KR20080068231A - Bi-layer photoresist polymer, composition comprising the same and manufacturing method of photoresist pattern using it - Google Patents

Abstract

A polymer for a bilayer photoresist, a photoresist composition containing the polymer, and a method for forming a photoresist pattern by using the composition are provided to allow post-etching process to be carried out stably without the collapse of a photoresist pattern. A polymer for a bilayer photoresist comprises a repeating unit represented by the formula 1 and a repeating unit represented by the formula 2, wherein R1 is a C1-C5 linear or branched alkyl group; R2 is a C1-C5 linear or branched alkylene group; R3 to R5 are a C1-C5 linear or branched alkyl group, respectively; and n is an integer of 1-5. Preferably the polymer comprises a repeating unit represented by the formula 3, wherein R6 is H or a C1-C5 linear or branched alkyl group.

Description

Bi-layer photoresist polymer, composition comprising the same and manufacturing method of photoresist pattern using it}

1A is a cross-sectional view showing a photoresist pattern obtained by a conventional method.

2A to 2D are cross-sectional views illustrating a method of forming a photoresist pattern in the present invention.

3 is an NMR graph of the photoresist polymer obtained in Example 1. FIG.

<Brief description of the main parts of the drawing>

1, 21: etching target layer 3: conventional photoresist pattern

23: first photoresist film 23-1: first photoresist pattern

25: second photoresist film 25-1: second photoresist pattern

25-2: cured second photoresist pattern 27: exposure mask

The present invention relates to a polymer for two-layer photoresist, a photoresist composition containing the polymer and a method of forming a photoresist pattern using the same.

As the application fields of semiconductor devices are expanded, researches to improve manufacturing processes have been continuously made in order to manufacture high-capacity memory devices having improved integration. The photolithography process is a line pattern forming process or an essential process performed to form a contact hole pattern.

On the other hand, as the size of the semiconductor device gradually decreases, the aspect ratio of the photoresist pattern increases while the pattern critical dimension (CD) required in the photolithography process decreases. As a result, a phenomenon occurs in which the photoresist pattern 3 collapses in a subsequent cleaning process (see FIG. 1).

In order to improve the above disadvantages, it is difficult to ensure sufficient etching resistance to be used as an etching mask in the subsequent etching process for the etched layer 1 as the thickness of the formed photoresist film is gradually reduced.

In particular, since the photoresist material for ArF that does not contain an aromatic compound such as benzene is less etch resistant than the photoresist material for KrF, when the subsequent etching process is performed using the photoresist pattern as an etching mask, the etching target layer cannot be effectively removed. Another problem arises that circuit formation is impossible.

Conventionally, although a method of developing a new etching process has been attempted to increase the etching resistance of the photoresist material for ArF, not only there is a limit in increasing the etching resistance, but also there is a disadvantage in that the production cost increases.

An object of the present invention is to provide a polymer for a two-layer photoresist comprising a silicon compound and a norbornene compound and a photoresist composition containing the polymer in order to obtain a photoresist with improved etching resistance.

Another object of the present invention is to provide a method of forming a photoresist pattern having a two-layer structure by using the photoresist composition.

In order to achieve the above object,

The present invention provides a polymer for a two-layer photoresist comprising a polymerized repeating unit represented by Formula 1 and a polymerized repeating unit represented by Formula 2 below.

[Formula 1]

[Formula 2]

Where

R ₁ is C ₁ -C ₅ linear or branched alkyl,

R ₂ is C ₁ to C ₅ linear or branched alkylene,

R ₃ to R ₅ are each C _{1 to} C ₅ straight or branched alkyl,

n is an integer of 1-5.

The polymerization repeating unit of Chemical Formula 1 is (endo, endo) -bicyclo [2.2.1] -hept-5-ene-2,3-dicarboxylic acid dimethyl ether [(endo, endo) -bicyclo (2.2.1)- hept-5-ene-2,3-dicarboxylic acid dimethyl ester] and the polymerization repeating unit of formula 2 is derived from 3- (trimethoxysilyl) propyl methacrylate Is preferred.

In the polymerization repeating unit of Chemical Formula 1, the -COOR ₁ group increases the adhesion property when it is applied to a wafer to increase the coating uniformity.

Since the polymerization repeating unit of Formula 2 has a long chain (chain) form to prevent the cyclic hindrance between the end groups, it is easy to prepare a polymer. When performing the subsequent O ₂ plasma etching process, the repeating unit of Formula 2 is glass-cured in the form of a silicon oxide film while being cross-linked with oxygen atoms and cured. Therefore, the etching resistance of the photoresist may be improved during the subsequent CF ₄ plasma etching process on the etched layer.

In addition, the polymer of the present invention may further include a polymerization repeating unit represented by Chemical Formula 3 as a comonomer.

[Formula 3]

Where

R ₆ is H or C _{1 to} C ₅ linear or branched alkyl.

The polymerization repeating unit represented by Chemical Formula 3 is more preferably derived from a compound having an alcohol end group to secure the etching resistance of the photoresist, for example, derived from methacrylic acid. At this time, since the repeating unit of Formula 3 includes -OH group as the end group, it is possible to further improve the coating uniformity during wafer application.

Therefore, the polymer of the present invention preferably includes a polymerization repeating unit (repeating unit) represented by the following formula (4).

[Formula 4]

Where

R ₁ is C ₁ -C ₅ straight or branched alkyl, R ₂ is C ₁ -C ₅ straight or branched alkylene, and R ₃ to R ₅ are each C ₁ -C ₅ straight or branched Alkyl, R ₆ is H or C _{1 to} C ₅ straight or branched alkyl, n is an integer from 1 to 5,

The molar relative ratio of a: b: c is 0.4-0.7: 1-1.0.7: 1.

As for the polymerization repeating unit of Formula 4, the following Formula 4a is preferable.

[Formula 4a]

In the above formula, the molar relative ratio of a: b: c is 0.4 to 0.7: 1 to 0.7: 1.

The photoresist polymer of the present invention can be prepared using a radical polymerization reaction, the radical polymerization is carried out by bulk polymerization or solution polymerization.

In the case of the solution polymerization, the polymerization solvent is selected from the group consisting of tetrahydrofuran, cyclohexanone, cyclopentanone, dimethylformamide, dimethyl sulfoxide, methyl ethyl ketone, dioxane, benzene, toluene and xylene, and the like. It is preferable to use a solvent or a mixed solvent.

The polymerization reaction was carried out with 2,2'-azobisisobutyronitrile (AIBN), benzoyl peroxide, acetyl peroxide, lauryl peroxide, t-butylperacetate, t-butylhydroperoxide and di-t-butyl Peroxide, etc., in the presence of a polymerization initiator selected from the group consisting of.

In addition, the present invention includes a photoresist composition comprising the photoresist polymer, a photoacid generator and an organic solvent.

The photoacid generator may be used as long as the compound can generate an acid by light, US 5,212,043 (May 18, 1993), WO 97/33198 (September 12, 1997), WO 96/37526 (1996. 11.28), EP 0 794 458 (September 10, 1997) EP 0 789 278 (August 13, 1997), US 5,750,680 (May 12, 1998), US 6,051,678 (April 18, 2000), GB 2,345,286 A (August 7, 2000), US 6,132,926 (October 17, 2000), US 6,143,463 (Nov. 7, 2000), US 6,150,069 (November 21, 2000), US 6.180.316 B1 (January 30, 2001) ), US 6,225,020 B1 (May 1, 2001), US 6,235,448 B1 (May 22, 2001) and US 6,235,447 B1 (May 22, 2001) and the like, and mainly include sulfide-based or onium salt-based compounds use. In particular, low absorbance at 157 nm and 193 nm phthalimidotrifluoromethane sulfonate, dinitrobenzyltosylate, n-decyl disulfone, naphthylimidotrifluoromethane Sulfonate (naphthylimido trifluoromethane sulfonate), diphenylurodoxyl hexafluorophosphate, diphenylurodolic acid hexafluoro arsenate, diphenylurodolic acid hexafluoro antimonate, diphenylparamethoxyphenylsulfonium triflate, diphenylpara Toluenylsulfonium triflate, diphenylparaisobutylphenylsulfonium triflate, triphenylsulfonium hexafluoro arsenate, triphenylsulfonium hexafluoro antimonate, triphenylsulfonium triflate and dibutylnaph One or more selected from the group consisting of thylsulfonium triflate may be used, and It is preferably used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the toresist polymer. When the photoacid generator is used at 0.01 parts by weight or less, the sensitivity of the photoresist to light is weak. When the photoacid generator is used at 5 parts by weight or more, the photoacid generator absorbs a lot of ultraviolet rays and a large amount of acid is generated to obtain a pattern having a bad cross section.

Further, the organic solvent is not particularly limited as long as it is an organic solvent capable of dissolving the compounds, but is not limited to US 5,212,043 (May 18, 1993), WO 97/33198 (September 12, 1997), WO 96/37526 (1996. 11.28), EP 0 794 458 (September 10, 1997) EP 0 789 278 (August 13, 1997), US 5,750,680 (May 12, 1998), US 6,051,678 (April 18, 2000), GB 2,345,286 A (August 7, 2000), US 6,132,926 (October 17, 2000), US 6,143,463 (Nov. 7, 2000), US 6,150,069 (November 21, 2000), US 6.180.316 B1 (January 30, 2001) ), US 6,225,020 B1 (May 1, 2001), US 6,235,448 B1 (May 22, 2001) and US 6,235,447 B1 (May 22, 2001) and the like, preferably diethylene glycol diethyl ether ( diethylene glycol diethyl ether), methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propylene glycol methyl ether acetate, cyclohexanone or 2-heptanone, and the like can be used alone or in combination. The organic solvent is used in an amount of 500 to 2000 parts by weight based on 100 parts by weight of the photoresist polymer, for obtaining a photoresist film having a desired thickness, for example, when the organic solvent is used in an amount of 1000 parts by weight for the photoresist polymer. The photoresist thickness is about 0.25 μm.

In the present invention,

(a) forming a first photoresist film on the etched layer;

(b) coating the photoresist composition of the present invention on the first photoresist film and baking the same to form a second photoresist film;

(c) forming a second photoresist pattern by performing an exposure and development process on the second photoresist film; And

(d) performing an O ₂ plasma etching process on the first photoresist layer using the second photoresist pattern as an etching mask,

It provides a photoresist pattern forming method comprising the step of forming a two-layer photoresist pattern of the first and second photoresist pattern is a laminated structure.

The method may further include, after the etching process of step (d), performing a CF ₄ plasma etching process on the lower etching layer using the two-layer photoresist as an etching mask to form an etching layer pattern.

The photoresist polymer including the silicon compound and the compound having an alcohol end group as described above and the photoresist composition containing the same not only have thermal stability of the photoresist film, but also have high wettability to a developer, thereby forming a stable photoresist pattern. can do. In addition, in the above method, the second photoresist pattern not only has excellent resolution, but also includes a compound having a silicon-based compound and an alcohol end group, thereby improving etching resistance, thereby preventing the pattern from falling down. Even if the first photoresist is thinly formed at less than 4000 GPa, an etching selectivity that can be used as a barrier during an etching process on a subsequent etching layer can be obtained.

Furthermore, since the thickness of the photoresist film is reduced by securing the etching resistance, not only the pattern collapse can be prevented, but also the process margin can be secured, thereby forming a high-resolution pattern by a stable subsequent etching process.

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

First, as shown in FIG. 2A, a first photoresist film 23 is formed on the etched layer 21.

In this case, the etched layer is formed using one material selected from an oxide film, a nitride film, a polycrystalline silicon film, a borophosphosilicate glass (BPSG), aluminum, tungsten, cobalt, an organic diffuse reflection prevention material, or a metal such as titanium.

The first photoresist film is preferably formed at a thickness of 4000 GPa or less, preferably 3000 to 4000 GPa.

The first photoresist film is a general photoresist material for ArF, for example, any chemically amplified polymer can be used, US 5,212,043 (May 18, 1993), WO 97/33198 (September 12, 1997), WO 96/37526 (Nov. 28, 1996), EP 0 794 458 (September 10, 1997) EP 0 789 278 (August 13, 1997), US 5,750,680 (May 12, 1998), US 6,051,678 (April 2000) 18), GB 2,345,286 A (July 5, 2000), US 6,132,926 (October 17, 2000), US 6,143,463 (November 7, 2000), US 6,150,069 (11.11.2000), US 6.180.316 B1 (January 30, 2001), US 6,225,020 B1 (May 1, 2001), US 6,235,448 B1 (May 22, 2001) and US 6,235,447 B1 (May 22, 2001) and the like. In particular, the photoresist film is a ROMA-type polymer including a ring-opened maleic anhydride (ROMA) as a repeating unit; A COMA-type copolymer comprising a methacrylate or acrylate-based polymerization repeating unit, a cycloolefin polymerization repeating unit, and a cycloolefin-maleic anhydride polymerization repeating unit; And a polymer selected from among the polymers of the hybrid type as the base resin, and more preferably poly (t-butyl bicyclo [2.2.1] hept-5-ene-2-carboxylate). / 2-hydroxyethyl bicyclo [2.2.1] hept-5-ene-2-carboxylate / bicyclo [2.2.1] hept-5-ene-2-carboxylic acid / maleic hydride) and the like can be used. Can be. The photoresist material for ArF may be used instead of the photoresist material for KrF.

The photoresist composition of the present invention is coated on the first photoresist film 23 and then baked to sequentially form the second photoresist film 25.

The second photoresist film is preferably formed to a thickness of 500 to 1500 kPa, more preferably 1000 kPa.

As shown in FIG. 2B, an exposure process using an exposure mask 27 is performed on a predetermined region of the second photoresist film 25 and then baked.

It is carried out with an exposure energy of 1 to 100mJ / cm ² using a light source of KrF, ArF, Extreme Ultra Violet (EUV), Vacuum Ultra Violet (VUV), E-beam, X-ray or ion beam of the exposure process. desirable.

The resultant of FIG. 2B is developed to form the second photoresist pattern 25-1 as shown in FIG. 2C. Then, the photoresist pattern is etched to form an O ₂ etch gas for the first photoresist layer. The plasma dry etching process is used.

In this case, as illustrated in FIG. 2D, a two-layer photoresist pattern in which the hardened second photoresist pattern 25-2 is stacked is formed on the first photoresist pattern 23-1.

Next, a CF ₄ plasma dry etching process is performed on the etched layer 21 by using the two-layer photoresist pattern as an etch mask to form a predetermined etched layer pattern.

That is, silicon present in the second photoresist pattern 25-1 reacts with the O ₂ etching gas during the O ₂ plasma etching process, thereby forming silicon oxide bonds. The silicon oxide bond has a strong etching resistance to the plasma etching gas, such as CF ₄ used in the subsequent etching process. Thus, the method of the present invention can simultaneously solve the problem of pattern collapse due to the weak resistance and aspect ratio of the ArF resist.

Hereinafter, the present invention will be described in detail by way of examples. However, the examples are only to illustrate the invention and the present invention is not limited by the following examples.

I. Method of Making Photoresist Polymer.

Example 1 Synthesis of Photoresist Polymer of Formula 5a

(Endo, endo) -bicyclo [2.2.1] -hept-5-ene-2,3-dicarboxylic acid dimethyl ether (3mole) (Aldrich Co.), 3- (trimethoxysilyl) propyl (5mole) ( Aldrich Co.), methacrylic acid (3 mole) (Aldrich Co.) and 2,2′-azobisisobutyronitrile (0.13 mole) were dissolved in 600 ml of tetrahydrofuran, and the solution was then heated for about 24 hours under argon atmosphere. Stir slowly at about 67 ° C. The reaction solution was precipitated in methanol, filtered and washed several times with methanol, and then dried under reduced pressure to obtain a compound of Chemical Formula 5a (yield 50%, see NMR graph of FIG. 3).

II. Photoresist composition preparation and pattern formation method

Example 2

(Step 1)

The polymer (1 g) prepared in Example 1 and the photoacid generator phthalimidotrifluoromethanesulfonate (0.01 g) were dissolved in propylene glycol methyl ethyl acetate (PGMEA) (8 g), and then filtered through a 0.20 μm filter to photoresist. A composition was obtained.

(Step 2)

An ArF first photoresist film (AX1020P, Clariant Co.) was formed on the etched layer to a thickness of 3500 kPa, the composition obtained in step 1 was spin coated on the film to 1000 kPa, and then soft baked at 140 ° C. for 90 seconds. To form a second photoresist film (see FIG. 2A).

The second photoresist film was exposed with an ArF laser exposure apparatus (see FIG. 2B). The resultant was post-baked again at 140 ° C. for 90 seconds and then immersed in a 2.38 wt% TMAH aqueous solution for 90 seconds to develop a second photoresist L / S pattern of 0.15 μm. Next, an O ₂ plasma etching process is performed on the first resist layer using the second photoresist pattern as an etch mask, thereby forming a second photoresist pattern on the first photoresist pattern of 0.15 μm L / An S pattern was formed (see FIGS. 2C and 2D).

As described above, in the method of the present invention by providing a two-layer photoresist pattern formed with a second photoresist pattern excellent in etching resistance on the ArF photoresist pattern having a low aspect ratio and using it as an etching mask, It is possible to perform a stable subsequent etching process, thereby improving the yield of the device.

Claims (20)

A photoresist polymer comprising a polymerized repeating unit of Formula 1 and a polymerized repeating unit of Formula 2 below: [Formula 1]

[Formula 2]

Where R ₁ is C ₁ -C ₅ linear or branched alkyl, R ₂ is C ₁ to C ₅ linear or branched alkylene, R ₃ to R ₅ are each C _{1 to} C ₅ straight or branched alkyl, n is an integer of 1-5. The method of claim 1, The photoresist polymer is used for a two-layer photoresist pattern forming process. The method of claim 1, The polymer repeating unit of Formula 1 is a photoresist polymer, characterized in that derived from (endo, endo) -bicyclo [2.2.1] -hept-5-ene-2,3-dicarboxylic acid dimethyl ether. The method of claim 1, The polymer repeating unit of Formula 2 is a photoresist polymer, characterized in that derived from 3- (trimethoxysilyl) propyl methacrylate. The method of claim 1, The polymer is a photoresist polymer, characterized in that further comprises a polymerization repeating unit of the formula [Formula 3]

Where R ₆ is H or C _{1 to} C ₅ linear or branched alkyl. The method of claim 5, Polymeric repeating unit of Formula 3 is a photoresist polymer, characterized in that derived from methacrylic acid. The method of claim 5, The polymer is a photoresist polymer, characterized in that it comprises a polymerized repeating unit of formula: [Formula 4]

Where R ₁ is C ₁ -C ₅ linear or branched alkyl, R ₂ is C ₁ to C ₅ linear or branched alkylene, R ₃ to R ₅ are each C _{1 to} C ₅ straight or branched alkyl, R ₆ is H or C ₁ -C ₅ linear or branched alkyl, n is an integer from 1 to 5, The molar ratio of a: b: c is 0.4-0.7: 1-10.7: 1. The method of claim 7, wherein The polymerized repeating unit of Formula 4 is a polymer for photoresist, characterized in that the polymerization repeating unit of the formula 4a: [Formula 4a]

In the above formula, the molar ratio of a: b: c is 0.4 to 0.7: 1 to 0.7: 1. A photoresist composition comprising the polymer for photoresist of claim 1, a photoacid generator and an organic solvent. The method of claim 9, The photoacid generator is phthalimidotrifluoromethanesulfonate, dinitrobenzyltosylate, n-decyldisulfone, naphthylimidotrifluoromethanesulfonate, diphenyl iodo salt hexafluorophosphate, diphenyl iodo salt hexafluoro Arsenate, Diphenyl iodo salt hexafluoro antimonate, Diphenyl paramethoxyphenylsulfonium triflate, Diphenyl paratoluenylsulfonium triflate, Diphenyl paraisobutylphenyl sulfonium triflate, triphenylsulfonium Hexafluoro arsenate, triphenylsulfonium hexafluoro antimonate, triphenylsulfonium triflate and dibutyl naphthylsulfonium triflate composition for a photoresist, characterized in that. The method of claim 9, The photoresist is a photoresist composition, characterized in that used in 0.01 to 5 parts by weight based on 100 parts by weight of the photoresist polymer. The method of claim 9, The organic solvent is diethylene glycol diethyl ether, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propylene glycol methyl ether acetate, cyclohexanone and 2-heptanone. A composition for photoresist, characterized in that selected from the group consisting of. The method of claim 9, The organic solvent is a photoresist composition, characterized in that used in 500 to 2000 parts by weight based on 100 parts by weight of the photoresist polymer. (a) forming a first photoresist film on the etched layer; (b) coating the photoresist composition of claim 9 on the first photoresist film, and baking to form a second photoresist film; (c) performing a process of exposing and developing the second photoresist film to form a second photoresist pattern; And (d) performing an O ₂ plasma etching process on the first photoresist layer using the second photoresist pattern as an etching mask, Forming a two-layer photoresist pattern having a stacked structure of first and second photoresist patterns. The method of claim 14, After the etching step (d), using the two-layer photoresist pattern as an etching mask using a CF ₄ plasma etching process for the lower etching layer further comprises the step of forming an etching layer pattern Forming method. The method of claim 14, And the first photoresist film is formed to a thickness of 3000 to 4000 GPa. The method of claim 14, And the second photoresist film is formed to a thickness of 500 to 1500 kPa. The method of claim 14, The first photoresist film may include a ROMA type polymer including a ring-opened maleic hydride as a repeating unit; A COMA-type copolymer comprising a methacrylate or acrylate-based polymerization repeating unit, a cycloolefin polymerization repeating unit, and a maleic anhydride polymerization repeating unit; And a polymer selected from the group consisting of a polymer having a mixed type of the polymer as a base resin. The method of claim 18, The first photoresist film is poly (t-butyl bicyclo [2.2.1] hept-5-ene-2-carboxylate / 2-hydroxyethyl bicyclo [2.2.1] hept-5-ene-2- Carboxylate / bicyclo [2.2.1] hept-5-ene-2-carboxylic acid / maleic anhydride). The method of claim 14, And the exposure process uses a light source selected from the group consisting of KrF, ArF, EUV, VUV, E-beam, X-ray and ion beam.

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