JP3492046B2 - Target material for forming antireflection film and pattern forming method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-based target material for an antireflection film, which is capable of forming a high-performance antireflection layer in a photoresist process in a semiconductor device manufacturing process such as IC and LSI. The present invention relates to a method for forming a resist pattern of a semiconductor device using the target material.

The photoresist process is a method of forming a single-layer or multiple-layer resist layer on a semiconductor wafer and then transferring a pattern to obtain a resist pattern having the same shape as the mask surface. Currently, the photolithography method is generally used. Has been applied. However, when a fine pattern is formed in the photoresist process, the unevenness of the semiconductor substrate causes the thickness of the photoresist layer to change at the step portion, so that the dimensional accuracy of the resist pattern is impaired due to the influence of optical interference. Easy to invite.

Recently, with the progress of integration and densification of semiconductor integrated circuits, finer and more accurate resist patterns are required. To meet this demand, the resist film is flattened. However, if the reflectance of the substrate is high, halation may occur and it may be difficult to form a highly accurate pattern. In order to accurately form a pattern on the surface of the substrate having such a high reflectance, conventionally, means for forming a light reflection preventing layer on the inner and outer surfaces of the photoresist layer has been adopted.

[0004]

2. Description of the Related Art Conventionally, as a means for forming a light reflection preventing layer, a method of depositing an inorganic coating film on a substrate or a method of applying an organic coating film is known, and W and Ti are used as the inorganic coating material. , TiW, TiN, TiON, α-S
i, etc. are used. However, the antireflection film made of these inorganic materials has a limit in suppressing the influence of the reflected light from the base during exposure.

Japanese Unexamined Patent Publication (Kokai) No. 6-69123 discloses an antireflection film having a lower reflectance than the conventional inorganic coating material and a resist pattern forming method using the same, which is selected from carbon and materials containing carbon. An antireflection film composed of at least one material selected from the above, and a resist pattern forming method using the antireflection film when forming a resist pattern by a photolithography technique, at least one selected from the above carbon and a material containing carbon. A method using a film made of a kind of material has been proposed. And as a material containing carbon,
Carbides such as SiC are exemplified.

[0006]

However, Japanese Patent Application Laid-Open No. 6-69123 describes that a carbon target having a specific resistance of 0.1 Ω-cm or less was used as a carbon target for forming an antireflection film by sputtering. Other than that, the physical properties of the carbon target relating to the performance of the antireflection film have not been clarified. In particular, if particles are generated in the formed carbon film, it will hinder precise circuit formation. Therefore, it is necessary to form a film so that the number of particles of 0.2 μm or less is 50 or less. Is not recognized.

The present inventor, when forming a film on the surface of a resist layer by a photoresist process, has an excellent antireflection property, a uniform film thickness necessary for forming a precise circuit pattern, and suppression of particle generation. As a result of repeated multifaceted studies on the carbon-based target material that brings about the above, it was clarified that the glassy carbon material having the specific material physical properties exhibits an excellent effect.

The present invention has been developed on the basis of the above-mentioned findings, and a problem to be solved by the present invention is to provide excellent antireflection in a photoresist process, and to reduce the variation in film thickness and the generation of particles in a carbon-based reflection. It is an object of the present invention to provide a target material for forming a prevention film and a resist pattern forming method for a semiconductor device using the target material.

[0009]

A target material for forming an antireflection film according to the present invention for solving the above-mentioned problems has a crystallite size Lc (002) of 1.5 to 3.0 nm and a graphite hexagonal shape. The average lattice spacing d _{002 of the} mesh surface layer is 0.345 to 0.36.
The structural feature is that it is made of a glassy carbon plate having a crystallinity of 0 nm.

In addition to these crystal properties, a glassy carbon plate having material properties such that the maximum diameter of the internal pores is 5 μm or less and the bulk density is 1.48 g / cm ³ or more, and / or the total ash content is 10 ppm or less in purity. The glassy carbon plate having the characteristics exhibits a more excellent effect as the target material for the antireflection film.

Further, in the pattern forming method according to the present invention, the above antireflection film target material is sputtered to form a light antireflection layer on a photoresist layer of a semiconductor substrate,
Then, after exposing through a mask, an etching process is performed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION It is a prerequisite that the target material for forming an antireflection film of the present invention comprises a glassy carbon plate. Glassy carbon is a carbonaceous substance obtained by firing and carbonizing a thermosetting resin and having a structure structure different from that of ordinary graphite materials and carbon materials, and has a macroscopically hard structure with no pores and high strength. It has characteristics such as low chemical reactivity, gas impermeability, self-lubricating property, fastness, and low impurities.

In the present invention, the crystallite size Lc (002) of the glassy carbon material is 1.5 to 3.0 nm, and the average lattice spacing d ₀₀₂ of the graphite hexagonal mesh plane layer is 0.345 to.
Plates with a crystallinity of 0.360 nm are selected.
The crystallite size Lc (002) and the average lattice spacing d ₀₀₂ of the graphite hexagonal network plane layer are indices showing the crystallinity of graphitization determined by X-ray diffraction, and the above-mentioned specific range indicates that the graphite crystallization is Corresponds to a moderately developed structure. The carbon coating film formed on the resist layer surface of the substrate by sputtering with the crystalline glassy carbon plate as a target exhibits an excellent anti-reflection function, and at the same time, the film thickness is uniform and the generation of particles is extremely small.

However, the crystallite size Lc (002) is 3.0.
In the glassy carbon material having a graphitization property that exceeds 1.0 nm and the average lattice spacing d _{002 of} the graphite hexagonal mesh plane layer is less than 0.345 nm, particles of an abnormal structure are mixed in the structure and particles are generated. However, the crystallite size Lc (002) is less than 1.5 nm and the average lattice spacing d ₀₀₂ of the graphite hexagonal mesh plane layer is 0.3.
Amorphous glassy carbon material with a thickness of more than 60 nm has a reduced ability to prevent light reflection and causes local consumption at the sputtering stage, which causes fluctuations in the carbon film thickness and pinholes on the film surface. Defects occur. Further, even if the glassy carbon plate is out of the range of any of these requirements, the light reflection preventing ability is deteriorated or the formed film thickness becomes nonuniform.

In addition to the above crystallinity, the maximum diameter of the pores contained in the material structure of the glassy carbon plate constituting the target material is 5 μm or less and the bulk density is 1.48 g / cm.
It is preferable to have material characteristics of ³ or more. When a glassy carbon plate with a coarse structure having a maximum internal pore diameter of more than 5 μm and a bulk density of less than 1.48 g / cm ³ is used as the target material, the particles in the carbon film formed will increase and the number of particles will increase. To do. Further, preferably, the glassy carbon plate constituting the target material has a purity of 10 ppm or less in terms of total ash content, which is effective in suppressing particle generation.

The target material for forming an antireflection film of the present invention comprising a glassy carbon plate having the above-mentioned physical properties can be manufactured as follows. First, in order to increase the density and purity of the material, a phenol-based, furan-based, or polyimide-based resin having a residual carbon ratio of at least 40% or a thermosetting resin obtained by blending them is used as a raw material. . Since these raw material resins are usually in the form of powder or liquid, they are molded into a predetermined plate shape by using an optimum molding means such as molding or casting depending on the form. The molded body continues to be 100 in the atmosphere.
Curing treatment is performed at a temperature of 180 ° C. The firing carbonization process is
The cured resin molding is packed in a graphite crucible or sandwiched between graphite plates and packed in an electric furnace or a lead hammer furnace kept in an inert atmosphere of nitrogen, argon, etc.
It is performed by heating to 1000 ° C. Further, the carbonized fired body is placed in a vacuum furnace capable of atmosphere replacement, and heated to a temperature range up to 2000 ° C. while flowing a halogen-based purified gas to control the crystal properties and perform a purification treatment. The crystal properties can be adjusted by the heating temperature and the holding time.

In the method for forming a pattern of a semiconductor device according to the present invention, a glassy carbon plate having the above-mentioned specific physical properties is used as a target material for an antireflection film, and a light antireflection layer made of a carbon thin film is formed on a photoresist layer by sputtering. The resist layer is formed through exposure, the resist layer is exposed through a mask, and then a predetermined etching process is performed.

As the film forming means of the antireflection film, for example, plasma CVD method, photo CVD method, thermal CVD method, glow discharge vapor deposition method and the like are known. For the purpose of the present invention, a CD is used.
Sputtering such as magnetron sputtering or RF sputtering is preferably applied. The antireflection film is formed on the inner and outer surfaces of the resist layer of the semiconductor substrate, but may be formed by laminating an insulating film, a wiring forming thin film, or the like on the substrate. The formation of the resist pattern is performed by a known means such as a photolithography method. That is,
A resist layer, a light reflection preventing layer, and other necessary thin films are formed on the surface of the semiconductor substrate, and a photomask is arranged on the surface of the layer and exposed.
Then, the resist layer is developed and then subjected to a predetermined etching treatment to remove the exposed portion to form a desired pattern. At this time, since the antireflection layer formed by the present invention has a high light reflectivity, a phenomenon such as halation does not occur, and a precise pattern can always be formed even in a fine photoresist process.

Since the antireflection film of the present invention is a carbon film, it can be easily removed by heating in an oxygen-containing atmosphere. Therefore, the antireflection layer can be removed at the same time in the oxygen ashing process for removing the resist pattern.

[0020]

【Example】

Examples 1 to 6 and Comparative Examples 1 to 4 (1) Production of Target Material for Forming Antireflection Film Using phenol and formalin purified by vacuum distillation as raw materials, addition condensation reaction is carried out according to a conventional method to obtain a phenol resin initial condensate (liquid). Resin) was prepared. The phenol resin initial condensate was poured into a polypropylene vat, placed in a vacuum desiccator, deaerated under a reduced pressure of 10 Torr or less, and then transferred to an electric oven to be heat-cured. The curing temperature was initially set to 100 ° C, then 18
The temperature was raised to 0 ° C. to complete the curing. In this molding step, the degree of pressure reduction during degassing and the degassing time were controlled to adjust the bulk density and the intrinsic pore state of the glassy carbon material finally obtained.

The resin plate obtained in the above-mentioned molding process is a high-purity graphite plate containing less than 5 ppm of impurities (manufactured by Tokai Carbon Co., Ltd.).
G347SS), and set it in a heating furnace equipped with a heating element also made of high-purity graphite. While maintaining the inside of this heating furnace in a high-purity argon gas atmosphere containing less than 10 ppm of impurities, it was calcined and carbonized at a temperature of 1000 ° C. to be converted into glassy carbon. The glassy carbon plate obtained is further added with 15
The temperature was maintained at a high temperature of 00 ° C. or higher, chlorine gas was circulated to perform high-purity treatment, and the degree of graphitization was adjusted. The degree of graphitization was adjusted by combining the maximum temperature of the treatment and the holding time.

The glassy carbon plates having different properties produced in the above manner were used in a clean room to have a diameter of 300.
mm into a disk shape having a thickness of 6 mm to obtain a target material for forming an antireflection film. Table 1 shows the graphitization degree, bulk density, pore diameter, and total ash content of each target material for forming an antireflection film. The target material shown as Comparative Example 5 is a graphite plate.

[0023]

[Table 1]

(2) Formation of Antireflection Film Each target material of the glassy carbon plate having the property shown in Table 1 was installed as a cathode in a DC magnetron sputtering device, and a thin film of Al-Si-Cu alloy was previously prepared as a counter electrode. The semiconductor substrate on which was formed was set. Set the atmosphere in the device to 5
The pressure of argon was adjusted to mTorr, and a carbon coating having a film thickness of 15 to 30 nm was formed under the sputtering conditions of DC 1.0 kw.

The properties of the formed carbon film and the product yield are shown in Table 2. In Table 2, the reflectance is i-line (wavelength
(Light of 365 nm), the number of particles of the carbon film is the number per 1 ft ³ measured by a light scattering type particle counter, and the product yield is the product pass rate for 100 tests.

[0026]

[Table 2] [Table Note] PH of the appearance of the film is an abbreviation for pinhole.

As is clear from a comparison of Tables 1 and 2, the carbon coating formed using the target material for forming an antireflection coating according to the embodiment of the present invention is compared with the comparative example in which the material property requirements of the present invention are not satisfied. It is recognized that the quality of the carbon film is excellent and the product yield is improved. However, in Example 6 in which the total ash content of the glassy carbon plate exceeded 10 ppm, some pinholes were recognized in the carbon coating film, and the particle size and the number of particles tended to be inferior.

(3) Formation of Pattern A resist layer was formed on the upper surface of the carbon film according to the example, and a photomask was overlaid to expose i-line, and then the resist layer was developed. Each of the obtained resist patterns had a stable form with few notches. Then, Al-Si- which is not covered with the resist pattern
When the Cu alloy film was removed by etching, an extremely accurate wiring pattern was formed. O resist pattern
Although it was removed by ₂ ashing, the carbon film was removed at the same time as the resist part in this process.

[0029]

As described above, according to the present invention, by the photoresist process, excellent light reflection preventing performance is exhibited on the resist layer surface, and the uniform film thickness required for forming a precise circuit pattern and generation of particles are small. It is possible to provide a target material for forming an antireflection film, which is composed of a glassy carbon plate on which a high quality carbon film can be formed. Further, according to the pattern forming method of the present invention, it becomes possible to form a fine resist pattern on a semiconductor substrate with high accuracy.

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Claims (4)

(57) [Claims] 1. The crystallite size Lc (002) is 1.5 to 3.
At 0 nm, the average lattice spacing d ₀₀₂ of the graphite hexagonal mesh plane layer is 0.
A target material for an antireflection film, comprising a glassy carbon plate having crystallinity of 345 to 0.360 nm. 2. The target material for an antireflection film according to claim 1, wherein the intrinsic pores have a maximum diameter of 5 μm or less and a bulk density of 1.48 g / cm ³ or more. 3. The target material for an antireflection film according to claim 1, which has a purity characteristic that the total ash content is 10 ppm or less. 4. A target material for an antireflection film according to claim 1 is sputtered to form a light antireflection layer on a photoresist layer of a semiconductor substrate, and then the resist layer is exposed through a mask and then subjected to etching treatment. A pattern forming method characterized by the above.