JPH09320930A - Pattern forming method and pattern forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pattern having high resolution and an excellent form, by heat-treating a semiconductor wafer wherein a chemical amplification type positive resist film is formed and exposure is performed, in an atmosphere to which gas containing water content equivalent to air at a specific temperature and humidity is supplied. SOLUTION: Chemical amplification type resist is made to drip on a film to be worked of a semiconductor wafer 1, and it is rotated at a number of revolution suitable for obtaining a desired film thickness. Thereby a resist coating film is formed. In order to vaporize and dry organic thinner in the resist coating film, the semiconductor wafer 1 is put on a hot plate and heat- treated. Thereby a resist film 3 having a desired thickness is formed. By a demagnification projection aligner using an excimer laser, a resist film 3 is exposed to light via a mask, and then PEB treatment is performed on a hot plate 5. The PEB treatment is performed in an atmosphere wherein air at a temperature of 23 deg.C and a humidity of 45-55% is sent to the resist film 3 surface at a given flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method and a pattern forming apparatus for forming a pattern on a semiconductor wafer in manufacturing a semiconductor integrated circuit.

[0002]

2. Description of the Related Art In the manufacture of semiconductor integrated circuits, a method of forming a fine pattern on a film to be processed on a semiconductor wafer and etching the film to be processed using this pattern as a mask is employed. In this pattern forming step, the following operations are usually performed. That is, first, a solution containing a resin and a photosensitizer is applied onto a film to be processed such as a semiconductor thin film and dried to form a resist film (photosensitive resin film). Then, the resist film is subjected to an exposure process of selectively irradiating energy such as light. After that, a mask pattern (resist pattern) is formed on the semiconductor wafer by a developing process.

By the way, the degree of integration of a semiconductor integrated circuit is 2 to
Although 3 is highly integrated at a speed of 4 times, the dimension of the pattern of the circuit element is becoming finer year by year, and thus strict dimensional accuracy is required. Conventionally, as the exposure wavelength for irradiating the photosensitive resin film,
Line (435 nm) and i-line (365 nm) ultraviolet light has been used. A positive resist composed of a novolac resin and a naphthoquinonediazide compound has been used as the resist.

However, with the miniaturization of patterns, expectations are growing for chemically amplified resists that utilize the catalytic reaction of acid with the exposure light of excimer light (248 nm) of krypton or fluorine. This chemically amplified positive resist material comprises a resin in which a functional group soluble in an alkali developing solution such as a hydroxyl group or a carboxylic acid is replaced with a certain compound (protecting group), and an acid generator (PAG: photo acid generator). It is configured.

When this resist is exposed, an acid is generated from PAG, and this acid diffuses in the resist and acts as a catalyst for the decomposition of the protective group and the alkali-soluble functional group of the resin, and the protective group is removed from the resin. As a result of the progress of the elimination reaction, the region in which the decomposition of the protective group has progressed becomes soluble in the developing solution and forms a pattern.

[0006]

As described above, in the chemically amplified resist, the acid generated by exposure diffuses in the resist matrix and participates in the elimination of the protective group. The decomposition reaction rate is governed by a heat treatment after exposure called post exposure bake (PEB). Therefore, strict control of PEB is extremely important for pattern formation and dimensional control thereof. Furthermore, when the amount of water required for the above-mentioned acid diffusion and decomposition reaction of the protecting group is not appropriate, the decomposition reaction of the protecting group does not proceed properly, resulting in unresolved patterns and poor shape.

However, the existing bake oven currently used for PEB processing is performed only by placing a semiconductor wafer on a hot plate having a high temperature uniformity, and the surface of the semiconductor wafer during PEB processing. Environment is not considered, the environment is not necessarily suitable for the above-mentioned acid diffusion and decomposition reaction, and there is a problem that the resolution is insufficient and defective shape occurs. It was In such a baking oven for PEB processing, the performance of the original resist material cannot be fully exerted, and even if the exposure wavelength is shortened due to miniaturization, only a resolution of about 0.30 μm can be obtained. Was the reality.

The present invention has been made to solve the above-mentioned problems, and a pattern forming method and a pattern forming method capable of obtaining a pattern having a high resolution and a good shape by adjusting an environment in a baking oven appropriately. The purpose is to provide a device.

[0009]

According to the pattern forming method of the present invention, an exposed semiconductor wafer is heated at a temperature of 23.degree.
This includes a step of performing heat treatment in an atmosphere in which a gas containing moisture equivalent to air having a humidity of 45 to 55% is supplied. Further, subsequent to the above step, the semiconductor wafer is heat-treated in an atmosphere with less water than this step.

Further, in the pattern forming apparatus according to the present invention, the gap between the semiconductor wafer to be heated and the ceiling of the chamber is within 1 cm. Further, a plurality of pipes for supplying gas into the chamber are provided so that the humidity of the supplied gas can be switched.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. 1 and 2 are cross-sectional views of a semiconductor wafer 1 showing the steps of the pattern forming method according to the first embodiment of the present invention, and the step of FIG. 2 is performed after the step of FIG. In the figure, 1a is a substrate, 2 is a substrate 1
A film to be processed formed on a, 3 is a chemically amplified positive resist film (hereinafter referred to as resist film) formed on the film to be processed 4, 4 is a mask on which a pattern is drawn, 5 is a hot bake oven The plate, 6 is a cooling plate.

First, a film 2 to be processed is formed on a substrate 1a as shown in FIG. 1A, and a resist film 3 is further formed thereon as shown in FIG. 1B. Here, TD made by Tokyo Ohka Kogyo
UR-P series resist was used, but WK made by Wako Pure Chemical Industries
You may use R-PT series. 4-5 cc of such a resist is dropped on the processed film 2 of the semiconductor wafer 1,
The semiconductor wafer 1 is rotated at a rotation speed suitable for obtaining a desired film thickness to form a resist coating film, and the organic thinner in the resist coating film is evaporated to dryness. The resist coating film is heat-treated by placing it on a substrate (not shown) to form a resist film 3 having a film thickness of 7600 angstroms.

The chemically amplified resist used in the present invention is constituted by dissolving at least an acid generator and a resin in an organic thinner, and more specifically, it is decomposed by receiving energy such as electron beam or ultraviolet ray to decompose the acid. The acid-generating agent that generates a carboxylic acid, a hydroxyl group of a resin such as polyphenyl or acrylic acid, or a functional group exhibiting originally-soluble characteristics such as carboxylic acid in a developing solution, is replaced with a protecting group such as an alkyl group. Resins insolubilized in, and organic thinners such as propylene glycol monomethyl ether acetate, 2-heptanone, and ethyl lactate are used. Further, as a resist effective in the present invention, a resin soluble in a developing solution such as polyvinylphenol or acrylic acid shown in Chemical formula 1 (a) or (b) is used.
A resist in which at least a part of the resin substituted with an acetal group or a ketal group shown in (c) and (d) is used in the form of a mixture or a copolymer is preferable. In the formula, R and R ′ do not have to be the same m.

[0014]

Embedded image

After the resist film 3 shown in FIG. 1B is formed, a reduction projection exposure apparatus (not shown) using a wavelength of 248 nm of an excimer laser using a mixed gas of krypton and fluorine is used to form the resist film 3 shown in FIG. As shown in c), the resist film 3 is exposed through the mask 4. The amount of energy at this time was 28 mJ / cm ² . Figure 3a
Is an exposed portion, and 3b is an unexposed portion.

After that, as shown in FIG.
PEB treatment at 115 ° C. for 90 seconds is performed on the hot plate 5 set to ° C. PEB is performed in an atmosphere in which air having a temperature of 23 ° C. and a humidity (relative humidity) of 45 to 55% is blown onto the surface of the resist film 3 at a flow rate of 5 Nl / min. After this PEB process is completed, as shown in FIG. 2B, the semiconductor wafer 1 is cooled for 60 seconds on the cooling plate 6 set at 23 ° C. Further, a 2.38 wt% tetramethylammonium aqueous solution is used as a developing solution, and the resist film 3 is used for 60 seconds.
Form a paddle on top and develop. Thus, FIG.
As shown in (c), the exposed portion of the resist film is dissolved and removed to form a resist pattern 7.

Explaining the mechanism of presenting the resist pattern 7, the acid generated in the resist film 3 by irradiation with laser light or the like functions as an acid catalyst, and the bond between the resin and the protective group is hydrolyzed by the heat during PEB treatment. The functional group soluble in the developing solution of the resin itself is exposed by decomposing, so that the exposed portion 3a is exposed.
Is removed in a state of being soluble in the developing solution, and the resist pattern 7 is formed.

Compared with the case of the prior art in which PEB treatment was performed with air in a clean room without adjusting the humidity,
In this embodiment, the resolution is improved. For example, 0.03
The fine line-and-space pattern that can be separated at the exposure dose optimized by the μm line-and-space (line size: space size = 1: 1) is 0.24 μm line-and-space when the conventional technique is used. On the other hand, in the present embodiment, the line and space is improved to 0.20 μm in part, particularly in the part other than the central part of the wafer surface.

In addition, an improvement in the in-plane dimension uniformity of the resist dimension of the semiconductor wafer was observed. For example, the variation (difference between the minimum dimension and the maximum dimension) when measuring the line dimension of 0.30 μm line and space at 30 points on an 8-inch semiconductor wafer is 0.036 μm in the case of the conventional technique, while In this embodiment, it is improved to 0.018 μm.

Although different from the above resist, a resist using a tertiary butyloxycarbonyl group-containing polyvinylphenol resin which is widely used as a chemically amplified positive resist, such as the APEX series manufactured by Shipley Co., Ltd., is used. When the steps were carried out, this type of resist had a poor dependency on the PEB processing temperature, so the degree was smaller than the above improvement, but the in-plane dimensional uniformity of the semiconductor wafer was improved compared to the conventional case. In the same method of measuring the dimensional variation as described in paragraph 0019, 0.032 μm was used in the case of the conventional technique, while 0.032 μm was used.
It was improved to μm.

Although it is outside the scope of the present invention, for example, SNR-200 manufactured by Shipley Co. or TDUR-N90 manufactured by Tokyo Ohka Kogyo Co., Ltd.
When a process similar to that of the present embodiment is performed using a chemically amplified negative resist such as No. 8 or the like, the resist pattern causes shape abnormality in the vicinity of the resist surface as shown in FIG. Although 0.26 μm line and space could be resolved by the conventional technique, it deteriorated to 0.30 μm line and space by using the same process as above.

By the way, the water in the gas blown during the PEB treatment contributes to the hydrolysis reaction of the protective group used for the resin substitution using an acid as a catalyst and the diffusion of the acid in the resist film. It is considered that the protecting group eliminated in the presence of an acid catalyst contributes to prevent re-bonding with a functional group (hydroxyl group, carboxylic acid, etc.) which is soluble in an alkaline solution. Therefore, when the set humidity is 40% or less at 23 ° C., the hydrolysis reaction by the acid catalyst in the resist film does not proceed sufficiently, the acid does not diffuse sufficiently in the resist film, or the recombination reaction of the protective group. For example, as shown in Table 1, problems such as no resolution or poor resolution in a fine pattern occur for the reason of promoting the above.

On the contrary, when the humidity is 60% or more, the water functions as a material for promoting the diffusion of the acid in the resist film, so that the diffusion of the acid and the addition of the protective group to the portion which should be originally left as the resist pattern are desired. The decomposition reaction progresses, and the photolithography performance such as resolution is deteriorated, especially the resist pattern is significantly deteriorated. From the above results, the humidity at 23 ° C is 4
Air of 5 to 55% is suitable. The results are shown in Table 1.

[0024]

[Table 1]

In addition, when a resist using a resin as described above is used to expose a pattern having a wide exposed area, a larger amount of acid than the amount of acid required to decompose the protective groups of the resin in that area is generated. Therefore, the reaction product generated by decomposition may be polymerized by this excess acid, and may become insoluble even though the protective group is decomposed and removed, which causes a pattern defect. Even in such a case, if the PEB treatment is performed in an environment in which the humidity is controlled as shown in this embodiment, this polymerization reaction is suppressed, which is also effective for pattern defects.

In the above, the temperature is 23 ° C. and the humidity is 45 to 5
Although 5% air was sent, the temperature may be different from 23 ° C., in which case the humidity value is deviated from the range so as to contain the water equivalent to the above. Further, the gas to be sent may be nitrogen or the like other than air.

Embodiment 2. In the first embodiment, air having a temperature of 23 ° C. and a humidity of 45 to 55% was sent during PEB treatment, but in the second embodiment, the air is sent so as to fit well to the resist film, and FIG. It is sectional drawing of an oven. In the figure, 8 is a chamber provided so as to cover a hot plate 5 on which the semiconductor wafer 1 is placed and heated, and 9 is a pipe for sending gas such as air to the chamber 8. A semiconductor wafer 1 in which a hot plate 5 is sealed in a chamber 8 and a resist film is further formed
The size s of the space between the chamber and the ceiling 8a of the chamber 8 is 1
It is within cm.

From the pipe 9 to the lower part of the periphery of the chamber 8, 3N
Air having a temperature of 23 ° C. and a humidity of 45 to 55% is sent at a flow rate of 1 / min, and a differential pressure of 0.
The same amount of exhaust gas is treated with ₂ mmH ₂ O. As a result, the humidity-controlled air does not stagnate on the semiconductor wafer 1 and uniformly contacts the resist film over the entire surface of the semiconductor wafer 1. With the resist pattern obtained by such a method, the effect obtained in the first embodiment is efficiently exhibited in the entire area of the surface of the semiconductor wafer 1. For example, in the first embodiment, the resolution is 0.
It has been shown that the line width and space up to 20 μm are partially achieved. However, in this embodiment, the entire wafer surface including the central portion of the wafer surface is uniformly exposed to air whose humidity is controlled. The resolution can be improved up to 0.20 μm line and space.

Further, in the first embodiment, it was shown that the resist using the tert-butyloxycarbonyl-based polyvinylphenol resin slightly improved the dimensional uniformity in the wafer surface. When a baking oven is used, the line width of a 0.30 μm line-and-space resist pattern at 30 locations within the semiconductor wafer surface of an 8-inch diameter under the same conditions has a pattern dimension variation of 0.024 μm. It was observed.

The degree of narrowing between the semiconductor wafer 1 and the ceiling 8a of the chamber 8 was loosened, and the size of the gap s was set to 2 cm. I couldn't see it.

Embodiment 3 FIG. 5 is a cross-sectional view of a bake oven showing Embodiment 3 of the present invention. The pipe 9 has two systems of pipes 9a and 9b so that two different kinds of gas can be switched and sent into the chamber 8. Made of. Others are the same as those in the third embodiment. A pattern forming method according to this embodiment will be described. The process up to the exposure step is the same as in the first and second embodiments. PEB
In the treatment, the temperature is 23 ° C and the humidity is 4
While blowing 5 to 55% of air into the chamber 8, the semiconductor wafer 1 is heat-treated at 115 ° C. for 40 seconds, and then the air in the pipe 9a of one system is stopped and the pipe 9 of the other system is stopped.
The heat treatment is performed at 115 ° C. for 40 seconds while blowing air from b to 23 ° C. and 40% humidity into the chamber 8. After that, the semiconductor wafer 1 is cooled by a cooling plate and developed to form a resist pattern.

Such a resist pattern forming method is
This is particularly effective when forming a hole pattern. For example, the depth of focus for a 0.26 μm hole was 1.2 μm according to the prior art, but in this embodiment, 1.
It was improved to 6 μm. Further, the minimum hole opening size at the optimum exposure amount of 0.26 μm is 0.24 μm in the conventional technique.
The number of m holes was 0.20 in this embodiment.
It was a μm hole and the resolution was improved.

Note that, as shown in FIG.
A and 9b may be put together via the valve 10 on the way.
In this case, the gas sent to the chamber 8 can be switched by operating the valve 10. In addition, in the above process, the space between the semiconductor wafer 1 and the ceiling portion 8a of the chamber 8 is 1c.
Although a bake oven having a length of m or less was used, even if a plurality of lines of piping were provided so that two kinds of gas could be switched to be sent to the hot plate 5 in such a space that the gap was not so narrow, This has the effect of improving the pattern resolution.

[0034]

According to the pattern forming method of the present invention, a semiconductor wafer is heat-treated by sending a gas containing moisture equivalent to air having a temperature of 23 ° C. and a humidity of 45 to 55%. Acts properly controlled,
This has the effect of improving the resolution of the resist pattern and improving the shape. Further, the depth of focus and the resolution in hot pattern formation are improved by heat-treating the semiconductor wafer in an atmosphere containing less water than the above heat treatment.

The pattern forming apparatus according to the present invention is
Since the distance between the semiconductor wafer and the ceiling of the chamber is within 1 cm, the gas to be fed and the resist film are well compatible, the resolution of the resist pattern is improved over the entire surface of the wafer, and the in-plane dimensional uniformity of the wafer is improved. Further, since the piping is provided in a plurality of systems, the gas to be sent during the heat treatment can be switched, and the depth of focus and resolution of the hole pattern can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor wafer showing a pattern forming method according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor wafer showing a step that follows FIG. 1 in the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor wafer showing a shape abnormality in a chemically amplified negative resist.

FIG. 4 is a sectional view showing a bake oven according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing a bake oven according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing another oven according to the third embodiment of the present invention.

[Explanation of symbols]

1 semiconductor wafer, 3 resist film, 5 hot plate, 7 resist pattern, 8 chamber, 8a ceiling, 9 pipe, 9a one pipe, 9b another pipe.

Front Page Continuation (72) Inventor Mutsumi Nakamura 4-1, Mizuhara, Itami City, Hyogo Prefecture Ryoden Semiconductor System Engineering Co. Ltd.

Claims (4)

[Claims] 1. A first step of selectively exposing a semiconductor wafer having a chemically amplified positive resist film formed thereon, a second step of heat-treating the exposed semiconductor wafer, and the heat treatment. And a third step of developing the semiconductor wafer.
A pattern forming method, wherein the second step is carried out in an atmosphere in which a gas containing moisture equivalent to air at a temperature of 45 to 55% is supplied. 2. The pattern forming method according to claim 1, wherein, following the second step, the heat treatment of the semiconductor wafer is performed in an atmosphere containing less water than in the second step. 3. A hot plate for mounting and heating a semiconductor wafer, and a chamber for covering the hot plate,
In a pattern forming apparatus provided with a bake oven including a pipe for supplying a humidity-controlled gas into the chamber, a gap between the semiconductor wafer and the ceiling of the chamber is set to be within 1 cm. Pattern forming device. 4. A hot plate for mounting and heating a semiconductor wafer, and a chamber for covering the hot plate,
In a pattern forming apparatus provided with a bake oven including a pipe for supplying a humidity-controlled gas into the chamber, the pipes have a plurality of systems so that the humidity of the gas supplied into the chamber can be switched. A pattern forming apparatus characterized by the above.