JP2006071913A - Resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a relatively thick high-resolution resist pattern with light having a short wavelength such as deep-UV light as an exposure source. <P>SOLUTION: The method comprises: a step of forming a positive chemically amplified resist film containing a polymer having hydroxyl groups and a photoacid generator on a substrate to be etched; a step of silylating the polymer in a surface of the resist film by reacting the resist film with a silicon element-containing compound in a vapor phase or in a liquid phase; a step of exposing the silylated resist film by selective irradiation with deep-UV light, an ionizing radiation or near-field light; a step of desilylating the silylated polymer in the exposed portion of the surface of the resist film by heating the resist film after the exposure in an atmosphere of water vapor; a step of selectively removing the exposed portion up to a desired depth by development; and a step of further removing a resist film part located in the exposed portion by drying etching with an oxygen-containing gas through the unexposed portion as a mask. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resist pattern forming method.

  In general, a resist pattern is formed by forming a resist film on a substrate to be etched, pattern-exposing the resist film with light having a desired wavelength, developing the exposed portion (in the case of a positive resist) or unexposed portion ( This is formed by selectively dissolving and removing a negative resist).

  The resolution limit of such a resist pattern is considered to be about ½ of the light wavelength during exposure due to the influence of light diffraction. For this reason, in order to form a fine resist pattern, it is conceivable to perform exposure using light having a short wavelength. However, as the wavelength becomes shorter, the depth of focus on the resist film during exposure becomes shallower, so that the exposure margin for a thick resist film is lowered and it becomes difficult to form a highly accurate resist pattern faithful to pattern exposure.

  For this reason, a multi-layer resist method in which a resist film has a laminated structure has been proposed, but there is a problem that the number of steps for forming a resist pattern increases.

  In order to solve the above-mentioned problem, Patent Document 1 discloses that the surface of a single resist film is silylated, the silylated layer is patterned, and the remaining resist film is used as a mask to form a lower resist film portion by oxygen plasma. A method of forming a resist pattern by removing the resist pattern is disclosed. This method is described in detail below.

  First, a resist containing a photosensitive agent such as polymethylpentene sulfone and a polymer having a hydroxyl group such as a novolac resin is applied on the substrate and dried to form a resist film. This resist film is brought into contact with the gas phase of a silicon-containing compound such as hexamethyldisilazane and reacted with the resist film surface to form a silylated layer. Subsequently, pattern exposure is performed by selectively irradiating the silylated layer of the resist film with ionizing radiation such as an electron beam. At this time, the photosensitizer present in the silylated layer is decomposed in the exposed portion to produce a decomposition product soluble in an alkali developer. Subsequently, the exposed portion of the silylated layer is selectively dissolved and removed by processing with an alkali developer such as tetramethylammonium hydroxide. Next, dry etching (for example, oxygen reactive ion etching; oxygen RIE) of a gas containing oxygen is performed. At this time, since the silylated layer remaining after the alkali development acts as a mask for oxygen RIE, the exposed portion of the resist film from which the silylated layer has been dissolved and removed is etched away and the resist pattern having the silylated layer on the surface Is formed.

  As described above, in the invention of Patent Document 1 described above, the formation of a silylated layer (silylation pattern) that acts as a mask for oxygen RIE is performed by a step of forming a silylated layer on the surface of a resist film containing a photosensitizer and by pattern exposure. The photosensitizer present in the layer is decomposed to produce a decomposition product soluble in an alkali developer, and the exposed portion of the silylated layer is selectively dissolved and removed by alkali development.

The invention of Patent Document 1 describes a chemically amplified resist containing polyphthalic aldehyde (dissolution inhibitor) and omnium salt (photoacid generator).
Japanese Patent No. 2549317

  The resolution limit of the resist pattern is considered to be about ½ of the light wavelength during exposure due to the influence of light diffraction. For this reason, in order to form a fine resist pattern, it is conceivable to perform exposure using light having a short wavelength. However, as the wavelength becomes shorter, the depth of focus on the resist film during exposure becomes shallower, so that the exposure margin for a thick resist film is lowered and it becomes difficult to form a highly accurate resist pattern faithful to pattern exposure. For this reason, a multi-layer resist method in which a resist film has a laminated structure has been proposed, but there is a problem that the number of steps for forming a resist pattern increases.

  On the other hand, when the wavelength is shortened and the vacuum ultraviolet light is used, the light transmittance of the base polymer is lowered. Therefore, an attempt has been made to use an alicyclic or fluorine polymer. However, such a polymer has problems in film formability and adhesion, and the material becomes expensive.

  In addition, since the light source to be used becomes more expensive as the wavelength becomes shorter, near-field photolithography capable of using existing g-line and i-line exposure apparatuses by simply changing the mask has been proposed. However, since the near-field light can be generated only slightly under the mask, it is difficult to form a pattern with a single layer resist. For this reason, a two-layer resist method has been proposed, but it is difficult to apply the second-layer resist thinly and uniformly on an uneven base.

  The present invention provides a method for forming a resist pattern having high resolution, high sensitivity and excellent adhesion.

According to one aspect of the invention,
Forming a positive chemically amplified resist film containing a polymer having a hydroxyl group and a photoacid generator on the substrate to be etched;
Reacting the resist film with a compound containing silicon element in a gas phase or a liquid phase to silylate the polymer on the surface of the resist film;
A step of selectively irradiating the silylated polymer layer of the resist film with deep ultraviolet light, ionizing radiation or near-field light, and exposing;
Heating the resist film after the exposure in a water vapor atmosphere to desilylate the polymer silylated in the exposed portion of the resist film surface;
Developing the resist film to selectively remove the exposed portion to a desired depth;
And a step of removing the resist film portion located in the exposed portion by dry etching using an oxygen-containing gas using the unexposed portion where the silylated polymer layer remains as a mask. A forming method is provided.

  In the method for forming a resist pattern according to the present invention, when a light source having a wavelength of 200 nm or less, such as ionizing radiation, which reduces the light transmittance of the resist, an aliphatic polymer and a hydroxyl group that dissolves in an organic solvent not having active hydrogen It is preferable to use a copolymer with an aliphatic polymer as the base polymer.

  According to the present invention, after silylating the polymer on the surface of a positive chemically amplified resist film containing a polymer having a hydroxyl group and a photoacid generator, ionization such as deep ultraviolet light, vacuum ultraviolet light, or soft X-rays is performed. Exposed to radiation or near-field light, steam heated to selectively desilylate the selectively silylated polymer, the exposed area silylated polymer and the unexposed area desilylated polymer The exposed portion is selectively dissolved and removed using a difference in solubility in the developer, and the exposed portion is selectively used using the unexposed portion where the silylated polymer layer remains as a mask for oxygen dry etching. By dry etching, deep UV light, vacuum ultraviolet light, short-wavelength light such as soft X-rays, or near-field light is used as an exposure source, and the pattern is relatively thick. It can provide a method of forming a resist pattern faithful high resolution.

  Hereinafter, a method for forming a resist pattern according to the present invention will be described in detail.

(First step)
First, a positive chemically amplified resist solution containing a polymer having a hydroxyl group and a photoacid generator is applied to the substrate to be etched and dried to form a resist film. Subsequently, the resist film is reacted (silylated) with a compound containing silicon element in a gas phase or a liquid phase to silylate the polymer on the resist film surface.

  Examples of the substrate to be etched include a silicon substrate, a compound semiconductor substrate, a glass substrate, or a substrate having a structure in which films of various metals, semiconductors, oxides thereof, nitrides, and the like are formed on these substrates.

  Examples of the positive chemically amplified resist include novolak resin, polyvinylphenol, aliphatic and alicyclic polymers having a hydroxyl group as a substituent (for example, polyacrylic acid ester or polymethacrylic acid ester of alcohol), and these And a polymer having a hydroxyl group such as a copolymer or a blend polymer containing a photoacid generator such as triphenylsulfonium hexafluoride antimony (TPS-SbF6) or diphenyliodonium salt (DPIPF6). .

In particular, when using a light source with a wavelength of 200 nm or less which is difficult to transmit light through the resist film in the exposure process described later, the polymer having a hydroxyl group is an aliphatic polymer dissolved in an organic solvent having no active hydrogen and an aliphatic having a hydroxyl group. It is preferable to use a polymer which is a copolymer with a polymer. Specific examples of this copolymer include a copolymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), And a copolymer of methyl methacrylate (MMA) and 2-hydroxyethoxyethyl methacrylate (HEtO-EMA). The copolymerization ratio of the aliphatic polymer dissolved in the organic solvent having no active hydrogen and the aliphatic polymer having a hydroxyl group is 10 to 90 mol% of the former aliphatic polymer, 90 to 10 mol% of the latter aliphatic polymer, Preferably, the former aliphatic polymer is 20 to 50 mol% and the latter aliphatic polymer is 80 to 50 mol%.
As the coating solvent for the chemically amplified resist, an organic solvent having no active hydrogen is preferably used. When an organic solvent having active hydrogen is used, there is a risk that a good silylation reaction will not proceed. Examples of the organic solvent having no active hydrogen include diethylene glycol monomethyl ether (DGM), propylene glycol monomethyl ether acetate (PGMEA), and ethyl-3-ethoxypropyl acetate (EEP).

  Examples of the compound containing silicon element (silylating agent) used in the gas phase include hexamethyldisilazane (HMDS), 1,1,3,3,5,5-hexamethylcyclotrisilazane (HMCS), and trimethylsilyldimethyl. Amine (TMSDMA), trimethylsilyldiethylamine (TMSDEA), dimethylsilyldimethylamine (DMSDMA), 1,1,4,4-tetramethyl-1,4-bisdiethylene (TMDDS), 1,2,3,4,5 , 6-hexamethylcyclotrisilazane (HMCTS), trimethylsilyl chloride (TMSC) and the like.

  Examples of the compound containing silicon element (silylating agent) used in the liquid phase include hexamethyldisilazane (HMDS), 1,1,3,3,5,5-hexamethylcyclotrisilazane (HMCS), and bisdimethyl. Examples thereof include aminodimethylsilane (B [DMA] DMS), bisdimethylaminomethylsilane (B [DMA] MS), and trimethylsilyl chloride (TMSC).

  The liquid phase preferably contains an organic solvent having no active hydrogen as a silylation accelerator. If an organic solvent having active hydrogen is used as the silylation accelerator, there is a risk that a good silylation reaction will not proceed. Examples of the silylation accelerator include diethylene glycol monomethyl ether (DGM), propylene glycol monomethyl ether acetate (PGMEA), ethyl-3-ethoxypropyl acetate (EEP), and the like.

  In order to react the compound containing silicon element with the resist film in a liquid phase, for example, a spraying method or a dipping method can be employed.

  The thickness of the silylated polymer layer formed on the resist film surface is not particularly limited, but when a resist film of about 1 μm is used, it is preferably 100 to 200 nm. However, when near-field light is used as a light source, the thickness of the silylated polymer layer is preferably 50 nm or less.

(Second step)
After exposing the silylated polymer layer on the resist film surface to deep ultraviolet light (deep UV light), ionizing radiation, or near-field light for exposure (pattern exposure), the resist film is exposed to a water vapor atmosphere. By heating, the silylated polymer in the exposed portion on the resist film surface is desilylated.

  Examples of the ionizing radiation include vacuum ultraviolet light, soft X-rays, electron beams, and ion beams.

  In the exposure, deep UV light, vacuum ultraviolet light, soft X-rays, and near-field light can be performed using a mask, which is advantageous in improving productivity.

The water vapor atmosphere is preferably 100 g / m ³ or more in absolute humidity or 19934 Pa or more in water vapor partial pressure.

  The heating (generally heating the substrate) is preferably 60 to 130 ° C. If the heating temperature is less than 60 ° C., it may be difficult to desilylate the silylated polymer in the exposed area. On the other hand, when the heating temperature exceeds 130 ° C., H of the OH group of the desilylated polymer is eliminated and crosslinking proceeds through —O—, which makes it difficult to dissolve in the developer. For this reason, there exists a possibility that the solubility difference with respect to the developing solution between the exposure part which has a desilylated polymer, and the unexposed part which has a silylated polymer may become small.

(Third step)
The exposed portion is selectively removed to a desired depth by developing the resist film after the steam heating. Subsequently, the resist pattern is formed by further selectively removing the resist film portion located in the exposed portion by performing dry etching using an oxygen-containing gas using the unexposed portion where the silylated polymer remains as an etching mask. Form.

  When the exposed portion is selectively dissolved and removed by the development (for example, wet development), it is preferable to dissolve and remove the exposed portion until a resist film portion deeper than the previously silylated surface layer is exposed.

  The wet development can be performed using, for example, an alkali developer in which tetramethylammonium hydroxide, tetraethylammonium hydroxide, or ammonia is dissolved in water or alcohol. As the developing means, for example, a spray developing method or a dipping developing method can be employed.

Examples of the oxygen-containing gas include oxygen alone, a mixed gas of oxygen and an inert gas such as argon, or a mixed gas of oxygen and a gas such as CO, CO ₂ , NH ₃ , N ₂ O, and SO _2. Can be used.

  As the dry etching using the oxygen-containing gas, for example, oxygen plasma etching performed in an atmosphere in which oxygen is converted into plasma, or a substrate to be etched having a resist film disposed on one electrode while oxygen is converted into plasma between parallel plate electrodes Oxygen reactive ion etching (oxygen RIE) in which etching is performed by accelerating oxygen ions toward the surface can be employed.

  According to the present invention described above, a single positive chemically amplified resist and short wavelength light such as deep UV light or ionizing radiation (for example, vacuum ultraviolet light, soft X-ray), or near-field light is used as an exposure source. As a result, a resist pattern having a relatively large thickness and a high resolution can be formed.

  Hereinafter, the operation of the method of the present invention will be specifically described by taking as an example a positive chemically amplified resist having a composition containing polyvinylphenol (polymer) and diphenyliodonium salt (photoacid generator).

  When the chemically amplified resist film formed on the substrate to be etched is reacted (silylated) with a compound containing silicon element (for example, hexamethyldisilazane) in a gas phase, as shown in the following chemical formula 1, -OH of polyvinylphenol The group H is eliminated and trimethylsilane is bonded to -O-, and the polymer on the resist film surface is silylated. At this time, by using the chemically amplified resist, it becomes possible to increase the contrast of the boundary between the silylated portion / unsilylated portion in the thickness direction of the resist film, that is, to form a clear boundary.

When the resist film is subjected to pattern exposure through, for example, deep UV light or near-field light through a mask, the photoacid generator in the resist film is decomposed and acid is generated in the exposed portion as shown in Chemical Formula 1 below. When heated in a water vapor atmosphere after pattern exposure, the acid generated in the exposed area as shown in the following chemical formula 1 acts on trimethylsilane bonded to -O- of the polyvinylphenol with the help of heat and water vapor to remove it. Silylation is performed and trimethylsilanol is eliminated. That is, the already silylated polymer in the exposed area changes to the original polyvinylphenol chemical structure. Due to such desilylation in the exposed area, a large difference in solubility occurs in the developing solution between the exposed area and the unexposed area where the silylated polymer remains, that is, the chemical structure changes so that the exposed area is easily dissolved. Made.

  After the desilylation, the exposed portion is selectively removed to a desired depth (preferably a depth corresponding to the silylated layer) by wet development with a developer such as tetramethylammonium hydroxide. Thereafter, by performing dry etching using an oxygen-containing gas, the unexposed portion where the silylated polymer remains acts as an etching mask, and the resist film portion exposed from the mask is selectively etched away. A resist pattern can be formed.

  In forming such a resist pattern, it is necessary to selectively dissolve and remove the exposed portion to a desired depth (preferably a depth corresponding to the silylated layer) by wet development after desilylation. This is because when dry etching is performed using an oxygen-containing gas without performing wet development after desilylation, etching is performed between an exposed portion having a desilylated polymer and an unexposed portion in which the silylated polymer remains. This is because it becomes difficult to obtain a sufficient selection ratio.

  In fact, the etching depth of the resist film in which the silylated polymer exists on the surface and the resist film in which the unsilylated polymer exists on the surface with respect to the etching time by dry etching (for example, oxygen RIE) using the oxygen-containing gas is illustrated. It is shown in 1. In FIG. 1, a is an etching characteristic line of a resist film having an unsilylated polymer on the surface, and b is an etching characteristic line of a resist film having a silylated polymer on the surface. From FIG. 1, by setting the etching time from about 20 minutes to about 40 minutes, the layer where the silylated polymer exists on the surface acts as an etching mask without disappearing by etching, and the thickness located at the exposed portion. It can be seen that an unsilylated resist film of about 1 μm (1000 nm) can be removed by etching. That is, a sufficient etching margin can be taken in an unexposed portion where a polymer silylated in oxygen RIE remains.

  Therefore, according to the present invention, by using short-wavelength light such as deep UV light or electron beam, or near-field light as an exposure source from a single positive-type chemically amplified resist, A high-resolution resist pattern that is faithful to the pattern at the time of exposure can be formed.

  In addition, if the heat treatment is simply performed after the pattern exposure (heat treatment in a dry atmosphere), the substitution reaction (desilylation reaction) of the trimethylsilane group and H group bonded to —O— of the polymer is not sufficient, The polymer undergoes a cross-linking reaction through —O—, and the solubility of the exposed portion in the developer is lowered. As a result, it becomes difficult to form a high-resolution resist pattern.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS.

Example 1
First, polyvinylphenol (polymer) and diphenyliodonium salt (photoacid generator) were dissolved in diethylene glycol dimethyl ether to prepare a positive chemically amplified resist solution. Subsequently, this resist solution was applied onto the substrate 1 as shown in FIG. 2A and dried to form a positive resist film 2 having a thickness of 1 μm. Thereafter, the resist film was baked at 70 ° C. for 10 minutes.

  A chamber having a built-in plate-shaped heater and having an exhaust portion with a heater arranged on the outer periphery was prepared, and the resist film-coated substrate was placed on the plate-shaped heater in the chamber. Subsequently, the heater and the plate heater are heated to heat the inside of the chamber and the substrate to 70 ° C., respectively, and the inside of the chamber is evacuated through the exhaust section. Then, hexamethyldisilazane (silicon-containing compound) HMDS) was introduced into the chamber until it reached 85-100 mTorr. The resist film is exposed to an atmosphere of HMDS for 20 to 40 minutes and reacted with HMDS on the resist film surface, whereby the thickness of the polyvinyl phenol silylated on the resist film 2 surface as shown in FIG. A silylated layer 3 of 50 to 80 nm was formed.

Next, the substrate is taken out from the chamber, and as shown in FIG. 2C, deep UV light is patterned on the silylated layer 3 of the resist film on the substrate 1 through the exposure mask 4 at an exposure amount of 7 mJ / cm ^2. Exposure was performed. At this time, an acid was generated from the photoacid generator present in the exposed portion of the silylated layer 3 to form the acid generating portion 5 on the resist film 2. Subsequently, the resist film is heat-treated at 80 to 130 ° C. in a water vapor atmosphere (absolute humidity of 130 g / m ³ or more) for 5 to 20 minutes, thereby forming an acid as an exposed portion as shown in FIG. The generation part was desilylated to form a desilylated layer 6.

  Next, the exposed portion was removed by selectively dissolving and removing the desilylated layer 6 by developing the resist film with an aqueous tetramethylammonium hydroxide solution having a concentration of 1.5 to 2.0%. At this time, as shown in FIG. 3E, the level difference of the dissolved portion 8 between the unexposed portions 7 where the silylated polymer remains was smaller than 300 nm. Subsequently, oxygen reactive ion etching was performed to convert oxygen into plasma and accelerate the oxygen ions. At this time, since the unexposed portion 7 where the silylated polymer remains acts as a mask for oxygen RIE, the exposed portion of the resist film 2 from which the desilylated layer has been dissolved and removed is etched away, as shown in FIG. As shown in F), a resist pattern 9 was formed.

  The obtained resist pattern had high resolution faithful to the pattern at the time of exposure.

In addition, when a resist film having a silylated layer is subjected to pattern exposure with deep UV light, the step of the resist film dissolution portion after development can be reduced to 300 nm or less with an exposure amount of 7 mJ / cm ² . Even when compared with the sensitivity (10 to 20 mJ / cm ² ), the sensitivity was sufficient.

(Example 2)
First, a positive chemically amplified resist solution was prepared by dissolving polyvinylphenol (polymer) and triphenylsulfonium salt (photoacid generator) in diethylene glycol dimethyl ether. Subsequently, the resist solution was applied onto the substrate 1 and dried to form a positive resist film 2 having a thickness of 1 μm, as in FIG. Thereafter, the resist film was baked at 70 ° C. for 10 minutes.

  After immersing the substrate having the resist film in a silylation solution composed of silicon-containing compound hexamethylcyclosilylsilazane (HMCTS), diethylene glycol dimethyl ether and n-decane for 2 minutes and reacting with the HMCTS on the resist film surface, By rinsing twice in n-decane for 4 minutes each, a silylated layer 3 having a thickness of 100 to 210 nm in which polyvinylphenol is silylated is formed on the surface of the resist film 2 as in FIG. did. The silylation operation was performed in a dry box filled with dry nitrogen.

Next, the substrate is taken out of the dry box, and in the same manner as in FIG. 2C, the exposure amount of 5 mJ / cm ² is passed through deep UV light through the exposure mask 4 to the silylated layer 3 of the resist film on the substrate 1. Then, pattern exposure was performed. At this time, an acid was generated from the photoacid generator present in the exposed portion of the silylated layer 3 to form the acid generating portion 5 on the resist film 2. Subsequently, the resist film is heat-treated at 120 ° C. under a water vapor atmosphere (absolute humidity of 130 g / m ³ or more) for 5 to 20 minutes, thereby generating an acid which is an exposed portion as in FIG. The portion was desilylated to form a desilylated layer 6.

  Next, the exposed portion was removed by selectively dissolving and removing the desilylated layer 6 by developing the resist film with an aqueous tetramethylammonium hydroxide solution having a concentration of 1.5 to 2.0%. At this time, as in the case of (E) in FIG. 3 described above, the level difference of the dissolved portion 8 between the unexposed portions 7 where the silylated polymer remained was 200 nm. Subsequently, oxygen reactive ion etching was performed to convert oxygen into plasma and accelerate the oxygen ions. At this time, since the unexposed portion 7 where the silylated polymer remains functions as a mask for oxygen RIE, the exposed portion of the resist film 2 from which the desilylated layer has been dissolved and removed is etched away, and the above-described FIG. As in (F), a resist pattern 9 was formed.

  The obtained resist pattern had high resolution faithful to the pattern at the time of exposure, and had sufficient resistance necessary for processing the electronic element substrate by dry etching and a thickness of 1 μm or more.

(Example 3)
First, a positive chemically amplified resist solution was prepared by dissolving polyvinylphenol (polymer) and triphenylsulfonium salt (photoacid generator) in diethylene glycol dimethyl ether. Subsequently, the resist solution was applied onto the substrate 1 and dried to form a positive resist film 2 having a thickness of 1 μm, as in FIG. Thereafter, the resist film was baked at 70 ° C. for 10 minutes.

  After immersing the substrate having the resist film in a silylation solution consisting of silicon-containing compound tetramethyldisilazane (TMDS), diethylene glycol dimethyl ether and n-decane for 2 minutes and reacting with the TMDS on the resist film surface, By rinsing twice for 4 minutes each in n-decane, a silylated layer 3 having a thickness of 100 to 250 nm in which polyvinylphenol is silylated is formed on the surface of the resist film 2 in the same manner as in FIG. did. The silylation operation was performed in a dry box filled with dry nitrogen.

Next, the substrate is taken out of the dry box, and in the same manner as in FIG. 2C, the exposure amount of 5 mJ / cm ² is passed through deep UV light through the exposure mask 4 to the silylated layer 3 of the resist film on the substrate 1. Then, pattern exposure was performed. At this time, an acid was generated from the photoacid generator present in the exposed portion of the silylated layer 3 to form the acid generating portion 5 on the resist film 2. Subsequently, the resist film is heat-treated at 120 ° C. under a water vapor atmosphere (absolute humidity of 130 g / m ³ or more) for 5 to 20 minutes, thereby generating an acid which is an exposed portion as in FIG. The portion was desilylated to form a desilylated layer 6.

  Next, the exposed portion was removed by selectively dissolving and removing the desilylated layer 6 by developing the resist film with an aqueous tetramethylammonium hydroxide solution having a concentration of 1.5 to 2.0%. At this time, as in the case of (E) in FIG. 3 described above, the level difference of the dissolved portion 8 between the unexposed portions 7 where the silylated polymer remained was 200 nm. Subsequently, oxygen reactive ion etching was performed to convert oxygen into plasma and accelerate the oxygen ions. At this time, since the unexposed portion 7 where the silylated polymer remains functions as a mask for oxygen RIE, the exposed portion of the resist film 2 from which the desilylated layer has been dissolved and removed is etched away, and the above-described FIG. As in (F), a resist pattern 9 was formed.

  The obtained resist pattern had high resolution faithful to the pattern at the time of exposure, and had sufficient resistance necessary for processing the electronic element substrate by dry etching and a thickness of 1 μm or more.

  In Example 2 in which hexamethylcyclosiliclazane (HMCTS) is used in the silylation process, a residue tends to be generated after oxygen reactive ion etching. In HMCTS, since two nitrogen atoms (N) are bonded to Si in the structure, it is considered that polyvinylphenol molecular chains are cross-linked with each other and are not easily wet-developed. On the other hand, in Example 3, since tetramethyldisilazane (TMDS) used in the silylation process is bonded with only one nitrogen atom (N) to Si in the structure, and no cross-linking reaction occurs, patterning characteristics are improved. It is thought to improve.

Example 4
First, a positive chemically amplified resist solution is prepared by dissolving a copolymer of an aliphatic polymer, methyl methacrylate and 2-hydroxyethyl methacrylate, and diphenyliodonium salt (photoacid generator) in diethylene glycol dimethyl ether. did. Subsequently, the resist solution was applied onto the substrate 1 and dried to form a positive resist film 2 having a thickness of 1 μm, as in FIG. Thereafter, the resist film was baked at 70 ° C. for 10 minutes.

  The substrate having the resist film is immersed in a silylation solution heated to 110 ° C. composed of silicon-containing compound hexamethyldisilazane (HMDS), diethylene glycol dimethyl ether and n-decane for 5 minutes. After the reaction, by rinsing twice for 4 minutes each in n-decane, the same weight of methyl methacrylate and 2-hydroxyethyl methacrylate is formed on the surface of the resist film 2 as in FIG. A silylated layer 3 having a thickness of 200 nm in which the coalescence was silylated was formed. The silylation operation was performed in a dry box filled with dry nitrogen.

Next, the substrate is taken out of the dry box, and similarly to the case of FIG. 2C described above, vacuum ultraviolet light is exposed to the silylated layer 3 of the resist film on the substrate 1 through the exposure mask 4 at an exposure of 5 mJ / cm ² . Pattern exposure was performed in the amount. At this time, an acid was generated from the photoacid generator present in the exposed portion of the silylated layer 3 to form the acid generating portion 5 on the resist film 2. Subsequently, the resist film is heat-treated at 120 ° C. under a water vapor atmosphere (absolute humidity of 130 g / m ³ or more) for 5 to 20 minutes, thereby generating an acid which is an exposed portion as in FIG. The portion was desilylated to form a desilylated layer 6.

  Next, the exposed portion was removed by selectively dissolving and removing the desilylated layer 6 by developing the resist film with an aqueous tetramethylammonium hydroxide solution having a concentration of 1.5 to 2.0%. At this time, as in the case of (E) in FIG. 3 described above, the level difference of the dissolved portion 8 between the unexposed portions 7 where the silylated polymer remained was 200 nm. Subsequently, oxygen reactive ion etching was performed to convert oxygen into plasma and accelerate the oxygen ions. At this time, since the unexposed portion 7 where the silylated polymer remains functions as a mask for oxygen RIE, the exposed portion of the resist film 2 from which the desilylated layer has been dissolved and removed is etched away, and the above-described FIG. As in (F), a resist pattern 9 was formed.

  The obtained resist pattern had high resolution faithful to the pattern at the time of exposure, and had sufficient resistance necessary for processing the electronic element substrate by dry etching and a thickness of 1 μm or more. Moreover, there was no problem about film forming property and adhesiveness.

(Example 5)
First, a positive chemically amplified resist solution was prepared by dissolving polyvinylphenol (polymer) and triphenylsulfonium salt (photoacid generator) in diethylene glycol dimethyl ether. Subsequently, the resist solution was applied onto the substrate 1 and dried to form a positive resist film 2 having a thickness of 1 μm, as in FIG. Thereafter, the resist film was baked at 70 ° C. for 10 minutes.

  A substrate having the resist film in a silylation solution heated to 110 ° C. composed of 30% of hexamethyldisilazane (HMDS) which is a silicon-containing compound, 1.5% of diethylene glycol dimethyl ether as a silylation accelerator and n-decane is 1 After immersing for a minute and reacting with HMDS on the surface of the resist film, rinsing twice in n-decane for 1 minute each to form methyl methacrylate on the surface of the resist film 2 as in FIG. A silylated layer 3 having a thickness of 50 nm in which a copolymer of 2-hydroxyethyl methacrylate was silylated was formed. The silylation operation was performed in a dry box filled with dry nitrogen.

Next, the substrate is taken out of the dry box, and, as in the case of FIG. 2C, the near-field light is exposed to the silylated layer 3 of the resist film on the substrate 1 through the exposure mask 4 at an exposure of 5 mJ / cm ² . Pattern exposure was performed in the amount. At this time, an acid was generated from the photoacid generator present in the exposed portion of the silylated layer 3 to form the acid generating portion 5 on the resist film 2. Subsequently, the resist film is heat-treated at 120 ° C. under a water vapor atmosphere (absolute humidity of 130 g / m ³ or more) for 5 to 20 minutes, thereby generating an acid which is an exposed portion as in FIG. The portion was desilylated to form a desilylated layer 6.

  Next, the exposed portion was removed by selectively dissolving and removing the desilylated layer 6 by developing the resist film with an aqueous tetramethylammonium hydroxide solution having a concentration of 1.5 to 2.0%. At this time, as in the case of FIG. 3E described above, the level difference of the dissolved portion 8 between the unexposed portions 7 where the silylated polymer remained was 50 nm. Subsequently, oxygen reactive ion etching was performed to convert oxygen into plasma and accelerate the oxygen ions. At this time, since the unexposed portion 7 where the silylated polymer remains functions as a mask for oxygen RIE, the exposed portion of the resist film 2 from which the desilylated layer has been dissolved and removed is etched away, and the above-described FIG. As in (F), a resist pattern 9 was formed.

  The obtained resist pattern had high resolution faithful to the pattern at the time of exposure, and had sufficient resistance necessary for processing the electronic element substrate by dry etching and a thickness of 1 μm or more. Moreover, there was no problem about film forming property and adhesiveness.

  In Examples 4 and 5 described above, even when silylation in the gas phase is performed instead of silylation in the liquid phase, the high resolution faithful to the pattern at the time of exposure is obtained, as in these examples. In addition, it is possible to form a resist pattern having sufficient resistance necessary for processing the electronic element substrate by dry etching and a thickness of 1 μm or more.

The relationship between the etching depth of the resist film in which the unsilylated polymer exists only on the surface and the resist film in which the silylated polymer exists on the surface with respect to the etching time in dry etching (for example, oxygen RIE) using an oxygen-containing gas. FIG. Sectional drawing which shows the formation process of the resist pattern in Example 1 of this invention. Sectional drawing which shows the formation process of the resist pattern in Example 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Resist film, 3 ... Silylated layer, 6 ... Desilylated layer, 7 ... Unexposed part, 9 ... Resist pattern.

Claims (6)

Forming a positive chemically amplified resist film containing a polymer having a hydroxyl group and a photoacid generator on the substrate to be etched;
Reacting the resist film with a compound containing silicon element in a gas phase or a liquid phase to silylate the polymer on the surface of the resist film;
A step of selectively irradiating the silylated polymer layer of the resist film with deep ultraviolet light, ionizing radiation or near-field light, and exposing;
Heating the resist film after the exposure in a water vapor atmosphere to desilylate the polymer silylated in the exposed portion of the resist film surface;
Developing the resist film to selectively remove the exposed portion to a desired depth;
And a step of removing the resist film portion located in the exposed portion by dry etching using an oxygen-containing gas using the unexposed portion in which the silylated polymer layer remains as a mask. Method.   When the exposure light source having a wavelength of 200 nm or less is used, the polymer having a hydroxyl group is composed of 10 to 90 mol% of an aliphatic polymer dissolved in an organic solvent having no active hydrogen and 90 to 10 mol% of an aliphatic polymer having a hydroxyl group. 2. The method for forming a resist pattern according to claim 1, wherein the resist pattern is a copolymer.   2. The method of forming a resist pattern according to claim 1, wherein the coating solvent for the chemically amplified resist is an organic solvent having no active hydrogen.   2. The process of silylating the resist film with a compound containing silicon element in a liquid phase, wherein the liquid phase contains an organic solvent having no active hydrogen as a silylation accelerator. Of forming a resist pattern.   The method for forming a resist pattern according to claim 1, wherein the heating in the water vapor atmosphere is performed at a temperature of 60 to 130 ° C. The method for forming a resist pattern according to claim 1, wherein the water vapor atmosphere is 100 g / m ³ or more in absolute humidity.

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