KR20120081667A - Pelicle membrane and method of forming pelicle membrane - Google Patents

Abstract

PURPOSE: A pellicle film and a method for manufacturing the same are provided to secure almost constant transmittance regardless of the deviation of film thicknesses. CONSTITUTION: A method for manufacturing a pellicle film includes the following: a fluorine resin solution is prepared; a substrate is arranged on a cooling plate with temperature deviation of ±0.1 degrees Celsius or less; the substrate is left on the cooling plate for a pre-set period of time to uniform the temperature of the substrate. The substrate is mounted on a coating unit; the fluorine resin solution is applied to the substrate, and a drying process and an exfoliating process are followed. The thickness of the dried pellicle film becomes in a range between 270 and 286 nm.

Description

Pellicle membrane and its manufacturing method {PELICLE MEMBRANE AND METHOD OF FORMING PELICLE MEMBRANE}

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 used for an ArF excimer laser used as a light source for high resolution patterning.

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.

The conventional pellicle for ArF excimer laser has a problem that the thickness of a part of the film becomes thin due to the light energy of the ArF excimer laser, causing variation in the film thickness. Differences in the film thickness cause variations in the transmittance and cause a problem in that a high-resolution exposure pattern cannot be obtained.

The present invention is to solve the above-described problems, the pellicle for ArF excimer laser that does not significantly change the transmittance due to the variation in the film thickness, the variation in transmittance does not occur even if the variation in the film thickness occurs for a long time The purpose is to provide.

In order to achieve the above object, the present invention provides a method for manufacturing a pellicle film 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, the method comprising: preparing a fluorine resin solution ; And

Placing the substrate on a cooling plate having a temperature deviation of ± 0.01 ° C. or less and maintaining the substrate for a predetermined time to keep the temperature of the substrate constant; Mounting the substrate to a coating apparatus; And applying, drying, and peeling off the fluororesin solution on the substrate.

The step of applying the fluorine resin solution is preferably a step of applying so that the thickness of the pellicle film after drying 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 step of applying the fluororesin solution is preferably a step of applying so that the thickness of the pellicle film after drying is 270nm to 286nm.

Further, according to the present invention, a pellicle film used for semiconductor lithography, 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 incidence angle in the pellicle film is vertical, and the exposure is cumulative. When the energy is 6 kJ, a pellicle film is provided, characterized in that the change in light transmittance is 1% or less.

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

In addition, the pellicle film has a refractive index of 1.38 to 1.39 and a thickness of 270 nm to 286 nm.

The pellicle according to the present invention does not change the transmittance largely due to the variation in the film thickness. Therefore, even if the pellicle is used for a long time and the variation in the film thickness is caused by the light energy of the ArF excimer laser, there is an effect that the variation in the transmittance is not large.

Hereinafter, the present invention will be described in detail.

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.

A solution in which the fluorine resin constituting the prepared pellicle film is dissolved is coated on a substrate at a constant temperature, and dried at a temperature near the boiling point of the solvent to form a pellicle film. In order to keep the temperature of the substrate constant, the substrate is placed on a cooling plate with a temperature deviation of ± 0.01 ℃ or less and maintained for a certain time to make the temperature of the substrate constant. As the substrate has a smooth surface, silicon wafers, quartz glass, ordinary glass, and the like may be used, but quartz glass is preferably used. As a method of coating, various well-known methods can be used. For example, a pellicle film can be formed on the substrate by a coating method such as roll coating, casting, spin coating, water casting, dip coating or Langmuir Blodgett, with spin coating being preferred. 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 thickness of the pellicle film should satisfy the following requirements.

First, the pellicle film preferably has a high light transmittance. Specifically, the light transmittance is preferably 99.3% or more. 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)

&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)

That is, if the above equation is calculated under the condition that θ = 0 °, 99.3% ≤ T (%), it is possible to obtain the film thickness of the required pellicle film according to the refractive index of the pellicle film and the wavelength of the light source used. 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 for the pellicle film, and when the incident angle is vertical, the pellicle film thickness is 1 m. , 2, 3, 4, 5, it is calculated to increase to about 69.6nm, 139nm, 208nm, 278nm, 348nm. 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.

Second, even if the thickness of the pellicle film changes, it is preferable that the transmittance of the exposure light does not change significantly. If the exposure light passes longer, the thickness of the pellicle film gradually decreases due to the cumulative exposure energy. If the transmittance changes significantly with the decrease in the thickness of such a film, a high-resolution exposure pattern cannot be obtained, and the pellicle film must be replaced frequently. As a result of the experiment, even if the thickness of the pellicle film is changed, the thickness of the pellicle film is advantageous in order not to significantly change the transmittance of the exposure light.

Third, the thickness distribution of the pellicle film should be small. In order to reduce the thickness distribution of the film, the temperature of the substrate on which the solution in which the fluorine resin constituting the pellicle film is dissolved is coated should be uniform. In order to make the temperature of a board | substrate uniform, as mentioned above, the board | substrate is put on a cooling plate with a temperature deviation of +/- 0.01 degreeC or less, and it maintains for a predetermined time, and makes temperature of a board | substrate constant. The temperature of the cooling plate is maintained at the same temperature as where the coating is made. The inside of the cooling plate is tightly wound spirally in a pipe in which the cooling water flows to reduce the temperature variation.

Next, it is dried at a temperature near the boiling point of the solvent to form a pellicle film.

Next, the dried pellicle film is peeled off from the substrate. The pellicle membrane can be detached by applying a cell jig with a cellophane tape or adhesive to the pellicle membrane, and lifting the cellophane tape or the jig from one end by hand or mechanical means.

The separated pellicle film is attached to an aluminum frame coated with an adhesive, an adhesive, and the like, and the pellicle is completed by cutting and removing unnecessary films on the outside of the frame.

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 40cP (23 ° C) solution was prepared using a fluorine resin (Cytop CTX-S) manufactured by Asahi Glass Co., Ltd. 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 cooled in a cooling plate, spin coated for 60 seconds at a speed of 600 rpm, then heated and dried for 30 minutes on a plate heated to 230 ° C., and then again in a convection oven. It dried at 50 degreeC for 50 minutes, and formed the pellicle film | membrane. 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 a viscosity 38c (23 ° C.) solution was prepared, the rotational speed during pellicle film formation was adjusted to 550 rpm, and the thickness of the pellicle film was 284 nm.

(Comparative Example 1)

The pellicle membrane was produced in the same manner as in Example 1 except that the viscosity of the pellicle membrane was adjusted to 80 cP (23 ° C.), and spin-coated by rotating for 60 seconds at a speed of 400 RPM. .

% Change in transmittance according to cumulative exposure energy 2kJ 4kJ 6kJ Example 1 0.2 0.4 0.8 Example 2 0.15 0.5 0.9 Comparative Example 1 1.3 2.5 3.8

Using a 193 nm accelerated exposure machine, the transmittance change rate (%) was measured while increasing energy, and the measurement results are shown in Table 1. As can be seen from Table 1, when the cumulative exposure energy is 2kJ, the change in transmittance was 1.3% in Comparative Example 1, but in Examples 1 and 2, the change in transmittance was 0.2 and 0.15%. It decreased a lot. Similar results were obtained when the cumulative exposure energy was 4kJ and 6kJ.

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.

Claims (6)

A method of manufacturing a pellicle film 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; And
Placing the substrate on a cooling plate having a temperature deviation of ± 0.01 ° C. or less and maintaining the substrate for a predetermined time to keep the temperature of the substrate constant;
Mounting the substrate to a coating apparatus; And
And coating, drying, and peeling the fluorine resin solution on the substrate. The method of claim 1,
The step of applying the fluororesin solution,
Method of producing a pellicle film, characterized in that the step of coating so that the thickness of the pellicle film after 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
[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 exposure light source (nm), T: transmittance (%), θ: incident angle) The method of claim 1,
The step of applying the fluororesin solution,
Method of producing a pellicle film, characterized in that the step of applying so that the thickness of the pellicle film after drying to 270nm to 286nm. As a pellicle film 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 vertical,
A pellicle film having a light transmittance of 99.3% or more and a change in light transmittance of 1% or less when the cumulative exposure energy is 6 kJ. The method of claim 4, wherein
The thickness of the pellicle film is a pellicle film, characterized in that 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
[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 method of claim 4, wherein
Refractive index is from 1.38 to 1.39,
A pellicle film, characterized in that the thickness is 270nm to 286nm.