JPS63165845A - Pattern forming method - Google Patents

Abstract

PURPOSE:To simply form a pattern having superior resistance to oxygen plasma by projecting specified ions on a resist film. CONSTITUTION:A high molecular material layer is formed on a substrate and a radiation sensitive material layer contg. a polymer having functional groups capable of being electrically charged by accepting or releasing protons or electrically charged functional groups is formed on the high molecular material layer. The radiation sensitive material layer is exposed and ions are electrostatically bonded to the resulting pattern during or after development. The lower high molecular material layer is then dry-etched with oxygen plasma through the pattern as a mask. By this pattern forming method, resistance to oxygen plasma is provided to the resist pattern by introducing the ions and a desired fine pattern can be formed by dry etching with oxygen plasma through the resist pattern as a mask.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a pattern forming method, and particularly to a semiconductor device,
The present invention relates to a pattern forming method suitable for forming fine patterns for manufacturing photomasks and the like.

(Prior art) As a microfabrication technology for manufacturing high-density integrated circuits, magnetic bubble devices, and optical components, optical lithography technology and iP are used to generate ionizing radiation such as electron beams, X-rays, and ion beams, or short-wavelength radiation. Lithography using ultraviolet light, etc. is being put into practical use.

In particular, the latter lithography technique is indispensable for microfabrication of about 0.5 μm or less.

In recent years, as semiconductor devices have become three-dimensional, there has been a tendency to form resist patterns on semiconductor substrates with considerable steps and to perform microfabrication. In such a case, it is necessary to increase the resist film thickness to a certain extent, but increasing the resist film thickness causes a problem that conversely causes a decrease in resolution.

For this reason, a thick planarization layer is formed on the semiconductor substrate, several layers including a thin resist film are formed on top of this, and the resist pattern of the upper layer is sequentially transferred to the lower layer by dry etching to improve the shape ratio. Multilayer processes are being used to form resist patterns with high resistivity. As a normal multilayer resist, a three-layer system is most often used, in which an intermediate layer having oxygen plasma resistance is formed on the leveling layer 2, and a thin resist film is formed on the leveling layer 2. However, this method has the problem that the drying process must be repeated several times to transfer the resist pattern, making the process extremely complicated.

Therefore, a two-layer resist process is being developed in which a resist film that is itself resistant to oxygen plasma is formed on the planarization layer. As resists having such oxygen plasma resistance, chloromethylated polydiphenylsiloxane, chloromethylated polyphenylmethylsilane, and the like are conventionally known. However, in order to obtain these resists that are resistant to oxygen plasma, complicated synthesis methods must be used, resulting in the problem that the resulting materials become expensive.

In addition, there was a problem that differences in properties between synthetic lofts were likely to occur, making it difficult to control the quality of the resist.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and by applying specific ions to a normal resist pattern, a pattern with excellent oxygen plasma resistance can be created. The present invention aims to provide a pattern forming method that can be easily formed at relatively low cost and with good reproducibility.

[Structure of the Invention] (Means for Solving the Problems) The present invention comprises a step of forming a polymer material layer on a substrate, and a process of attaching or detaching protons to the structure of the polymer material layer to charge it. A step of forming a radiation-sensitive material layer containing a polymer having a functional group that can be charged or a functional group that is directly charged; This method is characterized by comprising the steps of electrostatically bonding, and using this pattern as a mask, dry etching the lower layer of high dielectric material using oxygen plasma.

Examples of the substrate include a single silicon substrate doped with impurities, a semiconductor substrate in which a conductive film such as a polycrystalline silicon film is provided on the silicon substrate via a silicon oxide layer, a blank mask, and the like.

As the polymer material layer (flattening layer), any polymer material that can be formed into a thin film, such as polystyrene, can be used. Such a polymeric material layer can be formed by applying a polymeric material solution in which the material is dissolved in a solvent onto the substrate using a spinner, for example, and drying it. Suitable solvents used here include, for example, toluene, xylene, ethyl cellosolve acetate, and cyclohexanone. Furthermore, the polymer material solution may further contain additives such as diazide compounds for enhancing properties such as thermosetting properties. The viscosity of the polymeric material solution is desirably adjusted to 20 to 10Ocp8%, more preferably 60 to 100cps, considering application using a spinner or the like. Furthermore, it is desirable that the thickness of the polymeric material layer be in the range of 1 to 2 μm. The reason for this is that if the thickness of the polymeric material layer deviates from the above range, there is a risk that the resolution will decrease or that flattening on a substrate with steps may not be achieved. In addition, J! A baking treatment may be performed after applying the polymeric material solution onto the plate and drying it. This baking process condition is
The temperature is sufficient to evaporate the solvent and exceeds the glass transition point of the polymeric material used, but usually ioo
~250°C for 0.1 to 1 hour, preferably 150 to 20
It may be carried out at 0°C for 0.4 to 1 hour.

Examples of the functional groups that can be charged by attaching or detaching protons in the polymer constituting the L-order radiation-sensitive material include aromatic rings to which a hydroxyl group is bonded, sulfonic acid groups,
Examples include an amino group and a carboxyl group. Polymers containing these functional groups include, for example, polyvinylphenol, polypropenylphenol, cresol novolak resin, or phenolic resins in which the hydroxyl groups of some of them are allylated, esterified with chlorine-containing acyl groups, or methacrylated. , polystyrene sulfonic acid,
Nafion, polyvinylpyridine, polyacrylic acid, polymethacrylic acid, etc. can be mentioned. It may also be a copolymer of the constituent units of such polymers and the constituent units of ordinary resist materials, such as a copolymer of styrene sulfonic acid and styrene, a copolymer of vinylpyridine and styrene, a copolymer of methacrylic acid and styrene, and a copolymer of styrene sulfonic acid and styrene. Examples include a copolymer of methyl methacrylate, a copolymer of α-chloro-γ-tetrofluoroethyl acrylate and methacrylic acid, and the like.

Examples of functional groups that are directly charged include quaternary amino groups such as trimethylammonium, triethylammonium, and dimethylethylammonium groups. Examples of polymers containing this quaternary amino group include N-methyl Examples include polyvinylpyridine and N-benzylpolyvinylpyridine. These functional groups occupying in the polymer desirably account for 5% or more based on the molar amount of residues in the polymer, and if it is less than 5%, the amount of ions incorporated into the polymer decreases. There is a risk that the resistance to drying by oxygen plasma in subsequent steps may be reduced.

In addition to the above-mentioned polymer, the radiation-sensitive material may optionally include polymethyl methacrylate, polyα-chloro-γ-
Ordinary resist materials such as tetrafluoroethyl acrylate, polychloromethylstyrene, and Resin-M, and 1-8
A 0% sensitizer such as a naphthoquinonediazide compound or a bisazide compound may be blended.

The 1-number radiation sensitive material is usually dissolved in a solvent, applied to the polymeric material layer L using, for example, a spinner, and dried to form a two-layer resist. Suitable solvents used here include, for example, cyclohexanone and ethyl cellosolve acetate. This solution may further contain additives such as octylmethylcyclotetrasilazane and hexamethylcyclotrisilazane for improving coating properties and film-forming properties. The viscosity of the radiation-sensitive material solution is 20 to 1, considering application with a spinner etc.
00 cps, more preferably Go ~100 cps
It is desirable to adjust it to s. Further, the thickness of the radiation sensitive material layer is 0.1 to 0.5 μm, more preferably 0.2 μm.
It is desirable that the thickness be in the range of ~0.5 μm. The reason for this is that if the thickness of the radiation-sensitive material layer deviates from the above range, oxygen plasma resistance may be reduced or resolution may be reduced. Note that a radiation-sensitive material solution may be applied onto the polymer material layer, dried, and then subjected to baking treatment. The baking treatment conditions are a temperature sufficient to evaporate the solvent and a temperature exceeding the glass transition point of the polymer material used, usually at 100-250°C for 0.1-1 hour, preferably at 150-250°C. What is necessary is just to carry out at 200 degreeC for 0.4 to 1 hour. After such a radiation-sensitive material layer is formed, it is selectively irradiated with radiation and exposed, and then the unexposed portions or exposed portions of the radiation-sensitive material layer are developed with a developer and removed.

As the above-mentioned developer, a normal organic solvent can be used, but especially when the radiation-sensitive material has an aromatic ring to which a hydroxyl group is bonded, an alkaline developer can be used. It is desirable because it can reduce the swelling of This developing solution preferably contains 1 to 50% of tetramethylammonium hydroxide, choline, and the like.

The ions to be treated at the same time as the development or after the development are listed below.

■, Ag+, Aノ3◆, Cu◆, Fe2”, Fo 3
+ , Mn 2 + , Ni 2 + , Pb 2
Single metal ions such as +, T14+, Coz+, Co3+, Sn4+.

■, CI to the metal ion mentioned in ■! ,CN,NH3,OH
, phenanthroline, dipyridine, acetylacetone,
A complex compound coordinated with a ligand such as oxine.

(2) An ammonium compound in which a silicon atom is introduced into the molecule represented by the following general formula.

1+ R2-N R & 1u, R1-R4 in the formula may be the same or different, at least R1 is an alkyl group containing a silicon atom, and the remaining R2-R4 are hydrogen, an alkyl group, and an alkyl group containing a hydroxyl group. group, or an alkyl group containing a silicon atom.

■ Ammonium compounds containing germanium or gallium.

(2) An organometallic compound of the metal ion of (2) above and a hydrocarbon having six charged sites.

Examples of the alkyl group containing a silicon atom introduced into the general formula include -C112-9t(C1hh, -(C112)2-5
i(CI!3)s.

-(C1lz)a -5i(CHs)3. -CH20
Si(CHa)3゜-C112-81(OCIla)3
．． -(C112)2-! 3i (OCIla) 3゜-CI
+20CII 2 St (CI+3)3.

etc. can be mentioned.

The amount of the compound as ions in the solution is preferably in the range of 0.1 mmol to several moles. If this solution is an aqueous solution, it is desirable to use one whose pH is adjusted to such a level that the ions it contains are stable and the charged sites within the composite of the radiation-sensitive material to be treated are sufficiently charged. For example, when polymethacrylic acid is used as the polymer, sufficient charge can be generated on the melon by adjusting the pH of the solution to 4 or higher and containing ions.

"The introduction of two series of ions imparts oxygen plasma resistance to the resist pattern, and using this resist pattern as a mask, the underlying polymer material layer is dry-etched using oxygen plasma to form the desired fine pattern. can do.

(Function) According to the present invention, a polymer material layer is formed on a substrate, and a functional group that can be charged by attaching or desorbing protons in its structure, or a functional group that can be charged as it is, is formed on the polymer material layer. A radiation-sensitive material layer containing a polymer having a functional group is formed, and after this radiation-sensitive material layer is exposed, it is developed simultaneously with development, that is, using a developer in which ions are dissolved, or after development, ions are removed. By immersing the pattern in the containing solution, ions can be electrostatically bound to the pattern, resulting in the formation of a pattern on the polymeric material that is highly resistant to oxygen plasma. For example, when a radiation-sensitive material layer containing a polymer having an aromatic ring to which hydroxyl groups are bonded is exposed and then developed using an alkaline developer, protons are desorbed from the hydroxyl groups in the unexposed areas and a charge of 〇- is generated. The pattern is then treated with a solution containing oppositely charged ions, thereby introducing the ions into the pattern and imparting resistance to oxygen plasma. On the other hand, if ions are added to the alkaline developer in advance, protons are removed from the hydroxyl groups in the unexposed areas at the same time as development, generating an O- charge, and at the same time positively charged ions are introduced. and oxygen plasma resistance. As a result, by using the pattern as a mask and dry etching the underlying polymer material layer (flattening layer) with oxygen plasma, it is possible to easily form a fine and highly accurate pattern that is faithful to the pattern at the time of exposure.

In addition, a radiation-sensitive material layer containing a polymer that generates a functional group that can be charged by attaching or detaching protons when irradiated with radiation is formed on a substrate, and after exposure and development, a layer of ions is formed. By treating the exposed area with a solution containing the oxide, oxygen plasma resistance can be easily imparted to the exposed area, and as a result, dry development using oxygen plasma becomes possible.

In addition, if the radiation-sensitive material layer is directly formed on the substrate, and a normal resist film sensitive to radiation is formed on the layer 1-, and then exposed, developed, and treated with a solution containing ions, the upper resist layer can be formed directly on the substrate. Oxygen plasma resistance can be imparted to the portion of the lower radiation-sensitive material layer exposed through the opening. the result,
By drying with oxygen plasma,
The resist film and the radiation sensitive material layer except for the oxygen plasma resistant layer in the opening are etched to form a pattern that is inverse to the pattern of the upper layer.

(Example of the invention) Examples of the present invention will be described in detail below.

Example 1 5% of 2.6-bis-(4'-diazidebenzal)-14-methylcyclohexanone with a thickness of 1.5 μm on one substrate
A polystyrene film containing the following was formed and heated at 200° C. for 1 hour to form a flattening layer. Subsequently, after forming an ultraviolet sensitive material layer (manufactured by Tokyo Ohka Co., Ltd. under the trade name OF PR-800) with a thickness of 0.5 μm on this flattening layer,
Exposure was carried out by selectively irradiating ultraviolet rays under the conditions of 6.6 and exposure Q30+n. Subsequently, a pattern with a width of 0.5 μm was formed on the flattened layer by development using an alkaline developer containing 5% of ions represented by the following structural formula (1).

H2H5 1+ C2H5-N-CH2S i (CH3) 3
...(r) Next, the substrate on which the pattern was formed was placed in a parallel plate type dry etching device with an oxygen gas pressure of 4 pa and an output of 0.8 W/d, and dry etching was performed using oxygen plasma. There are 4 patterns of
The resist pattern was completely transferred to the underlying flattening layer within minutes, and a fine resist pattern with a high shape ratio could be formed.

Example 2 As in Example 1, a planarizing layer was formed on a substrate, a radiation sensitive material layer was formed thereon, and exposure was performed. Subsequently, after developing with a developer containing 3% tetramethylammonium hydroxide to form a pattern with a width of 0.5 μm on the flattening layer, a pattern having the same structural formula as in Example 1 (I
) for 5 minutes. Next, when the substrate on which the pattern was formed was subjected to dry etching using oxygen plasma in the same manner as in Example 1, the entire pattern on the upper layer was transferred to the upper flattening layer in 4 minutes, resulting in a fine resist with a high shape ratio. I was able to form a pattern.

Example 3 Polyvinylphenol (Resin M) with an average molecular weight of E19600 was reacted with chloroacetic anhydride and triethylamine in tetrahydrofuran, and then added dropwise to IN hydrochloric acid, whereby 20% of the OH terminals were chloroacetylated. Resin M was prepared. Subsequently, this polymer was applied onto the flattening layer formed on the substrate in the same manner as in Example 1, and dried to form a radiation-sensitive material layer made of chloroacetylated resin M with a thickness of 0.5 μm. . Subsequently, this layer of radiation sensitive material was applied with 20 kV and 20 μC/cd.
After selective exposure to an electron beam of l
− was formed. Next, when the substrate on which the pattern was formed was subjected to dry etching using oxygen plasma in the same manner as in Example 1, the upper layer pattern was completely transferred to the lower layer flattening layer in 4 minutes, resulting in a fine resist with a high shape ratio. I was able to form a pattern.

Example 4 A 1.5 μm thick polystyrene film containing 5% of 2.6-bis-(4′-diazidobenzal)-4-methylcyclohexanone was formed on a substrate, and heated at 200° C. for 1 hour to form a flattened layer. was formed. Next, tort 4,4'-diazide diphenyl sulfone to polystyrene sulfonic acid of 2300G on average molecular weight on this (10 planarization layer).
A radiation-sensitive material layer having a thickness of 1v and 0.5 μm was formed by mixing t'u%. Subsequently, 20
After selectively irradiating and exposing to an electron beam of kV and 50 μC/cd, it was developed with a mixed solution of methyl ethyl ketone and isopropyl alcohol (mixing ratio 3; l) to form a 0.4 μm wide pattern on the flattened layer. did. After this, the pattern was immersed in a 1% Fe C1s solution for 5 minutes.

Next, the patterned substrate is exposed to an oxygen gas pressure of 4 p.
a. When the device was placed in a parallel plate dry etching device with an output of 0.8 W/d and dry etching was performed using oxygen plasma, the upper layer pattern was completely transferred to the lower flattening layer in 4 minutes, resulting in fine and fine patterns. A resist pattern with a high shape ratio could be formed.

Example 5 As in Example 4, a flattening layer was formed on a substrate, a radiation sensitive material layer was formed thereon, and exposure was performed. Next, a mixture of methyl ethyl ketone and methanol (mixing ratio 3
:Developed with a developer containing 1% FcC-3 in 1).
．． A 4 μm wide pattern was formed on the planarization layer. Next, when the substrate on which the pattern was formed was subjected to dry etching using oxygen plasma in the same manner as in Example 4, the entire pattern was transferred to the underlying flattening layer in 4 minutes.
A fine resist pattern with a high shape ratio could be formed.

Example 6 A radiation-sensitive material layer with a thickness of 0.5 μm was prepared by mixing polystyrene-poly4-vinylpyridine copolymer (copolymer ratio 3:1 with 1 offiW% of 4.4″-diazide diphenyl sulfone) in Example 4. was formed on the flattening layer in the same manner as in the above.Subsequently, this radiation sensitive material layer was applied with a voltage of 20 kV and 50 kV.
After selective exposure to an electron beam of μC/d, development was performed with a mixed solution of methyl ethyl ketone and isopropyl alcohol (mixing ratio 2:1) to form a pattern with a width of 0.3 μm on the flattening layer.

Thereafter, the pattern was immersed for 10 minutes in an aqueous solution of pH 1.5 containing 10 mmol of W(CN)s4-. Then,
When the substrate on which the pattern was formed was subjected to dry etching using oxygen plasma in the same manner as in Example 4, the entire pattern of the first layer was transferred to the underlying flattening layer in 4 minutes, resulting in a fine resist pattern with a high shape ratio. was able to form.

Example 7 A polystyrene film containing 5% of 2.8-bis-(4'-diazidobenzal)-4-methylcyclohexanone with a thickness of 1.5 μm was formed on the substrate 1-, and was heated at 200° C. for 1 hour to make it flat. A thick layer was formed. Subsequently, an ultraviolet sensitive material layer made of methyl methacrylate-methacrylic acid copolymer (copolymerization ratio 3:1) having a thickness of 0.5 μm was formed on this flattening layer. Next, apply 2QkV to this radiation sensitive material layer.
After selectively irradiating and exposing to 50 μC/d electron beam, it was developed with a mixed solution of methyl ethyl ketone and isopropyl alcohol (mixing ratio 7:3) to form a 0.2 μm wide pattern on the flattened layer. . After this, Tlt the pattern
It was immersed in a pH 3 solution containing ◆ for 5 minutes.

Next, when this substrate was subjected to dry etching using oxygen plasma in the same manner as in Example 4, the upper layer pattern was completely transferred to the lower layer flattening layer in 4 minutes, forming a fine resist pattern with a high shape ratio. I was able to do that.

Example 8 A 1.5 μm thick radiation sensitive material layer represented by the following structural formula (n) was formed on a substrate. Next, this radiation-sensitive material layer was exposed to UV light with a wavelength of 3B5 ni and an output of 200 mJ/i.
After exposure by selectively irradiating light, it was immersed for 5 minutes in a solution containing 1% of the ion represented by the structural formula (1) similar to that in Example 1. Next, oxygen gas pressure L5 pas output 0.5
When placed in a W/cIJ parallel plate type dry etching device and exposed to oxygen plasma for 1 minute, the film was 0.5μ
It was possible to develop a pattern with a width of m.

Example 9 After forming a planarization layer on a substrate in the same manner as in Example 1, a layer having a thickness of 0.5 as represented by the above structural formula (II) was formed on the planarization layer.
A radiation-sensitive material layer of μm was formed.

Subsequently, this radiation-sensitive material layer was exposed by selectively irradiating UV light with a wavelength of 365,311 and an output of 200 taJ/d, and then a layer containing 1% of ions represented by the structural formula (1) similar to Example 1 was exposed. It was immersed in the solution for 5 minutes. Next, when placed in a row-plate type dry etching apparatus with an oxygen gas pressure of 3.5 pa and an output of 0.5 W/cIJ, and exposed to oxygen plasma for 1 minute, a film with a width of 0.5 μm and a height of 2 μm was formed. We were able to form a pattern with a high aspect ratio.

Example 10 First, a radiation-sensitive material layer made of resin M with a thickness of 1.5 μm was formed on a substrate 1, and then a layer of radiation-sensitive material with a thickness of 0.5 μm was formed on this material layer.
A 2 μm polymethyl methacrylate film was formed. Next, this polymethyl methacrylate film was applied with 20 kV and 5
After selectively irradiating and exposing to an electron beam of 0 μC/c'd, methyl ethyl ketone and isopropyl alcohol are mixed? & (mixing ratio 4:l) to form a hole pattern with a width of 0.2 μm on the radiation-sensitive material layer. After this,
The pattern was immersed for 5 minutes in an aqueous solution containing 0.5% of ions having the same structural formula <1) as in Example 1. Next, this substrate was subjected to dry etching using oxygen plasma in the same manner as in Example 4, and the positive and negative patterns of the upper layer were reversed and transferred to the lower layer, with a width of 0.2 μm and a height of 1.5 μm.
A resist pattern with a high aspect ratio of m could be formed.

[Effects of the Invention] As detailed above, according to the present invention, a pattern with excellent oxygen plasma resistance can be easily produced at a relatively low cost and with good reproducibility by applying specific ions to a normal resist pattern. It can be formed on a molecular material layer (9μ planarization layer), and by using the pattern as a mask and performing dry etching with oxygen plasma, a fine two-layer resist pattern can be easily formed, which in turn can be used to fabricate fine, highly integrated semiconductor devices. It is possible to provide a pattern forming method that can be effectively used for manufacturing etc.

Claims (3)

[Claims] (1) A step of forming a polymeric material layer on a substrate, and a functional group that can be charged by attaching or desorbing protons in its structure, or a functional group that is charged as it is, on this polymeric material layer. a step of forming a layer of radiation-sensitive material containing a polymer with ions, a step of electrostatically bonding ions to the pattern after exposing the layer of radiation-sensitive material and at the same time or after development, and using the pattern as a mask to 1. A pattern forming method comprising the step of dry etching a lower polymer material layer using oxygen plasma. (2) The pattern forming method according to claim 1, wherein the polymer constituting the radiation-sensitive material has an aromatic ring to which a hydroxyl group is bonded. (3) The pattern forming method according to claim 1, wherein the ion is an ammonium compound in which a silicon atom is introduced into the molecule represented by the following general formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, R_1 to R_4 in the formula may be the same or different, and at least R_1 is an alkyl group containing a silicon atom, and the remaining R_2 to R_4 are hydrogen, an alkyl group, Indicates either an alkyl group containing a hydroxyl group or an alkyl group containing a silicon atom.