen from FIG. 8 that when the focal length is 70 cm and the spot size (ω ₀ ) of the beam waist is 1.00 cm, the spot size at the focus is the smallest as 20 μm, and from FIG. 9 the focal length is 135 cm and the beam It can be seen that the spot size at the focal point is the smallest at 40 mu m when the spot size ω ₀ of the waist is 1.00 cm.

However, in the case of beam spot size (ω ₀₎ is 1.00㎝ waist, the spot size (ω ₀₎ of the beam waist in order to control the size of the spot stably due to the change of the spot size (the inclination of the graph), the size 0.75㎝ It is desirable to design as possible.

Therefore, the modulated beam expander 25 and the non-modulated beam expander 95 are formed so as to enlarge the laser beam emitted from the acoustic optical modulator 4 so that the spot size ω ₀ of the beam waist becomes 0.75 cm. It is desirable to.

The scanning mirror 22 of the optical system 20 is installed to rotate at a predetermined speed.

The scanning mirror 22 is composed of a polygonal rotating mirror that rotates at a high speed (about 15,000 rpm or more).

The circumferential lens 23 uses a lens having a focal length of 35 cm, for example, and the flat mirror 24 has a reflecting mirror having a plan view smaller than 1/4 of the laser beam wavelength λ, for example. Use

The planar mirror 24 changes the path of the laser beam transmitted through the cylindrical lens 23 so that the laser beam is scanned on the measurement object 7 mounted on the table 6. Install it.

The optical system 20 further includes a modulated optical cable 26 made of an optical fiber for transmitting the laser beam, which is enlarged and transmitted from the modulated beam expander 25, to a predetermined position.

In addition, the optical system 20 includes a modulation beam splitter 27 for changing a part of the laser beam transmitted through the modulation optical cable 26 to the reference light detecting device 10, and the modulation optical cable 26. It further includes a reflection mirror 28 for changing the path of the rest of the laser beam transmitted through the modulated beam splitter 27 to the focus lens 21.

Therefore, the laser beam oscillated from the laser oscillator 2 is modulated by the acoustic optical modulator 4, and a part of the laser beam transmitted through the modulated beam expander 25 and the modulated optical cable 26 is It is separated from one modulation beam splitter 27 and proceeds to the reference photodetector 10 described above, and the rest of the path is changed in the reflection mirror 28 to proceed to the focus lens 21.

The laser beam focused by the focusing lens 21 and focused on the scanning mirror 22 is scanned while the polygonal scanning mirror 22 is rotated to change its position, and the cylindrical lens 23 is scanned. As it passes through, it is converted into a parallel beam, and the path is changed by the plane mirror 24 described above, and scanned on the workpiece 7 loaded on the table 6.

The reference light detecting apparatus 10 includes a reference light detecting sensor 12 for detecting a laser beam whose traveling path is changed by the modulation beam splitter 27, and a traveling path by the modulation beam splitter 27. And a reference splitter 18 for separating and advancing the laser beam, which is a reference light to be advanced, in two directions opposite to the reference light detection sensor 12 and the reference splitter 18 described above by the reference splitter 18. And a reference light focusing lens 19 for focusing the laser beam, which is the reference light separated by the side toward the reference light detection sensor 12.

The reference photodetector 12 described above uses a high speed photodiode with good spatial response and a very fast response time of about 2 nsec.

Preferably, the detection area of the reference light detection sensor 12 is formed to be about 5,1 mm 2 wide so that the laser beam does not need to be precisely focused.

The reflected light detecting device 30 includes a reflected light detecting sensor for detecting a laser beam that is reflected light reflected from the surface of the measuring object 7 among the laser beams scanned on the measuring object 7 loaded on the table 6. 32), a reflected light splitter 35 for selecting a laser beam, which is reflected light reflected from the surface of the measurement object 7, and changing the path of the laser beam to the reflected light detection sensor 32; and the reflected light splitter 35. Reflected light circumferential lens 34 for focusing the reflected light proceeds by changing the path toward the reflected light detection sensor 32 by the reflected light, and reflected light for transmitting the reflected light carried by the reflected light circumferential lens 34 to a predetermined position The reflected light is obtained by mixing the cable 36 and the reference light separated by the reference splitter 18 from the opposite side of the reference light detection sensor 12 and the reflected light transmitted through the reflected light cable 36. And the reflected light mixer (38) to push forward towards the output sensor 32, a reflected light focusing lens 39 for focusing the laser beam reflected by the said one sensor (32) mixed in the above-mentioned reflected light mixer (38).

The reference light, which is separated from the reference light detection sensor 12 by the reference splitter 18 and moves forward, is changed through the one or more reflection mirrors 28 and proceeds to the reflected light mixer 38.

In the reflected light mixer 38, the laser beam oscillated by the laser oscillator 2 and unmodulated by the acoustic optical device 4 is transmitted through a predetermined path, mixed with the reference light and the reflected light, and mixed. The laser beam is detected through the above-described reflected light detection sensor 32.

The laser beam unmodulated in the acoustic optical device 4 is enlarged in the beam expander 25, is reflected in a predetermined path through one or more reflection mirrors 95, and through the non-modulated optical cable 96 It is transmitted to a predetermined position, and divided into two directions through the unmodulated beam splitter 97, and proceeds to the above-described reflected light detecting device 30 and transmitted light detecting device 40, respectively.

The reflection light detection sensor 32 can be implemented in the same configuration as the reference light detection sensor 12 described above, and the reflection light circumferential lens 34 is implemented in the same configuration as the above-mentioned circumferential lens 23. Since the reflective optical cable 36 and the non-modulated optical cable 96 can be implemented in the same configuration as the modulated optical cable 26, detailed description thereof will be omitted.

The transmission light detecting device 40 is a transmission light detection sensor 42 for detecting a laser beam which is transmitted light passing through the measurement object 7 among the laser beams scanned on the measurement object 7 loaded on the table 6. And, through the plane mirror 45 which changes the path of the laser beam, which is transmitted light passing through the measurement object 7, toward the above-mentioned transmitted light detection sensor 42, and detects the transmitted light by the plane mirror 45. A transmission light circumferential lens 44 for focusing the transmitted light traveling by changing the path toward the sensor 42; a transmission light cable 46 for transmitting the transmission light carried by the transmission light circumferential lens 44 to a predetermined position; The reference light splitter 18 mixes the reference light separated by the reference splitter 18 toward the opposite side of the reference light detection sensor 12 and the transmitted light transmitted through the transmitted light cable 46 to the transmitted light detection sensor 42. Transmitted light mixing And a 48 and the transmitted light focus lens 49 for focusing the laser beam is mixed in the above-described transmitted light mixer (48) to said one transmission light detection sensor 42.

The reference light, which is separated from the reference light detection sensor 12 by the reference splitter 18 and proceeds, is partially separated from the reflected light mixer 38, and proceeds to the non-modulated beam splitter 97. The non-modulated laser beam, which is separated and propagated toward one transmitted light detector 40, is mixed in the non-modulated beam splitter 97, and is reflected in a predetermined path through the reflecting mirror 98. The transmitted light mixer 48 Proceed to

Therefore, the laser beam detected by the transmitted light detection sensor 42 is a laser beam in which the reference light, the transmitted light and the unmodulated light are mixed.

The transmitted light detection sensor 42 can be implemented in the same configuration as the reference light detection sensor 12 described above, and the transmitted light circumferential lens 44 is implemented in the same configuration as the circumferential lens 23 described above. The flat mirror 45 can be implemented in the same configuration as the flat mirror 24, and the transmitted optical cable 46 has the same configuration as the modulated optical cable 26. The detailed description is omitted since it is possible to carry out.

10 shows a process in which the spot size ω ₀ of the beam waist is changed when the laser beam is transmitted to the transmitted light detecting device 40.

As shown in Fig. 10, the laser beam is focused through the focus lens 21 so that the spot size ω ₀ of the beam waist is minimized in the workpiece 7, and is expanded again to transmit the above-mentioned transmitted light cable 46 The spot size of the beam waist ω ₀ is minimized in the transmitted light detection sensor 42 through the transmitted light focusing lens 49, which is transmitted through the light transmitting focal length lens (focal length is about 20 cm). Focus as much as possible.

The data processing device 50 is made of PROM or the like having a counting speed of 5 MHz or more.

In the data processing apparatus 50, the reference light detected by the reference light detector 10, the reflected light detected by the reflected light detector 30, and the transmitted light detected by the transmitted light detector 40 are described. The thickness and surface roughness of the workpiece 7 are read by counting the number of interference fringes by using the phase difference which is reflected by or reflected through the workpiece 7 and transmitted through the workpiece 7, respectively.

That is, the surface roughness is read by comparing the reference light with the reflected light, and the thickness is read by comparing the reference light with the transmitted light.

In general, since the laser beam has linearity and coherence, it is widely used for measuring thickness and surface roughness, and the monochromatic light including the laser beam changes in the speed of light when it passes through the measurement medium, which is a transparent medium having a predetermined refractive index. It is known.

The changing speed of the light can be compared with the reference light passing through the air, and can be measured by using a phase difference φ between two changing lights (reference light and measurement light) as shown in Equation 5 below.

Where μ _v is the refractive index of the vacuum and dz (= z _2- z ₁ ) is the path length (or thickness of the workpiece) inside the workpiece 7.

Therefore, μ _v = 1 and the phase difference φ is simply expressed as (1-μ ₀ ) kd when μ ₀ is the average value of the refractive indices in the workpiece 7.

The waveforms of the measurement light (reflected light or transmitted light) and the reference light are shown in Equations 6 and 7, respectively.

x _s = acos (ωt-φ)

x _r = bcosωt

In the above, a and b are constants, x _s is a waveform of measurement light, and x _t is a waveform of reference light.

The detected output (x _s + x _r ) ² is calculated by the square law as shown in Equation 8 below.

a ² cos ² (ωt-φ) + b ² cos ² ωt + ab [cos (ωt-φ) + cosφ]

The waveform of the reflected or transmitted light represented as described above is sensitive to the amplitude change of the waveform expected from the change of the transmitted or transmitted light, and the phase difference φ cannot be distinguished between the difference between the increase and the decrease in thickness. Modulation is performed using the acoustic optical modulator (4).

Therefore, a part of the laser beam is modulated at a frequency of ψ, and the final waveform detected by the reference light detector 10, the reflected light detector 30, or the transmitted light detector 40 is expressed by the following equations (9) and (10). It is represented as

S _s = abcos (ψt + φ)

S _r = a′b′cos (ψt + φ ₀ )

In the above, Ss is the final waveform detected by the reflected light detector 30 or the transmitted light detector 40, and St is the final waveform detected by the reference light detector 10.

In addition, when ψ ₁ = 2k ₁ π and φ + ψ ₂ = 2k ₂ π, zero crossing of S _r and S _s occurs. K ₁ and k ₂ are each 1, 2, 3,. Given by

Therefore, the phase difference φ is expressed by the following equation (11).

φ = ψ ₁ -ψ ₂ + 2π (k ₂ -k ₁ )

In addition, assuming that ψ is a linear function of t, and using the pseudo period τ of the function cosψ, the phase difference φ is expressed by the following equation (12).

Therefore, phase difference (phi) is measured irrespective of amplitude, and the signal of d (phi) / dt is clearly determined by the change of the signal which can be interpreted suitably.

In addition, an embodiment of the high-speed scan interferometer system according to the present invention further includes a display device 60 connected to the data processing device 50 to display the processing result of various data.

The display device 60 includes a liquid crystal display, a cathode ray tube, a fluorescent display, and the like.

The display device 60 is provided with a thickness display device 62 for displaying the measured thickness, a roughness display device 64 for displaying the measured surface roughness, and a reference display device 66 for displaying a standardized reference value, respectively. It is also possible to configure the display device to display all of them in one display device.

The various values processed by the data processing device 50 displayed on the display device 60 are stored in the storage device 68, respectively.

In addition, the data processing device 50 is connected to the reference light detection sensor 12, the reflected light detection sensor 32 and the transmitted light detection sensor 42, and the trigger pulse and the gate pulse are input.

The trigger pulse is a trigger splitter 74 for changing a path to separate a portion of the laser beam scanned through the scan mirror 22 to be used as a trigger light, and a path through the trigger splitter 74. Is detected through a trigger detection device 70 consisting of a trigger focus lens 76 for focusing the changed trigger light and a trigger sensor 72 for detecting the trigger light focused through the trigger focus lens 76. It is input to one data processing device 50.

In addition, the data processing device 50 is connected to a real time signal generator 80 for processing a signal in real time.

A digital-to-analog converter 82 is connected to the real-time signal generator 80, and the signal converted by the digital-to-analog converter 82 is input to the defect search electronic device 84 and processed.

In addition, in one embodiment of the high-speed scanning interferometer system according to the present invention, it is also possible to further install a computer 88 to input, modify or control the required values.

As the computer 88, a general personal computer can be used, and a workstation can be used.

The computer 88 is installed in connection with the defect detection electronic device 84 and the storage device 68.

Next, the measurement process for the thickness and surface roughness of the high-speed scanning interferometer system according to the present invention configured as described above will be described.

First, when the workpiece 7 is loaded on the table 6, the oscillator 2 is oscillated by the laser oscillator 2 and modulated by the acoustic optical modulator 4 and enlarged through the modulated beam expander 25. The laser beam is transmitted through the modulation optical cable 26, the modulation beam splitter 27, and the reflection mirror 28, and the transmitted laser beam is transferred to the scanning mirror 22 by the focus lens 21. Focused

The laser beam focused on the scanning mirror 22 as described above is scanned in a predetermined pattern by the scanning mirror 22 rotating at a high speed.

The laser beam scanned by the scanning mirror 22 is changed into a path through the circumferential lens 23 and the planar mirror 24 and is scanned on the measurement object 7.

As shown in FIG. 6, the laser beam scanned to the workpiece 7 is continuously scanned in the oblique direction at predetermined intervals when the workpiece 7 moves at a predetermined speed.

Therefore, the moving speed of the table 6 on which the workpiece 7 is loaded is set to 5 cm / sec, and the workpiece 7 is 600 mm × 750 mm for manufacturing six panels of 210 mm × 240 mm size. A glass panel having a size of?, And when the rotational speed of the scanning mirror 22, in which the laser beam is the scanning speed, is set to 1 ms, 0.84 sec is required to scan 210 mm.

If the spot size of each measurement value is 50 μm × 50 μm (corresponding to the size of the gate pulse), 4,200 measurement points are calculated per line, and the total number of lines for 240 mm is 4,800. Dog.

In the above-mentioned reference light detecting device 10, reflected light detecting device 30, and transmitted light detecting device 40, using a photodiode operated at 2 nsec, and using a data processing device 50 operating at 5 MHz, 240 mm The time taken to measure is 4.8 sec.

Table 1 shows the time taken to measure panels of 210 mm x 240 mm size and 175 mm x 220 mm size.

Measuring water 210 mm x 240 mm 175 mm x 220 mm Total number of lines 4,800 4,400 Measuring points per line (pcs) 4,200 3,500 Total measurement point (dog) 20.16 × 10 ⁶ 15.4 × 10 ⁶ Measurement speed (5MHz) 0.2 μsec 0.2 μsec Gate pulse 0.84 msec 0.7 msec Total measurement time 4.8 sec 4.2sec

Therefore, as shown in Table 1, when measured using the high-speed scanning interferometer system according to the present invention, the front surface of the glass panel of the size (for example 210mm x 240mm or 175mm x 220mm) used as the display panel The time required to inspect the glass is very short, 4.8 sec and 4.2 sec, and the time required to inspect the 600 mm × 750 mm glass panel to make six 210 mm × 240 mm display panels is also less than 30 sec. Very fast as

Therefore, when two panels are installed in parallel and measured, it takes less than 15 sec to inspect a 600mm × 750mm glass panel to make six 210mm × 240mm display panels.

The reflected light which is scanned at the measurement object 7 at the same speed and reflected by the measurement object 7 is detected by the above-described reflected light detection device 30 and transmitted to the data processing device 50 as described above. 7) The transmitted light passing through 7) is detected through the transmitted light detecting device 40 and transmitted to the data processing device 50.

The data processing device 50 compares the reference light detected by the reference light detector 10 and transmitted with the reflected light and the transmitted light transmitted from the reflected light detector 30 and the transmitted light detector 40 to the phase difference. The interference fringes are counted, the thickness and the surface roughness of the measurement object 7 are calculated from the counted results, and each value is transmitted to the display device 60.

The measurement result transmitted to the display device 60 and displayed is stored in the storage device 68.

The first operation mode, which is a process of detecting the reference light, the reflected light and the transmitted light, comparing the phase difference, calculating the thickness and the surface roughness, and storing the calculated result, is shown in a flowchart in FIG. 4.

On the other hand, the thickness and the surface roughness values calculated from the data processing apparatus 50 are processed in real time through the real-time signal generator 80, and the above-described digital-to-analog converter Search for the converted signal through 62) and if it finds a defect, treat it as a defect.

A second operation mode, which is a process described above, is shown in a flowchart in FIG. 5.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

According to the high-speed scanning interferometer system according to the present invention constructed and operated as described above, it is possible to measure the thickness and surface roughness of the measured object at a very high speed, so that all the products are inspected for all products in the manufacturing process of the display device that proceeds at high speed. It is possible that the defective rate of the finished product is greatly reduced.

In addition, since the defective product can be removed immediately, waste of material is greatly reduced compared to the conventional method in which a predetermined lot is manufactured and then a defect is found and removed.

And the measured value is stored and utilized every time, so it is possible to precisely check the trend of the processing precision of the manufacturing equipment.

Claims (11)

The intensity of the laser beam scanned from the laser oscillator is modulated through an acoustic optical modulator, a portion of the modulated laser beam is detected as reference light, and the remaining modulated laser beam is advanced to a predetermined optical path using an optical system to measure the measured object. High-speed scanning interferometer for scanning and measuring the thickness and surface roughness of the workpiece by detecting the reflected light reflected from the workpiece and the transmitted light passing through the workpiece, and counting the number of interference fringes generated when mixing with the above-mentioned reference light. system. A laser oscillator for oscillating and outputting a laser beam of a predetermined wavelength; an acoustic optical modulator for modulating or unmodulating a laser beam output from the laser oscillator; A reference light detecting device for detecting, an optical system for advancing the rest of the modulated laser beam through the acoustic optical modulator to be scanned into a measuring object loaded on a table, a reflected light detecting device for detecting a laser beam hit by the measuring object and reflected; And comparing the signals detected by the transmitted light detector for detecting the laser beam passing through the measured object with the reference light detector and the reflected light detector or the transmitted light detector, and counting the interference fringe to determine the thickness or surface roughness of the workpiece. A high speed scanning interferometer system comprising a data processing device. 3. The optical system of claim 2, wherein the optical system is a modulated beam enlarger and a non-modulated beam expander for expanding a diameter of a laser beam output from the laser oscillator and modulated or unmodulated and emitted by the acoustic optical modulator, and the modulated beam. Modulation optical cable consisting of an optical fiber for transmitting the laser beam transmitted from the enlarger to a predetermined position, a focus lens for focusing the laser beam transmitted through the above-described modulation optical cable, and scanning of polygons rotating at a predetermined speed A high speed scanning interferometer system comprising a mirror, a cylindrical lens, and a planar mirror that redirects the laser beam to the workpiece. 4. The optical system of claim 3, wherein the optical system includes a modulation beam splitter for changing a part of a laser beam transmitted through the modulation optical cable to a reference light detecting device, and a modulation beam splitter transmitted through the modulation optical cable. And a reflective mirror for redirecting the remainder of the laser beam that has passed through to the focal lens. 5. The apparatus of claim 4, wherein the reference light detecting device comprises a reference light detecting sensor comprising a high speed photodiode for detecting a laser beam whose traveling path is changed by the modulating beam splitter, and the traveling path is changed by the modulating beam splitter. A reference splitter which separates the laser beam, which is an ongoing reference light, in two directions opposite to the reference light detection sensor side, and a laser beam that is the reference light separated by the reference splitter toward the reference light detection sensor; A high speed scanning interferometer system comprising a reference optical focus lens to focus on a sensor. 6. The apparatus according to claim 5, wherein the reflected light detecting device comprises: a reflected light detecting sensor comprising a high speed photodiode for detecting a laser beam which is reflected light reflected from the surface of the measuring object among the laser beams scanned on the measuring object loaded on the table; A reflection light splitter for selecting a laser beam, which is reflected light reflected from the surface of water, to change the path toward the reflection light detection sensor, and focusing the reflection light that is changed by the reflection light splitter toward the reflection light detection sensor; A reflective light source lens, a reflective light cable for transmitting the reflected light carried by the reflective light source lens to a predetermined position, and the reference light and the reflected light cable which are separated by the reference splitter to the opposite side of the reference light detection sensor The above-described half by mixing the reflected light transmitted through Photodetecting the light reflected towards the mixer to proceed sensor, high-speed scanning interferometer system that includes a reflected light focus lens for focusing the laser beam reflected by the mixture in a mixer to the reflected light sensor. 7. The high speed scanning interferometer system according to claim 6, wherein in the reflected light mixer, a laser beam oscillated by the laser oscillator and demodulated by the acoustic optical machine is transmitted through a predetermined path and mixed with the reference light and the reflected light. The transmission light detection device according to claim 6, wherein the transmission light detection device comprises a transmission light detection sensor comprising a high speed photodiode for detecting a laser beam that is transmission light that passes through the measurement object among laser beams scanned on the measurement object loaded on the table. A flat mirror for changing the path of the laser beam, which is transmitted through the laser beam, to the transmitted light detection sensor, and a transmitted light circumferential lens for focusing the transmitted light that is changed in the path toward the transmitted light detection sensor by the plane mirror; And a transmission light cable for transmitting the transmission light carried by the transmission light circumferential lens to a predetermined position, and the reference light which is separated and propagated to the opposite side of the reference light detection sensor by the reference splitter and transmitted through the transmission light cable. Transmitted light mixing which mixes the transmitted light and proceeds to said transmitted light detection sensor And a high-speed scanning interferometer system including a transmitted light focus lens for focusing the laser beam from the mixture by mixing the transmitted light with the transmitted light detected by the sensor. The high speed scanning interferometer system according to claim 8, wherein, in the transmission light mixer, a laser beam oscillated by the laser oscillator and demodulated by the acoustic optical machine is transmitted through a predetermined path and mixed with the reference light and the transient light. The data processing apparatus according to claim 2, further comprising: a storage device for connecting a display device for displaying data processing results to the data processing device, and storing various values processed by the data processing device displayed on the display device. High speed scanning interferometer system to connect. The apparatus of claim 2, wherein the data processing apparatus is connected with a real time signal processor for processing a signal in real time, the real time signal is connected with a digital to analog converter, and the digital / analog converter is connected to a defect from the converted signal. A high-speed scanning interferometer system to which defect detection electronics for searching and processing are connected.