JP2000147750A - Pellicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent light resistance and transmitting property for UV rays by forming antireflection layers on both surfaces of a base body made of a dense metal oxide and constituting the antireflection layer of a porous metal oxide thin film. SOLUTION: A pellicle film or plate 1 consists of a dense metal oxide base body 2 and antireflection layers 313 formed on both surfaces of the base body 2. The antireflection layers 3, 3 consist of porous metal oxide thin films. By forming the porous metal oxide films on both surface of the dense metal oxide base body, deterioration due to short wavelength light such as vacuum UV rays can be prevented while effective antireflection can be obtd. on the surfaces. Therefore, even when the pellicle is to be used for UV rays, especially vacuum UV rays, the inorg. antireflection layers having excellent transmitting property and antireflection performance can be formed and the pellicle has excellent light resistance and transmitting property for UV rays. Moreover, deterioration of the pellicle by light is suppressed and a fine pattern can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pellicle using a pellicle film or plate provided with an antireflection layer of a porous inorganic oxide, and more particularly to lithography using ultraviolet light, particularly vacuum ultraviolet light. A pellicle suitable for

[0002]

2. Description of the Related Art In a photolithography process, a photomask or reticle (hereinafter referred to as a "mask") in which a circuit pattern is formed on a glass plate surface with a vapor-deposited film of chrome or the like is used, and the circuit is formed on a silicon wafer coated with a resist. An operation of transferring the pattern by exposure is performed. In this step, if the exposure is performed in a state where foreign matter such as dust adheres to the circuit pattern on the mask, the foreign matter is also transferred to the wafer and becomes a defective product wafer. In particular,
When exposure is performed by a stepper, there is a high possibility that all chips formed on the wafer become defective, and adhesion of foreign matter to the circuit pattern of the mask becomes a serious problem.
Pellicles have been developed to solve this problem, and various improvements have been made.

[0003] Generally, a pellicle is formed by stretching a transparent film made of a resin such as nitrocellulose on one side of a pellicle frame made of aluminum or the like, and applying a double-sided tape to the other side. It can be mounted on a mask. According to this, it is possible to prevent foreign matter from entering from the outside, and even if foreign matter might adhere to the film, the problem is unlikely to occur because the image is transferred out of focus at the time of exposure.

In the semiconductor process, the wavelength of an exposure light source has been shortened in order to improve the degree of integration by pattern miniaturization, and after the KrF excimer laser (λ = 248 nm) whose market is currently rising, Vacuum ultraviolet region (λ ≦ 2
00 nm), among which the ArF excimer laser (λ = 193 nm) is considered the most promising.

[0005]

A conventional pellicle uses an organic polymer thin film (self-supporting thin film). The organic polymer has a problem that it is easily deteriorated with respect to light having a short wavelength. That is, as the wavelength of the light source becomes shorter, the photon energy increases. For example, in the case of an ArF excimer laser, 6.
It has an energy of 4 eV (= 147 kcal / mol). This energy is equal to the C—C
Since it is sufficiently larger than the bond dissociation energy (104 kcal / mol), a polymer having absorption at the wavelength of the exposure light source easily undergoes photodecomposition by irradiation with the exposure light, and cannot be used as a pellicle film material.

On the other hand, there is a problem that an inorganic material which is less deteriorated with respect to light having a short wavelength has a low transmittance to an organic polymer thin film. That is, in the organic polymer thin film, a high transmittance is realized by using a polymer having low light absorption and utilizing light interference in the form of a thin film.
However, since inorganic materials are brittle, it is difficult to realize a form of a free-standing thin film. Further, in the case of a plate made of an inorganic material, light is reflected on the surface of the plate, so that a high transmittance as in an organic polymer thin film cannot be obtained. Even if an anti-reflection film is formed to suppress light reflection on the surface of the plate, there is no material with an appropriate refractive index as the anti-reflection film, so a high transmittance can be obtained like an organic polymer thin film. Absent.

Accordingly, an object of the present invention is to form an inorganic antireflection layer having excellent transparency and antireflection performance on ultraviolet light, especially vacuum ultraviolet light, on the surface of a base made of a dense metal oxide. As a result, an object of the present invention is to provide a pellicle having excellent light resistance to ultraviolet light and light transmittance.
Another object of the present invention is to achieve a low refractive index required for antireflection by a porous structure of a metal oxide, and further achieve light scattering in an antireflection film by miniaturization of particles forming the porous structure. Is to provide a pellicle. Another object of the present invention is to suppress the photodegradation of the pellicle even when ultraviolet light, particularly vacuum ultraviolet light, is used, and as a result, a sharp and fine pattern is formed stably for a relatively long time by lithography. To provide a pellicle that can be used.

[0008]

According to the present invention, there is provided a pellicle film or plate in which an antireflection layer is laminated on both sides of a base made of a dense metal oxide (a), wherein the antireflection layer is made of a porous metal. A pellicle is provided, which is a pellicle film or plate made of a thin film of the oxide (b). In the pellicle of the present invention: 1. The porous metal oxide (b) thin film has a porosity of 30 to 70%; 2. The pellicle film or plate has a transmittance of 80% or more with respect to vacuum ultraviolet light having a wavelength of 200 nm or less; The dense metal oxide (a) is dense SiO ₂ ,
_{3. the} porous metal oxide (b) is porous SiO ₂ ; The porous metal oxide (b) thin film is formed by a sol-gel method from a metal alkoxide, more preferably, the porous metal oxide (b) thin film is prepared from a metal alkoxide. It is preferably an inorganic porous thin film obtained by applying a solution (sol) to a substrate and subjecting the solution to pressure and heat treatment under supercritical conditions.

[0009]

FIG. 1 shows a sectional structure of a pellicle film or plate used in the present invention.
Consists of a dense metal oxide substrate 2 and antireflection layers 3 and 3 provided on both surfaces of the substrate 2. In the present invention, these antireflection layers 3 and 3 are made of a porous metal oxide. The feature is that a material consisting of

When a dense metal oxide (a) is used as the base of the pellicle film or plate, even when light having a short wavelength such as vacuum ultraviolet light is used, deterioration (thickness of the thickness) due to light such as an organic polymer occurs. (Reduction) and has the advantage of being excellent in light resistance.

On the other hand, such a dense metal oxide (a)
The pellicle film or plate made of has a problem that the light transmittance is lower than that of the organic polymer. That is, as already pointed out, in the organic polymer, high transmittance is realized by utilizing light interference in the form of a thin film. However, the material made of the metal oxide (a) has toughness and elasticity. In this case, it is difficult to use a self-supporting thin film because of lack of light, and high transmittance cannot be obtained because light is reflected on the surface of the plate.

It is a general measure to provide an anti-reflection film on the surface in order to prevent reflection on the surface of the plate, but it satisfies the non-reflection condition for light having a short wavelength such as vacuum ultraviolet light. Since it is difficult to obtain a material having such a refractive index, it is not easy to realize high transmittance even if a general antireflection film is simply provided. That is, in the case of a dense film used as an ordinary anti-reflection film of an optical material, there is a problem that there is no material having a refractive index satisfying a non-reflection condition described later (the refractive index is too large). It is theoretically possible to satisfy the anti-reflection condition by laminating several dense films having different refractive indices. However, if the material is transparent at the wavelength of the excimer laser, an appropriate refractive index can be obtained. Cannot be realized, and the non-reflection condition cannot be satisfied. There is also a problem that the production becomes complicated when the number of stacked films is increased in order to approach the non-reflection condition.

According to the present invention, by providing a porous metal oxide (b) film on both surfaces of a substrate made of a dense metal oxide (a), deterioration by short wavelength light such as vacuum ultraviolet light is prevented. However, it is possible to effectively prevent reflection on the surface, and to realize high transparency to light.

The refractive index of the dense metal oxide (a) changes depending on the wavelength of light. Regarding silica glass (quartz glass), which is a typical example of a dense metal oxide (a) substrate,
The relationship between the wavelength (X, nm) and the refractive index (Y) is represented by the following approximate expression (1): Y = −1.4304 × 10 ⁻¹¹ .X ⁵ + 1.768 × 10 ⁻⁸ .X ⁴ −8.8172 × 10 ⁻⁶ .X ³ + 2.1904 × 10 ⁻³ .X ² -2.7364 × 10 ⁻¹ .X + 1.5350 × 10 (1), and the relationship is shown in FIG. 2 ( In FIG. 2, the points are literature values and the curve is a polynomial approximation).

The optical design of the porous metal oxide (b) satisfying the anti-reflection condition is performed as follows.

Assuming that the refractive index of the dense plate (substrate) is N _fine and the refractive index of the porous film is N _porous , under the non-reflection condition, the following equation (2) is obtained: N _porous = (N _fine) The refractive index of the porous film may be determined so as to satisfy ^0.5 ‥ (2).

The porosity of the porous film is controlled based on the following formula (3) in order to realize the refractive index N _porous of the _porous film given by the above formula (2). . The density of the porous film is ρ _porous , and the density (theoretical density) when the porous film is completely dense is ρ
Then, there is a relationship of P = 1−ρ _porous / ρ ‥ (3), and the porosity when satisfying the non-reflection condition is P = 1 − [｛(N _porous ) ² −1｝ / ｛(N _{porous ^{) 2 +2}] × [{}} (N fine) 2 +2} / {(N fine) 2 -1}] = 1 - {(N fine) 2 +2} / (N fine +2) / (N fine +1) ‥ (4)

The thickness of the porous film is d and the wavelength of the light used is λ (for example, KrF: 248 nm for excimer laser, Ar
F: 193 nm), the relationship between the two under the non-reflection condition is as follows: d = λ / 4 / N _porous = λ / 4 / (N _fine ) ^0.5 ‥ (5) .

The above formulas (2) and (5) are the antireflection conditions of the antireflection film. In the present invention, by forming a porous film satisfying these conditions, it is possible to realize the nonreflection conditions. . Further, as is apparent from the above equations (2), (4) and (5), when the “wavelength of light to be used” and the “refractive index of the dense plate” are determined, the optical design (the anti-reflection film by the anti-reflection film) It is understood that the refractive index, the porosity, and the film thickness of the porous film can be set based on the (reflection conditions). Also, it should be understood that the optical design need only be performed for the porous film, and the thickness may be any as long as the dense plate hardly absorbs light and is transparent.

Now, a porous SiO ₂ film / a dense SiO ₂ plate /
An example of the optical design of the SiO ₂ porous film will be described by using specific numerical values. The wavelength used is 248 nm (KrF) 193 nm (ArF) The refractive index of the dense plate 1.514 1.564 Refractive index 1.230 1.251 Porosity of porous film 51.4% 51.4% Thickness of porous film 50.4 nm 38.6 nm Note) The refractive index in the table is the value at the wavelength used. The value of the refractive index changes with the wavelength (see Fig. 1).

[Pellicle film or plate] As the substrate made of the dense metal oxide (a), a material that does not absorb light at the wavelength of light to be used is used. As the metal oxide (a), Al ₂ O ₃ , HfO ₂ , MgO, Nd ₂ O ₃ , S
_{c 2 O 3, SiO 2,} Y 2 O 3, ZrO 2 or mixed oxides thereof are preferable, considering that absorption of light is especially _{small, Al 2 O 3, MgO,} SiO 2 is particularly preferred, SiO ₂ Is most preferred. Silica (SiO ₂ ) glass is also called quartz glass, and when a transition metal is mixed as an impurity, the transmittance at a short wavelength is reduced. Therefore, a high-purity material must be used in the application of the present invention. In a dense plate through which light passes for a long distance, the influence of impurities is more likely to appear than in the case of a porous film. The content of metal impurities in the silica glass is preferably 1 ppm by weight or less. The thickness of the substrate is not particularly limited, but is generally 0.05 to 10 m.
m, particularly preferably in the range of 0.1 to 5 mm in terms of handling.

On the other hand, as the film made of the porous metal oxide (b), a material that does not absorb light at the wavelength of light to be used is used. As the metal oxide (b), Al
₂ O ₃ , HfO ₂ , MgO, Nd ₂ O ₃ , Sc ₂ O ₃ ,
SiO ₂ , Y ₂ O ₃ , ZrO ₂ or a mixed oxide thereof is preferable, and considering that light absorption is particularly small,
Al ₂ O ₃ , MgO and SiO ₂ are particularly preferred, and SiO _2
2 is most preferred. The antireflection film made of the porous metal oxide (b) can be formed by a sol-gel method described later.

As described above, the characteristics of the antireflection film are determined by the refractive index and the thickness of the film. Among these, the film thickness (d) can be controlled by the film forming conditions, while the refractive index (N
( _porous ) can be controlled by adjusting the porosity ( _ρporous ) of the porous membrane. In the present invention, the porosity of the porous metal oxide (b) film also depends on the refractive index of the dense metal oxide (a), and cannot be specified unconditionally.
It is preferably in the range of 70 to 70%, particularly 40 to 60%. In addition, the thickness of the porous metal oxide (b) is generally determined in a range of 10 to 90 nm so as to obtain a predetermined peak transmittance according to the wavelength of light to be used.

The porosity of the porous film, that is, the relationship between the refractive index and the light transmittance, was measured by using a porous Si film on both sides of a SiO ₂ glass plate having a refractive index of 1.558 for light having a wavelength of 193 nm.
The following is the result obtained when a film having an O ₂ antireflection film is formed. Porous SiO ₂ film SiO ₂ plate with porous SiO ₂ film formed on both sides Porosity (%) Refractive index Peak transmittance (%) Film thickness at peak transmittance (nm) 51.4 1.248 100 38. 7 40.0 1.311 99.5 36.8 30.0 1.370 98.3 35.2 20.0 1.429 96.4 33.8 10.0 10.0 1.492 93.8 32.3

FIG. 3 shows the thickness and the thickness of the porous SiO ₂ film of the SiO ₂ plates having the porosity of 51.4%, 40.0% and 30.0 among the SiO ₂ plates having the porous SiO ₂ films formed on both surfaces. The relationship with the transmittance is plotted and shown. From the above, it is apparent that a high light transmittance can be achieved by setting the porosity of the porous film to a certain range for light of a certain wavelength.

The optical characteristics of the porous metal oxide (b) are desirably low in light absorption and scattering.
Among these characteristics, light absorption may be considered to be negligible for a high-purity metal oxide porous film formed by a sol-gel method, as described later. On the other hand, the light scattering depends on the size of the particles constituting the porous film. That is, in excimer laser applications, since the wavelength of the light used is short, there is a problem that the transmittance is reduced due to light scattering in the porous film. The smaller the size of the particles constituting the porous film, the smaller the light scattering, and the higher the transmittance. Therefore, in an excimer laser application, the size of the particles constituting the porous film is 50 nm or less, particularly 1
It is preferably 0 nm or less.

[Formation of Porous Metal Oxide Film] In order to form a porous metal oxide (b) film on the surface of a dense metal oxide (a) substrate, it Any porous film forming means can be adopted as long as the porosity is within the above range, and preferably, the constituent particles of the coating are within the above range.

Means for forming a porous film on a dense metal oxide substrate such as glass are roughly classified into a method of subjecting a metal oxide substrate such as glass to a surface treatment, and a method of forming a metal oxide substrate such as glass. There are known methods for depositing a film on the surface of the substrate, and these known methods can be applied to the formation of a porous metal oxide film.

As the former method, (1) a phase separation treatment of sodium borosilicate glass and then leaching (elution) with an acid.
(A phase separation leaching method) and (2) a method of treating the glass surface with a neutral solution containing sodium arsenite and aluminum ions (a neutral solution method). However, these methods are not very suitable methods because the glass composition is limited.

On the other hand, as the latter method, a method of forming a porous film on a dense metal oxide substrate using a colloidal dispersion of a metal oxide formed by a sol-gel method or the like, or a method of forming a porous film on a sol-gel method There is a method of further etching the etched film. These methods are preferable because the glass composition is not limited as in the former method and the preparation is easy.

In general, in a system in which fine particles are homogeneously dispersed in a solution, a state having fluidity is called a sol, and a state having lost fluidity is called a gel. The boundary between the sol and the gel is clearly distinguished. It is difficult to do. The sol used in the sol-gel method is a homogeneous solution having a predetermined chemical composition,
A sol in which fine particles of a predetermined composition are dispersed by adding water, an acid or an alkali to cause a chemical change such as hydrolysis, and, if necessary, performing a post-treatment such as evaporation or cooling of a solvent. Is obtained. This sol solution is applied to the surface of the base, dried and heat-treated to form a porous metal oxide (b) film.

Metal alkoxides are particularly suitable as raw materials for forming the sol. The metal alkoxide is a compound represented by the following formula (I) M (OR) mｍ (I) wherein M is a metal, R is an alkyl group, and m is a valence of the metal M. . As the alkyl group, one having 1 to 4 carbon atoms is usually preferable, and a methyl group, an ethyl group, a propyl group and the like are particularly suitable.
In this metal alkoxide, the OR group is easily hydrolyzed. For example, in the case of tetraalkoxysilane, the following formula (I
A metal oxide or hydroxide is formed through a condensation process as shown in I).

In the sol-gel method using a metal alkoxide, 1) since it can be purified by recrystallization or distillation, a high-purity metal alkoxide can be easily obtained. 2)
Since the reaction system finally contains only water and alcohol or more volatile acids or alkalis in addition to metal oxides or hydroxides, the product can be purified and dried by heating without separation from the solution. Metal oxide can be obtained. 3) Since it goes through a condensation process, by setting appropriate hydrolysis conditions, it is possible to control the form, molecular weight or particle size of the condensed molecule, and it is possible to adjust the viscosity of the sol liquid. There is an advantage that a film can be formed in the same manner as an organic polymer.

When an acid or an alkali is used for the hydrolysis, it is preferable that these are volatile in order to avoid contamination by impurities caused by the acid or the alkali. Nitric acid and hydrochloric acid are used as the acid, and ammonia is used as the alkali. The use of water is preferred.

In the case of film formation by a general sol-gel method, taking a description of a tetraalkoxysilane as an example, ethanol, an aqueous ammonia solution and tetraethoxysilane are mixed to prepare a coating solution composed of a SiO ₂ sol.
This coating solution is applied to a substrate, dried at room temperature, and further heat-treated at a temperature of 200 to 1000 ° C.

In the case of etching a film formed by the sol-gel method, a coating solution composed of a sol of SiO ₂ is prepared by mixing ethanol, an aqueous solution of nitric acid and tetraethoxysilane, and the coating solution is applied to a substrate. Dry in dry nitrogen and heat treat in an oxygen stream (temperature 4)
(0.00-500 ° C.), which is etched using hydrofluoric acid, rinsed with water and ethanol, and then dried in air.

The concentration of the metal oxide in the solution used for the sol-gel method is generally in the range of 0.01 to 10% by weight, particularly preferably 0.1 to 5% by weight, from the viewpoint of film forming properties. . When the concentration is lower than the above range, the efficiency of film formation is deteriorated. On the other hand, when the concentration is higher than the above range, the viscosity of the liquid tends to be too high, and the workability of film formation tends to decrease.

The formation of an antireflection film from a solution (sol) prepared from a metal alkoxide can be carried out by a casting film formation method known per se, for example, a spin coating method, a knife coating method, a dip coating method and the like. The solution (sol) is preferably cast on a smooth substrate surface such as a glass plate to form a thin film. The thickness of the formed thin film can be easily changed by changing the solution viscosity, the rotation speed of the substrate, and the like.

In the method for producing a porous metal oxide (b) film of the present invention, the porosity of the porous metal oxide film is maintained in the above-mentioned high range, and the particle diameter of the constituent particles of the porous film is reduced. It is desirable to dry the gel film formed on the substrate by the sol-gel method under supercritical conditions. The supercritical condition is a clear term per se, but generally means a condition at a higher temperature and a higher pressure side than the critical temperature and the critical pressure. In the drying of the film by the sol-gel method, the supercritical condition exists in or around the film. Supercritical conditions are determined by the type of liquid (generally, alcohols) to be used.

When a gel film formed by the sol-gel method is dried under normal pressure, drying shrinkage occurs due to the capillary force of water or a solvent remaining in the gel during the drying process. When the heat treatment is performed, shrinkage further occurs due to bonding between particles and the like, so that the porosity becomes smaller than the porosity required as a porous film for a pellicle. On the other hand, under supercritical conditions, there is no distinction between gas and liquid, so there is no capillary force in the drying process, so there is no drying shrinkage, and the porosity of the porous membrane obtained after drying is extremely large. . Further, there is an advantage that the particle size of the porous film is fine, and light scattering can be suppressed to a low level.

Drying under supercritical conditions generally involves placing a sol-gel film formed on a substrate in a pressurized container such as an autoclave together with a solvent such as alcohol for controlling the atmosphere, and applying compressed nitrogen or the like. While applying pressure to a supercritical pressure using a pressurized medium, heating to a temperature higher than the supercritical temperature of a solvent such as alcohol, and generally maintaining the temperature and pressure for a certain period of time, gradually reducing the pressure to normal pressure while maintaining this temperature Then, if necessary, drying can be carried out under reduced pressure.

[Pellicle and Lithography] The pellicle used in the present invention is obtained by stretching a pellicle film or plate obtained by the above method on one side of a pellicle frame and attaching a double-sided tape to the other side. It can be mounted on a mask. The pellicle frame is not limited to this, but may be made of metal such as aluminum, aluminum alloy, stainless steel, synthetic resin, or ceramic. In order to stretch the pellicle film or plate on the pellicle frame, an adhesive known per se, for example, a fluororesin adhesive is used. According to the structure of the pellicle, foreign matter can be prevented from entering the inside from the outside, and even if foreign matter adheres to the film, it is transferred in a blurred state at the time of exposure, which causes a problem. Hateful.

In order to prevent the generation of dust inside the pellicle, an adhesive substance layer known per se can be formed on the inner surface of the pellicle frame or the inner surface of the pellicle film or plate. That is, if an adhesive layer is provided inside the pellicle frame or film or plate, dust generation from the inside of the pellicle can be prevented, and floating dust can be fixed to prevent adhesion to the mask. It is excellent in that.

In the exposure method of the present invention, the pellicle provided with the pellicle film or plate manufactured by the above-described method is mounted on a photomask or reticle having a circuit pattern formed on the surface of a glass plate by a deposition film of chromium or the like. The circuit pattern is transferred onto the resist-coated silicon wafer by exposure using an ultraviolet exposure light source having a wavelength in the range of 140 to 200 nm. According to the present invention, even when ultraviolet light, particularly vacuum ultraviolet light, is used, a decrease in light resistance due to photodecomposition of the pellicle is small, and as a result, a sharp and fine pattern is stable for a relatively long time by lithography. Can be formed.

[0045]

According to the present invention, even when ultraviolet light, particularly vacuum ultraviolet light, is used, a low refractive index required for antireflection can be achieved by the porous structure of the metal oxide. There is an advantage that the light scattering at the substrate can be achieved by making the particles forming the porous structure finer. Thus, an inorganic antireflection layer having excellent transparency and antireflection performance with respect to ultraviolet light, particularly vacuum ultraviolet light, can be formed on the surface of the substrate made of a dense metal oxide. It has excellent light resistance and light transmittance. In addition, when the pellicle of the present invention is used, ultraviolet light, particularly when vacuum ultraviolet light is used, light degradation of the pellicle is suppressed,
As a result, there is an advantage that a sharp and fine pattern can be stably formed over a relatively long period by lithography.

[0046]

The present invention is further described by the following examples.

[Example 1] Production of SiO ₂ plate coated on both sides with anti-reflection coating with porous SiO ₂ film (1) Preparation of porous production solution Tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ): 2
5.0 g, purified water _{(H 2 O): 37.4ml,} 0.5m
ol / L hydrochloric acid: 1.7 ml was placed in a flask,
Stir for 2 hours. After allowing to stand at room temperature for 14 days, 70 ml of ethanol was added for dilution, followed by stirring at room temperature for 12 hours.

(2) Formation of Porous Film 15 ml of the above solution was dropped on a synthetic silica glass plate of 150 mm × 120 mm (thickness: 1 mm), and the number of rotation was 2300 rpm
A jelly-like film was formed by spin coating at pm and a rotation time of 20 seconds. The same operation was repeated to form jelly-like films on both surfaces of the silica glass plate. After drying at room temperature for one day, it was immersed in ethanol for one day. Set in an autoclave containing ethanol to control the atmosphere,
7.8 MPa (80 kgf / c) at room temperature using compressed nitrogen
m ² ) (supercritical pressure of ethanol 6.3 MPa)
(At least 64 kgf / cm ² ), while keeping the pressure at 7.8 MPa, the temperature was raised to 250 ° C., which is higher than the supercritical temperature (243 ° C.) of ethanol, and the temperature was kept at 250 ° C. after 30 minutes. While maintaining the pressure, depressurize to normal pressure, and further use a vacuum pump to 13 Pa (1.4 × 10 ⁻⁴ kgf / c).
m ² ) and the ethanol was removed. After replacing the inside of the system with dry air and returning to normal pressure, the system was cooled to room temperature and a sample was taken out from the autoclave. Thereafter, a heat treatment was performed at 500 ° C. for 1 hour in dry air using an electric furnace to form a porous SiO ₂ film on both surfaces of the silica glass plate.

The thickness of the formed porous film was 35 nm, 58
The refractive index measured at 9.3 nm (sodium D line) is 1.
214. The transmittance at 193 nm of a silica glass plate having a porous SiO ₂ film formed on both surfaces is 96.
%Met.

(3) Evaluation of laser light resistance ArF excimer laser device L5 manufactured by Hamamatsu Photonics KK
Under the following conditions, an ArF excimer laser having a wavelength of 193 nm was irradiated using 837 to evaluate light resistance. Laser frequency: 100 Hz Laser fluence: 0.1 mJ / cm ² / pulss
e, laser irradiation atmosphere: dry air 19 before laser irradiation and 5000 J / cm ² laser irradiation
When the transmittance at 3 nm was compared, the decrease in transmittance was less than 1%, indicating good laser light resistance.

Comparative Example 1 A pellicle having a film thickness of 0.82 μm was made of an amorphous fluororesin (CYTOP manufactured by Asahi Glass Co., Ltd.) used as a pellicle material for a KrF excimer laser. The transmittance at 193 nm before laser irradiation was 98%. Irradiation with an ArF excimer laser at 5,000 J / cm ^{2 under the} same conditions as in the above example resulted in a 5% decrease in transmittance at 193 nm compared to before irradiation.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sectional structure of a pellicle film or plate of the present invention.

FIG. 2 is a graph showing the relationship between the wavelength of light and the refractive index of silica glass.

FIG. 3 shows the thickness and transmittance of a porous SiO ₂ film having a porosity of 51.4%, 40.0% and 30.0 among SiO ₂ plates having a porous SiO ₂ film formed on both surfaces. 6 is a graph showing the relationship of.

Claims (6)

[Claims] 1. A pellicle film or plate in which an antireflection layer is laminated on both surfaces of a substrate made of a dense metal oxide (a), wherein the antireflection layer is made of a thin film of a porous metal oxide (b). A pellicle, which is a film or a plate. 2. A thin film of porous metal oxide (b) having a thickness of 30
The pellicle according to claim 1, which has a porosity of ~ 70%. 3. The pellicle according to claim 1, wherein the pellicle film or plate has a transmittance of 80% or more for vacuum ultraviolet light having a wavelength of 200 nm or less. 4. The method according to claim 1, wherein the dense metal oxide (a) is dense SiO
₂ , and the porous metal oxide (b) is porous SiO ₂
The pellicle according to any one of claims 1 to 3, wherein 5. The pellicle according to claim 1, wherein the porous metal oxide (b) thin film is formed from a metal alkoxide by a sol-gel method. 6. An inorganic thin film obtained by applying a solution (sol) prepared from a metal alkoxide to a substrate and subjecting the solution to pressure and heat treatment under supercritical conditions. The pellicle according to any one of claims 1 to 5, wherein the pellicle is a porous thin film.