KR20080006210A - Photoresist composition and method for forming a pattern using the same - Google Patents

Abstract

A photoresist composition and a patterning method are provided to keep high-resolution characteristics of a photoresist pattern and to form a finer pattern exactly at the same time. A photoresist composition includes 87.5-97.5wt% of a mixed solvent, a photosensitive resin, and a photoacid generator. The mixed solvent is obtained by mixing a propylene glycol monomethyl ether solvent with an ester solvent having higher polarity than the propylene glycol monomethyl ether. A method for forming a photoresist pattern includes the steps of: (S102) coating a semiconductor substrate with the photoresist composition to form a photoresist layer; (S104) performing selective exposure of the photoresist layer using a light source; (S106) developing the exposed photoresist layer to form a photoresist pattern; and (S110) to reduce a width of the photoresist pattern, subjecting a photoresist pattern-formed object to a reflow process.

Description

Photoresist composition and method for forming a pattern using the same

1 is a process flowchart illustrating a method of forming a photoresist pattern using a photoresist composition according to an embodiment of the present invention.

FIG. 2 is a graph illustrating a result after a reflow process is performed on photoresist contact hole patterns formed using photoresist compositions prepared according to Examples and Comparative Examples. FIG.

3 is an electron micrograph of a photoresist pattern obtained using a conventional photoresist composition.

4 is an electron micrograph of a photoresist pattern obtained using the photoresist composition of the example.

The present invention relates to a photoresist composition and a pattern forming method using the same, and more particularly, a photoresist composition constituting a photoresist for forming a photoresist film on a semiconductor substrate and a photoresist film formed by exposing and developing the photoresist film. A method of forming a photoresist pattern.

In a rapidly developing information society, a high-integration device having a high data transfer rate is required to process a large amount of information faster. In order to manufacture highly integrated semiconductor devices, design rules of semiconductor devices are rapidly decreasing. Accordingly, semiconductor devices require fine patterns beyond the limit resolution of equipment and photoresists.

In order to form the fine pattern as described above, the characteristics of the photoresist that can flow at a high temperature are used. That is, after forming a photoresist pattern for forming a fine pattern, if heat is applied above the glass transition temperature (Tg) of the polymer in the photoresist, the photoresist constituting the photoresist pattern expands and flows laterally While expanding to the area exposed by the photoresist pattern, the diameter and pattern spacing of the contact hole is reduced.

Such a process is called a reflow process of the photoresist, and may expose a narrower area than the smallest possible size area that can be stably formed by photolithography by the reflow process. Therefore, the process may be performed according to the critical dimension (cd) to be formed.

At this time, the heating temperature determines the line width during the reflow process. That is, the line width becomes narrower or wider than the preset line width by the heating temperature being higher or lower than the set temperature. A suitable temperature for the reflow process is a temperature between the glass transition temperature of the polymer in the photoresist and the temperature at which the polymer degrades (Td).

However, ArF photoresist compositions currently used in ArF lithography have glass transition temperatures too high for the reflow process to proceed. In particular, the photosensitive resin included in the ArF photoresist composition causes a problem of causing decomposition at the reflow process temperature when the reflow process is performed.

The first object of the present invention for solving the above problems is to provide a photoresist composition suitable for application to the reflow process.

A second object of the present invention for solving the above problems is to provide a method of forming a fine photoresist pattern by applying the photoresist composition.

The photoresist composition for achieving the first object of the present invention is obtained by mixing a propylene glycol monomethyl ether solvent and an ester solvent having a higher polarity than the propylene glycol monomethyl ether solvent. Mixed solvents 87.5 to 97.5% by weight, photosensitive resin and photoacid generator. The mixed solvent is obtained by mixing the propylene glycol monomethyl ether solvent and the ester solvent in a weight ratio of 6-7: 3-4, and the viscosity of the mixed solvent is 2.01-2.60cp.

The ester solvent is ethyl lactate and 2-hydroxyisobutyrate methyl ester, and the ethyl lactate and 2-hydroxyisobutyric acid methyl ester are contained in a weight ratio of 1 to 2: 2. Obtained by mixing.

In addition, it is obtained by mixing 87.5 to 97.5% by weight of the mixed solvent, 2.0 to 12.0% by weight of the photosensitive resin and 0.1 to 0.5% by weight of the photoacid generator.

The pattern forming method for achieving the second object of the present invention, 87.5 to 97.5% by weight of a mixed solvent obtained by mixing a propylene glycol monomethyl ether solvent and an ester solvent having a polarity higher than the propylene glycol monomethyl ether solvent, photosensitive A photoresist composition comprising a resin and a photoacid generator is applied onto a semiconductor substrate to form a photoresist film, the photoresist film is selectively exposed using a light source, and the exposed photoresist film is developed to form a photoresist pattern. Thereafter, performing a reflow process on the object on which the photoresist pattern is formed to reduce the width of the photoresist pattern.

At this time, the reflow process is performed at a temperature of 150 to 180 ℃, the light source is a light source having a wavelength of 193nm.

The photoresist composition according to the present invention as described above, using a conventional photosensitive resin having a high resolution and a solvent having a high viscosity to increase the amount of the solvent remaining in the pattern. Thus, it maintains high resolution characteristics and enables a reflow process even at low temperatures. Finally, by forming a pattern having a fine line width while maintaining high-resolution characteristics on the semiconductor substrate, it is possible to effectively produce highly reliable semiconductor devices.

EMBODIMENT OF THE INVENTION Hereinafter, the photoresist composition of this invention and the formation method of the pattern using the photoresist composition are explained in full detail by an Example. However, the present invention is not limited to the following embodiments and may be implemented in other forms. The embodiments introduced herein are provided to make the disclosure more complete and to fully convey the spirit and features of the invention to those skilled in the art. In the drawings, the thickness of each device or film (layer) and regions has been exaggerated for clarity of the invention, and each device may have a variety of additional devices not described herein. If (layer) is mentioned as being located on another film (layer) or substrate, it may be formed directly on another film (layer) or substrate, or an additional film (layer) may be interposed therebetween.

Photoresist  Composition

The photoresist composition according to the present invention is 87.5 to 97.5 wt% of a mixed solvent obtained by mixing a propylene glycol monomethyl ether solvent and an ester solvent having a higher polarity than the propylene glycol monomethyl ether solvent, Photosensitive resins and photoacid generators.

The mixed solvent is prepared by mixing a polar solvent with a relatively higher polar polar solvent and serves as an important parameter in determining the viscosity of the photoresist composition. The photosensitive resin is also referred to as a polymer as the substance of the photoresist pattern remaining after development. The photosensitive resin also has a property of dissolving in a mixed solvent. Finally, photoacid generators are substances that decompose by light to generate acids.

The propylene glycol monomethyl ether solvent and the ether solvent each have inherent viscosity characteristics depending on the kind. Therefore, while the propylene glycol monomethyl ether solvent and the ether solvent satisfy the above-mentioned weight% ratio, it is preferable to mix in the ratio which can make the viscosity of the mixed solvent about 2.01-2.60cp. If the viscosity of the mixed solvent exceeds the above range, the applicability of the photoresist composition is lowered, which is not preferable.

If the viscosity of the mixed solvent is less than the above range, the evaporation rate of the photoresist composition increases, which is not preferable.

Therefore, the mixed solvent is preferably prepared by mixing the propylene glycol monomethyl ether solvent and the ester solvent in a weight ratio of 6-7: 3-4.

Specific examples of the ester compound that can be used in the present invention include ethyl lactate and 2-hydroxyisobutyric acid methyl ester (methyl 2-hydroxyisobutyrate). These can be used individually or in mixture.

In addition, it is preferable to prepare the ethyl lactate and 2-hydroxyisobutyric acid methyl ester by mixing in a 1-2 weight ratio.

When the ratio of the propylene glycol monomethyl ether solvent and the ester solvent in the mixed solvent of the photoresist composition is less than 87.5 wt%, and the ratio of the ester solvent exceeds 22.5 wt%, the solubility of the mixed solvent increases rapidly. When the solubility of the mixed solvent is rapidly increased, the viscosity of the photoresist composition increases and is not formed in a later pattern, which is not preferable. And when the ratio of the propylene glycol monomethyl ether solvent exceeds 97.5 wt% and the ratio of the ester solvent is less than 2.5 wt%, the solubility of the mixed solvent is drastically reduced. Therefore, the mixed solvent is preferably used in the ratio of 87.5 to 97.5% by weight based on the photoresist composition.

As described above, the photoresist composition including the mixed solvent obtained by mixing according to the weight ratio or the weight part includes a resin and a photoacid generator. In this case, the photoresist composition is preferably prepared by mixing about 87.5 to 97.5% by weight of the mixed solvent, 2.0 to 12.0% by weight of the photosensitive resin, and 0.1 to 0.5% by weight of the photoacid generator.

Representative examples of the photosensitive resin include acrylate (acrylate), coma (cyclo-clefin methacrylate), co-based (cyclo-olefin) and the like. More preferably, the resin may include methacrylate, vinyl ether methacrylate, and coma-based cyclo-olefin methacrylate. These can be used individually or in mixture.

Representative examples of the photoacid generator include monophenylsulfonium salts, triphenylsulfonium salts, and the like. These can be used individually or in mixture.

The photoresist composition according to the embodiment of the present invention may further include an organic base. The organic base serves to control the shape of the pattern while minimizing the influence of basic compounds such as amines contained in the atmosphere on the pattern obtained after exposure.

The photosensitive resin, photoacid generator, and quencher used in the photoresist according to the present invention do not abnormally react with the mixed solvent, have sufficient dissolving power and a suitable drying rate, and have the ability to form a uniform and smooth coating film after the mixed solvent evaporates You can use anything with.

As mentioned above, the photoresist composition comprises a photosensitive, photoacid generator, quencher and mixed solvent. In this case, about 87.5-97.5 weight% of mixed solvents make up 100 weight% of photoresist compositions. Therefore, the physical properties of the photoresist composition are almost the same as those of the mixed solvent. In addition, it is substantially difficult to specify the physical properties of the photoresist composition because of the wide variety of resins, photoacid generators and quenchers dissolved in the mixed solvent. However, those skilled in the art will be able to easily implement the photoresist composition according to the present invention from a mixed solvent satisfying the above-described mixed weight ratio and physical properties.

Pattern Formation Method

1 is a process flowchart showing a method of forming a photoresist pattern using a photoresist composition according to an embodiment of the present invention.

Referring to Figure 1, first to form a photoresist composition comprising a propylene glycol monomethyl ether solvent and ester solvent (step S100).

Specifically, to form a photoresist composition comprising 87.5 to 97.5% by weight of a mixed solvent obtained by mixing a propylene glycol monomethyl ether solvent and an ester solvent having a higher polarity than the propylene glycol monomethyl ether solvent, a photosensitive resin and a photoacid generator do.

The mixed solvent is obtained by mixing a propylene glycol monomethyl ether solvent and an ester solvent. Specific examples of the ester compound include ethyl lactate and 2-hydroxyisobutyric acid methyl ester. These can be used individually or in mixture.

The mixed solvent is prepared by mixing a polar solvent with a relatively higher polar polar solvent and serves as an important parameter in determining the viscosity of the photoresist composition. While the propylene glycol monomethyl ether solvent and the ester solvent satisfy the above-described weight ratio, it is preferable to mix in a ratio that can make the viscosity of the mixed solvent at about 2.01 to 2.60 cps.

Subsequently, the photoresist composition is applied onto a semiconductor substrate to form a photoresist film. (Step S102)

The photoresist film may be formed by rotating the rotary chuck supporting the substrate at high speed and uniformly applying the photoresist composition onto the substrate while the substrate is rotated. In addition, an anti-reflective layer may be formed on the substrate.

 After applying the photoresist composition on the semiconductor substrate as described above, it is preferable to soft bake the semiconductor substrate at a temperature of about 110 to 120 ℃ to increase the adhesion of the photoresist film.

 The photoresist film is selectively exposed by using a light source. (Step S104) A reticle having a predetermined image pattern formed on the photoresist film for selectively exposing only a predetermined portion of the photoresist film is disposed thereon, and then light is applied to the photoresist film. Project the. In this case, a light source having a wavelength of less than 248 nm is used. More preferably, an ArF light source having a wavelength of 193 nm is used. However, if necessary, other light sources having appropriate wavelengths can be used for exposure. Post-baking the semiconductor substrate at a temperature of about 100 to 110 ° C. may be further performed to increase the adhesion of the exposed photoresist film.

The exposed photoresist film is developed to form a first photoresist contact hole pattern. (Steps S106, S108)

Specifically, the exposed photoresist film is developed to form a photoresist contact hole pattern by etching the exposed portion, which is a portion having high solubility, and leaving a portion having a low solubility. At this time, a developer such as tetra-methyl ammonium hydroxide (TMAH) may be used.

Subsequently, the first photoresist contact hole pattern is formed through a conventional process such as cleaning.

 A second photoresist contact hole pattern is formed by performing a reflow process on the object on which the first photoresist contact hole pattern is formed. (Steps S110, 112)

The reflow process may be performed by heating the semiconductor substrate on which the first photoresist pattern is formed to a temperature of 150 to 180 ° C. In one embodiment of the invention the reflow process is carried out at a temperature of 150 to 155 ℃.

 During the reflow process, the photoresist constituting the first contact hole pattern expands and flows laterally, and has a width smaller than that of the first photoresist contact hole pattern. Form in a pattern.

The width of the second photoresist contact hole pattern is a portion exposing the object.

Thereafter, a predetermined process may be performed on the semiconductor substrate on which the second photoresist pattern is formed to form semiconductor patterns necessary for various wirings and electrodes.

Hereinafter, the present invention has been described with reference to specific embodiments of the present invention, but the present invention is not limited to the following embodiments by those skilled in the art.

Example  One

In this example, propylene glycol monomethyl ether solvent, ethyl lactate and 2-hydroxyisobutyric acid methylester solvent were mixed at a weight ratio of about 6: 2: 2 to obtain 94.15 g of a mixed solvent. The viscosity of the obtained mixed solvent was 2.60 cps. The solution obtained by dissolving 2.7 g of methacrylate resin and 0.3 g of PAG in the obtained mixed solvent 94.15 was filtered through a 0.2 μm membrane filter to obtain a photoresist composition.

Comparative Example 1

Propylene glycol monomethyl ether solvent and 2-hydroxyisobutyric acid methylester solvent were mixed in a 9: 1 weight ratio to obtain 94.15 g of mixed solvent. The viscosity of the obtained mixed solvent was 1.85 cps. The solution obtained by dissolving 2.7 g of methacrylate resin and 0.3 g of PAG in the obtained mixed solvent 94.15 was filtered through a 0.2 μm membrane filter to obtain a photoresist composition.

Comparative Example 2

Propylene glycol monomethyl ether solvent, ethyl lactate and 2-hydroxyisobutyric acid methylester solvent were mixed at a weight ratio of about 7: 1: 2 to give 94.15 g of mixed solvent. The viscosity of the obtained mixed solvent was 2.01 cps. The solution obtained by dissolving 2.7 g of methacrylate resin and 0.3 g of PAG in the obtained mixed solvent 94.15 was filtered through a 0.2 μm membrane filter to obtain a photoresist composition.

Comparative Example 3

Propylene glycol monomethyl ether solvent and 2-hydroxyisobutyric acid methylester solvent were mixed in a 3: 7 weight ratio to obtain 94.15 g of mixed solvent. The viscosity of the obtained mixed solvent was 2.50 cps. The solution obtained by dissolving 2.7 g of methacrylate resin and 0.3 g of PAG in the obtained mixed solvent 94.15 was filtered through a 0.2 μm membrane filter to obtain a photoresist composition.

Photoresist patterns were formed using the photoresist compositions prepared in the above Examples and Comparative Examples. Subsequently, the photoresist pattern was evaluated after performing a reflow process on the photoresist patterns. The result is shown in FIG.

Specifically, the photoresist composition obtained in Examples and Comparative Examples was sprayed onto the semiconductor substrate while rotating the semiconductor substrate on which the antireflection film was formed at an rpm speed of about 900 to 4000. Next, the semiconductor substrate was soft baked on a hot plate at a temperature of about 115 ° C. to form a photoresist film having a thickness of about 800 GPa. Subsequently, ArF light having an image of a reticle was projected onto the photoresist film and exposed. The exposed photoresist film was developed to form a photoresist contact hole pattern.

Finally, the semiconductor substrate having the photoresist contact hole pattern formed thereon was subjected to a reflow process at a temperature of 150 ° C. to 155 ° C. to obtain a result as shown in FIG. 2.

Referring to FIG. 2, as a result of performing the reflow process at the same temperature, it can be seen that the photoresist contact hole pattern according to the embodiment is significantly reduced in line width compared to the photoresist contact hole pattern according to the comparative examples. .

This is because a relatively large amount of solvent remains in the photoresist contact hole pattern formed using the photoresist composition according to the embodiment, compared with Comparative Examples 1 to 3, and the degree of expansion thereof is also large.

Thus, the line width of the photoresist contact hole pattern according to the embodiment is relatively more reduced, and as a result, the photoresist composition according to the embodiment enables a reflow process even at a low temperature.

3 is an electron micrograph of a photoresist pattern obtained using a conventional photoresist composition, and FIG. 4 is an electron micrograph of a photoresist pattern obtained using a photoresist composition of an example.

3 and 4, the pattern formed using the photoresist composition obtained in the embodiment of the present invention was compared with the pattern formed using the photoresist composition having conventional high resolution characteristics. It can be seen that the pattern according to the embodiment of the present invention is similar to the conventional pattern.

Therefore, the photoresist pattern formed using the photoresist composition according to the embodiment of the present invention can be formed in a finer pattern while maintaining the properties of high resolution.

As described above, a photoresist pattern is used using the photoresist composition according to the preferred embodiment of the present invention. This increases the amount of solvent remaining in the pattern, thereby enabling a reflow process even at low temperatures. As a result, a finer pattern can be accurately formed while maintaining high resolution characteristics.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (9)

87.5 to 97.5% by weight of a mixed solvent obtained by mixing a propylene glycol monomethyl ether solvent and an ester solvent having a higher polarity than the propylene glycol monomethyl ether solvent, including a photosensitive resin and a photoacid generator Photoresist composition, characterized in that. The photoresist composition of claim 1, wherein the mixed solvent is obtained by mixing the propylene glycol monomethyl ether solvent and the ester solvent in a weight ratio of 6-7: 3-4. The photoresist composition of claim 1, wherein the mixed solvent has a viscosity of 2.01 to 2.60 cps. The photoresist composition of claim 1, wherein the ester solvent is ethyl lactate and 2-hydroxyisobutyric acid methyl ester. 5. The photoresist composition of claim 4, wherein the ethyl lactate and 2-hydroxyisobutyric acid methyl ester are obtained by mixing in a weight ratio of 1-2. The photoresist composition of claim 1, wherein the mixed solvent is obtained by mixing 87.5 to 97.5 wt% of the mixed solvent, 2.0 to 12.0 wt% of the photosensitive resin, and 0.1 to 0.5 wt% of the photoacid generator. A photoresist composition comprising 87.5 to 97.5% by weight of a mixed solvent obtained by mixing a propylene glycol monomethyl ether solvent and an ester solvent having a polarity higher than that of the propylene glycol monomethyl ether solvent, a photosensitive resin, and a photoacid generator is formed on a semiconductor substrate. Applying to form a photoresist film; Selectively exposing the photoresist film using a light source; Developing the exposed photoresist film to form a photoresist pattern; And And performing a reflow process on the object on which the photoresist pattern is formed to reduce the width of the photoresist pattern. The method of claim 7, wherein the reflow process is performed at a temperature of 150 to 180 ℃. 8. The method of claim 7, wherein the light source is a light source having a wavelength of 193 nm.

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