JPH0470750A - Production of dustproof body - Google Patents

Abstract

PURPOSE:To obtain a high ray transmittance by forming a ray transmittable film on the surface of an inorg. substrate, then etching away the inorg. substrate, thereby preventing the sticking of foreign matter and uniformizing the stress in the film. CONSTITUTION:The ray transmittable film which has 0.2 to 10mum film thickness and allows the transmission of 240 to 500nm light at >= 85% average ray transmittance is obtd. by forming an inorg. or dielectric thin film on the inorg. substrate, then etching away the inorg. substrate. Then, the inorg. substrate is etched away and the thin film formed on the surface thereof is made into a single film to obtain the ray transmittable film, by which the damage and deterioration of the film, such as scratch, are prevented without allowing stresses to exist unequally in the film as in the case of film peeling. The high ray transmittance is obtd. in this way. In addition, the adhesion of foreign matter to the thin film which is the case for electrification at the time of peeling is prevented by etching away the inorg. substrate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for removing dust from a photomask or reticle (hereinafter simply referred to as a mask) used in a photolithography process in the manufacturing process of semiconductor devices such as ICs and LSIs. The present invention relates to a dustproof body used to prevent foreign matter from adhering to the present invention, and a method for manufacturing the same.

[Conventional technology]

Using a mask that patterns a circuit with a vapor-deposited light-shielding film of chromium, etc. on the surface of an eagle glass plate during exposure processing in the semiconductor device manufacturing process, this circuit pattern is transferred onto a silicon wafer coated with a photosensitive agent such as resist. Work is being done to

At this time, if exposure processing is performed with foreign matter such as dust attached to the mask, the shadow of this dust will be transferred onto the wafer as it is, resulting in product defects.
This becomes a factor that reduces so-called yield. In particular, in reduction projection exposure processing in which circuit patterns are sequentially transferred onto chip areas on a wafer using a reticle as a mask, the problem of dust adhesion is serious, as it determines the quality of most chips.

Therefore, a transparent dustproof material (pellicle) made of organic or inorganic material such as nitrocellulose is placed at a predetermined distance above the circuit pattern of the mask to prevent dust from directly adhering to the circuit pattern. It has been known.

By the way, the method for forming the dustproof body is to form a thin film of a predetermined thickness on a substrate made of an organic or inorganic material with a smooth surface by a spin code method, etc., and then peel this thin film from the substrate to form a single film. [Problem to be solved by the invention] However, the present invention has the following disadvantages in the method of forming a single film in the prior art. First, when an organic film is formed on the surface of an inorganic substrate such as quartz glass, when the organic film is peeled off, the organic film is easily charged due to friction, and the holding frame is damaged. In addition, when an inorganic film is formed on an inorganic substrate, the inorganic film is more brittle than the organic film. When an inorganic film is formed on an organic substrate, there is a high possibility that it will be damaged during peeling or deteriorate the optical transparency. The surface became rough, and sufficient light transparency could not be ensured.In addition, in both cases, the method of physically peeling off the thin film from the substrate applies stress unevenly to the film, resulting in deterioration of the film quality. The present invention was developed in view of the above points (1), and its purpose is to prevent the adhesion of foreign matter and make the stress within the film uniform, thereby achieving high light transmittance. An object of the present invention is to provide a dustproof body with high light transmittance.

[Means to solve the problem]

The present invention provides a dustproof body including a holding frame attached to a mask and a transparent three-ray transparent film attached to the holding frame, after forming a light-transmitting film on the surface of an inorganic substrate.
The gist of the present invention is to obtain the light-transmitting film by etching away the inorganic substrate.

Here, the inorganic substrate is, for example, a silicon substrate or quartz glass, and the shape of such an inorganic substrate is approximately 100 mm. Preferably it is a flat plate.

Further, as the light-transmitting film grown on the inorganic substrate, perfluoro amorphous resin may be used as an organic film, and silicon oxide may be used as an inorganic film.

Furthermore, as the inorganic film (Li, Na).

K, Cs, Mg, Ca, Sr, B
a, Y, La.

Ti, Zr, Hf, V, Nb, T
a, Cr, Fe.

Co, Ni, Pd, Au, Zn,
Cd, B, AlIn, C, Ge, Sn
, PbNPAsSb, O,
It may contain elements such as S and F or element oxides.

Methods for forming the light-transmitting film on the inorganic substrate include a so-called spin coating method in which a film material in a fluid state is dropped onto the inorganic substrate and coated by rotation, a dipping method in which the inorganic substrate is immersed in a film material liquid, etc. There is.

Moreover, when forming an inorganic film, it can also be manufactured by a sol-gel method using a metal alkoxide as a starting material.

In the sol-gel method, a sol is prepared by dissolving or dispersing fine particles of an organometallic compound such as a metal alkoxide or a metal oxide as a starting material in an appropriate solvent, and then a thin gel film is obtained from this sol, which is then dried. , a method in which the gel thin film is made into a glass-like inorganic film by heat treatment.

In addition, when preparing the above-mentioned sol, a deflocculant or the like may be added as necessary.

Examples of the organometallic compound used in the present invention include tetramethoxysilane (S i (OCH3) A), tetraethoxysilane (S i (OCHs),
Aluminum isopropoxide (A l (OCH[CH3] 2) 3. Titanium isopropoxide (T i (OCR[CH3]
2) -), zirconium propoxide (Zr
Metal alkoxide melons such as (QC3H, ), ) Silicon octylate (S 1 (C? H+ s COO) −
) -aluminum octylate (A I (Cv H
Examples include organic acid metals such as + s COO) 3 ).

Examples of the metal oxide fine particles include silicon oxide fine particles obtained by hydrolysis of the metal alkoxide and silicon oxide fine particles produced by flame hydrolysis of metal chlorides.

Furthermore, the solvent is not particularly limited, and may be any solvent that can be used in a normal sol-gel method. Examples of such solvents include alcohols such as butanol, impropanol, ethanol, and methanol, amides such as formamide and dimethylformamide, aromatic hydrocarbons such as benzene, toluene, and xylene, pentane, hexane, heptane, Aliphatic hydrocarbons such as octane, glycols such as ethylene glycol, diethylene glycol and triethylene glycol, amines such as jetanolamine and triethanolamine, ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, acetone, Ketones such as methyl ethyl ketone, β- such as acetylacetone, benzoylacetone, etc.
Examples include diketones.

The amount of the solvent to be used is not particularly limited, but is preferably in the range of 0.1 to 20 moles per mole of metal constituting the inorganic membrane.

In addition, when adding a catalyst when preparing a sol,
Examples of the catalyst include hydrochloric acid, nitric acid, acetic acid, silicon tetrachloride, hydrofluoric acid, titanium tetrachloride, sodium hydroxide, and aqueous ammonia. The amount of the catalyst added is preferably in the range of 1.0×10 −5 to 1.0 mol per mol of metal constituting the inorganic membrane.

Furthermore, when a peptizing agent is added when preparing the sol, for example, hydrochloric acid, nitric acid, acetic acid, hydrofluoric acid, aqueous ammonia, polyvinyl alcohol, etc. can be used. The amount of such peptizer added is 20% of the sol to be prepared.
It is preferably less than % by weight.

Furthermore, when water is added during the preparation of the sol, the amount of water added is preferably in the range of 0.1 to 20 moles per mole of metal constituting the inorganic membrane.

To prepare a sol, first, fine particles of an organometallic compound or metal oxide are added to a solvent, and the mixture is stirred at a temperature ranging from room temperature to the reflux temperature of the solvent. Further, a solvent is added to the fine particles of the organometallic compound or metal oxide while stirring the particles at a temperature ranging from room temperature to the reflux temperature of the solvent.

In the above process, when adding a deflocculant,
The method of addition is not particularly limited, but it is preferable to add it to the solvent in advance and mix thoroughly.

A spin coating method can be used to form a thin film from the sol obtained as described above. That is, the sol is dropped onto an inorganic substrate such as a silicon substrate or quartz glass, and a thin film layer is formed by spin coating using a spin coater. This thin film layer is dried with hot air or the like. If the desired film thickness cannot be obtained in one treatment, the spin coating and drying may be repeated. Multiple application and drying steps also have the effect of suppressing the occurrence of cracks and the like.

Note that the viscosity of the sol used for film formation is preferably adjusted in advance using an evaporator or the like so that the film formation process can be easily performed.

The thickness of the thin film, i.e., the light-transmitting film, obtained as described above is preferably in the range of 0.2 to 10 μm, particularly preferably in the range of 0.2 to 5.0 μm, and in the range of 240 to 500 μm.
It transmits 85% or more of light of nm in average light transmittance.

Here, the average light transmittance is the average value of peaks and valleys of interference waves of light transmittance occurring between 240 and 500 nm.

It is preferable that the film thickness be even thinner than the above 10 Pm, but in general, if it is less than 0.2 μm, sufficient strength cannot be obtained. However, if there is no problem in terms of strength, On the other hand, the thickness of the film may be 10 μm or more, but considering the increase in optical aberration during exposure, etc.
It is preferable that it is below m. That is, the film thickness is 10μ
m or more, optical aberrations caused by this light-transmitting film may occur during exposure processes using short wavelength light such as excimer lasers, which may interfere with the reproduction of fine patterns on semiconductor wafers during exposure. This is because of their gender.

The specific thickness of the light-transmitting film is selected so that the transmittance is high for the wavelength used for exposure.

In the present invention, it is possible to control the film thickness +i, the deposition time, the concentration of the hydrosilicic acid aqueous solution, etc.

Here, when the thickness of the light-transmitting film is d2, the refractive index is nl, and the wavelength is λ, (where m is an integer of 1 or more), reflection is prevented and the transmittance is the highest. For example, n
, = 1.5, then g! To increase the transmittance of (436 nm), the film thickness d1 is set to 0.87 μm, and to increase the transmittance of excimer laser (248 nm), the film thickness d is set to 0.83 or 2.48 μm.

Here, in order to prevent a decrease in transmittance due to the inability to obtain the desired film thickness or destabilization of transmittance due to fluctuations in wavelength, it is necessary to easily control the film thickness of the light-transmitting film. To do this, as shown in Figure 3, the light-transmitting film 3
Preferably, an antireflection layer 11 is further laminated on the upper layer.

When such an antireflection layer 11 is laminated, the refractive index of the light transmitting film 3 is n5, and the refractive index of the antireflection layer 11 is n5.
2. If the thickness of the antireflection layer 11 is d2, then reflection will be prevented and the transmittance will be the highest if the refractive index and film thickness are selected that satisfy both the formulas: 7n I :n 2 z. Further, the antireflection layer 11 may be laminated on either one side or both sides of the light-transmitting film 3.

The refractive index n1 of the light transmitting film 3 obtained in this way
is 1.4 to 1.6 in the case of an inorganic thin film.

Therefore, n2 ``''%'nl may be obtained by laminating a material having a refractive index of 1.18 to 1.26 as the antireflection layer 11 . Examples of such substances include IL, for example, calcium fluoride (CaF2), perfluoro amorphous resin, and the like.

In order to laminate such a compound, a vacuum evaporation method, a sputtering method, etc. can be used.

In addition, when the antireflection layer 11 has a two-layer structure of a high refractive index layer 12a and a low refractive index layer 12b as shown in FIG. When the refractive index of the index layer 12a is n2, its thickness is d2, the refractive index of the low refractive index layer 12b is nl, and its thickness is d3, (D v'n + = n 2 / n3, ■ d2 = m
If the refractive index and film thickness are selected to satisfy the following three equations: λ/4n2, d3=mλ/4n3, reflection can be completely prevented and high transmittance can be obtained.

Examples of materials for the high refractive index layer 12a include cerium fluoride (CeF3) and cesium bromide (CsBr).
, magnesium oxide (MgO), lead fluoride (PbF2)
Inorganic substances such as

As the material of the low refractive index layer 12b (for example, lithium fluoride (LiF), magnesium fluoride (Mg
F2), inorganic substances such as sodium fluoride (NaF), and organic substances such as perfluoro amorphous resin. Further, the high refractive index layer 12a and the low refractive index layer 12b
A shuttering method, a vacuum evaporation method, or the like can be used to stack the layers.

As a method for etching the inorganic substrate, it is possible to remove the inorganic substrate by etching using an etching solution such as a hydrofluoric acid aqueous solution or a potassium hydroxide aqueous solution. At this time, by controlling the etching solution and etching time, only the inorganic substrate can be etched away without affecting the thin film.

Furthermore, when performing the etching process, the holding frame may be formed simultaneously with the etching process by forming a frame-shaped mask using a photoresist film and etching away only the central portion of the inorganic substrate.

By simultaneously forming the holding frame in this manner, it is possible to maintain high adhesion between the light-transmitting film and the holding frame. In addition, since there is no manual tensioning process, there is no stress deviation in the light-transmitting film.
Uniform light transmittance can be ensured throughout the film.

Dustproof body 1 consisting of a light-transmitting film 3 attached to a holding frame 2
is attached to the mask 4 with double-sided adhesive tape or the like, as shown in FIG. By using the mask 4 whose surface is protected by the dustproof body 1, the shadow of foreign matter such as dust is prevented from being transferred onto the wafer during exposure.

That is, the protected space S constituted by the surface of the mask 4, the inner surface of the holding frame 2, and the inner surface of the light-transmitting film 3,
The structure is such that dust is prevented from directly adhering to the surface of the mask 4. Due to this structure, even if dust adheres to the outer surface of the light-transmitting film 3, the dust shadow will be out of focus, that is, it will become a dead focus, and the dust shadow will not be transferred onto the wafer. .

Note that the dustproof body 1 may be attached to the mask 4 not only on one side but also on both sides.

[Effect]

According to the above-mentioned means, by etching away the inorganic substrate and converting the thin film formed on the surface into a single film to obtain a light-transmitting film, it is possible to unevenly distribute stress within the film as in the case of film peeling. Therefore, damage and deterioration of the film such as cracks can be prevented. For this reason, the film thickness can be reduced to 0, which was difficult with conventional technology.
．． A light transmitting film having an average light transmittance of 85% or more can be obtained with a thickness of 2 to 10 μm and a wavelength of 240 to 500 nm.

Furthermore, by etching away the inorganic substrate, it is possible to prevent foreign matter from adhering to the thin film due to charging during peeling.

In addition, when etching an inorganic substrate, by etching only the central part and simultaneously forming the remaining part as a holding frame, the process can be omitted and the adhesion between the lightning-transparent film and the holding frame can be improved. Can be maintained high. Further, in this case, since there is no manual tensioning process, there is no stress deviation in the light-transmitting film, and uniform light-transmitting properties can be ensured over the entire film.

Example of implementation Embodiments of the present invention will be described below based on the drawings.

[Example 1] FIGS. 1(a) to 1(f) are cross-sectional views sequentially showing a method for manufacturing a dustproof body of the present invention.

First, a silicon substrate 5 constituting the substrate is prepared.The second silicon substrate 5 is obtained by slicing an ingot obtained by a single crystal pulling method to a thickness of 500 μm, and its surface is mirror-finished. is applied. In the following description, for convenience of explanation, the mirror surface side of the silicon substrate 5 will be referred to as the front surface, and the non-mirror surface side will be referred to as the back surface.

The entire surface of the silicon substrate 5 was heated at 1200° C. for 20 hours using a heat diffusion device, etc., and a 1 μm thick silicon oxide layer 6 was grown on both sides of the silicon wafer (see Fig. 1(a). )).

Subsequently, a photoresist solution was spin coated on both sides of the silicon oxide layer 6 using a spin coater and dried with hot air to form a photoresist layer 7 with a thickness of 1 to 10 μm (FIG. 1(b)). .

Next, a light-shielding mask 9 was positioned on the back side of the silicon substrate 5, and ultraviolet rays were irradiated from the outside of the light-shielding mask 9.Then, the decomposable photoresist layer 7 was chemically characterized by the portions irradiated with the ultraviolet rays. The photoresist layer 7 in the irradiated area was removed in the subsequent development step (FIG. 1(C)).

Then, using the photoresist layer 7 remaining from the step explained in FIG. 1(C) as a mask, the exposed portion of the silicon oxide layer 6 is removed using an etching solution such as hydrogen fluoride at 30°C. , the back side of the silicon substrate 5 was exposed (FIG. 1(d)).

Further, the silicon substrate 5 was etched with an aqueous solution such as potassium hydroxide at 50° C. to remove the exposed portion, that is, the central portion of the silicon substrate 5 (Fig. 1(e)
)).

Finally, by removing all the remaining photoresist layer 7, the remaining portion of the silicon substrate 5 is removed from the holding frame 2.
Thus, a dustproof body 1 in which the silicon oxide layer 6 became a single film and became a light-transmitting film 3 was obtained (FIG. 1(f)).

The dustproof body thus obtained has a light transmitting film 3
has a refractive index of 1.50, a film thickness of 1 μm, and a temperature of 248°C.
The transmittance was 98.0%, and the average light transmittance at 240 to 500 nm was 92.0% [Example 2] Tetraethoxysilane (S 1 (OC2H6) j),
A mixture of 1.0 mol of water, 1.0 mol of water, 0.05 mol of nitric acid, and 4.7 mol of isoprobal was stirred at room temperature for 2 hours, left to stand at room temperature to evaporate the solvent, and concentrated until the viscosity was 5 cP. Next, approximately 3.0 ml of the above concentrated solution was dropped onto a silicon substrate with a diameter of 2 inches and a thickness of 0.3 mm. Using a spin coater, the silicon substrate was spun at 11,000 rpm for 60 seconds. A silica sol film was formed on the silicon substrate 5. Then, the silicon substrate on which this film was formed was further dried at 90° C. for 10 minutes in a hot air circulation dryer. A light-shielding mask 9 was positioned on the back side, and ultraviolet rays were irradiated from the outside of the light-shielding mask 9, and the photoresist layer 7 was
The chemical properties were changed depending on the part irradiated with ultraviolet rays, and the photoresist layer 7 in the irradiated part was removed in the subsequent development process (FIG. 1(C)).

Then, using the photoresist layer 7 remaining in the above step as a mask, the exposed portion of the silicon oxide layer 6 is removed with an etching solution such as hydrogen fluoride at 30° C., and the back side of the silicon substrate 5 is removed. It was left exposed (FIG. 1(d)).

Further, the silicon substrate 5 was etched with an aqueous solution such as potassium hydroxide at 50° C. to remove the exposed portion, that is, the central portion of the silicon substrate 5 (Fig. 1(e)
)).

Finally, by removing all the remaining photoresist layer 7, the remaining portion of the silicon substrate 5 is removed from the holding frame 2.
Thus, a dustproof body 1 in which the silicon oxide layer 6 became a single film and became a light-transmitting film 3 was obtained (FIG. 1(f)).

The dustproof body thus obtained has a light transmitting film 3
has a refractive index of 1.53, a film thickness of 1.05 μm, and 24
Transmittance at 80m is 98.1%, 240-500n
The average light transmittance at m was 92.1%. [Example 3] A perfluoro amorphous fluororesin solution with a thickness of 5 wt% was placed on a quartz glass substrate with a diameter of 8 inches and a thickness of 0.5 mm. Drop at 11000 rpm using a spin coater 6
After rotating for 0 seconds to form a perfluoro amorphous fluororesin film, the substrate on which this film was formed was further dried at 170°C for 1 hour in a hot air circulation dryer, and then left to cool. The dust-proof body thus obtained is subjected to etching treatment with an aqueous solution such as hydrofluoric acid to form a single amorphous fluororesin film into a light-transparent film, and the light-transparent film has a refractive index. is 1.34, the film thickness is 1.1 μm, and the temperature is 248°C.
The transmittance at m was 96%, and the average light transmittance at 240 to 500 nm was about 90% [Effects of the Invention] According to the present invention, If, the inorganic substrate is etched away to form a light transmitting film as a single film. This makes it possible to form a single film without unevenly distributing stress within the film as in the case of film peeling, so it is possible to create a light-transmitting film with high transmittance without causing damage or deterioration of the film such as cracks. Obtainable. Also,
By etching away the inorganic substrate, it is also possible to prevent foreign matter from adhering to the thin film due to charging during peeling.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1(a) to (f) are cross-sectional views sequentially showing the method for manufacturing the dustproof body of the present invention, and FIG. 2 shows the dustproof body obtained in this way as a mask. Figure 3 is a cross-section showing a state in which an anti-reflection layer is formed on the top layer of a light-transmitting film, and Figure 4 is a cross-sectional view showing a state in which an anti-reflection layer is formed in multiple layers. . protected space,

Claims (4)

[Claims] (1) In a dustproof body equipped with a holding frame attached to a mask and a transparent light-transmitting film attached to this holding frame, after forming an inorganic or organic thin film on an inorganic substrate,
A dustproof body characterized in that a light transmitting film having a film thickness of 0.2 to 10 μm and transmitting 85% or more of light of 240 to 500 nm at an average light transmittance is obtained by etching and removing the inorganic substrate. Production method. (2) The method for manufacturing a dustproof body according to claim 1, characterized in that, when removing the inorganic substrate by etching, only the central portion of the inorganic substrate is etched, and the remaining frame-shaped portion around the inorganic substrate is used as a holding frame. (3) The method for manufacturing a high light transmittance dustproof body according to claim 1, characterized in that an antireflection layer is laminated on one or both sides of the thin film. (4) The high light transmittance dustproof body according to claim 1, wherein the antireflection layer has a multilayer structure including a first antireflection layer having a high refractive index and a second antireflection layer having a low refractive index. manufacturing method.