JP2001209185A - Antireflection film and coating liquid for antireflection film formation - Google Patents

Abstract

(57) Abstract: An anti-reflection film suitably used in a photoresist process having a high light absorption capacity and a low reflectance.
Also, to provide an antireflection film-forming coating liquid capable of easily forming the antireflection film. SOLUTION: Stokes mode diameter Dst of the aggregate
Is an antireflection film, characterized in that carbon black having a particle aggregation property of 20 to 50 nm and the same half width ΔDst is 40 nm or less is dispersed in a resin, preferably a value of an average particle size Dupa50% of agglomerate Is 20-150 nm,
The value of the maximum particle size Dupa99% is 300 nm or less. The coating liquid for forming an anti-reflection film contains 1 to 20% by weight of carbon black having the particle aggregation property and 2 to 10% by weight of a resin.
%, The balance being the composition of the solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film used in a photoresist process in a process of manufacturing semiconductor devices such as ICs and LSIs, and an antireflection film capable of forming the antireflection film simply and inexpensively. It relates to a coating liquid for forming.

[0002]

2. Description of the Related Art In a photoresist process, an insulating film, a conductive film for forming a pattern, a photoresist film, and the like are formed in this order on a semiconductor substrate, exposed to ultraviolet rays, and developed to form a resist pattern. Next, the conductive film is etched to transfer the wiring pattern.

In this case, when light is irradiated and irradiated with ultraviolet light, if light scattering or interference occurs due to light reflected by the substrate, an error occurs in the exposed portion of the photoresist film, and the shape accuracy of the resist pattern is reduced. It will be. Therefore,
A method has been adopted in which an antireflection film is formed on a substrate having high reflectivity to reduce light reflected from the substrate, and the antireflection film is usually formed under a photoresist film (over a conductive film for pattern formation). ) Is formed.

[0004] Conventionally, W, Ti, Ti
Although W, TiN, α-Si and the like are used, these materials have a limit in reducing the influence of the light reflected from the substrate, and therefore, JP-A-6-69123 discloses these materials. As an antireflection film exhibiting a lower reflectance than that and a resist pattern forming method using the same, an antireflection film made of at least one material selected from carbon and a material containing carbon, and a resist formed by photolithography technology As a method of forming a resist pattern using an antireflection film when forming a pattern, there has been proposed a method of using a film made of at least one material selected from the above-mentioned materials containing carbon and carbon. As a material containing carbon, for example, a carbide such as SiC is exemplified.

Japanese Patent Application Laid-Open No. Hei 8-241858 discloses an organic resin in which carbon particles are dispersed.
An antireflection film made of a semiconductor having an absorption coefficient of greater than 0.23 and a refractive index of 1.6 to 1.8 under a light having a wavelength of 250 nm, and an antireflection film made of an organic resin in which carbon particles are dispersed. A semiconductor manufacturing method has been proposed in which a photoresist film is formed on an oxidized surface of a substrate, a photoresist film is formed on an antireflection film, and the substrate is selectively exposed to ultraviolet light. However, there is no specific disclosure of carbon particles except that the size is preferably less than 100 angstroms (10 nm).

[0006]

In recent years, as the degree of integration and density of semiconductor integrated circuits has increased, it has become necessary to form finer and more accurate resist patterns, and the light absorption capability has been high. The need for an antireflection film having an excellent antireflection function is increasing.

Accordingly, the present inventors have focused on carbon black having a high light absorbing ability, and have conducted research on the particle properties, particularly the relationship between the particle aggregating properties and the light absorbing ability.
By dispersing carbon black with specific particle aggregation properties in resin to form an anti-reflection film, reflection from the substrate surface during exposure is effectively suppressed, and it is possible to form a resist pattern with fine and small dimensional errors. I found something.

That is, the present invention has been developed on the basis of the above findings, and has as its object to provide an antireflection film having a high absorptivity for irradiation light such as ultraviolet rays and a low reflectance.
It is another object of the present invention to provide a coating liquid for forming an anti-reflection film which can be formed on a substrate at a low cost by a simple method at a low cost.

[0009]

According to a first aspect of the present invention, there is provided an antireflection film having an aggregate having a Stokes mode diameter Dst of 20 to 50 nm and a half width ΔDst of 40 nm or less. A structural feature is that carbon black having particle aggregation properties is dispersed in a resin.

The antireflection film according to claim 2 of the present invention is the antireflection film according to claim 1, wherein the value of the average particle diameter Dupa 50% of the agglomerate of carbon black is 20 to 150.
It is characterized in that it has a particle aggregation property in which the value of nm and the maximum particle size Dupa 99% are 300 nm or less.

The coating liquid for forming an antireflection film according to the present invention comprises 1 to 20% by weight of carbon black having the particle aggregation property according to claim 1 or 2, 2 to 10% by weight of a resin, and the remainder of a solvent. Is a structural feature.

However, in the above structure, Dst is the Stokes equivalent diameter of the maximum frequency in the Stokes equivalent diameter distribution of the carbon black aggregate measured by the centrifugal sedimentation method, ΔDst is the half width of the Stokes equivalent diameter distribution, and Dupa5
0% is the value of the 50% cumulative frequency in the cumulative frequency distribution curve of the agglomerate particle size created from the frequency modulation degree of the scattered light by irradiating the aqueous dispersion of carbon black with laser light,
Dupa99% indicates the value of the 99% cumulative frequency in the distribution curve.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The antireflection film of the present invention has a structure in which carbon black is dispersed in a resin, and the carbon black is present in the resin in a uniform dispersion state. Carbon black is black and has high light absorption,
Although the present invention exhibits physical properties with low reflectance, the present invention aims at improving the antireflection function and maintaining a uniform and stable dispersion state in the resin by specifying the particle aggregation properties of carbon black.

That is, the carbon black used in the antireflection film according to the first aspect of the present invention has a Stokes mode diameter Dst of the aggregate of 20 to 20 as an aggregate form of particles.
It is characterized by having a particle aggregation property of 50 nm and a half width ΔDst of Stokes mode diameter of 40 nm or less.

In the formation process of carbon black particles, in the process of their formation, fine basic fine particles are firmly fused and bonded in an irregular and complex chain in a unit of several to several tens to form an aggregate (aggregate). ), And these aggregates are composed of aggregates (agglomerates) that are entangled with each other or adhere and re-aggregate.

The antireflection film according to the first aspect of the present invention is intended to improve the antireflection function by specifying the particle aggregation property of the carbon black aggregate. That is, when the aggregate becomes large, the dispersion state in the resin becomes coarse, the compactness is reduced, and the smoothness of the antireflection film is impaired. Further, when the size distribution of the aggregate becomes broad, the dispersion state of the carbon black in the resin also becomes broad, thereby impairing the smoothness of the surface of the antireflection film, and making it difficult to control the surface roughness. Therefore, in the antireflection film of the present invention, the value of the Stokes mode diameter Dst of the carbon black aggregate is set to 20 to 50 nm, and the value of the half width ΔDst of the Stokes mode diameter of the aggregate is set to 40 nm or less. Thereby, the light absorbing ability is improved and stabilized.

Further, the anti-reflection film according to claim 2 of the present invention comprises:
The average particle size Dup of the agglomerate, which is an aggregate in which aggregates are re-aggregated in the carbon black according to claim 1.
By setting the value of a50% to 20 to 150 nm and the value of the maximum agglomerate particle diameter Dupa99% to 300 nm or less, the antireflection function is further improved. That is, when the agglomerate increases, the density of the antireflection film surface decreases, the smoothness also decreases, and the antireflection function decreases, so that it is impossible to provide a stable and excellent antireflection function. Therefore, preferably, the value of the average particle size Dupa50% of the agglomerate is 20 to 150 n
m, the maximum particle size of agglomerate Dupa 99% is 300 nm
The setting is controlled as follows.

As the characteristics Dst and Dupa, values obtained by the following measuring methods are used. (1) Stokes mode diameter Dst (nm) and half width ΔDst (nm) of the aggregate: JIS K6221 (1982) 5 A dry carbon black sample containing a small amount of surfactant based on “How to prepare a dry sample” 20 A dispersion having a carbon black concentration of 0.1 kg / m ³ is prepared by mixing with a volume% aqueous solution of ethanol, and this is sufficiently dispersed with ultrasonic waves to obtain a sample. Disk Centrifuge (Joyes Lobel, UK)
Is set to 100 s ⁻¹ and 0.015 dm ^{3 of} spin solution (2% by weight glycerin aqueous solution, 25 ° C.) is added.
Inject 0.001 dm ³ of buffer solution (20% by volume ethanol aqueous solution, 25 ° C.). Then, after adding 0.0005 dm ³ of the carbon black dispersion at a temperature of 25 ° C. with a syringe, centrifugal sedimentation was started, and at the same time, the recorder was operated to obtain the distribution curve shown in FIG. , The vertical axis: absorbance at a specific point changed with the centrifugal sedimentation of carbon black). Each time T is read from this distribution curve and substituted into the following equation (Equation 1) to calculate the Stokes equivalent diameter corresponding to each time.

[0019]

(Equation 1)

In Equation 1, η is the viscosity of the spin liquid (0.935
× 10^-3Pa · s), N is the disk rotation speed (100 s^-1),
r₁Is the radius of the carbon black dispersion injection point (0.0456m)
 , R _TwoIs the radius (0.0482m) to the absorbance measurement point, ρ_CBIs
Carbon black density (kg / m^Three), Ρ₁Is the density of the spin liquid
Degree (1.00178 × 10^Threekg / m^Three).

The Stokes equivalent diameter having the maximum frequency in the Stokes equivalent diameter and the absorbance distribution curve (FIG. 2) obtained in this manner is calculated as the Stokes mode diameter Dst (n) of the aggregate.
m), and the distance between two points, large and small, corresponding to half the maximum frequency, is defined as a half width ΔDst (nm).

(2) Average particle size of agglomerate Dupa 50%,
Maximum particle size Dupa99% (nm): Carbon black is dispersed in water to prepare a dispersion of 0.1 to 0.5 kg / m ³ , and a heterodyne laser Doppler type particle size distribution analyzer (Microtrac, UPA mode1) 9340), the dispersion is irradiated with laser light, and the particle size of agglomerate in the dispersion is measured from the degree of frequency modulation of the scattered light. The carbon black in the dispersion liquid undergoes Brownian motion, and the frequency of scattered light is modulated by the size of the dispersed carbon black aggregate due to the Doppler effect. Therefore, since the intensity of the Brownian motion differs depending on the size of the aggregate, the size of the aggregate in a state of being dispersed in water,
That is, the particle size of the agglomerate can be measured. A cumulative frequency distribution curve is created from the agglomerate particle size measured in this way, and the value of 50% cumulative frequency is defined as the average particle size Dupa of agglomerate 50% (nm), and the value of 99% cumulative frequency is defined as the maximum agglomerated particle size Dupa99. % (nm).

The coating liquid for forming an antireflection film of the present invention comprises a Stokes mode diameter Dst of the aggregate and a half-value width Δ.
The Dst value is characterized in that it is formed by a composition ratio of 1 to 20% by weight of carbon black having the above-mentioned particle aggregation property, 2 to 10% by weight of a resin, and the remainder being a solvent. Further, the average particle diameter of agglomerate Dupa 50%, It is more preferable that the value of the maximum particle size Dupa of 99% has the above-mentioned particle aggregation property.

When the composition ratio of carbon black in the coating liquid for forming an anti-reflection film is less than 1 wt%, the anti-reflection function becomes insufficient due to low light absorbing ability, and when it exceeds 20 wt%, the resin becomes stable and uniform. It becomes difficult to disperse them inside, which leads to a decrease in the antireflection function.

When the amount of the resin is less than 2 wt%, the formed antioxidant film is brittle, and it is difficult to firmly fix the film on the substrate. On the other hand, if it exceeds 10% by weight, the carbon black content becomes relatively small, so that the light absorption capacity is reduced, and the antireflection function is reduced. The resin is of high purity and is not particularly limited as long as it does not inhibit the dispersibility of the carbon black in the solvent.For example, a phenol resin, an epoxy resin, a polyacrylamide resin,
An acrylic resin, a polyimide resin, polyvinyl alcohol, polyvinyl pyrrolidone and the like are exemplified.

As the solvent constituting the coating solution for forming an antireflection film of the present invention, a solvent having a boiling point of about 100 ° C. to 220 ° C. is preferably used. For example, as a polar solvent, water, dimethylformamide, dimethylsulfoxide, dimethylacetamide , N-methyl-2-pyrrolidinone and the like, and examples of the nonpolar solvent include cyclohexanone and ethyl lactate.

These carbon blacks and resins are
A coating solution for forming an anti-reflection film is prepared by mixing in a solvent at a predetermined ratio and uniformly dispersing the mixture. In this case, in order to uniformly disperse the carbon black in the solvent and to suppress aggregation in the solvent, it is preferable to modify the surface of the carbon black, for example, by oxidizing the carbon black or using a coupling agent. Processing is performed.

For example, the oxidation treatment includes gas phase oxidation with ozone, nitrogen oxide, fluorine gas, etc., and liquid phase oxidation with hypochlorite, dichromate, permanganate, nitric acid, peroxodisulfate, etc. Can be done in a way. However, the antireflection film is required to have high purity, and particularly dislikes the incorporation of metal elements.Therefore, the metal elements in carbon black are ionized and removed using an acid oxidizing agent such as nitric acid or ammonium peroxodisulfate. It is a desirable method to perform an oxidation treatment by a method of generating a functional group on the surface of carbon black.

The coating solution thus prepared is applied on a predetermined surface of the substrate by, for example, a spin coater, and then subjected to a heat treatment to volatilize and remove the solvent, fix the resin, and prevent reflection on the substrate. A film is formed. In addition,
The antireflection film is preferably formed to a thickness of about 100 to 200 nm, and the viscosity of the coating solution is preferably 10 mPa · s (25 ° C.) or less in order to form a uniform film thickness.

As described above, according to the present invention, an anti-reflection film in which carbon black having a predetermined particle aggregating property is uniformly dispersed in a resin is formed. An antireflection film having a high light absorption ability and an excellent antireflection function is provided.

Hereinafter, examples of the present invention will be specifically described in comparison with comparative examples.

Examples 1 to 9 and Comparative Examples 1 to 13 (1) Preparation of coating liquid for forming antireflection film: carbon black sample; carbon black having different particle aggregating properties shown in Table 1 was oxidized to obtain a sample. did. Oxidation treatment was performed using carbon black 0.150 kg at a concentration of 0.75.
mol / dm ³ ammonium persulfate solution 0.003m ³ , reaction temperature 60 ° C, reaction time 10 hours, stirring speed 5s
^{Performed under} the condition of ^-1 . After the completion of the reaction, desalting with an ultrafiltration membrane,
After purification, the mixture was diluted with water to a carbon black concentration of 3% by weight and centrifuged. Then, after being concentrated to a carbon black concentration of 20% by weight with an ultrafiltration membrane, dried under vacuum,
This was ground to obtain a carbon black sample. Preparation of coating solution; These carbon black samples were dispersed in solvents at different weight ratios. Ethyl lactate, cyclohexanone, and water were used as solvents and mixed and dispersed in an ultrasonic bath with stirring for 5 minutes. It should be noted that a fluorine-based surfactant was used only when water was used as the solvent. Then, the resins were added at different weight ratios and mixed with a homogenizer,
Further, a coating solution for forming an antireflection film was prepared by centrifugation (33.33 s ^-1 , 10 minutes). Note that a phenol resin or an acrylic resin was used as the resin. Table 1 compares the preparation conditions of the coating solution for forming an antireflection film.

[0033]

[Table 1]

(2) Formation and evaluation of an antireflection film: These coating solutions for forming an antireflection film of 0.002 dm ³ were applied on a silicon substrate using a spin coater (spin coater rotation speed: 16.67 s ⁻¹ ). Then, the film was baked at a temperature of 190 ° C. for 60 seconds to form an antireflection film. About the formed antireflection film, the film thickness and the film density were measured by the following methods, and the extinction coefficient was measured. Film thickness, film density: Cut with a diamond cutter, the cross section was observed with an electron microscope to measure the film thickness, and the film density was determined by measuring the coating film weight and calculating the volume from the film cross-sectional area. Extinction coefficient: Shimadzu Corporation, self-recording spectrophotometer (UV
-3100PC) with a specular reflection measurement device (MPS-3100), and measured at an incident angle of 5 ° and a wavelength of 250 nm. Table 2 shows the obtained results.

[0035]

[Table 2]

In Examples 1 to 9, even if the dispersion medium and the fixing resin were changed, the thickness as an antireflection film was 200 nm or less, the film density was 0.4 × 10 ³ kg / m ³ or more, and the density was high. It has nature. Further, the extinction coefficient is 0.3 or more, and a good antireflection film is formed without any problem. In Comparative Examples 1 to 3, the dispersion medium was ethyl lactate and the fixing resin was a phenol resin. However, since the aggregate size characteristics of carbon black were out of the range, the film thickness tended to be large and the film density was low. In Comparative Examples 4, 8, and 12, since no oxidation treatment was performed, the dispersibility of carbon black in the coating film solution was reduced, and it was difficult to form a coating film. In Comparative Examples 5 to 7, cyclohexanone was used as the dispersion medium and phenol resin was used as the fixing resin.
Since the aggregate size characteristic of carbon black is out of the range, the thickness of the coating film is increased, and the film density is also reduced. In Comparative Examples 9 to 11, water was used as the dispersion medium, and a phenol resin and an acrylic resin were used as the resin. However, since the aggregate size characteristics were out of the range, the thickness of the coating film was increased,
The film density has also decreased. Comparative Example 13 shows that, when ethyl lactate was used as the dispersion medium and phenol resin was used as the fixing resin, and the amount of each added was out of the range, the film density was significantly improved, but the film thickness was too large. became.

[0037]

As described above, according to the antireflection film of the present invention, the aggregate of carbon black and the agglomerated particles of agglomerate have a structure in which carbon black having a specific particle size range is dispersed in a resin. And the like, and has a high absorption capability of irradiation light, so that light reflected from the substrate surface during exposure can be effectively suppressed. Therefore, it is possible to form a fine resist pattern with a small dimensional error. Further, according to the coating solution for forming an antireflection film of the present invention,
An antireflection film having such excellent performance can be formed on a substrate at low cost by a simple method.

[Brief description of the drawings]

FIG. 1 is a distribution curve showing changes in absorbance due to centrifugal sedimentation of carbon black and elapsed time from the addition of a carbon black dispersion at the time of measurement of Dst.

FIG. 2 is a distribution curve showing the relationship between Stokes equivalent diameter and absorbance obtained at the time of measuring Dst.

Continued on the front page (72) Inventor Takaomi Sugihara 1-3-2 Kitaaoyama, Minato-ku, Tokyo Tokai Carbon Co., Ltd. F-term (reference) 2H025 AB16 DA34 5F046 PA11

Claims (3)

[Claims] 1. Stokes mode diameter Dst of an aggregate
An antireflection film comprising a carbon black having a particle aggregation property of 20 to 50 nm and a half value width ΔDst of 40 nm or less dispersed in a resin. 2. The agglomerate of carbon black has an average particle diameter Dupa of 50% of 20 to 150 nm and a maximum particle diameter Dupa9.
The antireflection film according to claim 1, wherein the antireflection film has a particle aggregation property of 9% or less of 300 nm or less. 3. The carbon black having the particle aggregating property according to claim 1 or 2 is 1 to 20% by weight, and the resin is 2 to 10%.
A coating liquid for forming an anti-reflection film, wherein the coating liquid comprises wt% and the balance is a solvent. However, Dst is the Stokes equivalent diameter of the maximum frequency in the Stokes equivalent diameter distribution of the carbon black aggregate measured by the centrifugal sedimentation method, ΔDst is the half value width of the Stokes equivalent diameter distribution, and Dupa50% is the laser in which the aqueous carbon black dispersion is The value of the 50% cumulative frequency in the cumulative frequency distribution curve of the agglomerate particle size created from the degree of frequency modulation of the scattered light by irradiating light, and the value of Dupa 99% represent the value of the 99% cumulative frequency in the same distribution curve.