JPH08271393A - Permeability measuring sample, manufacture thereof, and permeability measuring method - Google Patents

Abstract

PURPOSE: To prevent a measurement error in measuring the permeability of a raw material by removing the surface roughness, residual impurities such as an abrasive material, and a structural defect caused by the residual stress generated by machining, and setting the surface loss of the measuring wavelength of the polished face of a sample to a specific value or below. CONSTITUTION: Specifications of a permeability measuring sample are set to the parallelism of 30sec or below, the face accuracy of about the same as that of the parallelism, the surface roughness rms=10Å or below, the internal absorption coefficient of 0.1%/cm for stable measurement. The surface loss occurs when various components contained in an abrasive such as the main components CeO2 , Al2 O3 and diamond abrasive grains of the abrasive of an optical raw material remain as the impurities remaining on the surface of the sample. The effect of the metal impurities can be removed when high-purity SiO2 fine grains are used for finish polishing. The structural defect caused by the residual stress can be removed by the acid and alkali cleaning method. The ultraviolet cleaning of the sample before measurement is effective. The surface loss of the measuring wavelength is set to 0.1% or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended for highly accurate measurement of the transmittance of optical materials such as multi-component optical glass, synthetic quartz glass, and crystalline materials, such as internal transmittance (spectral transmittance not including reflection loss). The present invention relates to a sample to be used, a manufacturing method thereof, and a measuring method. Especially, g line (436 nm), i
Multi-component optical glass used in visible / ultraviolet optical systems typified by linear (365 nm) lithography and KrF
(248 nm), ArF (193 nm) The present invention relates to a synthetic quartz glass used in an ultraviolet optical system of 300 nm or less such as excimer laser lithography, and a sample for measuring transmittance of a crystalline material.

[0002]

2. Description of the Related Art Conventionally, in an optical lithography technique for exposing and transferring a fine pattern of an integrated circuit onto a wafer such as silicon, an exposure device called a stepper is used. The light source of this stepper has been shortened in wavelength from g line to i line with the recent high integration of LSI. The internal transmittance of the optical glass used in the illumination system or projection lens of such a stepper is 99.8% / cm or 99.9% / cm or more (internal absorption 0.2% / cm,
Alternatively, 0.1% / cm or less) is required. The light source of the stepper has been changed to a KrF or ArF excimer laser as the LSI is further integrated.
General optical glass can no longer be used for the illumination system or projection lens of such an excimer laser stepper,
Limited to materials such as quartz glass and fluorite. Quartz glass and fluorite used in the illumination system or projection lens of such excimer laser stepper are also required to have an internal transmittance of 99.8% / cm or 99.9% / cm or more. Therefore, development aiming at high transmittance of the above optical material in the ultraviolet region is under way. On the other hand, as the wavelength becomes shorter, it becomes technically very difficult to measure the internal transmittance of the optical material with high accuracy. Therefore, in order to achieve a high transmittance of an optical material, first of all, the internal transmittance (internal absorption of 0.1%) of optical glass, synthetic quartz glass, crystal material, etc., having only such weak absorption exists. / Cm) is required to be accurately measured and evaluated.

[0003]

As a method of measuring the internal transmittance, the Japan Optical Glass Industry Association standard JOGIS-17-8 is used.
2 defines the method of measuring the internal transmittance of optical glass. With respect to other optical materials such as quartz glass and crystal materials, the method of measuring the internal transmittance is based on this. In this specification, for the preparation of the transmittance measurement sample, the thickness of 3 mm and the pair of 10 mm are used as a pair, and the opposite surfaces are ground in parallel, and the internal transmittance is indicated by the value for the glass of 10 mm thickness. Since it is displayed and the number is rounded off to two decimal places, the measurement accuracy is only 1% / cm for internal absorption, and i-line, excimer laser, etc. where the problem of measurement error of internal transmittance becomes particularly noticeable. The short wavelength region of was not targeted.

In the method of measuring the transmittance of an optical material, the following items are mainly examined in order to measure the internal absorption of 0.1% / cm as a significant difference. Spectral transmittance (transmittance including reflection loss) is measured using a spectrophotometer with high basic performance. In a commercially available spectrophotometer, the transmittance shift caused by the optical path shift caused by inserting the sample into the measurement optical path is corrected. A sample with high accuracy, that is, a measurement error is small, is manufactured.

With respect to ,, due to the development of the device,
Measurement fluctuation at 93 nm and 248 nm is ± 3σ
Achieved 0.01%. In addition, since the light rays are parallel rays, a device having substantially no influence of uneven sensitivity on the photocathode of the photomultiplier tube used as a detector, which is caused by deviation of the optical path due to refraction, was manufactured.

[0006] However, as for the conventional method, there is no standard for the sample for measuring the transmittance, and the item and the degree of defining the accuracy of the sample have not been quantified. Therefore, a manufacturing method for realizing the standard of the transmittance measurement sample has not been shown.

[0007]

Means for Solving the Problems In the method of measuring the transmittance of an optical material, the inventors of the present invention have earnestly studied the measurement error caused by the standard of the sample for measuring the transmittance and the manufacturing method. Then, as a result of examining the measurement error factors due to the sample, it was found that the parallelism, surface accuracy, and surface roughness of the polished surface of the sample were problems.

Generally, a sample is prepared by cutting out a part of an optical material to be evaluated into a shape that fits into a sample chamber of a spectrophotometer, and optically polishing two opposing surfaces in the thickness direction with a commercially available abrasive. . Here, the parallelism is
Based on one of the two facing optical polishing surfaces,
It is the inclination (angle) with respect to the reference plane. Further, the surface accuracy is the amount of deviation of the polishing surface from the flat prototype, and the surface roughness is the height of the irregularities on each optical polishing surface.

The present inventors have previously stated that the parallelism is 30 seconds or less,
Surface accuracy is less than or equal to parallelism, surface roughness rms = 10Å
It has been proposed that the internal transmittance of the optical material can be measured with high accuracy with an error of ± 0.1% or less by using the following samples. Furthermore, the cutting used when making the transmittance measurement sample, it was found that the structural defects caused by the residual stress such as residual impurities and processing such as abrasives is the cause of the decrease in the spectral transmittance of the optical material,
In the preparation of a sample of an optical material, the sample is pre-polished to have a surface roughness of rms = 10 Å, and then rms = 10 Å or less with a SiO ₂ abrasive, or a transmittance measurement characterized by acid or alkali treatment. A method of making samples was proposed.

However, in measuring the transmittance of an optical material in the ultraviolet region of the short wavelength or the vacuum ultraviolet region, for example, higher precision measurement is desired. Therefore, further research was conducted on how the surface condition of the transmittance measurement sample greatly affects the measurement accuracy. The condition of the surface of the sample is controlled by three of the above-mentioned factors, in particular, surface roughness, residual impurities such as abrasives, and structural defects caused by residual stress generated by processing. Therefore, by setting the surface loss of the sample to 0.1% or less, it is possible to measure with higher accuracy.

Furthermore, by performing ultraviolet cleaning before the measurement, it is possible to suppress the influence on the measurement result of the sample surface.

[0012]

The following equation holds for the optical path shift of the measuring light which affects the parallelism and the transmittance of the sample.

[0013]

[Equation 1]

From this, it is understood that it is necessary to define the parallelism of the samples when performing the relative comparison of the transmittances. Further, since the inclination direction of the sample with respect to the measurement light determines the displacement direction of the measurement light on the detector, it is preferable that the inclination directions of the sample be aligned during measurement. However,
From the experimental results, it was found that the measurement error can be ignored if the parallelism is 30 seconds or less.

The surface precision was measured using a fringe scanning interferometer. In addition, the parallelism of the sample defined above (30
The surface accuracy that gives a height difference equivalent to (sec) can be obtained from the following equation.

[0016]

[Equation 2]

Where λ is the wavelength of the measuring light, which is usually 5
46 nm, 2 means the number of faces, L means the diameter of the sample, the maximum length (cm) of the polished face of the sample such as the diagonal line. Therefore, surface accuracy = 1.33Lλ or less is required. It was found that there is no problem in measurement accuracy if the actual measurement value of the surface accuracy of the transmittance measurement sample is within the surface accuracy derived by the above formula. When d is calculated from the above equation, d = 1.33
It becomes L.

Regarding the surface roughness, a verification experiment of sample specifications was conducted, paying attention to the fact that the spectral transmittance of the optical material is measured lower than the theoretical transmittance calculated from the refractive index. Here is an example. First, the theoretical transmittance will be described. The spectral transmittance T considering multiple reflection is defined by the following equations (1) and (2).

[0019]

(Equation 3)

R is the reflectance when the measurement light is incident perpendicularly to the surface of the optical material.

[0021]

[Equation 4]

The theoretical transmissivity T ₀ is expressed by the equation (1) when the decrease in light quantity is only reflection loss, that is, the internal absorption coefficient a
Is the calculated value of the spectral transmittance when 0 is 0 or the calculated value of the spectral transmittance when the sample thickness is infinitely small. Generally, the spectral transmittance is measured to be lower than the theoretical transmittance, that is, the scattering loss due to the surface roughness of the sample is considered as one of the causes of the surface loss of the measurement light amount.

Therefore, the measurement wavelength 248n is shown in FIGS.
The relationship between the surface roughness of the sample at m and 193 nm and the theoretical transmittance excluding scattering loss is shown. The theoretical transmittance T (dispersion) excluding the surface scattering loss due to the surface roughness is calculated using the following approximate expression.

[0024]

(Equation 5)

As for the spectral transmittances for various surface roughnesses shown in the figure, synthetic quartz glass manufactured under the same conditions was used as the transmittance measurement sample, and standards other than the surface roughness were parallelism of 30 seconds and surface roughness. The precision was 3λ and the thickness t was 10 ± 0.05 mm. The surface roughness is measured by using an optical interference type surface roughness meter and is calculated by the following formula.

[0026]

(Equation 6)

As can be seen from FIGS. 1 and 2, the theoretical transmittance including the surface scattering loss was calculated. As the surface roughness of the sample increased, the theoretical transmittance at the measurement wavelength, that is, 248.
nm is 92.12% / cm, and 193 nm is 90.8.
It tends to deviate from 7% / cm. Here, the wavy lines in FIGS. 1 and 2 show the theoretical transmittance in the case where there is no surface scattering loss,
The solid line shows the theoretical transmittance including surface scattering depending on the surface roughness, and the ● dot shows the actual measured value.

Therefore, it is theoretically understood that the standard of the transmittance measurement sample having the surface roughness rms = 10 Å or less is required to secure the measurement accuracy. From the above, according to the present invention, in the method for measuring the transmittance of an optical material, a standard is set for the transmittance measurement sample, and the standard is set to a parallelism of 30 seconds or less,
Surface accuracy is less than or equal to parallelism, surface roughness rms = 10Å
It is possible to stably measure the internal absorption coefficient of 0.1% / cm as a significant difference.

On the other hand, as can be seen from FIGS. 1 and 2, actual measured values of the spectral transmittance for various surface roughness (● dots)
Shows a tendency similar to the theoretical transmittance excluding surface scattering loss although there is a large variation. However, it is understood that the spectral transmittance is measured at least 0.1% or more lower than the theoretical transmittance excluding the surface scattering loss regardless of the surface roughness. In addition, this phenomenon is especially caused by the short wavelength of 193n.
It is remarkable in m.

Since the surface loss, which is the cause of the decrease in the spectral transmittance, cannot be explained only by the scattering loss, the present inventors conducted various measurements on the sample surface. Residual impurities on the sample surface can be analyzed by a usual surface analysis method, for example E
The SCA and X-ray fluorescence analyzer had a problem in sensitivity and it was impossible to quantify impurities. Therefore, analysis was performed using a total reflection X-ray fluorescence analyzer. The results are shown below. a) A large amount of Ce impurities was detected on the sample surface where the spectral transmittance was measured to be particularly low. b) In some cases, Ce impurities were not detected by the total reflection X-ray fluorescence analysis, and the sample had a low spectral transmittance at 193 nm.

It is considered that this is because CeO ₂ which is the main component of the polishing agent used for producing the sample remains in the microcracks on the surface of the sample. As the impurities remaining on the surface of the sample, various components contained in the polishing agent may be considered in addition to the main components CeO ₂ , Al ₂ O ₃ , ZrO ₂ and diamond abrasive grains of the polishing agent of the optical material. It is considered that even when these components remain as trace impurities on the sample surface, similar surface loss is caused.

The influence of metallic impurities is as follows:
It can be removed by finish polishing using O ₂ fine particles. Further, in the shorter wavelength region, the influence of organic residues below the detection limit, impurities other than Ce, etc., or the influence of structural defects due to residual stress becomes large, and the result of b) can be obtained by experiments, It became clear by analysis.

The residual stress can be removed by an acid or alkali cleaning method. From these facts, it was clarified that the factor other than the surface scattering of the sample is largely influenced by the loss due to the absorption of the sample surface as the factor affecting the transmittance measurement. Therefore, the inventors of the present invention used an internal absorption coefficient of 0.
A method for producing a transmittance measurement sample that enables accurate measurement with a significant difference of 1% / cm was examined. As a result, it was found by various experiments that it is effective to perform ultraviolet cleaning by ultraviolet irradiation.

This is a method of cleaning the surface by irradiating the sample with ultraviolet rays to decompose organic substances on the surface and simultaneously oxidizing and removing the generated ozone O ₃ . The history of UV cleaning is described below. Even if the sample is stored in a container that has been vacuum-sealed and N ₂ purged while maintaining the clean room and cleanliness, the transmittance measurement value changes relatively quickly and an error occurs in the measurement. -Si in the frame
Inspired by the surface contamination phenomenon of the substrate, emission gas analysis, ES
Various experiments such as CA and contact angle measurements revealed the following. After the wet precision cleaning, the transmittance decreases with time. After wet precision cleaning, hydrocarbon-based impurities increase on the surface over time.

From these, it is estimated that the cause of the decrease in transmittance is the surface loss due to the hydrocarbon-based impurities in the several atomic layers attached to the surface. As a measure against these, just before measurement,
I tried to do UV cleaning. As a result of experiments, it was confirmed that the ultraviolet cleaning method is simple in treatment and extremely effective in a short time. From this, it can be confirmed that the presence of the hydrocarbon compound in the surface layer is the main cause of the surface loss.

Next, the experimental results of the effect of the ultraviolet cleaning will be described in detail. The principle of UV cleaning is to decompose organic compounds such as carbohydrates by UV irradiation using a low-pressure Hg lamp and to reduce O _{2 in} the air from O ₂ → O + during irradiation.
O, O + O ₂ → O ₃ generated active oxygen O ^*
The organic compound is in the gaseous state due to the strong oxidizing action of
For example H ₂ O, then changed to CO _2, N _2, etc., are removed from the non-irradiated surface, in that a very clean surface is obtained.

However, it is desirable that the contaminants that can be removed by the ultraviolet treatment have a few atomic layers on the surface. This is because if the film thickness due to contaminants is large, the processing time may increase. For this reason, it is desirable to combine with other cleaning methods, for example, acid and alkali cleaning, or so-called precision cleaning method in which an aqueous system and an organic system are combined. This effect is more pronounced at the shorter wavelength, 193 nm, so 193 nm transmittance measurements were investigated.

First, the relationship between the UV treatment time and the transmittance including reflection loss at 193 nm was investigated. As shown in FIG. 3, the measured transmittance increases with the start of the treatment, and approaches the theoretical transmittance value of 90.87% calculated from the refractive index. The deviation from the theoretical value is the loss due to internal scattering. Considering the internal scattering loss coefficient of 0.15% / cm calculated from the internal scattering measurement value, the internal absorption can be estimated to be 0.05% / cm or less.

FIG. 4 shows the relationship between the UV treatment time and the contact angle, and FIG. 5 shows the relationship between the contact angle and the surface loss. here,
The contact angle is a value measured by a liquid solution method using water. A clean surface has a high surface energy, and a contaminated surface has a low surface energy. Therefore, when an equal amount of droplets is dropped, it spreads widely on a clean surface and has a small contact angle, and on a contaminated surface. , Because it repels drops, it has a large contact angle.

That is, on the surface of the sample having a large contact angle, the contaminant organic substance adheres to the surface, and the organic substance is removed by the ultraviolet treatment, and the surface loss is reduced.
Therefore, it seems that the transmittance can be accurately measured. Reading from FIG. 4, in order to make the surface loss 0.1%,
It was confirmed that this can be achieved by setting the contact angle to 10 ° or less.

As the light source, a high output lamp in the ultraviolet region such as an Hg lamp, an excimer lamp, an ultraviolet pulse laser such as an ArF excimer laser, and an Ar ion laser are used.
It was confirmed by an experiment similar to the low pressure Hg lamp that an ultraviolet CW laser such as the third harmonic or the Nd: YAG third harmonic can be used. In particular, when the Hg lamp is used, the sample itself is damaged and changes in the physical properties of the sample (for example, decrease in transmittance, occurrence of cracks, change in surface shape, etc.)
Is preferable because it can prevent

When the dependency of the O ₂ concentration on the atmosphere during the ultraviolet treatment was confirmed, the effect by the treatment and the cleaning effect by the treatment time were almost the same at an O ₂ concentration of 5% or more. However, if it is 5% or less, the treatment effect is slightly inferior, and the treatment time for obtaining the same effect becomes long. For this reason,
The atmosphere O ₂ concentration during the ultraviolet treatment is preferably 5% or more.

This effect is due to the multi-component optical glass and C
It can also be applied to precision measurement of transmittance of an optical single crystal such as aF ₂ . Hereinafter, the present invention will be described in detail with reference to examples.

[0044]

[Example] A high-purity quartz glass ingot, which is an optical material, uses high-purity silicon tetrachloride as a raw material, and an oxygen gas and a hydrogen gas are mixed and burned by a quartz glass burner, and the raw material gas is carried from the center. It was diluted with a gas (usually oxygen gas), ejected, deposited on a target, melted, and synthesized. This gives a diameter of 180 mm and a length of 550
A mm quartz glass ingot was obtained.

Further, regarding the obtained quartz glass ingot and fluorite single crystal, metal impurities (Ti, Cr,
When quantitative analysis of Fe, Ni, Cu, Zn, Co, Mn) was performed by inductively coupled plasma emission spectroscopy, the concentrations were 20 ppb or less, respectively, and it was found that the silica glass and fluorite are of high purity. . The internal scattering loss coefficient of this quartz glass was calculated to be 0.15% / cm from the actual measurement value using an integrating sphere. Here, the main cause of the internal scattering is Rayleigh scattering, Brillian scattering, and the like, which are caused by the essential physical properties of quartz glass.

As the transmittance measuring device, a double-beam ultra-precision spectrophotometer using parallel beams was prepared and used. Here, regarding the 193 nm transmittance, FIG. 6 shows a comparison between the data obtained by a commercially available spectrophotometer which is not parallel light and the data obtained by the ultra-precision spectrophotometer manufactured in this example.

The same sample was measured, and the surface loss was practically negligible because the sample preparation method of this patent was used. The solid line shows the internal scattering loss coefficient of 0.15.
It is the theoretical transmittance including the internal scattering loss of% / cm. ● Dots are ultra-precision spectrophotometers of this patent, ■ Dots are commercially available spectrophotometers, and are actual data obtained by measuring the dependence of the transmittance on the sample thickness. ● In the regression line of dots, the intercept agrees with the theoretical value, and the deviation from the straight line is small, while the dot shows the sensitivity of the photocathode of the photomultiplier tube due to the deviation of the optical path due to the sample thickness. Due to the effect of unevenness,
There is no linearity. The ultra-precision spectrophotometer of this example is
It was confirmed that the accuracy was very good because parallel light was used. The deviation of the ● dot regression equation and the theoretical solid line in Fig. 6 seems to be due to internal absorption. As described above, by using the transmittance measuring method of the present invention, the internal absorption can be calculated with high accuracy from the transmission loss-internal scattering loss.

In all the data of the following examples, a double-beam ultra-precision spectrophotometer using a parallel beam produced according to the present invention was used. The internal scattering loss coefficients of the quartz glass samples used were all 0.15% / cm ± 0.03.
Is. [Example 1] The results of confirming the ultraviolet cleaning effect of the transmittance sample are shown in Fig. 7.

(3) The dots were finely polished by SiO2, the parallelism was 30 seconds or less, the surface accuracy was less than or equal to the parallelism, and the surface roughness was rms = 10Å or less. It is a value. Further, ● dots are data of a sample which was further washed with ultraviolet rays for 10 minutes before the measurement of the transmittance.

The wavy line and the alternate long and short dash line are regression lines, respectively, and the coefficient of determination R = 0.99 and standard error = 0.01. The solid line indicates the theoretical transmittance (transmittance including reflection / internal scattering loss) including the internal scattering loss of 0.15% / cm. The linearity of the data without UV treatment is good due to the high accuracy of the measuring device according to this patent,
The intercept is 0.12% lower than theoretical. This is also considered to be the surface loss due to organic contaminants, because the slope is the same as the regression line of ● dots.

On the other hand, in the measured value of the dot which was washed with ultraviolet rays, the intercept was in agreement with the theoretical value. Thus, the deviation of the intercept indicates the surface loss, and the component showing the thickness dependency such as the theoretical transmittance and the regression line of the measured value, which includes the internal scattering loss, is the internal transmission loss. [Example 2] Fig. 8 shows a method for producing a transmittance sample and a measurement example using a transmittance measuring device.

The sample used for the measurement was one whose absorption was expected to be slightly larger than usual. The sample for transmittance measurement was finish-polished with SiO ₂ and had a parallelism of 30.
Seconds or less, surface accuracy equal to or less than parallelism, surface roughness rms
This is the transmittance measurement data of a sample obtained by performing precision cleaning after precision polishing of 10 Å or less and further performing ultraviolet cleaning for 10 minutes before measuring the transmittance.

The solid line shows the internal scattering loss coefficient of 0.15% / c.
The theoretical transmittance including the internal scattering loss of m (transmittance including reflection / internal scattering loss) is shown. The dashed line is the regression line,
The coefficient of determination R was 0.99 and the standard error was 0.01.
It can be seen that the linearity is very high and the intercept matches the solid line, that is, the theoretical value. From the slope of the regression line,
A transmission loss coefficient of 0.19% / cm was calculated. Transmission loss coefficient-internal scattering loss coefficient = absorption coefficient, so 0.19
−0.15 = 0.04% / cm was calculated. [Example 3] Fig. 9 shows a method for producing a transmittance sample and a measurement example using a transmittance measuring device.

The sample used for the measurement was one in which absorption was expected to be somewhat average. The sample for transmittance measurement was finish-polished with SiO ₂ and had a parallelism of 30 seconds or less, a surface accuracy of the same degree or less as the parallelism, and a surface roughness rms = 1.
It is the transmittance measurement data of a sample which was subjected to precision cleaning after precision polishing to 0 Å or less, and further subjected to ultraviolet cleaning for 10 minutes before transmittance measurement.

The solid line shows the internal scattering loss coefficient of 0.15% / c.
The theoretical transmittance including the internal scattering loss of m (transmittance including reflection / internal scattering loss) is shown. The wavy line is the regression line,
The coefficient of determination R was 0.99 and the standard error was 0.01.
It can be seen that the linearity is very high and the intercept matches the solid line, that is, the theoretical value. From the slope of the regression line,
A transmission loss coefficient of 0.17% / cm was calculated. Transmission loss coefficient-internal scattering loss coefficient = absorption coefficient, so 0.17
−0.15 = 0.02% / cm was calculated.

[0056]

According to the standard of the sample and the method of manufacturing the sample according to the present invention, the internal transmittance of the optical material is ± 0.1.
It has become possible to measure with high accuracy with an error of% / cm or less. INDUSTRIAL APPLICABILITY The present invention is particularly effective in measuring the transmittance in the ultraviolet region of the short wavelength region and the vacuum ultraviolet region.

Further, it can also be used for optical parts in which minute absorption in the short wavelength region poses a problem.

[Brief description of drawings]

FIG. 1 shows the sample surface roughness and various transmittances (248
(nm) is the graph which plotted the relationship.

FIG. 2 shows the sample surface roughness and various transmittances (193
(nm) is the graph which plotted the relationship.

FIG. 3 Sample UV treatment time and spectral transmittance (19
3 nm) is a graph plotting the relationship.

FIG. 4 is a graph plotting the relationship between the sample UV treatment time and the sample surface contact angle.

FIG. 5: Sample surface contact angle and surface loss (193n
It is the graph which plotted the relationship of m).

FIG. 6 is a graph showing sample thickness dependence in transmittance measurement of the ultra-precision transmittance measuring device according to the present invention.

FIG. 7: Example 1 according to the present invention, 1 of synthetic quartz glass
It is the graph which plotted the 93 nm spectral transmittance measurement result.

FIG. 8: Example 2 according to the present invention, 1 of synthetic quartz glass
It is the graph which plotted the 93 nm spectral transmittance measurement result.

FIG. 9: Example 3 according to the present invention, 1 of synthetic quartz glass
It is the graph which plotted the 93 nm spectral transmittance measurement result.

Claims (8)

[Claims] 1. A transmittance measurement sample of an optical material having two opposite surfaces polished, wherein the surface loss at the measurement wavelength of each polished surface is 0.1% or less. 2. A transmittance measurement sample of an optical material having two opposite surfaces polished, wherein the polished surface is washed with ultraviolet light before the transmittance measurement. 3. A transmittance measurement sample of an optical material having two opposite surfaces polished, wherein the polishing surface has a cleanliness degree corresponding to a contact angle of water of 10 ° or less. 4. A method for producing a sample for measuring a transmittance of an optical material, which comprises polishing two surfaces facing each other and washing with ultraviolet light in a processing atmosphere having an oxygen concentration of 5% or more. 5. The method for producing a transmittance sample according to claim 4, wherein the light source for the ultraviolet cleaning is an Hg lamp. 6. The transmittance of an optical material, which has two opposite surfaces polished and whose surface loss at the measurement wavelength of the polished surfaces is 0.1% or less, is measured by a spectrophotometer. Measuring method. 7. The method for measuring transmittance according to claim 6, wherein the spectrophotometer uses a parallel beam. 8. The two surfaces facing each other are polished, and the polished surface is cleaned with ultraviolet light, and the surface loss of the measured wavelength of the polished surface is 0.1.
A method for measuring the transmittance, wherein the transmittance of the optical material, which is less than or equal to%, is measured by a spectrophotometer using a parallel beam.