KR101680937B1 - Pellicle for EUV Lithography and method of fabricating the same - Google Patents

Abstract

A pellicle for EUV lithography and a method of manufacturing the same are provided. The pellicle for EUV lithography is a porous thin film made of a material having a plurality of holes and an extinction coefficient of 0.02 or less, and the hole has a diameter of 1 占 퐉 or less. Therefore, by using the porous thin film having a plurality of holes per se as a pellicle, it is possible to make the thickness thicker while having a higher EUV transmittance than that of the thin pellicle type pellicle.

Description

TECHNICAL FIELD The present invention relates to a pellicle for EUV lithography and a method for fabricating the same,

The present invention relates to a pellicle for EUV lithography, and more particularly to a pellicle for EUV lithography with improved EUV transmissivity and strength and a method of manufacturing the same.

Extreme ultraviolet (EUV) lithography is a technique of patterning using a very short 13.5 nm wavelength light source compared to conventional photolithography using an ArF light source with a wavelength of 193 nm.

This is regarded as a key process technology for manufacturing a semiconductor device having a pattern line width of 22 nm or less.

Since the EUV light source is strongly absorbed by all the substances present in nature, the design of the type and structure of equipment required for the process is different from that of conventional photolithography.

Due to the high absorptivity of EUV, no transmissive optics are used in lithography equipment, and all EUV optics are made up of reflective optics.

On the other hand, if unintentional particles adhere to the mask surface during the EUV exposure process due to the lithography mask, the particles cause defects in the pattern formation during the lithography process.

The pellicle protects the mask pattern to prevent particles from adhering to the surface. However, because light from the EUV wavelength is absorbed by all materials, the pellicle absorbs the light source, and the mask to be protected uses the reflective type, so a return light path occurs and two absorption occurs per pellicle layer. Thus, the presence of such a pellicle causes loss of the light source.

This can significantly reduce the throughput of the semiconductor EUV lithography exposure tool.

Thus, the pellicle for EUV lithography is fabricated as a transmissive thin film and mounted above the mask to protect the mask.

It is a pellicle made of silicon monolayer, which is the most advanced research into pellicle for EUV lithography. The pellicle made of such a single-layer silicon film has a low mechanical strength and a thin film having a thickness of 100 nm or less. Therefore, it is possible to secure a sufficient EUV transmittance. However, since the strength is very weak, many.

Therefore, in order to compensate for the low strength of the single silicon thin film, a pellicle structure in which a supporting structure is paved with honeycomb or the like is being studied. In this case, problems such as sagging or tearing of the pellicle membrane can be partially improved, There arises a problem that the intensity distribution of the EUV light becomes uneven after penetrating the pellicle because of the shape of the branch and the thick thickness.

Furthermore, there has been a problem that it is very difficult to fabricate a fine supporting structure so as to eliminate the phenomenon that the intensity distribution of EUV light becomes uneven.

Therefore, there is a need for research on pellicles for EUV lithography that can satisfy both EUV transmittance and strength.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pellicle for EUV lithography with improved EUV transmittance and strength and a method for manufacturing the same.

According to an aspect of the present invention, there is provided a pellicle for EUV lithography. The pellicle for EUV lithography is a porous pellicle thin film composed of a material having a plurality of holes and an extinction coefficient of 0.02 or less, and the hole has a diameter of 1 占 퐉 or less.

The porous pellicle thin film may include Zr, Mo, Y, Si, Rb, Sr, Nb, or Ru.

On the other hand, it may further include a cap layer disposed on the porous pellicle thin film and composed of a material having an extinction coefficient of 0.02 or less.

According to another aspect of the present invention, there is provided a method of manufacturing a pellicle for EUV lithography. A method of manufacturing a pellicle for EUV lithography includes the steps of preparing a porous structure having a nano-sized hole, injecting a template material into holes of the porous structure to form a template including the opposite shape of the porous structure, Forming a porous pellicle film including the shape of the porous structure by coating a material for pellicle on the template, and removing the template.

In addition, the porous structure includes anodized aluminum.

In addition, the template material may include PDMS or PMMA.

In addition, the step of injecting the template material into the hole of the porous structure may include filling the template material with the template material, and then maintaining the vacuum state for a predetermined period of time, thereby increasing the filling rate of filling the hole of the porous structure with the template material. do.

The pellicle material may include Zr, Mo, Y, Si, Rb, Sr, Nb, or Ru.

According to the present invention, since the porous thin film having a plurality of holes is used as a pellicle, the thickness can be increased while having a higher EUV transmittance than a pellicle of a single thin film type having no hole, thereby ensuring an improved strength.

In addition, the method for manufacturing a pellicle for EUV lithography according to the present invention uses a porous structure replication method, and it is possible to manufacture a pellicle of various materials by changing a material for a pellicle to be deposited on a template. In addition, such pellicle materials can be selected for the purpose of controlling the permeability and the structural strength.

Further, in such a pellicle, the diameter of the hole and the thickness of the thin film can be adjusted through the growth method of the porous structure, for example, the AAO growth method, and various pellets of various materials and sizes can be manufactured. Therefore, it is easy to control the mechanical strength and light transmittance of the pellicle.

In addition, since the porous pellicle film can be continuously copied by a simple process using only the porous structure, for example, the AAO structure, it is possible to replace the conventional method of forming the support layer, which must be made by the cumbersome patterning technique and the etching technique.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a plan view of a pellicle for EUV lithography according to an embodiment of the invention.
2 is a view showing an example of using a pellicle for EUV lithography according to an embodiment of the present invention.
FIGS. 3 to 7 are perspective views illustrating a method of manufacturing a pellicle for EUV lithography according to an embodiment of the present invention, in accordance with a process step.
Figure 8 is a schematic diagram according to the diameter and hole pitch ratio of a hole of a pellicle for EUV lithography according to an embodiment of the present invention.
9 is a graph showing the transmittance according to the thickness of the Si single thin film and the Si porous thin film.
10 is a graph showing the transmittance according to the thickness of the Zr single thin film and the Zr porous thin film.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers and / or regions, such elements, components, regions, layers and / And should not be limited by these terms.

On the other hand, "for EUV lithography" means that it is used in a lithography process using a EUV wavelength (λ = 13.5 nm) or a light source shorter than the EUV wavelength.

1 is a plan view of a pellicle for EUV lithography according to an embodiment of the invention.

Referring to FIG. 1, a pellicle for EUV lithography according to an exemplary embodiment of the present invention is a porous pellicle film 300 including a plurality of holes 310 and made of a material having an extinction coefficient of 0.02 or less.

That is, the porous pellicle film 300 for EUV lithography preferably includes a substance having a high EUV transmittance, that is, an extinction coefficient of more than 0 and 0.02 or less.

For example, a pellicle for an EUV lithography mask is basically a mask protecting film for preventing contamination of the mask. Furthermore, for use as a protective film for an EUV lithography mask, it is preferable to select a substance having a high EUV transmittance.

This EUV transmissivity is related to the extinction coefficient of the optical constants of the material.

<Formula 1>

n = 1 -? + i?

In the optical constant complex refractive index equation in the EUV / soft x-ray region expressed by Equation (1), a real number δ of the refractive index (n) is referred to as refraction index or refractive index, and the imaginary portion?

Therefore, a substance preferentially selected as a candidate for a pellicle for EUV lithography is preferably a substance having a low extinction coefficient and a low absorption of EUV.

For example, a material having an extinction coefficient of 0.02 or less may include Zr, Mo, Y, Si, Rb, Sr, Nb, or Ru. For example, silicon (Si) has an extinction coefficient of 0.001826, a low extinction coefficient and a low absorption of EUV, and is suitable as a pellicle material for EUV lithography.

On the other hand, even if the extinction coefficient of such a pellicle material is low, since the EUV transmittance is lowered as the thickness of the pellicle increases, there is a certain limit to increase the thickness and improve the strength.

Accordingly, the porous thin film including a plurality of holes 310 is used as a pellicle. In other words, since the EUV light can pass directly through the holes 310 of the porous pellicle film 300, the amount absorbed by the porous thin film can be reduced, and even if the thickness is further increased, the desired EUV transmissivity can be satisfied .

Accordingly, the porous pellicle film 300 including the plurality of holes 310 can have a higher thickness and a higher EUV transmittance than a pellicle of a single thin film type without a hole, thereby ensuring an improved strength.

At this time, the diameter of the hole 310 is 1 占 퐉 or less. If the diameter of the hole 310 exceeds 1 占 퐉, the problem of unevenness of the intensity distribution of the EUV light after pellicle transmission may occur.

Therefore, by setting the diameter of the hole 310 to a nano-size of 1 m or less, it is possible to prevent unevenness in the intensity distribution of the EUV light even after the pellicle is transmitted.

The ratio of the diameter of the hole 310 to the pitch of the hole 310 is preferably 5:10 to 9:10.

If the ratio of the diameter of the hole 310 to the pitch of the hole 310 is less than 5:10, that is, if the diameter of the hole 310 is less than 1/2 of the pitch of the hole 310, The increase in the EUV transmissivity of the porous pellicle film 300 is not as high as that of the single thin film having no hole, because the area ratio of the holes 310 is small. Therefore, there is a limit to increase the porosity thickness to improve the strength.

On the other hand, it may further include a cap layer (not shown) formed on the porous pellicle film 300 and composed of a substance having an extinction coefficient of more than 0 and 0.02 or less.

For example, such a cap layer (not shown) may include Zr, Mo, Y, Si, Rb, Sr, Nb or Ru.

2 is a view showing an example of using a pellicle for EUV lithography according to an embodiment of the present invention.

Referring to FIG. 2, a porous pellicle thin film according to an embodiment of the present invention is used as a protective film of an EUV mask. In this case, the porous pellicle thin film is placed on the EUV mask through the pellicle mounting frame.

Therefore, the EUV light is reflected by the EUV mask through the porous pellicle thin film, and then passes through the porous pellicle thin film. The loss of the light source can be minimized by the high transmittance of the porous pellicle thin film.

In addition, since the thickness of the porous pellicle film is increased to have an improved strength, there is no disadvantage that the strength of the EUV light after the penetration of the pellicle becomes uneven due to the addition of the conventional support structure, since a separate support structure for reinforcing the strength is not needed.

FIGS. 3 to 7 are perspective views illustrating a method of manufacturing a pellicle for EUV lithography according to an embodiment of the present invention, according to a process step. FIG.

Referring to FIG. 3, a porous structure 100 having nano-sized holes 110 is prepared.

For example, such a porous structure 100 may comprise anodic aluminum oxide (AAO).

Referring to FIG. 4, a template material is injected into the holes 110 of the porous structure 100. Thus, the injected template material may be cured to form the template 200 comprising the opposite form of the porous structure 110. That is, the template 200 including a plurality of protrusions (210 in FIG. 5) can be formed.

The template material may be PDMS or PMMA.

In addition, various injection methods such as a solution injection method can be used as a method of injecting the template material. For example, the PMMA template 200 may be formed by injecting a PMMA solution into the AAO porous structure 100, adsorbing the same, and then curing it.

The template material may be adsorbed to the hole 110 of the porous structure 100 as well as to cover the upper portion of the porous structure 100 and then cured.

The step of injecting the template material into the holes 110 of the porous structure 100 may further include a step of injecting the template material and maintaining a vacuum state for a predetermined period of time.

Therefore, by maintaining the vacuum state for a certain period of time after the injection of the template material, the template material can fill the hole of the porous structure better by the capillary phenomenon. That is, the filling rate for filling the holes of the porous structure with the template material can be increased through the vacuum state holding step.

Therefore, by increasing the filling rate in this manner, there is an advantage that a porous structure can be more precisely formed.

Referring to FIG. 5, the porous structure 100 is removed.

Therefore, when the porous structure 100 is removed, the plurality of protrusions 210, which are opposite to the porous structure 100, are removed. Only the template 200 including the template 200 remains.

At this time, the porous structure 100 can be removed by various methods such as wet etching, using a mold release agent in an applied mold, or separating using a Teflon coating, which can selectively remove only the porous structure 100. For example, the AAO porous structure can be removed by a wet etching process.

Referring to FIG. 6, a pellicle material is coated on the template 200 to form a porous pellicle membrane structure 300 including the porous structure 100.

For example, a porous pellicle membrane structure 300 having a plurality of holes (310 of FIG. 7) filled therein may be formed by coating a pellicle material on a template 200 on which a plurality of protrusions 210 are disposed.

The material for the pellicle may include Zr, Mo, Y, Si, Rb, Sr, Nb or Ru.

The pellicle material may be deposited on the template 200 using various thin film deposition methods such as atomic layer deposition (ALD), sputtering, chemical vapor deposition (CVD), ion beam deposition (IBD), or electroplating Can be coated.

For example, the porous pellicle film 300 including a plurality of holes 310, which are the same as the AAO structure, can be formed by using the AAO porous structure including a plurality of holes by using two replication methods.

Meanwhile, the shape of the finally formed porous pellicle thin film (300 in FIG. 7) can be adjusted by adjusting the diameter of the hole 110 of the porous structure 100 or the thickness of the thin film in advance. For example, AAO porous structure can control hole diameter or thin film thickness through AAO growth method.

Referring to FIG. 7, the template 200 is removed.

A variety of removal methods such as a wet etching method capable of selectively removing only these templates can be used. For example, the PMMA template can be removed by wet etching.

Therefore, only the porous pellicle film 300 including the plurality of holes 310 is finally left.

Measurement of transmittance of single thin film and porous thin film

Figure 8 is a schematic diagram according to the diameter and hole pitch ratio of a hole of a pellicle for EUV lithography according to an embodiment of the present invention.

8 (a) shows a case where the hole diameter and the hole pitch ratio of the pellicle are 5:10, FIG. 8 (b) shows the case where the hole diameter and the hole pitch ratio of the pellicle are 8:10, And the hole diameter and hole pitch ratio of the pellicle are 9:10.

The transmittance of Si single thin film without holes and the thickness of Si porous thin films having hole diameter and hole pitch ratio of pellicle holes as shown in Fig. 8 were measured.

9 is a graph showing the transmittance according to the thickness of the Si single thin film and the Si porous thin film.

In addition, the transmittance according to the thickness of the Zr porous thin film having the hole diameter and hole pitch ratio of the hole of the pellicle as shown in Fig. 8 and the Zr single thin film without holes was measured.

10 is a graph showing the transmittance according to the thickness of the Zr single thin film and the Zr porous thin film.

The EUV transmittance results according to Figs. 9 and 10 are shown in the following Tables 1 to 4.

Table 1 below shows the EUV transmissivity according to the thickness of a single thin film without holes.

Thin film thickness 50 nm 100 nm 150 nm 200 nm Si 91.9 84.4 77.5 71.2 Zr 84.0 70.5 59.2 49.7

Table 2 below shows the EUV transmissivity according to the thickness of the thin film when the hole diameter and the hole pitch ratio are 5:10.

Thin film thickness 50 nm 100 nm 150 nm 200 nm Si 93.5 87.4 81.9 76.8 Zr 87.1 76.3 67.2 59.6

Table 3 below is a table showing the EUV transmissivity according to the thickness of the thin film when the hole diameter and the hole pitch ratio are 8:10.

Thin film thickness 50 nm 100 nm 150 nm 200 nm Si 95.9 92.2 88.8 85.7 Zr 92.0 85.3 79.7 75.0

Table 4 below shows the EUV transmissivity according to the thickness of the thin film when the hole diameter and the hole pitch ratio are 9:10.

Thin film thickness 50 nm 100 nm 150 nm 200 nm Si 97 94.3 91.8 89.5 Zr 94.2 89.3 85.1 81.7

Referring to FIGS. 9, 10 and Tables 1 to 4, it can be seen that the hole diameter and the hole pitch ratio are similar to the transmittance of a single thin film of 50 nm thickness at a thickness of 200 nm for a 9:10 porous thin film.

Therefore, when the pellicle is made into a porous thin film, the same transmittance can be made thicker than a single thin film, thereby increasing the strength of the pellicle.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

100: Porous structure 110: Hole
200: template 210: projection
300: porous pellicle thin film 310: hole

Claims (8)

delete delete delete Preparing a porous structure having a nano-sized hole formed therein;
Forming a template including a plurality of protrusions having a nano-sized diameter and pitch including an opposite shape of the porous structure by injecting a template material into holes of the porous structure;
Removing the porous structure;
Coating a material for pellicle on the template to form a porous pellicle membrane structure including the shape of the porous structure; And
Removing the template from the porous pellicle membrane structure to form a porous pellicle membrane,
The porous pellicle thin film may be formed,
Wherein the thickness is from 150 nm to 200 nm, the ratio of the diameter of the holes to the pitch is from 8:10 to 9:10, and the EUV transmittance is not less than 75% and not more than 100%. 5. The method of claim 4,
Wherein the porous structure comprises anodized aluminum. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; 5. The method of claim 4,
Wherein the template material is PDMS or PMMA. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; 5. The method of claim 4,
Wherein the step of injecting the template material into the hole of the porous structure comprises:
Wherein the template material is injected and maintained in a vacuum state for a predetermined period of time to increase the filling rate of filling the holes of the porous structure with the template material. 5. The method of claim 4,
Wherein the material for pellicle comprises Zr, Mo, Y, Si, Rb, Sr, Nb or Ru.

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