JP2000147204A - Optical element with protective coat, its production, optical device and semiconductor exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical element with a protective coat less liable to affect the optical characteristics of the optical element and easy to peel by allowing active hydrogen groups on the surface of an optical element to react chemically with reactive groups. SOLUTION: Organic molecules having a fluorocarbon group in at least one end of each molecule and a functional group (reactive group) which reacts with an active hydrogen group in at least the other end are fed to the surface of an optical element 4 and active hydrogen groups on the surface of the optical element 4 are allowed to react chemically with the reactive groups to form a protective coat 6 on the surface. The optical element 4 is a substrate of an optical material such as synthetic quartz or fluorite or a member obtained by forming an optical thin film comprising an oxide such as SiO2, TiO2 or Al2O3, a fluoride such as LiF or CaF2 or a metallic sulfide on the substrate, e.g. a lens, a mirror or a prism having arbitrarily varied optical characteristics. The active hydrogen groups mean -OH (hydroxyl) and -NH- (imino).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a light having a protective film.
Element, method of manufacturing the same, and optical element including the optical element
The present invention relates to an apparatus and a semiconductor exposure apparatus.

[0002]

2. Description of the Related Art With the development of various optical application technologies, the demand for the performance of optical elements is becoming increasingly sophisticated. That is, as a recent trend, for example, optical devices such as a semiconductor exposure device for lithography for printing a fine pattern in a semiconductor device manufacturing process and a laser processing device for fine processing require further miniaturization. The light used in these optical devices is a light having a wavelength shorter than that of visible light, that is, g-line (about 436 nm) and i-line (about 365 nm) of a mercury lamp, and is now a KrF excimer laser light (248n).
m), various excimer laser beams such as ArF excimer laser beam (193 nm), etc., are shifting to shorter and shorter wavelengths.

[0003] In these optical devices, especially semiconductor exposure devices, etc., a slight loss of light due to light absorption leads to a large deterioration of the performance of the device. Existence is not acceptable. In an optical system using a large number of tens of optical elements as in a semiconductor exposure apparatus, even a slight amount of light absorption, light absorption is integrated,
Since the total transmittance is greatly reduced, the amount of exposure light is reduced, and as a result, the throughput is reduced. In addition, even a small amount of light absorption causes a rise in the temperature of the optical element, and the thermal expansion of the optical element due to the rise in the temperature causes not only distortion of the shape but also deterioration of the characteristics of the material.

[0004] Therefore, not only these optical elements but also the optical material substrate must be manufactured so that the optical thin film formed on the surface thereof has a very low light absorption in the ultraviolet region.

[0005]

[Problems to be Solved by the Invention] Optical material substrates such as synthetic quartz and fluorite, SiO ₂ , TiO ₂ , Al ₂ O ₃ , LiF, CaF ₂ , Sr
_{F 2, BaF 2, NaF,} MgF 2, Na 3 AlF 6, AlF 3, GdF 3, NdF 3,
When an optical element with an optical thin film made of oxide, fluoride, metal sulfide, etc. such as LaF ₃ is stored for a long time, this optical element is formed not only on the optical material substrate but also on its surface Even if the optical thin film is manufactured with an extremely low light absorption rate, water, organic substances, and inorganic substances contained in the storage environment adhere to and adhere to the surface of the optical element, thereby causing contamination.
In some cases, even when the optical element is incorporated into an optical device and used for a long period of time, water, organic substances, and inorganic substances contained in the installation environment of the optical element adhere to and adsorb to the surface of the optical element, thereby causing contamination. The dirt causes the optical element to absorb light. The light absorption due to this surface contamination can be eliminated by cleaning the optical element, but frequent cleaning must be performed to maintain the quality of the optical element. As described above, frequent cleaning is a cause of an increase in cost and a decrease in production efficiency.

In order to cope with such a problem, conventionally, a resin film containing carbon fluoride or hydrocarbon is formed as a protective film on the surface of an optical element to reduce the surface free energy due to the carbon fluoride or hydrocarbon film. There is known a method in which water repellency, oil repellency, and stain resistance are imparted to an optical element by utilizing the same. However, the thickness of the above resin film is from several μm to several tens n.
Because of the order of m, the formation of these films affects the optical characteristics of the optical element. This is because these resin films generally have a non-negligible light absorptivity. When light is transmitted through an object having a light absorptivity, a thicker object generally has a higher light absorptivity. That would greatly increase the rate. Further, when a thick resin film is formed on the surface of an optical element provided with an optical thin film such as an antireflection film, this film greatly changes the optical characteristics of the optical thin film. When the optical thin film is an antireflection film, the reflectance is greatly increased, and as a result, the transmittance is reduced.

[0007] Therefore, the resin film is used as a protective film for the optical element.
When using the optical device, the optical element is actually incorporated into the optical device.
When using the product, peel off the protective resin film.
Method and the resin film as an optical thin film
A method of incorporating the element into the outermost layer of the element has been used. Resin film
Formed as a protective film for optical elements and actually used optical elements
The method of peeling the resin film when performing
The resin film must be peeled off without damaging it.
Optical thin film with weak or soft adhesion to material
This is difficult with the formed optical element.

[0008] In addition, deterioration of optical elements during long-term storage
When performing periodic inspections, the resin film that is the protective film is opaque.
It is also inconvenient to be able to check the optical characteristics of the optical element
Therefore, it is the manufacturing period that the protective film is peeled off and re-formed every inspection.
Extension, and thus cost. On the other hand, the resin film
How to incorporate into the outermost layer of an optical element as part of an optical thin film
Is in the visible to ultraviolet range where the absorption of the resin film is not negligible
The optical thin film used is limited by resin material selection.
Problem.

Further, the above-mentioned thick resin film has been produced by coating, wet pulling, spin coating, vacuum evaporation, sputtering, etc., but these require a large-scale apparatus and are complicated in the production process. There is also a problem that it is difficult to form a resin film on an optical element having a complicated shape. Therefore, the present invention is provided with a protective film exhibiting a sufficient anti-staining property that solves the above-described problems and leads to an increase in cost, which requires advanced manufacturing environment management, storage environment management, and process management and frequent cleaning. Provided are an optical element, an optical element having an extremely small influence on the optical characteristics of the optical element, and having an easily peelable protective film, a method of manufacturing the same, and an optical device having the optical element, particularly a semiconductor exposure apparatus. The purpose is to do.

[0010]

[Means for solving the problem] The present invention solves the aforementioned problems.
In order to solve this problem, first of all, "
A functional group that reacts with an active hydrogen group
At the other end of the molecule)
By supplying organic molecules to the surface of the optical element,
The active hydrogen group on the element surface is chemically reacted with the reactive group.
Characterized by comprising a protective film formed on a surface thereof
(Claim 1).

Secondly, there is provided "the optical element according to claim 1, wherein the thickness of the protective film is 10 nm or less." Thirdly, there is provided "the optical element according to claim 1, wherein the protective film is a monomolecular film." Fourthly, the present invention provides “the optical element according to claim 1, wherein the coverage of the surface of the protective film is 1 or less”.

Fifth, "the reactive group is a methoxysilyl group which reacts with an active hydrogen group.
4. An optical element according to any one of claims 4 to 5). Sixth, a method for producing an optical element according to any one of claims 1 to 5, wherein a reactive group having a fluorocarbon group at at least one end of the molecule and reacting with an active hydrogen group is present in the rest of the molecule. A step of arranging the optical element in a space filled with vapors of organic molecules at at least one end of the optical element (claim 6). "

Seventh, "the protective film can be removed by irradiation with light in an ultraviolet region.
An optical element according to any one of claims (Claim 7) "is provided.
Eighthly, there is provided an “optical device comprising the optical element according to any one of claims 1 to 4 (claim 8)”. Ninthly, there is provided a "semiconductor exposure apparatus used in a lithography step of manufacturing a semiconductor device, comprising the optical element according to any one of claims 1 to 4 (claim 9)".

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention achieves the above-mentioned object.
Have a fluorocarbon group on at least one end of the molecule.
And the functional groups that react with the active hydrogen groups
Organic molecules at both ends are applied to the entire surface of the optical element
Supply the active hydrogen groups on the optical element
Group and a chemical reaction between the organic element and the surface of the optical element.
A protective film covered with a fluorocarbon group is produced.

Here, the optical element is an optical material substrate such as synthetic quartz or fluorite, or SiO ₂ , TiO ₂ , Al ₂ O
_{3, LiF, CaF 2, SrF} 2, BaF 2, NaF, MgF 2, Na 3 AlF 6,
A member with an optical thin film made of oxide, fluoride, metal sulfide, etc., such as AlF ₃ , GdF ₃ , NdF ₃ , LaF _3. Representative.

[0016] And active hydrogen groups are -OH (hydroxyl group) and
-NH- (imino group) and the like. The protective film of the present invention
Organic molecules used for
CF on at least one end of child_Three(CF_Two)_n(CH_Two)_m-(N, m is 0
Having a fluorocarbon group such as
A functional group reactive with an active hydrogen group on at least one end of
For example -Si-OCH_Three(Methoxysilyl group), -Si-Cl (chloro
(Silyl group).

[0017] For example, CF_Three(CF_Two)_n(CH_Two)_mSiX_Three-_a(OCH
_Three)_a(N and m are integers of 0 or more, X is H, Cl, an alkyl group,
A fluorocarbon group, a is 1, 2 or 3), such as
Organic molecules are a preferred example. CF_ThreeCH_TwoCH_Two(OCH_Three) CF_ThreeCH_TwoCH_TwoSi (OCH_Three)_Three CF_ThreeCH_TwoCH_TwoSiCH_Three(OCH_Three)_Two CF_ThreeCH_TwoCH_TwoSi (CH_Three)_Two(OCH_Three) CF_ThreeCH_TwoCH_TwoSiCl_Three CF_Three(CF_Two)_FiveCH_TwoCH_Two(OCH_Three) CF_Three(CF_Two)_FiveCH_TwoCH_TwoSi (OCH_Three)_Three CF_Three(CF_Two)_FiveCH_TwoCH_TwoSiCH_Three(OCH_Three)_Two CF_Three(CF_Two)_FiveCH_TwoCH_TwoSi (CH_Three)_Two(OCH_Three) CF_Three(CF_Two)_FiveCH_TwoCH_TwoSiCl_Three CF_Three(CF_Two)₇CH_TwoCH_Two(OCH_Three) CF_Three(CF_Two)₇CH_TwoCH_TwoSi (OCH_Three)_Three CF_Three(CF_Two)₇CH_TwoCH_TwoSiCH_Three(OCH_Three)_Two CF_Three(CF_Two)₇CH_TwoCH_TwoSi (CH_Three)_Two(OCH_Three) CF_Three(CF_Two)₇CH_TwoCH_TwoSiCl_Three Before forming a protective film on the optical element surface,
And a solvent 3 containing the organic molecule and a solvent for forming a protective film.
The elephant optical element 4 is placed in the closed container 2. (Fig. 1)
Optical treatment by UV ozone cleaning or other cleaning methods as pretreatment
By cleaning the surface of the device and activating the active hydrogen groups,
This is preferable because the adhesion between the protective film and the optical element increases. Real truth
In the embodiment, methoxysilyl is used as the organic molecule for the protective film.
Fluorocarbon silane molecules with groups
There is no particular limitation as long as it is a functional group that reacts with the group.
No. Solvent that dissolves organic molecules for protective film is Fluorinert
For active hydrogen groups and protective films like (Sumitomo 3M)
Inert non-polar solvents that do not react with organic molecules are preferred. So
Then, the whole closed container 2 is heated to 50 to 150 ° C. in the heating furnace 1 or the like.
To evaporate the organic molecules for the protective film. As a reactive group
With methoxysilyl or chlorosilyl groups
When using organic molecules for a film, a temperature of 50 to 150 ° C.
It can be reacted with active hydrogen groups at normal pressure. reaction
The condition is that the reactive group of the organic molecule for the protective film is an active hydrogen group.
The temperature and the pressure may be set so as to react with the pressure. However, 20
Be careful as the fluorocarbon begins to decompose at 0 ° C or higher.
is necessary. By the above process, the vapor of organic molecules for the protective film is
The organic molecules that fill the space in the sealed container 2 and are vaporized
The surface of the optical element arrives, and the surface activity of the optical element
Reactive hydrogen groups and reactive groups contained in organic molecules for protective film
Accordingly, a monomolecular film 6 of an organic molecule for a protective film is formed on the surface of the optical element.
Can be formed. (FIG. 2) Put the optical element in the closed container 2
The time should be long enough to complete the reaction.
Methoxysilyl group and halogen
About 2 hours when a silyl halide group is used. However,
Organic molecule film for protective film is formed on the monomolecular protective film
Of the organic molecules for the protective film on the optical element surface
Because the rate at which the membrane is formed is much slower,
The time for keeping the optical element 4 in the vessel 2 must be accurately controlled.
No need.

The organic molecules for the protective film are supplied to the surface of the optical element.
In a container filled with vapors of organic molecules for the protective film
Liquid phase method, without using the gas phase method to dispose the optical element
For example, dipping optical element in organic molecule solution for protective film
Method, spin coating method, vacuum evaporation method, sputtering method, coating method
It is also possible to produce a protective film by a cloth method. I
However, the vapor phase method is filled with the vapor of organic molecules for the protective film
Made simply by placing optical elements in space and heating
The process is simple and requires large equipment compared to other methods.
Not required, complicated shape due to use of gas phase reaction
Excellent in that it is easy to attach a protective film to even optical elements
I have.

In the protective film formed by such a process, the methoxysilyl group at one end of the organic molecule for the protective film is fixed to the surface of the optical element, so that the fluorocarbon group at the other end of the molecule is removed. , On the surface (shown by the broken line) of the optical element. (Figure 2) CaF ₂ , SrF ₂ , BaF ₂ , NaF, Mg
F ₂ etc. or oxides, whereas the surface free energy of the optical thin film such as a sulfide is 200 × 10 ^-3 800 × from ^{N / m 10 -3 N / m} , the solid fluorocarbon group is a surface The surface free energy is from 5 × 10 ⁻³ N / m to 20 × 10 ⁻³ N / m, and the fluorocarbon group is located on the surface side of the optical element. A decrease in surface free energy occurs, and water repellency, oil repellency, and stain resistance can be imparted to the optical element. In addition, an active hydrogen group that greatly contributes to the adsorption reaction can be replaced with an inactive fluorocarbon group, and the adsorption of organic / inorganic molecules that cause contamination can be suppressed. The protective film of the present invention eliminates the need for strict storage environment management and frequent cleaning even when the optical element is stored for a long period of time. Some organic
Since the bonding force between the inorganic molecules and the surface of the optical element is small, dirt can be easily removed simply by wiping with a wiping cloth impregnated with an organic solvent.

The protective film formed in the above steps is a monomolecular film
However, this monolayer always covers the entire optical element.
No need to cover. In other words, the surface of the optical element
If it is a substance, its surface is entirely hydroxylated as shown in FIG.
Since it is covered with base 5, the protective film is an optical monolayer.
Covers the entire surface of the element, but in the optical thin film of the ultraviolet optical element
LiF, CaF used_Two, SrF_Two, BaF_Two, NaF, MgF_Two, Na
_ThreeAlF₆, AlF_Three, GdF_Three, NdF_Three, LaF_ThreeSuch as fluoride, or
Non-oxide compound such as sulfide or sulfide is the outermost surface layer of optical thin film
If used for surface oxidation of these substances, etc.
Therefore, some of the hydroxyl groups are present as organic molecules for the protective film.
Becomes an active hydrogen group 5 to be reacted. (Fig. 2)
Less active hydrogen groups on the surface of these films, so coverage is less than 1.
May be cheaper. However, organic molecule coating for protective film
Even if the ratio is less than 1 and the average film thickness is
Organic molecules for the protective film partially formed on the surface of the
Covers all active active hydrogen groups that greatly participate in the reaction
I have. In this way, the surface of the optical element
Fluorocarbon groups in which the active hydrogen groups that are significantly involved are inactive
Reduces the surface free energy by
Organic and inorganic substances that cause contamination on the optical element surface
Adsorption of molecules can be suppressed. Of course, the light of the present invention
The protective film formed on the element has a thickness of at least a monomolecular film.
However, this does not mean that the protective film has reduced contamination resistance. Only
As described in [Problems to be solved by the invention],
Since the presence of the protective film affects the characteristics of the optical element,
The effect on the optical characteristics of the optical element is smaller as the target film thickness is smaller.
It will be cheap. Therefore, the thickness of the protective film impairs the antifouling property.
The thinner the better, the better.
Geometric film thickness by shortening molecular chains of
Active hydrogen groups that greatly affect the adsorption reaction
Active hydrogen groups are present when partially present on the device surface
Or less than a single molecule that covers only the part
No. For organic molecules with low refractive index and protective film with low light absorption
Choosing organic molecules is also a preferred choice.

Even if the thickness of the protective film is small, the protective film is chemically bonded to the surface of the optical element, so that the protective film is not easily peeled off mechanically, and is not exposed to weak ultraviolet light from a deuterium lamp used in a spectroscope. However, since the chemical bond does not break and does not peel off, it has sufficient durability as a protective film of the optical element. Since the optical element of the present invention has a very thin protective film and its influence on the optical characteristics is very small, when examining the deterioration of the optical characteristics of the optical element during long-term storage of the optical element, the protective film is peeled off. It can be directly measured and inspected with a spectroscope without it.

Since the optical element of the present invention is provided with the protective film having good durability as described above, the optical element is directly incorporated into an optical device such as a semiconductor exposure apparatus without peeling the protective film and used. It is possible. In addition, even after being incorporated into an optical device such as a semiconductor exposure apparatus, the surface of the optical element is inactivated by the protective film, so that water, organic substances, and inorganic substances in the environment in which the optical element is incorporated may adhere and adsorb. The optical element can be kept clean for a long time. Furthermore, depending on the conditions of use of the optical element, it may be desired to remove the protective film and use the optical element. In this case, if a simple method such as irradiation of ultraviolet light having a photon energy sufficient to break a chemical bond, for example, continuous irradiation of ultraviolet light by a UV lamp in the presence of ozone or irradiation of an excimer laser of several J / cm ² is used. Since the protective film is thin, it can be easily removed. The removal of the protective film can be performed on the optical element alone or in a state of being incorporated in the optical element.

Although the embodiments of the present invention have been described above with respect to an optical element having an optical thin film, it is needless to say that the present embodiment is also applicable to an optical element having no optical thin film and comprising only an optical material substrate. No.

[0024]

EXAMPLE An optical element 4 having an optical thin film having MgF ₂ as the uppermost layer formed on the surface was washed with ultraviolet and ozone, and the spectral characteristics of this optical element were measured. Thereafter, the optical element 4 was again washed with ultraviolet and ozone, and the optical element 4 and the solvent 3 containing an organic molecule serving as a material for the protective film were set in the closed container 2.
(FIGS. 1 and 2) In this embodiment, the solvent 3 containing the organic molecule is CF ₃ CH ₂ CH ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₅ CH ₂ CH ₂ Si (OC
H _{3) 3,} was used _{CF 3 (CF 2) 7 CH} 2 CH 2 Si (OCH 3) 3 three 100% solution.

[0025] Then, the entire closed container 2 is stored at 130 to 150
℃, heating in heating furnace 1 for 2 to 4 hours, each organic
A monomolecular protective film 6 corresponding to the molecule is formed on the surface of the optical element.
Was. The spectral characteristics of the optical element on which the protective film was formed were measured.
However, before and after the formation of the protective film, the spectral characteristics of the optical element change significantly.
No transformation was seen. Before attaching the protective film to FIG._ThreeC
H_TwoCH_TwoSi (OCH_Three)_ThreeAfter forming a protective film using
4 shows a change in spectral characteristics (spectral transmittance) of a chemical element. 190n
The drop in transmittance at wavelengths above m is within ± 0.3%
I have. The spectral characteristics of the optical element are large before and after the protective film is applied.
No significant change is seen when the protective film thickness is equivalent to a single molecular thickness
This is because the film thickness is as extremely small as 1 nm or less.

In the protective film formed in such a process, the contact angle of the water droplet was 32 ° in the sample without the protective film, whereas the contact angle of the sample without the protective film was CF ₃ CH ₂ CH ₂ Si (OCH ₃ ) ₃ . CF ₃ (CF ₂ ) ₅ CH ₂ CH
₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OCH ₃ ) ₃ were reacted and the protective films were applied to the samples, respectively.
The angles were as large as 0 ° and 110 °, and generation of water repellency by the protective film was confirmed.

Optical element sample without protective film and CF ₃ CH ₂ CH
_When the optical element samples coated with a protective film with ₂ Si (OCH ₃ ) ₃ and CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OCH ₃ ) ₃ were exposed to air for 4 weeks and stored, Of the transmittance at 193 nm (= the value obtained by subtracting the transmittance at 193 nm after exposure to the atmosphere for 4 weeks from the transmittance at 193 nm before storage and the transmittance at 193 nm after storage) is 4.
1%, optical element sample with a protective film of CF ₃ CH ₂ CH ₂ Si (OCH ₃ ) ₃ 3.3%, protective film of CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OCH ₃ ) ₃ The optical element sample marked with was 1.9%, which was reduced by attaching the protective film. When organic / inorganic molecules, which are contaminants, adhere to and adhere to the optical element, the transmittance of the optical element generally decreases. That is, the fact that the amount of decrease in the transmittance is reduced by providing the protective film means that the contamination is suppressed by the protective film. To support the above, the optical element sample without protective film and CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ S
An optical element sample coated with a protective film using i (OCH ₃ ) _{3 is} stored in the atmosphere for one week, and then stored in an atmospheric pressure ionization mass spectrometer (API-
When the degassing amount from each optical element sample was measured by MS), the degassing amount was smaller in the optical element sample with the protective film. (See FIG. 4. The vertical axis is the ion intensity value proportional to the degassing amount, and the horizontal axis is the temperature of the optical element sample at the time of measurement. The smaller the area between the curve and the horizontal axis in the graph, the smaller the area The amount of degassing is small.) From this, it can be understood that the adhesion of organic and inorganic molecules, which are contaminants, is suppressed by the protective film.

Even if the optical element sample with the protective film becomes dirty, it can be easily removed by simply wiping with a wiping cloth impregnated with an organic solvent, and it is confirmed that the transmittance recovers before the contamination. Was done. CF to remove the protective film
₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OCH ₃ ) _{3 When} a sample with a protective film is irradiated with UV light from a UV lamp in an ozone atmosphere, the contact angle of the water droplet is irradiated in about 15 minutes. From the previous 110 °, the contact angle value before applying the protective film was returned, and peeling of the protective film was observed. (FIG. 5) This is because the thickness of the protective film is extremely thin. With a conventional thick resin protective film, 15
It could not be peeled off with a short irradiation time of minutes.

However, since the protective film is chemically bonded to the surface of the optical element even if the thickness of the protective film is small, the protective film is hardly peeled off mechanically, and does not peel off during normal handling in the manufacturing process. Since the chemical bond is not broken and does not peel off even with a weak ultraviolet light from a deuterium lamp used in a spectroscope, it has sufficient durability as a protective film of an optical element.

[0030] The protective film of the optical element of the present invention is as described above.
It has excellent durability and extremely thin film thickness.
Use an optical element without removing the protective film within the range of durability
It is also possible. In this way, the optical element can be used for a long time.
Water, organic and inorganic substances contained in the environment during use
Can be suppressed from adhering and adsorbing to the surface.

[0031]

【The invention's effect】 The optical element of the present invention reacts with active hydrogen groups.
Organic molecules with functional groups
Supply the active hydrogen groups and reactive groups on the optical element.
Formed by a chemical reaction, the surface of which is an organic molecule of fluorocarbon
With a protective film covered with a base. With this, fluorocarbon
The surface free energy of the optical element
Water and oil repellency and stain resistance to the optical element
Can be done. Also greatly involved in the adsorption reaction
Replace active active hydrogen groups with inert fluorocarbon groups
To prevent the adsorption of organic and inorganic molecules that cause contamination.
Can be obtained.

[0032] Further, the optical element of the present invention has
Strict protective film for long-term storage of optical elements
Storage environment management and frequent cleaning are no longer necessary.
Surface free energy of the UV-visible optical element
-Organic and inorganic molecules that are
Since the bonding strength with the optical element surface is small, the organic solvent
Dirt can be easily removed simply by wiping with the wiped cloth.

Furthermore, in the optical element of the present invention, the protective film
Good durability and thin film thickness for forming protective film
Since the performance deterioration caused by this is extremely small, peel off the protective film.
Directly into an optical device such as a semiconductor exposure device,
And so on. Furthermore, these
Optical devices such as semiconductor exposure devices incorporating optical elements
Is the surface of the optical element even after the
Has been inactivated by the protective film,
Organic and inorganic substances are less likely to adhere and adsorb,
Can be kept clean for a long time, resulting in optical
The optical performance of the device can be kept good for a long time
You. Furthermore, the protective film is removed from the optical element,
When using a child, simple methods such as strong ultraviolet light irradiation
Method, the thickness of the protective film is so thin that it can be easily removed.
It is possible.

Furthermore, in the optical element of the present invention, even if the thickness of the protective film is small, the protective film is chemically bonded to the surface of the optical element, so that the protective film is not easily peeled off mechanically, and the optical element used for a spectroscope is hardly removed. The durability is good because the chemical bond is not broken and does not decompose even with weak ultraviolet light from the hydrogen lamp. In combination with the fact that the protective film of the present invention has a small effect on the optical characteristics of the optical element, deterioration of the optical characteristics of the optical element can be periodically inspected with a spectroscope during long-term storage.

Further, according to the present invention, an optical element having a protective film can be easily manufactured simply by arranging the optical element in a space filled with the vapor of the organic molecule for the protective film and heating.
Compared to the wet pulling, spin coating, vacuum deposition, and sputtering methods, a large-scale apparatus is not required, so that it is inexpensive, and since a gas phase reaction is used, an optical element having a complicated shape can be provided with a protective film.

[Brief description of the drawings]

FIG. 1 is a schematic view of a manufacturing process of an optical element with a protective film of the present invention.

FIG. 2 is a schematic diagram in which an optical element without a protective film (upper part) and an optical element with a protective film (lower part) are enlarged to a molecular level.
This is an example in which CF3 (CF2) 7CH2CH2Si (OCH3) 3 is used as an organic molecule for a protective film.

FIG. 3 is a graph showing a change in spectral characteristics with and without a protective film.

[Fig. 4] API-MS measurement results showing the amount of outgas generated from the sample without the protective film (upper) and the sample with the protective film (lower). The vertical axis represents the ion intensity value proportional to the degassing amount, and the horizontal axis represents the temperature of the sample at the time of measurement. m is the mass number and Z is the charge.

FIG. 5 is a graph showing a change in contact angle of a water droplet when an optical element provided with a protective film is continuously irradiated with ultraviolet rays by a UV lamp in the presence of ozone.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heating furnace of thermostat etc. 2 Airtight container 3 Organic molecule for protective films 4 Optical element 5 Hydroxyl group 6 Protective film 7 Container
8 lids

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2K009 AA00 BB02 BB04 CC03 CC06 CC21 DD03 EE02 EE05 4G059 AA11 AB01 AB11 AC04 AC18 BB01 FA05 FB01 GA01 GA02 GA04 GA16 5F046 AA28 CA04 CB12

Claims (9)

[Claims] An organic molecule having a fluorocarbon group at at least one end of a molecule and a functional group reacting with an active hydrogen group (hereinafter referred to as a reactive group) at at least one end of the molecule is provided on the surface of the optical element. An optical element comprising a protective film formed on the surface by chemically reacting an active hydrogen group on the surface of the optical element with the reactive group when supplied. 2. The optical element according to claim 1, wherein said protective film has a thickness of 10 nm or less. 3. The optical element according to claim 1, wherein said protective film is a monomolecular film. 4. The optical element according to claim 1, wherein a coverage of the surface of the protective film is 1 or less. 5. The optical element according to claim 1, wherein said reactive group is a methoxysilyl group which reacts with an active hydrogen group. 6. A method for producing an optical element according to claim 1, wherein a reactive group having a fluorocarbon group at at least one end of the molecule and reacting with an active hydrogen group is added to the molecule. A method of manufacturing an optical element, comprising: arranging an optical element in a space filled with vapor of organic molecules at at least one end. 7. The method according to claim 1, wherein said protective film is removable by irradiation with light in an ultraviolet region.
Item 6. The optical element according to item 1. 8. An optical device comprising the optical element according to claim 1. 9. A semiconductor exposure apparatus for use in a lithography step of manufacturing a semiconductor device, comprising the optical element according to claim 1.