JPH08328258A - Pattern formation method - Google Patents

Abstract

PURPOSE: To make it possible to easily form a pattern having excellent resolving performance, sensitivity and substrate dry etching resistance in various exposure methods, such as ArF, X-rays, EB and STM. CONSTITUTION: A substrate 1 to be processed is subjected to a surface treatment to introduce Si-R groups therein and thereafter, a resist film 2 is formed thereon. This resist film is selectively irradiated with energy rays 3, thereby, the Si-R groups on the substrate surface of the irradiated parts are decomposed and the Si atoms are bonded to the molecules in the resist film. The resist film 2 exclusive of the resist film molecules bonded to the Si atoms is removed by developing such film to form the resist patterns 4. The substrate to be processed is processed using such a pattern as mask.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method for forming fine patterns of various solid-state devices.

[0002]

2. Description of the Related Art In order to improve the degree of integration and operation speed of solid-state elements such as LSI, circuit patterns are becoming finer. For these circuit patterns, the resist film formed on the substrate is irradiated with patterned light to induce a photosensitive reaction in the exposed portion, and then developed to form a resist pattern, which is used as a mask for the underlying substrate. It is produced by etching. To form a finer pattern,
The wavelength of exposure light is becoming shorter, and KrF or ArF excimer lasers (wavelengths 248 nm and 193 nm) are being used. Further, in order to form a finer pattern, an X-ray exposure method, an electron beam (EB) drawing method, a pattern drawing method using a scanning tunneling microscope (STM) and the like have been studied.

Various resists are used for these energy rays and various treatment processes are known. In the phenol resin-based resist that has been conventionally used for light exposure, light absorption increases as the wavelength becomes shorter, and pattern formation becomes difficult. Therefore, in the ArF excimer laser, an organic resist containing acrylic resin as a main component is considered. Furthermore, in order to improve the sensitivity of conventional resists, chemically amplified resists have been developed.

Further, in the pattern formation of nm dimension order using electron beam or STM, it has been attempted to use an inorganic resist instead of the above organic resist.

When forming a circuit pattern on various electronic devices, the underlying substrate has various irregularities and reflectance. Since these impede uniform pattern formation, a multilayer resist method, a silylation method, and the like have been developed in which an intermediate layer for flattening or the like is provided between the underlying substrate and the imaging layer.

As a pattern forming method using surface reaction, a pattern forming process using a self-assemble film (SA film) has been proposed.

Regarding the above various resist processes,
For example, resist material process technology, Chapter 1, Section 1 (published by Technical Information Association, 1991, Tokyo), or ULSI
Innovative Lithography Technology, Chapter 9 (Science Forum, 1994, Tokyo).

[0008]

However, each of the above methods has the following problems. An acrylic resin-based resist most suitable for ArF excimer laser has lower resistance to dry etching of the base than a conventional phenol resin-based resist. Further, the chemically amplified resists which improve the sensitivity of these organic resists generally have a problem that they are extremely sensitive and unstable to chemical contamination from the atmosphere or the base.
Further, various inorganic resists generally have low sensitivity. In addition, since it is generally impossible to form a film by a simple spin coating method, C
It is necessary to use a dry deposition method such as VD or sputtering,
Film formation requires time and expense. Further, since the multi-layer resist method and the silylated surface reaction method use dry development, development also requires time and cost. On the other hand, the pattern forming method using the SA film has problems such as the need for metal plating and the formation of pinholes.

An object of the present invention is to provide a simple pattern forming method which can be applied to various exposure methods such as ArF excimer laser, X-ray, EB and STM, and which is excellent in resolution performance, sensitivity and resistance to underlying dry etching. To provide.

[0010]

The above object is to form a resist film on a substrate to be processed into which a Si—R group (where R is a functional group which absorbs and activates the above energy rays) is introduced by surface treatment. Then, the resist film is selectively irradiated with energy rays to decompose the Si—R group in the irradiated portion to combine Si atoms with molecules in the resist film, and this is developed to form a resist film combined with Si atoms. This is achieved by forming a resist pattern by removing the resist film while leaving molecules, and processing the substrate to be processed using the resist pattern as a mask. As the resist, a monomer, an oligomer or a polymer containing a Si-R 'group can be used.
When an ArF excimer laser is used as an energy ray, good results can be obtained by using an R ring containing an aromatic ring.

[0011]

[Function] A substrate surface having an OH group on the surface (for example, Si
When the surface of the natural oxide film is heated and dehydrated) with organosilane, silane coupling material, etc.
a or the following formula, the surface of the substrate is covered with a Si—R group (provided that the substrate having an OH group on the surface is X—
Shall be designated as OH).

X-OH-> X-O-Si-R A resist film 2 containing resist molecules represented by R'-Y is spin-coated on the surface-treated substrate 1 (FIG. 1b).
Next, by selectively irradiating the substrate with energy rays 3, the Si—R bond on the substrate surface is broken and radicals S are generated.
i- is generated (FIG. 1c).

X--O--Si--R.fwdarw.X--O--Si-- Reactive radical Si-- is a resist molecule Y--R '.
And cause a reaction as shown in the following formula to bond. For example, X-O-Si- + R'-Y → X-O-Si-Y In the presence of oxygen or ozone, a siloxane bond is generated as follows.

X-O-Si- + R'-Y → X-O-Si-O-Y On the other hand, in the energy ray non-irradiated portion, the bond between the surface and the molecules in the resist film does not occur (FIG. 1d). Therefore, upon development, the resist film remains on the energy beam irradiation portion, and the resist pattern 4 is formed (FIG. 1e).

By using Y as a substance having etching resistance to X, the resist film formed in the energy beam irradiation portion can be used as a mask for etching the underlying layer. For example, when the base substrate X is Si, by using Y-R 'as a siloxane oligomer or polymer, silicon oxide which is the main component of siloxane functions as an etching mask for Si.
To ensure a sufficient thickness as an etching mask,
It is preferable that the resist molecules have a certain size or more.

Also, the resist molecule Y-R 'itself can generate radicals by irradiation with energy rays. In this case, not only the bond between the substrate and the resist molecule but also the bond between the molecules in the resist simultaneously occur, so that a resist pattern having a relatively large film thickness can be obtained after development. The required film thickness depends on the processed film thickness of the underlying layer, the etching selection ratio, etc. However, when a thick film thickness is required, it is desirable that the bonds between molecules in the resist occur. The resist film pattern formed by this method is an extremely dense film, and pinholes are unlikely to occur unlike the method of selectively removing the SA film by laser light irradiation.

As the energy ray irradiation method, various methods such as an electron beam drawing method, a scanning tunneling microscope (STM), an X-ray exposure method, and an X-ray projection exposure method are applied in addition to the light (laser) exposure method. can do. In any case, the amount of energy (sensitivity) required for pattern formation is determined by the decomposition efficiency of Si-R on the substrate surface or Si-R 'of resist molecules. Therefore, it is preferable to properly select the reactive group according to the energy ray used. For example, Ar
When irradiating with an F excimer laser, when R is a phenyl group, the light absorption peak of the phenyl group and the laser wavelength almost match, and the Si—R bond dissociation occurs extremely efficiently. It can be formed.

Further, the energy rays must reach the interface between the substrate and the resist film. That is, for example, when irradiating with an ArF excimer laser, the resist film must transmit the above laser light to the underlying interface. Therefore, when a resist material containing a phenyl group having strong light absorption at the laser wavelength is used, it is not preferable to make the resist film too thick.

Here, R on the substrate surface is a phenyl group,
Further, it is assumed that the resist molecule Y-R 'is a one-dimensional siloxane molecule whose terminal ends are phenyl groups or the like. A to this
When irradiated with rF excimer laser light or the like, only the phenyl group in the light irradiation part is released, and as shown in FIG. 4, the ends of the phenyl groups may be bonded to each other via oxygen atoms, and a regular structure may be obtained. . If the siloxane molecules in the non-irradiated area are removed by development, the regular structure remains only in the unirradiated area. Although the side chain is omitted in FIG. 4, a three-dimensional Si—O network can be obtained by introducing a phenyl group into the side chain. Since such a structure has regularity at the atomic level, it is considered that the edges of the pattern are extremely smooth and have excellent resolution.

As a substrate having an OH group on its surface, a hydrophilic substrate can be generally used, but even in the case of a hydrophobic substrate, an appropriate surface treatment such as oxygen plasma treatment is performed to remove the OH group. Can be introduced.

[0021]

【Example】

(Example 1) A Si wafer substrate was dipped in a phenyltrichlorosilane solution to form a self-assembled film schematically shown in Fig. 2a on the surface of the substrate. Polymethylsilsesquioxane (GR650, a product name of Showa Denko KK) schematically shown in FIG.
Then, a heat treatment was performed to form a resist film having a thickness of 100 nm. ArF excimer laser exposure device (NA = 0.
5) is used to expose patterns of various dimensions, then
Developed with methyl alcohol. As a result of observing the pattern-exposed portion of the substrate with a scanning electron microscope, a silicon oxide film pattern having a dimension of 0.2 μm and a thickness of about 50 nm is selectively formed on the light-irradiated portion for a laser exposure amount of 200 mJ / cm ² . I confirmed that.

For comparison, when the phenyltrichlorosilane treatment was changed to the hexamethyldisilazane (HMDS, FIG. 2c) treatment used in the ordinary resist process for light exposure, the exposure dose required for pattern formation was about 1
It was 0 times as high as ² J / cm ² . When the same experiment was conducted without surface treatment, 5 J / cm ² was required for pattern formation, and the pattern formed during development was peeled off. From these comparisons, it is clear that the efficient dissociation of the Si-Ph (phenyl group) bond on the substrate by the light of 193 nm largely contributes to the pattern formation.

As a result of dry etching of the Si substrate using the formed silicon oxide film pattern as a mask, a silicon film pattern having a height of 0.2 μm was obtained.

Although phenyltrichlorosilane treatment was used in this example, the present invention is not limited to this as long as Si-R (R includes an aromatic ring) can be formed on the surface. Also, for the resist, various other siloxane polymers or oligomers can be used. For example, polyphenylmethylsilsesquioxane (GR100, product name of Showa Denko KK) in which a part of the methyl groups in FIG. Similar results were obtained using Showa Denko's product name). Further, polymethylsilsesquioxane and polyphenylsilsesquioxane may be mixed in an appropriate ratio. However, in these cases, since Si—Ph in the resist also absorbs light and decomposes, polymerization between resist molecules simultaneously occurs. Therefore, a resist pattern having a larger film thickness can be formed. However,
As the number of phenyl groups increases, the transmittance of the resist decreases and the pattern cross-sectional shape deteriorates. Therefore, it is preferable to select the proportion of phenyl groups in consideration of the required film thickness and pattern shape. It should be noted that although the end is terminated with a hydroxyl group in FIG. 2b, this is not necessarily a necessary condition.

(Example 2) Film thickness of 50 n on a Si wafer
After heating the substrate on which the Si oxide film of m was formed to 100 ° C., the substrate was saturated with saturated phenylmethyldisilazane (FIG.
After standing for 0 seconds, the surface of the substrate was subjected to rough water treatment. Phenylmethylsilane (FIG. 3b) was spin-coated on the substrate to form a resist film having a film thickness of 30 nm. Then, Example 1
Similarly, ArF excimer laser exposure was performed and development was performed. As a result, a silane thin film pattern was formed on the Si oxide film. Using the above pattern as a mask, hydrofluoric acid is used
The oxide film was wet-etched to form a Si oxide film pattern.

(Example 3) A Si wafer substrate was placed at 100 ° C.
After heating to 100 ° C., the substrate surface was left in saturated vapor of hexamethyldisilazane (HMDS) for 120 seconds to roughen the surface of the substrate. Polyhydroxybenzylsilsesquioxane having phenyl group on the side chain (HSQ, Shin-Etsu Silicon trade name, Fig. 3
After c) was spin-coated on the substrate, it was heat-treated at 100 ° C. to form a resist film having a film thickness of 30 nm. Drawing patterns of various dimensions on the above board using an electron beam drawing device,
Then, development was performed using an organic alkaline developer (tetramethylammonium hydroxide 1% aqueous solution). As a result of observing the pattern exposed portion of the substrate with a scanning electron microscope, a resist film pattern having a dimension of about 50 nm and a thickness of about 20 nm was selectively formed on the electron beam irradiated portion with respect to the electron beam exposure amount of 200 μC / cm ² . It was confirmed.

Example 4 The same surface-treated and resist-coated substrate as in Example 3 was drawn using STM. A finer resist film pattern having a size of 10 nm could be formed.

As described above, the present invention can be applied to exposure methods using various energy rays. Although not shown in the above embodiment, soft X with a wavelength of about 5 nm to about 15 nm
It may be applied to a method of performing projection exposure using a line or X-ray lithography for performing mask proximity exposure using a soft X-ray having a wavelength of about 1 nm. Further, it may be applied to holographic exposure or the like using laser light. Further, the surface treatment method, resist material and treatment process, conditions such as exposure and etching are not limited to those described above, and various changes can be made within the scope of the present invention.

[0029]

According to the pattern forming method of the present invention, when a pattern is formed by selectively irradiating an energy beam on a substrate to be processed, the substrate to be processed is surface-treated and Si-
A resist film is formed on top of the introduction of R groups, and the resist film is selectively irradiated with energy rays to decompose the Si—R groups on the substrate surface in the irradiated part to bond Si atoms with molecules in the resist film. Then, the resist film is developed and the resist film is removed by leaving the resist film molecules bonded to Si atoms to form a resist pattern, and the substrate to be processed is processed using the resist pattern as a mask. EB, ST
Even with various exposure methods such as M, it is possible to easily form a pattern excellent in resolution performance, sensitivity, and resistance to dry etching under the base.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention.

FIG. 2 shows the molecular structure of compounds used in various examples of the present invention.

FIG. 3 shows the molecular structure of compounds used in various examples of the present invention.

FIG. 4 is a schematic view showing one embodiment of a pattern forming method according to the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... Resist film, 3 ... Energy ray, 4 ... Resist pattern, X-O-Si-R ... Surface-treated substrate, R'-Y ... Resist molecule, Si -... Radical.

Claims (9)

[Claims] 1. A method of forming a pattern by selectively irradiating an energy beam on a substrate having a material to be processed on the surface thereof, wherein a step of bonding Si—R groups to the surface of the substrate by surface treatment (where R is Is a functional group that absorbs and activates the energy rays), a step of forming a resist film on the surface-treated substrate, and an interface between the resist film and the substrate is selectively irradiated with energy rays to expose the irradiation part. A step of forming a resist pattern by combining the Si atoms with molecules in the resist film, and developing the resist film to remove the resist film leaving the resist film molecules combined with the Si atoms. A pattern forming method characterized by the above. 2. The pattern forming method according to claim 1, wherein the resist film contains a monomer, an oligomer or a polymer containing a Si—R ′ group as a main component. 3. The bond between the Si atom and the resist molecule is
The pattern forming method according to claim 1, wherein the Si-R group is generated by absorbing an energy ray and dissociating. 4. The bond between the Si atom and the resist molecule is
3. The pattern forming method according to claim 2, wherein the Si—R ′ group is generated by absorbing energy rays and dissociating them. 5. The pattern forming method according to claim 1, wherein the energy rays are light having a wavelength of 260 nm or less, X rays, electron rays, or focused ion beams. 6. The R group or R'group contains a benzene ring,
The pattern forming method according to claim 1 or 2, wherein the energy beam is an ArF excimer laser. 7. The pattern forming method according to claim 1, further comprising a step of processing the material to be processed using the resist pattern as a mask. 8. The pattern forming method according to claim 1, further comprising the step of introducing a hydroxyl group into the surface of the substrate before the surface treatment. 9. A method for forming a pattern by selectively irradiating an energy beam on a substrate having a work material on its surface, the step of forming a self-assemble monolayer on the surface, wherein the self-assemble monolayer is formed. A step of forming a polymer or oligomer film, selectively irradiating the interface between the self-assemble monolayer and the polymer or oligomer film with an energy beam, and chemically arranging the irradiated part between the self-assemble monolayer and the polymer or oligomer. And a step of developing to remove the polymer or oligomer film in the unirradiated portion of the energy beam.