JP3098090B2 - Conductive resist - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of semiconductor devices such as LSIs and VLSIs, and more particularly to a high-sensitivity and high-resolution resist for forming fine patterns with high precision.

[0002]

2. Description of the Related Art Semiconductor integrated circuits such as ICs, LSIs and VLSIs are coated with a resist on a substrate such as a silicon wafer and exposed to a desired pattern by a stepper or the like.
It is manufactured by repeating a so-called lithography process such as development and etching.

A photomask called a reticle used in such a lithography process tends to be required to be more and more precise with the high performance and high integration of a semiconductor device. In the example of the DRAM, the dimensional deviation in a 5-fold reticle for a 1-Mbit DRAM, that is, a reticle having a size five times as large as the pattern to be exposed, has an average value ± 3σ (σ is a standard deviation). In this case, a precision of 0.15 μm is required. Similarly, a 5 × reticle for a 4 Mbit DRAM has a dimensional accuracy of 0.1 to 0.15 μm, and a 5 × reticle for a 16 Mbit DRAM has a dimensional accuracy of 0.05 to 0 μm. A dimensional accuracy of .1 μm is required.

Further, a line width of a pattern of a semiconductor device formed using these reticles is 1 Mbit DR.
1.2μm for AM and 0.8μ for 4Mbit DRAM
In the case of m and 16 Mbit DRAMs, further miniaturization of 0.6 μm is required. In order to meet such demands, various exposure methods have been actively studied, and the radiation sources used for these exposures have also been shortened to g-rays, i-rays, and excimer lasers. As the line width of semiconductor devices becomes smaller, the resolution of the projection lens becomes the limit in the light exposure method.
It is considered that the process will shift to electron beam or X-ray exposure with a shorter wavelength, and even now, reticles used for manufacturing semiconductor devices such as integrated circuits are manufactured by electron beam lithography apparatuses.

[0005]

In the electron beam lithography used for manufacturing a photomask or the like, as shown in FIG. 2A, a resist layer 22 formed on a base material 21 is exposed by an electron beam exposure apparatus. When a desired pattern is drawn by irradiating the electron beam 23, a charge-up phenomenon occurs in which the resist layer 22 made of a non-conductive material such as a synthetic resin composition is charged by the electron beam. As a result, the path of the electron beam is distorted, and the accuracy of the pattern is reduced. In addition, when a charge-up phenomenon occurs in the resist applied to the semiconductor device, there is a problem that a dielectric breakdown of the semiconductor device occurs.

Therefore, as shown in FIG. 2 (B), a conductive resin is applied on the resist layer 22 by spin coating or the like to form a conductive film 24 made of the conductive resin. In order to prevent the electron beam from being distorted, a method has been used.

However, in the method of providing a conductive film on the resist layer to avoid charge-up, the presence of the conductive film having a thickness of about 50 to 200 nm deteriorates the resolution of the resist and the in-plane dimensional distribution. .

When applying the conductive film, an intermixing layer is formed at the interface between the resist layer and the conductive film, and fog development occurs.

Since the resist layer is multi-layered (two or three layers), there are problems that the process becomes complicated and the number of defects increases.

In order to impart conductivity to the resist itself, it is conceivable to add a fine powder of a conductive substance. However, a sufficiently fine conductive fine powder compared to the line width of a pattern to be formed is considered. It is difficult to get.

Therefore, if the resist itself can be made conductive, the resist layer only needs to be a single layer, and the process can be shortened, the number of defects can be reduced, and the resist performance can be prevented from deteriorating.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems associated with a method for preventing a charge-up phenomenon by forming two layers, a resist layer and a conductive film, and includes an electron beam and an X-ray. It is intended to perform high-precision lithography using ionizing radiation such as described above.

The present invention has been studied to enable ultra-fine lithography, and as a result, in order to make the resist itself conductive without forming a conductive film on the resist,
In a negative resist in which a substance having an anion or a cation by irradiation with ionizing radiation and a substance having a cation or an anion as its counter ion forms a polyion complex, at least one substance forming the polyion complex is converted into a highly conductive substance. It has been found that a conductive negative resist can be produced by using a molecular substance, and the present invention has been completed based on such findings.

Hereinafter, the conductive negative resist of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a reaction scheme of a conductive negative resist of the present invention, wherein 1 is a polymer substance that generates cations, and 2 is a conductive polymer substance having an anion. Irradiation with ionizing radiation 3 produces cations 4, resulting in the formation of a polyion complex 5 from anions and cations, increasing the apparent molecular weight, while the unirradiated portion remains unchanged, so that tetramethylammonium hydro When developed with an alkaline aqueous solution such as an oxide, the unirradiated portion dissolves and a pattern of the exposed portion is formed.

Since the resist contains a conductive polymer, a charge-up phenomenon does not occur when irradiating the electron beam, so that the path of the electron beam is not distorted and an accurate pattern is formed. Further, when drawing by an electron beam, by grounding the conductive resist film, it is possible to eliminate the displacement due to charge-up and to draw accurately.

Various anion and cation generators can be used in the present invention.
Examples of the anion generator include orthodiazonaphthoquinone and its derivatives, and examples of the cation generator include triphenylmethanol and its derivatives.

As the conductive high molecular substance, thiophene, acetylene, pyrrolethiazyl, azulene, indene, indole, paraphenylene, naphthylene, anthracene, aniline, phthalocyanine, carbazole, ferrocene, TCNQ complex and their derivatives are used as a skeleton or a side chain. It is selected from the high molecular substances contained in the chain, but a composition which is soluble in a solvent, can be mixed with other components, and can be applied on a substrate is required.

Further, the conductive polymer substance includes -NH
_2, as the amine, such as -CH ₂ -CH ₂ -NH _2, the number 0 to 8 of primary carbon resulting cation, secondary, tertiary amine or ammonium salts or carboxylic acid producing anion, sulfonic acid And a phosphate group.
Since the side chain has a group that generates an anion or a cation, self-doping can be performed by these groups without doping the conductive polymer substance.
The conductivity can be increased.

The substance having an anion or cation is an oligomer or polymer of a dimer or more, and preferably contains an aromatic ring in order to impart dry etching resistance. It is possible to obtain conductivity.

The resist of the present invention is prepared by preparing an equimolar (per monomer unit) mixed solution of a conductive high molecular substance having an anion and a polymer having a cation, and uniformly coating the substrate on a substrate by spin coating or the like. Coating, heat drying, thickness 0.1 ~ 2.0μm
About a resist film can be provided. The heating and drying treatment is usually performed at 80 to 150 ° C. for 10 to 60 minutes, depending on the type of the resist. Next, the cation or anion generator will be described. For example, a mechanism for generating a cation from a triphenylmethanol derivative when the triphenylmethanol derivative is irradiated with ionizing radiation is described below.

[0021]

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When the energy of ionizing radiation is applied to the triphenylmethanol derivative, the hydroxyl group is dissociated to generate a cation.

For example, the mechanism by which an orthodiazonaphthoquinone derivative generates an anion when irradiated with ionizing radiation will be described.

[0024]

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When the orthodiazonaphthoquinone derivative is irradiated with the energy of ionizing radiation, ketene is formed, and subsequently, two kinds of anions, carboxylic acid and sulfonic acid, are obtained in the presence of water molecules. The carboxylic acid is a weak acid and therefore exists as a carboxylate under neutral or alkaline conditions. Since the sulfonic acid is a strong acid, it exists as a sulfonate except for a rather strong acidic region.

[0026]

With the recent high integration of LSIs and VLSIs, resists with higher sensitivity and higher resolution are required, and those with good dry etching resistance and stability are desired. The resist uses a polyion complex formation reaction for the crosslinking reaction of the negative resist,
Since the conductive polymer is incorporated in the resist, the resist can be prevented from being charged, and highly accurate pattern drawing can be performed.

[0027]

Embodiments of the present invention will be described below.

Example 1 As a cation generator, the following triphenylmethanol derivatives were used.

[0029]

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The following polythienylmethylstilphonic acid is used as an anionic conductive polymer.

[0031]

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Was used.

These compounds were mixed with ethoxyethyl 2-acetate in an equimolar amount (per monomer unit) to obtain a resist solution. This resist solution was applied to SOG (SPIN O
NGLASS) was applied on a glass substrate coated with 300 nm by a spin coating method, and prebaked at 120 ° C. for 30 minutes to obtain a uniform resist film having a thickness of 500 nm. The surface resistance at this time was 1 MΩ / □. Next, a beam diameter of 0.05 μm, an energy of 1
An electron beam of 0 keV was irradiated. After the irradiation, this was immersed in an aqueous solution of tetramethylammonium hydroxide for 60 seconds for development, and further rinsed with pure water to insolubilize the irradiated portion. A pattern having a line width of 1 μC / cm ² and a resolution of 0.25 μm was formed. Further, when the in-plane positional deviation was evaluated using a Rampass lightwave 3i (manufactured by Nikon), the positional accuracy was 0.05 μm or less at 3 sigma. The cross-sectional shape of the pattern is also vertical, and the in-plane variation in dimensions is 0.049 at 3 sigma.
μm.

COMPARATIVE EXAMPLE ESPACER10 which is an antistatic film on the upper layer of the resist
A comparative experiment was performed using a two-layer resist coated with a 0 (manufactured by Showa Denko KK). First, a chemically amplified negative resist SNR24
8 (manufactured by Shipley) solution with SOG (SPIN ONG)
(LASS) was applied on a glass substrate coated with 300 nm by a spin coating method, and prebaked at 120 ° C. for 30 minutes to obtain a uniform resist film having a thickness of 500 nm.
Next, an antistatic film ESPACER10 is formed on the resist film.
0 was applied at 2000 rpm to obtain a film having a thickness of 50 nm. The surface resistance at this time was 20 MΩ / □. Next, the resist film was irradiated with an electron beam having a beam diameter of 0.05 μm and an energy of 10 keV. Next, first, the antistatic film was peeled off with water, baked after exposure at 120 ° C., developed by immersing it in an alkaline aqueous solution for 60 seconds, and rinsed with pure water to make the irradiated portion insoluble. When the displacement in the plane was evaluated using the Rampass lightwave 3i, the positional accuracy was 0.12 μm at 3 sigma.
The in-plane variation of dimensions was also 0.08 μm at 3 sigma.

[0035]

The ionizing radiation-sensitive conductive negative resist using the polyion complex formation of the present invention has high sensitivity and high resolution because the molecular weight is increased by a cross-linking reaction due to the formation of an ion complex between a polyanion and a polycation. In addition, since the conductive polymer substance is incorporated in the resist, the problem of charge-up during electron beam exposure can be solved without applying an antistatic film on the resist. As a result, the ionizing radiation lithography process can be greatly reduced, and high-precision drawing can be performed.

[Brief description of the drawings]

FIG. 1 shows the effect of an antistatic film.

FIG. 2 shows a conductive negative resist using polyion complex formation.

[Explanation of symbols]

1 is a polymer substance generating cations; 2 is a conductive polymer substance having an anion; 3 is ionizing radiation; 4 is a cation; 5 is a polyion complex; 6 is an anionic conductive polymer; 7 is a cation; Anion, 9 polyion complex, 21 base material, 22 resist layer, 23 electron beam, 24 conductive resin

Continuation of the front page (56) References JP-A-63-204724 (JP, A) JP-A-2-29654 (JP, A) JP-A-2-39156 (JP, A) JP-A-2-90166 (JP) JP-A-3-26741 (JP, A) JP-A-4-29148 (JP, A) JP-A-4-212962 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G03F 7/038 G03F 7/004 H01L 21/027

Claims (3)

(57) [Claims] 1. A polyion complex is formed in a resist in which a substance which generates an anion or a cation by irradiation with ionizing radiation and a substance having a cation or an anion which is a counter ion thereof form a polyion complex and the molecular weight increases to make the resist insoluble. A conductive resist, characterized in that at least one of the substances is a conductive polymer substance. 2. The method according to claim 1, wherein at least one of a substance which generates an anion or a cation upon irradiation with ionizing radiation and a substance having a cation or an anion which is a counter ion thereof comprises a dimer or a higher oligomer or a polymer. Item 4. The conductive resist according to Item 1. 3. The method according to claim 1, wherein the substance generating a cation is a triphenylmethanol derivative shown below, and the anionic conductive polymer is a polythienylmethylstilphonic acid derivative shown below. The conductive resist according to any one of the above. Embedded image