JP2014228396A - Diffraction grating cross-sectional shape measurement instrument and cross-sectional shape measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cross-sectional shape measurement instrument and a cross-sectional shape measurement method which are capable of measuring, without destruction, a cross-sectional shape of a diffraction grating having a material not transmitting light.SOLUTION: The cross-sectional shape measurement instrument includes: a nanoimprint production unit which produces a shape measurement sample made of a resin by transferring a groove shape of a measurement object with a groove to the resin; a scatterometry optical system which causes light to obliquely impinge on the shape measurement sample to measure a spectral waveform of reflected light reflected from the groove shape; and a data processing unit which uses simulation to calculate spectral waveforms for several preliminarily assumed cross-sectional shapes of the groove of the measurement object and stores calculation results. The data processing unit determines a cross-sectional shape of the groove of the measurement object on the basis of the spectral waveform measured by the scatterometry optical system and the spectral waveforms calculated in the data processing unit by simulation.

Description

  The present invention relates to an apparatus for measuring a cross-sectional shape of a diffraction grating and a method for measuring the cross-sectional shape.

  A diffraction grating is an optical element that divides light of various wavelengths (white light) used in a spectroscope into narrowband wavelengths, and has fine grooves on the surface of an optical material on which a reflective metal is deposited. It is rare.

  The optical performance of the diffraction grating is affected by the periodic shift of grooves engraved in the diffraction grating and irregularities in the groove shape. Therefore, it is necessary to measure the cross-sectional shape of the diffraction grating in order to confirm the periodicity of the manufactured grooves and the shape of the grooves. An electron microscope such as an SEM (scanning electron microscope) is used for measuring the cross-sectional shape of the diffraction grating.

  However, in this method, it is necessary to cut the sample in order to obtain detailed information on the cross section. For this reason, the sample once cut for measurement cannot be used, so it is not practical to measure the cross section of all the produced diffraction gratings.

  Therefore, there is a method using scatterometry as a method for measuring the cross-sectional shape without cutting the sample. This method is a light measurement technique in which light of a plurality of wavelengths is incident on a sample at a predetermined angle, the reflected light of the sample is measured, and a parameter representing a change in spectral reflectance or polarization state is calculated from the reflected light. This is a method combined with a simulation technique using an electromagnetic wave analysis technique (see, for example, Patent Document 1). The method using the spectral reflectance is easy to measure, and the method using the parameter representing the change in the polarization state is characterized by high measurement accuracy.

JP2012-19111A

  However, in the method of measuring the cross-sectional shape by measuring the reflected light of a sample by entering light of a plurality of wavelengths at a predetermined angle using the scatterometry as described above, the sample is like a metal. Scatterometry is not applicable when a material that does not transmit light is used for the sample surface. That is, there is a problem that the cross-sectional shape of the diffraction grating in which the reflective metal is deposited on the sample surface cannot be measured.

  Accordingly, an object of the present invention is to provide a cross-sectional shape measuring apparatus and a cross-sectional shape measuring method capable of nondestructively measuring the cross-sectional shape of a diffraction grating having a material that does not transmit light.

In order to solve the above problems, the main features of the cross-sectional shape measuring apparatus according to the present invention are as follows.
1) A nanoimprint production part for producing a shape measurement sample made of the resin by transferring the groove shape of an object to be measured having a groove to the resin; light is obliquely incident on the shape measurement sample and reflected from the groove shape; Calculates the spectral waveform for some of the cross-sectional shapes of the groove of the object to be measured, which is assumed in advance, by measuring the spectral waveform of the reflected light, and stores the calculation result A data processing unit, and in the data processing unit, the cross-sectional shape of the groove of the object to be measured based on the spectral waveform measured by the scatterometry optical system and the spectral waveform calculated by simulation in the data processing unit. It is characterized by determining.

The main features of the cross-sectional shape measuring method according to the present invention are as follows.
2) A cross-sectional shape measuring method using a measuring apparatus including a nanoprint manufacturing unit, a scatterometry optical system, and a data processing unit, and the measurement target possessed in advance by the measured object in the data processing unit A step of calculating a spectral waveform for some of the shape of the part in advance using a simulation and storing the calculation result; and in a nanoprint producing part, the nanoimprint is used for the object to be measured. A step of transferring the shape of the measurement target portion to the resin, a step of preparing a shape measurement sample made of a resin for measuring the shape of the measurement target portion, and a plurality of shape measurement samples in the scatterometry optical system. Measuring the spectral waveform of the reflected light reflected from the shape of the measurement target part for a plurality of wavelengths, The spectral waveform shape measurement sample measured at Yatorometori optical system, characterized by a step of determining the shape of the target portion of the object based on the result calculated by simulation by the data processing unit.

  ADVANTAGE OF THE INVENTION According to this invention, the cross-sectional shape measuring apparatus and cross-sectional shape measuring technique which can measure the cross-sectional shape of a diffraction grating nondestructively can be provided.

It is a flowchart which shows the cross-sectional shape measuring method shown in 1st Embodiment. It is a figure which shows the transfer method using nanoimprint. It is a figure which shows the optical system of a cross-sectional shape measuring apparatus. It is a figure which shows the method of determining cross-sectional shape. It is a figure which shows the manufacture procedure of a diffraction grating.

  Embodiments according to the present invention will be described below with reference to the drawings.

  The diffraction grating cross-sectional shape measuring apparatus according to the present invention is a measuring apparatus incorporating the nanoimprint manufacturing apparatus shown in FIG. 2 and the scatterometry optical system shown in FIG. Therefore, each of the nanoimprint manufacturing apparatus and the scatterometry optical system according to the present invention will be described below.

First embodiment

The first embodiment relates to measurement of the sectional shape of a replica diffraction grating.
FIG. 1 is a flowchart showing a cross-sectional shape measuring method. The following (1) to (4) show the procedure for measuring the cross-sectional shape.
(1) The shape is transferred to the resin using nanoprint (step 101). A shape evaluation sample is prepared by transfer. This nanoprint will be described later with reference to FIG.
(2) The reflected light of the shape evaluation sample is measured using scatterometry, and the spectral reflectance is calculated from the measured reflected light (step 102). The calculation of the spectral reflectance will be described later in [Step 1] shown in FIG.
(3) Using an electromagnetic wave analysis such as the RCWA method, the spectral reflectance is calculated for each cross-sectional shape of the diffraction grating, and a library is created (step 103). The creation of this library will be described later in [Step 2] shown in FIG.
(4) Data that most closely matches the measured spectral reflectance is searched in the library to determine the shape (step 104). The determination of the shape will be described later in [Step 3] shown in FIG.

  Hereinafter, the transfer method using nanoimprint shown in Step 101 will be described in detail with reference to FIG.

  The “nanoimprint technology” is a molding technique in which a nano stamper (original plate) on which a nanoscale uneven pattern is formed is pressed against a substrate coated with a resin thin film, and the uneven pattern is transferred to the resin thin film. The nanoimprint process includes four elements: (1) application, (2) press, (3) transfer, and (4) release, and transfer includes optical (UV) nanoimprint and thermal nanoimprint. In this embodiment, optical (UV) nanoimprint is used. However, it is also possible to use thermal nanoimprint in this embodiment.

First, FIGS. 2A to 2C illustrate a method of forming the replica diffraction grating 201. FIG.
In the present embodiment, the diffraction grating hereinafter refers to a replica diffraction grating.
In FIG. 2A, a diffraction grating 201 having a groove pattern in which a reflective metal 204 is deposited on a surface of an optical material 202 such as glass via an adhesive resin 203 is prepared. Next, resin is dropped onto the reflective metal 204 from a resin dropping nozzle 206 provided above the diffraction grating 201. The resin is dripped over the entire diffraction grating 201. For this resin, a photo-curing resin 205 that is cured by irradiation with ultraviolet rays is used.

  Next, in FIG.2 (b), the dripped photocurable resin 205 is pressurized using the nanoprint board | substrate 207 from upper direction. The pressurized photocurable resin 205 flows along the surface shape of the groove pattern and is transferred to the same shape as the groove pattern. Further, since the nanoprint substrate 207 is made of a material that transmits ultraviolet rays (UV), the ultraviolet rays (300 nm to 400 nm) irradiated from the upper side of the nanoprint substrate by the ultraviolet irradiation device 208 are nanoprinted. It penetrates the substrate. The photo-curing resin 205 can be cured by ultraviolet light transmitted through the nanoprint substrate 207, and a cured resin having the same pattern as the groove pattern is formed on the nanoprint substrate. A cross-sectional shape measurement sample 209 having the groove pattern of the cured resin is obtained.

  Note that the above-described optical nanoimprint has a feature that a shape can be transferred onto a resin with an accuracy of several tens of nm, which has been difficult with the prior art.

  Next, in FIG. 2C, the cross-sectional shape measurement sample 209 obtained in FIG.

  Since the resin used for optical nanoimprinting is a material that transmits light, it is possible to measure the cross-sectional shape using scatterometry.

≪Explanation of scatterometry optical system≫
Next, the measuring instrument 300 shown in FIG. 2 will be described with reference to FIG.
The measuring device 300 is a measuring device using scatterometry. This scatterometry is a method of measuring a spectral waveform of reflected light from a measurement target when light of various wavelengths (white light) is obliquely incident at a certain angle.

  FIG. 3 shows a light source 301 that emits white light, a spectroscopic optical element 304 that splits light reflected from the sample to be measured, a detector 303 that detects light dispersed by the spectroscopic optical element 304, and the detector 303. 1 shows a measuring instrument composed of an optical signal amplifier 304 for processing an optical signal transmitted from the A / D converter, an A / D converter 305, and a computer 306.

  As shown in this figure, the light emitted from the light source 301 is incident on the cross-sectional shape measurement sample 209 at a predetermined angle. The reflected light of the cross-sectional shape measurement sample 209 is spatially wavelength-separated by the spectroscopic optical element 304. The separated light is incident on the photodetector 303 in which diodes are arranged on the array, and is converted into an optical signal. The input optical signal is amplified by the optical signal amplifier 304, converted into an electronic signal digitized by the A / D converter 305, and then taken into the computer 306.

≪Measurement method of cross-sectional shape≫
A method for measuring the cross-sectional shape of the diffraction grating will be described with reference to FIG.
In [Step 1] shown in the figure, the spectral waveform of the cross-sectional shape measurement sample that is the object to be measured is measured. The measurement of the spectral waveform is as described above with reference to FIG.
In [Step 1] of this figure, a waveform distribution showing the spectral reflectance measured for a wavelength in a predetermined range is shown. That is, since the surface of the diffraction grating is covered with a reflective metal, light cannot be transmitted, but reflected light from the surface can be measured. Spectral reflectance is measured based on this reflected light.

  Next, in [Step 2] shown in this figure, a spectral waveform in a presumed cross-sectional shape pattern is calculated using an electromagnetic field analysis method such as RCWA (Rigorous Coupled Wave Analysis), and the library An example of creating is shown. In this figure, the groove pattern formed in the diffraction grating and the spectral waveform calculated using the electromagnetic field analysis method for the groove pattern are shown. Here, as an example, three groove patterns are shown, and each groove pattern is a triangular shape, and representative cases are the sides X1 to X3, the bases Y1 to Y3, and the angles α1 to α3 formed by the base and the hypotenuse. Shown as an example.

  Finally, in [Step 3] shown in the figure, data that most closely matches the spectral waveform measured in [Step 1] is searched from the library created in [Step 2] to determine the shape (library matching). ).

  The cross-sectional shape measuring apparatus shown in this embodiment is a nanoimprint manufacturing apparatus and a measuring apparatus with a built-in scatterometry optical system as described above. The shape is transferred onto a resin using nanoimprint, and the scatterometry is measured. Since the cross-sectional shape can be measured by using it, the cross-sectional shape can be measured regardless of the material to be measured.

  Therefore, it is possible to measure a diffraction grating having a reflective metal deposited on the surface, which could not be performed by the conventional measurement method. In addition, since non-destructive measurement can be performed, all manufactured diffraction gratings can be measured.

Second embodiment

The second embodiment is characterized in that a cross section of a master diffraction grating that is a source of a replica diffraction grating is measured.
In the present embodiment, a method using a scriber for a diffraction grating (a ruling engine) is described. However, in manufacturing a diffraction grating, any method may be used as long as a replica diffraction grating is manufactured using a master diffraction grating. There is no particular limitation.

The manufacturing procedure (procedure 1 to procedure 5) of the diffraction grating will be described below with reference to FIG.
Procedure 1: The diffraction grating groove is formed by pressing the tool 502 of the diffraction grating scorer 501 against the reflective metal layer 504 formed on the glass substrate 503. The diffraction grating manufactured in this way is called a master diffraction grating 507.
Most of the commercially available diffraction gratings are replica diffraction gratings having a shape transferred from the above-mentioned 507.
Next, a procedure for transferring the shape from the master diffraction grating 507 to the replica diffraction grating will be described.
In the procedure 2, the reflective metal 506 is deposited on the surface of the master diffraction grating created in the procedure 1 by using the reflective metal vapor deposition device 505.
In step 3, the resin 508 is applied on the reflective metal deposited in step 2.
In step 4, the glass substrate is pressed from above the resin applied in step 3, the resin is cured, and the reflective metal and the glass substrate are bonded. The shape of the master diffraction grating is transferred to the reflective metal deposited in the procedure 2.
Finally, in step 5, the master diffraction grating and the replica diffraction grating are peeled off.

  By measuring the cross section of the master diffraction grating 507, variations in the optical performance of the diffraction grating can be reduced.

  201 ... Diffraction grating with reflective metal deposited on the surface, 202 ... Optical material, 203 ... Resin, 204 ... Reflective metal, 205 ... Light curable resin, 206 ... Drip nozzle, 207 ... Optical nanoimprint substrate, 208 ... UV irradiation 209 ... Sample for evaluating cross-sectional shape, 300 ... 301 ... Light source, 302 ... Spectroscopic optical element, 303 ... Optical detector, 304 ... Optical signal amplifier, 305 ... A / D converter, 306 ... Computer, 501 ... Diffraction grating Scriber for engraving, 502 ... tool, 503 ... reflecting metal layer, 504 ... reflecting metal vapor deposition device, 507 ... master diffraction grating.

Claims (8)

A nanoimprint production part for producing a sample for shape measurement comprising the resin by transferring the groove shape of the object to be measured having a groove to the resin;
A scatterometry optical system that obliquely enters light into the shape measurement sample and measures a spectral waveform of reflected light reflected from the groove shape;
A spectroscopic waveform is calculated using simulation for some of the cross-sectional shapes of the groove of the object to be assumed in advance, and a data processing unit that stores the calculation result,
In the data processing unit, the cross-sectional shape of the groove of the measured object shape is determined based on the spectral waveform measured by the scatterometry optical system and the spectral waveform calculated by simulation in the data processing unit. A characteristic cross-sectional shape measuring apparatus. The shape of the measurement target portion of the object to be measured is a groove shape formed on the diffraction grating,
The cross-sectional shape measuring apparatus according to claim 1, wherein a groove shape of the object to be measured is determined using a spectral waveform calculated by the simulation from a spectral waveform of reflected light from the groove shape. The scatterometry optical system obliquely enters a plurality of wavelengths of light with a constant incident angle on the shape measurement sample, and measures a spectral waveform of reflected light reflected from the groove shape for the plurality of wavelengths. The cross-sectional shape measuring apparatus according to claim 1. The shape of the measurement target portion of the object to be measured is a groove shape formed on the diffraction grating,
A spectral waveform of reflected light is measured from the groove shape, a polarization state is calculated from the measured spectral waveform, and a shape of a measurement target portion of the object to be measured is determined based on the spectral waveform and the polarization state. The cross-sectional shape measuring apparatus according to claim 1. A cross-sectional shape measuring method using a nanoprint production unit, a scatterometry optical system, and a measurement device including a data processing unit,
In the data processing unit, a step of calculating a spectral waveform in advance using a simulation for some of the shapes of the measurement target portion of the object to be assumed in advance, and storing the calculation result;
In the nanoprint production part, a step of transferring the shape of the measurement target part of the measurement object to the resin using nanoimprint for the measurement object;
Producing a shape measuring sample made of the resin for measuring the shape of the measurement target part; and
In the scatterometry optical system, light of a plurality of wavelengths is obliquely incident on the shape measurement sample with a constant incident angle, and a spectral waveform of reflected light reflected from the shape of the measurement target portion is obtained for the plurality of wavelengths. Measuring process;
Determining the shape of the measurement target part of the object to be measured based on the spectral waveform of the sample for shape measurement measured by the scatterometry optical system and the result calculated by simulation in the data processing part; A method for measuring a cross-sectional shape, comprising: In the step of determining the shape of the measurement target part of the object to be measured,
The shape of the measurement target portion of the object to be measured is a groove shape formed on the diffraction grating,
The cross-sectional shape measurement method according to claim 5, wherein the groove shape of the object to be measured is determined using the spectral waveform calculated by the simulation from the spectral waveform of reflected light from the groove shape. The step of transferring the shape of the measurement target part to the resin,
A step of pressing the resin applied on the measurement target portion of the object to be measured using a transparent substrate;
A step of transmitting the transparent substrate through the transparent substrate and irradiating with UV light, curing the resin, and creating a sample for shape measurement made of the resin. The cross-sectional shape measuring method according to claim 5. The shape of the measurement target portion of the object to be measured is a groove shape formed on the diffraction grating,
The cross-sectional shape measuring method according to claim 5, wherein a polarization state assumed from the cross-sectional shape of the diffraction grating is calculated by simulation.

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