KR20090043697A - Dual-mode spectral imaging method and system using acousto-optic tunable filter, and optical apparatus using the same - Google Patents

Abstract

The present invention relates to a dual-mode spectroscopic imaging method using an acoustic optical modulation filter, a system, and an optical device using the same. The present invention relates to a stationary wave and an abnormal wave using spectroscopic and polarization characteristics of an acoustic optical modulation filter. Dual-mode spectroscopic imaging using an acousto-optic modulation filter capable of measuring the refractive index and thickness of semiconductor thin films including multi-layered thin films, their shapes, and the refractive index and spectral property values of cells at high speed by measuring two diffracted lights in dual mode. It is an object of the present invention to provide a method, a system, and an optical device using the same.

As a means for solving this problem, the dual-mode spectroscopic imaging system using the acoustooptic optical filter according to the present invention comprises: a light source unit for spectroscopically irradiating light generated from a light source into measurement light and reference light; A specimen part which irradiates the measurement light onto the specimen to obtain the reflected measurement light; A reference unit for polarizing the reference light; An acoustic optical modulation filter for spectroscopically diffracting the reflected measurement light and the polarized reference light with two diffracted light having different polarization states; A detector for detecting each diffracted light; And a signal processing and control unit for controlling the imaging processing and the acoustic optical modulation filter by using the detected diffracted light. In addition, the present invention provides an optical device including a method for imaging using such an imaging system and an optical member for performing the imaging method.

Acousto-optic modulation filter, birefringence, polarization, dual mode, polarization and spectroscopy

Description

Dual-mode Spectral Imaging Method and System using Acousto-Optic Tunable Filter, and Optical Apparatus using the same

The present invention relates to a dual mode spectroscopic imaging method using an acoustic optical modulation filter, a system and an optical device using the same. The present invention relates to a dual mode spectroscopic imaging method using an acoustic optical modulation filter that can be used in a dual mode, a system thereof, and an optical device using the same.

The development of semiconductor technology has led to miniaturization and large capacity of semiconductor devices. What is emerging as a main point in the manufacture of such semiconductor devices is the interest in how finely the production technology and pattern of the next generation wafer can be formed.

Recently, as a technique for forming a fine pattern, a CMP (Chemlcal Mechanical Polishing) process obtained through a planarization process has been in the spotlight. CMP refers to the implementation of chemical or mechanical polishing on a substrate over the entire substrate. However, in the implementation of such flatness, only the unnecessary parts can be polished if the degree of flattening, that is, the thickness of the layer applied on the substrate or the shape thereof is accurately known.

In addition, with the development of the semiconductor industry, in the display industry, for example, in the field of flat panel display (FPD), in order to lower the defect rate and improve the quality, there is a big problem of controlling the thickness of the thin film constantly.

Also in the bioindustry, which is another industrial field, obtaining an index of refraction or spectral properties of cells has become an important issue.

One of the technical fields commonly required in various fields as described above is an optical device that can precisely measure the shape and thickness of a measurement target, and in particular, can immediately know the thickness of the measurement target along with processing in a machining process.

In order to meet such demands, there are many examples of applying an acoustic-optical tuneable filter (AOTF) as an optical device.

As shown in FIG. 1, the AOTF 40 includes PZTs 43 on both sides of an anisotropic (Birefringenet) crystal 42. In particular, when an RF signal is applied to the PZT 43, an acoustic wave is generated, and thus a standing wave of the acoustic wave is formed inside the anisotropic crystal 42. Since the standing wave functions like a diffraction grating, it can be used as a band pass filter for wavelength.

Another advantage of the AOTF 40 is that the period of the standing wave in the decision 42 changes depending on the RF frequency applied to the PZT 43. By using this property, it can be used as a filter that can pass a band of a specific wavelength only by changing the RF frequency.

In addition, another advantage of the AOTF 40 is that due to the anisotropy of the crystal 42, the projected light is spectroscopically divided into two diffracted light beams (normal and unsteady) polarized in a direction perpendicular to each other. That is, when light having an arbitrary wavelength bandwidth and an arbitrary polarization state is incident on the AOTF 40, it is spectroscopically diffracted light having two different polarization states in a direction determined by the direction of the anisotropic crystal 42. . In particular, the wavelength band of each diffracted light at this time is determined by the frequency applied to the PZT 43. Since the generation of such two diffracted light is already well known by the acousto-optic effect, the description thereof is omitted here.

The technique using the conventional AOTF 40 uses only one diffracted light out of two diffracted light polarized by the optoacoustic effect. That is, after scanning the light onto the specimen and passing the interference signal between the light coming out of the specimen and the light coming out of the reference plane through the acoustic optical modulation filter, the diffracted standing wave and the abnormal wave of a specific wavelength according to the frequency applied to the acoustic optical modulation filter. One signal was obtained for all wavelengths, and the thickness and shape information of the specimen was measured by analyzing the signal.

However, in the case of a specimen in which a very thin transparent thin film is coated on the opaque measuring part, in addition to the wavefront reflected from the opaque measuring part, the light reflected from the surface of the transparent thin film affects the interference and is separated. It is difficult, and it takes a lot of time when it is separated using a software algorithm.

As a solution to this problem, Korean Patent Publication No. 10-0451881 (name: a three-dimensional shape measuring apparatus of a transparent thin film using an acoustic optical modulation filter) is disclosed. This patent is a transparent thin film using an acoustic optical modulation filter capable of independently extracting thickness information and shape information for a measurement object of a multi-layer structure by independent mode-specific measurement of blocking plates for white light irradiated to a reference plane. It provides a three-dimensional shape measuring apparatus of.

However, this method has a disadvantage in that the measurement must be performed twice in the same environment, respectively, with and without the blocking plate for the specimen to be measured. Measurement errors can occur if the system is misaligned during the mounting and removal of the blocking plate, or if the external environment changes during the two measurements. In addition, since the same measurement must be performed twice with and without the blocking plate, the measurement time may be longer.

The present invention has been made in view of the above, and by using the spectroscopic and polarization characteristics of the acoustic optical modulation filter, two diffracted lights containing different information are measured in dual mode by including two-layered thin films. To provide a dual-mode spectroscopic imaging method, a system, and an optical device using the acoustic optical modulation filter that can accurately and accurately measure the refractive index or thickness or shape of the semiconductor thin film and the refractive index and spectral properties of the cells. There is this.

As a means for solving this problem, the dual-mode spectroscopic imaging system using the acoustic optical modulation filter according to the present invention,

A light source unit for spectroscopically irradiating the light generated from the light source with the measurement light and the reference light;

A test piece unit irradiating the test light to the test piece to obtain the reflected test light;

A reference unit for polarizing the reference light;

An acoustic optical modulation filter for spectroscopy with two diffracted light having different polarization states from interference light obtained by polarizing the reflected measurement light and the polarized reference light;

A detector for detecting the diffracted light; And

And a signal processing and a controller for controlling the imaging process and the acoustooptic modulation filter by using the detected diffracted light.

The light source unit may include a light source for generating light, a lens unit for condensing the generated light, and a light separation unit for separating the collected light, wherein the light source may be a white light or a laser having a variable wavelength. do.

In addition, the lens unit is characterized in that it is configured to change the light source to parallel light or to adjust the amount of light.

In addition, the specimen portion comprises a lens for focusing the measurement light, and a specimen mounting portion for mounting the specimen, wherein the specimen is characterized in that the thin film is coated or a specific cell or optical element.

In addition, the reference portion comprises a polarizer, a lens portion and a reflecting mirror, in particular, characterized in that configured to be rotatable to change the direction of the linearly polarized light. The reference unit may be an optical device that may change a polarization state, including a phase retarder or a liquid crystal variable retarder (LCVR) or a woolton prism. In addition, the reference unit is characterized by irradiating the acoustic optical modulation filter in the form of a standing wave or an abnormal wave by linearly polarizing the reference light.

In addition, the detector is characterized in that to obtain a spectral signal in the diffraction direction of the stationary wave and the diffraction direction of the stationary wave, respectively, wherein the spectral signal is a spectral signal of only the measurement light and the spectral signal where the reference light and the measurement light interfere with each other. do.

The detection unit may include two two-dimensional imaging elements for forming each diffracted light, and may further include a lens unit for imaging or condensing.

In addition, in the diffracted light detected by each of the detectors, any one of the diffracted light includes data for both the reference light and the measured light, and the other diffracted light includes only the data for the measured light.

The signal processing and control unit may further include an acoustic optical modulation filter driver for changing the wavelength of the light that is input to the acoustic optical modulation filter.

On the other hand, the dual-mode spectroscopic imaging method using an acoustic optical modulation filter according to the present invention,

Spectroscopy the light generated from the light source into the measurement light and the reference light (S100);

Irradiating the measurement light onto a specimen to obtain the reflected measurement light (S200);

Polarizing the reference light (S300);

Condensing the reflected measurement light and the polarized reference light with an acoustic optical modulation filter to form two diffracted light having different polarization states (S400); And

And detecting and processing data from the diffracted light (S500).

In addition, in the diffraction light forming step (S400), each diffracted light is polarized using a birefringence phenomenon, wherein each diffracted light is a diffracted light polarized in an orthogonal direction while passing through an acoustic optical modulation filter. do.

Further, the data relating to the measurement light and the reference light is detected from any one of these diffracted light, and the data relating to the measurement light is detected from the other diffracted light.

On the other hand, the optical device according to the invention is characterized in that it comprises an optical member for performing each of the above-described imaging method.

According to the present invention has the following effects.

1) Because the two diffracted lights from one acoustic optical modulation filter are measured in dual mode, the thickness and refractive index of the specimen including multiple thin films can be measured at high speed and precision.

2) Accordingly, it is possible to manufacture optical devices that can be applied in various industrial fields such as semiconductor production process, thin film manufacturing process, and bio industry that require such high speed / precision measurement.

3) The structure of the system can be simplified because one acoustic optical modulation filter can be used to replace the spectroscopic and polarizing elements.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 is a schematic diagram showing the configuration for explaining a dual-mode spectroscopic imaging system using an acoustic optical modulation filter according to the present invention.

The system according to the present invention includes a light source unit 10 for largely spectroscopic light, a specimen unit 20 for obtaining light reflected from the specimen, a reference unit 30 for polarizing the spectroscopic light, and an acoustic optical And a modulation filter 40, a detector 50 for detecting the diffracted two diffracted lights, a signal processing and a controller 60 for processing the detected data.

The light source unit 10 is spectroscopically analyzed by the measurement light irradiated on the specimen to be measured and the reference light as a reference. To this end, as shown in FIG. 3, the light source unit 10 includes a light source 11, a lens unit 12, and an optical separation unit 13.

The light source 11 generates a white light or a laser having a variable wavelength, and the generated light is collected by the lens unit 12. The collected light is separated into the measurement light and the reference light by the optical separator 13.

In this case, the lens unit 12 is preferably configured to change to parallel light or to adjust the amount of light emitted from the light so that the white light or the laser is not dispersed and can enhance the condensing effect. In addition, the optical splitter 13 may use a conventional beam splitter.

The specimen part 20 receives the measurement light and irradiates the specimen 21 to be measured to enter the reflected light into the light splitter 13. The specimen 20 includes a lens 22 for collecting the measurement light and the reflected light, and a specimen mounting portion 23 for mounting the specimen 21.

Here, in the preferred embodiment of the present invention, the specimen 21 may be a substrate on which a thin film such as an oxide film or a dielectric film is formed, and the specimen 21 may be a cell or an optical device.

The reference unit 30 polarizes the reference light incident from the light source unit 10 to be a stationary or abnormal wave. Here, a standing wave or an abnormal wave refers to a standing wave or an abnormal wave state that is spectroscopically emitted when an arbitrary light is diffracted by an acoustic optical modulation filter.

As such, the reference unit 30 includes a polarizer 31, a lens unit 32, and a reflector 33 as a configuration for polarizing the reference light, and these components are configured to be positioned perpendicular to the reference light. .

In addition, the polarizer 31 may use a polarizer 31 which is generally used, and may use a phase retarder, a wollaston prism, or an electrical signal capable of arbitrarily changing the polarization state. It is also possible to use a device such as a liquid crystal variable retarder (LCVR) that can adjust the amount of delayed phase. The polarizer 31 may be configured to be rotated to change the direction of linear polarization under the control of the signal processing and the control unit 60.

The acoustic optical modulation filter 40 diffracts the incident light into stationary and abnormal waves having a specific wavelength to produce diffracted light. In particular, the acoustic optical modulation filter 40 is different in the degree of diffraction of the light spectroscopy according to the RF signal, the RF signal is used for the acoustic optical modulation filter 40 under the control of the signal processing and control unit 60 to be described later It is controlled by the driver 41.

The detection unit 50 includes two two-dimensional imaging elements 51 and 52 so as to detect and form two diffracted lights that are diffracted and spectroscopically transmitted while passing through the acoustic optical modulation filter 40. In addition, each of the two-dimensional imaging elements 51 and 52 may further include a lens unit 53 for collecting an image or collecting light.

The detection unit 50 obtains a spectral signal from the diffracted light of the standing wave and the abnormal wave state through the two-dimensional imaging elements 51 and 52, respectively. In this case, the signal related to the measurement light and the reference light may be obtained in one of the spectroscopic signals, and only the signal of the reference light may be obtained in the other. The detected spectral signal is transmitted to the signal processing and control unit 60.

The signal processing and control unit 60 analyzes the signals detected from the two imaging elements 51 and 52 to detect the shape and thickness of the specimen to be measured. In addition, the RF frequency of the acoustic optical modulation filter 40 may be controlled by controlling the driver 41 according to the type of specimen.

Further, in a preferred embodiment of the present invention, the signal processing and control unit 60 controls the reference unit 30 to control the polarizer 31 according to the RF frequency signal applied to the acoustic optical modulation filter 40 to control the reference light. It is preferable to configure so that a polarization degree can be adjusted.

On the other hand, the dual-mode spectroscopic imaging method using the acoustic optical modulation filter according to the present invention will be described in conjunction with the system described above.

4 is a flowchart illustrating a dual mode spectroscopic imaging method using an acoustic optical modulation filter according to the present invention.

As a first step, the light is subjected to step S100. The light at this time is a light irradiated from the light source 11, which is a white light or a laser light having a variable wavelength, and the light is separated into two lights (measured light and reference light) by the light separation unit 13.

Then, the spectroscopic measurement light is irradiated onto the specimen 21 to obtain the reflected light (S200). At this time, the measurement light is collected by the lens 22, irradiated onto the specimen 21, reflected, and then collected by the lens 22. The reflected and condensed measurement light is incident on the optical separator 13 of the light source unit 10 and then incident on the acoustic optical modulation filter 40 through interference with reference light, which will be described later.

The next step is to polarize the reference light (S300). In this step (S300), the reference light spectroscopy from the light source 11 is polarized through the polarizer 31. At this time, the degree of polarization is polarized to a degree of polarization such as a standing wave or an abnormal wave that is spectroscopically analyzed by the acoustic optical modulation filter 40 under the signal processing and the control of the controller 60.

The measurement light and the reference light having passed through the above steps (S200 and S300) are irradiated to the optical separator 13, and then subjected to spectroscopy, followed by a step (S400) of obtaining diffracted light having different polarization states. That is, the reflected measurement light and the polarized reference light are irradiated to the optical separator 13 to obtain interference light, and the interference light is irradiated to the acoustic optical modulation filter 40 to be two diffracted light previously determined according to the RF frequency. Spectroscopic.

At this time, the diffracted light includes a signal relating to the measurement light and the reference light, and the other diffracted light includes a signal relating to the measurement light. This is because when the measurement light is irradiated to the acoustic optical modulation filter 40, spectroscopy is performed with the standing wave and the abnormal wave, and in the case of the reference light, the polarization is performed with the standing wave or the abnormal wave in advance. For example, assuming that the reference light is polarized into a standing wave, the first diffraction light includes a signal related to the standing wave and an abnormal wave, and the second diffraction light includes a signal relating to the standing wave. Of course, when the reference light is an abnormal wave, the opposite signals are included.

In a next step S400, the two diffracted light beams thus diffracted through the two-dimensional imaging device of the detector 50 are respectively detected. The diffracted light thus detected is transmitted to the signal processing and control unit 60.

In the last step (S500), as described above, the optical signal obtained in the dual mode form is processed by the signal processing and control unit 60 to obtain the thickness of the thin film to be measured, the refractive index of the cell, or the spectral property value.

On the other hand, in the preferred embodiment of the present invention, the optical member for performing the above-described imaging method and the optical device provided with such an optical member are also included in the present invention.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will cover such modifications and variations as fall within the spirit of the invention.

1 is a schematic diagram for explaining an acoustic optical modulation filter (AOTF).

Figure 2 is a schematic diagram showing the configuration for explaining a dual-mode spectroscopic imaging system using an acoustic optical modulation filter according to the present invention.

Figure 3 is a schematic diagram showing an embodiment of a dual mode spectroscopic imaging system using an acoustic optical modulation filter according to the present invention.

Figure 4 is a flow chart for explaining a dual mode spectroscopic imaging method using an acoustic optical modulation filter according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: light source

11: light source

12: lens unit

13: optical separation unit

20: specimen

21: Psalms

22 lens

23: specimen mounting part

30: reference

31: polarizer

32: lens unit

33: reflector

40: Acoustic Optical Modulation Filter

41: driver

42: anisotropic crystal

43: PZT

50: detector

51,52: two-dimensional imaging device

53: lens unit

60: signal processing and control unit

Claims (21)

A light source unit 10 for spectroscopically irradiating the light generated from the light source 11 with the measurement light and the reference light; A specimen 21 for irradiating the measurement light onto the specimen 21 to obtain reflected measurement light; A reference unit 30 for polarizing the reference light; An acoustic optical modulation filter 40 for spectroscopy with two diffracted light having different polarization states from interference light obtained by polarizing the reflected measurement light and the polarized reference light; A detection unit (50) for detecting the diffracted light; And And a signal processing and control unit (60) for controlling the imaging process and the acoustooptic modulation filter (40) by using the detected diffracted light. The method of claim 1, The light source unit 10 includes a light source 11 for generating light, a lens unit 12 for collecting the generated light, and an optical separation unit 13 for separating the collected light. Dual-mode spectroscopic imaging system using a modulation filter. The method of claim 2, The light source 11 is a dual-mode spectroscopic imaging system using an acoustic optical modulation filter, characterized in that the white light or a laser having a variable wavelength. The method of claim 2, The lens unit 12 is a dual-mode spectroscopic imaging system using an acoustic optical modulation filter, characterized in that configured to convert the light into parallel light or to adjust the amount of light. The method of claim 1, The specimen portion 20 includes a lens 22 for focusing the measurement light and a specimen mounting portion 23 for mounting the specimen 21, dual-mode spectroscopy using an acoustic optical modulation filter. Imaging system. The method of claim 5, wherein The specimen 21 is a dual-mode spectroscopic imaging system using an acoustic optical modulation filter, characterized in that the thin film is coated or a specific cell or optical element. The method of claim 1, The reference unit 30 includes a lens unit 32 for condensing the reference light, a polarizer 31 for polarizing the collected reference light, and a reflector 33 for reflecting the polarized reference light again. Dual-mode spectroscopic imaging system using optical modulation filters. The method according to claim 1 or 7, The reference unit 30 is a dual-mode spectroscopic imaging system using an acoustic optical modulation filter, characterized in that configured to be rotatable to change the direction of the linearly polarized light. The method of claim 8, The reference unit 30 is an optical element capable of changing the polarization state, including a phase retarder or a liquid crystal variable retarder (LCVR) or a woolen prism (Wollaston Prism), dual mode using an acoustic optical modulation filter Spectroscopic imaging system. The method of claim 9, The reference unit 30 linearly polarizes the reference light to irradiate the acoustic optical modulation filter in the form of a standing wave or an abnormal wave, dual mode spectroscopic imaging system using an acoustic optical modulation filter. The method of claim 1, The detector 50 obtains a spectral signal in the diffraction direction of the abnormal wave and the diffraction direction of the standing wave, respectively. The method of claim 11, The spectral signal is a dual-mode spectroscopic imaging system using an acoustic optical modulation filter, characterized in that the reference light and the measurement light interfered with each other and a spectral signal of only the measurement light. The method according to claim 1 or 11, wherein The detection unit (50) is a dual-mode spectroscopic imaging system using an acoustic optical modulation filter, characterized in that comprises two two-dimensional imaging elements (51, 52) for forming each diffracted light. The method of claim 13, The detection unit 50 further comprises a lens unit 53 for imaging or condensing, dual mode spectroscopic imaging system using an acoustic optical modulation filter. The method of claim 1, The signal processing and control unit 60 further includes an acoustic optical modulation filter driver 41 for changing the wavelength of light that is input to the acoustic optical modulation filter 40 and spectroscopically. Dual-mode spectroscopic imaging system using. The method according to claim 1 or 15, The signal processing and control unit (60) is a dual-mode spectroscopic imaging system using an acoustic optical modulation filter, characterized in that for controlling the acoustic optical modulation filter 40 with an RF signal. Spectroscopy the light generated from the light source into the measurement light and the reference light (S100); Irradiating the measurement light onto a specimen to obtain the reflected measurement light (S200); Polarizing the reference light (S300); Condensing the reflected measurement light and the polarized reference light with an acoustic optical modulation filter 40 to form two diffracted light having different polarization states (S400); And And detecting and processing data from the diffracted light (S500). The method of claim 17, wherein in the diffraction light forming step (S400), And said each diffracted light is polarized using a birefringent phenomenon. The method of claim 17, wherein in the diffraction light forming step (S400), Each diffracted light is a diffraction light polarized in an orthogonal direction while passing through the acoustooptic modulation filter (40). The method of claim 17, wherein in the data detection step (S500), And detecting data related to the measurement light and the reference light from the diffracted light and detecting data related to the measurement light from the other diffracted light. 21. An optical apparatus comprising an optical member for performing the imaging method of any one of claims 17-20.

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