JP2002198295A - Pattern formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pattern formation method for forming a pattern where unevenness is reduced on a sidewall by a multilayer resist process. SOLUTION: This pattern formation method includes a process for forming a lower-layer film (103) that contains carbon on a silicon wafer (101), a process for forming a middle film (104) that has the connection between silicon elements in a main chain and at the same time contains a silicon compound including a unit having elimination properties on the lower-layer film by the coating method, a process for eliminating the unit having elimination properties of the silicon compound, a process for forming a resist film (106) on the uniformized, middle film (105), a process for forming a resist pattern (107) by carrying out pattern exposure and processing to the resist film, a process for using the resist pattern as a mask for processing the middle film to obtain a middle film pattern (108), and a process for using the middle film pattern as the mask for processing the lower-layer film to obtain a lower-layer film pattern (109).

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 materials on a wafer to form thin films, and patterning each thin film into a desired pattern. In patterning a film to be processed, first, a photosensitive substance generally called a resist is deposited on the film to be processed on a wafer to form a resist film, and a predetermined region of the resist film is selectively 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 is a problem that a resist film thickness required for etching the film to be processed cannot be secured.

In order to solve such a problem, a lower resist film, an intermediate film, and a resist film are sequentially formed on a film to be processed, and a resist pattern is formed by performing pattern exposure on the resist film. A multilayer resist process for obtaining a lower resist pattern by transferring a pattern by sequentially etching an intermediate film and a lower resist film is used. The spin-on-glass etching is performed using a fluorine-based gas. Kw
ong, et al. SPIE, Proc. SPIE
As reported in 3678, 1209 (1999), under these etching conditions, unevenness occurs on the side wall of the resist pattern, and the unevenness is transferred to the spin-on glass. In addition, when etching the lower resist film, the spin-on-glass serving as an etching mask is shaved unevenly, and the processed shape of the lower resist film is further deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pattern forming method capable of forming a pattern having reduced side wall irregularities by using a multilayer resist process. Aim.

[0006]

In order to solve the above-mentioned problems, the present invention mainly comprises a step of forming an underlayer film containing carbon on a silicon wafer, and a step of bonding silicon and silicon on the underlayer film. A step of forming, by a coating method, an intermediate film containing a silicon compound having a chain and containing a desorbable unit, a step of desorbing the desorbable unit of the silicon compound, and the uniformized intermediate film Forming a resist film thereon, performing a pattern exposure and development process on the resist film to form a resist pattern, and processing the intermediate film using the resist pattern as a mask, A pattern forming method comprising: a step of obtaining a pattern; and a step of processing the lower layer film using the intermediate film pattern as a mask to obtain a lower layer pattern. That.

[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 resist film 103 is formed on a film to be processed 102 formed on a wafer substrate 101. The processed film 102 is, for example,
Conductive materials such as aluminum, aluminum silicide, copper, tungsten, tungsten silicide, titanium, and titanium nitride; semiconductor materials such as germanium and silicon; silicon oxide; silicon nitride; and insulating materials such as silicon oxynitride and organic resin be able to.

The lower resist film 103 can be formed of any organic compound. The film to be processed 102
In order to provide etching resistance when processing the organic compound, the lower organic resist 10
When it is 0 parts by weight, it is preferable that 50 parts by weight or more of carbon is contained. Specifically, a solution obtained by dissolving a novolak resin, a polyvinylphenol resin, a polymethacrylate resin, a polyarylene resin, a polyarylene ether resin, or a polyimide in a solvent is applied by a spin coating method or the like, and a hot plate, an oven, or the like. The film can be formed by baking.

In forming the lower resist film 103, spin coating is preferably employed because the process is simple, but carbon or the like may be formed by sputtering or CVD. It is preferable that the thickness of the lower resist film 103 is approximately in the range of 20 to 10000 nm. The thickness of the lower resist film is 20 nm
If the thickness is less than the above range, it becomes difficult to act as an etching mask when etching the underlying film to be processed 102. On the other hand, if it exceeds 10,000 nm, a dimensional conversion difference is remarkably generated when the intermediate film pattern is transferred to the lower resist film.

In the pattern forming method of the present invention, the lower resist film 103 thus formed functions as a lower film formed immediately below the intermediate layer. When the film to be processed 102 is formed from an organic resin containing carbon, an intermediate film may be directly formed using the film to be processed as a lower layer film.

Next, as shown in FIG. 1B, an intermediate film 104 is formed on the lower resist film 103. In the present invention, an intermediate film 104 is formed by applying a solution obtained by dissolving a specific silicon compound in a solvent, and then evaporating the solvent. As the silicon compound for forming the intermediate film, a silicon compound having a bond between silicon and silicon in a main chain and having a detachable unit in a side chain is used. Specifically, examples of the silicon compound include a compound represented by the general formula (SiR ¹¹ R ¹² ). Where R ¹¹ and R ¹²
Represents a hydrogen atom, a hydroxyl group, or a substituted or unsubstituted aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 20 carbon atoms. These organic groups R ¹¹ and R ¹² must be eliminable units which can be eliminated by the following operations, which will be described later.

The silicon compound used in the present invention may be a homopolymer or a copolymer. In addition, two or more silicon compounds are composed of an oxygen atom, a nitrogen atom,
It may have a structure bonded to each other via an aliphatic group or an aromatic group. Further, the silicon compound may be a cyclic compound. More specifically, the following compounds can be used as the silicon compound.

[0015]

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[0016]

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[0018]

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[0027]

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[0028]

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[0029]

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[0030]

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

The molecular weight of these silicon compounds is not particularly limited, but is preferably in the range of 100 to 100,000. The reason is that if the molecular weight of the silicon compound is less than 100, the stability of the coating film cannot be obtained, while if it exceeds 100,000, it is difficult to dissolve in a solvent and it is difficult to prepare a solution material. Because it becomes. The silicon compound is not limited to one kind, and a mixture of several kinds of compounds can be used.

By dissolving the above-mentioned silicon compound in a predetermined organic solvent, a coating material for an intermediate film is prepared. The organic solvent is not particularly limited, and any one can be used. For example, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; cellosolve solvents such as methyl cellosolve, methyl cellosolve acetate and ethyl cellosolve acetate; ester solvents such as ethyl lactate, ethyl acetate, butyl acetate and isoamyl acetate; methanol,
Alcoholic solvents such as ethanol and isopropanol,
Other examples include anisole, toluene, xylene, and naphtha.

If necessary, a thermal polymerization inhibitor for improving storage stability, an adhesion improver for improving adhesion to the lower resist film, and a surfactant for improving coating properties are added. May be.

The coating material prepared as described above is applied on the lower resist film 103 by, for example, a spin coating method or the like to form a coating film. Next, the intermediate film 104 is formed by heating to evaporate the solvent. The thickness of the intermediate film 104 formed here is 10 to 1
It is preferably in the range of 000 nm. When the thickness of the intermediate film is less than 10 nm, it is difficult to act as an etching mask when etching the lower resist film 103. On the other hand, when the thickness exceeds 1000 nm, when the resist pattern is transferred to the intermediate film 104, This is because a dimensional conversion difference occurs remarkably.

Then, using a hot plate, an electric furnace, a heat radiation furnace, a halogen lamp, a flash lamp, etc.
By baking, the elimination unit in the silicon compound is eliminated. Thus, a uniformized intermediate film 105 as shown in FIG. 1D is obtained.

When a relatively light volatile group such as a hydrogen atom and a methyl group is introduced as R ¹¹ and R ¹² in the silicon compound for forming the intermediate film 104, the temperature is about 100 to 500 ° C. Baking, or 10 J / cm ² or less for light, 10 for electron beam
Irradiation with an energy beam of about C / cm ² or less allows easy desorption from the silicon compound. On the other hand, when a relatively heavy group such as an ethyl group or a propyl group having 3 or more carbon atoms is introduced as a leaving unit as R ¹¹ and R ¹² , baking at a higher temperature and a higher irradiation dose Can be desorbed by irradiating with an energy beam.

Further, the intermediate film 104 may be subjected to a solvent treatment to desorb the eliminable unit from the silicon compound. The solvent is not particularly limited, and any solvent can be used. For example, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; cellosolve solvents such as methyl cellosolve, methyl cellosolve acetate and ethyl cellosolve acetate; ester solvents such as ethyl lactate, ethyl acetate, butyl acetate and isoamyl acetate; Examples thereof include alcohol solvents such as methanol, ethanol, and isopropanol, and anisole, toluene, xylene, and naphtha. Further, an alkaline aqueous solution may be used.
By applying such a solvent to the intermediate film 104,
The desorbable unit is dissolved and removed from the silicon compound to be desorbed. For example, when a substituent containing a hydroxyl group having a high polarity as R ¹¹ and R ¹² , for example, a hydroxyl group, a methanol group, an ethanol group, and a phenol group are introduced, it is preferable to remove by such a solvent treatment. .

When the desorbable unit is desorbed from the silicon compound by baking, the temperature is 100
The range is preferably from 1200 to 1200 ° C, more preferably from 150 to 500 ° C. If the temperature is lower than 150 ° C., the decomposition reaction of the desorbable unit does not sufficiently proceed, and if the temperature exceeds 500 ° C., the oxidation of the intermediate film 104 progresses, resulting in a silicon oxide-like film quality.

As an energy beam for accelerating the desorption of the desorbable unit, visible light, ultraviolet light, deep ultraviolet light, X-ray and electron beam can be used.
When irradiating visible light, ultraviolet light, deep ultraviolet light, or X-rays, the irradiation amount is not particularly limited, but is 1 mJ.
/ Cm ^{2 to} 1000 J / cm ² is preferred. 1mJ
If it is less than / cm ² , it will be difficult to sufficiently promote the detachment of the detachable unit. On the other hand, if it exceeds 1000 J / cm ² , the irradiation time may be increased and the throughput may be reduced.

When irradiating an electron beam, the irradiation amount is not particularly limited, but is 0.001 μC / cm ² to 1 μC / cm ^2.
A range of 000 C / cm ² is preferred. When the irradiation amount of the electron beam is less than 0.001 μC / cm ² , it becomes difficult to sufficiently advance the detachment of the detachable unit. On the other hand, if it exceeds 1000 C / cm ² , the irradiation time may be increased and the throughput may be reduced. The acceleration voltage is preferably in the range of 0.001 to 1000 keV. If the accelerating voltage is less than 0.01 keV, there is a possibility that only the desorbable units near the surface of the intermediate film 104 are desorbed. On the other hand, when it exceeds 1000 keV, most of the electrons penetrate through the intermediate film, and it becomes difficult to sufficiently remove the desorbable unit of the intermediate film.

The atmosphere during the baking of the intermediate film preferably has an oxygen concentration of 1% or less, more preferably 1000 ppm or less. If the oxygen concentration exceeds 1%, the oxidation proceeds, resulting in a silicon oxide-like film quality. Further, baking may be performed in a reduced pressure atmosphere in order to promote the detachment of the detachable unit.

In the present invention, the intermediate film 104 is subjected to the above-described treatment, so that the desorbable unit is eliminated from the silicon compound, so that the intermediate film is made uniform. The composition of the uniformized intermediate film 105 is preferably such that Si is 40 atomic% or more, and more preferably 80 atomic% or more. When the Si content is less than 4 atomic%,
There is a possibility that the etching rate when processing the intermediate film is reduced. The content of H is preferably at most 60 atomic%, more preferably at most 20 atomic%. If the H content exceeds 60 atomic%, the etching when processing the intermediate film proceeds unevenly, and the roughness of the side wall increases. Further, the content of O is preferably 20 atomic% or less,
More preferably, it is 5 atomic% or less. The content of O in the uniformized intermediate film 105 is 20 atom
If it exceeds mic%, the film quality may be like silicon oxide.

A resist solution is applied on the uniformized intermediate film 105 by spin coating or the like, and the solvent is evaporated by heating to form a resist film 106 as shown in FIG. 1D. . If the thickness of the resist film 106 is reduced, the exposure latitude, the focus latitude, or the resolution can be improved. Therefore, the film thickness of the resist film 106 is preferably as small as possible so long as the intermediate film 105 can be etched with good dimensional control, and preferably 10 to 10,000 nm. If the thickness of the resist film 106 is less than 10 nm, it is difficult to etch the intermediate film in a good shape.
If it exceeds 10,000 nm, the resolution will be reduced.

The resist composition for forming the resist film 106 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, and a positive type or a negative type is selected and used. be able to. Examples of the positive resist composition include a resist composition (IX-770, manufactured by JSR) containing naphthoquinonediazide and a novolak resin, and a polyvinylphenol resin protected with t-BOC and a photoacid generator. A resist composition containing a polyvinyl phenol resin copolymerized with tertiary butyl methacrylate and an acid generator (UVIIHS, manufactured by Shipley), etc. No. Examples of the negative resist include a chemically amplified resist containing polyvinyl phenol, a melamine resin, and a photoacid generator (SNR200, manufactured by Shipley), and a resist containing polyvinyl phenol and a bisazide compound (RD). -2000N, manufactured by Hitachi Chemical Co., Ltd.), but is not limited thereto.

After applying such a resist solution on the intermediate film 105 by, for example, a spin coating method or a dip method, the resist film 106 is formed by heating the mixture on a hot plate or an oven to evaporate the solvent. .

Next, pattern exposure is performed on the resist film 106. 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) and i-line (wavelength = 365) of a mercury lamp are used.
nm), XeF (wavelength = 351 nm), XeC
1 (wavelength = 308 nm), KrF (wavelength = 248 n)
m), KrCl (wavelength = 222 nm), ArF (wavelength =
Excimer laser such as 193 nm) and F ₂ (wavelength = 151 nm). If necessary, post-exposure baking may be performed using a hot plate, an oven or the like.

In the pattern forming method of the present invention, since the intermediate film can be processed with a high selectivity with respect to the resist film, the resist film 106 can be formed with a thin film thickness of about 200 nm or less. It is. Therefore, low-acceleration electron beam and the thinning of the resist film is required, the time of pattern exposure to F ₂ laser as the exposure light source, the present invention is particularly effective.

Next, a resist pattern 107 as shown in FIG. 1E is formed by performing development processing with an alkali developing solution such as TMAH (tetramethylammonium hydroxide) and choline.

If necessary, an upper anti-reflection film for reducing multiple reflections in the resist film generated when performing light exposure, or an upper anti-reflection film for preventing charge-up generated when performing electron beam exposure. An antistatic film may be formed on the resist film 106.

Using the obtained resist pattern 107 as an etching mask, the intermediate film 105 is dry-etched to transfer the pattern shape of the resist pattern 107 to the intermediate film 105, as shown in FIG. 1 (f). An intermediate film pattern 108 is formed. The etching method is not particularly limited as long as it can be finely processed by, for example, reactive ion etching, magnetron type reactive ion etching, electron beam ion etching, ICP etching or ECR ion etching.

At this time, as the source gas, a chlorine-based gas, ie, a gas containing chlorine atoms in molecules, or a bromine-based gas, ie, a gas containing bromine atoms in molecules, can be used. Examples of the chlorine-based gas include CF ₃ C
1, CF ₂ Cl ₂ , CF ₃ Br, CCl ₄ , C ₂ F ₅ Cl ₂ ,
Cl ₂ , SiCl ₄ , and BCl ₃ .
Further, examples of the bromine-based gas include a gas such as HBr. These chlorine-based gas and bromine-based gas may be used as a mixture. When etching is performed using such an etching gas, deposits on the resist pattern 107 are reduced unlike the case of a fluorocarbon-based gas that has been conventionally used. Therefore, it is possible to prevent the side wall of the resist pattern from being roughened during the etching of the intermediate film 105. As a result, the intermediate film pattern 108 can be obtained with a good processed shape.

Further, using the resist pattern 107 and the intermediate film pattern 108 as an etching mask,
By etching the lower resist film 103, a lower resist film pattern 109 as shown in FIG. 1 (g) is formed. 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, a gas containing an oxygen atom or a nitrogen atom is preferably used. The intermediate film 105 uniformized by the method of the present invention is inert to an etchant obtained by discharging using such a gas containing atoms, and thus has high etching resistance. Therefore, the lower resist film 103 can be processed with good anisotropy.

As an etching gas containing an oxygen atom,
O ₂ , CO, and CO ₂ are mentioned, and N ₂ , NH _{3 and the} like can be mentioned as an etching gas containing a nitrogen atom.
These etching gases may be used as a mixture. Further, the etching gas may contain a sulfur atom such as SO ₂ . The reason is that the lower resist film can be processed with good anisotropy. In addition, ArF, He
And the like.

As described above, the lower resist film 103
Can prevent the sidewall roughness from occurring in the intermediate film pattern 108 during the etching of the lower resist film. As a result, it becomes possible to obtain the lower resist film pattern 109 without side wall roughness. It is considered that this is because the desorbable unit in the silicon compound constituting the intermediate layer was desorbed, the composition in the film was made uniform, and the etching proceeded uniformly.

As described above, the lower resist film 103
By processing this, a lower resist film pattern 109 having no side wall roughness can be obtained.

[0057]

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.

First, as shown in FIG. 1A, a film to be processed 102 having a film thickness of 500 is formed on a silicon wafer 101.
A TEOS oxide film of nm was formed by the LPCVD method.
In forming the lower resist film, novolak resin 1
0 g was dissolved in 90 g of ethyl lactate to prepare a solution. This solution is spin-coated on the film to be processed 102 and then heated at 300 ° C. for 60 seconds to form a film having a thickness of 50 μm.
A lower resist film 103 of 0 nm was formed.

Next, using the method shown in the following (S1) to (S15), the intermediate film 104 as shown in FIG.
Are formed, and the detachable units are detached, respectively, as shown in FIG.
A uniform intermediate film 105 was formed as shown in FIG.

(S1) As a silicon compound, 10 g of cyclopentasilane was prepared and dissolved in 90 g of cumene to prepare a solution material for the intermediate film. The obtained coating material was applied on the lower resist film 103 by a spin coating method to form an intermediate film 104. In the cyclopentasilane used here, a hydrogen atom acts as a desorbable unit.

Further, at 150 ° C. in a nitrogen atmosphere (atmospheric pressure) having an oxygen concentration of 50 ppm or less using a hot plate.
The baking was performed for minutes, so that the detachable unit was detached, and a uniformed intermediate film 105 was formed.

(S2) 5 minutes at 300 ° C. for 1 minute at 150 ° C.
A uniform intermediate film 105 was obtained by the same method as in the above (S1), except that the baking for one minute was sequentially performed to remove the detachable unit.

(S3) 5 minutes at 400 ° C. for 1 minute at 150 ° C.
A uniform intermediate film 105 was obtained by the same method as in the above (S1), except that the baking for one minute was sequentially performed to remove the detachable unit.

(S4) 5 minutes at 500 ° C. for 1 minute at 150 ° C.
A uniform intermediate film 105 was obtained by the same method as in the above (S1), except that the baking for one minute was sequentially performed to remove the detachable unit.

(S5) 5 minutes at 600 ° C. for 1 minute at 150 ° C.
A uniform intermediate film 105 was obtained by the same method as in the above (S1), except that the baking for one minute was sequentially performed to remove the detachable unit.

(S6) The uniformized intermediate film 105 was obtained in the same manner as in the above (S3) except that the elimination unit was eliminated by baking in the air.

(S7) An intermediate uniformized by the same method as in the above (S3), except that the elimination unit was eliminated by baking in a nitrogen atmosphere (in the air) having an oxygen concentration of 2%. The film 105 was obtained.

(S8) An intermediate film made uniform by the same method as in the above (S3), except that the elimination unit was eliminated by baking in a nitrogen atmosphere (atmosphere) having an oxygen concentration of 1000 ppm. 105 was obtained.

(S9) An intermediate film made uniform by the same method as in the above (S3), except that the elimination unit was eliminated by baking in a nitrogen atmosphere (in the air) having an oxygen concentration of 300 ppm. 105 was obtained.

(S10) A uniform intermediate film 105 was obtained by the same method as in the above (S2), except that the baking was performed under a reduced pressure atmosphere of 10 Torr to remove the detachable unit.

(S11) A uniformized intermediate film 105 was obtained in the same manner as in the above (S2), except that baking was performed under a reduced pressure atmosphere of 1 Torr to remove the desorbable unit.

(S12) The intermediate film 105 is made uniform by the same method as in the above (S2), except that the elimination unit is eliminated by baking in a reduced pressure atmosphere of 1 × 10 ⁻¹ Torr. I got

(S13) Further, an electron beam irradiation amount of 10 C is applied in a nitrogen atmosphere (atmospheric pressure) having an oxygen concentration of 50 ppm or less.
A uniform intermediate film 105 was obtained by the same method as in the above (S1) except that the intermediate film was irradiated at / cm ² .

(S14) The above-described (S14) was repeated except that the intermediate film was irradiated with a flash lamp at a dose of 20 J / cm ² in a nitrogen atmosphere (atmospheric pressure) having an oxygen concentration of 50 ppm or less.
The uniformized intermediate film 105 was obtained by the same method as in 1).

(S15) As a silicon compound, 10 g of the compound represented by the above formula (1-50) is prepared,
This was dissolved in cyclohexanone to prepare a solution material for the intermediate film. The obtained coating material was applied onto the lower resist film 103 by a spin coating method to form an intermediate film 104 as shown in FIG. In addition, in the compound used here, a butyl group which is an organic component functions as a detachable unit.

Further, at 150 ° C. in a nitrogen atmosphere (atmospheric pressure) having an oxygen concentration of 50 ppm or less using a hot plate.
Baking for minutes. Further, the removable unit was eliminated by dissolving and removing the organic components in the mask over the entire surface with toluene to form a uniform intermediate layer 105 as shown in FIG. 1C.

The thickness of the intermediate film 105 formed in (S1) to (S15) was 100 nm.

Further, the following processes (R1) to (R3) were applied to the intermediate film 104 as a reference sample.

(R1) The same operation as in the above (S1) was performed, except that the solvent was removed by air drying after applying the solution material without performing baking for detaching the detachable unit.

(R2) The same operation as in the above (S1) was performed except that baking was performed at 100 ° C. for 5 minutes.

(R3) The same operation as in (S15) was performed, except that toluene was applied to the liquid surface and the organic components in the intermediate film were not removed.

Of the above (S1) to (S15), (S1)
In 2) to (S5), two-stage baking is performed. In order to prevent the solvent from abruptly vaporizing and generating cracks and craters in the coating film, it is effective to perform the two-stage baking as described above. In the present invention, if necessary, the intermediate film may be subjected to multi-stage baking. Also, as in (S13) and (S14),
Irradiation with an energy beam to gasify the desorbable unit (decomposable unit) can also be desorbed from the silicon compound.

With respect to the intermediate film formed by the method of (S1) to (S15) and the reference sample formed by the method of (R1) to (R3), Si, H,
The content (atomic%) of each element of O was examined. The results are summarized in Table 1 below.

[0085]

[Table 1]

(S1) to (S5), (R1) and (R
The comparison in 2) shows that the dehydrogenation reaction proceeds due to the decomposition and gasification of hydrogen at 150 ° C. or higher, and the oxidation of the intermediate film proceeds at 600 ° C. or higher. In the case where the baking was not performed (R1) and the case where the baking was performed at 100 ° C. (R2), the hydrogen content in the intermediate film exceeded 65 atomic%, and the baking was performed at 150 ° C. (S1). In, the hydrogen content is slightly reduced. Further, although the hydrogen content is reduced by performing the two-stage baking, the oxygen content is increased at the baking temperature of 600 ° C. (S5). Comparing (S15) and (R3), it can be seen that the content of carbon and hydrogen is reduced by the solvent treatment, and siliconization is performed.

Further, (S3) and (S6) to (S9)
The comparison shows that the lower the oxygen concentration in the baked atmosphere, the less the effect of oxidation. Furthermore, comparing (S2) and (S10) to (S12), it is understood that the dehydrogenation reaction proceeds more easily in the reduced pressure atmosphere.

Next, on each of the uniformed intermediate films 105,
A resist solution was applied by spin coating, and baked on a hot plate at 140 ° C. for 90 seconds to form a resist film 106 as shown in FIG. 1D. The resist solution used here is a positive chemically amplified resist KRF M20G (manufactured by JSR).
The thickness of the obtained resist film 106 is 50 nm.

The resist film 106 is subjected to pattern exposure using an exposure apparatus (NA = 0.6) using an F ₂ excimer laser as a light source, and is baked at 140 ° C. for 90 seconds using a hot plate. gave. The resist film 106 after baking is subjected to paddle development using 0.21 N tetramethylammonium hydroxide for 30 seconds, thereby obtaining a resist film 106 as shown in FIG.
0 nm line and space resist pattern 10
7 was formed.

Observation of the resist pattern 107 from above, the least square mean value of the unevenness on the side wall of the resist pattern was 2.5 nm.

Next, the intermediate film 105 was etched using a magnetron type etching apparatus to transfer the shape of the resist pattern 107 to the intermediate film, thereby forming an intermediate film pattern 108 as shown in FIG. The etching conditions here were: source gas Cl ₂ = 200 SCCM, degree of vacuum: 75 mTorr, excitation power density: 2.0 W / cm ² , and substrate temperature: 80 ° C.

After completion of the etching, the resist pattern 10
7 was observed from above and the least-square mean value of the unevenness of the resist pattern side wall was examined. When any intermediate film was used, it was 2.8 nm, which was within the allowable value of 5 nm or less. Therefore, the etching of the intermediate film 105 could be performed while suppressing the side wall irregularities of the resist pattern.

The dimensional conversion difference caused by the etching of the intermediate film 105 is defined as follows, and is summarized in Table 1 above. The dimensional conversion difference here is the difference (= Y−) between the dimension Y of the intermediate film pattern 108 shown in FIG. 1F and the dimension X of the resist pattern 107 shown in FIG.
X).

As shown in Table 1, in each case, the dimensional conversion difference was within the allowable range of -5 to +5 nm or less, and the intermediate film 105 could be processed with good dimensional control.

The etching of the intermediate film is stopped halfway, and the selectivity of the intermediate film to the resist (= the etching rate of the intermediate film /
The etching rate of the resist pattern) was examined, and the obtained results are summarized in Table 1. Each intermediate film is etched at a high selectivity of 5.2 or more. As a result, it is considered that the intermediate film 105 was able to be etched without preventing the resist pattern from falling off, and without deviating from the dimension of the resist pattern 107. (S1) ~
Comparing the resist selectivity for (S15), the more the dehydrogenation reaction proceeds and the less the influence of oxidation, the more
High selectivity to resist. As a result, the processing conversion difference can be reduced, which is preferable. In particular, when the composition ratio of hydrogen is 2
0 atomic% or less, oxygen composition ratio is 8 atomic
% (S2) to (S6) and (S7) to (S15), the intermediate film 105 could be processed with an extremely small processing conversion difference of 3 nm or less.

Further, as the silicon compound, the above-mentioned chemical formulas [1-1], [1-22], [1-46], [1-4]
7] and the compound represented by [1-115], and an intermediate film was formed in the same manner as in the above (S1) to (S15). Further, a predetermined treatment was performed to desorb the desorbable unit in the silicon compound, thereby forming a uniform sample of the intermediate film. Also, samples were prepared using these silicon compounds under the same conditions as (R1) to (R3).

For each of the obtained samples, element analysis and etching of the intermediate film were performed in the same manner as described above. As a result, the same tendency as in the case of cyclopentasilane was observed with respect to the relationship between the desorption conditions and the residual ratio of desorbable units in the silicon compound and the selectivity to resist.

From the above results, the baking temperature for desorbing the desorbable unit from the silicon compound to make the intermediate film uniform is preferably in the range of about 150 to 500 ° C. 1% or less, and a reduced pressure atmosphere is preferable.

Subsequently, the lower resist film 103 is etched using a magnetron type etching apparatus, and the shape of the intermediate film pattern 108 is transferred to the lower resist film.
A lower resist film pattern 109 as shown in (g) was formed. The etching conditions here are the source gas O ₂ /
N ₂ = 10/100 SCCM, excitation power 700 W, degree of vacuum 40 mTorr, and substrate temperature 20 ° C. For the determination of the etching time, the end point detection by light emission was used, and the etching time was set so as to be 50% over-etching with respect to the just time.

When the cross section of the obtained lower resist film pattern 109 was observed using a scanning electron microscope, it was found that the lines and spaces were processed with good anisotropy as shown in FIG. confirmed.

FIG. 2 shows the result of observing the intermediate film pattern 108 of (S1) to (S15) from above. FIG.
As shown in (1), in any case, the lower resist film 103 could be etched without excessively increasing the unevenness on the side surface of the pattern.

When the least squares mean value of the irregularities on the side surface of the intermediate film pattern 108 was calculated, the values (S1) to (S1)
All of 5) were within the allowable range at 5 nm or less. On the other hand, for (R1) to (R3), irregularities exceeding the allowable amount of 5 nm occurred. Thus, (R1) to (R
The reason why the unevenness is large in 3) is that the removable unit in the silicon compound in the intermediate film is not removed. That is, in the intermediate film in this case, there are a silicon portion and a desorbable unit such as a hydrogen portion. Since the silicon portion and the hydrogen portion have different etch rates, it is conceivable that the etching progressed unevenly when the intermediate film 105 was processed.

In the method of the present invention, the dehydrogenating unit was desorbed from the silicon compound constituting the intermediate film to promote the dehydrogenation reaction, so that the composition of the intermediate film could be made uniform. This makes it possible to reduce the surface roughness of the intermediate film and to process the lower resist film with a favorable processing shape.

Further, the dimensional conversion difference caused by the etching of the lower resist film 103 is defined as follows, and is summarized in Table 1 above. The dimensional conversion difference is shown in FIG.
(G) of the lower resist film pattern 109 shown in FIG. 1G and the intermediate film pattern 108 shown in FIG.
(= Z−Y).

As shown in Table 1, in each case,
The dimensional conversion difference is in the range of -5 to +5 nm,
The lower resist film 103 could be processed with good dimensional control.

The etching of the lower resist film was stopped halfway, and the selectivity to the resist of the lower resist film 103 (= etching rate of the lower resist film / etching rate of the intermediate film) was examined. The obtained results are summarized in Table 1. Was. In any of the intermediate films, a high selectivity of 4.5 or more is secured. As a result, it is considered that the shoulder of the intermediate film pattern could be prevented from being dropped, and the lower resist film could be etched without deviating from the dimensions of the intermediate film pattern. (S
Comparing the resist selectivity for 1) to (S15) and (R1) and (R2), the selectivity is higher as the dehydrogenation reaction proceeds and the influence of oxidation is smaller. As a result, it is found that the processing conversion difference can be reduced, which is preferable.

Comparative Example 1 In this comparative example, a case where an intermediate film is formed using a conventional spin-on glass will be described.

First, in the same manner as in Example 1, a film to be processed and a lower resist film were formed on a silicon wafer. Next, an intermediate film was formed on the lower resist by the following method (R4).

(R4) 10 g of a spin-on glass (n / m = 1/1) of a compound represented by the following chemical formula (weight average molecular weight 11,000) was dissolved in 90 g of isopropyl alcohol to prepare a coating material. After applying this coating material on the lower resist film by a spin coating method, baking is performed at 300 ° C. for 60 seconds,
An intermediate film was formed.

[0110]

Embedded image

Further, a resist pattern was formed on the intermediate film in the same manner as in Example 1.

Next, the intermediate film was etched using a magnetron type etching apparatus, and the shape of the resist pattern was transferred to the intermediate film to form an intermediate film pattern. The etching condition here is that the source gas is CF ₄ / O ₂ / Ar = 2.
0/20/200 sccm, the degree of vacuum was 75 mTorr, the excitation power density was 2.0 W / cm ² , and the substrate temperature was 80 ° C.

When the degree of unevenness on the side wall of the resist pattern was examined, it was found to be 5.2 nm, which was an allowable amount.
Irregularities exceeding nm were generated. Silicon oxide-based materials such as spin-on-glass are hard to be etched by chlorine-based or bromine-based gas, and fluorine-based gas is mainly used for etching. However, when etching is performed using a fluorine-based gas, irregularities are easily generated on the side walls of the obtained resist pattern. As one of the causes, it is considered that when a fluorine-based gas is used, a fluorocarbon-based product is deposited unevenly on the side wall of the resist pattern.

As can be seen from the results of this comparative example, in the multilayer resist process according to the present invention, the intermediate film can be etched without using a fluorine-based gas. Therefore, by using the present invention, the intermediate film can be etched without increasing the unevenness of the resist pattern side wall.

Further, in the same manner as in Example 1, the selectivity to resist, dimensional conversion difference, and element composition ratio were examined. The results are shown in Table 1. As compared with (S1) to (S15), it was confirmed that the resist selectivity was low and the dimensional conversion difference was large. Thus, it can be seen that the multilayer resist process according to the present invention is also advantageous from the viewpoint of the dimensional conversion difference after the etching of the intermediate film.

Subsequently, the lower resist film was etched using a magnetron type etching apparatus in the same manner as in Example 1, and the shape of the intermediate film pattern was transferred to the lower resist film. FIG. 3 shows the result of observing the intermediate film pattern from above. As compared with FIG. 2 obtained in Example 1, it is understood that the unevenness on the side surface of the intermediate film pattern is large.

Further, when the unevenness on the side wall of the intermediate film pattern after the etching was examined, it was found that it was 13.6 nm, which exceeded the allowable amount of 5 nm. The reason is considered as follows. That is, since the intermediate film formed in this comparative example was spin-on-glass, (S
The composition is not uniform as compared with the intermediate films formed in 1) to (S15). For this reason, when processing the lower resist film, the etching tends to proceed non-uniformly, and unevenness on the side surface has increased.

The dimensional conversion difference caused by the etching of the lower resist film is defined as follows and is shown in Table 1 above. The dimensional conversion difference here is the difference (= Z−Y) between the dimension Z of the lower film pattern 109 shown in FIG. 1G and the dimension Y of the intermediate film pattern 108 shown in FIG. ). As shown in Table 1, the dimensional conversion difference is
It exceeded the allowable range of -5 to +5 nm, and the lower resist film could not be processed with good dimensional control.

Further, the selectivity of the intermediate film to the lower resist film was examined, and the results are shown in Table 1. Example 1 (S1)
The selection ratio is significantly lower than that of (S15). This is considered because the etching resistance of the intermediate film formed using spin-on-glass is low.

Embodiment 2 In this embodiment, an example in which an intermediate film is etched using a bromine-based gas will be described.

(S1) to (S15) described in the first embodiment
In this way, an intermediate film was formed. Further, a resist pattern 107 was formed on the intermediate film 105 as shown in FIG.

Next, the intermediate film 105 was etched using a magnetron type etching apparatus to transfer the shape of the resist pattern 107 to the intermediate film, thereby forming an intermediate film pattern 108 as shown in FIG. The etching conditions here were source gas HBr = 200 sccm, degree of vacuum 75 mTorr, excitation power density 2.0 W / cm ² , and substrate temperature 80 ° C.

After completion of the etching, the resist pattern was observed from above, and the least-square mean value of the irregularities on the side walls of the resist pattern was examined. When any intermediate film was used, it was 2.8 nm. It is less than 5 nm. Therefore, the intermediate film 105 could be etched while suppressing the unevenness of the side wall of the resist pattern.

The dimensional conversion difference caused by the etching of the intermediate film 105 was examined in the same manner as in Example 1, and the results are shown in Table 2 below.

[0125]

[Table 2]

As shown in Table 2, all the intermediate films were etched at a high selectivity of 6.3 or more. As a result, it prevents the resist pattern from falling off,
It is considered that the intermediate film could be etched without deviation from the resist pattern dimensions. (S1)-(S1
Comparing the selectivity with respect to the resist in 5), the selectivity with respect to the resist is higher as the dehydrogenation reaction sufficiently proceeds and the influence of oxidation is smaller. As a result, it is found that the processing conversion difference can be reduced, which is preferable.

As described above, in the present invention, even when the intermediate film is etched using the bromine-based gas,
As in the case of (1), the intermediate film pattern can be formed with good dimensional controllability by reducing the unevenness of the side wall.

(Embodiment 3) In this embodiment, an example in which a film to be processed containing carbon is formed as a lower layer film and processed by the method of the present invention will be described.

First, 10 g of polyarylene ether was dissolved in 90 g of isopropyl alcohol to prepare a solution material for a film to be processed. This solution material was applied on a silicon wafer by spin coating, and then baked on a hot plate at 450 ° C. for 180 seconds to form a 500 nm-thick interlayer insulating film as a film to be processed.

Next, an intermediate film having a thickness of 100 nm was formed on the film to be processed by the same method as in (S1) to (S15) of Example 1.

A resist pattern was formed on the obtained intermediate film in the same manner as in Example 1.

Next, in the same manner as in Example 1, the intermediate film was etched and the resist pattern was transferred to the intermediate film to form an intermediate film pattern. The unevenness of the resist pattern side wall, the dimensional conversion difference, and the etching selectivity were examined in the same manner as in Example 1, and the obtained results are summarized in Table 3 below.

[0133]

[Table 3]

As shown in Table 3, the same results as in Example 1 were obtained for all the intermediate films.

Next, the film to be processed was etched in the same manner as in Example 1, and the shape of the intermediate film pattern was transferred to the film to be processed to form a film pattern to be processed. When the cross-section processing shape was observed using a scanning electron microscope, FIG.
As shown in (g), it was confirmed that the line and space were processed with good anisotropy. Also, (S1) to (S1)
Observation of the intermediate film pattern of 15) from above revealed that in any case, as shown in FIG. 2, the film to be processed could be etched without excessively increasing the unevenness on the side surface of the pattern.

Further, the intermediate film pattern was observed from above, the least mean square value of the unevenness on the side wall was calculated, and the results are summarized in Table 3 together with the processing conversion difference and the selection ratio.

As shown in Table 3, as in the case of the first embodiment, the unevenness of each of (S1) to (S15) is 5
In the case of nm or less, the irregularities within the allowable range are suppressed. In the method of the present invention, the dehydrogenating unit is desorbed from the silicon compound constituting the intermediate film to promote the dehydrogenation reaction, so that the composition of the intermediate film can be made uniform. This makes it possible to reduce the surface roughness of the intermediate film and process the film to be processed with a good processing shape. Moreover,
Since the intermediate film formed by the method of the present invention has a sufficient etching resistance, a sufficient selectivity can be obtained and the film to be processed can be etched with good dimensional control.

[0138]

As described in detail above, according to the present invention,
A pattern forming method capable of forming a pattern with reduced side wall irregularities by using a multilayer resist process is provided.
In the present invention, since the silicon film formed by the coating method is used as an intermediate film in the multilayer resist process, it is possible to etch this intermediate film with a chlorine-based gas or a bromine-based gas. As a result, the intermediate film can be etched without increasing unevenness on the side wall of the resist pattern. In addition, since the composition of the intermediate film is uniform, it is possible to significantly reduce the occurrence of irregularities on the side wall of the intermediate film pattern when etching the lower film. Therefore, the lower layer film pattern can be obtained with good dimensional control without transferring the unevenness of the side wall of the intermediate film pattern to the lower layer film.

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.

FIG. 2 is a schematic diagram showing the shape of an intermediate film pattern observed from above after a lower film pattern is formed by the method of the present invention.

FIG. 3 is a schematic diagram showing the shape of an intermediate film pattern observed from above after forming a lower film pattern by a conventional multilayer resist process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Silicon wafer 102 ... Work film 103 ... Lower resist film 104 ... Intermediate film 105 ... Uniform intermediate layer 106 ... Resist film 107 ... Resist pattern 108 ... Intermediate layer pattern 109 ... Lower resist film pattern 201, 203 ... Intermediate Membrane pattern

Claims (15)

[Claims] 1. A step of forming an underlayer film containing carbon on a silicon wafer, and a silicon compound having a bond between silicon and silicon in a main chain and containing a desorbable unit on the underlayer film. Forming an intermediate film to be applied by a coating method; desorbing the silicon compound desorbing unit; forming a resist film on the uniformized intermediate film; Performing a pattern exposure and a development process to form a resist pattern; processing the intermediate film using the resist pattern as a mask to obtain an intermediate film pattern; and using the intermediate film pattern as a mask. Processing the lower layer film to obtain a lower layer pattern. 2. forming a film to be processed on the silicon wafer before forming the lower film on the silicon wafer; and processing the film to be processed using the lower film pattern as a mask; 2. The pattern forming method according to claim 1, further comprising a step of obtaining a film pattern to be processed. 3. The pattern forming method according to claim 1, wherein the step of desorbing the silicon compound desorbable unit is performed by heating. 4. The pattern forming method according to claim 3, wherein the heating is performed at a temperature of 100 ° C. or more and 1200 ° C. or less. 5. The pattern forming method according to claim 1, wherein the step of desorbing the silicon compound desorbable unit is performed by irradiating an energy beam. 6. The energy beam is selected from the group consisting of visible light, ultraviolet light, deep ultraviolet light, and X-rays, and the irradiation amount is 1 mJ / cm ² or more and 1000 J / cm ² or less. 6. The pattern forming method according to claim 5, wherein: 7. The energy beam is an electron beam, and the irradiation amount is 0.001 μC / cm ² or more.
0 C / cm ² or less, acceleration voltage is 0.001 to 1000
The pattern forming method according to claim 5, wherein the voltage is keV or less. 8. The method according to claim 1, wherein the step of detaching the detachable unit of the silicon compound is performed by dissolving and removing the detachable unit by treating the intermediate film with a solvent. The pattern forming method according to the above. 9. The pattern forming method according to claim 1, wherein the step of desorbing the silicon compound desorbable unit is performed in an atmosphere having an oxygen concentration of 1% or less. 10. The pattern forming method according to claim 1, wherein the step of desorbing the silicon compound desorbable unit is performed under a reduced pressure atmosphere of 1 Torr or less. 11. The step of obtaining an intermediate film pattern comprises using an etching gas containing a chlorine atom or a bromine atom,
The pattern forming method according to claim 1, wherein the method is performed by etching the intermediate film. 12. The composition of the intermediate film after desorbing the desorbable unit is as follows: Si is 40 atomic% or more, H is 60 atomic% or less, and O is 20 atomic%.
The pattern forming method according to any one of claims 1 to 11, wherein the ratio is c% or less. 13. The film thickness of the lower layer film is 20 nm or more and 1
The pattern forming method according to any one of claims 1 to 12, wherein the thickness is within a range of 0000 nm or less. 14. The film thickness of the intermediate film is 10 nm or more and 1
The pattern forming method according to any one of claims 1 to 13, wherein the thickness is within a range of 000 nm or less. 15. The pattern forming method according to claim 1, wherein a thickness of the resist film is in a range from 10 nm to 10,000 nm.