JPH07199451A - Pellicle - Google Patents

Abstract

PURPOSE:To provide a pellicle which is provided with a method for specifying the thickness of the pellicle film required for the transmittance of the film to be 98% or higher in either case, the pellicle film being usable for light rays of first and second different wavelengths. CONSTITUTION:This pellicle used for light rays of first and second different wavelengths is characterized in that for the transmittance of a pellicle film to become T or higher as desired, the transmittance is set to a value specified by the formula in which (d) is the thickness of the pellicle film, T is the transmittance of the film, n0 is the refractive index of air, (n) is the refractive index of the pellicle film, lambdak is the wavelength of the light used, and A(d) is the absorption and scattering of the film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to pellicles, and in particular to LS.
Substantially 500 nm, which is used as a dust shield when manufacturing semiconductor devices such as I and VLSI, or liquid crystal display panels.
The present invention relates to a pellicle in an exposure system using the following light.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices such as LSI and VLSI, or liquid crystal display boards, patterning is performed by irradiating a semiconductor wafer or a liquid crystal original plate with light. If dust adheres, this dust absorbs light or bends the light, so the transferred patterning is deformed, the edges are rough, and the white background is stained black, There is a problem in that the dimensions, quality and appearance are impaired, and the performance and manufacturing yield of semiconductor devices and liquid crystal display panels are reduced. Therefore, these operations are usually performed in a clean room, but it is difficult to keep the exposure master always clean even in the clean room. A method of mounting a pellicle to be passed is adopted. In this case, the dust does not directly adhere to the surface of the exposure master plate but adheres to the pellicle. Therefore, if the focus is aligned with the pattern of the exposure master plate during lithography, the dust on the pellicle will not be transferred and the semiconductor device This will improve the performance and manufacturing yield of LCDs and LCD panels.

As a pellicle structure, a pellicle film is formed on one surface of a support frame, and an adhesive for mounting the pellicle film on the exposure original plate is provided on one surface. This film needs to have a high transmittance in order to prevent the projection performance during lithography from decreasing. Therefore, it is necessary to reduce the film thickness of the pellicle film, but the light used in lithography is generally monochromatic light. Therefore, if the film thickness is not appropriate, the transmittance will decrease due to the interference phenomenon of the thin film, the illuminance during lithography will decrease, the exposure time during lithography will increase, and the throughput will decrease.

The light used for lithography is
The wavelength has become shorter with the miniaturization of the pattern line width.
Light of two different wavelengths may be used for one exposure original plate. In this case, a pellicle corresponding to each wavelength must be prepared, and when used, the pellicle must be replaced every time the wavelength changes, which is inevitable. Therefore, a pellicle corresponding to two kinds of wavelengths is required. One example of the method is 2
In order to prevent a decrease in transmittance due to thin film interference for both types of wavelengths, the film thickness of the pellicle film is set to a half wavelength value in the medium in the pellicle film of the first wavelength and the pellicle film of the second wavelength. A method has been proposed in which the half wavelength value in the medium and the least common multiple or an integer multiple of the least common multiple are set (see Japanese Patent Publication No. 3736/1990).

[0005]

However, when the film thickness is controlled according to this method, a high transmittance may be surely obtained at the first wavelength and the second wavelength. However, this method causes various problems during actual manufacturing. Dots come up. That is, depending on the selection of the first wavelength, the second wavelength, and the refractive index of the pellicle film, the film thickness that is the least common multiple becomes thicker, and the film thickness interference phenomenon is controlled by controlling the film thickness to the least common multiple or an integral multiple thereof. Although it is possible to prevent a decrease in transmittance due to, the absorption and scattering of the film itself may be large, and the transmittance at the first and second wavelengths may be low. Further, as the film thickness increases, the in-plane distribution of the film increases, which causes a problem in manufacturing the pellicle film. When the calculated film thickness is small, the transmittance is certainly high at the first wavelength and the second wavelength. However, the strength of the film is reduced, and it does not become a practical pellicle.

Further, the above-mentioned Japanese Patent Publication No. 3736/1993 discloses a method of calculating only a target film thickness, but it is inevitable that a certain amount of film thickness deviation occurs in actual manufacturing. Calculating the allowable range of the film thickness with respect to the required transmittance is indispensable for improving the yield at the time of manufacturing the pellicle. As described above, when realistically determining the film thickness of the pellicle having high transmittance at both the first wavelength and the second wavelength, it is not necessary to consider only the interference of the thin film, and other factors such as those described above are used. Since the factor must also be taken into consideration, the least common multiple or the least common multiple of the half-wavelength value in the medium of the first wavelength pellicle film and the half-wavelength value in the medium of the second wavelength pellicle film The method of controlling the film thickness of the pellicle film to an integral multiple is insufficient.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a pellicle which solves the above problems, and it relates to a first pellicle.
And a second pellicle used for light having different wavelengths, the film thickness d of the pellicle film, the transmittance T, the refractive index of air is n ₀ , and the refractive index of the pellicle film is n. Where λ k is the wavelength of the film and A (d) is the absorption and scattering of the film, the following formula is used so that the transmittance of the pellicle film becomes the desired T or more.

[Equation 2] It is characterized by being a value defined by.

The front part on the right side of the above equation is derived by the interference of the thin film. Let S1 be the incident surface of the thin film and S2 be the exit surface of the thin film, and the amplitude reflectance and amplitude transmittance at S1 and S2 respectively ( r1, t1) (r2, t2), the total amplitude transmittance due to multiple reflection in the thin film is

[Equation 3] It is represented by. δ is a phase delay that occurs while light passes through S1 and S2. Therefore,

[Equation 4] It's easy to see. The energy reflectance T is T
= T × t ^* (where t ^* represents a complex complex number), where Fresnel's relation

[Equation 5] Therefore, T is

[Equation 6] Given in. The rear part on the right side shows absorption and scattering of the film, which is a function of the film thickness. For example, generally, it is represented by A (d) = A'exp (-α · d). Here, A ′ and α are constants.

That is, when the present inventors consider other factors, the thickness of the medium in the medium of the pellicle film of the first wavelength and the thickness of the medium in the medium of the pellicle film of the second wavelength are determined. Even if it is not possible to set the half wavelength value and the least common multiple or an integer multiple of the least common multiple, as a result of various studies to develop a method for defining the film thickness at which high transmittance is obtained at the first wavelength and the second wavelength, For this, the transmittance is T, the refractive index of air is n ₀ , the refractive index of the pellicle film is n, the wavelength of the light used is λ k, and the absorption and scattering of the film are A (d).
Then, in order to make the transmittance of the pellicle film equal to or higher than the desired T, the value of the film thickness d is calculated by the following equation (1).

[Equation 7] It has been found that the transmittances T ₁ and T ₂ at the first and second wavelengths can both be 98% or more when the value defined by The present invention has been completed by conducting research on measures to improve the above. This will be described in more detail below.

[0010]

The present invention relates to a pellicle used for first and second light having different wavelengths. The pellicle film has a light transmittance T, an air refractive index n ₀ , and a pellicle. When the refractive index of the film is n, the wavelength of light used is λk, and the absorption and scattering of the film are A (d), the film thickness d of this pellicle film is defined by the formula shown in the above formula (1). Value, the first and second different wavelengths, eg 4
Even when they are 36nm and 365nm, or 365nm and 248nm,
Light transmittances T ₁ and T _{2 at} this wavelength are both 98%
The advantage of being above is given.

The pellicle in the present invention is used when light of two kinds of wavelengths is used for one exposure original plate, and this pellicle transmits two kinds of light having different first and second wavelengths. The present invention relates to a pellicle having a refractive index of 98% or more. As a result of the research conducted by the present inventors, the pellicle film has a light transmittance of T, an air refractive index of n ₀ , and a pellicle film of refractive index of n ₀ . Assuming that the index is n and the wavelength of the light used is λk, the function of the transmittance T of the pellicle film and the film thickness d of the pellicle film is given by the following equation (2).

[Equation 8] Was found to be

However, regarding this, the thicker the pellicle film, the greater the light absorption and scattering. Therefore, the degree of this light absorption and scattering is a function of the film thickness and is represented by A (d). Therefore, considering the interference of this thin film and the absorption of light in the film, the relationship between the transmittance T and the film thickness d is expressed by the above-mentioned equation (1).

[Equation 9] Will be shown in.

In this case, exemplifying the relationship between the film thickness d and the transmittance T for each of the first wavelength λ ₁ and the second wavelength λ ₂ , this is as shown in FIG. Both the wavelength λ ₁ and the second wavelength λ ₂ have a film thickness range of d _2a to d _1a and d _2b that support a high light transmittance of T _o % or more.
It will be understood that the results are ~ d _1b , d _2c ~ _{d 2d} . In this way T _o
There are several ranges of film thickness that support a transmittance of not less than%, but in consideration of other factors such as film strength, film in-plane distribution, film thickness deviation during film production, etc. It suffices to obtain the optimum range.

According to this, the first wavelength in the range of the film thickness,
It is possible to manufacture a pellicle that has a high transmittance for the second wavelength and is excellent in other properties such as the strength of the film and the in-plane distribution of the film. For example, if the first wavelength and the second wavelength are A pellicle having a light transmittance of 98% or more can be obtained at any of 436 nm and 365 nm and 365 nm and 248 nm, respectively.

[0015]

EXAMPLES Next, examples of the present invention will be given. Example 1 An amorphous fluoropolymer CYTOP (trade name, manufactured by Asahi Glass Co., Ltd.) having a refractive index of 1.34 was used as a pellicle film, and the absorption and scattering coefficients of this film were A
(D) = exp (-αd), but if the first wavelength used here is 436 nm and the second wavelength is 365 nm, then α in A (d) is α ₄₃₆ =
4,930 × 10 ^-7 , α ₃₆₅ = 1,846 × 10 ^-6 . In this case, the film thickness (d) and the transmittance T with respect to the wavelength
From the above equation (1), the relationship with is as shown in FIG. 2, but at this time, the transmittance for each wavelength is
The film thickness of 99% or more is (1) 664 nm to 665 nm, (2) 800 nm to 825 nm in the range of 400 nm to 2,000 nm,
(3) 957nm ~ 960nm, (4) 1,614nm ~ 1,636nm,
(5) It is 1,769 nm to 1,771 nm.

Therefore, a Cytop film having a thickness of 800 nm was prepared on a quartz substrate by using a spin coater, and adhered to an aluminum frame having outer dimensions, width, and height of 98 mm × 120 mm, 2.0 mm, and 5.8 mm, respectively. The film obtained through the agent was stretched to prepare a pellicle, and the transmittance of this film was measured. As a result, it was 99.5% at a wavelength of 436 nm and 99.0% at a wavelength of 365 nm.

In the film thickness range of the above (1) to (5) obtained from the above calculation, considering the fluctuation of the film thickness during film formation, the practically usable film thickness range. Becomes (2) to (4), but if the film thickness in the range of (2) is sufficient in actual use in consideration of the film strength, the film thickness of the pellicle film becomes ( It may be controlled within the range of 2). Further, when stronger strength is required, if the film thickness is controlled within the range of (4), the transmittance at 436 nm and 365 nm exceeds 99%, and a film having higher film strength can be obtained. The required transmittance is 99% here,
It goes without saying that this value can be higher, for example 99.5%, or lower, for example 97%.

Example 2 A pellicle film was used as in Example 1, and the first
If the wavelength is 365 nm and the second wavelength is 248 nm, the α value at this time is α ₃₆₅ = 1,846 × 10 ^-6 , α ₂₄₈ = 7,443 × 10 ^-6, and the film thickness α for each wavelength at this time is The relationship with the transmittance is as shown in FIG. 3 from the above equation (1). Here, the transmittance for each wavelength is
The film thickness of 98% or more is (1) 537 nm to 560 nm, (2) 81
2nm ~ 832nm, (3) 1,087nm ~ 1,102nm, (4) 1,36
2nm ~ 1,372nm, (5) 1,637nm ~ 1,643nm, (6) 1,
742 nm to 1,744 nm, but considering the fluctuation of the film thickness during film formation, the practically usable film thickness range is (1), (2), (3) and (4). Become.

In this case, the shorter the wavelength, the greater the absorption or scattering of the film, and the thicker the film, the greater its effect. Therefore, the film should be as thin as possible.
Since sufficient strength cannot be obtained with a film thickness in the range of (1),
By controlling the film thickness in the range of (2), it is possible to manufacture a pellicle that can be used practically, in which high transmittance and film strength are harmonized.

Then, in the same manner as in Example 1, a spin coater was used to form a Cytop film having a refractive index of 1.34,
A film with a thickness of 812 nm was prepared, a pellicle was prepared using this, and the transmittance of this film was measured to be 99.8% at a wavelength of 365 nm and 98.1% at a wavelength of 248 nm. The thickness cannot be controlled to the least common multiple or the integer multiple of the least common multiple of the half wavelength value in the medium of the first wavelength pellicle film and the half wavelength value in the medium of the second wavelength pellicle film. However, it was confirmed that it is possible to manufacture a film having a high transmittance.

[0021]

The present invention relates to a pellicle which can be used for two kinds of light having different wavelengths. As described above, the pellicle film has a thickness d, a transmittance T, and an air refractive index. where n ₀ , the refractive index of the pellicle film is n, the wavelength of the light used is λ k, and the absorption and scattering of the film are A (d), the transmittance of the pellicle film is equal to or higher than the desired T,
The following formula

[Equation 10] However, according to this, the transmittances T ₁ and T ₂ at the first and second wavelengths can both be 98% or more. However, it can be used for both the first wavelength and the second wavelength having different wavelengths, which provides an advantage that a pellicle having high intensity can be easily obtained.

[Brief description of drawings]

FIG. 1 is a first wavelength λ when a pellicle of the present invention is used.
FIG. 5 is a diagram showing the relationship between the film thickness d and the transmittance for each of ₁ and the second wavelength λ ₂ .

FIG. 2 shows a pellicle according to the first embodiment of the present invention.
6 is a diagram showing the relationship between the film thickness d and the transmittance T for each wavelength when the first wavelength of 436 nm and the second wavelength of 365 nm are used.

FIG. 3 shows a pellicle according to a second embodiment of the present invention.
6 is a diagram showing the relationship between the film thickness d and the transmittance T for each wavelength when the first wavelength of 365 nm and the second wavelength of 248 nm are used.

Front page continuation (72) Inventor Aihiko Nagata 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd., Institute for Precision Materials (72) Inventor Shu Kashida 2-chome, Isobe, Gunma Prefecture 13-1 Shinetsu Kagaku Kogyo Co., Ltd. Precision Materials Research Laboratory (72) Inventor Yoshihiro Kubota 2-13-1 Isobe, Annaka-shi, Gunma Shin-Etsu Kagaku Kogyo Co. Ltd.

Claims (3)

[Claims] 1. A film thickness d of a pellicle film in a pellicle used for first and second light having different wavelengths.
And the transmittance T, n ₀ the refractive index of air, the refractive index of the pellicle film n, .lamda.k the wavelength of light used, the absorption and scattering of the film when the A (d), transmission of the pellicle membrane In order that the rate be equal to or higher than the desired T, the following equation A pellicle characterized by a value defined by. 2. A pellicle used for light having different first and second wavelengths, wherein when the first and second wavelengths are 436 nm and 365 nm, respectively, the transmission at the first and second wavelengths is achieved. The pellicle according to claim 1, wherein the thickness of the pellicle film is controlled so that both the rates T ₁ and T ₂ have a value of 99% or more. 3. A pellicle used for light having different first and second wavelengths, wherein when the first and second wavelengths are 365 nm and 248 nm, respectively, transmission at the first and second wavelengths is achieved. The pellicle according to claim 1, wherein the film thickness of the pellicle film is controlled so that both the rates T ₁ and T ₂ have a value of 98% or more.