Frame for pellicle

Abstract

The present invention addresses the problem of providing a frame for a pellicle, the frame being light in weight and excellent in terms of air permeability. A frame (10) for a pellicle according to the present invention has an inner periphery (11) that surrounds a space (13) and contains a porous material in which particles or fibers are bound, and an outer periphery (12) that is positioned opposite to the inner periphery (11). The porous material contains at least one material that is selected from the group consisting of carbon, a metal having a melting point of 1000°C or higher, and a ceramic having a melting point of 1000°C or higher. When the porous material contains carbon or the metal, the frame for a pellicle comprises a coating material that is formed of a ceramic and covers the porous material. The porous material has communicating pores that have air permeability between the inner periphery (11) and the outer periphery (12).

Description

Pellicle Frame

[0001] The present invention relates to a frame for a pellicle.

[0002] In photolithography using ultraviolet light and photoresist, the presence of dust on the mask pattern prevents accurate exposure. Therefore, a dustproof cover (pellicle film) is required to prevent dust from entering the mask pattern, and the frame that supports this is called a pellicle frame. Pellicle frames can be made of metal, but for high-heat-resistant pellicles (for EUV applications), materials such as carbon, silicon, and ceramic are also used. Furthermore, to ensure breathability, Patent Document 1 discloses the use of breathable ceramics, Patent Document 2 discloses the use of porous materials, and Patent Document 3 discloses the provision of ventilation holes.

[0003] JP-A-4-190355 JP-A-4-196117 JP-A-2023-151129

[0004] Conventional pellicle frames have the following issues. First, they need to be lightweight. Although bulk alumina has a specific gravity of 2.7, the stage carrying the frame moves at high speed, so further weight reduction is required. Second, they require processing time and effort; holes must be drilled in the body to ensure ventilation.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a frame for a pellicle that is lightweight and has excellent breathability.

[0006] The present invention includes the following aspects: [1] A pellicle frame comprising a porous material to which particles or fibers are bound, the pellicle frame having an inner periphery surrounding a space and an outer periphery extending in relation to the inner periphery, the porous material comprising at least one selected from the group consisting of carbon, a metal having a melting point of 1000°C or higher, and a ceramic having a melting point of 1000°C or higher, and when the porous material comprises carbon or a metal, the porous material further comprises a coating material made of ceramic that coats the porous material, the porous material having continuous pores that are air-permeable between the inner periphery and the outer periphery. [2] The pellicle frame is characterized in that the air permeability between the outer periphery and the inner periphery of the pellicle frame is 0.1 to 50 cm ３ / cm ２ [3] The pellicle frame according to [1], characterized in that the density of the pellicle frame is 0.1 to 2.1 g / cm ３ [4] The pellicle frame according to any one of [1] to [3], characterized in that the porosity of the pellicle frame is 5 to 95%. [5] The linear expansion coefficient of the porous material is 0.8 × 10 －６ ~3.2 × 10 －６ [6] The pellicle frame according to any one of [1] to [4], characterized in that the porous material is coated with a coating material having a thickness of 0.001 μm to 1 μm. [7] The pellicle frame according to any one of [1] to [6], characterized in that the porous material is coated with a coating material having a volume ratio of 0.1 to 10% by volume of the coating material relative to the true volume of the porous material.

[0007] According to the present invention, it is possible to provide a pellicle frame that is lightweight and has excellent breathability.

[0008] 1 is a cross-sectional view showing an example of a pellicle frame, and FIG. 2 is a micrograph showing an example of a porous material made of carbon.

[0009] The present invention will be described below based on preferred embodiments.

[0010] 1, the pellicle frame 10 of this embodiment has an inner periphery 11 that surrounds a space 13 and an outer periphery 12 that faces the inner periphery 11. Also, between the inner periphery 11 and the outer periphery 12, there is an upper surface 14 on which a pellicle 21 is supported. A lower surface 15 opposite the upper surface 14 may be in contact with a mounting surface 22 on which the pellicle frame 10 is mounted.

[0011] The space 13 inside the pellicle frame 10 is surrounded at the top and bottom by a pellicle 21 and a mounting surface 22. The mounting surface 22 may be the surface of a substrate to be processed by photolithography, or the surface of a table or device on which the substrate is placed. The planar shape of the pellicle frame 10 is not particularly limited, but examples include a polygon such as a rectangle, a circle, an ellipse, etc.

[0012] The pellicle frame of this embodiment includes a porous material in which particles or fibers are bonded. Because it is a porous material, it can be lighter than bulk materials. To ensure the heat resistance of the pellicle frame, the porous material includes at least one selected from the group consisting of carbon, a metal with a melting point of 1000°C or higher, and a ceramic with a melting point of 1000°C or higher. Carbon does not exhibit a melting point below 1000°C, does not exhibit a melting point even at 1000°C or higher at atmospheric pressure, and sublimes at temperatures above 3000°C. Therefore, even without specifying the melting point of carbon, it is possible to ensure heat resistance equivalent to or superior to that of metals or ceramics with melting points above 1000°C. The melting points of the metals or ceramics are not particularly limited, and may be 1500°C, 2000°C, 2500°C, 3000°C, 3500°C, etc. (temperatures above or below these temperatures). Furthermore, the porous material has continuous pores that allow air to pass between the inner and outer peripheries. Since the pellicle frame is porous and breathable, breathability can be achieved without drilling holes.

[0013] When the porous material contains carbon or metal, a ceramic coating material is included to cover the porous material. By applying a ceramic coating to the surface of carbon or metal, durability against hydrogen radicals can be ensured. When the porous material is made of ceramic, the coating material may be omitted.

[0014] Porous materials are produced by bonding particles or fibers. When the aspect ratio is the ratio of the large diameter to the small diameter, particles may be fragments with an aspect ratio of 3 or less, and fibers may be fragments with an aspect ratio of more than 3. In this case, the small diameter and large diameter are defined as the smallest value and the largest value of the distance between two parallel lines tangent to the outline of a particle or fiber that can be observed from a direction perpendicular to the horizontal plane when the particle or fiber is placed most stably on a horizontal plane.

[0015] The particle diameter of the particles used in producing the porous material can be 0.01 to 500 μm. In the case of fibers, the small diameter can be 0.01 to 1000 μm, and the large diameter can be 0.03 to 3000 μm. Coarse particles with larger particle diameters and fine particles with smaller particle diameters may be included. If necessary, the particle size distribution of the particles can be adjusted by sieving or the like. Fragments with large particle diameters and fragments with small particle diameters can be mixed to adjust the particle size distribution to have two or more peaks, or to have one peak.

[0016] The method for producing the porous material is not particularly limited, but examples thereof include a method of binding particles or fibers made of a predetermined material. The predetermined material before binding may be a material of the same quality as the porous material, or a material different from the porous material.

[0017] When the porous material is composed of carbon, methods include (1) bonding carbon particles or fibers, (2) bonding organic particles or fibers and then carbonizing the organic material, and (3) bonding carbon particles or fibers with a resin binder and then carbonizing the resin binder. Organic materials can be synthetic materials such as synthetic resins and synthetic fibers, or natural materials such as sawdust and rice husks. Examples of carbon include graphite, amorphous carbon, and carbon nanotubes (CNTs). Compared to metals or ceramics, carbon is superior in terms of light weight (low density), productivity (low sintering temperature), and cost. Figure 2 shows a micrograph of an example of a porous material composed of carbon. This example was obtained by bonding carbon particles.

[0018] When the porous material is made of metal, examples of methods include (1) bonding metal particles or fibers, (2) bonding metal compound particles or fibers and then converting the metal compound to metal, and (3) bonding metal or metal compound particles or fibers with a resin binder and then carbonizing the resin binder. Examples of metal compounds include metal oxides, hydroxides, and carbonates. Examples of metals include gold, copper, iron, tungsten, and titanium.

[0019] When the porous material is composed of ceramic, examples of the method include (1) a method of binding ceramic particles or fibers, (2) a method of binding ceramic precursor particles or fibers and then converting the ceramic precursor into ceramic, and (3) a method of binding ceramic or ceramic precursor particles or fibers with a ceramic precursor binder and then converting the ceramic precursor into ceramic.

[0020] When providing a ceramic coating, the porous material may be treated with a paint containing ceramic particles, etc., or may be treated with a paint containing a ceramic precursor, etc. Examples of treatment methods using a paint include applying, spraying, and immersing the paint on the porous material.

[0021] Ceramic precursors used in binders, particles, or fibers include clay minerals, organometallic compounds, polymeric compounds, metal salts, etc. Ceramics used in particles or fibers, or produced by conversion from binders, include aluminum oxide (alumina), magnesium oxide, titanium oxide, zirconium oxide, silicon oxide (silica), silicon carbide, etc.

[0022] The air permeability between the outer periphery and the inner periphery of the pellicle frame made of a porous material is 0.1 to 50 cm ３ / cm ２ The value of the air permeability is preferably set to suppress swelling or depression of the pellicle membrane due to the difference in air pressure between the space surrounded by the pellicle frame and the external space, and may be set from the viewpoint of the mechanical strength, heat resistance, handleability, weight reduction, etc. of the pellicle frame.

[0023] The method for measuring the air permeability of a pellicle frame made of a porous material is not particularly limited, but an example is Method A (Fragile method) of JIS L 1096 (Testing methods for woven and knitted fabrics).

[0024] The density of the pellicle frame made of a porous material is 0.1 to 2.1 g / cm ３ The density value may be set from the viewpoint of the mechanical strength, heat resistance, ease of handling, weight reduction, etc. of the pellicle frame.

[0025] The method for measuring the density of a pellicle frame made of a porous material is not particularly limited, but the volume of the entire pellicle frame including voids can be calculated as V (cm ３ ), the mass of the pellicle frame is M (g), and the density d (g / cm ３ ) is required.

[0026] The method for measuring the volume V of the entire pellicle frame made of a porous material is not particularly limited, but examples include a method of calculating it from the general shape of the pellicle frame, a method of measuring the volume of a sample that has blocked the voids, and a method of immersing it in a liquid such as mercury that does not easily penetrate the voids.

[0027] The porosity of the pellicle frame made of a porous material is preferably 5 to 95%. The porosity value may be set from the viewpoint of the mechanical strength, heat resistance, handleability, weight reduction, etc. of the pellicle frame.

[0028] The porosity of a pellicle frame made of a porous material is expressed as v1 / V, where V is the volume of the entire pellicle frame including the voids, v1 is the volume of the voids, and v2 = V - v1 is the volume excluding the voids. When expressed as a percentage, the porosity (%) can be calculated by (v1 / V) x 100 (%).

[0029] If the true density ρ of a porous material is known, the volume of the porous material excluding voids (v2 = V - v1) can be calculated from the ratio of the mass M of the porous material to the true density ρ. From V - v1 = M / ρ, the porosity (v1 / V) = 1 - M / (V × ρ) = 1 - d / ρ.

[0030] The linear expansion coefficient of the porous material is 0.8 × 10 －６ ~3.2 × 10 －６ / K. The value of the linear expansion coefficient may be set in consideration of the mechanical strength, heat resistance, handleability, etc. of the pellicle frame. When the pellicle frame supports a pellicle membrane made of carbon nanotubes (CNTs), damage to the pellicle membrane due to dimensional changes caused by temperature changes can be suppressed by matching the linear expansion coefficients of the pellicle frame and the pellicle membrane.

[0031] When the pellicle frame includes a coating material that covers the porous material, the thickness of the coating material is preferably 0.001 μm to 1 μm. The thickness value may be set from the viewpoints of the protective function of the porous material, ensuring breathability, cost, productivity, etc.

[0032] When the pellicle frame includes a coating material that covers the porous material, the volume ratio of the coating material to the true volume of the porous material is preferably 0.1 to 10%. The value of the volume ratio may be set from the viewpoints of the protective function of the porous material, ensuring breathability, cost, productivity, etc.

[0033] The present invention has been described above based on preferred embodiments, but the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0034] The present invention will be specifically described below with reference to examples.

[0035] (Example 1 of a Pellicle Frame) Carbon particles with a particle size of 10 μm were dispersed in polyimide varnish (active ingredient: 30%, solvent: cyclohexanone) to prepare a slurry. The mixture ratio of particles:binder:solvent (cyclohexanone) in the slurry was 3:1:1. The slurry was poured into a silicone resin mold and dried at 60°C for 24 hours to form the polyimide resin with dispersed carbon particles into a frame-shaped block. The block removed from the mold was placed in a vacuum or nitrogen atmosphere oven, heated to 1000°C over 2-3 hours, and held at 1000°C for 1 hour to carbonize the polyimide, yielding a porous carbon frame. A ceramic coating was applied to the frame to impart hydrogen radical resistance, resulting in a pellicle frame. Silicon carbide (SiC) was used as the ceramic coating.

[0036] The silicone resin mold was prepared by mixing and stirring a two-component curing rubber (manufactured by Shin-Etsu Chemical Co., Ltd., base agent: KE1316, curing agent: CAT1316) into a master mold made by cutting aluminum, and then curing it at 60°C for 12 hours. The SiC coating was prepared by impregnating a porous body with a coating material prepared by adding toluene to a polycarbosilane solution (manufactured by Starfire Systems, SMP-10, 30% toluene solution) and diluting it to 3%, and then evaporating the toluene at 60°C for 1 hour. After that, the polycarbosilane was converted to SiC in a nitrogen atmosphere at 1000°C for 1 hour.

[0037] (Comparative Example 1 of Pellicle Frame) A carbon frame was obtained using a bulk carbon material. In order to impart hydrogen radical resistance to the frame, a ceramic coating was applied to the frame in the same manner as in Example 1, to obtain a pellicle frame.

[0038] (Comparative Example 2, Examples 2-3, and 6 for Pellicle Frames) A ​​porous metal frame was produced and coated with ceramic in the same manner as in Example 1, except that a slurry containing polyimide varnish was prepared using metal particles instead of carbon particles. The metals used were silver (Ag) in Comparative Example 2, copper (Cu) in Example 2, titanium (Ti) in Example 3, and tungsten (W) in Example 6.

[0039] (Examples 4 and 5 of Pellicle Frames) Ceramic particles were dispersed in water glass (aqueous sodium silicate solution) to prepare a slurry, which was poured into a mold and dried. After that, it was heated at 1000°C for 1 hour to convert the sodium silicate into silicon dioxide, thereby obtaining a porous ceramic frame, which was used as a pellicle frame. In Example 4, aluminum oxide (Al ２ O ３ In Example 5, magnesium oxide (MgO) was used.

[0040] (Comparative Example 3 of Pellicle Frame) The ceramic coating was omitted, and the porous carbon material frame of Example 1 was used as a pellicle frame as it was.

[0041] (Comparative Example 4 of Pellicle Frame) A pellicle frame was prepared by applying a resin coating to a porous carbon material frame prepared in the same manner as in Example 1. The resin coating was formed by adding methyl ethyl ketone to epoxy resin to prepare a 3% solution, impregnating the porous carbon material with the resin solution obtained, vaporizing the methyl ethyl ketone, drying, and then heat-treating at 100°C for 20 minutes.

[0042] (Examples 7 to 12 of Pellicle Frames) As shown in Table 3 below, except for changing the particle diameter of the carbon particles, a porous carbon material frame was prepared in the same manner as in Example 1, and a ceramic coating was applied to form a pellicle frame.

[0043] (Pellicle Frame Examples 13 to 18) Pellicle frames were prepared by preparing porous carbon material frames and applying a ceramic coating in the same manner as in Example 1, except that the coating thickness was changed as shown in Table 4 below. The thickness of the ceramic coating was adjusted by appropriately adjusting the paint concentration and the number of impregnations. To reduce the coating thickness, the paint concentration was diluted accordingly. To increase the coating thickness, the number of impregnations was increased to two or more times as necessary.

[0044] (Evaluation of Lightweightness of Pellicle Frames) Because the pellicle frame supporting the pellicle moves at high speed during patterning, it is preferable that the pellicle frame be lighter. For this reason, the lightness was evaluated based on the mass reduction rate W (%) relative to a bulk body of the same material. Specifically, the mass reduction rate W was calculated using the formula W = 100 × (mass of bulk body - mass of porous body) / mass of bulk body. A: 5% ≦ W B: 2% ≦ W < 5% C: W < 2% <Method for measuring the mass of bulk body> The mass of a bulk body to be compared with a sample porous body was calculated by measuring the dimensions and mass of the porous body and assuming it to be a bulk body of the same material and dimensions.

[0045] (Evaluation of Gas Replacement Property of Pellicle Frame) During patterning, the atmosphere inside the pellicle frame supporting the pellicle needs to be replaced with an inert gas. For this purpose, the air permeability X (cm) was measured by the following measurement method in accordance with Method A (Fragile method) of JIS L 1096 (Testing Method for Woven and Knit Fabrics). ３ / cm ２ The gas displacement was evaluated by the following formula: A: 0.1 cm ３ / cm ２ ・s≦X B:0.05cm ３ / cm ２ ・s≦X<0.1cm ３ / cm ２ ・s C:X<0.05cm ３ / cm ２・s <Air permeability measurement conditions> Air was sucked in until the internal pressure reached 125 Pa, and the air flow rate resulting from the difference with the external pressure (atmospheric pressure) was measured. A 40 mm diameter air hole was selected for the Frazier tester. A tester conforming to Method A (Fragile method) of JIS L 1096 (Testing Methods for Woven and Knit Fabrics) was used. The sample was placed on a stainless steel plate with holes so that the holes were completely hidden, and the air permeability was measured. (1) Preparation of Stainless Steel Plate: A stainless steel plate (100 mm long, 100 mm wide, 0.5 mm thick) with a 10 mm x 10 mm through-hole in the center of the plate, as viewed vertically, was prepared. (2) Preparation of Test Piece: A test piece of a size that fully covers the through-hole was cut from one side of the pellicle frame, which was the measurement sample. A test piece was cut out so that the inner and outer peripheral surfaces of the frame could be positioned above and below each other, allowing for measurement of the air permeability between the inner and outer peripheries of the frame. If a sufficient size cannot be obtained, the individual pieces may be joined together with adhesive or the like to a size that covers the through-holes. In this case, by bonding the individual pieces together on surfaces parallel to the air permeation direction, a test piece of sufficient size for measurement can be obtained without changing the sample's vertical air permeability. (3) Setting the stainless steel plate: The stainless steel plate prepared in (1) above is set so that the through-holes of the plate are centered in the air hole of the Frazier tester. (4) Setting the test piece: The test piece prepared in (2) above is placed on the stainless steel plate so that the through-holes of the stainless steel plate set in (3) above are completely hidden. (5) Measuring air permeability: The clamp is tightened, and the air permeability is measured in the same manner as in JIS.

[0046] (Evaluation of Heat Resistance of Pellicle Frames) During patterning, the temperature of the pellicle frame rises due to plasma irradiation of the pellicle. For this reason, it is required that the shape of the pellicle frame remains stable even at high temperatures. Therefore, the pellicle frame was operated at a constant temperature in an inert atmosphere in an electric furnace, and the shape after heating for one hour was observed to evaluate the heat resistance from the shape retention rate. A: At a furnace temperature of 1500°C, the "shape retention rate = B / A" is 0.9 or more. B: At a furnace temperature of 1000°C, the "shape retention rate = B / A" is 0.9 or more. C: At a furnace temperature of 1000°C, the "shape retention rate = B / A" is less than 0.9. <Measurement Procedure> (1) Pre-heating Measurement: If the shape change of the pellicle frame upon heating is small, any point on any side can be selected. However, in this evaluation, a height (distance between the upper surface 14 and the lower surface 15) was selected so that the "shape retention rate = B / A" could be measured even if the sample melted during heating. This single point was measured with a vernier caliper to obtain the "height A of the pellicle frame before heating." (2) Sample Installation: The pellicle frame was positioned so that its inner and outer peripheral surfaces were perpendicular to the installation surface within the electric furnace (see Figure 1). (3) Sample Heating: The electric furnace containing the pellicle frame was purged with an inert gas (such as nitrogen) and operated at a constant temperature of 1000°C for one hour. (4) Post-heating Measurement: After one hour of heating, the sample was returned to room temperature and removed. The height of the pellicle frame after heating was measured with a vernier caliper in the same manner as in (1) above to obtain the "height B of the pellicle frame after heating." (5) Confirmation of dimensional change: Using the values ​​obtained in (1) and (4) above, calculate "shape retention rate = B / A". (6) Judgment and evaluation: If the value "B / A" obtained in (5) above is less than 0.9, it is rated as C, and if it is 0.9 or more, it is rated as B. Furthermore, for the samples where the constant operating temperature in (3) above was 1500°C, if the "shape retention rate = B / A" is 0.9 or more, it is rated as A.

[0047] (Evaluation of Plasma Resistance of Pellicle Frame) During patterning, the pellicle is irradiated with plasma, which also exposes the pellicle frame to plasma irradiation. For this reason, plasma resistance is required for the pellicle frame. Plasma resistance was evaluated based on the mass reduction rate Z (%) of the entire pellicle frame before and after plasma irradiation under the following plasma irradiation conditions. Specifically, the mass reduction rate Z (%) was calculated using the formula Z = 100 × (mass before plasma irradiation - mass after plasma irradiation) / mass before plasma irradiation. A: 6% ≧ Z B: 10% ≧ Z > 6% C: Z > 10% <Plasma irradiation conditions> High-frequency power output: 1000 W High-frequency power frequency: 13.56 MHz Bias power output: None Vacuum level: 300 mTorr (= 40 Pa) Gas flow rate: Oxygen 400 sccm, carbon tetrafluoride 200 sccm Irradiation time: 10 hours Temperature: 25°C

[0048] (Evaluation of workability of pellicle frames) When assembling a pellicle onto a pellicle frame or during patterning, it is required that the pellicle frame supporting the pellicle can be handled without any problems. For this reason, when handling the pellicle frame, the pellicle frame was qualitatively evaluated based on whether it was damaged or generated dust when it was subjected to impacts that occurred when supporting and assembling the pellicle film or when it landed on the installation surface inside the etcher. A: Not easily damaged and did not generate dust. B: Not easily damaged, but generated dust. C: Easily damaged.

[0049] (Evaluation Results) The above results are shown in Tables 1 to 4. In these tables, when the material was carbon (C), the sublimation point was shown in the melting point (° C.) column.

[0050]

[0051]

[0052]

[0053]

[0054] In Examples 1 to 18, the results of all five of the above evaluations (lightweightness, gas displacement, heat resistance, plasma resistance, and workability) were A (excellent) or B (good). For the overall evaluation, if all five evaluations were A, the overall evaluation was A, and if one or more evaluations were B, the overall evaluation was B. In Comparative Examples 1 to 4, the results of one or more evaluations were C (fail), so the overall evaluation was also C. In Comparative Example 1, the light weight and gas displacement were C (fail). In Comparative Example 2, the heat resistance was C (fail). In Comparative Examples 3 and 4, the plasma resistance was C (fail).

[0055] According to the present invention, it is possible to provide a pellicle frame that is lightweight and has excellent breathability.

[0056] 10... pellicle frame, 11... inner periphery, 12... outer periphery, 13... space, 14... upper surface, 15... lower surface, 21... pellicle, 22... installation surface

Claims

1. A pellicle frame comprising a porous material to which particles or fibers are bonded, having an inner periphery surrounding a space and an outer periphery opposite to the inner periphery, wherein the porous material comprises at least one selected from the group consisting of carbon, metals with melting points of 1000°C or higher, and ceramics with melting points of 1000°C or higher, and when the porous material comprises carbon or metal, a coating material made of ceramic that covers the porous material is included, and the porous material has continuous pores that are breathable between the inner periphery and the outer periphery.

2. The air permeability between the outer periphery and the inner periphery of the pellicle frame is 0.1 to 50 cm ３ / cm ２ 2. The pellicle frame according to claim 1, wherein the thickness of the pellicle frame is s.

3. The density of the pellicle frame is 0.1 to 2.1 g / cm ３ 2. The pellicle frame according to claim 1, wherein:

4. A pellicle frame according to claim 1, characterized in that the porosity of the pellicle frame is 5 to 95%.

5. The linear expansion coefficient of the porous material is 0.8 × 10 －６ ~3.2 × 10 －６ 2. The pellicle frame according to claim 1, wherein the thickness of the pellicle frame is 1 / K.

6. The pellicle frame according to claim 1, further comprising a coating material that covers the porous material, the coating material having a thickness of 0.001 μm to 1 μm.

7. A pellicle frame as described in claim 1, characterized in that it includes a coating material that covers the porous material, and the volume ratio of the coating material to the true volume of the porous material is 0.1 to 10%.

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