HK1211089B - Adhesive for anti-dust pellicle assembly and anti-dust pellicle assembly employing the same - Google Patents

Description

Adhesive for pellicle and pellicle using the same

Technical Field

The present invention relates to a low-outer-gas-resistance adhesive for a pellicle used in photolithography using, for example, EUV (Extreme Ultra Violet) light having a main wavelength of 13.5 nm, and a pellicle using the same.

Background Art

In the manufacture of semiconductors such as LSI and VLSI, or in the manufacture of liquid crystal display panels, semiconductor wafers or liquid crystal original plates are irradiated with light to create patterns. At this time, if dust adheres to the photomask or intermediate mask (hereinafter collectively referred to as the "photomask") used, the tip will become rough and the base will become dirty, resulting in problems such as damage to size, quality, and appearance.

Therefore, these operations are typically performed in a clean room. However, even then, it is difficult to keep the photomask clean. Therefore, a dust-removing pellicle is attached to the photomask surface before exposure. In this way, foreign matter adheres to the pellicle, not directly to the photomask surface. This allows the focus to be maintained on the photomask pattern during photolithography, without any foreign matter from the pellicle being transferred to the photomask.

In such pellicles, a transparent pellicle made of highly transparent nitrocellulose, cellulose acetate, or fluororesin is typically applied to the upper surface of a pellicle frame made of aluminum, stainless steel, polyethylene, or the like. A good solvent for the pellicle is then applied and air-dried (see Patent Document 1), or bonded using an adhesive such as an acrylic resin or epoxy resin (see Patent Document 2). Furthermore, an adhesive layer made of a polybutylene resin, polyvinyl acetate resin, acrylic resin, silicone resin, or the like is formed on the lower surface of the pellicle frame to attach the photomask, along with a release layer (separator) to protect the adhesive layer.

Then, such a dust-proof film assembly is installed on the surface of the photomask. When exposing the photoresist film formed on the semiconductor wafer or the liquid crystal original plate, foreign matter such as dust adheres to the surface of the dust-proof film assembly instead of directly adhering to the surface of the photomask. Therefore, when irradiating with the exposure light, the influence of foreign matter such as dust can be avoided.

However, in recent years, semiconductor devices and liquid crystal display panels have become increasingly integrated and miniaturized. Technology for forming fine patterns around 32nm on photoresist films is now becoming practical. For patterns around 32nm, improved technologies using existing excimer lasers can also be used. These include immersion exposure and double exposure, where the space between the semiconductor wafer or LCD master plate and the projection lens is filled with a liquid such as ultrapure water and the ArF excimer laser is used to expose the photoresist film.

However, next-generation semiconductor devices and liquid crystal display panels require the formation of even finer patterns of less than 10 nm. Formation of such finer patterns of less than 10 nm is no longer possible by modifying the conventional excimer laser.

EUV light, with a dominant wavelength of 13.5nm, is the most effective method for forming patterns smaller than 10nm. However, using this EUV exposure technology to create fine patterns smaller than 10nm on photoresist films requires addressing technical challenges such as the light source, photoresist, and pellicle. To address these technical challenges, research and development of new light sources and photoresist materials is progressing, resulting in various proposals.

Regarding the dustproof film components that affect the yield of semiconductor devices or liquid crystal display panels, for example, in Patent Document 3, although a transparent silicon film with a thickness of 0.1 to 2.0 μm that does not cause optical distortion is described as used in EUV lithography, there are still unresolved problems, which have become obstacles to the application of EUV exposure technology.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 58-219023

Patent Document 2: Japanese Patent Publication No. 63-27707

Patent Document 3: U.S. Patent No. 6,623,893

In particular, the adhesive material used to attach the pellicle to the pellicle frame has traditionally been selected solely based on adhesion during exposure using i-rays (wavelength 365nm), krypton fluoride (KrF) excimer lasers (wavelength 248nm), or ArF excimer lasers (wavelength 193nm). However, when using EUV exposure technology to form fine patterns of less than 10nm in photoresist films, it is necessary to maintain a vacuum within the exposure chamber. However, conventional adhesives generate external gases, which contaminate the pellicle and photomask, making it difficult to form fine patterns. Furthermore, during EUV exposure, the energy of the exposure heats the pellicle, necessitating the use of a heat-resistant adhesive that can withstand these temperatures.

The present invention has been made in view of the above circumstances and has an object to provide a heat-resistant pellicle adhesive having high temperature resistance while reducing the generation of external air that contaminates a photomask, and a pellicle using the same.

To address the above-mentioned issues, the present inventors have focused on silicone adhesives among various adhesives. They have discovered that silicone adhesives that meet the test conditions of TML of 1.0% or less and CVCM of 0.1% or less according to the ASTM E595-93 test method have low outside gas properties and can be used effectively in EUV exposure technology.

Summary of the Invention

That is, the present invention is an adhesive for a dustproof film assembly with low external gas resistance, which is used to attach a dustproof film to a dustproof film assembly frame. The adhesive is characterized in that the adhesive is a silicone-based adhesive. Regarding the external gas resistance of the adhesive, according to the test method of ASTM_E595-93, the TML must meet 1.0% or less, and the CVCM must meet 0.1% or less.

Here, TML stands for Total Mass Loss, and CVCM stands for Collected Volatile Condensable Materials.

Furthermore, the adhesive of the present invention preferably has heat resistance capable of withstanding high temperatures of 100°C to 200°C.

The dustproof film assembly of the present invention is a dustproof film assembly using an adhesive that meets the above conditions, and is particularly preferably a dustproof film assembly that can be exposed to a temperature of 100°C to 200°C during EUV exposure. The dustproof film assembly is formed by attaching the dustproof film to the dustproof film assembly frame using the above-mentioned adhesive that can withstand high temperatures of 100°C to 200°C.

Effects of the Invention

The adhesive of the present invention, even when EUV exposure technology is used, maintains a vacuum in the exposure chamber, and is exposed to high temperatures, generates little external gas from the adhesive, and has heat resistance above 100°C. Therefore, it can prevent contamination of dust-proof films and photomasks and form fine patterns of less than 10nm on the photolithography film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a longitudinal cross-sectional view of a pellicle using a low-atmosphericity adhesive.

FIG2 is a schematic explanatory diagram of an adhesive coating apparatus used in the present invention.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings; however, the present invention is not limited thereto.

Figure 1 is a longitudinal cross-sectional view of one embodiment of a pellicle using a low-atmosphericity adhesive 13. This pellicle 1 is attached to a substrate (a photomask or its glass substrate portion; not shown) and is typically shaped like a rectangular or square frame. A pellicle 11 is stretched across the top surface of a pellicle frame 12 using adhesive 13.

The materials for the pellicle 11 and pellicle assembly frame 12 are not particularly limited, and known materials may be used. Pellicle 11 is preferably made of a material with high EUV light transmittance, such as single-crystal silicon, polycrystalline silicon, or amorphous silicon. Furthermore, a protective film made of SiC, _SiO₂ , _Si₃N₄ , SiON, _Y₂O₃ , YN, _Mo , _Ru , or Rh may also be used to protect the pellicle 11. Metal is preferably used for the pellicle assembly frame 12 in terms of heat dissipation, workability, and strength.

The low-gas-resistance adhesive 13 of the present invention is applied to the entire circumference of the upper end of the pellicle frame 12, thereby attaching the pellicle 11 to the pellicle frame 12. The adhesive 13 of the present invention is a silicone adhesive, and its gas-resistance meets the following test conditions of ASTM E595-93: TML of 1.0% or less and CVCM of 0.1% or less. This silicone adhesive, with its low gas-resistance, is particularly suitable as an adhesive for EUV pellicles.

ASTM_E 595-93 experimental conditions

Vacuum degree: 7.0× ^10-5 Torr or less

Heating rod temperature: 125℃

Cooling plate temperature: 25°C

Experimental time: 24 hours

Here, TML is the total mass loss.

CVCM is the mass ratio of collected volatile condensable materials.

An example of a specific low-extrogas silicone adhesive that meets the above conditions is Shin-Etsu Chemical Co., Ltd.'s commercially available silicone KE-101A/B (product name). KE-101A/B exhibits low extrogas resistance and heat resistance, making it suitable for use. Furthermore, KE-101A/B is a two-component, room-temperature curing adhesive. The adhesive 13 of the present invention can be cured using any method, and single-component heat-curing or UV-curing methods are also acceptable.

The adhesive 13 of the present invention is particularly suitable for EUV pellicles. However, during EUV exposure, the pellicle body is exposed to high temperatures of 100°C to 200°C depending on the exposure energy, so it is preferable to have sufficient heat resistance to withstand such high temperatures.

Thus, among the silicone adhesives that meet the requirements of the ambient air test of the present invention, KE-101A/B adhesives were subjected to a heat resistance test. This heat resistance test involved placing the pellicle 1 in an oven at a 150°C atmosphere for 24 hours, cooling it to room temperature, and then verifying the adhesion (tightness) of the pellicle 11. This heat resistance test confirmed that KE-101A/B, which meets the requirements of the ambient air test of the present invention, maintained a good adhesion (tightness) even after attaching the pellicle 11 to the pellicle frame and exposing it to a high temperature of 150°C.

In addition, as other adhesives, among the silicone-based adhesives that meet the conditions of the external gas test of the present invention, the silicone-based adhesive KE-4908SC-T (product name manufactured by Shin-Etsu Chemical Co., Ltd.) was subjected to the same heat resistance test by raising the oven atmosphere temperature to 200°C, and no abnormality was found in the bonding state of the dust-proof film 11.

From the above heat resistance test, it was confirmed that the silicone adhesive that meets the conditions of the external gas test of the present invention can maintain sufficient heat resistance and adhesion even at high temperatures of 150°C and 200°C. During EUV exposure, even if it is exposed to temperatures of 100°C to 200°C, it can be used as an adhesive for EUV dust-proof film components.

When applying such an adhesive 13 having low ambient air heat resistance to the pellicle frame 12, for example, the coating apparatus shown in Figure 2 can be used. Figure 2 is a schematic diagram of an example of an adhesive coating apparatus suitable for applying the adhesive 13. This adhesive coating apparatus 2 comprises a three-axis robot 22 composed of a fixed track and a movable track. A barrel 23 mounted on a platform 21 is movable in the X, Y, and Z axes. A needle 25 is attached to the tip of the barrel 23. The barrel 23, filled with adhesive 13, is connected to a pneumatic dispenser (not shown). The three-axis robot 22's controller (not shown) controls the robot's movements to dispense the coating liquid.

Then, the needle 25 drips the adhesive onto the pellicle frame 24 installed on the stand 21 of the adhesive coating device 2, while moving, thereby coating the adhesive 13 onto the pellicle frame 24. In this case, the transfer device (not shown) for the adhesive 13 is not limited to a gas pressure type or a gas pressure type such as nitrogen pressure. Various transfer devices that can control the supply amount and discharge and stop can also be used, such as a cylinder pump, a high-pressure piston pump, and a tube pump.

In addition, when the viscosity of the adhesive 13 is high and it is difficult for the coating device 2 to apply it, aromatic solvents such as toluene and xylene, aliphatic solvents such as hexane, octane, isooctane, and isoparaffin, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as diisopropyl ether and 1,4-dioxane, or mixed solvents thereof can be added as necessary.

Example

Hereinafter, the present invention will be described in detail using Examples and Comparative Examples.

<Example 1>

In Example 1, an aluminum alloy pellicle frame 24, measuring 149 mm x 122 mm x 5.8 mm in height and 2 mm thick, was first brought into a clean room, thoroughly cleaned with a neutral detergent and pure water, and dried. The pellicle frame 24 was then secured to the frame 21 of the adhesive coating apparatus 2 shown in Figure 2 .

The silicone-based low-gas adhesive 13 of Example 1 is KE-101A/B (a product of Shin-Etsu Chemical Co., Ltd.). KE-101A/B is a two-component, room-temperature curing adhesive. KE-101A and KE-101B can be weighed in equal amounts and thoroughly stirred to mix.

Next, the prepared adhesive 13 is filled into a polypropylene (PP) cylinder 23 of the adhesive coating apparatus 2 shown in Figure 2 , and this cylinder 23 is connected to a pneumatic dispenser (manufactured by Iwashita Engineering Co., Ltd., not shown). In the adhesive coating apparatus 2, a controller (not shown) of a three-axis robot 22 controls both robot movement and coating liquid dispensing. The robot automatically operates around the entire circumference of a pellicle frame 24, applying the adhesive 13 by dripping from a needle 25.

Then, the pellicle 11 is attached to the adhesive-coated end of the pellicle assembly frame 24, and the unnecessary outer film is cut away with a knife. In Example 1, the adhesive 13 is left to cure at room temperature (25°C) for 24 hours, but heat curing can also be used to shorten the curing time.

<Example 2>

In Example 2, a pellicle 1 was produced in the same manner as in Example 1 except that silicone-based KE-4908SC-T (a product name manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the adhesive 13 .

<Comparative Example 1>

In Comparative Example 1, the pellicle 1 was produced in the same manner as in Example 1 except that epoxy-based araldite AW-106 (product name of Ciba-Geigy, Japan) was used as the adhesive 13 .

<Comparative Example 2>

In Comparative Example 2, a pellicle 1 was produced in the same manner as in Example 1 except that epoxy acrylic-based OptoDine UV-3100 (a product name manufactured by Daikin Industries, Ltd.) was used as the adhesive 13 .

Next, the amount of outgassing and heat resistance of the adhesive 13 were evaluated for Examples 1 and 2 and Comparative Examples 1 and 2, respectively, using the following indices.

External gas experiment

The experimental conditions for evaluating the amount of external gas generated by the adhesive 13 used in Examples 1 and 2 and Comparative Examples 1 and 2 are as follows.

ASTM_E 595-93 experimental conditions

Vacuum degree: 7.0× ^10-5 Torr or less

Heating rod temperature: 125℃

Cooling plate temperature: 25°C

Experimental time: 24 hours

Heat resistance test

The pellicles 1 prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were placed in an oven at 150° C. for 24 hours and then cooled to room temperature. The state (tension) of the pellicles 11 was checked.

The results of the external gas test and the heat resistance test are shown in Table 1 below.

Table 1

The results in Table 1 above show that the adhesives of Examples 1 and 2 reduced the amount of outgassing to 0.4% and 0.6%, respectively, while also maintaining good pellicle tension and exhibiting no degradation of high-temperature adhesion, demonstrating excellent heat resistance. In contrast, the adhesive of Comparative Example 1 exhibited a high outgassing rate of 4.9%, maintaining good pellicle tension. The adhesive of Comparative Example 2 limited outgassing to 0.4%, but the pellicle tension became loose, resulting in poor heat resistance.

Therefore, the silicone-based adhesives KE-101A/B and KE-4908SC-T of Examples 1 and 2 are excellent in low-outgas resistance and heat resistance, and are particularly good in comprehensive evaluation as adhesives used in EUV exposure technology.

Explanation of symbols

1 Dustproof film assembly

11 Dust-proof film

12 Dustproof film assembly frame

13 Adhesive

2 Adhesive coating device

21 racks

22 3-axis robot

23 tubes

24 Dustproof film assembly frame

25 pins

Claims (4)

1. An adhesive for EUV dustproof film assemblies with low external gas content, comprising an adhesive for attaching a dustproof film to a dustproof film assembly frame, characterized in that the adhesive is a two-component room temperature curing silicone adhesive, wherein the external gas content of the adhesive, in the test method of ASTM E595-93, meets the conditions of TML less than 1.0% and CVCM less than 0.1%, where TML refers to weight reduction and CVCM refers to the reagglomerate mass ratio. 2. The adhesive for EUV dustproof film assembly with low external gas susceptibility as described in claim 1, characterized in that the adhesive for EUV dustproof film assembly with low external gas susceptibility has heat resistance of 100°C to 200°C. 3. A dustproof film assembly for EUV, characterized in that it uses the adhesive described in claim 1 or 2. 4. A dustproof film assembly for EUV, which is exposed to a temperature of 100°C to 200°C during EUV exposure, characterized in that the dustproof film of the EUV dustproof film assembly is attached to the dustproof film assembly frame by the adhesive described in claim 2.