KR102015811B1 - Apparatus for inspecting surfaceusing using spectroscopic ellipsometer - Google Patents

Abstract

The present invention relates to an optical inspection device, and more particularly, to spectroscopically reflect reflected light reflected from a sample on a line-by-line basis, and to obtain spatial information and wavelength information for a line region composed of multiple measurement points at once, in a two-dimensional image form. Accordingly, the present invention relates to a surface inspection apparatus using a spectroscopic ellipsometer which enables simultaneous analysis of multiple measurement points and has high spatial resolution.
The surface inspection apparatus using the spectroscopic ellipsometer according to the present invention includes a polarization control module for converting light generated from a light source into linearly polarized light and projecting it onto a sample surface, focusing the measurement light in the form of a line on the sample surface, and based on the sample. Positioned symmetrically with the polarization control module, the spatial information corresponding to the multiple measurement point position corresponding to the measurement light line and the spectral information of the wavelength of each measurement point for the reflected light having a specific polarization characteristic reflected from the sample on different axes By calculating the elliptic constant based on the wavelength information for the multi-measurement point of the line unit through the polarization analysis module for obtaining a measurement image of the two-dimensional image by imaging to a two-dimensional image provided from the polarization analysis module, It is configured to include an image analysis module for analyzing the surface state of the sample line by line, the polarization analysis module And an imaging spectrometer configured to image each measuring point of the line-shaped reflected light applied from the slit formed on one side to a size one-to-one matching with the pixel size of the spatial information imaging axis of the CCD camera disposed on the other side. A plurality of mirrors forming an optical path so that the reflected light in the form of a line applied from the slit formed in the lens is focused on the CCD camera, and a reflective spectroscope for spectroscopically reflecting the reflected light in the form of a line on the optical path formed in the mirrors. It is characterized by.

Description

Surface inspection apparatus using spectroscopic ellipsometer {APPARATUS FOR INSPECTING SURFACEUSING USING SPECTROSCOPIC ELLIPSOMETER}

The present invention relates to an optical inspection device, and more particularly, by spectroscopically reflecting light reflected from a sample by line, and separating spatial information and wavelength information of a line region composed of multiple measurement points and acquiring them in a two-dimensional image form at once. In addition, the present invention relates to a surface inspection apparatus using a spectroscopic ellipsometer which enables simultaneous analysis of multiple measurement points and has high spatial resolution.

Ellipsometry, which is widely used as a non-destructive measurement method in the fields of semiconductor, display, and optical thin film, injects light having a controlled polarization state into a sample, and then measures and analyzes the changed polarization state of reflected light and polarizes it. It is a method to find the density change, the optical thickness, and the complex angulation rate of the sample, which are factors which changed the value.

An apparatus for this purpose is called an ellipsometer, and an ellipsometer is a device for controlling, measuring, and analyzing the polarization state of light, and is generally composed of a light source, a polarization generating module, a sample, a polarization detection module, and a light detector. An ellipsometer that measures and analyzes according to the wavelength is called a spectroscopic ellipsometer.

As the semiconductor process is progressed from the process of the circuit line width of 30 nm to the process of the circuit line width of 1x nm, the process thickness and line width of the thin film are also reduced, and the space of the spectroscopic ellipsometer, which is essential for monitoring the thickness of the thin film, is used in the semiconductor field. There is a growing demand for improving resolution.

A spectroscopic ellipsometer focuses light applied from a light source into a spot on a sample surface using a focusing optical system, and spots with a diameter of several tens of μm or less at the sample position over a wide wavelength band from the DUV region to the near infrared region. It is very difficult to implement due to the diffraction limit of the light, processing of the optical system, assembly error, etc.

In addition, the spectroscopic ellipsometer collects light generated from the light source of the ellipsometer into a spot for measurement to measure optical properties such as thickness, refractive index, etc. of the spot of the spot. Accordingly, there is a disadvantage in that the sample or the measurement module must be mechanically moved for each measurement point of the sample, and a large measurement time is required to measure a large area of the sample.

1. Korean Registered Patent No. 10-1057093 (Name: Spectroscopic Ellipsometer) 2. Korean Patent Publication No. 2016-0012476 (Name: Spectroscopic elliptical polarization measurement system and method and data analysis device and method)

Accordingly, in the present invention, the measurement light in the line unit corresponding to the multi-point region is incident to the sample, and the measurement light in the line unit reflected from the sample is distributed to multiple wavelengths using a reflective optical scatterometer to provide the CCD camera. In addition, by collecting a two-dimensional measurement image in which one axis shows spectral information of a wavelength and the other axis shows a position information of a sample through a CCD camera, it is possible to measure only a single spot of a spectroscopic ellipsometer. It is a technical object of the present invention to provide a surface inspection apparatus using a spectroscopic ellipsometer that can overcome the limitations of the spots of a high spatial resolution spectroscopic ellipsometer.

Surface inspection apparatus using a spectroscopic ellipsometer according to an aspect of the present invention for achieving the above object, by converting the light generated from the light source to linearly polarized light and projected to the sample surface, focusing the measurement light in the form of a line on the sample surface Spatial information and each measurement point corresponding to the measurement point position corresponding to the measurement light line with respect to the polarization control module and the reflected light having a specific polarization characteristic reflected from the specimen while being symmetrically positioned with respect to the polarization control module with respect to the sample. Polarization analysis module for acquiring measurement images of two-dimensional images by forming spectral information of different wavelengths on different axes, and wavelengths for multiple measurement points in line units through measurement image analysis of two-dimensional images provided from the polarization analysis module. The image analysis module analyzes the surface state of the sample line by line by calculating the elliptic constant based on the information. The polarization analysis module includes an imaging spectrometer configured to image each measuring point of the line-shaped reflected light applied from the slit formed on one side to a size that is one-to-one matching with the pixel size of the spatial information imaging axis of the CCD camera disposed on the other side. The imaging spectrometer comprises a plurality of mirrors forming an optical path so that the reflected light in the form of a line applied from a slit formed on one side is focused on the CCD camera, and the reflected light in the form of a line on the optical path formed in the mirrors. A reflective spectrometer for spectroscopy is arranged and configured.

At this time, the polarization control module is disposed on the optical axis between the light source and the sample and rotated by a predetermined angle unit, the polarizer for changing the white light applied from the light source to linear polarization, and disposed on the optical axis between the light source and the sample to measure the measurement light It is characterized by comprising a first focusing lens for changing to parallel light in the form of a line.

The polarization analysis module may include an analyzer for passing reflected light having a polarization characteristic corresponding to the polarizer, a second focusing lens for converting the reflected light into parallel light in a line shape, and a parallel light type passing through the second focusing lens. And a CCD camera for acquiring a measurement image in the form of a two-dimensional image formed on an imaging plane of the imaging spectrometer by spectroscopically reflecting the reflected light in a predetermined path to form spatial information and wavelength information on different axes. It is characterized by.

The imaging spectrometer may include a slit of a line structure for introducing reflected light in the form of parallel light applied from a second focusing lens in a form corresponding to a line unit, and parallel to the slit while being disposed on an opposite surface of the slit. The first mirror for reflecting the reflected light in the form of light having a first direction angle, the first mirror to be arranged on the opposite surface of the first mirror, the reflected light in the form of parallel light reflected from the first mirror to have a second direction angle A spectroscope for projecting the reflected light in the direction of the direction and separating the spectroscopic parallel light into two different axes by dividing it into wavelength information and spatial information, and being arranged on opposite surfaces of the spectroscope, A second mirror that reflects toward the spectroscope direction to have a third direction angle, and a spectrometer that is reflected from the second mirror while being disposed on an opposite surface of the second mirror The reflected light of the parallel beam type, characterized in that comprises a third mirror for imaging on the imaging surface of the CCD camera location.

The measurement image acquired by the CCD camera may be a two-dimensional image in which wavelength information is formed on an X axis, and measurement point position information corresponding to a measurement light line of a sample is formed on a Y axis.

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The image analysis module may be configured to simultaneously perform signal processing on multiple measurement points corresponding to measurement light lines using a graphic processing unit (GPU).

According to the present invention as described above, by using the spectroscopic information on the multiple measurement points of the line unit collected through one two-dimensional image can be analyzed at the same time the multiple measurement points can be ensured the rapidity of the sample surface inspection, of course In addition, the spectral information for each measuring point can provide a very precise inspection device with a spatial resolution of several μm.

1 is a view showing the configuration of a surface inspection apparatus using a spectroscopic ellipsometer according to a first embodiment of the present invention.
2 is a diagram showing the configuration of an imaging spectrometer 230 shown in FIG.
FIG. 3 is a diagram illustrating a measured image obtained by the CCD camera 240 shown in FIG.

Configurations shown in the embodiments and drawings described in the present invention are merely preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, the scope of the invention is the embodiments and drawings described in the text It should not be construed as limited by That is, since the embodiments may be variously modified and may have various forms, the scope of the present invention should be understood to include equivalents capable of realizing the technical idea. In addition, the objects or effects presented in the present invention does not mean that a specific embodiment should include all or only such effects, the scope of the present invention should not be understood as being limited thereby.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. The terms defined in the commonly used dictionary should be interpreted to correspond with the meanings in the context of the related art, and should not be interpreted as having an ideal or excessively formal meaning not explicitly defined in the present invention.

1 is a view showing the configuration of a surface inspection apparatus using a spectroscopic ellipsometer according to a first embodiment of the present invention, Figure 2 is a view showing the configuration of the imaging spectrometer 230 shown in FIG. 3 is a diagram illustrating a measured image obtained by the CCD camera 240 shown in FIG.

1 to 3, in the surface inspection apparatus using the spectroscopic ellipsometer according to the first embodiment of the present invention, the polarization control module 100 and the polarization analysis module 200 are symmetrical with respect to the sample 1. It is arranged to achieve a specific angle, the image analysis module 300 is coupled to the output terminal of the polarization analysis module 200 is configured.

The polarization control module 100 modulates white light into linearly polarized light to irradiate the sample 1 with the measurement light in the form of a line.

The line-shaped measurement light incident on the sample 1 changes the polarization state according to the surface characteristics of the sample 1, and the reflected light of the polarization state corresponding to the surface characteristics is reflected by the polarization analysis module 200.

The polarization analysis module 200 passes the reflected light of the polarization characteristic corresponding to the linear polarization characteristic of the polarization control module 100 of the incident reflected light, and spectroscopy the reflected light in the form of a line to measure the spatial information and the spectral information of the line. Separated and formed into a two-dimensional face.

In addition, the image analysis module 300 calculates an elliptic constant for the multi-measurement points in line units using the two-dimensional image provided from the polarization analysis module 200, thereby performing the surface state analysis process for the multi-measurement points in line units. At the same time.

In general, the elliptic constant calculation processing is performed in the CPU, and the CPU is composed of 1 to 8 cores optimized for the serial processing method (processing the next task after completing one operation). The calculation process is performed. In other words, when the CPU is applied to the elliptic constant processing means in this embodiment, the time required for multiplying the number of pixels on the axis corresponding to the spatial information of the camera by the time required for each pixel (measurement point) is one line. There is this.

In addition, the number of pixels of the CCD camera is also related to the spatial resolution to be measured. As the number of pixels of the CCD camera is increased, the spatial resolution is improved.

In other words, high spatial resolution is required for more accurate surface inspection of the sample, and a larger number of CCD camera pixels are required for this purpose.However, the method of calculating elliptic constants in units of measurement points using a CPU requires a lot of time. There is a problem that is required.

Accordingly, in the present invention, the signal processing is performed on a line-by-line basis using a graphic processing unit (GPU) to satisfy the high spatial resolution while calculating the elliptic constant for the high measurement point in the line unit more quickly. It is possible to carry out constant analysis simultaneously. GPUs can contain hundreds to thousands of cores, allowing massive amounts of data to be processed simultaneously.

Here, the algorithm for calculating the elliptic constant based on the characteristic information according to the wavelength with respect to the measurement point is a known technique for calculating using the measured amount of light for each wavelength and the rotation angle of the polarizer, and the sine and cosine functions. Therefore, detailed description thereof will be omitted.

In general, in a spectroscopic ellipsometer, linearly polarized light is generated to control a desired polarization state for unpolarized light. The linearly polarized light generates a rotating polarizer (RP) method for rotating a polarizer and an RA (rotating analyzer). Rotating Analyzer).

In the present embodiment, in the case of configuring a spectroscopic image ellipsometer in the form of a rotating analyzer (RA) for rotating an analyzer, the polarizer is considered to have a problem in obtaining accurate measurement information due to the shaking of the analyzer. It constructs a spectroscopic image ellipsometer in a rotating polarizer (RP) method that rotates.

Looking in more detail with respect to the surface inspection apparatus using a spectroscopic ellipsometer according to the present invention,

First, the polarization control module 100 includes a light source 110, a polarizer 120, and a first focusing lens 130, and the polarizer 120 and the first focusing lens 130 are inputs of the light source 110. It is arranged sequentially on the optical axis. In this case, the arrangement order of the polarizer 120 and the first focusing lens 130 may be changed.

The light source 110 is a light generating device irradiated to the sample 1 and generates light of various wavelength bands, that is, white light, from deep ultra violet (DUV) to near infrared.

The polarizer 120 polarizes the light generated by the light source 110 in a linearly polarized state. That is, since the light generated from the light source 100 is generally represented as non-polarized light that cannot be represented in a specific polarization state, the polarizer 120 is rotated by a rotating unit (not shown) by a predetermined angle (polarization angle) to thereby polarizer 120. To change the polarization of the light passing through.

The first focusing lens 130 focuses the measurement light polarized by the polarizer 120 to the sample 1 as parallel light in a line shape.

On the other hand, the measurement light incident on the surface of the sample (1) is reflected by the polarization modified according to the optical and structural features such as the refractive index, the thickness of the sample (1) is incident to the polarization analysis module 200.

The polarization analysis module 200 includes an analyzer 210, a second focusing lens 220, an imaging spectrometer 230, and a CCD camera 240, and includes an analyzer 210 and a second focusing lens ( 220 and the imaging spectrometer 230 are sequentially disposed on the reflected light path. In this case, the arrangement order of the analyzer 210 and the second focusing lens 220 may be changed. In addition, the imaging spectrometer 230 and the CCD camera 240 are integrally configured to obtain a more stable two-dimensional image from the CCD camera 240.

The analyzer 210 passes only a specific polarization of the reflected light applied from the sample 1 in response to the polarization characteristic modulated by the polarizer 110 of the polarization control module 100.

The second focusing lens 220 focuses the reflected light passing through the analyzer 210 to the imaging spectrometer 230 as parallel light in a line shape.

The imaging spectrometer 230 spectroscopically reflects reflected light in the form of parallel light applied through the second focusing lens 220 and reflects it in a predetermined path, and separates spatial information and wavelength information included in the reflected light into two different axial images. By forming a reflecting path so as to form an image, the spectroscopic information on the multiple measuring points corresponding to the measuring light lines is formed in a two-dimensional plane.

The imaging spectrometer 230 includes a slit 231, a first mirror 232, a spectroscope 233, a second mirror 234, and a third mirror 235. In this case, the first to third mirrors 232, 234, 235 and the spectrometer 233 are appropriately disposed such that a reflection path is formed inside the housing 2 having an internal space having a predetermined size and shape.

That is, since the imaging spectrometer 230 is composed of mirrors, chromatic aberration does not occur, and it is advantageous to manufacture a high resolution optical system without being limited to the wavelength band, and there is no characteristic of the wavelength change because no transmission medium is used. Applicable to a wide wavelength band over the near infrared.

The slit 231 is formed at one side of the housing 2 to introduce reflected light in the form of parallel light applied from the second focusing lens 220 into the housing 2. The slit 231 is formed in a line structure corresponding to the parallel light form of the reflected light. The slit 231 performs a function of blocking the inflow of ambient light, as well as reducing the resolution or throughput by forming a narrow structure. FIG. 3 (A) shows the reflected light L in the form of a line flowing into the reflective spectrometer 230 through the slit 231, and the measuring light composed of a plurality of measuring points located in a predetermined direction of the sample 1 Corresponds to the line.

The first mirror 232 is arranged to be spaced apart from the opposite surface of the slit 231 by a predetermined distance, and reflects the reflected light in the form of a line flowing through the slit 231 to have a first direction angle. The first mirror 232 may be formed of a collimator, for example, a collimating mirror, which parallelly outputs the distributed reflected light while flowing through the slit 231. At this time, the diameter of the light beam in the spectrometer is determined according to the size of the collimator.

The spectroscope 233 is disposed on the opposite surface of the first mirror 232 at a predetermined distance, and spectroscopically reflects the reflected light in the form of lines reflected from the first mirror 232 and projects it toward the first mirror direction to have a second direction angle. do.

At this time, the spectroscope 233 separates and projects the reflected light in the form of a line so that spatial information corresponding to the line and wavelength information spectroscopically by spatial position (measurement point position) are formed on different axes. For example, the spectrometer 233 may be formed of a diffraction grating, and the spatial information and the wavelength information may be imaged on different axes by projecting the wavelength information of the measurement point in different directions through the fixed diffraction grating.

The second mirror 234 is disposed on the opposite surface of the spectroscope 233 at a predetermined distance, and reflects the reflected light incident from the spectroscope 233 toward the spectroscope direction to have a third direction angle.

The third mirror 235 is disposed on the reflection path of the second mirror 234 so as to be spaced apart from the second mirror 234 by a predetermined distance, and provides spatial information and spectral information with respect to the reflected light reflected from the second mirror 234. Images are formed on different axes in two dimensions.

The CCD camera 240 is disposed on an image forming surface 236 of the reflected light reflected by the third mirror 235. The imaging surface 236 is disposed on the opposite surface of the slit 231.

Here, the positions of the spectroscope 232, the second mirror 234, the third mirror 235, and the imaging surface 236 may be positioned at a focal length at which the reflected light spectroscopically reflected by the spectrometer 232 is formed on the imaging surface 236. Correspondingly set.

That is, the reflected light in the form of a line is introduced into the housing 2 of the imaging spectrometer 230. At this time, the CCD camera 240 is disposed on the opposite side of the housing 2 in which the slit 231 is formed.

3B is a diagram illustrating a measurement image in the form of a two-dimensional image collected by the CCD camera 240.

As shown in FIG. 3, the measured image is composed of a two-dimensional image including wavelength information of the X axis and line space information (Row) of the Y axis. Here, the Y axis is the position of each measurement point corresponding to the incident light line L provided to the sample 1 in (A).

In other words, spectral information for each of the plurality of measuring points corresponding to the measuring light lines incident on the sample through the CCD camera 240 is obtained as a two-dimensional image. Here, the number of measurement points corresponding to one line may be set from several tens to thousands of measurement points according to the number of pixels of the CCD camera 240.

In general, the size of one pixel of the CCD camera 240 is 4 ~ 5μm. Therefore, if each measurement point for multiple measurement points on the sample surface is matched to the position of each CCD pixel by using one-to-one optical system, it is possible to construct a micro spot spectroscopic ellipsometer that can measure the measurement points of 5 μm or less. have. At this time, the polarization analysis module 200 configures the optical system to form the sample surface measurement point to be one-to-one matching with the pixel of the spatial information imaging axis of the CCD camera 240.

That is, the micro spot optical system of the spectroscopic ellipsometer for the process measurement of the existing semiconductor line is considered to be the limit of the spot size that can be measured due to the diffraction limit is 20 ~ 30 μm. However, when applying the multi-point spectroscopic ellipsometer method according to the present invention, it is possible to measure a measuring point of several μm by overcoming the diffraction limit of the conventional micro spot optical system.

As described above, according to the present invention, spectroscopic information on each measurement point can be obtained simultaneously in line units formed from multiple measurement points. This makes it possible to measure multiple measuring points of a sample without moving the sample or inspection module, and obtains high spatial resolution by obtaining wavelength information for a wide wavelength band for each measuring point through a reflective imaging spectrometer. Test results can be obtained.

100: polarization control module, 110: light source,
120: polarizer, 130: first focusing lens,
200: polarization analysis module, 210: the analyzer,
220: second focusing lens, 230: imaging spectrometer,
231: slit, 232,234,235: mirror,
233: spectrometer, 236: imaging plane,
240: CCD camera, 300: image analysis module,
1: sample, 2: housing.

Claims (7)

A polarization control module for converting the light generated from the light source into linearly polarized light and projecting it onto the sample surface, focusing the measurement light in the form of a line on the sample surface;
Positioned symmetrically with respect to the polarization control module with respect to the sample, the spatial information corresponding to the multiple measurement point position corresponding to the measurement light line for the reflected light having a specific polarization characteristic reflected from the sample and the spectral information of the wavelength for each measurement point Polarization analysis module for obtaining a measurement image of the two-dimensional image by forming a phase on different axes,
Comprising an image analysis module for analyzing the surface state of the sample by the line unit by calculating the elliptic constant based on the wavelength information for the multi-point measurement point in the line unit through the measurement image analysis of the two-dimensional image provided from the polarization analysis module But
The polarization analysis module comprises an imaging spectrometer for imaging each measurement point of the line-shaped reflected light applied from the slit formed on one side to a size one-to-one matching with the pixel size of the spatial information imaging axis of the CCD camera disposed on the other side,
The imaging spectrometer includes a plurality of mirrors forming an optical path so that the line-shaped reflected light applied from the slit formed on one side is focused to the CCD camera, and a reflection type that spectroscopic line-shaped reflected light on the optical path formed on the mirrors. Surface inspection apparatus using a spectroscopic ellipsometer, characterized in that the spectrograph is arranged.
The method of claim 1,
The polarization control module is disposed on the optical axis between the light source and the sample and rotated by a predetermined angle unit, the polarizer for changing the white light applied from the light source to linearly polarized light,
And a first focusing lens disposed on an optical axis between the light source and the sample, the first focusing lens converting the measurement light into a parallel light in a line shape.
The method of claim 2,
The polarization analysis module and the analyzer for passing the reflected light having a polarization characteristic corresponding to the polarizer;
A second focusing lens for converting the reflected light into line-like parallel light,
An imaging spectrometer for spectroscopically reflecting reflected light in the form of parallel light passing through the second focusing lens and reflecting it in a predetermined path, thereby forming spatial information and wavelength information on different axes;
Surface inspection apparatus using a spectroscopic ellipsometer, characterized in that it comprises a CCD camera for obtaining a measurement image in the form of a two-dimensional image formed on the imaging plane of the imaging spectrometer.
The method of claim 3,
The imaging spectrometer,
A slit of a line structure for introducing reflected light in the form of parallel light applied from the second focusing lens in a form corresponding to a line unit;
A first mirror disposed on an opposite surface of the slit and reflecting the reflected light in the form of parallel light flowing through the slit to have a first direction angle,
While disposed on the opposite surface of the first mirror, the reflected light in the form of parallel light reflected from the first mirror is spectroscopically projected to the first mirror direction side to have a second direction angle, the reflected light in the form of the parallel light is spectroscopic wavelength and space A spectrometer that separates the information into projections with different axes,
A second mirror disposed on an opposite surface of the spectroscope and reflecting the reflected light in the form of spectroscopic parallel light incident from the spectroscope toward the spectroscope direction to have a third direction angle;
A spectroscopic ellipsometer comprising a third mirror disposed on an opposite surface of the second mirror and configured to reflect reflected light in the form of spectroscopic parallel light reflected from the second mirror onto an image plane on which the CCD camera is located. Surface inspection device using.
The method of claim 4, wherein
The measurement image obtained by the CCD camera is a two-dimensional image of which wavelength information is formed on the X-axis and measurement point position information corresponding to the measurement light line of the sample is formed on the Y-axis. Inspection device.
delete The method of claim 1,
The image analysis module is a surface inspection apparatus using a spectroscopic ellipsometer, characterized in that configured to perform the signal processing for the multiple measuring points corresponding to the measurement light line using a graphic processing unit (GPU).

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