JP2002296791A - Method for forming pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a pattern by which a resist film can be made thin by using a lower layer film formed by a coating method, the required mask thickness is maintained, and the difference caused by conversion in processes is suppressed to process the objective film with high dimensional accuracy. SOLUTION: The method includes a process of applying a solution containing a compound having silicon and nitrogen couplings in the main chain on the objective film (2) to be treated to form a base layer film (3), a process of substituting nitrogen in the lower layer film with oxygen, a process of forming a resist film (5) on the lower layer film, a process of exposing and developing the resist film to form a resist pattern (6), a process of transferring the resist pattern to the lower layer film to form a lower layer film pattern (7), and a process of transferring the lower layer film pattern to the objective film to form the objective film pattern (8).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a pattern, and more particularly to a method for forming a fine pattern on a wafer substrate in manufacturing a semiconductor device.

[0002]

2. Description of the Related Art A method of manufacturing a semiconductor device includes many steps of depositing a plurality of substances as a film to be processed on a silicon wafer to form thin films, and patterning each thin film into a desired pattern. In patterning the film to be processed, first, a photosensitive material generally called a resist film is deposited on the film to be processed to form a resist film, and a predetermined region of the resist film is exposed. Next, the exposed portion or the unexposed portion of the resist film is removed by a development process to form a resist pattern, and the film to be processed is dry-etched using the resist pattern as an etching mask.

As an exposure light source for exposing a predetermined region of a resist film to light, KrF
Ultraviolet light such as an excimer laser and an ArF excimer laser has been used. Recently, with the miniaturization of LSIs, the required resolution has become smaller than the exposure wavelength, and the exposure process latitude such as the exposure latitude and the focus latitude has become insufficient. To compensate for these process margins, it is effective to reduce the thickness of the resist film to improve the resolution. However, in that case, there arises a problem that the resist film thickness required for etching the film to be processed cannot be secured.

In order to solve such a problem, a method has been proposed in which a resist pattern is temporarily transferred to a silicon oxide film to form a silicon oxide film pattern. In this method, the pattern is transferred by dry-etching the film to be processed using the formed silicon oxide film pattern as an etching mask. As the silicon oxide film, spin-on-glass which can be formed by a coating method such as spin coating which can be formed at low cost without requiring a vacuum system is used. However, since spin-on-glass is formed by a coating method, it is difficult to obtain a high-density film as compared with a physicochemical film forming method such as a CVD method or a sputtering method. Therefore, as compared with a silicon oxide film formed by a physicochemical method, spin-on-glass has a problem that etching resistance is low and a processing conversion difference is likely to occur during etching of a film to be processed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and has been made to reduce the thickness of a resist film by using a lower layer film that can be formed by a coating method and secure a necessary mask thickness. An object of the present invention is to provide a pattern forming method capable of processing a film to be processed with high dimensional accuracy by suppressing a processing conversion difference.

[0006]

In order to solve the above problems, the present invention provides a method of forming a lower layer film by applying a solution containing a compound having a bond between silicon and nitrogen in a main chain on a film to be processed. Forming a resist film on the lower film, forming a resist pattern on the lower film, and performing a pattern exposure and development process on the resist film to form a resist pattern. And transferring the resist pattern to the lower film to form a lower film pattern, and transferring the lower film pattern to the film to be processed to form a film pattern to be processed. A method of forming is provided.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pattern forming method according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a process sectional view showing an example of a pattern forming method according to the present invention.

First, as shown in FIG. 1A, a lower film 3 is formed on a film 2 to be processed on a wafer. The processed film 2 in the present invention can be formed directly on a wafer or via a thin film such as an interlayer insulating film. Therefore, reference numeral 1 in FIG. 1 represents a wafer or a film immediately below the film 2 to be processed. The film to be processed 2 is not particularly limited as long as it can be etched with a high selectivity to silicon oxide, and can be made of any material. For example, aluminum, aluminum silicide,
Copper, wiring materials such as tungsten, titanium, titanium nitride, etc., electrode materials such as polysilicon, tungsten silicide, cobalt silicide, ruthenium, amorphous silicon, silicon-based materials such as silicon substrates, and organic interlayer insulation such as polyimide and polyarylene ether A film, a lower resist film used in a multi-layer resist film process such as a novolak resin, polyimide, polyacenaphthylene, polyarylene, polyarylene ether, or the like can be formed as the film 2 to be processed.

In particular, in the present invention, it is preferable to form the processed film 2 from an organic interlayer insulating film or an organic material made of a compound having carbon such as a multilayer resist film process. This is because a film to be processed formed from such an organic material can be processed with high selectivity to the lower layer film 3 formed thereon. In this case, the content of carbon in the film to be processed 2 is preferably 30% by weight or more. If the amount is less than 30 wt%, it becomes difficult to process the target film 2 with selectivity to the lower film 3.

On the film 2 to be processed, a lower film 3 is formed by a method of applying a solution. The coating method does not require a vacuum system, and can be formed at low cost because the process is simple.

Here, a method of forming a lower layer film by a coating method will be described in detail. First, a silicon compound having a bond between silicon and nitrogen in its main chain is dissolved in a solvent to prepare a solution material. Examples of the silicon compound having a bond between silicon and nitrogen in the main chain include polysilazane represented by the following general formula.

[0013]

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(Here, R ¹¹ , R ¹² and R ¹³ represent a nitrogen atom, a hydrogen atom or a substituted or unsubstituted aliphatic hydrocarbon or aromatic hydrocarbon having 1 to 20 carbon atoms. N Is an integer.)

In the present invention, the polysilazane used for forming the underlayer film may be a homopolymer or a copolymer, and two or more kinds of polysilazane may be an oxygen atom, a nitrogen atom,
Those having a structure bonded to each other via an aliphatic group or an aromatic group may be used. Further, these compounds may include a bond between silicon and silicon or a bond between silicon and oxygen.

The content of silicon in the silicon compound is preferably in the range of 5 to 80 wt%, and the content of nitrogen is preferably in the range of 5 to 80 wt%. If the contents of silicon and nitrogen are less than 5 wt%, it becomes difficult to obtain sufficient etching resistance. On the other hand, if it exceeds 80 wt%, the applicability may be deteriorated. Specific examples of the polysilazane that can be used in the present invention include compounds represented by the following chemical formula.

[0017]

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[0018]

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[0019]

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[0020]

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(In the formula, m and n represent positive integers.)

The weight-average molecular weight of these silicon compounds is not particularly limited.
0 is preferred. The reason is that if the molecular weight is less than 200,
The underlayer film was dissolved in the solvent of the resist.
If it exceeds 000, it is difficult to dissolve in a solvent, and it becomes difficult to prepare a solution material. The silicon compound is not limited to one kind, and several kinds of compounds can be mixed and used.

By dissolving the silicon compound as described above in a predetermined solvent, a coating material for the underlayer film is prepared. The solvent is not particularly limited, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, methyl cellosolve,
Cellosolve solvents such as methyl cellosolve acetate and ethyl cellosol acetate; ester solvents such as ethyl lactate, ethyl acetate, butyl acetate and isoamyl acetate; alcohol solvents such as methanol, ethanol, and isopropanyl; and other anisoles, toluene, Xylene, naphtha and the like can be mentioned.

Further, if necessary, a thermal polymerization inhibitor for improving the storage stability, an adhesion enhancer for improving the adhesion to the film to be processed, and a light reflected from the film to be processed into the resist film. UV-absorbing dyes, polysulfone, polybenzimidazole or other UV-absorbing polymers, conductive substances to prevent electric charge from being accumulated in the resist film during electron beam exposure, conductivity due to light and heat A substance, a crosslinking agent capable of crosslinking a silicon compound for imparting solvent resistance and heat resistance, and a radical generator for promoting crosslinking may be added to the solution material.

The coating material prepared as described above is coated on the film to be processed 2 by, for example, a spin coating method or the like to form a coating film. Next, the solvent is vaporized by heating to form the lower layer film 3. The thickness of the lower film 3 formed here is preferably in the range of 1 to 1000 nm. If the film thickness of the lower layer film 3 is less than 1 nm, it is difficult to secure a film thickness as a mask material for etching the film 2 to be processed. On the other hand, when the resist pattern is thicker than 1000 nm, when the resist pattern is transferred to the lower layer film by the dry etching method, a dimensional conversion difference may be significantly generated.

Next, nitrogen in the lower film 3 is replaced with oxygen. In a silicon compound having a bond between silicon and nitrogen in its main chain, nitrogen is desorbed by heating or irradiation of an energy beam as shown in the following reaction formula, and oxygen is bonded to a dangling bond from silicon generated. As a result, a silicon oxide-like film 4 as shown in FIG. 1B is obtained. In the course of the substitution reaction from nitrogen to oxygen, the lower film becomes denser, so that a high-density film can be obtained.

[0027]

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The replacement ratio of nitrogen to oxygen is preferably at least 20%, more preferably at least 80%, based on the nitrogen content of the silicon compound in the solution. If the substitution rate is less than 20%, the etching resistance of the lower layer film cannot be sufficiently improved due to insufficient substitution. Since nitrogen and oxygen are required for the progress of the substitution reaction, heating or irradiation with an energy beam
It is desired to perform the process while exposing the lower layer film to an atmosphere containing moisture and oxygen. In this case, the humidity in the atmosphere is 10%
The oxygen concentration is preferably at least 10%. When the humidity and oxygen concentration of the atmosphere are 10% or more, the substitution reaction from nitrogen to oxygen can proceed efficiently and sufficiently, and a high-density film can be obtained.

When nitrogen is replaced by oxygen by heating, the temperature is preferably 200 ° C. or more and 500 ° C. or less. If the temperature is lower than 200 ° C., the substitution reaction from nitrogen to oxygen becomes difficult to proceed. On the other hand, if the temperature exceeds 500 ° C., the film to be processed 2 may be deteriorated. Heating at such a temperature can be performed using a hot plate, an oven, or the like, and multi-stage baking may be performed.

When the energy beam is applied to replace nitrogen in the lower film with oxygen, light having a wavelength in the range of 1 nm to 1 mm or an electron beam can be used. As light, 100 nm to 800
Light containing wavelengths in the nm range is particularly preferred. The dose of such light and electron beam is not limited,
When irradiating light, the irradiation amount is 1 mJ / cm ² -100
The range is preferably 0 J / cm ² , and when irradiating with an electron beam, the range is preferably 1 μC / cm ^{2 to} 1000 C / cm ² . In any case, when the irradiation amount is less than the lower limit described above, it is difficult to sufficiently promote the substitution reaction from nitrogen to oxygen. On the other hand, if the upper limit is exceeded, the irradiation may take a long time and the throughput may be reduced. Also,
Heating and energy beam irradiation may be performed simultaneously to replace nitrogen in the lower film with oxygen.

A resist solution is applied on the lower layer film 4 densified by replacing nitrogen with oxygen by a spin coating method or the like, and is heated to evaporate the solvent. As shown, a resist film 5 is formed. When the thickness of the resist film 5 is reduced, the exposure latitude, the focus latitude, or the resolution can be improved. Therefore, the thickness of the resist film 5 is preferably as small as possible as long as the lower layer 4 can be etched with good dimensional control. Specifically, the thickness of the resist film 5 is preferably in the range of 100 to 10000 nm, and more preferably in the range of 100 to 400 nm. If the thickness of the resist film 5 is less than 100 nm, it is difficult to perform the lower layer film with good dimensional controllability. On the other hand, if it exceeds 10,000 nm, the lithography process window may be deteriorated.

The resist composition for forming the resist film 5 is not particularly limited as long as it is a composition that can be patterned by exposure to visible light, ultraviolet light, or the like. A negative type can be selected and used. Specifically, as the positive resist, for example, a resist composition (IX-770, manufactured by JSR) containing naphthoquinonediazide and a novolak resin, a polyvinylphenol resin protected with t-BOC, a photoacid generator, And a resist composition containing a polymethacrylate protected with an aliphatic hydrocarbon group and an acid generator, and the like. Examples of the negative resist film include, for example, a chemically amplified resist (SNR248, manufactured by Shipley Co., Ltd.) containing polyvinylphenol, a melamine resin, and a photoacid generator, and a resist containing polyvinylphenol and a bisazide compound (SNR248). RD-2000D, manufactured by Hitachi Chemical Co., Ltd.), but are not limited thereto.

After applying such a resist solution on the lower layer film 4 by, for example, a spin coating method or the like, the resist film 5 is formed by evaporating the solvent by heating on a hot plate or an oven or the like.

Next, pattern exposure is performed on the resist film 5. The light source of the exposure light is not particularly limited, and examples thereof include ultraviolet light, X-rays, an electron beam, and an ion beam. Specifically, as ultraviolet light, g-line (wavelength = 436 nm), i-line (365 nm), XeF (wavelength = 351 nm), XeCl (wavelength =
308 nm), KrF (wavelength = 248 nm), KrCl
(Wavelength = 222 nm), ArF (wavelength = 193 nm),
And excimer lasers such as F ₂ (wavelength = 157 nm). The resist film after the exposure may be subjected to post-exposure baking as needed.

Thereafter, development processing is carried out using an aqueous solution of an inorganic alkali such as an aqueous solution of tetramethylammonium, sodium hydroxide and potassium hydroxide, or an organic solvent such as xylene and acetone, as shown in FIG. Such a resist pattern 6 is formed.

If necessary, an upper anti-reflection film for reducing multiple reflections in the resist film generated when performing light exposure, or an upper layer anti-reflection film for preventing charge-up generated when performing electron beam exposure. The prevention film may be formed on the resist film 5.

Since the lower layer film 4 formed in the present invention has a high polarity, the developing solution permeates between the resist pattern 6 and the lower layer film 4, and the resist pattern 6
May come off from the lower film 4. In this case, by subjecting the lower layer film to a hydrophobic treatment, the developer hardly permeates between the resist pattern and the lower layer film, and the resist pattern can be prevented from peeling off from the lower layer film. Examples of the hydrophobic treatment include a method in which the lower layer film is exposed to an atmosphere in which hexamethyldisilazane is evaporated, and a hydroxyl group on the surface of the lower layer film is substituted with a methyl group.

By performing the hydrophobic treatment, by-products such as ammonia may be generated. It is desired that such by-products are removed by baking at about 150 to 500 ° C. By baking in this range, by-products can be sufficiently removed without deteriorating the underlying film. The upper limit of the baking temperature is
The temperature is more preferably set to 350 ° C. or lower. Baking for removing by-products can be performed using a hot plate or an oven or the like, and multi-stage baking may be performed.

When the resist film 5 is formed of a chemically amplified resist, the resist profile may be deteriorated due to the presence of a basic substance. For example, if a basic substance remains in the lower film 4, the resist film 5
In this case, the acid generated by the exposure is deactivated. In order to prevent this, it is preferable that the lower layer film immediately before the formation of the resist film 5 is subjected to a heat treatment at a temperature of 150 ° C. or higher to volatilize the basic substance and thereby remove the basic substance from the lower layer film. In this case, the upper limit of the temperature is 500 ° C. or less, and 3
The temperature is preferably set to 50 ° C. or lower. If the temperature exceeds 500 ° C., the film to be processed may be deteriorated. Baking at such a temperature can be performed using a hot plate, an oven, or the like, and multi-stage baking may be performed.

In the case where the adhesion between the resist pattern 6 and the lower layer film 4 cannot be obtained even by employing the above-described method,
Alternatively, when the basic substance remaining in the lower film 4 cannot be sufficiently volatilized, a thin film (not shown) is formed on the lower film, and then a resist film 5 is applied on the thin film to form a resist pattern. Is also good. In this case, the thin film is preferably as thin as possible in order to suppress a processing conversion difference when the thin film is etched, and is preferably 5 to 500 nm, more preferably 10 to 10 nm.
A range of 0 nm is preferred. Examples of such a thin film include polymethyl siloxane, polymethyl methacrylate, and polysulfone. From the viewpoint of throughput, it is preferable to form the thin film by a coating method.

Using the obtained resist pattern 6 as a mask, the lower layer film 4 is dry-etched, whereby the pattern shape of the resist pattern 6 is transferred to the lower layer film, and the lower layer film as shown in FIG. The pattern 7 is formed. As the etching method, for example, reactive ion etching, magnetron type reactive ion etching,
There is no particular limitation as long as it can be finely processed, such as electron beam ion etching, ICP etching or ECR ion etching.

At this time, it is preferable to use a source gas containing fluorine as the source gas. Such gases include, for example, CF ₄ , C ₄ F ₈ , CHF ₃ , CF ₃ C
1, CF ₂ Cl ₂ , CF ₃ Br, CCl ₄ , C ₂ F ₅ Cl ₂ ,
And such as SF _6, and the like. These gases may be used as a mixture, or may be used by further adding Ar, N ₂ , O ₂ , CO, or the like. By etching using a source gas containing fluorine, the lower film 4 can be etched several times faster than the etching rate of the resist film. As a result, even if the thickness of the resist film is small, the lower layer film pattern 7 that is faithful to the resist pattern dimensions can be obtained without the resist pattern being cut off in the middle.

Further, by using the resist pattern 6 and the lower layer film pattern 7 as an etching mask, the film 2 to be processed is etched by a dry etching method to form a film pattern 8 to be processed as shown in FIG. You. The etching method is not particularly limited as long as it can be fine-processed such as reactive ion etching, magnetron-type reactive ion etching, electron beam ion etching, ICP ion etching, or ECR ion etching. As the etching gas at this time, it is preferable to use a source gas containing at least one selected from the group consisting of oxygen, nitrogen, bromine and chlorine. The reason is that the lower layer film formed in the present invention has high etching resistance to etching conditions using a source gas containing at least one of oxygen, nitrogen, bromine and chlorine. As a result, it is possible to transfer the lower layer film pattern to the film to be processed without any processing conversion difference, thereby obtaining a film to be processed pattern.

In the present invention, a thin film may be formed between the substrate and the film to be processed. In this case, the thin film can be an interlayer insulating film made of, for example, SiO _2, and the film to be processed is used as a lower resist in a three-layer resist process. Using the film pattern to be processed formed as described above as a lower layer resist of a three-layer resist process, the lower interlayer insulating film can be processed with good dimensional controllability.

[0045]

Now, the present invention will be described in further detail with reference to specific examples.

(Embodiment 1) This embodiment will be described with reference to FIG.

(1) Example 1 First, an interlayer insulating film containing polyarylene ether as a main component was formed on a silicon wafer 1 as a film to be processed 2 with a film thickness of 50%.
It was formed at 0 nm.

Next, the lower film 3 as shown in FIG. 1A was formed on the film to be processed 2 by the following methods (S1) to (S4).

(S1) A lower layer film solution material was prepared by mixing 10 g of polysilazane (weight average molecular weight: 2,000) represented by the above formula [1-37] as a silicon compound and 90 g of anisole. The obtained solution material was applied onto the film to be processed 2 by a spin coating method.

(S2) As a silicon compound, 9.99 g of polysilazane (weight average molecular weight: 2,000) represented by the above chemical formula [1-37] and the following chemical formula [12-1]
The lower layer film solution material was prepared by mixing 0.01 g of an acid generator, which is a compound represented by the formula, and 90 g of anisole.

[0051]

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The obtained solution material was applied on the film to be processed 2 in the same manner as described above.

(S3) As a silicon compound, 9.99 g of polysilazane (weight average molecular weight: 2,000) represented by the above chemical formula [1-37] and the following chemical formula [12-2]
The lower layer film solution material was prepared by mixing 0.01 g of the acid represented by the formula and 90 g of anisole.

[0054]

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The obtained solution material was applied on the film to be processed 2 in the same manner as described above.

(S4) Polymethylsiloxane was dissolved in polyisopropanol to prepare a thin film solution. The obtained solution was applied on the lower film formed by the method (S1) by a spin coating method to form a thin film having a thickness of 20 nm.

The lower film formed in (S1) to (S3) and the thin film formed in (S4) are
Baking was performed at 60 ° C. for 60 seconds. In addition, in the atmosphere,
By baking at 300 ° C. for 60 seconds, the lower film 3
By substituting the nitrogen therein with oxygen, a denser lower film 4 was obtained as shown in FIG. 1 (b).

The amounts of Si—O bonds and Si—N bonds in the underlayer film before baking were each set to 1, and the amounts of these bonds after baking were examined using X-ray spectroscopy. Further, the density of the underlayer film before and after the baking was examined using the X-ray total reflection method, and the obtained result was compared with the Si film.
Table 1 below shows the proportions of the —O bond and the Si—N bond.

[0059]

[Table 1]

As shown in Table 1, the baking reduced the Si—N bonds in the lower layer film and increased the Si—O bonds. This is probably because nitrogen in the Si—N bond is eliminated by baking to generate a dangling bond, and the dangling bond is recombined with oxygen, and nitrogen is replaced by oxygen. Further, the density of the lower layer film is increased to 2.25 g / cm ² by performing the baking. The density of the SiO ₂ film formed by the LPCVD method capable of obtaining a high-density film quality is 2.1 g / cm ² , and the lower film of the same density can be obtained by the method of the present invention even when the coating method is used. Have been. This is presumably because baking was performed at 300 ° C. for 60 seconds to generate dangling bonds in silicon in the lower film and recombined with oxygen, thereby densifying the lower film.

Next, the lower layer film formed by the methods (S1) to (S3) was exposed to hexamethyldisilazane vapor and subjected to a hydrophobic treatment. Thereafter, at 250 ° C., 90
Ammonia generated as a by-product of the hydrophobizing treatment was removed from the surface and the inside of the lower film 4 by performing a dehydration bake for 2 seconds.

A resist solution is applied by spin coating on the lower layer film 4 thus subjected to the hydrophobic treatment, and baked at 130 ° C. for 90 seconds using a hot plate, as shown in FIG. 1C. Resist film 5
Was formed. The resist solution used here was 9.5 g of an inhibitor resin (weight average molecular weight 12,000) represented by the following chemical formula [12-3] and 0.5 g of an acid generator represented by the following chemical formula [12-4]. Was prepared by dissolving in ethyl lactate. The thickness of the obtained resist film 5 is 250 nm.
It is.

[0063]

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The resist film 5 was subjected to pattern exposure using an ArF excimer laser, and then baked at 130 ° C. for 90 seconds using a hot plate. Further, development processing is performed using a 0.21 N TMAH developing solution to obtain a 110 nm
A line-and-space resist pattern 6 was formed.

Regardless of which of the lower films was used, a resist pattern could be formed without the resist pattern 6 peeling off from the lower film 4. Further, the shape of the resist pattern was observed using a scanning electron microscope. As a result, a skirt was found on the lower film formed by the method (S1), but no skirt was formed on the lower film formed by the methods (S2) to (S4), and a favorable resist film shape was obtained. It was confirmed that it was obtained. Depending on the type of resist used, the acid contained in the resist may diffuse into the underlayer film and cause tailing, but (S
By adding an acid generator as in 2) or adding an acid as in (S3) to compensate for the lack of acid at the bottom of the resist, the bottoming can be improved. Further, by forming a thin film between the lower film 4 and the resist film 5, the diffusion of the acid into the lower film can be prevented, and the bottoming can be improved.

When the hydrophilicity of the surface of the lower layer film is high as in the films formed by the methods (S1) to (S3), the developer permeates between the resist pattern 6 and the lower layer film 4. May cause the resist pattern to peel off. In such a case, by performing the hydrophobic treatment as in the present embodiment, the adhesion can be improved and the peeling of the resist pattern 6 can be suppressed.

Next, the resist pattern 6 was transferred to the lower film 4 using a dry etching method to form a lower film pattern 7 as shown in FIG. As the etching apparatus, a magnetron type reactive ion etching apparatus was used, and a source gas CHF ₃ = 100 SCCM and O ₂ = 20 S
CCM, excitation power 1300W, degree of vacuum 75mTorr,
Etching was performed at a substrate temperature of 40 ° C. In addition,
In the case of (S4), the thin film on the lower film 4 was also etched together with the lower film. To determine the etching time,
Using end point detection by luminescence, just 50
% Over-etching.

The dimensional change caused by the etching of the lower layer film 4 is defined as follows, and is summarized in Table 1 above. The dimension conversion difference here is the difference between the dimension Y of the lower layer film pattern 7 after etching shown in FIG. 1E and the dimension X of the resist pattern 6 before etching shown in FIG. (= YX).

As shown in Table 1, the dimensional conversion difference is within the allowable range of -5 to +5 nm in any of the lower films, and the lower film 4 is etched with high dimensional controllability. I was able to.

Subsequently, the lower layer film pattern 7 was transferred to the film to be processed 2 by dry etching, thereby forming a film to be processed pattern 8 as shown in FIG. As the etching apparatus, a magnetron-type reactive ion etching apparatus was used, and a source gas C ₄ F ₈ / CO / Ar = 10/100.
/ 200SCCM, excitation power 700W, degree of vacuum 40mT
Etching was performed under conditions of orr and a substrate temperature of 20 ° C. The end point detection by light emission was used to determine the etching time, and the etching time was set to be 50% over-etching with respect to the just time.

The dimensional conversion difference caused by the etching of the film to be processed 2 is defined as follows, and is summarized in Table 1 above. Here, the difference in the dimensional conversion is the difference between the dimension Z of the processed film pattern 8 after etching shown in FIG.
It was defined by the difference (= Z−Y) from the dimension Y of the lower film pattern 7 shown in (e).

As shown in Table 1, the dimensional conversion difference was within the allowable range of -5 to +5 nm in any of the lower films, and processing was performed without deviation from the lower film pattern dimensions before etching. We were able to.

Further, the etching of the film to be processed was stopped halfway, and the etching selectivity with the film to be processed (= etching rate of the film to be processed / etching rate of the lower film) was examined. The obtained results are shown in Table 1. Summarized. Further, an SiO ₂ film formed by the LPCVD method was used as a lower layer film, and the etching selectivity to the film to be processed in that case was examined to be 8.7. From this result, it is understood that the lower layer film according to the present invention has the same etching resistance as SiO _{2 formed} by the LPCVD method. Because of such high etching resistance, in the present invention, the processing target film 2 could be etched without generating a dimensional conversion difference.

Comparative Example 1 In this comparative example, a case where a conventional spin-on-glass is formed as a lower layer film will be described.

First, in the same manner as in Example 1, a film to be processed was formed on a silicon wafer.

10 g of a polysiloxane represented by the following chemical formula (R) was dissolved in 90 g of isopropyl alcohol to prepare a solution for an underlayer film.

[0077]

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After applying this solution on the film to be processed by spin coating, the solution is heated at 200 ° C. × 60 ° C. in air.
A second baking process was performed at 300 ° C. for 60 seconds to form a lower layer film having a thickness of 80 nm. The density of the obtained lower layer film is 1.88 g / cm ³ .

A resist pattern was formed on the lower layer film in the same manner as in Example 1.

Next, the resist pattern was transferred to the lower layer film in the same manner as in Example 1 to form a lower layer pattern, and the film to be processed was processed in the same manner as in Example 1. As a result, the dimensional conversion difference when the lower layer film was transferred to the film to be processed was -20 nm, which exceeded the allowable range, and the processing could not be performed with good dimensional controllability. Further, when the etching selectivity with respect to the film to be processed was examined, it was 5.1, which was lower than that of the lower layer film used in the example. This is probably because the etching resistance of the lower layer film was low.

The reason why the etching resistance cannot be obtained by spin-on-glass is considered to be because the density of the obtained film is low. As described above, with a conventional method of forming a silicon oxide film by applying a solution containing a compound having a bond between silicon and oxygen, a high-density silicon oxide film cannot be obtained. On the other hand, in the method according to the present invention, silicon oxide-like film quality is obtained by generating dangling bonds in silicon in the lower layer film and recombining with oxygen. As a result, the lower layer film is easily densified in the process of recombination, a high-density film quality can be obtained, and the etching resistance can be improved.

Example 2 A lower film was formed on a film to be processed by the same method as in Example 1. Thereafter, ultraviolet light having a wavelength of 157 nm was applied to each lower film using an excimer lamp at an irradiation amount of 100 mJ / cm ² and a degree of vacuum of 15 mTo.
By irradiating in an rr Ar atmosphere, nitrogen in the lower layer film was replaced with oxygen.

After the electron beam irradiation, the Si—
The amount of N bonds, Si—O bonds, and the density of the lower layer film were examined in the same manner as in Example 1, and the obtained results are shown in Table 2 below.

[0084]

[Table 2]

As shown in Table 2, the substitution reaction from nitrogen to oxygen is progressing in the lower layer film as in the case of the first embodiment. In addition, the density of the lower layer film has been improved by the irradiation treatment, and it can be seen that the density has been increased.

The lower film 4 in which nitrogen is replaced by oxygen
The resist pattern 6 is formed by the same method as in the first embodiment.
Was formed. Subsequently, the lower layer film and the film to be processed were processed in the same manner as in Example 1, and the processing conversion difference and the etching selectivity were examined. The results are summarized in Table 2 above. As shown in the results in Table 2, the lower layer film in this example had the same etching resistance as in Example 1, and the film to be processed could be processed with good dimensional control.

When the lower layer film is irradiated with ultraviolet light having a wavelength of 157 nm as in this embodiment, the same effect as described above can be obtained by replacing nitrogen with oxygen.

Example 3 A lower layer film was formed on a film to be processed in the same manner as in Example 1. Thereafter, an electron beam having an acceleration voltage of 10 keV was irradiated to each lower layer film with an irradiation amount of 10000 μC / cm ² and an Ar pressure of 15 mTorr.
By irradiating in an atmosphere, nitrogen in the lower layer film was replaced with oxygen.

After the electron beam irradiation, the Si—
The amounts of N bonds and Si—O bonds and the density of the lower layer film were examined in the same manner as in Example 1, and the obtained results are shown in Table 3 below.

[0090]

[Table 3]

As shown in Table 3, the amount of Si—O bonds generated in the lower layer film was larger than in the case of Example 1, and the substitution reaction from nitrogen to oxygen was progressing. Further, it can be seen that the density is high and the density is increasing.

The lower film 4 in which nitrogen has been replaced with oxygen in this manner
The resist pattern 6 is formed by the same method as in the first embodiment.
Was formed. No skirting occurred on any of the lower films. When the substitution reaction from nitrogen to oxygen is promoted by irradiating an electron beam as in this embodiment, the acid in the resist film is not easily diffused because the density of the underlying film is increased. Therefore, it may not be necessary to add an acid or an acid generator to the lower layer film as in (S1).

Subsequently, the lower layer film and the film to be processed were processed in the same manner as in Example 1, and the processing conversion difference and the etching selectivity were examined. The results are shown in Table 3 above. As shown in the results in Table 3, the lower layer film in the present embodiment can be processed with good dimensional control with a dimensional conversion difference within an allowable range, as in the case of the first embodiment. Also, the film to be processed could be processed with a smaller processing conversion difference than in Example 1. This is considered to be because the lower layer film could be densified more than in Example 1 by the electron beam irradiation, and higher etching resistance could be imparted to the lower layer film.

When the electron beam is applied to the lower layer film to replace nitrogen with oxygen as in this embodiment, the density of the lower layer film can be further increased.

(Embodiment 4) A case in which a film pattern to be processed is formed by the pattern forming method according to the present invention, and the obtained film pattern to be processed is used as a lower resist film of a three-layer resist process will be described. In this example, an SiO ₂ film was formed immediately below the processed film pattern, and the processed film pattern was transferred to the SiO ₂ film to form an SiO ₂ pattern.

[0096] First, on a silicon wafer, to form a SiO ₂ film having a film thickness of 500nm as an interlayer insulating film. The interlayer insulating film formed here corresponds to the layer denoted by reference numeral 1 in FIG.

A film to be processed was formed on the interlayer insulating film by the following method. First, an average weight molecular weight of 12,0
Novolak resin No. 00 was dissolved in 90 g of ethyl lactate to prepare a solution for a film to be processed, and this solution was applied onto the interlayer insulating film by spin coating. afterwards,
Using a hot plate at 180 ° C. for 60 seconds, followed by 3
By heating at 00 ° C. for 120 seconds, a film to be processed 2 having a thickness of 500 nm was formed.

Next, the lower film 3 was formed on the film to be processed by using the same method as in the first embodiment.

The obtained lower film was irradiated with an electron beam in the same manner as in Example 1 to replace nitrogen in the lower film with oxygen. When the ratio of nitrogen to oxygen was examined using X-ray spectroscopy, it was confirmed that nitrogen was replaced by oxygen as in Example 1.

Subsequently, a resist film was formed on the lower layer film in the same manner as in Example 1 to form a resist pattern. Further, processing of the lower layer film and processing of the film to be processed were sequentially performed to form a film pattern to be processed. When the processing conversion difference was examined, it was possible to perform processing with good dimensional control as in Example 1.

[0102] Furthermore, to form the SiO ₂ pattern by transferring the processed film pattern in the SiO ₂ film. According to the present invention, it is possible to suppress the processing conversion difference when transferring the lower layer film pattern to the film pattern to be processed, so that an SiO ₂ pattern can be obtained with good dimensional control. In this way, the film pattern to be processed can be transferred to a thin film located further below.

[0102]

As described in detail above, according to the present invention,
Provided is a pattern forming method capable of reducing the thickness of a resist film using a lower layer film that can be formed by a coating method, securing a necessary mask thickness, suppressing a processing conversion difference, and processing a target film with high dimensional accuracy. You.

The present invention is extremely effectively used for fine processing for manufacturing a semiconductor device, and its industrial value is enormous.

[Brief description of the drawings]

FIG. 1 is a process sectional view illustrating an example of a pattern forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Film immediately under a board | substrate or a film to be processed 2 ... Film to be processed 3 ... Lower film 4 ... Lower film in which nitrogen was substituted by oxygen 5 ... Resist film 6 ... Resist pattern 7 ... Lower film pattern 8 ... Film film pattern

Continued on front page F-term (reference) 2H025 AA00 AB16 AC01 AC04 AC05 AC06 AC07 AC08 AD01 AD03 DA40 FA01 FA03 FA12 FA17 FA41 2H096 AA00 AA25 BA01 BA09 DA10 EA02 EA04 EA05 EA06 EA07 EA08 FA01 GA08 HA23 JA02 JA04 A04 DA04 DA04 DA05 DA06 DA10 DA18 DA23 DA25 DA26 EA03 EA04 FA01 FA04 FA05 5F046 NA01 NA18 NA19

Claims (20)

[Claims] 1. A step of applying a solution containing a compound having a bond between silicon and nitrogen in a main chain on a film to be processed to form an underlayer film, and replacing the nitrogen in the underlayer film with oxygen. A step of forming a resist film on the underlayer film; a step of subjecting the resist film to pattern exposure and development to form a resist pattern; and transferring the resist pattern to the underlayer film to form an underlayer. A pattern forming method, comprising: forming a film pattern; and transferring the lower film pattern to the film to be processed to form a film pattern to be processed. 2. The pattern forming method according to claim 1, wherein the content of nitrogen in the compound having a bond between silicon and nitrogen in a main chain is 5 to 80 wt%. 3. The method according to claim 1, wherein said nitrogen in said lower layer film is 20%
3. The pattern forming method according to claim 1, wherein oxygen is replaced by oxygen. 4. The method according to claim 1, wherein said nitrogen in said lower film is 80%
4. The pattern forming method according to claim 3, wherein the above is replaced with oxygen. 5. The method according to claim 1, wherein the step of substituting the nitrogen in the lower film with oxygen is performed by heating or irradiating the lower film with an energy beam. 2. The pattern forming method according to claim 1. 6. The heating of the lower film is performed at 200 ° C. to 500 ° C.
The pattern forming method according to claim 5, wherein the method is performed at a temperature of ° C. 7. The energy beam has a thickness of 1 nm to 1 m.
The pattern forming method according to claim 5, wherein the light is an electron beam or a light including any wavelength in the range of m. 8. The energy beam has a thickness of 1 nm to 1 m.
a light including any wavelength in the range of m, a pattern forming method according to claim 7 the irradiation amount, which is a ^{1mJ / cm 2 ~1000J / cm 2} . 9. The pattern forming method according to claim 7, wherein the energy beam is an electron beam, and the irradiation amount is 1 μC / cm ^{2 to} 1000 C / cm ² . 10. The method according to claim 5, wherein the step of substituting the nitrogen in the lower film with oxygen is performed while exposing the lower film to an atmosphere containing moisture and oxygen. Item 2. The pattern forming method according to Item 1. 11. The pattern forming method according to claim 10, wherein the humidity in the atmosphere is 10% or more, and the oxygen concentration in the atmosphere is 10% or more. 12. The pattern forming method according to claim 1, wherein the film to be processed contains a compound containing carbon. 13. The method according to claim 1, further comprising a step of obtaining a thin film pattern by transferring a pattern of the film to be processed to the thin film, further comprising a thin film immediately below the film to be processed.
3. The pattern forming method according to 2. 14. The pattern forming method according to claim 13, wherein the thin film provided immediately below the film to be processed is an interlayer insulating film. 15. The pattern forming method according to claim 1, wherein the film pattern to be processed is formed by a dry etching method using a source gas containing at least one of oxygen, nitrogen, chlorine and bromine. Method. 16. The resist film is formed from a chemically amplified resist, and immediately before forming the resist film, the lower layer film is heated to remove a substance that deactivates an acid generated in the chemically amplified resist. The pattern forming method according to claim 1, wherein the pattern is removed from the lower layer film. 17. The heating of the lower film is performed at 150 ° C. to 50 ° C.
The method according to claim 16, wherein the method is performed at a temperature of 0 ° C. 18. The pattern forming method according to claim 1, wherein prior to the step of forming a resist film on the lower film, the lower film is subjected to a hydrophobic treatment. 19. The method according to claim 19, wherein after forming the resist film and before forming the resist film, the lower film is heated to remove by-products generated by the hydrophobic treatment from the lower film. Item 19. The pattern forming method according to Item 18. 20. The resist film is formed of a chemically amplified resist, and prior to a step of forming a resist film on the lower layer film, a resist film for preventing deactivation of an acid generated in the chemically amplified resist. 2. The pattern forming method according to claim 1, further comprising a step of forming a thin film on the lower film.