JPH1195418A - Photoresist film and pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoresist film showing excellent durability against dry etching in which a pattern can be formed by using an ArF excimer laser, by comprising a chemical amplification-type lower resist film containing at least a benzene ring as the component element and a lower resist film which produces an acid. SOLUTION: The photoresist film consists of a chemical amplification-type lower resist film 2 containing at least a benzene ring as the component element and of an upper resist film 3 which has sensitivity for at least light from an ArF excimer laser and produces an acid. The photoresist film thus produced is exposed to ArF excimer laser light. While an acid is produced or after an acid is produced, the acid is made to amplify and diffuse in the lower chemical amplification-type resist in the normal direction of the substrate. Then the resist is developed. Further, after the acid is diffused in the normal direction of the substrate, the resist is heated to accelerate amplification and diffusion of the acid and then developed to form a resist pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a photoresist film for forming a pattern using an excimer laser and a method for forming a photoresist pattern.

[0002]

2. Description of the Related Art Semiconductor integrated circuits (hereinafter referred to as "LSIs") have been increasingly integrated year by year, and their design rules have been required to be finer. The light source used in the photolithography process is also i-line (wavelength 365).
nm) and KrF (wavelength 248 nm) excimer laser have been changed to ArF (wavelength 193 nm) excimer laser.

However, conventional resists for i-line and KrF excimer lasers cannot be used because they absorb ArF excimer lasers and their transparency is impaired. This light absorption is caused by the benzene ring in the composition of the resist.
Therefore, it is indispensable to use a resin not containing a benzene ring for the ArF excimer laser resist. In recent years, resists for ArF excimer lasers that satisfy this requirement have been developed.

The resists for ArF excimer lasers reported so far include, specifically, methacrylic acid,
Tert-butyl methacrylate and methyl methacrylate terpolymer resist, methacrylic acid, ter
tertiary copolymer resist of t-butyl methacrylate and adamantyl methacrylate, methacrylic acid, ter
quaternary copolymer resist of t-butyl methacrylate, methyl methacrylate and adamantyl methacrylate,
And the like.

[0005] These resists are chemically amplified resists which are generally used as resists exposed to a KrF excimer laser (resist which generates an acid by laser irradiation, and then performs a heat treatment to amplify the acid). As described above, by generating an acid by ArF excimer laser irradiation and then chemically amplifying the acid, it is possible to distinguish between a soluble region and an insoluble region in the developer. In addition, since these do not include any benzene ring in the composition, transparency can be maintained even for an ArF excimer laser.

[0006]

However, these Ars
The resist for F excimer laser is a conventional i-line and KrF
Dry etching resistance is generally inferior to that of resist for excimer laser. This is a new problem caused by removing the benzene ring from the resin composition. In other words, the benzene ring converts the energy of fast ions and fast electrons that collide during dry etching from the planar structure in the excited state to small vibration energy,
It works to reduce energy and return to the original planar structure.
As a result, a substance containing a benzene ring exhibits excellent dry etching resistance. Specifically, the novolak resin, which is widely used as an i-line resist, and the polyvinyl phenol resin, which is widely used as a KrF excimer laser resist, both have a large number of benzene rings. The obtained dry etching resistance can be obtained.

On the other hand, recently, a resist which does not contain a benzene ring and is intended to improve dry etching resistance has recently been disclosed in, for example, JP-A-7-333850 and JP-A-8-259.
No. 626.

However, since the resist disclosed in JP-A-7-333850 contains a sulfur component, sulfur precipitates on the side of the resist mask during dry etching, and the pattern shape after development is precisely dried. Cannot be transferred by etching. In addition, a sulfur component is precipitated in the etching apparatus, which causes a problem of contamination. Further, H ₂ S or SO ₂ generated during decomposition of the sulfur component emits a bad smell and is harmful. From the above viewpoints, a resist film containing a sulfur component is not suitable as a photoresist film.

In the resist disclosed in Japanese Patent Application Laid-Open No. Hei 8-259626, a bridged cyclic hydrocarbon is bonded in a resin. Although the bridged cyclic hydrocarbon itself is excellent in dry etching resistance, Almost no solubility in the developer. Therefore, a resist containing a large amount of a bridged cyclic hydrocarbon leaves small resist pieces after development. This tendency is particularly noticeable in a fine pattern exposed using an ArF excimer laser. In addition, if the amount of the bridged cyclic hydrocarbon is reduced, the dry etching resistance is inferior and cannot be used. From the above viewpoint, this resist film is not suitable for use as a photoresist film.

Therefore, using an ArF excimer laser,
A photoresist film capable of forming a pattern and having excellent dry etching resistance has not yet been developed, and its development has been eagerly desired.

[0011]

According to the present invention, there is provided a photoresist film according to the present invention, which is exposed to at least an ArF excimer laser and a chemically amplified lower resist film containing at least a benzene ring as a component. And an upper resist film that generates an acid.

Further, the photoresist film of the present invention according to the present invention is characterized in that the lower resist film has a polyvinyl phenol resin in which a hydroxyl group is protected by the protecting group released by the acid. The photoresist film according to claim 1, wherein

According to a third aspect of the present invention, there is provided a resist pattern forming method using a photoresist film according to the first or second aspect, wherein at least a benzene ring is formed on the substrate. Is formed in a lower layer, and a resist that generates an acid by exposing at least to an ArF excimer laser is formed in an upper layer, and then is exposed to an ArF excimer laser to generate an acid. Or while
After generating the acid, the acid is amplified and diffused in a chemical amplification type resist below in a direction normal to the substrate, and then developed.

Further, in the method of forming a resist pattern according to the present invention, the acid is diffused in a normal direction to the substrate, and then a heat treatment is performed to promote amplification and diffusion of the acid. 4. The method according to claim 3, wherein a developing process is performed thereafter.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

FIG. 1 is a diagram showing a pattern forming process using a resist according to an embodiment of the present invention. Also, in FIG.
Reference numeral 1 denotes a silicon oxide film to be etched, 2 denotes a lower resist film, 3 denotes an upper resist film, 4 denotes a mask, 5a denotes an acid generation region, 5b denotes an acid diffusion amplification region, 6 denotes a wafer, and 7 denotes an electric field.

The photoresist film of the present invention has a chemically amplified resist containing at least a benzene ring as a component element on a substrate on which a film to be etched is formed, and is at least exposed to an ArF excimer laser. In a two-layer structure having an acid-generating resist as an upper layer. Here, when a resist containing no benzene ring is used for the lower layer, the dry etching resistance is poor, which is not preferable. In the present invention,
If a chemically amplified resist is not used for the lower layer, the acid generated in the upper resist film by ArF excimer laser irradiation cannot be diffused and amplified in the lower resist film, which is not preferable.

It is preferable that the lower layer of the chemically amplified resist of the present invention contains a polyvinylphenol resin in which at least a hydroxyl group is protected. Incidentally, a chemically amplified resist containing a polyvinyl phenol resin in which a hydroxyl group is protected is widely used as a resist for a KrF excimer laser. Further, it is preferable that the protecting group for protecting the hydroxyl group can be removed by an acid. As the protecting group satisfying these requirements, for example, a t-butoxycarbonyl group (tB
OC), an isopropoxycarbonyl group (i-PrO
C), tetrahydropyranyl group (THP), trimethylsilyl (TMS), t-butoxycarbonyl methyl group _{(t-BOC-CH 2)} , alkoxyalkyl group, haloalkoxy group, and an aralkyl oxyalkyl group.

Further, since the lower resist film of the present invention does not require transparency to an ArF excimer laser, a photo proton generator is not particularly required. If necessary, a novolak-type resist may be contained in order to further improve dry etch resistance.

The thickness of the lower resist film of the present invention is as follows:
Although not particularly limited, it is appropriately set from the viewpoint of dry etching resistance and diffusion amplification of the acid generated in the upper resist film into the lower resist film. That is, when the film thickness is large, the dry etching resistance is excellent, but the acid needs to be diffused and amplified over a long distance. On the other hand, when the film thickness is small,
The acid easily diffuses and amplifies, but has poor dry etching resistance. Therefore, the thickness of the lower resist film of the present invention is preferably in the range of 0.1 to 2.0 μm.

The upper resist film of the present invention is a resist that generates an acid by exposing it to at least an ArF excimer laser. Specifically, a ternary combination of methacrylic acid, tert-butyl methacrylate and methyl methacrylate is used. Polymer resist, tertiary copolymer resist of methacrylic acid, tert-butyl methacrylate and adamantyl methacrylate, quaternary copolymer resist of methacrylic acid, tert-butyl methacrylate, methyl methacrylate and isobornyl methacrylate, methacrylic acid, tert- Examples include a quaternary copolymer resist of butyl methacrylate, methyl methacrylate and adamantyl methacrylate.

That is, in the photoresist film of the present invention, exposure to the ArF excimer laser is performed by the upper resist film, and dry etching resistance is performed by the lower resist film. When a resist in which an acid is generated by exposing to an excimer laser is not formed in the upper layer, A
A pattern using an rF excimer laser cannot be formed.

Further, in order to generate an acid by exposing to an ArF excimer laser, it is necessary to contain a photoproton generator. However, since the content of the photo-proton generator is usually less than 10% of the whole, a component containing a benzene ring may be used as long as a certain degree of transparency is maintained. However, since the photoproton generator is a low molecular weight organic substance and is easily discharged out of the system during dry etching, even if it contains a benzene ring, it does not affect dry etching resistance.

Examples of the photoproton generator having a benzene ring include various diazonium salts, diallyliodonium salts, triallylsulfonium salts and the like. Examples of the photoproton generator not containing a benzene ring include ALS (alkyl sulfonium salt; cyclohexylmethyl (2-oxocyclohexyl) sulfonium trifluoromethane sulfonate, al
Kylsulfonium salt; cyclohex
ylmethyl (2-oxo-cyclohexy
l) sulfonium trifluorometh
anesulfonate), NEALS (β-oxocyclohexylmethyl (2-norbornyl) sulfonium trifluoromethylsulfonate, β-oxo-
cyclohexylmethyl (2-norbor
nyl) sulfonium trifluorome
thanesulfonate) and the like.

The thickness of the upper resist film of the present invention is not particularly limited, but it is necessary that the upper resist film has a thickness necessary to generate an acid sufficient to diffuse and amplify the acid in the lower resist film. On the other hand, if the thickness is too large, the resolution of the pattern may be degraded, and even if the thickness is too large, it hardly contributes to the dry etching resistance, which is not practical. Therefore, the thickness of the upper resist film of the present invention is preferably
It is in the range of 0.01 to 0.5 μm.

The solvent for the upper resist film and the lower resist film of the present invention may be any of those commonly used for photoresists. Specifically, ethyl lactate (EL),
Examples thereof include propylene glycol monomethyl ether acetate (PGMEA), ethyl-3-ethoxypropyl acetate (EEP), and methyl amyl ketone (MAK).

In the method of forming a photoresist pattern according to the present invention, a chemically amplified resist containing at least a benzene ring as a component element is formed in a lower layer on a substrate, and the resist is exposed to at least an ArF excimer laser to form an acid. Is formed on the upper layer, and then Ar
It is characterized in that it is exposed to light by an F excimer laser, generates an acid, diffuses and amplifies the acid in a direction normal to the substrate into a lower chemically amplified resist, and then develops. Further, it is more desirable that after the acid is diffused and amplified in the normal direction to the substrate, a heat treatment is performed and then a development treatment is performed. When diffusion amplification is not performed in the normal direction to the substrate in the present invention, for example, when diffusion amplification is performed in the same direction, it is difficult to form a fine pattern of the upper resist film. As a method of diffusing and amplifying the substrate in the normal direction, specifically, the substrate is exposed to an ArF excimer laser, and while generating an acid or after generating an acid, an electric field is applied to the substrate in a normal direction. , And the acid is preferably diffused and amplified in the normal direction.

Further, after the acid generated by irradiating the ArF excimer laser is diffused and amplified in a direction normal to the substrate and toward the upper resist film, a heat treatment is performed to increase the solubility of the acid in the developing solution due to the amplification of the acid. Can control.

The method of forming the upper resist film and the lower resist film of the present invention can be formed by spin coating, as is employed in a usual photolithography process. In addition, it is desirable to carry out a heat treatment for making the substrate lipophilic, removing the solvent after coating, and curing the resist, if necessary.

Next, in an ArF excimer laser generator, an ArF excimer laser is irradiated. The irradiation amount is appropriately determined depending on the desired pattern shape depending on the sensitivity of the upper resist film and the desired pattern shape. In order to effectively diffuse and generate the generated acid into the lower resist film,
Simultaneously with the ArF excimer laser irradiation, the acid may be diffused in the normal direction into the lower resist film formed on the base,
Alternatively, the acid may be diffused into the lower resist film after the irradiation.

An acid is applied to the substrate in a direction normal to the substrate,
Controls the direction of acid diffusion. The electric field uses a DC electric field,
An AC electric field with a constant bias may be used, or a pulsed electric field may be used. It is also preferable that the strength of the electric field is appropriately determined depending on the average moving distance of the acid, the concentration of the acid, the composition of the resist, and the like.

However, it is desirable not to raise the temperature, since the acid diffuses in the normal direction. Specifically, 0-70 ° C
Is desirable. If it is too high, the acid tends to diffuse isotropically, which is disadvantageous for forming a fine pattern. When left during and after exposure, it is desirable to remove ammonia and moisture in the outside air as much as possible in order to prevent acid deactivation. As a method for removing ammonia, a chemical filter is used to remove ammonia. Alternatively, a method of applying a strongly acidic aqueous solution or a paraffin-based solvent before or immediately after exposure to prevent deactivation of the acid may be used.

Next, a heat treatment is performed. This heat treatment is usually performed using PEB (Post Exposure Bak).
e) In the case where the acid is insufficient only by exposure or diffusion in the normal direction of the substrate by the electric field in the present invention, the acid is amplified, in other words, the acid is further amplified and the developing solution This is performed for the purpose of improving the solubility of the resist in the resist. The heating temperature and the processing time are appropriately determined depending on the concentration of the acid, the composition of the resist, and the like. Then it is developed. The development is performed by a usual development method. Specifically, for example, it is performed by immersing a 2.38% aqueous solution of TMAH (developer) on the resist surface, and then drying the developer.

Hereinafter, a first embodiment of the present invention will be described with reference to FIG.

First, a 6-inch silicon wafer 6 on the surface of which a silicon oxide film 1 was formed by thermal oxidation of about 1 μm was washed with a dilute hydrofluoric acid solution and then dried at a high temperature. Next, the surface was made lipophilic with hexamethyldisilane (HMDS). Next, a positive type chemically amplified resist (UV5, manufactured by Shipley Fur East Co., Ltd.) containing butoxycarboxylic acid ester of polyvinylphenol as a main component is applied by a spin coating method, and prebaked at 130 ° C. for 90 seconds to form a lower resist. Film 2 was formed. At this time, the film thickness after application was about 0.8 μm.

Then, using the same spin coater, a terpolymer copolymer resist of methacrylic acid, tert-butyl methacrylate and methyl methacrylate and a ternary copolymer resist of methacrylic acid, tert-butyl methacrylate and adamantyl methacrylate were used. : 1 mixed resist (triphenylsulfonium hexafluoroantimonate as photoproton generator 2%, ALS 1
%, A 1: 1 mixture of EL and PGMEA as a solvent)
Coating is performed by a spin coating method, and pre-baking is performed again at 90 ° C. for 90 seconds to form an upper resist film 3. The thickness of the upper resist film 3 after the application was about 0.1 μm.

Next, using a mask 4 on which a predetermined pattern is formed and an ArF excimer laser exposure apparatus (prototype machine, manufactured by Nikon Corporation), the mask size is set to 0.18.
Excimer laser irradiation was performed so that a μm L / S pattern could be formed (FIG. 1A). At this time, an acid generating region 5a is formed in a portion of the upper resist film 3 irradiated with the ArF excimer laser.

Next, at a temperature of 25 ° C., a DC electric field of 1000 V / mm is applied from the surface (resist formation surface) of the silicon oxide film 1 to be etched to the back surface of the wafer 6 for 3 minutes or 500 V / mm. The electric field obtained by applying an AC having an amplitude of 200 V and a frequency of 60 HZ to a DC bias is 5
A voltage was applied in one of three types of electric field patterns for one minute or a pulse electric field of 500 V / mm for ten minutes (FIG. 1B). In addition, when applying an electric field, in order to prevent the generated acid from being deactivated, the treatment was performed in an apparatus equipped with a chemical filter. By this step, an acid diffusion amplification region 5b is formed.

Next, PEB treatment was performed at 105 ° C. for 90 seconds. After cooling, the resist was immediately immersed in a developing solution (NMD-3, manufactured by Tokyo Ohka Kogyo Co., Ltd.) to wash out the soluble portion of the resist (FIG. 1 (c)). ). Next, the bake treatment is again performed (90 ° C at 110 ° C).
For 2 seconds) to completely evaporate the developer adhering to the wafer.

Then, etching treatment was performed for 2 minutes using an oxide film etching apparatus (inductively coupled plasma etching apparatus, manufactured by Applied Materials Japan Co., Ltd.) (FIG. 1D). Then, the cross section of the wafer was observed with an electron microscope. As a result, when a DC electric field is applied,
When an electric field to which a DC bias + AC was applied was applied and when a pulsed electric field was applied, the upper resist film almost disappeared, but the lower resist film remained.
The L / S pattern was also well formed.

Hereinafter, comparative examples will be described.

First, as Comparative Example 1, only the resist used as the lower resist film 2 in the above-described embodiment was applied, and an ArF excimer laser was irradiated.
/ Mm DC voltage applied for 3 minutes, PEB
(Heating) treatment, development treatment and dry etching treatment were performed, and the cross section was observed. As a result, although the resist remained, the L / S pattern was not formed.

Next, as Comparative Example 2, only the resist used as the upper resist film 3 in the above-described embodiment was applied, and an ArF excimer laser was irradiated.
/ Mm DC voltage applied for 3 minutes, PEB
(Heating) treatment, development treatment and dry etching treatment were performed, and the cross section was observed. As a result, the resist did not remain, and the part originally covered with the resist was also etched.

Next, as Comparative Example 3, a resist film comprising the same upper resist film 3 and lower resist film 2 as in the above-described embodiment was formed, and irradiated with ArF excimer laser. (Heating) treatment, development treatment and dry etching treatment were performed, and the cross section was observed. As a result, although better than Comparative Example 1, the formation of the L / S pattern was insufficient and etching was not sufficiently performed.

Next, a second embodiment of the present invention will be described.

First, an oxide film of 1000 °, a TiN film of 100 °, an Al film of 5000 °,
A substrate was prepared by sequentially laminating a TiN film having a thickness of 00 °, and heated to completely remove organic substances on the surface. Next, the surface was made lipophilic with hexamethyldisilane (HMDS). Next, the number of revolutions of a chemically amplified resist (K2G, manufactured by Nippon Synthetic Rubber Industry Co., Ltd.) was appropriately adjusted to form a lower resist film 2 of various thicknesses shown in Table 2. The heating after the application was performed at 135 ° C. for 90 seconds.

Then, using the same spin coater, a quaternary copolymer resist of methacrylic acid, tert-butyl methacrylate and methyl methacrylate and adamantyl methacrylate (2% of triphenylsulfonium hexafluoroantimonate as a photoproton generator,
The upper resist films of various thicknesses shown in Table 2 were formed by adjusting the number of rotations of 1% of ALS and 1: 1 mixture of EL and PGMEA as a solvent. The heating after the application was performed at 90 ° C. for 90 seconds.

Next, the same ArF excimer laser exposure apparatus as used in the first embodiment, which is improved so that an electric field can be applied, is used, and the mask size is set to 0.1.
For sample Nos. 1 to 3 in Table 1, a pulsed electric field of 400 V / mm was applied for 5 minutes at a temperature of 40 ° C. while irradiating an excimer laser so that a 7 μm L / S pattern could be formed.
In samples Nos. 4 to 6 in Table 1, a DC electric field of 2000 Vmm was applied at a temperature of 15 ° C. for 5 minutes.

Then, the resist was immediately immersed in a developing solution (NMD-W, manufactured by Tokyo Ohka Kogyo Co., Ltd.) to wash out the soluble portion of the resist. Next, baking treatment was performed again (at 110 ° C. for 90 seconds) to completely evaporate the developing solution attached to the wafer.

Then, etching was performed for 90 seconds using a metal etching apparatus (helicon wave plasma etching apparatus, manufactured by Tricon Technology Co., Ltd.).
Then, the cross section of the wafer was observed with an electron microscope. Table 1 shows the results.

[0051]

[Table 1]

[0052]

As described in detail above, by using the present invention, a photoresist film and a method of forming a photoresist pattern which can form a pattern using an ArF excimer laser and have excellent dry etching resistance. Can be provided.

Further, by performing a heat treatment after applying the electric field, the amplification of the acid can be further promoted and the solubility of the resist in the developing solution can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pattern forming process using a resist according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon oxide film 2 Lower resist film 3 Upper resist film 4 Mask 5a Acid generation area 5b Acid diffusion amplification area 6 Wafer 7 Electric field

Claims (4)

[Claims] 1. A chemically amplified lower resist film containing at least a benzene ring as a component, and at least Ar
A photoresist film comprising: an upper resist film that is exposed to an F excimer laser and generates an acid. 2. The photoresist film according to claim 1, wherein the lower resist film has a polyvinyl phenol resin in which a hydroxyl group is protected by the protecting group released by the acid. 3. A method for forming a resist pattern using a photoresist film according to claim 1, wherein a chemically amplified resist containing at least a benzene ring as a component element is formed in a lower layer on the substrate, ArF
A resist that generates an acid by being exposed to an excimer laser is formed in an upper layer, and then exposed to an ArF excimer laser to generate an acid or after generating an acid, and then apply the acid to a substrate. A method for forming a resist pattern, comprising amplifying and diffusing in a lower layer a chemically amplified resist in a normal direction, and then developing. 4. The method according to claim 3, wherein after the acid is diffused in a direction normal to the substrate, a heat treatment is carried out to promote amplification and diffusion of the acid, followed by a development treatment. A method for forming a resist pattern.