JPH05132561A - Material and method for forming fine pattern of ferroelectric thin film - Google Patents

Abstract

PURPOSE:To prepare the subject material which enables a fine resistless patterning of a ferroelectric thin film by mixing a colloidal soln. contg. a specific polymer with a specific sensitive compd. CONSTITUTION:A colloidal soln. contg. a polymer of formula I (wherein R1 is a group such as CH3 or C2H5; R2 is a group such as CH=CH2; R3 is a group such as phenyl; and M is a metal atom such as Pb, Zr, Ti, La, or Ba) is mixed with a sensitive compd., which responds to an electromagnetic wave or corpuscular ray to cause the cross-linking between the polymers (e.g. a compd. of formula II).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric thin film fine pattern used for forming a fine pattern of a ferroelectric thin film in the production of a ferroelectric memory, a ferroelectric sensor, a superconducting device and the like. The present invention relates to a forming agent and a ferroelectric thin film fine pattern forming method in the case of forming a fine pattern of a ferroelectric thin film using the ferroelectric thin film fine pattern forming agent.

[0002]

2. Description of the Related Art At present, as a new semiconductor memory device, a thin film ferroelectric memory has been proposed which uses a high dielectric material having a polarization inversion characteristic and a high dielectric constant and easily fused with a semiconductor process. Since such a ferroelectric memory is non-volatile, it can be used as a non-volatile memory, and since the amount of voltage and current at the time of rewriting is small, it is possible to configure a practical non-volatile memory. Has become. That is, in an ordinary semiconductor memory such as EPROM, in order to clear the stored contents,
A current or voltage source for clearing is required separately because it is necessary to apply a current or voltage that is excessively higher than usual or to place it under conditions different from normal. However, in the ferroelectric memory, the stored contents can be changed or cleared under the same conditions as usual, so that it is not necessary to install the current source or the voltage source as described above. Of.

Ferroelectrics are not only used in the above-mentioned ferroelectric memories, but also expanded to various ferroelectric sensors and liquid crystal displays, as well as superconducting devices and functional glasses. It's being done. In applying a ferroelectric substance to such a field, it is necessary to process the ferroelectric thin film into a predetermined pattern. For this reason, a method of forming a fine pattern of the ferroelectric thin film (ferroelectric thin film) Although a fine pattern forming method) is important, conventionally, the ferroelectric thin film was processed as follows to form a predetermined pattern.

In the past, a ferroelectric thin film was formed by forming a film by RF sputtering, followed by baking and crystallization. The microfabrication process for the ferroelectric thin film thus formed is based on a chemical wet etching method, a physical dry etching method such as ion milling, or hydrogen chloride or tetrafluoromethane as a base. It was performed by plasma etching or the like. Here, in the wet etching method,
When an alkaline solution such as potassium hydroxide or sodium hydroxide is used as the etching solution, it is preferable to remove the thin film portion other than the predetermined pattern by using the etching solution after forming the alkali-resistant photosensitive film resist by the lithography technique. Was getting the pattern. Here, when an acidic solution of phosphoric acid, sulfuric acid, hydrochloric acid, bromic acid or the like is used as an etching solution, a desired pattern is formed by using an acid resistant photosensitive film resist.

[0005]

However, each of the above processing techniques has the following drawbacks.

(1) Since wet etching is isotropic etching, there is a problem that fine processing cannot be performed because undercutting causes thinning of the remaining pattern and peeling of the resist when forming a fine processed pattern.

(2) Ion milling has excellent fine workability, but has a problem of damage to the underlying substrate and a problem of selectivity with the resist.

(3) The plasma etching has problems that the etching rate is very low, it is not mass-producible, the substrate is largely damaged, and the active layer of the lower wiring is largely damaged.

In any of the above methods, the conventional method has a problem that the number of steps is large and the cost is high because etching is performed after forming a desired pattern with a resist.

The present invention has been made in view of the above problems, and an object thereof is to overcome the above-mentioned drawbacks and to enable a resistless fine processing of a ferroelectric thin film by a simple process. A thin film fine pattern forming method and a forming agent are provided.

[0011]

In order to solve the above problems, in the present invention, the material itself for forming a ferroelectric thin film is etched without etching using a resist. Characterize.

Therefore, in the present invention, first, as a ferroelectric thin film fine pattern forming agent for forming a fine pattern of a ferroelectric thin film, a polymer represented by the following chemical formula 4 and a substance sensitive to electromagnetic waves or particle beams are used. And a sensitive compound that forms crosslinks between the polymers.

[0013]

[Chemical 4]

It is preferable to use a photocrosslinking aromatic bisazide compound represented by the following chemical formula 5 as a sensitive compound which is sensitive to electromagnetic waves or particle beams to form crosslinks between the polymers. ..

[0015]

[Chemical 5]

Further, in forming a fine pattern of a ferroelectric thin film using the ferroelectric thin film fine pattern forming agent, a forming agent applying step of applying the ferroelectric thin film fine pattern forming agent to a substrate, A lithographic process of irradiating an electromagnetic wave or a particle beam along a desired circuit pattern to draw the circuit pattern, and a removal process for removing the ferroelectric thin film fine pattern forming agent at a part not drawn in the lithographic process A ferroelectric thin film fine pattern forming method including a step and a sintering step of firing the circuit pattern formed in the removing step is used.

[0017]

In the ferroelectric thin film fine pattern forming agent and the ferroelectric thin film fine pattern forming method of the present invention having the above constitution, a colloidal solution containing the polymer shown in Chemical formula 4 is applied to an electromagnetic wave or a particle beam. A ferroelectric thin film fine pattern forming agent is prepared by adding a sensitizing compound (for example, a photo-crosslinking aromatic bisazide compound represented by Chemical formula 5) that sensitizes to form crosslinks between the polymers.

This ferroelectric thin film fine pattern forming agent is
When the ferroelectric thin film fine pattern forming agent is applied to the substrate in the forming agent applying step, electromagnetic waves or particle beams (hereinafter referred to as electromagnetic waves) are irradiated along the desired circuit pattern in the lithographic step.

Here, in the portion of the ferroelectric thin film fine pattern forming agent irradiated with the electromagnetic wave or the like, the sensitive compound contained in the ferroelectric thin film fine pattern forming agent reacts to activate radicals or the like. Generate seeds. And
Since this active species attacks and cleaves the unsaturated bond of the polymer shown in Chemical formula 4, a crosslink is formed between the polymers of Chemical formula 4 contained in the ferroelectric thin film fine pattern forming agent. Becomes When the crosslinks are formed in this way, the fluidity at the locations where the crosslinks are formed is smaller than at the locations where the crosslinks are not formed. Therefore, in the ferroelectric thin film fine pattern forming agent, the portion irradiated with electromagnetic waves or the like has a lower fluidity than the non-irradiated portion, and therefore the portion irradiated with the electromagnetic waves or the like by a known method is used. It becomes possible to leave it on the substrate. Therefore, in the lithographic process, after the electromagnetic wave or the like is irradiated along the desired circuit pattern, it is possible to leave the desired circuit pattern on the substrate by using a known removing means (removing process). .. Then, the circuit pattern left on the substrate in the removing step has 60
When baked at a temperature of about 0 to 800 ° C., the organic functional group portion of the polymer compound (crosslinked polymer of Chemical Formula 4) forming the circuit pattern is removed. In this way, when the organic functional group portion of the crosslinked polymer of Chemical formula 4 is removed, only the component that constitutes the ferroelectric remains on the circuit pattern, but this is crystallized by the heating in the sintering process. As a result, a fine pattern of the ferroelectric thin film is formed along the circuit pattern.

[0020]

The characteristics of this example are as follows. A ferroelectric containing a component constituting a ferroelectric substance and having an unsaturated bond, and a ferroelectric bisazide compound for forming a cross-link in the polyalkoxide. The use of a body thin film fine pattern forming agent. Then, this is irradiated with an electromagnetic wave or the like to form cross-links between the molecules, only the cross-linked molecules are left on the substrate, and the molecules remaining on the substrate are heat-treated to form a ferroelectric crystal. Is to form.

First, the chemical formula 6 shows the constitution of the polymer (original polymer) used in this embodiment.

[0022]

[Chemical 6]

By the way, typical ferroelectric substances are PZT and PLZT.
It contains elements such as zirconium, lead, titanium, and lanthanum, which are raw materials of ZT and PLZT. Therefore, after this organic functional group is removed, only the component that forms the ferromagnetic thin film such as PZT remains. Here, in order to oxidize and remove the organic component in the molecule of the original polymer, the original polymer is treated at high temperature. Then, after the organic component in the molecule is removed and only the component that constitutes the ferroelectric substance remains, the high temperature treatment is continued, and this crystallization progresses to form perovskite type fine crystal grains. Like In this way, by forming perovskite type fine crystal grains having domains that are spontaneously polarized in a certain direction, a ferroelectric substance is formed.

Here, the original polymer is a polyalkoxide having the above metal element as a central atom, and an organic functional group is bonded to this central metal, and the organic functional group is unsaturated. Contains a join. And
The aromatic bisazide compound described in Chemical formula 7 is added together with this polymer, and these are mixed with an appropriate solvent to prepare the ferroelectric thin film fine pattern forming agent according to this example.

FIG. 1 is a diagram for explaining a method for forming a ferroelectric thin film fine pattern forming agent according to this embodiment, and FIG. 2 is a diagram for explaining a method for forming a ferroelectric thin film fine pattern using this forming agent. FIG.

First, a metal butoxide having an unsaturated bond in the molecule is mixed, and diethanolamine as a polymerization inhibitor is added thereto. Toluene and isopropanol are added to this mixture to form a colloidal solution containing the metal butoxide. Then, water is added to this colloidal solution. When water is added to the colloidal solution containing the metal butoxide, hydrolysis occurs to generate normal butanol and metal hydroxide, but the metal hydroxides immediately undergo a polymerization reaction to form the original polymer. ..

Here, the length of the molecule of the original polymer is adjusted by suppressing the reaction by diethanolamine added in advance in the system.
The fact that the molecular length of the original polymer is adjusted means that
That is, the viscosity of the ferroelectric thin film fine pattern forming agent containing this is adjusted. If the viscosity is too high, it is not suitable for the ferroelectric thin film fine pattern forming method according to the present embodiment. This is because it is not suitable for coating on a substrate with a constant heat, and it is unsuitable for removing from a portion other than a predetermined pattern.

An aromatic bisazide compound represented by the following chemical formula 7 is added to the colloidal solution having a predetermined viscosity thus produced to form a fine pattern of the ferroelectric thin film according to this embodiment. The agent is created. Further, a sensitizer (1-nitropyrene, 1,8-dinitropyrene, etc.) as shown in FIG. 1 is added.

[0029]

[Chemical 7]

These mixtures are first stirred (S2
01) After the composition is made uniform, the substrate is uniformly coated in the forming agent applying step of S202. In this embodiment, spin coating is used to achieve uniform coating. Then, after drying for a while (S203), selective irradiation of ultraviolet rays, X-rays, particle beams and the like (hereinafter, simply referred to as electromagnetic waves) is performed in S204.

When the mixture is irradiated with an electromagnetic wave or the like, a crosslinking reaction as shown in FIG. 3 occurs. That is, when the aromatic bisazide compound is irradiated with electromagnetic waves or the like (hereinafter, simply referred to as light irradiation), nitrogen gas is released and nitrogen in a monovalent excited state is generated in the molecule. Then, this monovalent nitrogen attacks the unsaturated bond contained in the polyalkoxide molecule, cleaves the unsaturated bond, and adds. By the way, since the bisazide compound has two such azido groups, the above-mentioned addition reaction occurs at both ends of the molecule. Therefore,
When each of the plurality of original polymers is attacked, a crosslink is formed between these molecules. When the crosslinks are formed in this way, the polymer becomes more polymer than the parts where the crosslinks are not formed.Therefore, the viscosity of the ferroelectric thin film micropatterning agent increases only at the parts where the crosslinks are formed, and the fluidity decreases To do. Therefore, by using a known method, it is possible to selectively remove only the portion where the crosslinking reaction has not occurred, and selectively leave only the portion where the crosslinking reaction has occurred on the substrate.

In the lithographic process in S204, light irradiation is performed along a predetermined pattern. Therefore, the cross-linking reaction occurs along a predetermined pattern irradiated with light, the viscosity increases and the fluidity decreases only at the relevant portion, and it can endure most organic solvents.
In the removal step of S205, benzene is used as a solvent, and the ferroelectric thin film fine pattern forming agent at the portion where the light irradiation is not performed is removed, and the ferroelectric thin film fine portion where the light irradiation is not performed is removed. The patterning agent will be left behind. The ease of removal in the removal step of S205 can be adjusted by adjusting the amount of diethanolamine added in advance to the system as a polymerization reaction inhibitor.

Next, in the heating step of S207, 300
After the drying is performed at the temperature of 500 to 500 ° C., the heat treatment is performed in the sintering step of S208. In the sintering step of S208, by heating at 600 ° C. to 700 ° C., the organic functional group moiety is oxidized and removed from the polymer compound formed by crosslinking, and at the same time, the residual metal alkoxide moiety is removed. Crystallization occurs in the glass and a perovskite structure is formed.

As described above, in the ferroelectric thin film fine pattern forming agent according to the present embodiment, the ferroelectric thin film fine pattern forming agent is irradiated with light according to a predetermined pattern, and based on the viscosity difference generated. By removing the forming agent by using the resist, it is possible to form a fine pattern of the ferroelectric thin film on the substrate without using a resist.

[0035]

As described above, in the method and the agent for forming a ferroelectric thin film fine pattern according to the present invention, resistless fine processing of a ferroelectric thin film can be performed, and damage during dry etching can be reduced. This has the advantage that the process can be simplified.

[Brief description of drawings]

FIG. 1 is a flow chart showing a flow of operations when forming a ferroelectric thin film fine pattern forming agent according to the present embodiment.

FIG. 2 is a flowchart showing an operation flow of a ferroelectric thin film fine pattern forming method according to the present embodiment.

FIG. 3 is an explanatory diagram illustrating a reaction mechanism of a crosslinking reaction of this example.

[Explanation of symbols]

 S202 Forming agent applying step S204 Lithographic step S205 Removing step S208 Sintering step

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[Procedure amendment]

[Submission date] February 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The present invention has been made in view of the above problems, and an object thereof is to overcome the above-mentioned drawbacks and to enable a resistless fine processing of a ferroelectric thin film by a simple process. it is to provide a thin film fine pattern forming method and a forming agent.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

Here, in the portion of the ferroelectric thin film fine pattern forming agent irradiated with the electromagnetic wave or the like, the sensitive compound contained in the ferroelectric thin film fine pattern forming agent responds to the activation of radicals and the like. Generate seeds. And
Since this active species attacks and cleaves the unsaturated bond of the polymer shown in Chemical formula 4, a crosslink is formed between the polymers of Chemical formula 4 contained in the ferroelectric thin film fine pattern forming agent. Becomes When the crosslinks are formed in this way, the fluidity at the locations where the crosslinks are formed becomes smaller than at the locations where the crosslinks are not formed. Therefore, the part of the ferroelectric thin film fine pattern forming agent that is irradiated with electromagnetic waves has less fluidity than the part that is not irradiated.
Since it does not dissolve in the solvent, it becomes possible to leave the portion irradiated with the electromagnetic wave or the like on the substrate by a known method. Therefore, in the lithographic process, after being irradiated with electromagnetic waves along the desired circuit pattern,
By using a known removing means, the desired circuit pattern can be left on the substrate (removing step). Then, when the circuit pattern left on the substrate in the removing step is fired at a temperature of about 600 to 800 ° C. in the sintering step, a polymer compound forming the circuit pattern (crosslinked polymer of Chemical Formula 4). Therefore, the organic functional group portion of is removed. In this way, when the organic functional group portion of the crosslinked polymer of Chemical formula 4 is removed, only the component that constitutes the ferroelectric remains on the circuit pattern, but this is crystallized by the heating in the sintering process. As a result, a fine pattern of the ferroelectric thin film is formed along the circuit pattern.

Claims (4)

[Claims] 1. A ferroelectric thin film fine pattern formed by adding a sensitizing compound that is sensitive to electromagnetic waves or particle beams to form crosslinks between the polymers to a colloidal solution containing the polymer shown in Chemical formula 1. Agent. [Chemical 1] 2. A ferroelectric thin film fine pattern forming method for forming a fine pattern of a ferroelectric thin film, comprising the following steps: (a) The ferroelectric thin film fine pattern forming agent according to claim 1 on a substrate. A forming agent application step of applying, (b) a lithographic step of irradiating an electromagnetic wave or a particle beam along a desired circuit pattern to draw the circuit pattern, and (c) strength of a portion where drawing is not performed in the lithographic step. A removing step of removing the dielectric thin film fine pattern forming agent, and (d) a sintering step of firing the circuit pattern formed in the removing step. 3. A ferroelectric thin film fine pattern forming agent for forming a fine pattern of a ferroelectric thin film, comprising: (a) a polymer shown in Chemical formula 2, (B) A photocrosslinking aromatic bisazide compound represented by Chemical formula 3. [Chemical 3] 4. A ferroelectric thin film fine pattern forming method for forming a fine pattern of a ferroelectric thin film, comprising: (a) a ferroelectric thin film fine pattern forming agent as set forth in claim 3. Forming agent application step of applying to a substrate, (b) lithographic step of irradiating an electromagnetic wave or particle beam along a desired circuit pattern to draw the circuit pattern, (c) location where drawing was not performed in the lithographic step A removing step for removing the ferroelectric thin film fine pattern forming agent, and (d) a sintering step for firing the circuit pattern formed in the removing step.