JP2901044B2 - Pattern formation method by three-layer resist method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device and the like, and more particularly to a method of forming a pattern by a three-layer resist method used for forming active elements and wiring patterns.

[0002]

2. Description of the Related Art In order to achieve high integration and high speed of a semiconductor integrated circuit (IC), miniaturization of wiring and multi-layering are being promoted in manufacturing ICs. However, in order to prevent an increase in wiring resistance due to miniaturization, the aspect ratio of the wiring tends to be high, and since such wiring is multilayered, a step on a substrate to be processed is further increased. Therefore, when a resist pattern is formed on a substrate having such a step using, for example, a reduction projection exposure apparatus, the step exceeds the range of the depth of focus of the exposure apparatus. There is a possibility that a desired pattern cannot be formed by the patterning method using the resist. In particular, in the sub-micron region, this problem becomes more remarkable because a reduction projection exposure apparatus equipped with a lens having a large numerical aperture tends to be used and the depth of focus becomes increasingly shallow.

Therefore, as a technique for solving this, for example, Reference I, “Journal of Vacuum Science Technology (Journal of Vacuum Science)”
Science Technology), 16th edition.
Vol. 6, No. 16, pp. 1620-1624, November / December, 1979 ".

In this three-layer resist method, for example, when a wiring pattern is formed from a metal layer formed on a substrate to be processed having a step, the following procedure is taken.

First, a thermosetting resin (thickness: 1.5 to 3 μm) is applied on a metal layer on a substrate to be processed. Next, it is thermally cured to form a lower layer. The lower layer flattens the step of the substrate to be processed. Next, on this lower layer, as an intermediate layer, a thin layer (0.1 μm thick) of SiO ₂ having a high resistance to etching by oxygen plasma was applied to a thickness of 200 μm.
It is formed by a sputtering method by heating at ℃. Next, a photosensitive resin layer as an upper layer is formed on the intermediate layer, and this is exposed and developed to obtain a pattern of the photosensitive resin layer. Next, using this pattern as a mask, the intermediate layer is patterned by reactive ion etching using CHF ₃ gas. Thereafter, using the pattern of the intermediate layer as a mask, the lower layer is etched by reactive ion etching (O ₂ -RIE) using oxygen gas. As a result, a three-layer resist pattern having a high aspect ratio can be obtained. Then, using this as a mask, the underlying metal layer on the substrate to be processed is etched to form a desired wiring pattern.

An advantage of the three-layer resist method is that a photosensitive resin layer pattern is formed on a thick flattening layer (lower layer), so that the patterning of the photosensitive resin layer is affected by steps on the substrate. Therefore, a fine pattern having a high aspect ratio can be formed without dimensional fluctuation.

As the intermediate layer, for example, a commercially available OCD (manufactured by Tokyo Ohka Kogyo Co., Ltd.)
_A coating solution for forming a _two -layer coating may also be used. In the method described in Document I, a sputtering apparatus is required to form an intermediate layer, and the process is complicated.
Is very simple because a film can be formed by spin coating.

[0008]

However, when a film is formed by using the above-mentioned OCD, a high temperature of 450 ° C. (recommended temperature described in a catalog) is required, which has an influence on a base. In addition, there is a problem that cracks easily occur in the film during film formation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. Accordingly, an object of the present invention is to provide an intermediate layer which can be formed by a spin coating method and can reduce the influence of heat on an underlayer. An object of the present invention is to provide a pattern forming method by a layer resist method.

[0010]

In order to achieve the above object, according to the pattern forming method by the three-layer resist method of the present invention, a predetermined poly (siloxane) derivative described below is used as an intermediate layer forming material. A composition containing an acid generator that generates an acid upon exposure is used. Forming a layer of the above-described composition on the lower layer, exposing the layer of the composition, and forming an upper layer on the layer of the exposed composition. And The constituent materials of the lower layer and the upper layer are not particularly limited.

The predetermined poly (siloxane) referred to in the present invention
The derivative may be obtained by using a polymer represented by the formula (1), a polymer represented by the formula (2), or a copolymer of the polymer represented by the formula (1) and the polymer represented by the formula (2) One or more selected from the group consisting of: However, in the formulas (1) and (2), R ¹ , R ² , R ³ and R
⁴ represents an alkyl group, which may be the same or different. Here, the terminal of the poly (siloxane) derivative is not particularly limited. It can be hydrogen or a suitable protecting group such as a trimethylsilyl (TMS) group.
In the formulas (1) and (2), m and n represent positive integers.

[0012]

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Further, the weight average molecular weight of the above-mentioned poly (siloxane) derivative is in the range of 500 to 100,000. If the weight average molecular weight is less than 500, the film (Si
This is because it is not practical because the formation time of O ₂ ) is long and it is not practical. If the weight average molecular weight is more than 100,000, it is difficult to synthesize it with good control of the molecular weight.

Some of such poly (siloxane) derivatives are described in Japanese Patent Application No.
Compound No. 17588. Also, a method for synthesizing a part of such a poly (siloxane derivative) is disclosed in Japanese Patent Application No. Hei.
No. 0889.

On the other hand, the following acid generators can be used. For example, the following (3)
Each onium salt represented by the formula (4), specifically (3)
A sulfonium salt represented by the formula, an iodonium salt represented by the formula (4), a p-toluenesulfonate represented by the following formula (5), a trichloromethyl-substituted triazine represented by the following formula (6), and a following (7) It is a trichloromethyl-substituted benzene represented by the formula. These are preferred because they generate stronger acids than hydrochloric acid.

[0016]

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[0017]

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The above-mentioned acid generators are commercially available or are available, for example, from JV Cribero (JV Cri).
[Journal of Polymer Science, Polymer Chemistry Edition (J. Polymer Sci., Polymer C)
hem. Ed. ) 18,2677 (1980)]
And the method by T. Endo [Journal of Polymer Science, Polymer
Chemistry Edition 23.359 (198
5)].

These acid generators may be used in an amount of 0.01 to 50 parts by weight based on the weight of the poly (siloxane) derivative or resin used.
It is added in an amount in the range of wt%, preferably in the range of 0.05 to 30 wt%. If it is less than this range, a high temperature is required for film formation, and if it is more than this range, the intermediate layer becomes brittle.

Further, in carrying out the present invention, it is preferable to perform a heat treatment on the exposed intermediate layer. In the present invention, the intermediate layer may be made inorganic by exposure alone, but when heat treatment is performed after exposure, the action of the acid generated by exposure is efficiently generated. The heating temperature should be between 40 and
The temperature is in the range of 400 ° C, preferably in the range of 60 to 250 ° C. When the temperature is lower than 40 ° C., the reaction by heating does not proceed.
This is because an acid generator system which reacts at a low temperature of not more than ℃ has poor storage stability. On the other hand, if the temperature is as high as 400 ° C. or more, there is a possibility that the influence is exerted on the underlying substrate. However, a heating temperature of about 150 ° C. at the highest is sufficient. The heating means is not particularly limited. Examples of the heating means include an oven and a hot plate.

[0021]

According to the constitution of the present invention, the coating liquid of the intermediate layer forming material can be prepared by dissolving the poly (siloxane) derivative having an alkoxy group and the acid generator in a solvent. Examples of usable solvents include, for example, monochlorobenzene and 2-chlorobenzene.
Various substances such as ethyl methoxyacetate, xylene, dioxane, methyl isobutyl ketone, and isoamyl acetate can be given. This coating solution can be applied to the lower layer by, for example, a spin coating method, whereby a layer of a composition containing a poly (siloxane) derivative having an alkoxy group and an acid generator can be formed on the lower layer.

Next, a layer of this composition is exposed,
Acid is generated from the acid generator in the composition. Since this acid releases the alkoxy group of the poly (siloxane) derivative, silanol is generated in the poly (siloxane) derivative. Silanol is easily condensed and more easily condensed by applying appropriate heat to the exposed sample, so that the intermediate layer forming material becomes SiO ₂ and an intermediate layer having excellent O ₂ -RIE resistance is obtained. Here, by making the acid generator in the intermediate layer forming material appropriate, it is possible to cope with various exposure light sources.

Next, an appropriate resist is spin-coated on the intermediate layer, and the resist is exposed by an appropriate radiation source and further developed to obtain an upper layer pattern. Using this upper layer pattern, for example, CHF ₃ −
The intermediate layer is etched by RIE to form a pattern of the intermediate layer. Thereafter, using the pattern of the intermediate layer as a mask, the lower layer is etched by O ₂ -RIE, for example, to obtain a three-layer resist pattern having a high aspect ratio.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pattern forming method by a three-layer resist method according to the present invention will be described below. The materials used, the amounts thereof, the processing time, the temperature, and other numerical conditions described in the following description are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited only to these conditions.

1. O ₂ -RIE resistance test of intermediate layer forming material 1-1. Poly (di -t- butoxy siloxane) / triphenylsulfonium triflate (Ph ₃ S ⁺ OT
f ^-) weight in average molecular weight below 20000 (poly represented by 8) (di -t- butoxy siloxane) (Formula (1), R
¹ and R ² are t-butyl (Bu) groups and the terminal is hydrogen. ) 190 g (1 mol), and triphenylsulfonium triflate (Ph ₃ S ⁺ OTf ⁻ ) represented by the following formula (9) as an acid generator ^: 8.25
g (0.02 mol) with monochlorobenzene 178
0 g, which is filtered through a 0.2 μm pore membrane filter to prepare a coating solution for the intermediate layer forming material.

[0026]

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[0027]

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A photoresist (using MP2400 (trade name) manufactured by Shipley Co., Ltd.) is spin-coated on a silicon substrate, and is cured by heating at 200 ° C. for 1 hour in an oven. Form a layer. The above prepared coating solution was spin-coated on this to form a film having a thickness of 0.2 μm.
Then, the entire surface of this layer is exposed to a Xe-Hg lamp for 5 minutes. In this case, the exposure amount corresponds to about 4 J / cm ² . Since this dose is about 40 times the exposure required for converting the layer of the intermediate layer forming material into SiO ₂ , such exposure is not actually required. The exposed sample is heated on a hot plate at 100 ° C. for 2 minutes. Since the heat treatment is performed after the exposure, the layer of the intermediate layer forming material becomes a SiO ₂ film more efficiently. It should be noted that whether or not the layer of the intermediate layer forming material was an SiO ₂ film was confirmed separately from the experiment of this section by directly forming the layer of the intermediate layer forming material on a silicon substrate and subjecting this layer to heat treatment. The analysis was performed by the front and rear IR spectra. next,
The treated substrate was treated with O ₂ − using a DEM451 parallel plate dry etcher (manufactured by Nidec Anelva).
Perform RIE for 20 minutes. The etching conditions are oxygen (O
₂ ) Gas pressure 1.0 Pa, O ₂ gas flow rate 20 SCCM, R
The F power density was 0.12 W / cm ² .

The amount of film reduction of the etched SiO ₂ film (obtained from the layer of the intermediate layer forming material) was measured using a film thickness meter (Talystep, manufactured by Taylor Hobson).
No film loss was observed. Also, no cracks occurred.

1-2. Poly (di -t- butoxy siloxane) / bis (4-t- butylphenyl) hexafluoroantimonate ((4-t-BuPh) 2 I + Sb
F ₆ ⁻ ) In the constitution of the item 1-1, as the acid generator, the following (10)
Bis (4-t-BuPh) ₂ I ⁺ SbF ₆ represented by the formula
^And the heating temperature of the layer of the intermediate layer forming material after exposure to 10
The experiment is performed under the same conditions as those described in section 1-1 except that the temperature is set to 0 ° C.

[0031]

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In this example, no film loss or cracking due to O ₂ -RIE was observed.

1-3. Poly (di-t-butoxysiloxane) / benzoin tosylate In the constitution of the item 1-1, as an acid generator, the following (11)
Except that the benzoin tosylate represented by the formula was used and the heating temperature after exposure of the layer of the intermediate layer forming material was 120 ° C.
The experiment is performed under the same conditions as those described in the section -1.

[0034]

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In this example, no film loss and cracks due to O ₂ -RIE were observed.

1-4. Poly (di-methoxysiloxane)
/ Triphenylsulfonium triflate (Ph ₃ S ⁺
OTf ⁻ ) In the constitution of the item 1-1, a poly (siloxane) derivative represented by the following formula (12) and having a weight average molecular weight of 20,000
00 poly (di-methoxysiloxane) (in formula (1)
R ¹ and R ² are methyl groups and the terminal is hydrogen. ), And the experiment was performed under the same conditions as described in section 1-1, except that the heating temperature of the layer of the intermediate layer forming material after exposure was set to 150 ° C.

[0037]

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In this example, no film loss and cracking due to O ₂ -RIE was observed.

1-5. Poly (t-butoxysilsesquioxane) / triphenylsulfonium triflate In the constitution of the item 1-1, a poly (siloxane) derivative represented by the following formula (13) and having a weight average molecular weight of 20,000
Poly (t-butoxysilsesquioxane) of formula (2) (wherein R ³ and R ⁴ are t-Bu groups, and
Those whose terminals are TMS groups. ) Except that the heating temperature after exposure of the layer of the intermediate layer forming material was set to 150 ° C.
The experiment is performed under the same conditions as described in the section.

[0040]

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In this example, no film loss or cracking due to O ₂ -RIE was observed.

2. Pattern creation by three-layer resist method FIGS. 1A to 1C and FIGS. 2A to 2C
3A to 3C are process diagrams for explaining an embodiment of the method for forming a three-layer resist pattern of the present invention. Each drawing is a cross-sectional view of a main part. Each drawing used in the description merely schematically shows the size, shape, and arrangement relationship of each component so that the present invention can be understood.

As shown in FIG. 1A, as shown in FIG.
i) On the substrate 11, in this case a photoresist, MP2
400 (manufactured by Shipley Co., Ltd.) is spin-coated, and then the sample is heated and cured in an oven at 200 ° C. for 1 hour to form a lower resist layer 13 having a thickness of 2.0 μm.

Next, as shown in FIG. 1B, the coating solution prepared in the section of Example 1-1 was rotated on the lower resist layer 13 so that the film thickness became 0.2 μm. After coating, the entire surface of the film is exposed to light from a Xe-Hg lamp for 5 minutes. Next, by heating the exposed sample on a hot plate at 100 ° C. for 2 minutes,
An SiO ₂ film (intermediate layer) 15 is formed.

Next, as shown in FIG. 1C, an upper resist layer 17 made of SAL601-ER7 (trade name, manufactured by Shipley Co., Ltd.) having a thickness of 0.4 μm is formed on the intermediate layer 15. It is formed so that

Next, the upper resist layer 17 is selectively exposed to an electron beam. The exposure amount at that time is 3 μC / c
and m ^2. After the electron beam exposure, 115
Perform a post-exposure bake for 1 minute at a temperature of ° C. Thereafter, this was immersed in a 0.27 TMAH (tetramethylammonium hydroxide) solution for 5 minutes, further immersed in water for 5 minutes, and baked on a hot plate at 60 ° C. for 1 minute. Thus, an upper layer pattern 17a was obtained (FIG. 2A).

Next, to the upper layer pattern 17a as a mask, using a dry etcher DEM451 (manufactured by Nichiden Anelva), R by CHF ₃ gas to the intermediate layer 15
Perform IE. Thus, an intermediate layer pattern 15a is formed (FIG. 2B). The etching conditions were CHF ₃
Gas pressure is 10 Pa, CHF ₃ gas flow rate is 50 SCCM,
CF ₄ gas flow rate 50 SCCM, RF power density 10
The etching is performed at 0 W / cm ² for 5 minutes. Subsequently, O ₂ -RIE is performed on the lower layer 13 for 35 minutes. Thereby, the lower layer pattern 13a is formed (FIG. 2C). The etching conditions were O ₂ gas pressure of 1.0
The Pa and O ₂ gas flow rates were 20 SCCM, and the RF power density was 0.12 W / cm ² .

As a result of observing the cross section of the thus obtained resist pattern (laminated portion of 13a, 15a and 17a) by a scanning electron microscope (SEM),
It was found that the line-and-space pattern (L / S) of μm had an aspect ratio of 4 and was formed in a rectangular shape.

Although the embodiment of the pattern forming method by the three-layer resist method of the present invention has been described above, the present invention is not limited to the above embodiment.

For example, in the above-described embodiment, poly (siloxane) derivatives include poly (di-t-butoxysiloxane), poly (dimethoxysiloxane) and poly (t-methoxysiloxane).
-Butoxysilsesquioxane) and bis (4-t-butylphenyl) hexafluoroantimonate, benzoin tosylate, and triphenylsulfonium triflate as acid generators, but these are merely examples. Absent. The poly (siloxane) derivative may be any other suitable one such as the one represented by the above formula (1) or (2), and the acid generator may be represented by the above formulas (3) to (7). The same effects as those of the embodiment can be obtained also in the case of another suitable device such as the one.

The technical idea disclosed in the present invention is not limited to a pattern forming method by a three-layer resist method (a method of using a layer of an intermediate layer forming material as an intermediate layer), but selectively using the intermediate layer forming material. Exposure to Si
Since an O ₂ film pattern can be obtained, it can be expected to be developed as a method of forming a SiO ₂ film pattern.

[0052]

As is clear from the above description, according to the pattern forming method by the three-layer resist method of the present invention, a poly (siloxane) derivative having an alkoxy group and an acid generator which generates an acid upon exposure Is used as the intermediate layer forming material, so that a layer of this composition can be formed on the lower layer by spin coating (spin coating). Further, since the layer of this composition is exposed, an SiO ₂ layer as an intermediate layer is obtained. Therefore, O ₂ -RI
An intermediate layer having high E resistance can be easily formed.

When the heat treatment is supplementarily performed after the exposure, the intermediate layer forming material can be efficiently converted into SiO _2. The heat treatment temperature at that time is the same as that of the above-mentioned OCD (conventional SiO ₂ -based film forming material). In this case, the influence of heat on the base can be reduced because the temperature can be lower than the case (at most, 150 ° C. at the temperature of the embodiment).

[Brief description of the drawings]

1 (A) to 1 (C) are process diagrams for explaining an embodiment of a pattern forming method by a three-layer resist method of the present invention.

FIGS. 2A to 2C are process diagrams following FIG. 1 for explaining an embodiment of a pattern forming method by a three-layer resist method of the present invention.

[Explanation of symbols]

11: Si substrate 13: Lower resist layer 13a: Lower layer pattern 15: Intermediate layer (SiO ₂ film) 15a: Intermediate layer pattern 17: Upper resist layer 17a: Upper layer pattern

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI G03F 7/38 G03F 7/38 H01L 21/027 H01L 21/30 573 (58) Fields surveyed (Int.Cl. ⁶ , DB name) ) G03F 7 / 26,7 / 004,7 / 028 G03F 7 / 075,7 / 11

Claims (1)

(57) [Claims] 1. A polymer represented by the formula (1), a polymer represented by the formula (2), and a polymer represented by the formula (1):
And one or more poly (siloxane) derivatives selected from the group consisting of a copolymer of a polymer represented by the formula (1) and a polymer represented by the formula (2), wherein the weight average molecular weight is 50:
The poly (siloxane) derivative in the range of 0 to 100,000 and 0.0 with respect to the weight of the poly (siloxane) derivative
Using a composition containing an acid generator that generates an acid upon exposure and contained in the range of 1 to 50%, and forming a layer of the composition on a lower layer; A pattern forming method using a three-layer resist method, comprising a step of exposing and a step of forming an upper layer on the layer of the exposed composition (wherein formulas (1) and (2) , R ¹ , R
² , R ³ and R ⁴ represent an alkyl group, which may be the same or different, and m and n each represent a positive integer. ). Embedded image