KR20110057423A - Pellicle for liquid immersion lithography apparatus and forming method of the same - Google Patents

Abstract

PURPOSE: A pellicle for a liquid immersion lithography apparatus is provided to ensure high exposure light transmittance even if the value of the incident angle of a light source is increased. CONSTITUTION: A pellicle for a liquid immersion lithography apparatus is an ArF excimer laser in which a light source for exposure is 193 nm. When the incident angle on a pellicle film is 0° or more and 20° or less, light transmissivity is 99.3% or greater. The reflectivity of the pellicle for the liquid immersion lithography apparatus is 1.38-1.39 and the film thickness is 282nm - 284nm.

Description

Pellicle for liquid immersion exposure apparatus and its manufacturing method {Pellicle for Liquid Immersion Lithography Apparatus and Forming Method of the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pellicle for lithography used as a dustproof film when manufacturing a semiconductor device or a liquid crystal display, and more particularly, to a pellicle for an immersion exposure apparatus used for exposure requiring high resolution.

In manufacturing a semiconductor device or a liquid crystal display panel, a method called photolithography is used when patterning by irradiating UV light to a semiconductor wafer or a liquid crystal substrate. In photolithography, a mask is used as an original plate of patterning, and the pattern on the mask is transferred to a wafer or a liquid crystal substrate. When dust adheres to the mask, light is absorbed or reflected by the dust, and thus the transferred pattern is damaged, resulting in a decrease in performance or yield of a semiconductor device, a liquid crystal display panel, or the like. Therefore, although these operations are usually performed in a clean room, since dust exists in this clean room, the method of attaching a pellicle is performed in order to prevent dust from adhering to the mask surface. In this case, dust does not adhere directly to the surface of the mask, but adheres onto the pellicle film, and in lithography, since the focus is coincident with the pattern of the mask, the dust on the pellicle is out of focus and thus has no advantage of transferring to the pattern.

Increasingly, the required resolution of the exposure apparatus for semiconductor manufacturing is increasing, and the wavelength of a light source becomes shorter and shorter in order to implement the resolution. Specifically, the UV light source has gradually shortened from the ultraviolet ray g line (436 nm), the I line (365 nm), and the KrF excimer laser (248 nm) to the ArF excimer laser (193 nm). Since the light of such a short wavelength is large in energy, it is difficult to secure sufficient light resistance with a conventional cellulose-based film material, and a transparent fluorine resin is used as a film material after the KrF excimer laser. In recent years, in order to perform finer processing using an ArF excimer laser without reducing a UV wavelength band, the examination which uses an immersion exposure apparatus as disclosed by Unexamined-Japanese-Patent No. 7-220990, 10-303114, etc. is carried out. Is starting. The liquid immersion exposure apparatus is an exposure apparatus that achieves a higher numerical aperture (NA) by filling a gap between an objective lens and a silicon wafer with a liquid to obtain a higher resolution. As the numerical aperture of the exposure apparatus increases in this way, the incident angle of the exposure light passing through the peripheral circumference of the pellicle increases.

As described above, when the numerical aperture of the exposure apparatus increases, the incident angle of the exposure light passing through the peripheral circumference of the pellicle increases. In general, the transmittance of the pellicle is set so that the maximum transmittance is obtained with respect to the vertical incident light, and the phenomenon that the transmittance decreases as the incident angle increases. This transmittance decreases rapidly as the film thickness increases.

The present invention has been made to solve such a problem, and an object thereof is to provide a pellicle that can be used in an immersion exposure apparatus having a high numerical aperture.

According to the present invention, there is provided a pellicle used in semiconductor lithography, wherein the light source for exposure is an ArF excimer laser having a wavelength of 193 nm, and the light transmittance is 99.3% or more when the angle of incidence in the pellicle film is 0 ° or more and 20 ° or less. A pellicle for an immersion exposure apparatus is provided.

The thickness of the pellicle film preferably satisfies the following Equations 1 to 5.

Equation 1 R = r (1-cosX)

[Equation 2] r = 2 {(n-1) / (n + 1)} ²

[Equation 3] X = 4πnd / λ

Equation 4 T (%) = 1-R = 100 * {1-2 {(n-1) / (n + 1)} ² * (1-cos (4πnd / λ * cosθ))}

Equation 5 d = mλ / (2n * cosθ) (m = 0, 1, 2, ...)

(In the above formula, R: reflectance considering interference, r: reflectance not considering interference, n: refractive index of pellicle film, d: film thickness of pellicle (nm), λ: wavelength of light source for exposure (nm), T: transmittance (%), θ: incident angle)

The refractive index of the pellicle film is 1.38 to 1.39, and the film thickness is preferably 282 to 284 nm, and the pellicle film is preferably made of a fluorine resin solution having a viscosity of 30 to 35 cP at 23 ° C.

In addition, a method of preparing a pellicle for an immersion exposure apparatus used for semiconductor lithography by applying, drying, and peeling an organic solution for forming a pellicle film on a substrate, wherein a fluorine resin solution having a viscosity of 30 to 35 cP at 23 ° C. is prepared. step; And applying, drying, and peeling off the fluororesin solution on the substrate, wherein applying the fluororesin solution is a step of applying a thickness of the pellicle film after drying to satisfy Equations 1 to 5. A method for producing a pellicle for an immersion exposure apparatus is provided.

In addition, the step of applying the fluorine resin solution is provided, the method of manufacturing a pellicle for an immersion exposure apparatus, characterized in that the step of applying so that the thickness of the pellicle film after drying is 282 to 284nm.

The pellicle for an immersion exposure apparatus according to the present invention has an advantage of providing a pellicle having a high exposure light transmittance even if the incident angle of the light source of the exposure apparatus increases.

As a material of a pellicle film, the material which has a high exposure light transmittance and is hard to absorb exposure light is preferable. Specifically, cellulose resins such as nitrocellulose and cellulose acetate or fluorine resins are preferable. In recent years, the required resolution of exposure apparatus for semiconductor manufacturing is gradually increasing, and light with a short wavelength is used as a light source in order to realize the resolution. Since light having a short wavelength is large in energy as described above, it is difficult to ensure sufficient light resistance with a conventional cellulose membrane material. Therefore, recently, a pellicle film is mainly manufactured using a fluorine resin solution. The solvent is not particularly limited as long as it dissolves the resin, and a soluble fluorine solvent having a high degree of polymerization is preferable. Such solvents include aromatic halogen compounds, fluoroalkylated alcohols, fluorofluoroolefins (eg, tetrafluoroethylene oligomers, hexafluoropropylene oligomers, etc.), fluorinated cyclic ether compounds, and the like. . The concentration of the solution is 0.1 to 20% by weight, preferably 0.3 to 10% by weight.

In the immersion exposure pellicle requiring high resolution, the viscosity of the solution is more preferably 30 to 35 cP at 23 ° C. If the viscosity of the solution is 35 cP or more, a fine circular surface pattern may be formed on the surface of the pellicle film after drying, and appearance defects may occur. If the viscosity is 30 cP or less, it is difficult to obtain a pellicle film having a uniform thickness even if the rotation speed is adjusted. to be.

A solution in which the fluorine resin constituting the prepared pellicle film is dissolved is coated on a substrate and dried at a temperature near the boiling point of the solvent to form a pellicle film. The thickness of the film can be adjusted by changing conditions such as the concentration of the solution to be applied to the substrate and the number of revolutions of the spin coater.

The pellicle film preferably has a high light transmittance even when the incident angle of the exposure light incident on the pellicle film changes, and specifically, the light transmittance is preferably 99.3% or more. In particular, when the light transmittance is 99.3% or more when the incident angle is 0 ° or more and 20 ° or less, it is preferable that the film thickness is 282 to 284 nm and the maximum transmittance at an incident angle of 15 ± 0.1 °. When the incident angle is 0 ° or more and 20 ° or less, the thickness of the pellicle film having a light transmittance of 99.3% or more can be calculated through the following equations (1) to (5).

[Equation 1]

R = r (1-cosX)

[Equation 2]

r = 2 {(n-1) / (n + 1)} ²

&Quot; (3) "

X = 4πnd / λ

&Quot; (4) "

T (%) = 1-R = 100 * {1-2 {(n-1) / (n + 1)} ² * (1-cos (4πnd / λ * cosθ))}

[Equation 5]

d = mλ / (2n * cosθ) (m = 0, 1, 2, ...)

 (In the above formula, R: reflectance considering interference, r: reflectance not considering interference, n: refractive index of pellicle film, d: film thickness of pellicle (nm), λ: wavelength of light source for exposure (nm), T: transmittance (%), θ: incident angle)

That is, if the above equation is calculated under the conditions of 0 ° ≤θ≤20 ° and 99.3% ≤T (%), the required thickness of the pellicle film can be obtained according to the refractive index of the pellicle film and the wavelength of the light source used. Among the obtained several film thicknesses, the thickness of the film is so thick as to be maintained, and at the same time, the thickness is selected so as not to absorb the exposure light.

For example, an ArF excimer laser (wavelength 193 nm) is used as a light source of the exposure apparatus, and a fluorine resin having a refractive index n of 1.386 is used as a material of the pellicle film, and when the incident angle is 15 °, the pellicle film thickness is m value. It is calculated to increase to about 70.9 nm, 142 nm, 213 nm, 284 nm, and 354 nm as it increases to 1, 2, 3, 4, 5. Among these values, the thickness of the pellicle film may be selected in consideration of the strength of the film and whether the exposure light is absorbed.

Figure 1 is a comparison of the value of the incident angle is 0 ^o 20 ^o or more or less time, the actually measured value calculated by the following Equation 1-5 to film the light transmittance of the pellicle film having a thickness of 282 to 284nm incident angle graph. Although there is a slight difference between the theoretical value and the actual transmittance, it is generally consistent, and it can be seen that the transmittance is 99.3% or more in the entire incidence angle range from 0 ^° to 20 ^° .

Hereinafter, although an Example is given and it demonstrates concretely, this invention is not limited to an Example.

(Example 1)

As a film forming material for the pellicle film, a fluorine resin (Cytop CTX-S) manufactured by Asahi Glass Co., Ltd. was prepared using a fluorine-based solvent (CTX-180) to prepare a solution of viscosity 35 cP (23 DEG C), and the prepared solution was 100 nm in pore size. The debris was removed by filtration using an ultrapolyethylene (hereinafter abbreviated as UPE) membrane filter.

18 ml of this solution was added dropwise onto a quartz glass substrate, spin-coated by rotating for 60 seconds at a speed of 600 rpm, followed by heat drying for 30 minutes on a plate heated to 230 ° C., and then drying at 100 ° C. for 50 minutes in a convection oven. To form a pellicle film. An aluminum frame coated with an adhesive was attached thereto, and the pellicle film was peeled off. The thickness of the pellicle film was 284 nm.

(Example 2)

A pellicle film was prepared in the same manner as in Example 1 except that the pellicle film had a thickness of 282 nm by adjusting the concentration of the solution and the rotational speed during film formation.

(Comparative Example 1)

A pellicle film was produced in the same manner as in Example 1 except that the pellicle film had a thickness of 140 nm and the rotational speed of the pellicle film was adjusted.

(Comparative Example 2)

A pellicle film was produced in the same manner as in Example 1 except that the pellicle film thickness was adjusted to 240 nm by adjusting the concentration of the solution and the rotational speed during film formation.

(Comparative Example 3)

A pellicle film was produced in the same manner as in Example 1 except that the concentration of the solution and the rotational speed of the pellicle film formation were adjusted to set the film thickness of the pellicle film to 279 nm.

(Comparative Example 4)

A pellicle film was produced in the same manner as in Example 1 except that the concentration of the solution and the rotational speed of the pellicle film formation were adjusted to set the film thickness of the pellicle film to 288 nm.

(Comparative Example 5)

A pellicle film was produced in the same manner as in Example 1 except that the concentration of the solution and the rotational speed of the pellicle film formation were adjusted to set the thickness of the pellicle film to 310 nm.

(Comparative Example 6)

A pellicle film was produced in the same manner as in Example 1 except that the viscosity of the fluorine resin solution was adjusted to 45 cP (23 ° C.), and the spin coating was carried out by spinning at 60 seconds at a speed of 730 RPM to make the thickness of the pellicle film 284 nm.

(Comparative Example 7)

A pellicle film was produced in the same manner as in Example 1 except that the viscosity of the fluorine resin solution was adjusted to 40 cP (23 ° C.), and 60 seconds was rotated and spin-coated at a speed of 640 RPM to make the film thickness of the pellicle film 284 nm.

TABLE 1

Thickness of pellicle film (nm) % Transmittance at incident angle of 0 ° Transmittance (%) at incident angle of 20 ° Poor appearance Example 1 284 99.5 99.6 X Example 2 282 99.7 99.3 X Comparative Example 1 140 - - - Comparative Example 2 240 89.8 91.9 X Comparative Example 3 279 99.9 98.5 X Comparative Example 4 288 98.4 99.9 X Comparative Example 5 310 89.5 92.7 X Comparative Example 6 284 99.4 99.5 O Comparative Example 7 284 99.4 99.5 O

Using the UV transmittance meter HP8453, the transmittance of light having a wavelength of 193 nm was measured, and the measurement results are shown in Table 1. Comparative Example 1 was broken in the process of separating the pellicle membrane and could not be measured.

As can be seen from Table 1, in Examples 1 to 2 satisfying Equations 1 to 5, a pellicle film having a transmittance of 99.3% or more was obtained, and Comparative Examples 2 to 5 not satisfying Equations 1 to 5 Silver transmittance was relatively low.

In addition, it can be seen that in the case of Comparative Examples 6 and 7 having a high viscosity, appearance defects occurred. Therefore, in the immersion exposure pellicle which requires high resolution, the viscosity of the solution is preferably 30 to 35 cP (23 ° C).

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made by those skilled in the art within the technical idea of the present invention. Is obvious.

FIG. 1 is a graph comparing the measured values of the light transmittances according to the incident angles of the pellicle films having a film thickness of 284 nm and the values calculated by Equations 1 to 5 when the incident angles are 0 ^° or more and 20 ^° or less.

Claims (7)

As a pellicle used in semiconductor lithography, When the light source for exposure is an ArF excimer laser having a wavelength of 193 nm and the incident angle in the pellicle film is 0 ° or more and 20 ° or less, A pellicle for an immersion exposure apparatus, wherein light transmittance is 99.3% or more. The method of claim 1, A pellicle for the immersion exposure apparatus, characterized in that the thickness of the pellicle film satisfies the following equations (1) to (5). [Equation 1] R = r (1-cosX) &Quot; (2) " r = 2 {(n-1) / (n + 1)} ² &Quot; (3) " X = 4πnd / λ &Quot; (4) " T (%) = 1-R = 100 * {1-2 {(n-1) / (n + 1)} ² * (1-cos (4πnd / λ * cosθ))} [Equation 5] d = mλ / (2n * cosθ) (m = 0, 1, 2, ...) (In the above formula, R: reflectance considering interference, r: reflectance not considering interference, n: refractive index of pellicle film, d: film thickness of pellicle (nm), λ: wavelength of light source for exposure (nm), T: transmittance (%), θ: incident angle) The method of claim 1, Refractive index is from 1.38 to 1.39, A pellicle for an immersion exposure apparatus, wherein the film thickness is 282 nm to 284 nm. The method according to any one of claims 1 to 3, The pellicle film is a pellicle for an immersion exposure apparatus, characterized in that the viscosity is made of a fluorine resin solution of 30 to 35 cP at 23 ℃. The method of claim 1, A pellicle for an immersion exposure apparatus, characterized by having a maximum transmittance at an incident angle of 15 ± 0.1 °. A method of manufacturing a pellicle for an immersion exposure apparatus used for semiconductor lithography by applying, drying and peeling an organic solution for forming a pellicle film on a substrate, Preparing a fluororesin solution having a viscosity of 30 to 35 cP at 23 ° C .; And Applying, drying, and peeling off the fluororesin solution on the substrate; The step of applying the fluororesin solution, A method of manufacturing a pellicle for an immersion exposure apparatus, characterized in that the step of applying so that the thickness of the pellicle film after drying satisfies the following formula (1) to (5). [Equation 1] R = r (1-cosX) &Quot; (2) " r = 2 {(n-1) / (n + 1)} ² &Quot; (3) " X = 4πnd / λ &Quot; (4) " T (%) = 1-R = 100 * {1-2 {(n-1) / (n + 1)} ² * (1-cos (4πnd / λ * cosθ))} [Equation 5] d = mλ / (2n * cosθ) (m = 0, 1, 2, ...) (In the above formula, R: reflectance considering interference, r: reflectance not considering interference, n: refractive index of pellicle film, d: film thickness of pellicle (nm), λ: wavelength of light source for exposure (nm), T: transmittance (%), θ: incident angle) A method of manufacturing a pellicle for an immersion exposure apparatus used for semiconductor lithography by applying, drying and peeling an organic solution for forming a pellicle film on a substrate, Preparing a fluororesin solution having a viscosity of 30 to 35 cP at 23 ° C .; And Applying, drying, and peeling off the fluororesin solution on the substrate; The step of applying the fluororesin solution, A method of manufacturing a pellicle for an immersion exposure apparatus, characterized in that the step of applying so that the thickness of the pellicle film after drying is 282nm to 284nm.

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