JP2001288382A - Carbon black for anti-reflective coating - Google Patents

Abstract

(57) [Problem] To provide a carbon black suitable for forming an antireflection film used in a photoresist process. A crystallite size Lc (002) is more than 2.0 nm, the average lattice spacing d ₀₀₂ of the graphite hexagonal plane layer is 0.34
A carbon black for forming an antireflection film, characterized in that the carbon black has a crystalline property of 0 to 0.350 nm and a particle aggregating property of a Stokes mode diameter Dst of 20 to 50 nm of the aggregate and a content of each metal element of 50 ppb or less. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbon black suitable for forming an antireflection film in a photoresist process in a process of manufacturing a semiconductor device such as an IC or LSI.

[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 insulating film and the conductive film are etched to transfer the wiring pattern.

In this case, when light is radiated and exposed by 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 resist pattern shape accuracy is reduced. , And a precise pattern cannot be formed. Therefore, a method of reducing the reflected light from the substrate by forming an anti-reflection film on the substrate has been adopted. The anti-reflection film is usually formed below the photoresist film (over the conductive film for pattern formation). Have been.

[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]

On the other hand, as the degree of integration and density of semiconductor integrated circuits increase, the formation of finer and more accurate resist patterns is required, and the light absorption capacity is reduced. The need for an antireflection film that is high and has an excellent antireflection function is increasing.

Accordingly, the present applicant has focused on carbon black having a high light absorbing ability, and has studied the properties of the carbon black, particularly the relationship between the particle aggregating properties and the light absorbing ability. Developed and proposed an anti-reflection film (Japanese Patent Application No. 2000-013857) characterized in that carbon black having a particle cohesion property having a Dst of 20 to 50 nm and a half value width ΔDst of 40 nm or less is dispersed in a resin. .

As a result of continuous research on the properties of carbon black suitable for forming an anti-reflection film, the applicant of the present invention has found that the graphite crystallinity of carbon black has an effect on the light absorption ability, and the graphite crystallized structure has developed. It has been found that the obtained carbon black has a high light absorbing ability and exhibits an excellent antireflection function. Furthermore, it was confirmed that, when carbon black was subjected to high-temperature heat treatment to increase the crystallinity of graphite, metal impurities were particularly efficiently removed by simultaneously performing the purification treatment.

The present invention has been developed based on the above findings, and an object of the present invention is to provide carbon black suitable for forming an antireflection film used in a photoresist process.

[0010]

According to the present invention, there is provided a carbon black for forming an antireflection film according to the present invention, which has a crystallite size Lc (002) of at least 2.0 nm and a graphite hexagonal mesh layer. Average lattice spacing d ₀₀₂ is 0.340 to 0.35
It is characterized in that it has a crystal property of 0 nm and a particle cohesion property in which the Stokes mode diameter Dst of the aggregate is 20 to 50 nm, and the content of each metal element is 50 ppb or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Carbon black is composed of several to several tens of basic fine particles which are fused and bonded in a complex manner to form an aggregate (aggregate). The layer planes are oriented parallel to each other, and the layer planes overlap several layers to form crystallites, and the crystallites have a pseudo-graphite structure.

The carbon black for forming an antireflection film according to the present invention is characterized in that the graphite crystallized structure of the crystallite has a highly developed crystal property, and specifically, the crystallite size Lc (002) is at least 2.0 nm, and the average lattice spacing d _{002 of the} hexagonal graphite layer is 0.340 to 0.350 nm.

That is, the graphite crystallinity of carbon black is low, the value of the crystallite size Lc (002) is less than 2.0 nm, and the average lattice spacing d _{002 of the} hexagonal graphite layer is 0.3.
If it exceeds 50 nm, the light absorption capacity is low, so that the amount of reflected light is large, and it becomes impossible to form an excellent antireflection film. Further, the etching rate is increased, and the antireflection film is removed at the same time as the photoresist layer during the etching process, which makes it difficult to form a precise wiring pattern.

On the other hand, the average lattice spacing d of the hexagonal mesh layer of graphite
_{When the} degree of graphite crystallinity such that ₀₀₂ is less than 0.340 nm becomes high, a trace amount of graphite particles of abnormal structure is easily mixed in the structure, particles are dropped from the antireflection film, and the formation of a fine wiring pattern is hindered. The Rukoto.

These crystal properties are values measured by X-ray diffraction. Carbon black is heat-treated at a high temperature in an inert atmosphere to grow crystals in the particles to adjust the crystallinity to a predetermined degree of graphite. be able to. In this case, metal impurities in the carbon black can be removed by performing high-temperature heat treatment while flowing a purified halogen-based gas in an inert gas, and this high-purification treatment causes a problem as a contamination source particularly in semiconductor applications. Metal element can be reduced. That is, the content of each metal element is highly purified to a level of 50 ppb or less.

Further, the carbon black for forming an antireflection film of the present invention is characterized in that, in addition to the above-mentioned crystalline properties, the aggregate has a particle aggregation property in which the Stokes mode diameter Dst of the aggregate is 20 to 50 nm.

The antireflection film is formed by applying a dispersion of carbon black, a resin and a solvent onto a substrate and baking the dispersion. If the aggregate becomes large and the Stokes mode diameter Dst exceeds 50 nm, the antireflection film is formed. This is because the dispersion state of the carbon black in the dispersion becomes coarse, and the denseness and smoothness of the formed antireflection film are impaired. On the other hand, when the value of the Stokes mode diameter Dst is less than 20 nm, the light reflection function is reduced. The Stokes mode diameter Dst of the aggregate is measured by a centrifugal sedimentation method and refers to the Stokes equivalent diameter having the highest frequency in the Stokes equivalent diameter distribution.

The carbon black for forming an antireflection film of the present invention is prepared by dispersing it in a resin and a solvent to prepare a dispersion. The dispersion is applied onto a substrate and baked to form an antireflection film. It is preferable that the coating liquid for forming the antireflection film is blended and prepared in an amount ratio of 1 to 20% by weight of carbon black, 2 to 10% by weight of a resin, and the balance being a solvent.

If the amount ratio of carbon black is less than 1% by weight, light reflection cannot be sufficiently prevented due to low light absorbing ability, and the antireflection function becomes insufficient. However, 2
If it exceeds 0 wt%, it will be difficult to disperse the resin in a stable and uniform state in the resin, and the antireflection function will be reduced. If the amount of the resin is less than 2% by weight, the formed antioxidant film is brittle, and it is difficult to firmly fix it on the substrate. On the other hand, if it exceeds 10 wt%, the carbon black content becomes relatively small, so that the light absorption capacity is reduced, and the antireflection function is reduced.

The resin is not particularly limited as long as it has high purity and does not hinder the dispersion of carbon black in the solvent. For example, phenol resin, epoxy resin, polyacrylamide resin, acrylic resin, polyimide resin, polyvinyl alcohol And polyvinylpyrrolidone.

The solvent used has a boiling point of 100 ° C. to 220 ° C.
C. are preferably used. Examples of the polar solvent include water, dimethylformamide, dimethylsulfoxide, dimethylacetamide, N-methyl-2-pyrrolidinone, and the like, and the nonpolar solvent includes cyclohexanone, ethyl lactate, and the like. .

The carbon black for an antireflection film of the present invention is mixed with a resin in a solvent at a predetermined ratio and uniformly dispersed to prepare a dispersion for forming an antireflection film. It is necessary to disperse uniformly in the solvent and to suppress aggregation in the dispersion. However, carbon black in which the graphite crystallized structure of crystallites is developed has an extremely low dispersibility in a solvent because the surface is inactive. Therefore, it is preferable to improve the dispersibility by adding a surfactant. In addition, it is necessary to prevent the presence of metal in the anti-reflection film as much as possible.
As the surfactant, a special polycarboxylic acid-type polymer surfactant containing no metal, a polyoxyethylene derivative, a fluorine-based surfactant, a basic polymer-based dispersant, or the like is used.

The dispersion for forming an antireflection film prepared using the carbon black for an antireflection film of the present invention is applied onto a predetermined surface of a substrate by, for example, a spin coater,
A heat treatment removes the solvent by volatilization and fixes the resin to form an antireflection film. The antireflection film is preferably formed to a thickness of about 100 to 200 nm, and in order to form a uniform and smooth reflection film, the viscosity of the dispersion is adjusted to 10 mPa · s (25 ° C.) or less. Is preferred.

[0024]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Examples 1 to 3 and Comparative Examples 1 to 3 Carbon blacks having different Stokes mode diameters Dst of the aggregates were heat-treated while flowing chlorine gas in a high-purity argon gas atmosphere. Then, the degree of graphite crystallinity was adjusted and high-purification treatment was performed to prepare a carbon black sample. However, in Comparative Example 1, the chlorine gas was not circulated and the high-purification treatment was not performed. 5% by weight of these carbon black samples, 10% by weight of phenol resin, and 8% by weight of cyclohexanone (solvent).
After mixing at a weight ratio of 5 wt%, further adding a basic polymer type surfactant, stirring, mixing and dispersing, then centrifuging.
(33.33 s ⁻¹ , 10 minutes) to remove settled particles to prepare a dispersion coating solution for forming an antireflection film.

The coating liquid for forming an antireflection film is applied on a silicon substrate using a spin coater (rotational speed of the spin coater is 16.67 s ^-1 ) and baked at 190 ° C. for 60 seconds to form an antireflection film. did. About the formed antireflection film, the film thickness, the film specific gravity, the etching rate, and the extinction coefficient were measured by the following methods. The obtained results are shown in Table 1 together with the properties of carbon black such as crystal properties and particle aggregation properties. The content of metal elements in the coating solution for forming an anti-reflection film was measured by a flameless atomic absorption spectrophotometer (Z-9000, manufactured by Hitachi, Ltd.). The results are shown in Table 2. Film thickness, specific gravity of the film: cut by a diamond cutter, the cross section was observed with an electron microscope to measure the film thickness, and the specific gravity of the film was determined by measuring the weight of the coating film and calculating the volume from the cross-sectional area of the film. Etching rate: Etching was performed for 30 seconds using CF ₄ / O ₂ / Ar as an etching gas, the film thickness before and after etching was measured with an electron microscope, and the etching rate was calculated from the change in film thickness. 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.

[0027]

[Table 1]

[0028]

[Table 2]

According to Tables 1 and 2, the anti-reflection films shown in Examples 1 to 3 have a desired thickness by controlling the coating thickness at the time of spin coating. In addition, as a result of observing the surface and the cross section of the antireflection film with an electron microscope, the dispersion of the film thickness was small, the smoothness of the cross section was secured, and the gap between the carbon black particles was extremely small, and a dense coating film was formed. Was. Further, the etching rate was lower than that of the photoresist layer, and the antireflection film was not removed together with the photoresist layer during etching. In contrast, in the case of the antireflection film of the comparative example, the coating rate could not be controlled or a dense coating film was not formed, so that the etching rate was equal to or higher than that of the photoresist layer, and the It was removed at the same time as the photoresist layer.

[0030]

As described above, the carbon black for forming an antireflection film according to the present invention has a crystallinity Lc (002) of 2.0 nm or more and an average lattice plane of a hexagonal graphite layer of graphite. By setting the distance d ₀₀₂ in the range of 0.340 to 0.350 nm and setting the particle aggregating property in the range of the Stokes mode diameter Dst of the aggregate in the range of 20 to 50 nm, the carbon black of the present invention can be used as a resin and a solvent. An anti-reflective coating formed by applying a coating solution prepared by dispersing on a substrate and baking it has a high absorption capacity for irradiation light such as ultraviolet rays, and effectively suppresses reflected light from the substrate surface during exposure. Since the etching rate is low and the etching rate is low, it is possible to form a precise resist pattern with small dimensional errors. Furthermore, the metal element content is extremely low, and IC, L
It is possible to provide carbon black suitable for forming an antireflection film in a photoresist process in a semiconductor device manufacturing process such as SI.

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Claims (1)

[Claims] 1. The crystallite size Lc (002) is at least 2.0 nm, and the average lattice spacing d _{002 of} the graphite hexagonal mesh layer is 0.34.
A carbon black for forming an antireflection film, characterized in that the carbon black has a crystalline property of 0 to 0.350 nm and a particle aggregating property of a Stokes mode diameter Dst of 20 to 50 nm of the aggregate and a content of each metal element of 50 ppb or less. .