KR20200103223A - Pellicle membrane for lithography - Google Patents

Abstract

The present invention relates to a pellicle film having a uniform transmittance, which comprises a first film having a first thickness and a second film positioned on the first film and having a second thickness, wherein the first thickness and the second thickness are different from each other, the difference between the first thickness and the second thickness is within 5% of the first thickness, and the transmittance curve of the first film and the transmittance curve of the second film have a phase difference of 170 degrees to 190 degrees.

Description

Pellicle membrane for lithography {PELLICLE MEMBRANE FOR LITHOGRAPHY}

The present disclosure relates to a pellicle film for lithography.

A lithography process is a process used when manufacturing a semiconductor device or a display substrate. In the lithography process, an exposure process is performed on a semiconductor device or a display substrate through a photo-mask on which a pattern to be transferred is formed. In this case, a pellicle including a transparent pellicle film may be attached to the photo mask to prevent damage to the pattern or contamination due to foreign substances such as dust.

The embodiments are to provide a pellicle for lithography, which can make the transmittance uniform by stacking the pellicle film as a double layer to offset the transmittance curve of the two films, thereby reducing process dispersion.

A pellicle film according to an embodiment includes a first film having a first thickness and a second film positioned on the first film and having a second thickness, wherein the first thickness and the second thickness are different from each other, and the second film The difference between the first thickness and the second thickness is within 5% of the first thickness, and the transmittance curve of the first film and the transmittance curve of the second film have a phase difference of 170 degrees to 190 degrees.

The first material included in the first layer and the second material included in the second layer may be the same.

A separation membrane may be positioned between the first membrane and the second membrane.

The thickness of the separation membrane may be within 5% of the thickness of the first layer or the second layer.

The first thickness may be 1.5 μm to 3.0 μm.

When the transmittance curve of the first film has a first transmittance distribution in a first band including the wavelength of light supplied from the exposure source, the transmittance distribution may be 35% or less of the first transmittance distribution, and the transmittance distribution is the It is the difference between the maximum and minimum values of the transmittance in the first band.

The first band may have a wavelength of about 350 nm to 380 nm.

The transmittance distribution may be 2.7% or less of the total transmittance.

The first material and the second material may be cellulose acetate butyrate (CAB).

An anti-reflection film is positioned on the second film or under the first film, and the anti-reflection film may include fluorine (F).

The first material included in the first layer and the second material included in the second layer may be different from each other.

A pellicle film according to an embodiment includes a first film having a first thickness and a second film positioned on the first film and having a second thickness, and the first material included in the first film and the second film include The second materials are different from each other, the difference between the first thickness and the second thickness is within 1% of the first thickness, and the transmittance curve of the first film and the transmittance curve of the second film have a phase difference of 170 degrees to 190 degrees. Have.

The first material may be cellulose acetate butyrate (CAB).

The second material may be cellulose acetate propionate (CAP).

The first thickness may be 1.5 μm to 3.0 μm.

When the transmittance curve of the first film has a first transmittance distribution in a first band including the wavelength of light supplied from the exposure source, the transmittance distribution may be 35% or less of the first transmittance distribution, and the transmittance distribution is the It is the difference between the maximum and minimum values of the transmittance in the first band.

The first band may have a wavelength of about 350 nm to 380 nm.

The transmittance distribution may be 2.7% or less of the total transmittance.

An anti-reflection film is positioned on the second film or under the first film, and the anti-reflection film may include fluorine (F).

A separation membrane may be positioned between the first membrane or the second membrane.

According to embodiments, the transmittance curves of the two membranes, including two membranes having different transmission properties, cancel each other, thereby making the transmittance uniform, thereby increasing the precision and resolution of patterning, and reducing process dispersion. The quality of the device can be improved.

1 is a cross-sectional view illustrating a photo mask to which a pellicle film is attached according to an exemplary embodiment.
2 is a perspective view illustrating a photo mask to which a pellicle film is attached according to an exemplary embodiment.
3 is a cross-sectional view showing a pellicle film according to an embodiment.
4 is a graph showing a transmittance curve of a pellicle membrane according to an embodiment.
5 is a graph showing a wavelength period in a specific wavelength band according to the thickness of the pellicle film.
6 is a graph showing a transmittance curve of a pellicle membrane according to an embodiment.
7 and 8 are graphs showing transmittance curves in which thickness distribution of a pellicle film is reflected according to an exemplary embodiment.
9 to 11 are cross-sectional views each showing a pellicle film according to another embodiment.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In order to clearly describe the present invention, parts irrelevant to the description have been omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, so the present invention is not necessarily limited to the illustrated bar. In the drawings, the thicknesses are enlarged to clearly express various layers and regions. And in the drawings, for convenience of description, the thickness of some layers and regions is exaggerated.

In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" or "on" another part, this includes not only "directly over" another part, but also a case where another part is in the middle. . Conversely, when one part is "directly above" another part, it means that there is no other part in the middle. In addition, to be "on" or "on" the reference part means that it is located above or below the reference part, and does not necessarily mean that it is located "above" or "on" the direction opposite to the gravity. .

In addition, throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

In addition, throughout the specification, when referred to as "on a plane", it means when the target portion is viewed from above, and when referred to as "cross-sectional view", it means when the cross-section of the target portion vertically cut is viewed from the side.

Hereinafter, a photomask to which a pellicle film is attached according to an exemplary embodiment will be described with reference to FIGS. 1 to 3. 1 is a cross-sectional view showing a photomask with a pellicle film attached according to an embodiment, FIG. 2 is a perspective view showing a photomask with a pellicle film attached according to an embodiment, and FIG. 3 is a pellicle film according to an embodiment It is a graph showing the transmittance characteristics.

Referring to FIGS. 1 and 2, a photo mask according to an exemplary embodiment includes a substrate 10, a pattern film 20, and a pellicle 30.

A pattern film 20 is positioned on a transparent substrate 10 made of glass or quartz. In the pattern film 20, a pattern 21 to be patterned is formed on a substrate (wafer, not shown) of a display device. In the process of forming a pattern using the pattern film 20 as a mask, the pellicle 30 is attached to protect the pattern film 20 from external contamination by impurities.

The pellicle 30 includes a pellicle frame 31 and a transparent pellicle film 300. The pellicle 30 may be attached on the substrate 10 to which the pattern film 20 is attached using the pellicle frame 31. The pellicle frame 31 may be attached to the pattern film 20 through the adhesive layer 40. A protective layer (not shown) is interposed between the pattern film 20 and the adhesive layer 40 to prevent damage to the pattern film 20.

The pattern 21 is formed on a substrate (wafer, not shown) of the display device by exposing the pattern film 20 as a mask through the transparent pellicle layer 300. At this time, the pellicle film 300 is positioned away from the pattern film 20 through the pellicle frame 31 at a predetermined distance. Accordingly, the surface of the pellicle layer 300 is out of the focus position of light used during exposure during a lithography process of forming a pattern on a substrate (wafer, not shown) of the display device. Accordingly, impurities such as dust or particles on the pellicle layer 300 may not be patterned. That is, dust or foreign matter on the pellicle film 300 does not affect the pattern transferred through the pattern film 20. In this way, the pellicle 30 may prevent damage to the pattern film 20 or contamination due to external impurities in the lithography process.

The pellicle layer 300 may have a multilayer structure including a first layer (not shown) and a second layer (not shown), through which destructive interference of a transmittance curve having a sinusoidal shape of each layer occurs. Accordingly, it is possible to obtain a uniform transmittance by reducing the dispersion of transmittance for light supplied by the exposure source of the pellicle film 300. This may have an effect of increasing the precision and resolution of patterning by reducing an error of a pattern formed by a lithography process. A detailed stack structure and effect of the pellicle film 300 will be described later in detail.

Hereinafter, a pellicle membrane according to an exemplary embodiment and its transmission characteristics will be described in more detail with reference to FIGS. 3 and 4. 3 is a cross-sectional view illustrating a pellicle film according to an embodiment, and FIG. 4 is a graph showing transmittance according to a wavelength of a pellicle film according to an embodiment.

Referring to FIG. 3, the pellicle film 300 according to an embodiment includes a first film M1, a second film M2, and a separation film 310.

The first layer M1 and the second layer M2 may include the same material. When the thickness of the first layer M1 is the first thickness d1 and the thickness of the second layer M2 is the second thickness d2, when the two layers M1 and M2 contain the same material The first thickness d1 and the second thickness d2 are different from each other. Hereinafter, the difference between the first thickness d1 and the second thickness d2 is referred to as the thickness difference Δd. A detailed description of the thickness difference (Δd) will be described later.

Hereinafter, a double layer structure of the pellicle layer 300 according to an exemplary embodiment will be described with reference to FIG. 4. 4 is a graph showing transmittance according to wavelength of a pellicle film according to an exemplary embodiment. Referring to FIG. 4, the horizontal axis represents the wavelength (nm) of light supplied from the exposure source, hereinafter referred to as the exposure source wavelength (λ), and the vertical axis represents the exposure source wavelength (λ) of the pellicle film 300. Indicates transmittance. 4, a first curve L1, which is a transmittance curve of the first film M1, a second curve L2, which is a transmittance curve of the second film M2, and a first curve L1 and a second curve L2. A first summation curve L12, which is a transmittance curve obtained by summing up, is shown. Each transmittance curve L1, L2, L12 has a sinusoidal shape and includes one or more ridges and valleys.

Hereinafter, the transmittance of each of the transmittance curves L1, L2, and L12 will be described with respect to the wavelength period T1 centered on the first exposure source wavelength λ1.

As the display device develops to high quality and high resolution, the degree of integration of circuits in the display device increases, and accordingly, patterning with high resolution is required. In order to form a fine pattern, it is necessary to increase the patterning resolution (R). The smaller the patterning resolving power (R) is, the higher the resolving power is, and the patterning resolving power (R) in the lithography process is according to the following [Equation 1].

The patterning resolution R depends on a value obtained by dividing the exposure source wavelength λ by a numerical aperture (NA), and is determined by multiplying this by a coefficient k ₁ taking into account exposure conditions and process conditions. The numerical aperture (NA) may represent the size of an aperture that limits the path of light, and the larger the numerical aperture (NA), the higher the patterning resolution (R). According to [Equation 1], the patterning resolution R increases as the exposure source wavelength λ decreases. Accordingly, the patterning resolution R can be increased by limiting the exposure source wavelength λ to a short wavelength instead of a complex wavelength to expose the light. For example, light supplied from the exposure source may be limited to a short wavelength band by filtering or the like. Here, the complex wavelength may include a short wavelength and several wavelength bands greater than the short wavelength.

In the lithography process using the pellicle film according to an exemplary embodiment, exposure may be performed using light of a single wavelength band in which the exposure source wavelength λ is the first exposure source wavelength λ1. However, when the exposure source wavelength λ is limited to a single wavelength band instead of a complex wavelength, the dispersion of the transmittance of the pellicle film increases compared to exposure with light having a composite wavelength, resulting in a problem that the transmittance becomes uneven. This is because when exposure is performed using light of a composite wavelength, the transmittance is calculated as an average value for each exposure source wavelength λ included in the composite wavelength, so that the dispersion of transmittance is relatively small. As such, when the transmittance of the pellicle film is non-uniform, the line width (CD) to be patterned through the exposure process also varies, thereby reducing the accuracy of patterning and increasing process dispersion.

Accordingly, in order to make the transmittance of the pellicle film uniform according to an exemplary embodiment, the pellicle film is formed as a double film to offset the transmittance curve of each film, thereby obtaining a uniform transmittance. Hereinafter, the transmittance distribution in one wavelength period T1 including the first exposure source wavelength λ1 will be described in more detail.

The first curve L1 has a maximum transmittance x at the first exposure source wavelength λ1 and forms a floor. Hereinafter, the adjacent ridges and ridges, or between valleys and valleys of the first curve L1 are referred to as the wavelength period T1, and correspond to the wavelength period T1 centered on the first exposure source wavelength λ1. The region is referred to as the first band P1. The first band P1 has a width of half a period T1/2 on both sides centering on the first exposure source wavelength λ1. In this case, the wavelength period T1 may not be constant for all exposure source wavelengths λ depending on the material or thickness of the first layer M1.

The transmittance of the first layer M1 may have a difference between adjacent ridges and valleys according to a characteristic or thickness of a material included in the first layer M1 in the first band P1. In the following, this difference in transmittance is referred to as transmittance distribution. As shown in FIG. 4, the difference between the maximum transmittance (x) and the minimum transmittance (y) of the first curve L1 in the first band P1 may be referred to as a first transmittance distribution g1. That is, the first film M1 has a first transmittance distribution g1, and has a non-uniform transmittance in the first band P1.

Accordingly, the pellicle film according to the exemplary embodiment further includes a second film M2 having a different thickness from the first film M1 to uniform transmittance for a specific wavelength band. Hereinafter, the second layer M2 and the relationship between the first layer M1 and the second layer M2 will be described.

The second layer M2 has a second thickness d2 and is positioned on the first layer M1. Although the second layer M2 includes the same material as the first layer M1, the second layer M2 has different transmittance characteristics due to the difference in thickness Δd. The thickness difference Δd represents the difference between the first thickness d1 and the second thickness d2. By appropriately adjusting the thickness difference Δd, the second curve L2 can be moved by a half period T1/2 compared to the first curve L1. In this case, the second curve L2 has a minimum transmittance y at the first exposure source wavelength λ1 and may form a valley. That is, the second curve L2 may have a phase opposite to the first curve L1 in the first band P1. For example, the phase difference between the two curves L1 and L2 in the first band P1 may be about 170° to about 190°, and in particular, may be about 180°.

In this way, the pellicle film 300 includes the double film of the first film M1 and the second film M2, and light supplied from the exposure source passes through both films M1 and M2, and the pellicle film 300 The final transmittance of) is the result of summing the transmittances of the two films (M1, M2). That is, the transmittance of the pellicle film 300 has a distribution of a first summation curve L12 obtained by summing the first curve L1 and the second curve L2.

Since the first curve L1 and the second curve L2 have a phase difference of almost 180 degrees in the first band P1, the two curves L1 and L2 may cause destructive interference. Accordingly, the amplitude of the first summing curve L12 is significantly reduced in the first band P1 and thus has a substantially flat shape. The difference between the maximum transmittance (u) and the minimum transmittance (v) of the first sum curve L12 in the first band P1 is referred to as a second transmittance distribution (g2). According to the destructive interference of the two curves L1 and L2, the second transmittance distribution g2 may be significantly reduced than the first transmittance distribution g1.

The two curves (L1, L2) are the transmittances of the first film (M1) and the second film (M2), which are single films, respectively, and the transmittance of the pellicle film 300 having a double film is compared with the two curves (L1, L2). Thus, it can have a flat shape. Specifically, when the transmittance when all the light of a specific wavelength is transmitted is the total transmittance (a), the ratio of the second transmittance dispersion (g2) to the total transmittance (a) (g2/a) is within about 2.7%. May be, for example, within 1%. The ratio (g2/g1) of the second transmittance dispersion (g2) to the first transmittance dispersion (g1) may be within about 33.8%, for example, within 12.5%.

In this way, the transmittance of the pellicle film 300 can be made uniform by canceling the transmittance curves of the two films including the double film having different thicknesses. As the transmittance dispersion of the pellicle film decreases, the error of the pattern patterned on the substrate also decreases, thereby reducing process dispersion, and high-resolution patterning is possible even when a single wavelength band is used as the exposure source wavelength.

In particular, the two single films M1 and M2 of the pellicle film 300 have a thickness difference (Δd) that can cancel the transmittance curve of each single film. That is, the second layer M2 is formed to be thicker or thinner than the first layer M1 by the thickness difference Δd, so that the second curve L2 is formed in the first band P1 compared to the first curve L1. ) Can be moved by half a period (T1/2). Accordingly, the two transmittance curves L1 and L2 in the first band P1 cause destructive interference with each other, so that the distribution of transmittance of the pellicle film 300 can be significantly reduced.

The first exposure source wavelength λ1 may be about 360 ㎚ to 370 ㎚, especially 365 ㎚. The first band may be formed in a region of about 350 nm to 380 nm. That is, the pellicle film according to an exemplary embodiment may have a uniform transmittance for light in a single wavelength band of about 350 nm to 380 nm.

The above-described first band P1 is only an example of a specific wavelength band, and non-uniformity of transmittance may be improved in a band of at least one wavelength period T1 or more. As an example, as shown in FIG. 4, non-uniformity in transmittance may be reduced even in regions corresponding to one wavelength period T1 on both sides of the first band P1. Transmittance of light having an exposure source wavelength λ of about 330 nm to about 400 nm may be uniform.

Returning to FIG. 3 again, a separation membrane 310 is positioned between the first membrane M1 and the second membrane M2. The separation membrane 310 may serve to separate two membranes M1 and M2 including the same material. The separator 310 may be formed of a known material, and a material having a low refractive index and low absorption of light may be advantageous. The separator 310 may be a fluorine-based material including fluorine (F), and may be, for example, a fluoropolymer. Alternatively, the separator 310 may include an acrylic polymer, but the material of the separator 310 does not limit the present invention.

The thickness of the separator 310 may be within about 5% of the thickness of the first film M1 or the second film M2, but this is only an example and does not limit the present invention.

The pellicle film 300 according to the embodiment of FIG. 3 includes an anti-reflective coating layer 330. The antireflection layer 330 may be a fluorine-based material including fluorine (F), and may be, for example, a fluoropolymer, but the material of the antireflection layer 330 is not limited thereto.

The thickness of the antireflection layer 330 may be about 0.1 μm, but is not limited thereto. The thickness of the antireflection layer 330 may be within about 5% of the thickness of the first layer M1 or the second layer M2. In FIG. 3, the anti-reflection layer 330 is positioned above the pellicle layer 300, but may be positioned below the pellicle layer 300.

Hereinafter, the transmittance characteristics of the pellicle membrane according to an exemplary embodiment will be described with reference to FIGS. 5 to 8, 3 and 4. Hereinafter, descriptions of the same contents as those of the above-described embodiment may be omitted, and distinguished features will be mainly described.

5 is a graph showing a wavelength period in a specific wavelength band according to the thickness of the pellicle film, FIG. 6 is a graph showing the transmittance curve of the pellicle film according to an embodiment, and FIGS. 7 and 8 are It is a graph showing the transmittance curve reflecting the thickness distribution of the pellicle film.

5 to 8, the first film M1 and the second film M2 of the pellicle film 300 contain the same material of the nitro-cellulose series, and the first exposure source wavelength λ1 When is 365 nm, it will be described as an example. The first film M1 may include cellulose acetate butyrate (CAB). Cellulose acetate butyrate (CAB) is as shown in [Chemical Formula 1] below.

However, the material of the first layer M1 and the second layer M2 is not limited thereto, and any material having a transmittance curve in a sinusoidal wave shape may be used.

Referring to FIG. 5, when the first film M1 contains cellulose acetate butyrate (CAB), the relationship between the wavelength period T1 according to the first thickness d1 of the first curve L1 of FIG. 4 is Is shown. As shown in FIG. 5, it can be seen that the thinner the first thickness d1 in the range of about 1.5 μm to about 4 μm, the longer the wavelength period T1. For example, when the first thickness d1 is 2 μm, the wavelength period T1 is about 24 nm. The longer the wavelength period T1, the wider the interval between the curves L1 and L2, so that when the two curves L1 and L2 are summed, the mutual influence may be reduced. That is, the two curves L1 and L2 of FIG. 4 can be effectively canceled out.

In consideration of the effects of such destructive interference and the mechanical strength of the pellicle film, the first thickness d1 may be about 1.5 µm to about 3.0 µm, and particularly 2.0 µm to 2.5 µm.

6 to 8 are graphs showing transmittance characteristics when the pellicle membrane according to the exemplary embodiment described in FIG. 5 is applied to the exemplary embodiment of FIGS. 3 and 4. Specifically, as described above, the first film M1 contains cellulose acetate butyrate (CAB), the first exposure source wavelength (λ1) is 365 nm, the first thickness (d1) is 2 μm, and FIG. The wavelength period T1 of the first curve L1 of 4 will be described based on the case of about 24 nm. The first band P1 denotes a region having a width of a wavelength period T1 of 24 nm with a center of the first exposure source wavelength λ1 of 365 nm.

Referring to FIG. 6, the horizontal axis represents the wavelength (nm) of the exposure source, and the vertical axis represents the transmittance of the pellicle film when the total transmittance is 1. 6 shows a first curve L1, which is a transmittance curve of the first film M1, a second curve L2, which is a transmittance curve of the second film M2, and a first curve L1 and a second curve L2. A first summing curve L12 is shown by summing.

The first curve L1 has a transmittance of about 0.99, that is, about 99% at the first exposure source wavelength λ1 of 365 nm, and forms a floor. As described above, the first band P1 has a wavelength period T1 of 24 nm in width. The first curve L1 has a transmittance of about 0.91, that is, about 91% at both ends of the first band P1, and forms a valley. In this case, the first transmittance distribution g1 of the first curve L1 may have a value of about 0.08, that is, about 8%.

In this way, when a single wavelength band is used as the exposure source wavelength, it can be significantly increased compared to the dispersion of the average transmittance of the complex wavelength. Accordingly, patterning is performed unevenly, resulting in variations in the patterned line width (CD), resulting in an increase in process distribution and deterioration in display quality.

Accordingly, the pellicle film according to an embodiment may improve the uniformity of transmittance by canceling the transmittance curves of the two films including the double film, thereby reducing transmittance dispersion. In this case, in order for the first curve L1 and the second curve L2 to cause destructive interference, the phase difference between the two curves L1 and L2 should be about 180 degrees. That is, the second curve L2 should be moved to the left or right by about half a period T1/2 compared to the first curve L1. In this way, in order to move the second curve L2 by the half period T1/2, a certain amount of thickness difference Δd is required between the two films M1 and M2. In the pellicle film 300 according to the exemplary embodiment described with reference to FIG. 5, the thickness difference Δd according to the first thickness d1 is as shown in Table 1 below.

First thickness (d1)(um) Wavelength period (T1) (nm) Moving width (nm) of the second curve L2 Thickness difference (△d)(nm) 3.75 12 6 45 3.65 12 6 45 2.95 15 7.5 56.25 2.50 18 9 67.5 2.00 24 12 90

As described above, as the wavelength period T1 is longer, the two curves L1 and L2 are more effectively canceled, thereby obtaining a more uniform transmittance. As shown in [Table 1], as the first thickness (d1) approaches 2.0 µm, the wavelength period (T1) becomes longer, and the interval between each curve (L1, L2) becomes wider. Accordingly, the two curves (L1, L2) become It can be offset more effectively. Therefore, hereinafter, a case where the first thickness d1 is 2.0 μm will be described as an example.

When the first thickness (d1) is 2.0 μm, the wavelength period (T1) of the first curve (L1) is about 24 nm, and the movement width of the second curve (L2) for destructive interference is a half period (T1/2) Phosphorus is about 12 nm. For the second curve L2 to have a moving width of about 12 nm with respect to the first curve L1, the thickness difference Δd between the two films M1 and M2 is about 90 nm. At this time, the ratio (Δd/d1) of the thickness difference (Δd) to the first thickness (d1) is about 4.5%.

According to [Table 1], the ratio (△d/d1) of the thickness difference (△d) to the first thickness (d1) is about 2.5 µm, 2.95 µm, and 3.65 µm, respectively. It can be seen that it is 2.7%, 1.9% and 1.2%. That is, in the pellicle film 300 according to an embodiment, a ratio (Δd/d1) of the thickness difference Δd to the first thickness d1 may be about 1% to about 5%.

Returning to the case where the first thickness d1 is 2.0 μm, the second curve L2 has a transmittance of about 0.91, that is, about 91% at the first exposure source wavelength λ1 of 365 nm, and forms a valley. . At the same time, the second curve L2 has a transmittance of about 0.98, that is, about 98% at both ends of the first band P1, and forms a floor. In other words, the first curve L1 and the second curve L2 may have a phase difference of about 170 degrees to 190 degrees, and in particular, a phase difference of about 180 degrees. In this case, the transmittance distribution of the second curve L2 is not displayed, but is substantially the same as the first transmittance distribution g1, and may have a value of about 0.08, that is, about 8%.

The first summation curve L12 represents the transmittance distribution when the two curves L1 and L2 are summed. Referring to the first summing curve L12, the two curves L1 and L2 cause destructive interference with each other, so that a specific wavelength band, especially the first band P1, is formed flat with almost no transmittance distribution.

Specifically, the first summation curve L12 has a maximum transmittance and a minimum transmittance in the first band P1, and the difference between the maximum and minimum values is referred to as a second transmittance distribution g2. In FIG. 6, the second transmittance distribution g2 is illustrated to have a value within about 0.0067, that is, about 0.67%. This is a result of a significant decrease in the first transmittance distribution g1 due to destructive interference between the transmittance curves L1 and L2 of the two films M1 and M2 included in the pellicle film 300. In this case, a ratio (g2/g1) of the second transmittance distribution g2 to the first transmittance distribution g1 may be within about 8.4%.

As described above, by forming the pellicle film according to an embodiment as a double film, when the total transmittance is 1, that is, 100%, the dispersion of the transmittance in the specific wavelength band of the pellicle film, and in this embodiment, the first band P1 is 0.7 It can be improved within %. That is, uniform transmittance can be obtained without almost any distribution of transmittance, and thus, patterning with high resolution and accuracy is possible by reducing errors in patterns such as line width (CD) in the patterning process through a lithography process.

Hereinafter, with reference to FIGS. 7 and 8, the transmittance characteristics of the pellicle membrane in consideration of the distribution of the thickness of the pellicle membrane will be described.

The thickness d1 or d2 of the first film M1 or the second film M2 of the pellicle film 300 may not be constant over the entire area of the first film M1 or the second film M2. . According to this thickness distribution, the transmittance curves L1 and L2 are also shifted in position. Since the transmittance curves L1 and L2 have a sinusoidal shape, there is a difference in transmittance for a specific wavelength. Hereinafter, a description will be made by reflecting the movement of the second curve L2 according to the thickness distribution of the second layer M2.

[Table 2] shows the distribution of the film thickness according to the second thickness d2 and the shift width of the transmittance curve accordingly. The second thickness d2 represents the average thickness of the second layer M2 and has a thickness distribution according to the following table.

Second thickness (d2)(um) Film thickness dispersion (nm) Transmittance curve (L2) moving width (nm) 3.5 30 4 2.5 15 2

According to [Table 2], when the second thickness d2 is about 3.5 µm, the second film M2 has a thickness distribution of about 30 ㎚. In other words, the thickness at all points of the second layer M2 is not constant at 3.5 μm, but is distributed with a difference of about 30 nm over the entire area of the pellicle layer 300. Since the transmittance curve varies according to the film thickness as described above, the second curve L2 also shifts to a width of about 4 nm due to the dispersion of about 30 nm. Likewise, the second thickness d2 is about 2.5 μm. At this time, the second layer M2 has a thickness distribution of about 15 nm, and is reduced by half as compared to when the second thickness d2 is about 3.5 μm. Due to the dispersion of about 15 nm, the second curve L2 moves to a width of about 2 nm.

In view of the experimental results according to [Table 2], the moving width of the second curve L2 when the second thickness d2 is 2.0 μm can be expected to be smaller than when the second thickness d2 is 2.5 μm. However, in FIGS. 7 and 8, the movement width of the second curve L2 when the second thickness d2 is 2.5 μm will be reflected in order to reflect the maximum value of the transmittance distribution. In FIG. 7, the third curve L3 is 1 nm to the left (-1 nm) than the second curve L2, and the fourth curve L4 in FIG. 8 is 1 nm to the right compared to the second curve L2. It is shifted by the wavelength of (+1 nm), showing a total shift width of 2 nm.

Referring to FIG. 7, a first curve L1, a second curve L2, a third curve L3, and a second sum curve are shown. The first curve L1 and the second curve L2 are located at the same position as in FIG. 6, and the second curve L2 is shown by a dotted line. The third curve L3 is shifted to the left by 1 nm compared to the second curve L2 shown by the dotted line.

The second summing curve L13 is a curve representing the transmittance obtained by summing the first curve L1 and the third curve L3. Like the first summing curve L12 of FIG. 6, the second summing curve L13 also causes destructive interference between the first and third curves L1 and L3, resulting in a specific wavelength band, especially the first band P1. Is flattened compared to the existing curves L1 and L3.

However, with the shift of the second curve L2 by -1 nm, the second sum curve L13 has a second transmittance distribution g2' in the first band P1, and the second transmittance distribution g2' is It has a larger value than the second transmittance distribution g2 of the first summation curve L12 of FIG. 6. In this way, when the thickness distribution of the second film (M2) is reflected, the transmittance becomes non-uniform in the first band (P1) than in FIG. 6, and it can be confirmed that the transmittance is more uniform in the left side of the first band (P1). have.

Referring to FIG. 8, a first curve L1, a second curve L2, a fourth curve L4, and a third sum curve L14 are shown. The fourth curve L4 is shifted to the right by 1 nm compared to the second curve L2 shown by the dotted line.

The third summing curve L14 is a curve representing the transmittance obtained by summing the first curve L1 and the fourth curve L4. Like the first summing curve L12 of FIG. 6, the third summing curve L14 also causes destructive interference between the first and fourth curves L1 and L4, and thus a specific wavelength band, in particular, the first band P1. Is flattened compared to the existing curves L1 and L4.

However, due to the shift of the second curve L2 by +1 nm, the third summation curve L14 has a second transmittance dispersion (g2'') in the first band P1, and a second transmittance dispersion (g2''). ) Has a value greater than the second transmittance distribution g2 of the first summation curve L12 of FIG. 6. In this way, when the thickness distribution of the second film M2 is reflected, the transmittance becomes non-uniform in the first band P1 than in FIG. 6, and it is confirmed that the transmittance is more uniform in the right side of the first band P1. I can.

Specifically, in FIGS. 7 and 8, the second transmittance distributions g2' and g2' are shown to have a value within about 0.026, that is, about 2.6%. At this time, since the first transmittance distribution (g1) may have a value of about 0.08, that is, about 8%, the ratio (g2/g1) of the second transmittance distribution (g2) to the first transmittance distribution (g1) is about 35%. Can be within.

When the distribution of the film thickness is not considered, the second transmittance distribution (g2) of the first sum curve L12 is within 0.7% as in FIG. 6, but when the distribution of the film thickness is considered, in FIGS. 7 and 8 As described above, the second transmittance dispersion (g2', g2') may increase within about 2.4%.

6 to 8, since the pellicle film 300 includes a double film of the first film M1 and the second film M2, the transmittance in a specific wavelength band, especially the first band P1 By improving the dispersion to within about 2.4%, uniform transmittance can be obtained. The first to third summation curves L12, L13, and L14 may have a flat portion in a specific wavelength band because the regularity of the sine wave shape of the transmittance curves L1 and L2 of each of the single films M1 and M2 is broken. . Accordingly, variation of the patterned line width CD is also reduced, thereby reducing process dispersion. In this case, the difference in thickness (Δd) between the first layer M1 and the second layer M2 is about 1% to about 5%, and the two layers M1 and M2 may have substantially the same thickness.

Hereinafter, a pellicle membrane according to different embodiments will be described with reference to FIGS. 9 to 11. 9 to 11 are cross-sectional views each showing a pellicle film according to another embodiment. Hereinafter, descriptions of the same contents as those of the above-described embodiments may be omitted, and descriptions will be made focusing on features having differences.

Referring to FIG. 9, the pellicle layer 300 includes a first layer M1, a second layer M2, and a separation layer 310, and does not include an antireflection layer 330 unlike the embodiment of FIG. 3. . Since the anti-reflection film 330 is omitted, the thickness of the pellicle film 300 through which light supplied from the exposure source must transmit is reduced, so that the transmittance of the pellicle film 300 may be improved compared to the above-described embodiment.

Referring to FIG. 10, the pellicle layer 300 includes a first layer M1, a second layer N1, a separation layer 310, and an antireflection layer 330. The first layer M1 and the second layer N1 are separated by a separation layer 310, and the antireflection layer 330 is positioned on the second layer N1.

The first layer M1 and the second layer N1 include different materials. For example, the first membrane M1 may include cellulose acetate butyrate (CAB) and the second membrane N1 may include cellulose acetate propionate (CAP). Cellulose acetate propionate (CAP) is as shown in [Chemical Formula 2] below.

Unlike the above-described exemplary embodiment, in the present exemplary embodiment, the first layer M1 and the second layer N1 contain different materials and thus have different transmittance curves. At this time, cellulose acetate butyrate (CAB) and cellulose acetate propionate (CAP) have alkyl groups different from only one functional group as shown in Chemical Formulas 1 and 2. In other words, cellulose acetate butyrate (CAB) has one functional group of an ethyl group (-C ₂ H ₅ ), and cellulose acetate propionate (CAP) has one functional group of a propyl group (-C ₃ H ₇ ), Have the same skeleton.

Accordingly, the first layer M1 and the second layer N1 are formed in a specific wavelength band, such as the summing curves L12, L13, and L14, even with a thickness difference smaller than the thickness difference Δd of the above-described embodiment. Uniform transmittance can be obtained. The first layer M1 and the second layer N1 have the same thickness, and the difference in thickness (Δd) may be 0, and according to the embodiment, the difference in thickness (Δd) is about 5% of the first thickness (d1). , In particular, may be within 1%.

The material of the first film (M1) or the second film (N1) can be any material that can offset the transmittance curve of each of the films (M1, N1) in a specific wavelength band so as to deviate from the sinusoidal shape, and limits the present invention. I never do that.

In addition, the anti-reflection layer 330 may be positioned under the first layer M1 or may be omitted.

Referring to FIG. 11, the pellicle layer 300 includes a first layer M1, a second layer N1, and an antireflection layer 330. Unlike the embodiment of FIG. 10, since the first and second layers M1 and N1 contain different materials, there is no need to separate the two membranes M1 and N1 into the separator 310 of FIG. 10. The separator 310 may be omitted. Since the separation film 310 is omitted, the thickness of the pellicle film 300 through which light supplied from the exposure source must transmit is reduced, and thus the transmittance of the pellicle film 300 may be improved compared to the above-described embodiment.

The antireflection layer 330 is illustrated to be positioned above the second layer N1, but may be positioned below the first layer M1 or may be omitted.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

10: substrate 20: pattern film
21: pattern 30: pellicle
31: pellicle frame 300: pellicle membrane
M1: first film M2, N1: second film
310: separator 330: anti-reflection film
40: adhesive layer

Claims (20)

A first film having a first thickness and a second film positioned on the first film and having a second thickness,
The first thickness and the second thickness are different from each other, the difference between the first thickness and the second thickness is within 5% of the first thickness,
The transmittance curve of the first film and the transmittance curve of the second film have a phase difference of 170 degrees to 190 degrees. In claim 1,
The first material included in the first layer and the second material included in the second layer are the same pellicle layer. In claim 1,
A pellicle membrane in which a separation membrane is positioned between the first membrane and the second membrane. In paragraph 3,
The thickness of the separation membrane is within 5% of the thickness of the first membrane or the second membrane pellicle membrane. In claim 1,
The first thickness is 1.5 ㎛ to 3.0 ㎛ pellicle film. In claim 1,
When the transmittance curve of the first film has a first transmittance distribution in a first band including the wavelength of light supplied from the exposure source, the transmittance distribution is 35% or less of the first transmittance distribution,
The transmittance distribution is a difference between a maximum value and a minimum value of the transmittance in the first band. In paragraph 6,
The first band is a pellicle film having a wavelength of about 350 nm to 380 nm. In paragraph 6,
A pellicle membrane in which the transmittance dispersion is 2.7% or less of the total transmittance. In paragraph 2,
The first material and the second material are cellulose acetate butyrate (CAB) pellicle membrane. In claim 1,
An anti-reflection film is located above the second film or below the first film,
The antireflection film is a pellicle film containing fluorine (F). In claim 1,
A pellicle film in which the first material included in the first layer and the second material included in the second layer are different from each other. A first film having a first thickness and a second film positioned on the first film and having a second thickness,
The first material included in the first layer and the second material included in the second layer are different from each other,
The difference between the first thickness and the second thickness is within 1% of the first thickness,
The transmittance curve of the first film and the transmittance curve of the second film have a phase difference of 170 degrees to 190 degrees. In claim 12,
The first material is cellulose acetate butyrate (CAB) pellicle membrane. In claim 13,
The second material is cellulose acetate propionate (CAP) pellicle membrane. In claim 12,
The first thickness is 1.5 ㎛ to 3.0 ㎛ pellicle film. In claim 12,
When the transmittance curve of the first film has a first transmittance distribution in a first band including the wavelength of light supplied from the exposure source, the transmittance distribution is 35% or less of the first transmittance distribution,
The transmittance distribution is a difference between a maximum value and a minimum value of the transmittance in the first band. In paragraph 16,
The first band is a pellicle film having a wavelength of about 350 nm to 380 nm. In paragraph 16,
A pellicle membrane in which the transmittance dispersion is 2.7% or less of the total transmittance. In claim 12,
An anti-reflection film is located above the second film or below the first film,
The antireflection film is a pellicle film containing fluorine (F). In claim 12,
A pellicle membrane in which a separation membrane is positioned between the first membrane or the second membrane.

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