KR102634999B1 - Adhesive suitable for euv lithographic pellicle and pellicle using thereof - Google Patents

Abstract

(Project) Provide an adhesive suitable for a pellicle for EUV lithography, a pellicle using the same, a manufacturing method for the pellicle, and a method for selecting an adhesive suitable for a pellicle for EUV lithography.
(Solution) The adhesive of the present invention has a hardness change rate expressed by the following formula within the range of ±50% when the cured product of the adhesive is left to stand continuously for 7 days in an atmosphere of 300°C.
Formula: Hardness change rate (%) = {(hardness after the above-mentioned setting) - (hardness before the above-mentioned setting)} ÷ (hardness before the above setting) × 100

Description

Adhesive suitable for pellicle for EUV lithography and pellicle using the same {ADHESIVE SUITABLE FOR EUV LITHOGRAPHIC PELLICLE AND PELLICLE USING THEREOF}

The present invention relates to an adhesive suitable for a pellicle for EUV lithography and a pellicle using the same, and more specifically, for use when performing lithography using EUV (Extreme Ultra-Violet) light with a dominant wavelength of 13.5 nm, for example. This relates to an adhesive suitable for pellicle and a pellicle using it.

In the manufacture of semiconductors such as LSI, ultra-LSI, or liquid crystal displays, patterns are produced by irradiating light to a semiconductor wafer or liquid crystal original, and a photomask or reticle (hereinafter simply referred to as a “photomask”) is used at this time. If dust adheres to the surface, the dust blocks or reflects the irradiated light, causing the edges of the transferred pattern to become jagged, the underlying surface to become stained black, etc., and the dimensions, quality, and appearance to change. There was a problem with back damage.

For this reason, these operations are usually performed in a clean room, but since it is still difficult to always keep the photomask clean, exposure is performed after attaching a pellicle to the surface of the photomask as a dust shield. In this case, since foreign substances such as dust are not attached directly to the surface of the photomask but attached to the pellicle, if the focus is placed on the pattern of the photomask during lithography, the image of the foreign substances does not appear in the transferred pattern, and It becomes possible to avoid problems.

In such a pellicle, a transparent pellicle film made of nitrocellulose, cellulose acetate, or fluororesin that transmits light well is generally placed on the upper surface of a pellicle frame made of aluminum, stainless steel, polyethylene, etc., and a good solvent for the pellicle film is applied. After application, it is dried by air and adhered (see Patent Document 1), or is adhered using an adhesive such as acrylic resin or epoxy resin (see Patent Document 2). In addition, on the bottom surface of the pellicle frame, there is an adhesive layer made of polybutene resin, polyvinyl acetate resin, acrylic resin, silicone resin, etc. for adhesion to the photomask, and a release layer (separator) for the purpose of protecting the adhesive layer. It is formed.

However, in recent years, the reality is that semiconductor devices and liquid crystal displays are becoming increasingly highly integrated and miniaturized. Currently, technology for forming fine patterns of approximately 32 nm on a photoresist film is also being put into practical use. For patterns of about 32 nm, conventional methods such as liquid immersion exposure technology or multiple exposure are used to fill the space between a semiconductor wafer or liquid crystal original and the projection lens with a liquid such as ultrapure water and expose the photoresist film using an argon fluoride (ArF) excimer laser. It is possible to respond with improved technology using excimer lasers.

However, next-generation semiconductor devices and liquid crystal displays require the formation of even finer patterns of 10 nm or less. In order to form such finer patterns of 10 nm or less, improvements in exposure technology using conventional excimer lasers are already required. It is impossible to respond.

Therefore, as a method for forming patterns of 10 nm or less, EUV exposure technology using EUV light with a dominant wavelength of 13.5 nm is considered influential. When using this EUV exposure technology to form fine patterns of 10 nm or less on a photoresist film, it is important to solve technical issues such as what light source to use, what kind of photoresist to use, and what kind of pellicle to use. Among these technical tasks, new light sources and new photoresist materials are being developed and various proposals are being made.

Among them, regarding the pellicle that determines the yield of a semiconductor device or liquid crystal display, for example, Patent Document 3 describes a pellicle film used in a pellicle for EUV lithography with a thickness of 0.1 to 2.0 μm that is transparent and does not cause optical deformation. Although a silicone film has been described, unresolved problems remain in terms of practical use, and the reality is that these problems are a major obstacle to putting EUV exposure technology into practical use.

Japanese Patent Publication No. 58-219023 Japanese Patent Publication No. 63-27707 US Patent No. 6623893 Specification

Usually, the adhesive material for attaching the pellicle film to the pellicle frame includes exposure using conventional i-rays (wavelength 365 nm), exposure using krypton fluoride (KrF) excimer laser light (wavelength 248 nm), and argon fluoride ( Exposure using ArF) excimer laser light (wavelength 193 nm) was selected in consideration of its adhesive strength.

However, in an experiment in an environment assuming that a fine pattern of 10 nm or less is formed on a photoresist film using EUV lithography technology, it was found that with conventionally used adhesives, the pellicle film often peeled off from the pellicle frame. A problem occurred.

Therefore, in order to solve the above problem, the present inventor repeated simulations on a personal computer and found that the area where the EUV light is irradiated to the silicon pellicle film has the possibility of being heated to around 500°C by the energy of the EUV light. It was recognized by calculation that heat of 200°C to 300°C could be applied to the adhesive that joins the pellicle film and the pellicle frame. And, it was thought that the main cause of the pellicle film peeling in the above-described experiment was this high temperature. In other words, the hardness of the adhesive changes at such high temperatures, and when the hardness increases, it becomes brittle and cannot prevent peeling of the pellicle film. On the other hand, when the hardness decreases due to high temperature, it becomes fluid and acts to secure the pellicle film. It was thought that it became impossible to prevent peeling of the pellicle membrane. Therefore, in the pellicle for EUV lithography, it was determined that if the adhesive had low stability against heat, the adhesive would harden or soften excessively when heated, making it impossible to maintain adhesiveness.

Therefore, the present invention has been made in consideration of the above circumstances, and its object is to provide an adhesive suitable for a pellicle for EUV lithography that has excellent heat resistance (temperature stability) in the high temperature range occurring in EUV lithography, and a pellicle using the same. , a method of manufacturing the pellicle, and a method of selecting an adhesive suitable for the pellicle for EUV lithography.

The present inventor conducted intensive studies to solve the above problems, and as a result, among many types of adhesives, there were adhesives whose hardness change rate was within the range of ±50% when left to stand in an atmosphere of 300°C for 7 days continuously. discovered that it was suitable for use in EUV exposure technology and completed the present invention.

That is, the adhesive of the present invention is an adhesive suitable for a pellicle for EUV lithography for adhering a pellicle film to a pellicle frame, and the hardness change rate expressed by the following formula when the cured product of the adhesive is left to stand in an atmosphere of 300 ° C. for 7 days continuously It is characterized by being within this range of ±50%.

Formula: Hardness change rate (%) = {(hardness after the above-mentioned setting) - (hardness before the above-mentioned setting)} ÷ (hardness before the above setting) × 100

Additionally, the pellicle of the present invention is a pellicle for EUV lithography that includes a pellicle film, a pellicle frame, and an adhesive that bonds them together, and is characterized by using the adhesive of the present invention as the adhesive.

In addition, the method of manufacturing a pellicle of the present invention is a method of manufacturing a pellicle for EUV lithography including a pellicle film, a pellicle frame, and an adhesive that adheres them to each other, and includes a step of applying the adhesive of the present invention to the pellicle frame. It is characterized by:

In addition, the method of selecting an adhesive of the present invention is a method of selecting an adhesive suitable for a pellicle for EUV lithography for adhering the pellicle film of the pellicle for EUV lithography to a pellicle frame. The cured product of the test adhesive is continuously subjected to 7 cycles in an atmosphere of 300°C. It is characterized in that an adhesive suitable for a pellicle for EUV lithography is selected as an adhesive that satisfies the condition that the hardness change rate expressed by the following equation when left to stand for a day is within the range of ±50%.

Formula: Hardness change rate (%) = {(hardness after the above-mentioned setting) - (hardness before the above-mentioned setting)} ÷ (hardness before the above setting) × 100

Since the adhesive of the present invention has stability in the high temperature region experienced in EUV exposure technology, it is possible to maintain adhesion between the pellicle film and the pellicle frame in EUV lithography. Therefore, by using a pellicle in which the pellicle film and the pellicle frame are bonded with the adhesive of the present invention, it becomes possible to form a fine pattern of 10 nm or less on the photoresist film using EUV light.

1 is a longitudinal cross-sectional view of a pellicle using the adhesive of the present invention.
Figure 2 is a schematic diagram of an adhesive application device used when manufacturing the pellicle of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these.

Fig. 1 is a longitudinal cross-sectional view showing one embodiment of the pellicle 1 of the present invention using the adhesive 13 of the present invention. This pellicle 1 is a pellicle for EUV lithography that includes a pellicle film 11, a pellicle frame 12, and an adhesive 13 that bonds them together. In this pellicle 1, the pellicle frame 12 is usually in the shape of a square frame (rectangular frame shape or square frame shape) corresponding to the shape of the substrate (photomask or glass substrate portion thereof: not shown) to which the pellicle 1 is attached. ) A pellicle film (11) is spread and installed on the upper surface of the panel with an adhesive (13) interposed therebetween.

There are no particular restrictions on the materials of the pellicle film 11 and the pellicle frame 12, and known materials can be used.

The material forming the pellicle film 11 is preferably one that has high transparency to EUV light, such as single crystal silicon, polycrystalline silicon, or amorphous silicon. Additionally, for the purpose of protecting the pellicle film 11, a protective film made of SiC, SiO ₂ , Si ₃ N ₄ , SiON, Y ₂ O ₃ , YN, Mo, Ru, Rh, etc. may be provided.

The material of the pellicle frame 12 is preferably made of glass or metal with a small coefficient of linear expansion, but is more preferably made of metal in terms of heat dissipation, processability, and strength.

The adhesive 13 of the present invention is applied over the entire circumference of the upper end of the pellicle frame 12, and is used to attach the pellicle film 11 to the pellicle frame 12. As the adhesive 13 of the present invention, a hardness change rate expressed by the following formula when the cured product of the adhesive is left to stand continuously for 7 days in an atmosphere of 300° C. is within the range of ±50% is adopted. Such adhesives have high heat resistance (stability to temperature) during EUV lithography, and are therefore particularly suitable for pellicle for EUV lithography. In addition, in this specification and the scope of the patent claims, the term “hardness” of a cured product such as an adhesive refers to a hardness test conducted in accordance with JIS K 6249:2003, particularly using a durometer type A device. It is defined by the obtained hardness value.

Formula: Hardness change rate (%) = {(hardness after the above-mentioned setting) - (hardness before the above-mentioned setting)} ÷ (hardness before the above setting) × 100

In order to obtain the adhesive 13 of the present invention, for example, a commercially available adhesive is obtained, and the hardness change rate expressed by the above formula when the cured product is left to stand in an atmosphere of 300° C. for 7 consecutive days is ±50%. Just select the one that satisfies the conditions within the range. As a result, an adhesive suitable for a pellicle for EUV lithography can be easily obtained without going through a complicated manufacturing process.

Specific examples of the adhesive 13 that satisfies such conditions include commercially available silicone-based adhesives KE-1803 and KE-1854 (both manufactured by Shin-Etsu Chemical Co., Ltd.; product names), and EK2000 (Epoxy Technology, Inc.), an epoxy-based adhesive. Manufacturing: product name). These have high heat resistance up to 300°C and can be used suitably. KE-1803 is a three-component room temperature curing type according to the prescription, but the time until hardening can be shortened by heating. KE-1854 is a one-liquid heat-curing type, and EK2000 is a two-liquid heat-curing type.

The adhesive 13 of the present invention is not limited in its curing form, and may be of any curing form, such as 1-component room temperature curing type, 1-component heat-curing type, 2-component room temperature-curing type, 2-component heat-curing type, 3-component room temperature curing type, or ultraviolet curing type. It can be anything.

The adhesive 13 of the present invention is particularly suitable for adhering a pellicle film to a pellicle frame in a pellicle for EUV lithography. As mentioned above, during EUV exposure, the pellicle film may be partially exposed to temperatures as high as 500°C due to the energy of the exposure light, and furthermore, the adhesive that joins the pellicle film and the pellicle frame has a temperature of 200°C to 300°C. There is a possibility that it will be inflicted.

Therefore, the adhesive 13 of the present invention also needs to have sufficient heat resistance in such a high temperature range, and a heat resistance test of a pellicle using the adhesive 13 of the present invention (the pellicle 1 was placed in an oven at 250° C. As a result of continuously standing for 7 days and then cooling to room temperature), when the adhesive 13 satisfying the above conditions of the present invention was used, the state of tightness of the pellicle film 11 exposed to a high temperature of 250 ° C. It was confirmed that it was maintained well (see examples described later). This is believed to be the result of the adhesive 13 of the present invention maintaining sufficient adhesive strength even when exposed to a high temperature of 250°C. Therefore, the adhesive 13 of the present invention is heat resistant not only at 200°C but also in the high temperature range of 300°C. It indicates that the possibility of having a has been confirmed.

When applying the adhesive 13 having such high heat resistance to the pellicle frame 12, it can be performed, for example, using the adhesive coating device shown in FIG. 2. FIG. 2 is a schematic diagram showing an example of an adhesive application device suitable for application of the adhesive 3. This adhesive application device 2 is mounted above the stand 21 via a three-axis robot 22 configured by combining a fixed rail and a movable rail so that the syringe 23 can be moved in the XYZ axis directions. . A needle 25 is attached to the tip of the syringe 23, and the syringe 23 filled with the adhesive 13 is connected to an air pressurized dispenser (not shown), and the control unit (not shown) of the three-axis robot 22 is connected to the syringe 23. Both robot operation and coating liquid discharge can be controlled by this.

Then, the needle 25 moves on the pellicle frame 24 set on the stand 21 of the adhesive application device 2 while dropping the adhesive, and applies the adhesive 13 on the pellicle frame 24. You can. In this case, the transport means (not shown) of the adhesive 13 is not limited to gas pressurization such as air pressurization or nitrogen pressurization, but also includes a syringe pump, plunger pump, tube pump, etc. to control the supply amount and discharge/stop. Various means of transportation are available.

In addition, when the viscosity of the adhesive 13 is high and application by the coating device 2 is difficult, if necessary, an aromatic solvent such as toluene or xylene, an aliphatic solvent such as hexane, octane, isooctane, or isoparaffin, or methyl solvent may be used. Ketone-based solvents such as ethyl ketone and methyl isobutylmethone, ester-based solvents such as ethyl acetate and butyl acetate, ether-based solvents such as diisopropyl ether and 1,4-dioxane, or mixed solvents thereof can be added. there is.

Example

Next, the present invention will be described in detail by showing examples and comparative examples.

[Example 1]

First, a pellicle frame 24 made of super invariable steel (an alloy of iron, nickel, and cobalt) with an external size of 151 mm × 118 mm × height of 1.5 mm and a thickness of 4 mm was brought into the clean room and washed with neutral detergent and pure water. It was sufficiently washed and dried. After that, this pellicle frame 24 was fixed on the stand 21 of the adhesive application device 2 shown in FIG. 2.

Meanwhile, as the highly heat-resistant adhesive 13, silicone-based KE-1803 (manufactured by Shin-Etsu Chemical Co., Ltd.: product name) was used. Since this KE-1803 is a three-component room temperature curing type, according to the prescription, the main component of KE-1803, the curing agent, and the catalyst are weighed in a mass ratio of 100/10/10 and mixed with sufficient stirring. did.

Next, the prepared adhesive 13 is filled into the syringe 23 made of polypropylene (PP) of the adhesive application device 2 shown in FIG. 2, and this syringe 23 is dispensed into an air pressurized dispenser (manufactured by Iwashita Engineering Co., Ltd.) (not shown) was accessed. In the adhesive application device 2, both robot motion and coating liquid discharge are controlled by a control unit (not shown) of the three-axis robot 22, and the entire circumference of the pellicle frame 24 is covered by automatic operation, Application was performed by dropping the adhesive 13 from the needle 25.

Thereafter, the pellicle film 11 was attached to the adhesive-coated end surface side of the pellicle frame 24, and the unnecessary film on the outside was cut away with a cutter. Furthermore, the adhesive 13 was left to stand at room temperature (25°C) for 24 hours to harden, and the pellicle 1 was manufactured.

[Example 2]

As the adhesive 13, KE-1854 (manufactured by Shin-Etsu Chemical Co., Ltd.: product name), a silicone-based, one-component heat-curing type, was used, but other than that, the pellicle 1 was manufactured in the same manner as in Example 1.

[Example 3]

As the adhesive 13, KE-1880 (manufactured by Shin-Etsu Chemical Co., Ltd.: product name), a silicone-based, one-component heat-curing type, was used, but other than that, the pellicle 1 was manufactured in the same manner as in Example 1.

[Example 4]

As the adhesive 13, EK2000 (manufactured by Epoxy Technology, Inc.: product name), an epoxy-based, two-component heat-curing type, was used, but other than that, the pellicle 1 was manufactured in the same manner as in Example 1.

[Comparative Example 1]

As the adhesive 13, Araldite AV138M-1 (product name, manufactured by Chiba Geiki), an epoxy-based heat-resistant adhesive, was used, but other than that, the pellicle 1 was manufactured in the same manner as in Example 1.

[Comparative Example 2]

As the adhesive 13, Metalloc (product name, manufactured by Cemedine Co., Ltd.), an acrylic heat-resistant adhesive, was used, but other than that, the pellicle 1 was manufactured in the same manner as in Example 1.

[Comparative Example 3]

As the adhesive 13, a silicone-based adhesive KE-3490 (manufactured by Shin-Etsu Chemical Co., Ltd.: product name) was used, but other than that, the pellicle 1 was manufactured in the same manner as in Example 1.

[Comparative Example 4]

As the adhesive 13, Araldite 2000 (product name, manufactured by Ciba Geiki), an epoxy-based heat-resistant adhesive, was used, but other than that, the pellicle 1 was manufactured in the same manner as in Example 1.

[Heat resistance test of adhesive]

Only the cured products of the respective adhesives 13 used in Examples 1 to 4 and Comparative Examples 1 to 4 were allowed to stand in an oven at 300°C for 7 days continuously, and then cooled to room temperature to evaluate heat resistance. As an index for evaluating heat resistance, the hardness change rate expressed by the following formula was used for comparison. The results are shown in Table 1.

Formula: Hardness change rate (%) = {(hardness after the above-mentioned setting) - (hardness before the above-mentioned setting)} ÷ (hardness before the above setting) × 100

[Heat resistance test of pellicle]

The pellicle 1 manufactured in Examples 1 to 4 and Comparative Examples 1 to 4 was left in an oven at 250°C for 7 days continuously, then cooled to room temperature, and the state of tightness of the pellicle film 11 was confirmed. The results are shown in Table 1.

According to the results in Table 1 above, in the adhesives used in Examples 1 to 4, the rate of change in hardness after the heat resistance test at 300°C was suppressed as low as +40%, +50%, -30%, and +50%, respectively, and the adhesives In the heat resistance test of the pellicle using , it was confirmed that the pellicle film was in a good state of tension, so the adhesive used in Examples 1 to 4 had no deterioration in adhesive strength at high temperatures and had high heat resistance.

On the other hand, in the adhesives used in Comparative Examples 1 to 3, the hardness change rate after the heat resistance test at 300°C was large, +350%, +400%, and +200%, respectively, and the state (property) of the adhesive became soft. In addition, in the adhesive of Comparative Example 4, the hardness change rate after the heat resistance test at 300°C was -100%, and the state (property) of the adhesive became soft. In addition, in the heat resistance test of the pellicle, peeling of the pellicle film from the pellicle frame was observed, so it was confirmed that the adhesive used in Comparative Examples 1 to 4 had inferior heat resistance.

In this way, the silicone-based adhesives KE-1803, KE-1854, KE-1880, and the epoxy-based adhesive EK2000 used in Examples 1 to 4 have excellent heat resistance, and are particularly suitable for pellicle use when using EUV exposure technology. It was confirmed to be suitable as an adhesive when viewed comprehensively.

1: pellicle
2: Adhesive application device
11: Pellicle membrane
12: Pellicle frame
13: Adhesive
21: trestle
22: 3 axis robot
23: Syringe
24: Pellicle frame
25: Needle

Claims (14)

As an adhesive used in pellicles for EUV lithography,
The adhesive is used to fix the pellicle film, which is a component of the pellicle for EUV lithography, to the pellicle frame,
An adhesive used in a pellicle for EUV lithography, wherein the hardness change rate expressed by the following formula when the cured product of the adhesive is left to stand continuously for 7 days in an atmosphere of 300° C. is within the range of ±50%.
Formula: Hardness change rate (%) = {(hardness after the above-mentioned setting) - (hardness before the above-mentioned setting)} ÷ (hardness before the above setting) × 100 According to claim 1,
Adhesive used in pellicles for EUV lithography exposed to temperatures of 200 ℃ to 300 ℃. According to claim 1,
An adhesive used in a pellicle for EUV lithography, wherein the adhesive is a silicone-based adhesive. According to claim 1,
An adhesive used in a pellicle for EUV lithography, wherein the adhesive is an epoxy adhesive. delete A pellicle frame attached with an adhesive used in a pellicle for EUV lithography,
The adhesive is used to fix the pellicle film, which is a component of the pellicle for EUV lithography, to the pellicle frame,
A pellicle frame with an adhesive used in a pellicle for EUV lithography, characterized in that the hardness change rate expressed by the following formula is within the range of ±50% when the cured product of the adhesive is left to stand continuously for 7 days in an atmosphere of 300 ° C.
Formula: Hardness change rate (%) = {(hardness after the above-mentioned setting) - (hardness before the above-mentioned setting)} ÷ (hardness before the above setting) × 100 According to claim 6,
A pellicle frame attached with an adhesive used for EUV lithography pellicles exposed to temperatures of 200 ℃ to 300 ℃. According to claim 6,
A pellicle frame with an adhesive used in a pellicle for EUV lithography, wherein the adhesive is a silicone-based adhesive. According to claim 6,
A pellicle frame attached with an adhesive used in a pellicle for EUV lithography, wherein the adhesive is an epoxy-based adhesive. A pellicle for EUV lithography comprising a pellicle film, a pellicle frame, and an adhesive that secures the pellicle film to the pellicle frame,
A pellicle for EUV lithography, characterized in that the adhesive according to claim 1 is used as the adhesive. A photomask with a pellicle for EUV lithography attached, wherein the pellicle for EUV lithography according to claim 10 is attached to a photomask. An exposure method characterized by EUV exposure using a photomask attached with a pellicle for EUV lithography according to claim 11. A method of manufacturing a semiconductor comprising a process of EUV exposure using a photomask attached with a pellicle for EUV lithography according to claim 11. delete

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