JP2001127037A - Method of forming minute pattern, and manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give a resist pattern an excellent etching resistance, concerning the method of forming a minute pattern including a new processing method for a resist pattern. SOLUTION: The film of a photoresist 1 is made on a silicon oxide film 2 (Fig. 2 (a)). The specified section of the photoresist is exposed to the light of 200 nm or under in wavelength (Fig. 2(b)). The photoresist 1a after exposure is developed and patterned (Fig. 2 (c)). The whole surface of the patterned photoresist 1a is irradiated with radiation 7 of 200 nm in wavelength (Fig. 2 (d)). After irradiation with radiation 7, a silicon oxide film 2 is etched, with the patterned photoresist 1a as a mask (Fig. 2 (e)).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a fine pattern and a method for manufacturing a semiconductor device, and more particularly to a method for forming a fine pattern including a novel method for processing a resist pattern, and a semiconductor device using the method. And a method for producing the same.

[0002]

2. Description of the Related Art In a process of forming a circuit pattern of an LSI or the like, a reduced projection exposure method is widely used. In recent years, in the exposure method, the resolution has been improved by shortening the wavelength of the exposure light. By using an ArF excimer laser (wavelength: 193 nm) instead of the KrF excimer laser (wavelength: 248 nm), which has been widely used in the past, it is possible to reduce the number of laser beams to 0.1.
It is believed that processing at the 1 μm level becomes possible.

In the exposure using an ArF excimer laser, problems such as deterioration of the pattern shape due to light absorption of the photoresist, sensitivity of the photoresist, and the like arise. For this reason, a chemically amplified resist with low light absorption and high sensitivity has been developed, and various studies have been made toward practical use. Among them, a chemically amplified resist having a basic skeleton of a resin containing no aromatic ring such as polymethyl methacrylate (PMMA) has been studied. However, since these materials do not contain an aromatic ring, their dry etching resistance is not sufficient. Therefore, it has been proposed that a functional group having high etching resistance such as an adamantyl group is ester-bonded to a resin (Japanese Patent No. 2881969).
issue). Also, it has been found that a photoresist containing a polymerization product of a monomer containing an alicyclic hydrocarbon moiety and a maleic anhydride monomer or a polymerization product of a norbornene monomer as a main component also exhibits high resolution. (JP-A-10-10739, JP-A-10-207070).

[0004]

However, in experiments conducted by us, when the underlying substrate was etched using a gas containing fluorine atoms through a resist pattern made of a resin as described above, the photoresist was not etched. It was found that the surface became rough. FIG. 1A is an SEM image of a roughened photoresist surface, one side of which is 1.7 μm.
Is equivalent to FIG. 1B shows the SE of the cross section of the resist.
M image. The reason why the surface of the photoresist is roughened is that the etching rate of the photoresist locally increases as the etching of the photoresist proceeds. In a portion where the etching rate is locally increased, the possibility that the underlayer is etched increases, and it becomes difficult to form a high-definition fine pattern.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and can accurately form a resist pattern by lithography using a wavelength of 200 nm or less, and can form a fine pattern on an underlying substrate. It is a first object of the present invention to provide a method for forming a fine pattern, which can prevent the etching rate of a photoresist from locally increasing in a forming step. A second object of the present invention is to provide a method of manufacturing a semiconductor device using such a method of forming a fine pattern.

[0006]

The inventors of the present invention have studied the causes of roughness on the surface of the photoresist. As a result, when a photoresist having a wavelength of 200 nm or less is irradiated on the patterned photoresist prior to the etching process, the photoresist surface is exposed. It has been found that the roughness of the surface can be suppressed. (1) Therefore, a method for forming a fine pattern according to the present invention is a method for forming a fine pattern using a photoresist patterned into a desired pattern as a mask,
Forming a photoresist film on an underlying substrate, exposing a predetermined portion of the photoresist film to light having a wavelength of 200 nm or less, developing the exposed photoresist, and applying the photoresist to the photoresist. A step of patterning into a desired pattern, a step of performing a pretreatment of irradiating light having a wavelength of 200 nm or less to the entire surface of the patterned photoresist, and after the pretreatment, using the patterned photoresist as a mask, Forming a fine pattern on a photoresist underlayer.

According to the present invention, it is possible to prevent the etching rate of a photoresist from being locally increased in a fine pattern forming step involving etching, ion implantation, and the like, thereby preventing the surface of a resist pattern from being greatly roughened. Can be prevented.

(2) The pretreatment preferably includes a step of irradiating the photoresist with light having a wavelength of 200 nm or less at an irradiation intensity of 3 (J / cm ² ) or more. When this condition is satisfied, the roughness of the resist surface in the fine pattern forming step can be sufficiently suppressed.

(3) When the thickness of the photoresist to be removed in the step of forming the fine pattern is T (nm), the photoresist is exposed to light used in the pre-processing. It is desirable to exhibit a transmittance of 10% or more per film thickness T (nm). When the transparency of the photoresist is low, very large light energy is required to modify the film quality of the photoresist over the entire film thickness. When the light used in the pretreatment has such a large energy, the light energy supplied near the surface of the photoresist becomes excessive, and the polymer cutting reaction easily proceeds in the photoresist. Is reduced. According to the present invention, since excellent etching resistance can be imparted to the entire photoresist without such inconvenience, a sufficient process margin in the fine pattern forming step can be ensured.

(4) In the pretreatment, the concentration of ozone contained in the atmosphere around the photoresist is 2 × 10
It is desirable to carry out in a state of ^-7 (mol / l) or less. Oxygen contained in the atmosphere easily changes to ozone when receiving light having a wavelength of 200 nm or less. Ozone chemically etches the photoresist, so that when its concentration is high, the thickness of the photoresist may decrease. According to the present invention, it is possible to effectively prevent the thickness of the photoresist from being reduced in the course of the pretreatment, and thus a sufficient process margin in the fine pattern forming step can be secured.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Elements common to the drawings are denoted by the same reference numerals, and redundant description will be omitted.

Embodiment 1 Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. In Embodiment 1, Examples 1 to 5 of the method for forming a fine pattern according to the present invention, and Comparative Examples 1 to 5 used for comparison therewith.
4 will be described.

FIG. 2 shows Examples 1 to 5 and Comparative Examples 1 to 4.
FIG. 4 is a view for explaining a method for forming a fine pattern in FIG. In FIG. 2, reference numeral 1 denotes a photoresist, and reference numeral 1 denotes
a is a photoresist after patterning, 1b is a photoresist after etching of a base substrate, 2 is a silicon oxide (SiO ₂ ) film, 3 is a silicon nitride (SiN) film, and 4 is a silicon substrate. , Symbols 5 and 6 indicate a mask and exposure light used for exposing the photoresist 1. Reference numeral 7 denotes radiation.

In the fine pattern forming methods of Examples 1 to 5 and Comparative Examples 1 to 4, as shown in FIG. 2A, a parallel plate type plasma CVD device manufactured by ASM Japan was used. A silicon nitride film 3 having a thickness of 52 nm and a silicon oxide film 2 having a thickness of 800 nm are sequentially formed. Next, a photoresist 1 is formed on the silicon oxide film 2 by a spin coating method.

In the step of applying the photoresist 1, first,
After the silicon oxide film 2 is formed, the substrate is heated at 90 ° C. in a hexamethyldisilazane (HMDS) atmosphere at 60 ° C.
Exposure for seconds. Next, an ArF excimer laser lithography resist (PAR-101) containing methacrylic acid ester manufactured by Sumitomo Chemical Co., Ltd. is applied with a thickness of 600 nm.
Thereafter, the substrate is heated to 120 ° C. on a hot plate for 60 seconds. As a result, the state shown in FIG. 2A is formed.

Next, exposure of a contact hole pattern is performed by a prototype ArF excimer laser stepper manufactured by ISI (FIG. 2B). Exposure equipment N
A (Numerical Aperture) is 0.6 and σ is 0.7.

Thereafter, the substrate is heated to 120 ° C. for 60 seconds on a hot plate, and a developing process is performed by a paddle method using an organic alkaline aqueous solution such as an aqueous solution of tetramethylammonium hydroxide (TMAH) as a developing solution. As a result, a photoresist 1a having a contact hole pattern having a diameter of 160 nm is formed (FIG. 2C).

Next, as a pretreatment for etching, radiation 7 is applied to the entire surface of the substrate (FIG. 2D). Table 1 shows the type and intensity setting of the radiation 7 used in each of Comparative Examples 1 to 4 and Examples 1 to 5. In this step, the substrate temperature was set at 25 ° C.

[0019]

[Table 1]

Next, the silicon oxide film 2 is etched using the resist pattern 1a obtained by the above processing as a mask. As a result, the pattern of the contact hole is transferred to the silicon oxide film 2 (FIG. 2E). In this embodiment, the above-mentioned etching is performed using a parallel plate type prototype etching apparatus manufactured by Tokyo Electron Limited, and C ₄ F ₈ (11 sccm) is used as an etching gas.
This is performed using a mixed gas of / O ₂ (8 sccm) / Ar (400 sccm). At this time, the pressure in the etching chamber is 3
0mtorr, plasma power of upper electrode is 2000W
(27 MHz), the plasma power of the lower electrode is 1200
W (800 kHz), and the wafer temperature was set at -20 ° C.

The cross section of the resist pattern 1b thus obtained is scanned with a scanning electron microscope (S-5000, manufactured by Hitachi, Ltd.).
As a result of observation in Examples 1 to 5, and Comparative Examples 1 to 4
A clear difference was found in the state of the resist pattern 1b between the case of FIG. FIG. 3A is a cross-sectional view of a substrate processed by the method of Comparative Examples 1-4, and FIG. 3B is a cross-sectional view of a photoresist 1b processed by the method of Examples 1-5. .
As shown in these figures, the roughness of the surface of the photoresist 1b formed by the method of Examples 1 to 5 is the same as that of Comparative Example 1.
4 was smaller than the roughness of the surface of the photoresist 1b formed by the method described in any one of (1) to (4).

Next, we describe the surface roughness of the resist pattern as “3σ of the variation in the remaining amount of the resist in the unexposed portion.
The value d was quantified (see FIG. 2).
(E)). Note that an atomic force microscope (AFM) was used to measure the variation in the remaining film amount. Surface roughness d from our experiments
Is smaller than 50 nm, it is known that the dimensional accuracy of the pattern formed by etching does not decrease.

The column of "surface roughness d (nm)" in Table 1 shows the value of the surface roughness d determined by the above-described method. As is clear from Table 1, when the photoresist is irradiated with radiation having a wavelength of 200 nm or less as a pretreatment for etching,
The surface roughness d can be suppressed to 50 nm or less. As described above, according to the methods of Embodiments 1 to 5, the surface roughness of the photoresist 1 in the etching step can be effectively suppressed.

In the first embodiment, by exposing the silicon substrate 4 to an HMDS atmosphere immediately before the application of the photoresist 1, an adhesion layer for improving the adhesion to the photoresist 1 is formed on the surface of the substrate. are doing. However, the present invention is not limited to this, and the formation of this adhesion layer may be omitted if the adhesion between the photoresist 1 and its base can be sufficiently ensured.

Further, in the method of the first embodiment, in the resist pattern exposure step, reduced exposure using an ArF excimer laser is performed. However, the exposure method is not limited to this, and other methods are used. Is also good. For example, electron beam exposure, KrF excimer laser contact exposure or reduction projection exposure, F ₂ excimer laser contact exposure or reduction projection exposure, ultraviolet step and scan reflective reduction projection exposure as a light source, or it is used soft X-rays it can.

In the method of the first embodiment, NA and σ of the exposure apparatus are set to 0.6 and 0.7, respectively, but their values are not limited to these values.
The resist film thickness is also optional as long as a sufficient amount of the remaining film is secured after the underlayer etching step. The transfer pattern is not limited to the contact hole, but may be a line pattern, a groove pattern, or the like.

In the first embodiment, the underlying film to be etched is the silicon oxide film 2, but the underlying film is
It may be a silicon nitride film, a titanium nitride film, a tungsten film, a silicon oxynitride film, a polysilicon film, or the like.

In the first embodiment, the etching gas
As C_FourF₈/ O_Two/ Ar mixed gas is used
However, the etching gas is not limited to this,
CF _Four, CHF_Three, C_TwoF₆, C_FiveF₈A fluorine atom such as
Any etching gas containing is used in the method of the present embodiment.
can do. Other ranges obvious to those skilled in the art
Various modifications, improvements, combinations, etc. are possible.

In the process of manufacturing the semiconductor device, after forming the photoresist 1a shown in FIG. 2C using the method of the first embodiment, the underlying silicon oxide film 2 is formed via the resist pattern 1a. Alternatively, by etching both the silicon oxide film 2 and the silicon nitride film 3, a fine pattern of an insulating film constituting a semiconductor device can be formed.

When the underlying film of the photoresist 1a is a conductive film, the conductive film is etched using the method of the first embodiment in the process of manufacturing the semiconductor device, so that the conductive film forming the semiconductor device is formed. A fine pattern of the film can be formed. Thereafter, the semiconductor device is manufactured through a series of manufacturing steps, but the description of those steps is omitted.

Further, in the first embodiment, a fine pattern is formed by performing etching using the photoresist 1a as a mask after completion of the pretreatment, but the present invention is not limited to this. That is, the photoresist 1a that has been subjected to the pretreatment can be used as a mask when implanting ions into the silicon substrate 4. In this case, since the surface roughness of the photoresist 1a is suppressed, it is possible to accurately form a pattern such as a source / drain region of a transistor, for example.

As described above, according to the fine pattern forming method of the first embodiment, after a pattern is formed on a photoresist, a wavelength of 2 is used as a pretreatment for etching.
Radiation 7 of 00 nm or less is applied to the entire surface of the substrate. As a result, in the step of etching the base film using the photoresist as a mask, it is possible to effectively prevent the etching rate of the photoresist from being locally large. Therefore, the method of Embodiment 1 (Example 1)
According to the methods (1) to (5), a fine and highly accurate pattern of an insulating film or a conductive film can be formed, and a semiconductor device having such a fine pattern can be manufactured.

Embodiment 2 FIG. Hereinafter, a second embodiment of the present invention will be described with reference to FIG. In Embodiment 2, Examples 6-1 of the fine pattern forming method according to the present invention will be described.
2, and Comparative Examples 5 to 8 used for comparison therewith will be described.

Examples 6 to 12 of the present invention and Comparative Examples 5 to
8 can be described with reference to FIGS. 2A to 2E as in the first embodiment. In the fine pattern forming method according to the second embodiment, a parallel plate type plasma CVD device manufactured by ASM Japan is used.
As shown in FIG. 2A, a silicon nitride film 3 having a thickness of 53 nm and a silicon oxide film 2 having a thickness of 800 nm are sequentially formed on a substrate 4. Next, a photoresist 1 is formed on the silicon oxide film 2 by a spin coating method.

In the step of applying the photoresist 1, first,
After the silicon oxide film 2 is formed, the substrate is heated in a hexamethyldisilazane (HMDS) atmosphere at 110 ° C. for 1 hour.
Exposure is for 20 seconds. Next, a resist for ArF excimer laser lithography manufactured by Tokyo Ohka Kogyo Co., Ltd. having a thickness of 600 nm, which is mainly composed of a polymerization product of a monomer containing an alicyclic hydrocarbon portion and a maleic anhydride monomer, is applied. Then, the substrate is placed on a hot plate for 1 second for 60 seconds.
Heat to 30 ° C. As a result, the state shown in FIG. 2A is formed.

Next, exposure of a contact hole pattern is performed by a Nikon prototype ArF excimer laser stepper (NSR-S302A) (FIG. 2B). The NA of the exposure apparatus is 0.6 and σ is 0.75.

Thereafter, the substrate is placed on a hot plate at 6
The mixture is heated to 130 ° C. for 0 second, and a developing process is performed by a paddle method using an organic alkaline aqueous solution such as an aqueous solution of tetramethylammonium hydroxide (TMAH) as a developer. As a result, a photoresist 1a having a contact hole pattern with a diameter of 150 nm is formed (FIG. 2C).

Next, as a pretreatment for the etching, the entire surface of the substrate is irradiated with radiation 7 (FIG. 2D). As an irradiation source of the radiation 7, an excimer lamp irradiation device (UVS-4200) manufactured by Ushio Inc. was used. The center wavelength of the irradiation light in this apparatus is 172 nm. Table 2 shows Examples 6 to 12.
The irradiation energy used in each of Comparative Examples 5 to 8 is shown.

[0039]

[Table 2]

Next, the silicon oxide film 2 is etched using the resist pattern 1a obtained by the above processing as a mask. As a result, the pattern of the contact hole is transferred to the silicon oxide film 2 (FIG. 2E). In this embodiment, the above-mentioned etching is performed using a parallel plate type prototype etching apparatus manufactured by Tokyo Electron Limited, and C ₄ F ₈ (11 sccm) is used as an etching gas.
This is performed using a mixed gas of / O ₂ (6 sccm) / Ar (350 sccm). At this time, the pressure in the etching chamber is 2
5mtorr, plasma power of upper electrode is 2000W
(27 MHz), the plasma power of the lower electrode is 1000
W (800 kHz), wafer temperature to -20 ° C,
The etching processing time was set to 2 minutes.

The surface roughness of the thus obtained resist pattern 1b was measured by AFM. The column of “surface roughness d (nm)” in Table 2 shows the value of the surface roughness d measured as described above. From the results shown in Table 2, when the irradiation energy of the radiation 7 is set to 3 (J / cm ² ) or more, the roughness d of the resist surface can be suppressed to 50 nm or less, and highly accurate pattern transfer can be performed. I understood.

In the method of the second embodiment, the substrate is exposed to an HMDS atmosphere to form an adhesion layer immediately before coating the photoresist 1 on the substrate. Is sufficient, this adhesion layer may be omitted.

In the method of the second embodiment, the reduction exposure using the ArF excimer laser is performed in the exposure step of the resist pattern. However, the exposure method is not limited to this, and other methods may be used. Is also good. For example, electron beam exposure, KrF excimer laser contact exposure or reduction projection exposure, F ₂ excimer laser contact exposure or reduction projection exposure, ultraviolet step and scan reflective reduction projection exposure as a light source, or it is used soft X-rays it can.

In the method of the second embodiment, NA and σ of the exposure apparatus are set to 0.6 and 0.75, respectively, but their values are not limited to these values. The resist film thickness is also optional as long as a sufficient amount of the remaining film is secured after the completion of the base etching process. Further, the transfer pattern is not limited to the contact hole, but may be a line pattern or a groove pattern.

In the second embodiment, the underlying film to be etched is the silicon oxide film 2, but the underlying film is
It may be a silicon nitride film, a titanium nitride film, a tungsten film, a silicon oxynitride film, a polysilicon film, or the like.

In the second embodiment, the etching gas
As C_FourF₈/ O_Two/ Ar mixed gas is used
However, the etching gas is not limited to this,
CF _Four, CHF_Three, C_TwoF₆, C_FiveF₈Contains fluorine such as
Any etching gas is used in the method of the present embodiment.
be able to. In addition, to the extent obvious to those skilled in the art
Various changes, improvements, combinations, and the like are possible.

In the process of manufacturing the semiconductor device, using the method of the second embodiment, after forming the photoresist 1a shown in FIG. 2C, the underlying silicon oxide film 2 is formed via the resist pattern 1a. Alternatively, by etching both the silicon oxide film 2 and the silicon nitride film 3, a fine pattern of an insulating film constituting a semiconductor device can be formed.

When the underlying film of the photoresist 1a is a conductive film, the conductive film is etched through the resist pattern 1a by using the method of the second embodiment in the process of manufacturing the semiconductor device. Thus, a fine pattern of a conductive film included in a semiconductor device can be formed. After that, the semiconductor device is manufactured through a series of manufacturing processes,
The description of those steps is omitted.

In the second embodiment, a fine pattern is formed by performing etching using the photoresist 1a as a mask after the completion of the pretreatment, but the present invention is not limited to this. That is, the photoresist 1a that has been subjected to the pretreatment can be used as a mask when implanting ions into the semiconductor substrate.
In this case, since the surface roughness of the photoresist 1a is suppressed, it is possible to accurately form a pattern such as a source / drain region of a transistor, for example.

As described above, according to the fine pattern forming method of Embodiment 2 (Examples 6 to 12), after forming a pattern on a photoresist, 3 ( Radiation 7 having an irradiation energy of J / cm ² or more is applied. As a result, it is possible to effectively suppress a local increase in the etching rate of the photoresist in the process of etching the base film using the photoresist as a mask. Therefore,
According to the fine pattern forming method of the second embodiment (Examples 6 to 12), a fine pattern of an insulating film or a conductive film can be formed with high accuracy, and a semiconductor device having such a fine pattern can be formed. Can be manufactured.

Embodiment 3 FIG. Hereinafter, a third embodiment of the present invention will be described with reference to FIG. In Embodiment 3, Embodiments 13 to 13 of the method for forming a fine pattern according to the present invention will be described.
16 and Modifications 1 to 4 based on them.

Embodiments 13 to 16 and Modification 1 of the Present Invention
4A to 4E can be described with reference to FIGS. 2A to 2E as in the first or second embodiment. In the method for forming a fine pattern according to the present embodiment, as shown in FIG. 2A, a silicon oxynitride film having a thickness of 25 nm is formed on a substrate 4 using a parallel plate type plasma CVD apparatus manufactured by ASM Japan. SiON film), and a silicon oxide film 2 having a thickness of 700 nm is formed thereon.
Is formed. Next, a photoresist 1 is formed on the silicon oxide film 2 by a spin coating method.

In the step of applying the photoresist 1, first,
After the silicon oxide film 2 is formed, the substrate is heated at 110 ° C. in a hexamethyldisilazane (HMDS) atmosphere.
Exposure is for 0 seconds. Next, a resist (MRC1001) for ArF excimer laser lithography (MRC1001) manufactured by Mitsubishi Rayon Co., Ltd. and containing methacrylic acid ester as a main component is applied to a thickness of 600 nm. Thereafter, the substrate is heated to 120 ° C. on a hot plate for 60 seconds. As a result, the state shown in FIG. 2A is formed.

Next, exposure of the contact hole pattern is performed by an ArF excimer laser exposure device manufactured by Canon Inc. (FIG. 2B). The NA of the exposure apparatus is 0.6 and σ is 0.7.

Then, on a hot plate for 60 seconds,
The substrate is heated to 120 ° C., and a developing process is performed by a paddle method using an organic alkaline aqueous solution such as an aqueous solution of tetramethylammonium hydroxide (TMAH) as a developing solution. As a result, a photoresist 1a having a contact hole pattern with a diameter of 180 nm is formed (FIG. 2C).

Next, as a pretreatment for the etching, the entire surface of the substrate is irradiated with radiation 7 (FIG. 2D). Table 3 shows the settings for the wavelength and intensity of the radiation used in each of Examples 13 to 16 and Modifications 1 to 4. The desired wavelength was obtained by filtering the deuterium lamp. The set value of the substrate temperature is −10 ° C. in all of Embodiments 13 to 16 and Comparative Examples 1 to 4.

[0057]

[Table 3]

The silicon oxide film 2 is etched using the resist pattern 1a obtained by the above processing as a mask. As a result, the pattern of the contact hole is transferred to the silicon oxide film 2 (FIG. 2E). In this embodiment, the above etching is performed using a surface wave plasma etching apparatus (Wave-X4000) manufactured by Sumitomo Metal Industries, Ltd., and Ar (1000 sccm) / C as an etching gas species.
₄ F ₈ (30 sccm) / O ₂ (12 sccm) / CO (60 sccm)
This is performed using a mixed gas. At this time, the pressure in the etching chamber was 40 mtorr, the plasma power of the upper electrode was 2900 W, and the plasma power of the lower electrode was 180 mtorr.
It was set to 0W. The lower electrode temperature was set to 0 ° C., and the etching processing time was set to 5 minutes. When the above etching is performed, the photoresist 1a has a thickness of 200 nm.
Removed to a degree.

In Table 3, “Transmittance of resist (% / 2)
The column of “00 nm)” indicates the transmittance of the resist with respect to the wavelength of the radiation 7 used in the pretreatment for etching, more specifically, the thickness of the resist removed by the above-described etching (200 nm in this embodiment). Shows the transmittance of the resist.

When the transmittance of the photoresist is low, very large light energy is required to modify the film quality of the photoresist over the entire film thickness. If the light used in the pretreatment has such a large energy, the energy of the light facilitates the polymer cleavage reaction, especially near the surface of the photoresist. As the polymer cleavage reaction progresses, the thickness of the photoresist decreases. For this reason, as shown in Table 3, the resist residual film amount after the pretreatment becomes smaller as the resist transmittance is lower and a larger required energy is required.

From the results shown in Table 3, it can be seen that when the resist transmittance per film thickness removed by etching is 10% or more, a sufficiently large resist remaining film amount can be secured after the pretreatment. Therefore, in the method of the present embodiment,
By setting the resist transmittance to 10% or more, a particularly large process margin in the etching step can be secured.

In the method of the third embodiment, the substrate is exposed to an HMDS atmosphere to form an adhesion layer immediately before coating the photoresist 1 on the substrate. Is sufficient, this adhesion layer forming step may be omitted.

Further, in the method of the third embodiment, in the resist pattern exposure step, reduced exposure using an ArF excimer laser is performed. However, the exposure method is not limited to this, and another method is used. Is also good. For example, electron beam exposure, KrF excimer laser contact exposure or reduction projection exposure, F ₂ excimer laser contact exposure or reduction projection exposure, ultraviolet step and scan reflective reduction projection exposure as a light source, or it is used soft X-rays it can.

In the method of the third embodiment, NA and σ of the exposure apparatus are set to 0.6 and 0.7, respectively, but their values are not limited to these values.
The resist film thickness is also arbitrary as long as a sufficient film thickness is secured after the base etching process is completed. The transfer pattern is not limited to the contact hole, but may be a line pattern, a groove pattern, or the like.

In the third embodiment, the underlying film to be etched is the silicon oxide film 2, but the underlying film is
It may be a silicon nitride film, a titanium nitride film, a tungsten film, a silicon oxynitride film, a polysilicon film, or the like.

In the third embodiment, the etching gas
As C_FourF₈/ O_Two/ Ar mixed gas is used
However, the etching gas is not limited to this,
CF _Four, CHF_Three, C_TwoF₆, C_FiveF₈A fluorine atom such as
Any known etching gas containing
Can be used for Other, obvious to those skilled in the art
Various changes, improvements, combinations, etc. are possible within a reasonable range.
You.

In the process of manufacturing the semiconductor device, after the photoresist 1a shown in FIG. 2C is formed using the method of the third embodiment, the underlying silicon oxide film 2 is formed via the resist pattern 1a. Alternatively, by etching both the silicon oxide film 2 and the silicon nitride film 3, a fine pattern of an insulating film constituting a semiconductor device can be formed.

When the underlying film of the photoresist 1a is a conductive film, the conductive film is etched through the resist pattern 1a by using the method of the third embodiment in the process of manufacturing the semiconductor device. Thus, a fine pattern of a conductive film included in a semiconductor device can be formed. After that, the semiconductor device is manufactured through a series of manufacturing processes,
The description of those steps is omitted.

Further, in the third embodiment, a fine pattern is formed by performing etching using the photoresist 1a as a mask after completion of the pretreatment, but the present invention is not limited to this. That is, the photoresist 1a that has been subjected to the pretreatment can be used as a mask when implanting ions into the semiconductor substrate.
In this case, since the surface roughness of the photoresist 1a is suppressed, it is possible to accurately form a pattern such as a source / drain region of a transistor, for example.

As described above, in the method for forming a fine pattern according to the third embodiment, the resist transmittance per resist film thickness T (nm) removed in the etching step of the base substrate is determined by the central wavelength of the radiation 7. Is desirably set so as to be 10% or more with respect to. That is, it is desirable that the settings of Modifications 2 to 4 be performed. According to such a setting, the remaining film amount of the photoresist 1b can be sufficiently secured at the start of the etching process. Therefore, the process margin in the etching process can be particularly reduced while sufficiently suppressing the roughness d of the resist surface due to the etching. It is possible to secure a large amount.

Embodiment 4 Hereinafter, Embodiment 4 of the present invention will be described with reference to FIG. In the fourth embodiment, examples 17 to 17 of the fine pattern forming method according to the present invention will be described.
20 and Modifications 5 to 7 based thereon will be described.

Embodiments 17 to 20 and Modification 5 of the Invention
The method for forming a fine pattern according to any one of the first to third embodiments
The description can be made with reference to FIGS. 2A to 2E as in the case of FIG. In the method for forming a fine pattern according to the fourth embodiment, a silicon nitride film 3 having a thickness of 55 nm is formed on a substrate 4 by using a parallel plate type plasma CVD device manufactured by ASM Japan as shown in FIG. After the formation, a silicon oxide film 2 having a thickness of 800 nm is formed thereon. Next, a photoresist 1 is formed on the silicon oxide film 2 by a spin coating method.

In the step of applying the photoresist 1, first,
After the silicon oxide film 2 is formed, the substrate is heated in a hexamethyldisilazane (HMDS) atmosphere at 110 ° C. for 1 hour.
Exposure is for 80 seconds. Next, a resist (SAIL-X09) for ArF excimer laser lithography (manufactured by Shin-Etsu Chemical Co., Ltd.) containing methacrylic acid ester as a main component is applied to a thickness of 1000 nm. The state shown in FIG. 2A is formed by performing an appropriate baking process.

Next, exposure of a contact hole pattern is performed by a Nikon ArF excimer laser exposure apparatus (NSR-S302A) (FIG. 2B). The NA of the exposure apparatus is 0.
6, σ is 0.75.

Then, on a hot plate for 60 seconds,
The substrate is heated to 130 ° C., and a developing process is performed by a paddle method using an organic alkaline aqueous solution such as an aqueous solution of tetramethylammonium hydroxide (TMAH) as a developing solution. As a result, a photoresist 1a having a contact hole pattern with a diameter of 250 nm is formed (FIG. 2C).

Next, as a pretreatment for etching, a wavelength 1
Radiation 7 of 72 nm is applied to the entire surface of the substrate (FIG. 2).
(D)). In the present embodiment, the pretreatment is performed with an irradiation amount of 5 (J / cm ² ) by installing an excimer lamp irradiation device in a sealable chamber. The irradiation device described above includes an excimer lamp device (UVS420 manufactured by Ushio Inc.).
0) was used.

[0077] Nitrogen and oxygen can be fed into the chamber containing the irradiation device at an arbitrary concentration ratio. By reducing the concentration of oxygen fed into the chamber and filling the inside with nitrogen gas, the amount of ozone generated during the pretreatment step can be reduced, and the ozone concentration in the chamber can be reduced. Table 4 shows the amount of ozone contained in the chamber during the pretreatment step in each of Examples 17 to 20 and Comparative Examples 5 to 7.

[0078]

[Table 4]

Oxygen contained in the atmosphere easily changes to ozone when it receives light having a wavelength of 200 nm or less. Ozone is
Since the photoresist is chemically etched, if the concentration is high, the thickness of the photoresist 1a decreases during the pretreatment. For this reason, as shown in Table 4, the resist remaining film amount after the pre-treatment becomes smaller as the ozone concentration in the chamber during the pre-treatment becomes higher.

When the above pretreatment is completed, the silicon oxide film 2 is etched next using the resist pattern 1a as a mask. As a result, the pattern of the contact hole is transferred to the silicon oxide film 2 (FIG. 2E). In the present embodiment, the above etching is performed by Sumitomo Metal Industries, Ltd.
Using a surface wave plasma etching apparatus (Wave-X4000) manufactured by Co., Ltd., and using Ar (1000 sc
cm) / C ₄ F ₈ (30 sccm) / O ₂ (12 sccm) / CO (6
0 sccm) using a mixed gas. At this time, the pressure in the etching chamber was set to 40 mtorr, the plasma power of the upper electrode was set to 2900 W, and the plasma power of the lower electrode was set to 180 W. Furthermore, the lower electrode temperature is 0 ° C,
The etching time was set to 2 minutes.

By performing the above etching, the photoresist 1a is removed to some extent. Therefore, in order to secure a sufficient process margin in the etching step, it is desirable that a large resist remaining film be secured before the processing is started.

[0082] Table as shown in 4, before the case ozone concentration in the chamber during processing execution is 2.0 × 10 ^{over 7} (mol / l) or less, sufficiently pretreatment residual resist film amount after It can be seen that it can be secured. Therefore, in the method of this embodiment, the ozone concentration in the chamber is 2.0 × 10 ^{over 7} (mol /
l) By executing preprocessing under the following settings,
A particularly large process margin in the etching step can be secured.

In the method according to the fourth embodiment, the substrate is exposed to an HMDS atmosphere to form an adhesion layer immediately before coating the photoresist 1 on the substrate. Is sufficient, this adhesion layer forming step may be omitted.

Further, in the method of the fourth embodiment, in the resist pattern exposure step, reduced exposure using an ArF excimer laser is performed, but the exposure method is not limited to this, and other methods are used. Is also good. For example, electron beam exposure, KrF excimer laser contact exposure or reduction projection exposure, F ₂ excimer laser contact exposure or reduction projection exposure, ultraviolet step and scan reflective reduction projection exposure as a light source, or it is used soft X-rays it can.

In the method of the fourth embodiment, the NA and σ of the exposure apparatus are set to 0.6 and 0.75, respectively, but their values are not limited to these values. The resist film thickness is also arbitrary as long as a sufficient film thickness is secured after the base etching process is completed. The transfer pattern is not limited to the contact hole, but may be a line pattern, a groove pattern, or the like.

In the method of the fourth embodiment, the processing chamber is filled with nitrogen gas in order to reduce the concentration of ozone generated during the pretreatment for etching. Is not limited to this. For example, the inside of the processing chamber may be evacuated to reduce the ozone concentration.

In the fourth embodiment, the underlying film to be etched is the silicon oxide film 2, but the underlying film is
It may be a silicon nitride film, a titanium nitride film, a tungsten film, a silicon oxynitride film, a polysilicon film, or the like.

In the fourth embodiment, the etching gas
As C_FourF₈/ O_Two/ Ar mixed gas is used
However, the etching gas is not limited to this,
CF _Four, CHF_Three, C_TwoF₆, C_FiveF₈A fluorine atom such as
Any known etching gas containing
Can be used for Other, obvious to those skilled in the art
Various changes, improvements, combinations, etc. are possible within a reasonable range.
You.

In the process of manufacturing the semiconductor device, after forming the photoresist 1a shown in FIG. 2C using the method of the third embodiment, the underlying silicon oxide film 2 is formed via the resist pattern 1a. Alternatively, by etching both the silicon oxide film 2 and the silicon nitride film 3, a fine pattern of an insulating film constituting a semiconductor device can be formed.

When the underlying film of the photoresist 1a is a conductive film, the conductive film is etched through the resist pattern 1a by using the method of the third embodiment in the process of manufacturing the semiconductor device. Thus, a fine pattern of a conductive film included in a semiconductor device can be formed. After that, the semiconductor device is manufactured through a series of manufacturing processes,
The description of those steps is omitted.

In the fourth embodiment, the fine pattern is formed by performing etching using the photoresist 1a as a mask after the completion of the pretreatment, but the present invention is not limited to this. That is, the photoresist 1a that has been subjected to the pretreatment can be used as a mask when implanting ions into the semiconductor substrate.
In this case, since the surface roughness of the photoresist 1a is suppressed, it is possible to accurately form a pattern such as a source / drain region of a transistor, for example.

As described above, in the method for forming a fine pattern according to the fourth embodiment, the concentration of ozone contained in the atmosphere around the silicon substrate 4 in the pretreatment step of etching is 2 × 10 ⁻⁷ (mol / l). It is desirable that the following settings be made. That is, it is desirable that the settings of Modifications 5 to 7 be performed. According to such a setting, the remaining film amount of the photoresist 1b can be sufficiently secured at the start of the etching process. It is possible to secure a large value.

[0093]

Since the present invention is configured as described above, it has the following effects. According to the first aspect of the present invention, by irradiating the patterned photoresist with light having a wavelength of 200 nm or less, the etching resistance of the photoresist can be increased.
Therefore, according to the present invention, it is possible to form a fine pattern with high precision while preventing the surface of the resist pattern from being roughened during the formation of the fine pattern.

According to the second aspect of the present invention, it is possible to irradiate the photoresist with light having a sufficient intensity in the pretreatment stage. Therefore, according to the present invention, the etching characteristics of the photoresist can be sufficiently improved.

According to the third aspect of the present invention, since the photoresist has a sufficient transmittance, excellent etching resistance can be imparted to the entire photoresist without using excessive light energy. In this case, since the thickness of the photoresist does not decrease significantly with the execution of the pre-processing, a large process margin in the fine pattern forming step can be secured.

According to the fourth aspect of the present invention, since the pre-processing is performed in a state where the ozone concentration is sufficiently suppressed, the photoresist is effectively prevented from being etched by ozone during the execution of the pre-processing. can do. In this case, since the thickness of the photoresist does not decrease significantly with the execution of the pre-processing, a large process margin in the fine pattern forming step can be secured.

According to the fifth aspect of the present invention, a fine pattern can be formed on a base substrate with excellent accuracy by performing etching using a resist pattern having excellent etching resistance as a mask.

According to the sixth aspect of the present invention, by performing ion implantation using a resist pattern having excellent etching resistance as a mask, a fine pattern can be formed on the underlying substrate with excellent accuracy.

According to the seventh aspect of the present invention, it is possible to easily manufacture a semiconductor device having a fine pattern formed with high precision as a component.

[Brief description of the drawings]

FIG. 1 is an SEM image showing a state realized when a photoresist formed on a silicon substrate is etched by a conventional method.

FIG. 2 is a diagram for explaining a series of processes performed in the method for forming a fine pattern according to the first to fourth embodiments of the present invention.

FIG. 3 shows the state of the photoresist processed by the method for forming a fine pattern according to the first to fourth embodiments of the present invention (FIG. 3).
FIG. 4B is a diagram comparing the state of the photoresist treated by the method of the comparative example (FIG. 3A).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a, 1b Photoresist 2, 2 'Silicon oxide film 3 Silicon nitride film 4 Silicon substrate 5 Mask 6 Exposure light 7 Radiation

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshiyuki Matsuki 6409 Motoishikawacho, Aoba-ku, Yokohama-shi, Kanagawa Fushio Electric Co., Ltd. F-term (reference) 5F004 AA16 BA04 DA00 DA02 DA16 DA23 DA26 DB03 EA19 EA40 5F046 LA18 LA19

Claims (7)

[Claims] 1. A method for forming a fine pattern using a photoresist patterned into a desired pattern as a mask, comprising: forming a photoresist film on a base substrate; Exposing the photoresist to light having a wavelength of 200 nm or less, developing the photoresist after exposure, and patterning the photoresist into the desired pattern; and applying light having a wavelength of 200 nm or less to the entire surface of the patterned photoresist. Irradiating a pre-process; and, after the pre-process, using the patterned photoresist as a mask, forming a fine pattern in an underlayer of the photoresist. Forming method. 2. The method according to claim 1, wherein the pretreatment includes irradiating the photoresist with light having a wavelength of 200 nm or less at an irradiation intensity of 3 (J / cm ² ) or more. Method of forming a fine pattern. 3. When the thickness of the photoresist removed in the step of forming the fine pattern is T (nm), the photoresist has a thickness T with respect to light used in the pretreatment. 3. The method for forming a fine pattern according to claim 1, wherein the method exhibits a transmittance of 10% or more per (nm). 4. The method according to claim 1, wherein the concentration of ozone contained in the atmosphere around the photoresist is 2 × 10 ⁻⁷ (mol / l).
The method is performed in the following state, characterized in that:
The method for forming a fine pattern according to any one of the above items. 5. The method according to claim 1, wherein the step of forming the fine pattern includes a step of etching the underlayer of the photoresist using a gas containing fluorine atoms using the patterned photoresist as a mask. The method for forming a fine pattern according to claim 1. 6. The method according to claim 1, wherein the step of forming the fine pattern includes a step of implanting ions into an underlayer of the photoresist using the patterned photoresist as a mask. The method for forming a fine pattern according to claim 1. 7. A semiconductor device, comprising a step of forming a fine pattern as a component of a semiconductor device on the underlayer using the method according to claim 1. Manufacturing method.