KR101316192B1 - Photoresist composition - Google Patents

Abstract

The present invention provides a photoresist composition comprising a novolak-based resin, a photosensitive agent, a low-absorbance resin having a light absorbency of at least one of wavelengths of 248nm, 193nm, and 157nm than that of the novolak-based resin. Resist composition has good light transmittance in short wavelength semiconductor process of 248nm (KrF) or less even when applied in non-chemically amplified type, and has various performances such as sensitivity, resolution, residual film rate, coating property, and especially profile and depth of focus. It is an excellent resist composition.

Photoresist, Novolak Resin, Short Wavelength

Description

Photoresist composition and pattern formation method thereof {PHOTORESIST COMPOSITION}

1 is a graph relating to absorbance of a conventional novolak-based photoresist composition,

2A and 2B are graphs of light transmittances of 248 nm and 193 nm of embodiments according to the present invention;

3A to 3D are SEM photographs of the pattern shapes of the photoresist compositions of Comparative Example 1 and Examples 1 to 3,

4 is a graph of the sensitivity of embodiments according to the present invention.

The present invention relates to a photoresist composition capable of forming a semiconductor fine pattern by short wavelength light of KrF (248 nm) or less, and a pattern forming method thereof.

In general, microfabrication in semiconductor fabrication is commonly performed in lithographic processes using resist compositions. In a lithography process, the resolution can be improved primarily by shortening the exposure wavelength, as indicated by Rayleigh's formula regarding the diffraction limit. Therefore, the wavelength of the light source for the lithography process used in semiconductor manufacturing is g-line (wavelength 436 nm), i-ray (wavelength 365 nm), KrF-excimer laser (wavelength 248 nm), ArF- excimer laser (wavelength 193 nm). Increasingly, wavelengths of shorter light sources have been adopted. In recent years, as the degree of integration of integrated circuits has increased, submicron pattern formation has been required. In particular, photolithography using a KrF-eximer laser or an ArF-eximer laser has attracted attention in that it enables the production of 64-M DRAM to 1G DRAM. On the other hand, photoresists are also used for color filters and the like, and fine patterns are required.

However, since a lens of an exposure apparatus using a short wavelength excimer laser has a shorter lifetime than a lens used for a conventional exposure light source, it is preferable to expose the lens to the excimer laser for a short time.

Conventionally, novolak-based resins have been the basis of photoresist compositions that can be exposed by g-ray (436 nm) and i-ray (365 nm) light, and these g-ray and i-ray photoresists are currently the mainstream KrF. In the semiconductor exposure (248 nm), it has been recognized that semiconductor fine pattern formation is difficult due to high absorbance, low sensitivity, etc., and is not currently used in short wavelength exposure below KrF.

On the other hand, so-called chemically amplified photoresist using a photoacid generator is used for short wavelength exposure below KrF. Chemically amplified resists are based on PHS polymers and photoacid generators and use reaction inhibitors to enhance contrast and control solubility. In the development of photoresist materials, the introduction of chemical amplification has been groundbreaking and attracting much attention in terms of its chemical principles and application to resists. Chemical amplification refers to a phenomenon in which active species generated by the action of one photon cause chemical reactions in series, resulting in a quantum yield amplification. In this chemical amplification, the active species generated by a single photochemical reaction act as a catalyst so that chemical reactions such as deprotection and crosslinking can occur continuously, so that the total quantum yield of these reactions is greater than that of the initial catalyst production. Is amplified.

When a chemically amplified resist is used, the acid generated from the photoacid generator in the irradiation section of the radiation is diffused by subsequent heat treatment, and the solubility in the alkaline developer of the irradiation section is changed by a reaction using the generated acid as a catalyst. Or a negative pattern is obtained. On the other hand, because the chemically amplified resist uses an acid catalysis, there is a problem in that the lower tailing of the profile appears due to the inactivation of the acid when the substrate is basic.

In addition, this problem may be solved by adding a much larger amount of the basic removing material, but there is a problem that the sensitivity is lowered when a large amount of the basic removing material is added. When an excimer laser is used as the exposure light source, a low reflection substrate is usually used, but in general, the resist profile deteriorates to a tapered shape, although the dimensional uniformity is efficiently improved. Therefore, chemically amplified resists have a problem that their performance, in particular their profile, varies with the type of substrate.

Chemically amplified positive type resists, particularly positive type resists for KrF excimer laser photolithography, are poly (hydroxystyrene) resins in which some of their phenolic hydroxyl groups are dissociated by the action of an acid. Protected resins are often used in combination with photoacid generators. As a group dissociated by the action of such an acid, forming an acetal bond between oxygen atoms derived from phenolic hydroxyl groups from the viewpoint of resolution and sensitivity, for example, tetrahydro-2-pyranyl Although resins having a structure in which tetrahydro-2-furyl or 1-ethoxyethyl are bonded to an oxygen atom have been noted, even when these resins are used, the film thickness is thick when used for the metal process and the implanter process. However, there is a problem in that the profile is limited because the pattern is formed under the specific condition of the substrate.

In addition, the HF etching process is usefully used in the semiconductor process, and the PHS-based chemically amplified photoresist has a problem in that the HF etching process cannot be used because of poor resistance.

Therefore, as a non-chemically amplified photoresist, development of a photoresist that can be excellently applied to a semiconductor process using a short wavelength of KrF or less is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems,

It can be applied as a non-chemically amplified type with excellent HF etching resistance, and has excellent light transmittance even in short wavelength semiconductor process below KrF, and has various performances such as sensitivity, resolution, residual film rate, coating property, and profile and depth of focus. It is an object to provide an excellent photoresist.

According to an aspect of the present invention,

Provided is a photoresist composition comprising a novolak-based resin, a photosensitive agent, and a low-absorbance resin having absorbance of at least one of wavelengths of 248 nm, 193 nm, and 157 nm than the novolak-based resin.

In addition, when the photoresist composition was diluted in methanol at a concentration of 4 × 10 ⁻⁵ % and the absorbance was measured by a UV-Vis spectrometer, the light transmittance at a wavelength of 248 nm was obtained in the photoresist composition. Except for providing a photoresist composition characterized in that increased by more than 10% compared to the light transmittance of 248nm wavelength when the absorbance is measured by UV-Vis spectroscopy under the same conditions.

In addition, the low light absorbing resin provides a photoresist composition, characterized in that the resin comprises at least one of the structural units of the following formula (1) and (2).

≪ Formula 1 >

(The above R1 is a linear, branched or cyclic alkyl or alkoxy, ester, ether, carbonyl, acetal, alcohol group having 1 to 15 carbon atoms, and R2 is hydrogen or an alkyl group having 1 to 5 carbon atoms.)

(2)

(The said R3 is a C1-C5 alkyl group.)

It also provides a photoresist composition, characterized in that the non-chemically amplified photoresist.

The present invention also includes the steps of applying the above-described photoresist composition; Exposing a portion of the photoresist composition with light having a wavelength range of 248 nm or less in dominant wavelength; And removing the exposed or non-exposed areas of the photoresist composition.

Hereinafter, the present invention will be described in more detail.

The resist composition according to the present invention is characterized in that the absorbance of at least one wavelength of the novolak-based resin, photosensitive agent, at least one of 248nm, 193nm, and 157nm comprises a low absorbing resin lower than the novolak-based resin.

When the photoresist composition including the novolac-based resin is used without the low light absorbing resin, as shown in FIG. 1, it can be seen that light transmittance drops exponentially at a short wavelength of 248 nm or less. Therefore, if the light transmittance can be improved, the novolak-based resin can be used as the base resin of the photoresist even at short wavelengths of 248 nm or less.

According to Lambert-Beer's law, the absorbance is proportional to the transmission length and the concentration of the absorbing species. Therefore, if the concentration of absorbing species can be reduced, the overall absorbance is lowered and the transmittance of the photoresist is increased.

The resist composition according to the present invention absorbs at least one wavelength of at least one of 248 nm, 193 nm, and 157 nm in the novolak-based resin so as to reduce the concentration of absorbing species and at the same time satisfy the properties of the resist. Characterized in that it comprises a low absorbing resin lower than the base resin as an essential component.

The novolak-based resin may be used without limitation, novolak-based resins generally used as the base resin of the photoresist in the art, all of which are included in the present invention. As an example of the manufacturing method of a novolak base resin, a phenolic compound and an aldehyde can be condensed in presence of an acidic catalyst. Examples of phenolic compounds include phenol, o-, m- or p-cresol, 2,3-, 2,5-, 3,4- or 3,5-xylenol, 2,3,5-trimethyl Phenol, 2-, 3- or 4-tert-butylphenol, 2-3-butyl-4- or 5-methylphenol, 2-, 4- or 5-methyl resorcinol, 2-, 3- or 4-methoxyphenol, 2,3-, 2,5- or 3,5-dimethoxyphenol, 2-methoxyresorcinol, 4-tert-butyl catechol, 2-, 3- or 4-ethyl Phenol, 2,5- or 3,5-diethylphenol, 2,3,5-triethylphenol, 2-naphthol, 1,3-, 1,5- or 1,7-dihydroxynaphthalene and xylene Polyhydroxytriphenyl methane type compounds obtained by condensing knol and hydroxybenzaldehyde. These phenolic compounds may be used alone or in combination of two or more.

Examples of aldehydes include aliphatic aldehydes such as formaldehyde, acetoaldehyde, propionaldehyde, n-butylaldehyde, isobutylaldehyde, pivalaldehyde, n-hexylaldehyde, acrolein- and crotonaldehyde; Alicyclic compounds such as cyclohexaldehyde, cyclopentanealdehyde, furfural and furyl acrolein; Benzaldehyde, o-, m- or p- methylbenzaldehyde, p-ethylbenzaldehyde, 2,4-, 2,5-, 3,4- or 3,5-dimethylbenzaldehyde, o-, m- or p-hydroxy Aromatic aldehydes such as benzaldehyde, o-, m- or p-anisaldehyde and vanillin; And aromatic aliphatic aldehydes such as phenyl acetaldehyde and cinnamic aldehyde. These aldehydes can also be used alone or in combination of two or more. Among these, formaldehyde is preferable because it can be easily obtained industrially.

Examples of acid catalysts usable for condensing phenolic compounds and aldehydes include inorganic acids such as hydrochloric acid, sulfuric acid, perchloric acid and phosphoric acid; Organic acids such as formic acid, acetic acid, oxalic acid, trichloroacetic acid and p-toluenesulfonic acid; Divalent metal salts such as zinc acetate, zinc chloride and manganese acetate. These acid catalysts may be used alone or in combination of two or more. The condensation reaction can be carried out in a conventional manner, for example for 2 to 30 hours at 60 to 120 ℃.

The low light absorbing resin is a resin having a low absorbance at least one wavelength of 248 nm, 193 nm, and 157 nm compared to the novolak-based resin, and any resin satisfying such characteristics is included in the present invention. Moreover, even if it adds to a resist composition, it is preferable to select the low light absorption resin which satisfy | fills the physical property calculated | required as a resist composition. In particular, the low light absorbing resin preferably has a main skeleton of a novolak resin, and preferably has a resist property, and a functional group or side branch having a relatively short wavelength transmission is preferably present.

For example, the low light absorbing resin is preferably a resin including at least one of the structural units represented by the following Chemical Formula 1 and the following Chemical Formula 2. The low light absorbing resin may be formed by copolymerizing other structural units in addition to Chemical Formula 1 and Chemical Formula 2 and included in the present invention.

≪ Formula 1 >

(The said R ¹ is a C1-C15 linear, branched or cyclic alkyl or alkoxy, ester, ether, carbonyl, acetal, alcohol group, and said R <^2> is hydrogen or a C1-C5 alkyl group. )

(2)

(R ³ is an alkyl group having 1 to 5 carbon atoms.)

One or two or more kinds of structural units corresponding to Chemical Formula 1 may be included, and one or two or more kinds of structural units corresponding to Chemical Formula 2 may be included.

The low light absorbing resin is not limited, but is preferably included 5 to 50 parts by weight with respect to 100 weight of the novolak-based resin. If the addition is too small, the effect of addition is insignificant, and if it is added too much, the reactivity of the novolac base resin and the photosensitive agent is reduced, resulting in poor pattern shape during development. The low light absorbing resin is not limited, but the molecular weight is preferably in the range of 5000 to 10000.

By adding such a low absorbing resin to the resist, the concentration of the novolak-based resin is reduced to improve the light transmittance of KrF (248 nm) or less, enabling the formation of a fine pattern even at short wavelengths and at the same time satisfying the physical properties required as a resist. It becomes possible. Moreover, it turns out that a sensitivity improves.

The photosensitive agent may be a photosensitive agent generally used in the resist field, and in particular, a quinone diazo-type radiation-sensitive agent may be used. As an example, diazo naphthoquinone is mentioned.

It is also possible to use o-quinone diazosulfonic acid esters of compounds with one or more phenolic hydroxyl groups. Preference is given to 1,2-naphthoquinonediazo-5- or 4-sulfonic acid esters or 1,2-benzoquinone diazo-4-sulfonic acid esters of polyhydroxy compounds having three or more phenolic hydroxyl groups. Such esters can be prepared by reacting a compound having a hydroxyl group described above with an o-quinone diazosulfonic acid halide in the presence of a base such as triethyl amine. Among the o-quinone diazosulfonic acid halides, 1,2-naphthoquinone diazo-5-sulfonic acid chloride is particularly preferred.

These quinone diazo type radiation-sensitizers may be used alone or in combination of one or two reagents.

The radiation-sensitive agent is not limited but is preferably present in an amount of 30 to 60 parts by weight based on 100 parts by weight of the novolak-based base resin.

The present invention can be applied to a non-chemically amplified photoresist that does not contain a photo-acid generator by adding the photosensitizer, it can be particularly useful to solve the disadvantages of chemically amplified photoresist. However, the addition of the photoacid generator is not excluded from the present invention.

The photoresist composition according to the present invention may further include components added to photoresist compositions known in the art, all of which are included in the present invention. In particular, it may include what is known as a component added to the novolak-based photoresist composition.

In one example, a solvent may be further included for ease of coating. The photoresist composition of the present invention is generally applied as a resist solution on a substrate such as a silicon wafer. That is, each of the above components is dissolved in a solvent to prepare a resist solution, and this solution is applied. Any solvent may be used as long as it dissolves each component, has a suitable drying rate, and provides a uniform and smooth coating. Solvents commonly used in the art may be used. Examples thereof include glycol ether esters such as ethyl cellosolve acetate, methyl cellosolve acetate, propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate; Glycol ethers such as ethyl cellosolve, methyl cellosolve, propylene glycol monomethyl ether and propylene glycol monoethyl ether; Esters such as ethyl lactate, butyl acetate, amyl acetate and ethyl pyruvate; Ketones such as 2-heptanone and cyclohexanone; And cyclic esters such as γ-butyrolactone. These solvents may be used alone or in combination of two or more.

When the photoresist composition according to the present invention includes the low light absorbing resin, the light transmittance at a wavelength of 248 nm is measured by using a UV-Vis spectrometer, except for the low light absorbing resin in the photoresist composition of claim 1. It is characterized by an increase of more than 10%. In addition, the addition of the low absorbing resin satisfies the physical properties required as the photoresist composition.

The present invention also provides a method of forming a pattern of a photoresist composition. The pattern forming method of the photoresist composition according to the present invention comprises the steps of applying the above-described photoresist composition, exposing a portion of the photoresist composition with light having a wavelength range of 248nm or less, and exposure of the photoresist composition And removing the area or the non-exposed area.

As an example, it apply | coats on a base material as follows, photocuring, and develops, and a pattern is formed.

First, the composition is applied onto a substrate (not limited, usually glass or silicon wafer) or a layer containing solid content of a resist composition formed first, and preliminarily dried to remove volatile components such as a solvent to obtain a smooth coating film. Although the thickness of the coating film at this time is not restrict | limited, Usually, about 1-3 micrometers is preferable. The substrate may be a silicon wafer deposited with TiN treated with hexamethyldisilazane. Further, the method of applying the photoresist onto the substrate is not limited, but can be simply applied using a spin coater. After application, it is preferable to perform a pre-heat treatment for 60 seconds on a hot plate at 100 ℃ after drying.

In order to obtain the desired pattern in the coating film obtained in this way, a specific area | region is selectively exposed by the light source whose exposure wavelength is 248 nm or less through a mask. At this time, it is preferable to use apparatuses, such as a mask aligner and a stepper, so that a parallel light beam may be irradiated uniformly to the whole exposure part, and a mask and a board | substrate will be correctly aligned.

Although not limited to the light source of 248nm or less, one or more of KrF (248nm), ArF (193nm), F2 (157nm), and EUV (65nm) may be selectively used. As an example, a scanning exposure machine ('NSR-S203B' manufactured by Nikon Corp., NA = 0.55, s = 0.75) of 248 nm (KrF) is used to expose the light with varying exposure doses to form lines and space patterns.

Then, it develops with alkaline developing solution. If necessary, the heat treatment on the hot plate may be performed at 100 ° C. for 60 seconds before developing. As the alkaline developer, various alkali solutions used in this field can be used. Generally, tetramethyl ammonium hydroxide and (2-hydroxyethyl) trimethyl ammonium hydroxide (aka choline) are used in the form of an aqueous solution. After development, if necessary, post-drying may be performed at about 150 to 230 DEG C for about 10 to 60 minutes.

Depth and profile of the pattern after development was measured in a 0.4 μm line and space pattern using a scanning electron microscope. As a result, it was found that the profile, depth of focus, sensitivity and the like of the resist composition according to the present invention were excellent.

The invention will be described in more detail by way of examples, but it is not intended to limit the scope of the invention.

<Examples>

&Lt; Preparation of photoresist composition >

To the novolak-based photoresist composition (Comparative Example 1, DWI-401, Dongwoo Fine Chem Co., Ltd.) containing a novolak-based resin, a low absorbing resin (molecular weight 7100) of the following formula (3) was added. The addition amount of the low light absorbing resin was varied to 5, 10 and 15 parts by weight (Examples 1, 2 and 3, respectively) based on 100 parts by weight of the novolak-based base resin to prepare a photoresist composition.

<Formula 3>

<Absorbance measurement>

The photoresist compositions of Comparative Example 1 and Examples 1, 2, and 3 were diluted in methanol at a concentration of 4 × 10 ⁻⁵ % and the light transmittance was measured with a UV-Visible spectrometer. The results are shown in Fig. That is, the transmittance of the novolak-based photoresist composition of Comparative Example 1 to which the low light absorbing resin was not added as shown at a wavelength of 248 nm was 15.87, whereas the light transmittances of Examples 1, 2, and 3 were 19.22, 22.97, 25.52 was increased by 21.11%, 44.74%, and 60.81%, respectively (FIG. 2A).

In addition, the light transmittance of Comparative Example 1 was 14.82 at a wavelength of 193 nm, whereas the light transmittances of Examples 1, 2, and 3 were increased to 15.87, 17.32, and 18.42, respectively, by 7.09%, 16.87%, and 24.29% (FIG. 2b).

&Lt; Pattern formation >

The photoresist compositions of Comparative Examples and Examples 1, 2 and 3 were applied onto a 6-inch silicon wafer with a hexamethyldisilazane (HMDS) treatment using a spin coater and free on a hot plate at 100 ° C. for 60 seconds. By baking and drying, a resist layer having a film thickness of 350 nm was formed.

The wafer having the resist film thus formed is exposed while the exposure amount is gradually changed using a scanning exposure apparatus ['NSR-S203B' manufactured by Nikon Corp., NA = 0.55, s = 0.75] having an exposure wavelength of 248 nm (KrF). To form a line and space pattern.

Then, post-exposure heat treatment (PEB) was performed at 90 ° C. for 60 seconds on a hot plate. In addition, paddle development was performed for 60 seconds using an aqueous 2.38% tetramethylammonium hydroxide (TMAH) solution, followed by rinsing with pure water to form a 0.4 μm line and space (1: 1) pattern.

The obtained patterns of Comparative Examples and Examples 1, 2, and 3 were observed using a scanning electron microscope (SEM), and the results are shown in FIG. 3. As shown, the embodiments could obtain a rectangular pattern without blockage or collapse of the pattern at a line width of 0.4 μm. However, when the novolak-based photoresist of the comparative example is exposed using a light source of KrF (248 nm), the pattern is not properly formed due to low transmittance (a of FIG. 3). However, in Examples 1, 2, and 3, as the amount of low absorbing resin added increased, a clear pattern was formed by increased transmittance (b-d of FIG. 3).

<Sensitivity Measurement>

The photoresist compositions of Comparative Examples and Examples were formed in the same manner as described above, but the exposure energy was changed to obtain a minimum exposure energy at which the pattern was formed to the bottom of the photoresist film. As a result, as shown in FIG. 4, the minimum exposure energy of the photoresist of Comparative Example 1 was 200 mJ / cm ^2. On the other hand, in the case of the photoresist of Examples 1, 2, 3 to 160, 100, 60 mJ / cm ² , it was confirmed that the sensitivity is improved.

The resist composition of the present invention has excellent performances such as sensitivity, resolution, residual film ratio, coating property, and the like in a short wavelength semiconductor process of 248 nm (KrF) or less even when applied in a non-chemically amplified type. Composition.

Claims (6)

Novolac base resins; Photosensitizers; And 5 to 50 parts by weight of a low absorbing resin relative to 100 parts by weight of the novolak base resin, wherein the absorbance of at least one wavelength of 248 nm, 193 nm, and 157 nm is lower than that of the novolak base resin. , The low light absorbing resin is obtained by diluting the photoresist composition in methanol at a concentration of 4 × 10 ⁻⁵ % (w / w), and measuring the light transmittance at a wavelength of 248 nm when the absorbance is measured with a UV-Vis spectrometer. The photoresist composition, wherein the low-absorbance resin is excluded from the composition, and the photoresist composition is increased by 10% or more compared to the light transmittance at a wavelength of 248 nm when the absorbance is measured by UV-Vis spectroscopy under the same conditions. delete The photoresist composition of claim 1, wherein the low light absorbing resin is a resin including at least one of structural units represented by Formula 1 and Formula 2. &Lt; Formula 1 >

(The above R1 is a linear, branched or cyclic alkyl or alkoxy, ester, ether, carbonyl, acetal, alcohol group having 1 to 15 carbon atoms, and R2 is hydrogen or an alkyl group having 1 to 5 carbon atoms.) (2)

(The said R3 is a C1-C5 alkyl group.) delete The photoresist composition of claim 1, wherein the photoresist composition is a non-chemically amplified photoresist.  Applying the photoresist composition of any one of claims 1, 3 and 5; Exposing a portion of the photoresist composition with light having a wavelength range of 248 nm or less in dominant wavelength; And Removing the exposed area or the non-exposed area of the photoresist composition.

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