WO2019190064A1 - Composition for hard mask and pattern forming method using same - Google Patents

Abstract

Provided is a composition for a hard mask, which comprises a copolymer containing polybenzoxazole or a precursor thereof, and a solvent. A hard mask improved in both heat resistance and etching resistance can be formed from the composition for a hard mask.

Description

Composition for hard mask and pattern formation method using same

The present invention relates to a composition for a hard mask and a pattern forming method using the same. More particularly, the present invention relates to a hard mask composition comprising an aromatic structure-containing copolymer and a pattern forming method using the same.

For example, in the field of semiconductor manufacturing, microelectronics, and the like, the degree of integration of structures such as circuits, wiring, insulation patterns, and the like is continuously improving. Accordingly, a photolithography process for the fine patterning of the structures has been developed together.

In general, a photoresist is formed on the etching target layer to form a photoresist layer, and a photoresist pattern is formed through an exposure and development process. Subsequently, a predetermined pattern may be formed by partially removing the etching target layer using the photoresist pattern as an etching mask. After the image transfer to the etch target layer is performed, the photoresist pattern may be removed through an ashing and / or strip process.

An anti-refractive coating (ARC) layer may be formed between the etching target layer and the photoresist layer in order to suppress the resolution degradation due to light reflection during the exposure process. In this case, etching may be added to the ARC layer, thereby increasing the consumption amount or etching amount of the photoresist layer or the photoresist pattern. In addition, when the thickness of the etching target layer is increased or the amount of etching required to form a desired pattern is increased, sufficient etching resistance of the photoresist layer or photoresist pattern may not be secured.

Therefore, a resist underlayer may be added between the etching target layer and the photoresist layer to secure an etch resistance and an etching selectivity of the photoresist for forming a desired pattern.

The resist underlayer, for example, needs to have sufficient etching resistance (or etching resistance) to a high temperature etching process, and sufficient heat resistance to prevent mass loss in a high temperature process.

Korean Laid-Open Patent Publication No. 10-2010-0082844 discloses an example of a resist underlayer forming composition.

One object of the present invention is to provide a hard mask composition capable of forming a hard mask having improved mechanical, chemical and film forming properties of the present invention.

One object of the present invention is to provide a pattern forming method utilizing the composition for the hard mask.

1. a copolymer containing polybenzoxazole or a precursor thereof; And a solvent, the composition for a hard mask.

2. according to the above 1, wherein the carbon content of the polybenzoxazole is 75% or more, the composition for hard mask.

3. In the above 2, wherein the polybenzoxazole comprises a reactant of the first precursor monomer of Formula 1 and the second precursor monomer of Formula 2, the composition for the hard mask:

[Formula 1]

[Formula 2]

(In Formula 2, X is a halogen or -OR group, R is an aliphatic hydrocarbon group of 1 to 12 carbon atoms or an aromatic hydrocarbon group of 6 to 12 carbon atoms)

4. In the above 3, wherein the polybenzoxazole is a reactant of the first precursor monomer, the second precursor monomer and the end capping agent of the formula (3), a composition for a hard mask:

[Formula 3]

(In Formula 3, X is a halogen or -OR group, and R is an aliphatic hydrocarbon group having 1 to 12 carbon atoms or an aromatic hydrocarbon group having 6 to 12 carbon atoms).

5. In the above 2, wherein the polybenzoxazole is a hard mask composition comprising a structure represented by the following formula (4):

[Formula 4]

(In Formula 4, n is an integer of 1 to 100)

6. according to the above 2, the weight average molecular weight of the polybenzoxazole is 900 to 5,000, the composition for hard mask.

7. In the above 1, wherein the copolymer further comprises a copolymer of aromatic compounds comprising a structural unit represented by the following formula (5), a composition for a hard mask:

[Formula 5]

(In Formula 5, Ar1 is a C10-C30 arylene group which has a multiple aromatic ring structure, and Ar2 is a C10-C30 aryl group which has a multiple aromatic ring structure.).

8. according to the above 1, 5 to 30% by weight of the copolymer in the total weight of the composition, and 70 to 95% by weight of the solvent composition for the hard mask.

9. forming an etching target layer on the substrate; Forming a hard mask layer by applying the hard mask composition of any one of 1 to 8 on the etching target layer; Forming a photoresist pattern on the hard mask film; Etching the hard mask layer using the photoresist pattern to form a hard mask pattern; And etching the etching target layer by using the hard mask pattern.

By using the composition for a hard mask according to the embodiments of the present invention, it is possible to form a hard mask having excellent heat resistance and improved etching resistance and solubility.

The hard mask composition according to the embodiments of the present invention includes polybenzoxazole and does not substantially cause mass loss even at a high temperature of 600 ° C. or higher. Thus, for example, a rigid mask structure can be stably maintained in a high temperature semiconductor manufacturing process.

In some embodiments, the polybenzoxazole may be selected from precursors to have a carbon content of about 75% or more to secure the etch resistance required for the hardmask. In addition, by controlling the weight average molecular weight of the polybenzox group, it is possible to improve the solubility together to improve the film-forming properties such as coating properties, flatness.

A high resolution photolithography process may be implemented using a hard mask formed from the composition for the hard mask, and may form a target pattern having a desired fine line width.

1 is a thermogravimetric analysis (TGA) reference graph for explaining the heat resistance of polybenzoxazole.

2 to 6 are schematic cross-sectional views for describing a method of forming a pattern according to example embodiments.

Embodiments of the present invention include a polybenzoxazole as a protecting group, and provides a composition for a hard mask having improved heat resistance.

By using the hard mask composition, for example, a hard mask layer may be formed between the photoresist layer and the etching target layer to be utilized as a resist lower layer. The hard mask layer may be partially removed through the photoresist pattern to form a hard mask, and the hard mask may be used as an additional etching mask.

The hard mask layer or hard mask may be used as, for example, a spin-on hard mask (SOH).

Hereinafter, a hard mask composition according to embodiments of the present invention will be described in detail. When there is an isomer of a compound or resin represented by the chemical formula used in the present application, the compound or resin represented by the chemical formula means a representative chemical formula including the isomer.

The term "carbon content" as used herein may refer to the ratio of the carbon mass number to the total mass number per molecule of the compound.

As used herein, the term "aromatic" or "aromatic compound" is used to encompass not only a compound in which the entire compound satisfies aromaticity but also some structures or groups of the compound satisfying aromaticity.

The term "polycyclic aromatic" as used herein may include a structure in which a plurality of aromatic rings are oriented and fused.

<Composition for Hard Mask>

The hard mask composition according to the embodiments of the present invention may include a copolymer and a solvent including polybenzoxazole, and may further include additional agents such as a crosslinking agent and a catalyst.

Copolymer

The hard mask composition according to exemplary embodiments may include polybenzoxazole (PBO) as a copolymer used as a base resin.

1 is a thermogravimetric analysis (TGA) reference graph for explaining the heat resistance of polybenzoxazole.

Referring to FIG. 1, mass loss occurs rapidly in the case of polyimide (PI) and polyacrylic acid (PAA) when the polymer temperature rises to 600 ° C. However, polybenzoxazole does not substantially lose mass even at 600 ° C, and at least 80% of mass is maintained at 800 ° C.

As shown in FIG. 1, polybenzoxazole may be used as a material having excellent high heat resistance characteristics among commercially available polymer resin structures. In embodiments of the present invention, for example, a hard mask used in a semiconductor photo etching process It can be used as the base resin of the composition.

The polybenzoxazole precursor may be formed by reacting a first precursor monomer including a diamino alcohol compound as a precursor monomer, and a second precursor monomer including a diester compound or a diacyl halide compound to prepare polybenzoxazole.

Thereafter, the polybenzoxazole precursor may be thermally cured to produce polybenzoxazole together with a dehydration reaction.

According to exemplary embodiments, at least about 75% of polybenzoxazole may be used to secure the hard mask to be etched.

The precursor monomers may be selected in consideration of the at least about 75% polybenzoxazole structure implementation.

In one embodiment, the compound of formula 1 may be used as the first precursor monomer.

[Formula 1]

In one embodiment, the compound of formula 2 may be used as the second precursor monomer.

[Formula 2]

In Formula 2, X may be a halogen or —OR group such as Cl, and R may be an aliphatic hydrocarbon group having 1 to 12 carbon atoms (eg, an alkyl group), or an aromatic hydrocarbon group having 6 to 12 carbon atoms.

The amine group of the first precursor monomer nucleophilic attack the carbonyl carbon of the second precursor monomer to form a hydroxy amide structure to produce the polybenzoxazole precursor, the polybenzoxazole precursor is heat according to Scheme 1 Curing can produce polybenzoxazoles.

Scheme 1

According to exemplary embodiments, a compound in which two aromatic rings are directly connected or fused as a precursor monomer may be used as in Formula 1 and Formula 2. Therefore, it is possible to prevent the reduction of the carbon content according to the intermediate residues between the aromatic rings to achieve a high carbon content of about 75% or more. Therefore, polybenzoxazole for hard mask with improved heat resistance and improved etching resistance can be obtained.

In some embodiments, polybenzoxazole having a carbon content of 80% or more may be used as the copolymer.

In some embodiments, an end capping agent may be used with the precursor monomers for chain termination of the polybenzoxazole precursor. The molecular weight of the polybenzoxazole can be adjusted according to the content of the end capping agent.

In some embodiments, the end capping agent may include a compound represented by Formula 3 below.

[Formula 3]

X in formula 3 is as defined in formula (2).

As represented by Formula 3, the end capping agent may also use a compound in which two aromatic rings are fused, thereby maintaining a high carbon content of polybenzoxazole.

In some embodiments, the polybenzoxazole may include a structure represented by Formula 4 below.

[Formula 4]

In Formula 4, n may be an integer of 1 to 100, preferably an integer of 1 to 10.

In some embodiments, the hard mask composition may include a polybenzoxazole precursor. For example, it may include a polyhydroxy amide corresponding to the polybenzoxazole structure of the formula (4).

In this case, a hard mask film including polybenzoxazole represented by Formula 4 may be formed through a curing process or a baking process performed after the composition for the hard mask is applied.

In some embodiments, the weight average molecular weight of the polybenzoxazole may be adjusted in the range of about 900 to 5,000. If the weight average molecular weight of the polybenzoxazole is less than about 900, the hardness and mechanical properties of the hard mask may be somewhat degraded. When the weight average molecular weight of the polybenzoxazole is greater than about 5,000, the solubility of the polybenzoxazole may be excessively reduced to deteriorate the coating property and storage stability of the composition for a hard mask.

In one preferred embodiment, the weight average molecular weight of the polybenzoxazole can be adjusted in the range of about 1,000 to 4,000.

As mentioned above, the weight average molecular weight of the polybenzoxazole can be adjusted through, for example, the content of the end capping agent.

The content of the polymer is not particularly limited, but may be, for example, about 5 to 30% by weight of the total weight of the composition for a hard mask, and in one embodiment, about 10 to 30% by weight.

In some embodiments, the copolymer may further include a copolymer of aromatic compounds including a structural unit represented by Formula 5 together with polybenzoxazole.

[Formula 5]

In Formula 5, Ar1 may be an arylene group having 10 to 30 carbon atoms having a multi aromatic ring structure, and Ar2 may be an aryl group having 10 to 30 carbon atoms having a multi aromatic ring structure.

In some embodiments, Ar 1 includes a pyrene structure and Ar 2 may be a naphthyl group. In this case, the copolymer of the aromatic compounds may be represented by the following Chemical Formula 5-1.

[Formula 5-1]

As indicated in Formula 5-1, copolymers containing high carbon content units such as pyrene can be used in combination with polybenzoxazoles to obtain hard masks with balanced heat and etch resistance.

For example, when polybenzoxazole and a copolymer of the aromatic compounds are used together, it may be used in a weight ratio of about 4: 6 to 6: 4.

The content of the copolymer is not particularly limited, but may be, for example, about 5 to 30% by weight of the total weight of the composition for the hard mask, and may be about 10 to 30% by weight in one embodiment.

menstruum

The solvent used in the hard mask composition according to the embodiments of the present invention is not particularly limited and may include an organic solvent having sufficient solubility in the polycondensate described above. For example, the solvent is propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), cyclohexanone, ethyl lactate, gamma-butyrolactone (γ-butyrolactone; GBL), acetyl acetone, and the like.

The content of the solvent is not particularly limited, and may be included in the remaining amount except for the polycondensate and additional agents described below. For example, the solvent may be included in about 70 to 95% by weight of the total weight of the composition for the hard mask.

Additional formulations

Optionally, the composition for a hard mask according to embodiments of the present invention may further include additional agents such as a crosslinking agent, a catalyst, and a surfactant.

For example, when a copolymer of the above-mentioned aromatic compounds is further included as a copolymer, the crosslinking agent may react with hydroxyl groups included in the copolymer. By the crosslinking agent, the curing characteristics of the composition for a hard mask may be further enhanced.

As an example of the said crosslinking agent, a melamine, an amino resin, a glycoluril compound, a bisepoxy compound, etc. are mentioned.

Such crosslinking agents include, for example, etherified amino resins such as methylated or butylated melamine (specific examples being N-methoxymethyl-melamine or N-butoxymethyl-melamine) and methylated or butylated Urea resin (specific examples, Cymel U-65 Resin or UFR 80 Resin), glycoluril derivatives (see Formula 6, specific examples of Powderlink 1174), bis (hydroxymethyl) -p represented by Formula 7 -Cresol compounds and the like. In addition, the bisepoxy-based compound represented by the following formula (8) and the melamine-based compound represented by the following formula (9) can also be used as the crosslinking agent.

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

As the catalyst, an acid catalyst or a basic catalyst may be used.

The acid catalyst may use a heat activated acid catalyst. As an example of the acid catalyst, an organic acid such as p-toluene sulfonic acid may be used. As the acid catalyst, a compound of a thermal acid generator (TAG) system may be used. As examples of the thermal acid generator-based catalyst, pyridinium p-toluene sulfonate, 2,4,4,6-tetrabromocyclohexadienone, benzointosylate, 2-nitrobenzyltosyl And alkyl esters of eutectic acid and the like.

As the basic catalyst, any one selected from ammonium hydroxide represented by NH ₄ OH or NR ₄ OH (R is an alkyl group) may be used.

When the crosslinking agent is included, the content of the crosslinking agent may be about 1 to 30 parts by weight, preferably about 5 to 20 parts by weight, and more preferably about 5 to 10 parts by weight, based on 100 parts by weight of the polycondensate.

When the catalyst is included, the content of the catalyst may be about 0.001 to 5 parts by weight, preferably about 0.1 to 2 parts by weight, and more preferably about 0.1 to 1 part by weight, based on 100 parts by weight of the polycondensate. Can be.

Within the content range of the crosslinking agent and the catalyst, appropriate crosslinking properties can be obtained without deteriorating the etch resistance, heat resistance, solubility, and flatness of the copolymer.

The composition for a hard mask according to the embodiments of the present invention may further include a surfactant to improve the surface properties, adhesion of the hard mask. As the surfactant, alkylbenzene sulfonate, alkylpyridinium salt, polyethylene glycol, quaternary ammonium salt, and the like may be used, but are not limited thereto. The amount of the surfactant may be, for example, about 0.1 to 10 parts by weight based on 100 parts by weight of the polycondensate.

<Pattern forming method>

2 to 6 are schematic cross-sectional views for describing a method of forming a pattern according to example embodiments. 2 to 6 provide a pattern forming method using a hard mask composition according to the embodiments of the present invention described above.

Referring to FIG. 2, an etching target layer 110 may be formed on the substrate 100. The substrate 100 may be, for example, a semiconductor substrate including single crystal silicon, single crystal germanium, or the like.

The etching target layer 110 may include a conductive material such as metal or metal nitride, an insulating material such as silicon oxide or silicon nitride, or a semiconductor material such as polysilicon according to the use of the target pattern.

Referring to FIG. 3, the hard mask composition 120 may be applied to the etching target layer 110 by, for example, a spin coating process to form the hard mask layer 120.

As described above, the hard mask composition may include polybenzoxazole as a copolymer. In one embodiment, the hard mask composition may include a polybenzoxazole precursor. In this case, the hard mask layer 120 including the polybenzoxazole may be formed through a baking process after applying the composition for the hard mask. The baking process may be performed, for example, at a temperature of about 100 to 400 ° C.

Referring to FIG. 4, a photoresist film 130 may be formed on the hard mask film 120.

Referring to FIG. 5, the photoresist film 130 may be selectively exposed and developed to form a photoresist pattern 135. During the exposure process, the hard mask film 120 may substantially function as an antireflection film, thereby improving the resolution of the exposure process.

Referring to FIG. 6, a hard mask pattern 125 may be formed by selectively etching the hard mask layer 120 using the photoresist pattern 135.

Subsequently, by using the photoresist pattern 135 and the hard mask pattern 125 together as an etch mask to selectively remove the etch target layer 110, a predetermined target pattern 115 may be formed.

The hard mask pattern 125 includes, for example, polybenzoxazole having a carbon content of 75% or more, and has a high resistance to corrosion, for example, from an etching gas (eg, CF ₃ ) used in a dry etching process. Etch damage can be prevented. Therefore, a rigid etching mask structure is maintained during the etching process, and a target pattern 115 having a desired pattern profile may be formed.

Hereinafter, experimental examples including specific examples and comparative examples are provided to help understanding of the present invention, but these are merely illustrative of the present invention and are not intended to limit the scope of the appended claims. It is apparent to those skilled in the art that various changes and modifications to the embodiments can be made within the spirit and scope, and such variations and modifications are within the scope of the appended claims.

Examples and Comparative Examples

To prepare a composition for a hard mask of the composition and content (% by weight) described in Table 1.

A-1:

,

,

(4: 1 weight average molecular weight: 900, n = 1)

[Formula 4]

A-2: 1: 1 weight ratio mixture of the copolymer of Chemical Formula 4 and the copolymer of Chemical Formula 5-1

[Formula 5-1]

(Copolymer of Formula 5-1

,

(1: 1 molar ratio) condensation reaction product (weight average molecular weight: 3300))

A-3:

,

,

(1: 0.8: 0.4 molar ratio) of the copolymer of the formula (4) produced by the condensation reaction (weight average molecular weight: 2600, n = 4)

A-4:

,

,

(1: 0.9: 0.2 molar ratio) of the copolymer of the formula (4) produced by the condensation reaction (weight average molecular weight: 4100, n = 9)

A'-1:

,

Copolymer produced by condensation reaction of (1: 1 molar ratio) (weight average molecular weight: 3300)

Experimental Example

Through the evaluation method described below, the etch resistance, heat resistance and solubility of the hard mask layer or hard mask formed from the compositions of Table 1 were evaluated. The evaluation results are shown in Table 2 below.

(1) etching resistance evaluation

The compositions according to Examples and Comparative Examples were each coated by spin-coating on a silicon wafer and baked at 200 ° C. for 60 seconds to form a hardmask layer having a thickness of 1500 μs. The ArF photoresist was coated on each of the formed hard mask layers, baked at 110 ° C. for 60 seconds, and then exposed using ASML (XT: 1450G, NA 0.93) exposure equipment, respectively, followed by TMAH (2.38 wt% aqueous solution). It was developed to obtain a line-and-space pattern of 60 nm.

The photoresist pattern was further cured at 110 ° C. for 60 seconds, dry etching was performed on the hard mask layer for 20 seconds using the photoresist pattern and CHF ₃ / CF ₄ mixed gas, and the cross section was FE-SEM. Each was observed and the etching rate was measured to determine the etching resistance to the halogen plasma.

<Anti-etching determination>

(Double-circle): etching rate less than 10 microsecond / sec

○: etching rate 10 kPa / sec or more but less than 11 kPa / sec

△: etching rate 11 kPa / sec or more and less than 12 kPa / sec

X: etching rate 12 kPa / sec or more

(2) heat resistance evaluation

The compositions of the examples and comparative examples were vacuum dried to remove the solvent, and a portion of the sample was taken and the mass loss rate was measured while heating up to 800 ° C. using TGA (thermogravimetric analysis) under nitrogen.

Mass loss rate = {(initial mass-mass at 800 ° C) / initial mass} x 100%

<Heat resistance judgment>

◎: mass loss rate less than 10%

○: mass loss rate 10% or more to less than 15%

△: mass loss rate of 15% or more but less than 25%

×: 25% or more mass loss rate

(3) solubility

After stirring the compositions of Examples and Comparative Examples for 1 hour at 50 ℃, 1) to confirm the dissolved state of the copolymer in a heated state (50 ℃), and cooled to room temperature, 2) normal temperature (25 ℃) The dissolution state of the copolymer in was confirmed, and further stirred at room temperature for 6 hours, and 3) the dissolution state of the copolymer in the room temperature standing state (25 degreeC) was again confirmed, and the solubility was measured.

Solubility determination

(Double-circle): Undissolved polymer is not visually recognized in the state of normal temperature standing.

(Circle): Undissolved polymer is not visually recognized at room temperature, but a small amount of undissolved polymer is visually confirmed at room temperature.

(Triangle | delta): The polymer undissolved in a warm state is not visually recognized, but the polymer dissolves in a normal temperature state and visually confirmed.

X: Undissolved in a heated state, and a small amount of polymers are visually confirmed.

Referring to Table 2, the hard mask including polybenzoxazole according to the embodiments of the present invention exhibited significantly improved heat resistance while maintaining etch resistance. In the case of Comparative Example 1 containing only a copolymer of aromatic compounds, the heat resistance and solubility were drastically reduced. In the case of Example 4, the solubility slightly decreased as the weight average molecular weight increased.

Claims (9)

1. Copolymers containing polybenzoxazole or a precursor thereof; And

   A composition for a hard mask comprising a solvent.
2. The composition of claim 1, wherein the carbon content of the polybenzoxazole is 75% or more.
3. The composition of claim 2, wherein the polybenzoxazole comprises a reactant of a first precursor monomer of Formula 1 and a second precursor monomer of Formula 2 below:

   [Formula 1]

   

   [Formula 2]

   

   (In Formula 2, X is a halogen or -OR group, R is an aliphatic hydrocarbon group of 1 to 12 carbon atoms or an aromatic hydrocarbon group of 6 to 12 carbon atoms)
4. The composition of claim 3, wherein the polybenzoxazole is a reactant of the first precursor monomer, the second precursor monomer, and an end capping agent of Formula 3 below: 4.

   [Formula 3]

   

   (In Formula 3, X is a halogen or -OR group, and R is an aliphatic hydrocarbon group having 1 to 12 carbon atoms or an aromatic hydrocarbon group having 6 to 12 carbon atoms).
5. The composition of claim 2, wherein the polybenzoxazole comprises a structure represented by the following Chemical Formula 4:

   [Formula 4]

   

   (In Formula 4, n is an integer of 1-100.).
6. The composition for hard mask according to claim 2, wherein the polybenzoxazole has a weight average molecular weight of 900 to 5,000.
7. The composition of claim 1, wherein the copolymer further comprises a copolymer of aromatic compounds including a structural unit represented by Formula 5 below:

   [Formula 5]

   

   (In Formula 5, Ar1 is a C10-C30 arylene group which has a multiple aromatic ring structure, and Ar2 is a C10-C30 aryl group which has a multiple aromatic ring structure.).
8. The composition of claim 1, comprising 5 to 30 wt% of the copolymer and 70 to 95 wt% of the solvent in a total weight of the composition.
9. Forming an etching target layer on the substrate;

   Forming a hard mask layer on the etching target layer by applying the composition for hard mask according to any one of claims 1 to 8;

   Forming a photoresist pattern on the hard mask film;

   Etching the hard mask layer using the photoresist pattern to form a hard mask pattern; And

    Etching the etching target layer by using the hard mask pattern.

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