JP4458315B2 - Pellicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is used by being fixed to a photomask or reticle (hereinafter referred to as “mask”) used in a photolithography process in the manufacture of a semiconductor integrated circuit or a liquid crystal substrate, and foreign matter such as dust adheres to the mask. In particular, the present invention relates to a dust-free pellicle that prevents dust generated from the pellicle itself and the periphery of the pellicle from adhering to a mask.
[0002]
[Prior art]
The pellicle is formed by sticking a pellicle film made of a transparent thin film to a pellicle frame having a certain width using an adhesive or the like. The pellicle film is a mask at a predetermined distance (pellicle frame height) from the mask. It is positioned above to prevent foreign matters such as dust from adhering to the mask.
[0003]
In the photolithography process, even if foreign matter or the like adheres to the pellicle, the image is not formed on the semiconductor wafer coated with the photoresist. Therefore, by protecting the mask with a pellicle, it is possible to prevent a short circuit or disconnection of the semiconductor integrated circuit due to an image of a foreign substance or the like, and a defect of a liquid crystal display (hereinafter referred to as “LCD”). Manufacturing yield is improved.
[0004]
Further, the pellicle can provide effects such as reducing the number of times the mask is cleaned and extending its life.
[0005]
Both the pellicle for semiconductor and the pellicle for LCD are required to have high transmittance of light for exposure in order to improve throughput in the exposure process. Therefore, an antireflection layer has been provided on one side or both sides of the transparent thin film. The antireflection layer may be composed of a single layer or two or more layers.
[0006]
As the material of the antireflection layer used for the outermost layer, a tetrafluoroethylene-vinylidene fluoride-hexafluoropropylene polymer disclosed in JP-A-61-209449 or a polycrystal disclosed in JP-A-1-100549 is disclosed. Fluoroacrylate, or Teflon AF (trade name) manufactured by DuPont, which is a fluoropolymer having a cyclic structure in the main chain disclosed in JP-A-3-9963, or Cytop (trade name) manufactured by Asahi Glass Co., Ltd. Proposed.
[0007]
Many of the materials for the outermost antireflection layer use fluorine-containing polymers and inorganic fluorine-based materials such as calcium fluoride and magnesium fluoride. Most of transparent thin film layer (center layer) materials use nitrocellulose, cellulose acetate propionate, cellulose derivatives such as carbonated acetylcellulose, and mixtures thereof.
[0008]
In LCDs, TFTs (thin film transistors) are being used to achieve larger screens, higher definition, larger capacities, etc., but pellicles used in TFT-LCD manufacturing have been increased in size and in-plane. There is a demand for uniformity in light transmission, and a pellicle film having a uniform high light transmittance is also required for pellicles for semiconductor manufacturing. Further, there is a need for foreign matter such as micron-order dust from the pellicle itself and its surroundings. There is a need for a pellicle that is not allowed to occur.
[0009]
A pellicle as such a mask protection device is composed of a pellicle frame and a pellicle film attached to one side surface of the pellicle frame with an adhesive, and the pellicle frame is generally anodized. However, if the shape of the aluminum frame is closely observed, there is a risk that foreign matter inside the vent hole may generate dust due to vibration, impact, or air flow inside the vent hole due to a pressure difference.
[0010]
For example, in Japanese Patent Application Laid-Open No. 60-57841, when a thin film of an adhesive substance is provided in advance on the inner surface of a pellicle frame and a minute foreign matter mixed between the pellicle film and the mask floats, A foreign substance fixing method is disclosed in which the fine foreign substances are rendered harmless by adhering them to the aforementioned adhesive substance and fixing them.
[0011]
FIG. 2 is a partial cross-sectional view of a conventional pellicle. A pellicle film 52 is bonded to a pellicle frame 51 with an adhesive 53, and a filter 54 is provided outside a vent hole 51a provided in the pellicle frame 51. The pellicle frame 51 is bonded to the mask 56 with an adhesive 55.
[0012]
[Problems to be solved by the invention]
However, in the above-described conventional example, if foreign matter is generated from the inside of the vent hole 51a due to vibration or impact of transportation or handling after the pellicle is transported or handled and the mask is pasted, or air pressure difference, the minute foreign matter is generated. There was a problem that it could not be harmed.
[0013]
The present invention solves the above-mentioned problems, and the object of the present invention is to remove foreign matter from the inside of the vent hole due to air flow due to vibration and impact of transportation and handling after pellicle transportation and handling and mask attachment, and pressure difference. Is intended to provide a pellicle that does not generate dust.
[0014]
[Means for Solving the Problems]
As a result of diligent research to achieve the above-mentioned object, the present inventors, as a result of observing the surface of the pellicle frame inside the vent hole of the pellicle frame precisely, foreign matter such as alumite dust adheres. Thus, the present inventors have found that there is a risk of falling off due to vibration, impact, and air flow, and that it is easy to generate microscopic suspended matter such as pellicle film and adhesive dust.
[0015]
That is, in the pellicle according to the present invention, a pellicle frame and a pellicle in which a pellicle film is stuck to the pellicle frame with an adhesive are coated with an adhesive material containing a conductive substance inside the vent hole of the pellicle frame. Features. Further, the conductive substance is conductive carbon black or metal powder. Further, the conductive material is charged.
[0016]
Since the present invention is configured as described above, dust is captured by an adhesive material containing a conductive substance applied to the inside of the vent hole of the pellicle frame to transport the pellicle, handle it, transport it after attaching the mask, and handle vibration. Foreign matter is not generated from the inside of the vent due to the flow of air due to impact or pressure difference.
[0017]
Moreover, it is preferable to apply an adhesive on the inside of the pellicle frame. By applying to the inner surface, the mask and the suspended matter in the pellicle frame can be captured by the adhesive.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a pellicle according to the present invention will be specifically described with reference to the drawings. FIG. 1A is a partial sectional view of a pellicle according to the present invention, and FIG. 1B is a front explanatory view showing the periphery of a vent hole of a pellicle frame of the pellicle according to the present invention.
[0019]
In FIG. 1, reference numeral 1 denotes a pellicle frame, and a pellicle film 2 is stuck to the pellicle frame 1 with an adhesive 3. An adhesive material 4 is applied to the inner surface of the vent hole 1a of the pellicle frame 1, and a filter 5 is provided outside the vent hole 1a.
[0020]
Reference numeral 6 denotes an adhesive for attaching the pellicle A to a mask 7 made of a transparent substrate such as a photomask or a reticle (hereinafter referred to as “mask”).
[0021]
The pellicle frame 1 may be made of any material as long as it can support the pellicle film 2. However, the pellicle frame 1 may be made of an aluminum frame whose surface is anodized, a metal frame having a chrome plating, or the like, A resin support frame made of engineering plastic or the like is used, and the shape thereof may be other various shapes such as a square and a circle. Usually, a metal frame is used from the viewpoint of ease of manufacture, strength, and the like.
[0022]
As the transparent thin film layer (center layer) material of the pellicle film 2, cellulose derivatives such as nitrocellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, ethyl cellulose, and carbonated acetyl cellulose can be used.
[0023]
Each of these cellulose derivatives may be used alone, or a mixture with two or more cellulose derivatives may be used. As the cellulose derivative to be used, the higher the molecular weight, the better the shape retention of the thin film.
[0024]
That is, the number average molecular weight is 30,000 or more, preferably 50,000 or more. Of these materials, nitrocellulose is manufactured by Asahi Kasei Kogyo Co., Ltd., cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate are commercially available from Eastman Kodak, respectively. I can do it.
[0025]
As the solvent for the cellulose derivative, 2-butanone, methyl isobutyl ketone, cyclohexanone, butyl acetate, isobutyl acetate, ethyl lactate, cellosolve acetate, propylene glycol monomethyl ether acetate, and a mixed system of these solvents are used.
[0026]
A solution such as a cellulose derivative is filtered in advance for removing foreign substances and then spin-coated. The film thickness of the transparent thin film (center layer) can be appropriately changed by changing the solution viscosity or the rotation speed of the substrate. The solvent contained in the thin film formed on the substrate is volatilized by a hot plate, an oven or the like.
[0027]
The antireflection layer of the pellicle film 2 is composed of a single layer or two or more layers. In the case of a single layer (when the antireflection layer is formed on the front and back, the number of layers of the pellicle film 2 is three), the antireflection layer is used. When the refractive index n1 of the layer is n1 = (nC) ^1/2 with respect to the refractive index nC of the transparent thin film (center layer), the antireflection effect is maximized. The prevention effect is increased. The thickness d of the antireflection layer may be n1 × d = λ / 4, where λ is the wavelength to be antireflection.
[0028]
When the antireflection layer has two layers (if the antireflection layer is formed on the front and back surfaces as in the case described above, the number of layers of the pellicle film 2 is five), the layer in contact with the transparent thin film layer is a high refractive index antireflection layer, The outermost layer is a low-refractive-index antireflection layer. When the refractive index and the thickness are n1, d1, n2, and d2 in order from the outermost anti-reflection layer, antireflection is performed when n2 / n1 = (nC) ^1/2. The effect is maximized, and the antireflection effect increases as the n2 / n1 antireflection layer material close to this value is selected.
[0029]
The thicknesses d1 and d2 of the antireflection layer may be n1 × d1 = n2 × d2 = λ / 4, where λ is the wavelength to be prevented from being reflected. Cellulose derivatives, polyvinyl butyral, polyvinyl propional, and the like can be used for the center layer. In this case, since the refractive index thereof is around 1.5, (nC) ^1/2 is about 1.22. Become. Therefore, as the refractive index of the antireflection layer material, when the antireflection layer is a single layer, it is preferable that n2 / n1 is closer to 1.22, since the antireflection effect is increased.
[0030]
As a material for the low refractive index antireflection layer used as the outermost layer, tetrafluoroethylene-vinylidene fluoride-hexafluoropropylene polymer, polyfluoroacrylate, Teflon AF (manufactured by DuPont, which is a fluoropolymer having a cyclic structure in the main chain) Fluorine-based materials such as trade name) and CYTOP (trade name) manufactured by Asahi Glass Co., Ltd. can be used.
[0031]
Teflon AF is improved in filterability, antistatic properties, and adhesion between the pellicle film 2 and the pellicle frame 1 by irradiating light such as γ-rays, electron beams, α-rays, or light such as far ultraviolet rays.
[0032]
Various adhesive materials can be used as the adhesive material 4, for example, organic materials such as rubber-based, acrylic-based, silicone-based, and polyvinyl ether-based, or inorganic-based materials such as rubber-based organic materials. A system is common, but an acrylic system has heat resistance, a large adhesive force, and does not undergo oxidative deterioration like a rubber system.
[0033]
Silicone type has good heat resistance and high adhesive strength, but because of its high price, rubber type and acrylic type are preferable. Specifically, for example, natural rubber, butyl rubber, SBR (styrene butadiene rubber), CR (chloroprene rubber), NBR (nitrile butadiene rubber), butyl acrylate, PMMA (polymethyl methacrylate), silicone, polyvinyl butyl ether, etc. Is mentioned.
[0034]
The pressure-sensitive adhesive material 4 is composed of a pressure-sensitive adhesive, a tackifier, and an auxiliary material, and the tackifier is a resin that constitutes a main component of the pressure-sensitive adhesive in order to improve tackiness, applicability, durability, and the like. Resins such as rosin, terpene, synthetic petroleum, phenol and xylene are used. As the auxiliary material, a softener, a filler, an antioxidant, a crosslinking agent, a conductive agent, or the like is used as necessary.
[0035]
Examples of the method for applying the adhesive material 4 include a method using an organic solvent, a method using a water-based emulsion, a hot melt, and a reaction system. These are soaked in a stick-like member such as sponge or urethane and applied to the inside of the vent hole 1a. In this way, by applying the adhesive material 4 in the vent hole 1a, foreign matter that enters the vent hole 1a side of the pellicle frame 1 and adheres to the inner surface of the vent hole 1a can be firmly held. It is possible to prevent foreign matter from dropping around the outer periphery of the pellicle A.
[0036]
Examples of the solvent to be used include toluene, hexane, cyclohexane, methylene chloride, ethyl acetate, methyl ethyl ketone, cellosolve, isopropyl alcohol and the like.
[0037]
Moreover, it is preferable that the adhesive material 4 is electroconductive. In order to impart conductivity, a conductive substance such as conductive carbon black or metal powder may be blended as an auxiliary material of the pressure-sensitive adhesive. When the adhesive material 4 is conductive, dust is easily absorbed by charging, and the possibility that foreign matters are separated from the adhesive material 4 for some reason is reduced.
[0038]
In addition, the coating material which is one of the adhesive materials 4 includes oil-based, water-based, resin-based coating materials, general coating materials used for the surface protection and coloring of metals such as pigments, heat conductivity, conductivity, or light rays. Examples include a coating used for adjustment of absorption and reflection, and other special applications. Among them, a conductive material is a preferable example. If the paint is a chargeable substance, dust is easily absorbed by charging, and the absorbed substance may be removed for some reason, but such a problem does not occur with a conductive substance.
[0039]
The adhesive material 8 applied to the inner surface of the pellicle frame 1 is also made of the same material as the adhesive material 4. These are applied by brush, roller, spray, or dipping to form a thin film. By applying the adhesive material 8, foreign matter that has entered the inner depression of the pellicle frame 1 can be contained and prevented from jumping out.
[0040]
The adhesive 3 for adhering the pellicle film 2 to the pellicle frame 1 is preferably an ultraviolet curable adhesive or a thermosetting adhesive.
[0041]
[ Reference example]
A reference example to which the present invention is applied will be described below. First, cellulose acetate propionate (manufactured by Eastman Kodak Co., “CAP482-20”, hereinafter referred to as “CAP”) is dissolved in propylene glycol monomethyl ether acetate to prepare a CAP solution.
[0042]
Next, a solution in which a fluorine-containing resin as an antireflection layer is dissolved in a solvent is prepared. First, the coating substrate is set on a spin coater, the adjusted CAP solution is filtered through a filter, an appropriate amount of the filtrate is dropped onto the coating substrate, and then the coating substrate is placed at 1000 rpm for 45 seconds. Next, the solvent was evaporated with a hot plate, and a transparent thin film layer (center layer) having a thickness of 1 to 2 μm made of CAP was formed on the silicon wafer.
[0043]
Next, the fluororesin solution prepared above is filtered through a filter, and several cc of the filtrate is dropped on the center layer, rotated at 600 rpm for 30 seconds, air-dried, and further dried on a hot plate. Then, an antireflection layer was formed.
[0044]
Next, it is peeled off by a coating substrate under the conditions of 23 ° C. and relative humidity 50%, and further several cc of the fluororesin solution is dropped on the exposed surface of the central layer of the two-layer film peeled off from the substrate, and at 600 rpm for 30 seconds. After rotating, air-dried to form an antireflection layer, and a three-layer film was obtained.
[0045]
Next, using a UV curable adhesive on the upper surface, a three-layer film was adhered to a surface anodized aluminum pellicle frame 1 provided with a thin film of an adhesive material on the inner surface as shown in FIG. . An adhesive material 4 is previously applied to the inside of the vent hole 1a of the pellicle frame 1. The adhesive material 4 was applied by inserting a stick-like urethane soaked with an acrylic adhesive into the ventilation hole 1a.
[0046]
A filter 5 is provided on the outer surface of the vent hole 1a to prevent the entry of dust from the outside and adjust the air flow due to the pressure difference after the mask is attached.
[0047]
The obtained pellicle A did not generate dust during transportation and handling, and was excellent as a dust-free pellicle.
[0048]
【The invention's effect】
Since the present invention has the above-described configuration and operation, foreign matter does not generate dust from the inside of the vent hole due to air flow due to vibration and impact of transportation and handling of the pellicle, handling and attachment of the pellicle, and atmospheric pressure difference. A pellicle can be provided.
[0049]
In other words, dust is captured by the adhesive material containing conductive material applied inside the vent hole of the pellicle frame, and the vibration and impact of transportation and handling after handling the pellicle, handling and masking, and air flow due to pressure difference Foreign matter is not generated from the inside of the vent.
[Brief description of the drawings]
1A is a partial cross-sectional view of a pellicle according to the present invention, and FIG. 1B is a front explanatory view showing the periphery of a vent hole of a pellicle frame of the pellicle according to the present invention.
FIG. 2 is a diagram illustrating a conventional example.
[Explanation of symbols]
A ... Pellicle 1 ... Pellicle frame 1a ... Vent 2 ... Pellicle membrane 3 ... Adhesive 4 ... Adhesive material 5 ... Filter 6 ... Adhesive 7 ... Mask 8 ... Adhesive material

Claims (3)

In a pellicle frame and a pellicle in which a pellicle film is bonded to the pellicle frame with an adhesive, a vent hole is provided in the pellicle frame, and an adhesive material containing a conductive substance is applied in the vent hole. Pellicle. The pellicle according to claim 1, wherein the conductive substance is conductive carbon black or metal powder . The pellicle according to claim 1 or 2, wherein the conductive substance is charged .

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