JP2000147792A - Pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a fine pattern comprising a metal oxide on a substrate by treatment at ordinary temperature or a relatively low temperature. SOLUTION: A coating film having photosensitive hydrophobic groups is formed on a substrate and irradiated with light through a photomask or the like. By this irradiation, the hydrophobic groups in the exposed part are converted into hydrophilic groups and a pattern of a hydrophilic coating film is formed. The resultant coating film is immersed in an aqueous boric acid solution containing a fluorine-containing metal compound and a metal oxide is deposited on the coating film while applying ultrasonic vibration. The metal oxide on the hydrophobic coating film is peeled by the vibration and the metal oxide is deposited only on the hydrophilic pattern. Since the pattern is formed by photolithography and treatment at ordinary temperature is enabled, the objective high density and high precision pattern is formed.

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, and more particularly, to a metal oxide suitable for application to the manufacture of various electric and electronic parts such as a semiconductor integrated circuit (IC), a connector or a capacitor of a DRAM. And a method of forming a pattern.

[0002]

2. Description of the Related Art Conventionally, for example, a semiconductor integrated circuit (IC)
In the manufacture of electronic parts such as electric / electronic circuit boards or DRAM capacitors, a printing method such as screen printing is used as a method for forming an electric / electronic circuit using a metal oxide on a predetermined portion of the substrate. After forming a metal oxide circuit pattern on a substrate by a vapor phase method such as a vapor deposition method, a chemical vapor deposition (CVD) method, a sputtering method, or a coating method using a sol-gel method, unnecessary A method of removing a portion and the like are known.

[0003] For example, Japanese Patent Application Laid-Open No. 7-305027 discloses that a coating agent mainly composed of a photofunctional alkoxysilane and a water-soluble metal nitrate is applied to a substrate, dried, and irradiated with light. A method of forming a pattern by dissolving and removing an unirradiated portion with water is disclosed.

[0004]

However, in the screen printing method, a high molecular weight organic binder is added in order to increase the viscosity of a slurry which is a patterning agent, but heat treatment must be performed at a high temperature to remove this. Not only is the process not simple, but the substrate is limited to those having heat resistance, such as glass.
It is difficult to perform patterning with a fine shape of m or less.

In the case of a gas phase method or a coating method,
After a metal oxide thin film is formed on a substrate, a predetermined pattern is masked with a resist, and unnecessary portions are removed by etching or the like. This method involves applying a photoresist, patterning by exposure, and etching. ,
The removal of the resist and the number of steps are large and complicated. Moreover,
Since the removal of the resist uses an acid, an alkali, or the like, there is a problem that a metal oxide film in a necessary portion may be eroded.

Further, in the case of the gas phase method, since a vacuum system is used, the equipment and facilities become large-sized, which not only increases the cost but also lowers the productivity. In addition, when a coating method such as a sol-gel method is used, since the coating film is formed of a hydroxide, a heat treatment at a high temperature to convert the hydroxide to an oxide is required, which increases cost. Not only
At the time of this heating, the metal species on the substrate migrates, moves to a portion outside the pattern, impairs the sharpness of the pattern outline, and significantly lowers the precision of the pattern. Furthermore, there is also a problem that pattern formation can be applied only to a base material (substrate) having excellent heat resistance due to heat treatment at a high temperature.

On the other hand, also in the method disclosed in Japanese Patent Application Laid-Open No. 7-305027, the substance forming the coating film is a hydroxide coating film, and heat treatment at a high temperature is required to convert this to an oxide. Since it is required, the metal species on the substrate may cause migration and move to a portion outside the pattern, which may significantly reduce the precision of pattern formation.

In addition, according to this method, since the pattern formed on the substrate always contains SiO ₂ , the conductivity of the metal oxide formed as the pattern is reduced, and the desired conductivity is reduced. In some cases, it cannot be fully demonstrated. Furthermore, there is also a problem that the cost is increased by performing the high-temperature heat treatment, and the heat treatment cannot be applied to substrates other than heat-resistant substrates.

An object of the present invention is to provide a pattern forming method capable of patterning a fine shape with a metal oxide directly on a substrate by a normal temperature process or a process at a relatively low temperature. is there. Further, by using this method, various kinds of electronic components of a high-density and high-integrated circuit are to be provided to the market at low cost.

[0010]

In order to solve this problem, a pattern forming method according to the present invention comprises: a step of forming a film having a photosensitive hydrophobic group on a substrate; A hydrophilic pattern forming step of irradiating the hydrophobic film formed on the substrate by the forming step with a light to form a hydrophilic pattern, and the hydrophilic pattern formed on the film by the hydrophilic pattern forming step; And a metal oxide deposition step of depositing a metal oxide via an acid solution containing a fluorine-containing metal compound.

As the "substrate" in this case, besides a semiconductor substrate made of silicon oxide (SiO ₂ ), various ones such as metal, ceramics, glass, carbon, and plastic materials which are susceptible to high temperature can be appropriately selected. There is no particular limitation. In the present invention, since the processing is performed at room temperature or at a relatively low temperature, material selection in such a wide range becomes possible.

As the light source used in the "hydrophilic pattern forming step", various light sources can be applied, and for example, a mercury lamp, a xenon lamp, an excimer lamp, a pulsed laser and the like can be used. Since the irradiation time is determined depending on the output of the light source to be used, it may be appropriately selected according to the light source.

[0013] As described in the second aspect, a silane derivative is preferably used as a film formed by the "hydrophobic film forming step". The “silane derivative” has a hydrophobic group at the terminal opposite to the silane group.

As the silane group of the “silane derivative”, those capable of forming a self-assembled film by hydrolyzing on the surface of the substrate are preferable, and include —SiCl ₃ , —Si
_{HCl 2, -SiH 2 Cl, -SiCH} 3 Cl 2, -S
Preferred is i (CH ₃ ) ₂ Cl.
Further, the length of the straight chain between the silane group and the terminal group of the “silane derivative” is preferably such that _{n in} — (CH ₂ ) _n — is 4 or more. If n is less than 4,
In some cases, the hydrophobicity of the whole molecule of the silane derivative is insufficient. The “silane derivative” includes an aromatic compound and a hydrocarbon compound. More preferably, in the case of aromatic phenyltrichlorosilane or the like, it is useful to form a self-assembled film in which the direction of film formation is uniform.

According to a third aspect of the present invention, the hydrophobic group located at the terminal of the “silane derivative” is:
Reacts with water in the atmosphere to form sulfonic acid groups and hydroxyl groups,
Those exhibiting hydrophilicity are preferable, and for example, a thioacetoxy group, a thiocyano group, an acetoxy group, a phenyl group and the like are preferable.

According to a fourth aspect of the present invention, the "metal oxide deposition step" is performed in a disturbance field, that is, in a state in which a cyclic external force is directly or indirectly applied to the substrate. Is effective. Examples of the direct method include a method of mechanically vibrating the substrate, and examples of the indirect method include an ultrasonic vibration and an AC electric field. Among them, it is particularly preferable to use ultrasonic vibration from the viewpoint of simplicity of the apparatus.

Here, the effect of depositing the metal oxide in the disturbance field is that the deposition of the metal oxide on the hydrophobic portion can be prevented and the edge of the formed pattern can be sharpened. It is. The metal oxide is deposited preferentially on the hydrophilic portion, but there is a possibility that the crystal grows horizontally with the portion as a nucleus and covers the hydrophobic portion. By nature, metal oxides have low adhesion to hydrophobic parts, so by applying a cyclic external force, it is possible to block crystal growth in the horizontal direction,
As a result, it is considered that deposition of the metal oxide on the hydrophobic portion can be suppressed.

The "fluorine-containing metal compound" includes
Suitable examples include metal fluorides and salts such as (NH ₄ ) ₂ TiF ₆ , but are not particularly limited as long as they are water-soluble.

According to a second aspect of the present invention, there is provided the pattern forming method, wherein the silane derivative (phenyltrichlorosilane or the like) is
It utilizes the property of chemically adsorbing on the substrate surface and then polymerizing with each other to form a monomolecular layer, and the property of changing surface functional groups by a photochemical reaction. In other words, after the silane derivative is chemically adsorbed on the substrate, a fine pattern having a different surface functional group is formed on the substrate by light irradiation, and a metal oxide film is formed thereon. (Hydrophobicity and hydrophilicity) can selectively deposit metal oxides.

According to the pattern forming method of the present invention, which is performed through the above steps, it is possible to form a fine pattern with a metal oxide by a normal temperature process near room temperature or a process at a relatively low temperature. Since there is no need to use a simple apparatus, it is possible to provide a pattern forming method which can be performed easily at low cost.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, FIG. 1 shows a schematic process of a pattern forming method according to the present invention. As shown, a hydrophobic film forming step of forming a film on a substrate, and a hydrophilic pattern forming step of irradiating light to the film formed on the substrate in the hydrophobic film forming step to form a hydrophilic pattern And a metal oxide deposition step of depositing a metal oxide on the hydrophilic pattern on the material surface after the hydrophilic pattern formation step.

First, a "hydrophobic film forming step" (FIG. 1)
(A) → (b)) is, for example, to wash the surface of a silicon substrate, and wash it with an organic solvent such as toluene in a trichlorophenylsilane (chemical formula: C ₆ H ₅ SiCl) as a silane derivative.
₃ ) Immerse in the solution in which is dissolved. At this time, the surface of the substrate may be oxidized if necessary.

FIG. 2 is an enlarged view showing the state on the substrate when the silane derivative is used in the “hydrophobic film forming step”. The hydrophobic coating formed in this step is one in which the silane derivative is covalently bonded to the substrate at the terminal silane group, and is preferably a coating of several molecular layers or less, more preferably a monomolecular layer on the substrate. It is desirable.

Next, a "hydrophilic pattern forming step" (FIG. 1)
In (c) → (d)), the substrate on which the above-mentioned hydrophobic film is formed is irradiated with light via a photomask having a predetermined pattern. In this case, as long as light can be irradiated to a predetermined portion, the photomask may be brought into close contact with the substrate, or light may be irradiated at a certain distance.

FIG. 3 shows an enlarged view of the state on the substrate when the silane derivative is used in the “hydrophilic pattern forming step”. Here, the portion irradiated with light changes to hydrophilic, The part which is not irradiated remains hydrophobic, and hydrophilic and hydrophobic parts are formed on the substrate.

Next, in the “metal oxide deposition step” (FIGS. 1 (d) → (e)), the substrate on which the pattern was formed by the above-described hydrophilic pattern forming step was treated with an aqueous solution of a water-soluble fluorine-containing metal compound. The metal oxide is deposited by dipping in a mixed solution with an acid solution.

FIG. 4 shows an enlarged view of the state on the substrate when the silane derivative is used in the “metal oxide deposition step”. FIG. 4 shows an example in which TiO ₂ is deposited as the metal oxide, but shows how the metal oxide is selectively deposited on the hydrophilic portion in this step.

By the way, in this metal oxide precipitation step, a precipitation reaction in the case where a mixed solution in which (NH ₄ ) ₂ TiF ₆ is dissolved in an aqueous boric acid solution is used is shown in Chemical formulas 1 and 2.
The reaction of dissolving the fluorine-containing metal compound and depositing the metal oxide in Chemical formula 1 is a reversible reaction in nature. Therefore, if H ⁺ and F ⁻ generated in the reaction of the chemical formula 1 are consumed by the reaction of the chemical formula 2 using the reaction of the chemical formula 2 with boric acid, which is an irreversible reaction, the chemical formula 1 Reaction goes to the right,
As a result, the deposition of TiO ₂ can be continued.

[0029]

Embedded image TiF ₆ ^2- + 2H ₂ O → TiO ₂ + 4H
^{+ +} 6F ^-

[0030]

Embedded image BO ₃ ^3- + 6H ⁺ + 4F ⁻ → BF ₄ ⁻ +
3H ₂ O

As the acid solution for dissolving the "fluorine-containing metal compound", a boric acid aqueous solution is preferably mentioned. To this, an inorganic acid such as HCl may be added as a pH adjuster for accelerating the precipitation reaction of the metal oxide.

PH of "acid solution containing fluorine-containing metal compound"
Is preferably pH = 1 or more. When the pH is lower than 1, the solubility of the metal oxide is increased, so that the metal oxide may not be deposited. The upper limit of the pH is preferably the pH indicated when the aqueous solution of the fluorine-containing metal compound and the acid solution are mixed. The pH at this time is determined by the metal species, the concentration of the aqueous solution, and the like, but generally shows around pH = 4.

Further, "acid solution containing fluorine-containing metal compound"
The temperature is preferably in a temperature range between room temperature and 100 ° C., preferably 30 ° C. or more and 70 ° C. or less, more preferably 40 ° C. or more and 60 ° C. or less. In a temperature range lower than 30 ° C., the reaction is slowed down, so that time may be required for precipitation. Further, in a temperature range higher than 70 ° C., the reaction may be too fast and the deposition of the metal oxide may be non-uniform.

The immersion time of the substrate may be determined according to the desired thickness of the metal oxide to be deposited. The thickness of the deposited metal oxide depends on the type of the metal, the concentration of the aqueous solution, and the like, and the longer the deposition time, the greater the tendency. Therefore, the immersion time of the substrate may be adjusted in consideration of these various conditions, and is preferably immersed for 0.1 to 24 hours.

[0035]

(Embodiment 1) Si (100) is used as a substrate. First, the substrate is cleaned and then the substrate surface is oxidized. Then, in a glove box, in a nitrogen stream, 0.2 ml of C ₆ H ₅ SiCl ₃
Soak for 5 minutes in an organic solution mixed with ml of toluene solvent. After taking out this substrate, it was dried at 120 ° C. for 5 minutes to form a hydrophobic film (hydrophobic film forming step).

Next, a photomask having a predetermined pattern is set on the substrate on which the hydrophobic film is formed, and irradiated with a mercury lamp (wavelength: 220 to 400 nm) for 2 hours.
In this way, a hydrophilic pattern was formed on the substrate so that only a predetermined pattern of the hydrophobic film became hydrophilic (hydrophilic pattern forming step).

Next, 0.005 mol of (NH ₄ ) ₂ T
iF ₆ and 0.015 mol of boric acid were each added to 50 m
Dissolved in 1 l of distilled water and heated to 50 ° C. Then, after mixing the two solutions, HCl was added to adjust the pH.
Was added in an appropriate amount. Then, the substrate is immersed in the mixed solution, an ultrasonic oscillator is arranged outside the container, and the mixed solution is immersed in the mixed solution for 5 minutes.
While maintaining the temperature at 0 ° C., ultrasonic waves (frequency 47 kHz) are applied to the substrate.
(z, output: 70 W), and the metal oxide was deposited over about 2 hours while irradiating (metal oxide deposition step). afterwards,
The substrate was taken out, washed with distilled water, and naturally dried to produce a product of the present invention (Example 1).

Example 2 The phenyltrichlorosilane used in the hydrophobic film forming step of Example 1 (composition formula:
Instead of C ₆ H ₅ SiCl ₃ ), thioacetate trichlorosilyl undecane (composition formula: CH ₃ COS (C
Except for using H ₂ ) ₁₁ SiCl ₃ ), the test material of Example 2 was produced by going through each step under the same conditions as in Example 1. Therefore, this test material has been subjected to a metal oxide precipitation treatment by ultrasonic irradiation.

(Example 3) In the metal oxide deposition step of Example 1, each step was performed under the same conditions as in Example 1 except that no ultrasonic wave was applied.
Was prepared. Therefore, a film of phenyltrichlorosilane was formed on this test material.

In order to evaluate the products of the present invention (Examples 1 to 3), each substrate was subjected to X-ray diffraction measurement (hereinafter, simply referred to as “XRD”) to measure the metal oxide formed on the substrate. The crystal structure of the product was examined, and the cross section of the substrate was observed with a scanning electron microscope (hereinafter simply referred to as “SEM”).

From the results of the XRD measurement, it was confirmed that the metal oxides formed on the substrates of all the test materials of Examples 1 to 3 were anatase-type titanium oxides.

From the results of SEM observation, it was confirmed that both the test materials of Example 1 and Example 2 were capable of forming a 1 μm-width pattern finely and precisely. On the other hand, in the test material of Example 3, although slight, metal oxide was deposited on the hydrophobic portion, and the edge of the pattern could not be formed sharply.

The reason why the pattern of Example 3 was slightly inferior in the precision as compared with the patterns of Example 1 and Example 2 was that C ₆ H ₅ SiC
and that the hydrophobic portion remaining as l ₃ was weak, by not performing the deposition of the metal oxide in the disturbance field, it is believed that the metal oxides to a hydrophobic moiety had precipitated .

That is, from the comparison between the first embodiment and the third embodiment,
When the hydrophobicity of the hydrophobic film was not so strong, it was confirmed that a fine and precise pattern could be formed by depositing the metal oxide while applying a cyclic external force. Of course, if the hydrophobicity is strong, it is needless to say that the higher effect can be obtained, and that the deposition of the metal oxide in this disturbance field is an extremely effective means for forming a precise pattern. I understand.

The present invention is not limited to the above-described embodiment at all, and various modifications can be made without departing from the spirit of the present invention. For example, although a Si substrate is used in the above embodiment as a substrate for forming a pattern, a semiconductor,
It can be patterned into various things such as single crystal such as ceramics, polycrystal or glass.

As the photosensitive hydrophobic group of the silane derivative, in addition to the above examples, any hydrophobic group such as a thiocyano group and an acetoxy group, which can become a hydrophilic group by a photochemical reaction, can be used. In addition, in addition to the above-mentioned examples, -SiHCl ₂ , -SiH ₂ C
l, -SiCH ₃ Cl _2, or -Si _{(CH 3)} 2 C
l and the like can be applied.

As the disturbance field, in addition to the ultrasonic irradiation used in other than the above embodiment, an AC electric field, mechanical vibration, etc.
Various methods for directly or indirectly applying a cyclic external force to the substrate can be applied.

[0048]

According to the pattern forming method of the present invention, after a film having a photosensitive hydrophobic group is formed on a substrate, light is selectively irradiated on the hydrophobic film via a photomask or the like. Thus, a hydrophilic pattern is formed on the exposed portion of the self-assembled film, and this is immersed in an acid solution containing a fluorine-containing metal compound to precipitate a metal oxide on the exposed portion where the hydrophilic pattern is formed. is there. Therefore, fine patterning by light irradiation is possible, and there is no need to perform a heat treatment at a high temperature, so that there is no migration problem, and a fine and precise high-density pattern can be formed on the substrate.

Further, according to the present invention, the pattern can be formed by normal temperature processing, and since there is no need to use a special vacuum processing device or the like, a product with a pattern formed at low cost can be provided to the market. Things. Therefore, it is very advantageous to apply the present invention to the manufacture of high-density IC circuits or DRAM capacitors. Further, since the present invention can form a pattern on a substrate without performing heat treatment at a high temperature, the substrate does not need to have heat resistance and can be applied to a plastic substrate at low cost. .

Further, in the step of depositing the metal oxide, the step is performed in a state where a cyclic external force is applied, such as applying ultrasonic vibration, so that the metal oxide is not deposited on the hydrophobic coating. Therefore, the edge of the formed metal oxide pattern can be made sharper.

According to this pattern forming method, fine and precise patterns can be formed on various substrates, and the method can be performed easily and at low cost. In addition, the invention contributes to the integration of devices utilizing characteristics such as electrical, magnetic, optical, and chemical properties of metal oxides, and is an industrially extremely useful invention.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic process of forming a pattern according to the present invention.

FIG. 2 is an enlarged view of a state on a substrate in a hydrophobic film forming step shown in FIGS. 1 (a) and 1 (b).

FIG. 3 is an enlarged view showing a state on a substrate in a hydrophilic pattern forming step shown in FIGS. 1 (c) to 1 (d).

FIG. 4 is an enlarged view showing a state on a substrate in a metal oxide deposition step shown in FIGS. 1 (d) to 1 (e).

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Nobuo Kamiya 41 No. 41, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Toyota Central R & D Laboratories Co., Ltd. Address No. 1 (72) Inventor Akira Seo 17th term, Eikando Nishimachi, Sakyo-ku, Kyoto, Kyoto F-term (reference) 2H025 AB16 AC04 AD01 EA04 FA39 2H096 AA25 BA20 CA12 EA03 JA10

Claims (4)

[Claims] 1. A hydrophobic film forming step of forming a film having a photosensitive hydrophobic group on a substrate, and irradiating the hydrophobic film formed on the substrate by the hydrophobic film forming step with light to obtain a hydrophilic film. A hydrophilic pattern forming step of forming a pattern of
A metal oxide deposition step of depositing a metal oxide via an acid solution containing a fluorine-containing metal compound on the hydrophilic pattern formed on the film by the hydrophilic pattern formation step. Method. 2. The pattern forming method according to claim 1, wherein the film formed in the hydrophobic film forming step is made of a silane derivative. 3. The method according to claim 1, wherein the photosensitive hydrophobic group of the silane derivative is
3. The pattern forming method according to claim 2, wherein one or more of organic phenyl group, thioacetoxy group, thiocyano group and acetoxy group are selected. 4. The pattern forming method according to claim 1, wherein the step of depositing the metal oxide is performed in a disturbance field.