JPH07120048B2 - Pattern formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] In the present invention, a positive transfer or anti-transfer pattern is formed on a resist film by silylation or non-silylation utilizing heat treatment and photochemical reaction. The present invention relates to a method for forming a fine pattern on a substrate for a semiconductor or various devices with high accuracy.

[Prior Art] As a method of forming a fine pattern with high accuracy, a multilayer resist method has been conventionally developed. Compared with the case where pattern formation is performed on the resist single layer film, this method can eliminate the adverse effect on the pattern formation characteristics caused by the local fluctuation of the resist film thickness due to the step remaining on the substrate surface. Since the resist film thickness of the uppermost layer forming an image can be made thinner than that of the resist single layer film, there is an advantage that even a fine pattern can be formed with high accuracy. However, on the other hand, there are some serious problems in practical use such as the number of steps is complicated and a special resist material is required. Techniques currently being developed as a multilayer resist method include a three-layer resist method and a two-layer resist method. The three-layer resist method has a problem in that the process is complicated and the number of steps is large because the intermediate layer film formation and the dry etching for processing the intermediate film and the lower layer film are performed twice. On the other hand, the two-layer resist method was developed as a more practical pattern forming method by halving the number of steps of the three-layer resist method. The feature is that the upper layer resist is a silicon-containing resist having oxygen plasma resistance. Is used. However, in general, when silicon is contained as a constituent element of a polymer, basic properties required as a resist such as solubility and sensitivity to a solvent and pattern resolution are affected, and there is still a problem in practical use.

Therefore, a silylated two-layer resist method was developed (Japanese Patent Laid-Open Nos. 60-165041 and 61-116844). The method is
A commercially available resist having excellent characteristics in both sensitivity and resolution is used as it is as an upper layer resist, and silylation treatment is performed after pattern formation to obtain oxygen plasma resistance. Therefore, it is a versatile technique that can be applied not only to light exposure but also to an exposure method such as electron beam or X-ray, and can be used for a normal transfer or anti-transfer process.

FIG. 5 is a process diagram showing an example of pattern formation by a positive transfer process when the conventional silylated two-layer resist method is applied to electron beam exposure. In FIG. 5, reference numeral 3 is a substrate, 6 is a lower layer resist film, 7 is an upper layer resist film,
8 means a silylated layer.

As shown in FIG. 5 (a), a lower layer resist film (eg polyimide cured at a high temperature of 200 ° C. or higher) 6 which is not silylated is applied onto the substrate 3. Next, as the upper resist film 7, a resist for electron beam exposure [eg polymethylmethacrylate (PMMA), RE-5000P (manufactured by Hitachi Chemical Co., Ltd.), chloromethylstyrene (CMS), etc.] is thinly applied. Next, the upper layer resist 7 is exposed and developed using an electron beam exposure apparatus to form a pattern as shown in FIG. 5 (b). After that, when an organosilane such as a halogenated alkylsilane is used for irradiation with far-ultraviolet light, a silylated layer 8 is formed on the surface layer portion of the upper resist 7 as shown in FIG. 5 (c). Finally, by dry etching the entire substrate with oxygen gas, the lower layer resist film 6 is etched using the silylated layer 8 as a mask to form a pattern as shown in FIG. 5 (d).

On the other hand, FIG. 6 shows, as a process diagram, an example of pattern formation by an anti-transfer process when applied to conventional electron beam exposure. Reference numerals 3 and 6 to 8 in FIG. 6 have the same meanings as in FIG.

As shown in FIG. 6 (a), a lower layer resist film 6 capable of being silylated (for example, a novolak resin hard-baked at about 200 ° C.) is applied on the substrate 3. Next, as the upper resist film 7, a resist for electron beam exposure [for example, EBR-9 (manufactured by Toray), PMMA, fluorobutyl methacrylate (FB
M) etc.] is applied thinly. Next, electron beam exposure is performed and development is performed to form a pattern as shown in FIG. 6 (b). After this, silylation treatment is performed in a halogenated alkylsilane atmosphere, but here, by using far-ultraviolet light such that the upper resist film 7 is not silylated and only the lower resist film 6 is silylated. As a result, the silylation can be selectively carried out, and the silylation layer 8 can be formed only on the lower resist film 6 as shown in FIG. 6 (c). Finally, when the entire substrate is dry-etched in oxygen gas, the remaining portion of the unsilylated upper layer film is etched by using the silylated layer 8 as a mask as shown in FIG. Can be formed. As described above, this silylated two-layer resist method is a technique that can easily form a positive transfer or anti-transfer pattern by selecting the wavelength of the far-ultraviolet light source at the time of silylation using a commercially available resist material. is there. By the way, these inventions (Japanese Patent Application No. 60-1)
No. 65041, No. 61-116844), the use of an originally inactive polymer material such as polyimide, polyethylene, polypropylene, or polyvinyl chloride that is not silylated as the lower resist film 6 when forming a positive transfer pattern. .

[Problems to be solved by the invention]

However, when considering application in the current LSI process, polyethylene, polypropylene, polyvinyl chloride, etc. have no actual use record, and polyimide is a material that has recently begun to be used as a semiconductor process, so it is applied to mass production processes. To do so, more thorough examination is required.

For this reason, in order to use the silylated two-layer resist method in a mass production process, it is necessary to study a material with a proven track record. If possible, the same material as that used for the anti-transfer pattern is desired in the process.

The present invention has been made in view of the above circumstances, and an object thereof is to selectively silylate or desilylate a resist film when an organosilane is added to the resist film surface by utilizing a photochemical reaction. Another object of the present invention is to provide a method for forming a pattern of a resist film that enables the above.

[Means for solving problems]

Briefly describing the present invention, the present invention relates to a pattern forming method, in which a patterned resist film is irradiated with far-ultraviolet light on its surface while being in contact with an organic silane solution or vapor thereof. In the method
The surface of the resist film is silylated or non-silylated depending on the heat treatment conditions of the resist film.

In order to solve the above problems, the present invention is premised on using a photoresist, which has a proven track record in mass production of VLSI, as an organic polymer material, and silylates or desilylates the polymer surface depending on the processing conditions. It is characterized by that. Therefore, the same material can be applied in the forward transfer or anti-transfer process as compared with the conventional technique. Regarding the silylation method utilizing the photochemical reaction according to the present invention, the invention already proposed (Japanese Patent Application No. 60-1
65041, 61-116844) is a further development of the principle.

The present invention will be described in detail below.

In the present invention, VLSI is used as the polymer material for the lower resist film.
The silylation reaction states of these were selected from some positive photoresists applicable to or applied for mass production of. Table 1 shows various commercially available resists containing a novolak base polymer.

Samples were prepared by changing the heat treatment temperature and the heat treatment time for typical resists from these resists.

Next, the silylation treatment method of the present invention is shown in FIG. 1 as a schematic diagram. In FIG. 1, reference numeral 1 is a container, 2 is an organic silane liquid, 3 is a substrate, 4 is a resist film, and 5 is a lid. Dimethylchlorosilane [(CH ₃ ) ₂ SiHCl] is in the container 1.
Is filled with the organic silane liquid 2. Further, various resist films 4 having different processing conditions are formed on the substrate 3. Then, the container 1 is covered with a quartz glass 5 and far ultraviolet light is irradiated from the upper surface thereof to silylate the resist film 4.
Next, in order to confirm the silylation reaction state, reactive ion etching is carried out in a parallel plate type sputtering etching device into which oxygen gas is introduced, and the etching amount with respect to the etching time is measured and compared with the non-silylated one. I checked it out. As a result, it was found that there is a large difference in the silylation reaction depending on the treatment conditions of the resist film and the silylation treatment conditions. Various processing conditions are shown below. A hot air circulation oven was used for heat treatment of the resist, and the treatment time was set to 30 minutes and 60 minutes. The processing temperature is 20
There are four types, 0 ° C, 240 ° C, 280 ° C and 300 ° C. For the silylation treatment, far-ultraviolet light from a low-pressure mercury lamp (253.7 nm) was irradiated for 10 minutes and 20 minutes.

Dry etching (oxygen pressure 2 Pa, flow rate 50 sccm, high-frequency output 100 W) was performed on the sample under each of these conditions, and the etching amount at the etching time of 2 minutes and 5 minutes was obtained.
The silylation reaction state was investigated in comparison with that of the non-silylated sample.

As a typical example, FIG. 2 shows the dry etching characteristics of MP-1400 resist as a graph of the relationship between etching time (minutes, horizontal axis) and etching amount (μm, vertical axis). The circle is
Heat treatment at 280 ℃, 60 minutes, triangle mark at 240 ℃, 60 minutes,
The mark X indicates that heat treatment was performed at 200 ° C. for 60 minutes, and then silylation was performed for 10 minutes. The solid line does not silylate
This is the etching amount of the MP-1400 resist. In this case, it did not depend on the heat treatment conditions. From this result, it can be seen that even if the silylation time and the heat treatment time are the same, the etching amount greatly changes depending on the heat treatment temperature.

Table 2 shows the results of summarizing the silylation reaction states of various resists. The circles in the table represent those that were not silylated, the crosses represent those that were silylated, and the triangles indicate that the surface was slightly silylated.

As a result, it was found that at the heat treatment temperature of 240 ° C. or less, all the resist materials were silylated and hardly changed with the treatment time of about 1 hour.

Next, at a heat treatment temperature of 280 ° C. or higher, the silylation reaction was slightly different depending on the resist material. That is, it was found that under the heat treatment condition of 280 ° C. for 30 minutes, the resist surface was slightly silylated when the silylation treatment was carried out for 10 minutes (see FIG. 2 because the etching grade is worse than that of the non-silylated resist). . This was almost the same for the cresol novolak resin (1H-303) and the diazo / novolak photoresists other than Kodak-820. It was also found that all resists except Kodak-820 and 1H-303 were sufficiently silylated when the silylation treatment was carried out for 20 minutes. On the other hand, it was found that when the heat treatment time was 60 minutes, silylation was not performed except when the silylation was performed for 20 minutes with Kodak-809.

When the heat treatment temperature is 300 ° C, the heat treatment time is 3
It was found that the resist was not silylated at 0 minutes.

In this experiment, the hot air circulation type oven was used as the heat treatment device, so the processing time is long.However, if the adsorption type hot plate is used, the heat treatment is performed in a short time including the temperature uniformity of the substrate. Is possible (in the mass-production process, the heat treatment of the resist is performed by the hot plate method).

The silylation reaction of the novolak resin, which is the base polymer of photoresist, is excited and activated by the absorption of far-ultraviolet light, and chlorosilane is bonded to the OH group of the novolak resin by a dehydrochlorination reaction to form a siloxane bond and silylated. .

On the other hand, the results in Table 2 show that when the heat treatment temperature is around 280 ° C, it tends to be unsilylated, and at 300 ° C it is not completely silylated. Considering this factor, it is presumed that the OH group in the benzene nucleus began to undergo thermal decomposition and chlorosilane became difficult to bond. Further, the reason that the silylation reaction is slightly different depending on the resist is presumed to be that there is a slight difference in the base polymer which is a benzene nucleus.

Therefore, as is clear from this experiment, it is possible to selectively silylate by changing the heat treatment conditions of a commercially available photoresist (novolak resin as a base polymer). A normal transfer or anti-transfer pattern can be realized with the material.

〔Example〕

Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

Embodiment 1 FIG. 3 shows a specific embodiment of the positive transfer pattern of the present invention as a process chart. Reference numeral 3 is a substrate, 6 is a lower resist film, 7 is an upper resist film, and 8 is a silylated layer.

In order to carry out the method of this embodiment, first, as shown in FIG. 3A, an MP-1400 photoresist having a thickness of about 1.5 μm is applied on the substrate 3 to form a lower resist film 6. Then 300
After heat treatment at ℃ for 30 minutes, apply an electron beam resist of RE-5000P with a thickness of about 0.3μm on it, and at 90 ℃ for 10 minutes.
The upper resist film 7 is formed by performing heat treatment for a minute. After that, a desired pattern is printed on the upper resist film 7 with an electron beam exposure apparatus, and further development processing is performed to form the pattern of the upper resist film 7. In this case, the lower layer resist film 6 is applied sufficiently thick to reduce the influence of the step of the substrate 3, and the upper layer resist film 7 is applied thinly so that a fine pattern of about 0.2 μm can be formed with good reproducibility. . Then, dimethylchlorosilane [(C
H ₃ ) ₂ SiHCl] solution was used to perform silylation treatment by irradiation with a low-pressure mercury lamp having a wavelength of 253.7 nm for about 10 minutes. Since the lower resist film 6 is heat-treated at 300 ° C., the lower resist film 6 is not silylated and only the upper resist film 7 has a silylated layer 8 as shown in FIG. 3B. After that, the substrate 3 is transferred to a reactive ion etching device, and high frequency output 10
Etching (no residue) until the underlying substrate 3 is fully visible under the conditions of 0 W, oxygen pressure 2 Pa, and flow rate 50 sccm.
Then, a pattern is formed as shown in FIG.

If pattern processing is performed by the method as described above, it is possible to use all lithographic methods such as excimer, X-ray, and plasma as well as ultraviolet rays and far ultraviolet rays other than the resist for electron beam as the upper resist film 7. There is.

Embodiment 2 FIG. 4 shows a specific embodiment of the anti-transfer pattern of the present invention as a process drawing. In FIG. 4, reference numeral 3 is a substrate, 6 is a lower layer resist, 7'is an upper layer resist, and 8 is a silylated layer.

To carry out the method of this embodiment, first, as shown in FIG. 4 (a), an MP-1400 photoresist having a thickness of about 1.5 μm is applied on the substrate 3 to form a lower resist film 6. Next, heat treatment is performed at a temperature of about 200 ° C. for 30 minutes.

Next, EBR-9 for electron beam is used as the upper resist film 7 '.
It is applied to a thickness of about 0.3 μm and heat-treated at 190 ° C for 30 minutes. After that, exposure is performed with an electron beam and development is performed to form a pattern. Next, chlorotriethylsilane [(C ₂ H ₅ )
With ₃ SiCl], Yotsute the low-pressure mercury lamp having 253.7nm
After 10 minutes of silylation treatment, the methacrylate polymer, which is the base polymer of EBR-9, has a photosensitizing wavelength of 250n.
Since it is less than m, it is not exposed to light and therefore is not silylated. On the other hand, since the lower resist film 6 is heat-treated at about 200 ° C., it is sufficiently silylated, and the silylated layer 8 is formed on the exposed portion of the lower film as shown in FIG. 4B. . After that, if reactive ion etching is performed in the same manner as in the first embodiment, an anti-transfer pattern opposite to that in the first embodiment can be formed as shown in FIG. 4 (c).

〔The invention's effect〕

As described above, in the photochemical reaction of an organic silane monomer, the present invention silylates or desilylates the resist film surface by changing the heat treatment conditions of the patterned resist film. Therefore,
A normal transfer pattern or an anti-transfer pattern can be easily formed using the same type of resist film. Further, this resist film does not have any bad influence on the process because it can be used for the mass production process.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the silylation treatment method of the present invention, and FIG.
FIG. 4 is a graph showing a dry etching characteristic, FIG. 3 is a process chart of forming a normal transfer pattern according to the present invention, FIG. 4 is a process chart of forming an anti-transfer pattern according to the present invention, and FIG. 5 is a conventional normal transfer pattern. FIG. 6 is a process chart of forming a conventional anti-transfer pattern. 1: Container, 2: Organic silane liquid, 3: Substrate, 4: Resist film, 5:
Lid, 6: lower resist film, 7, 7 ': upper resist film, 8: silylated layer

Claims (1)

[Claims] 1. A pattern forming method comprising irradiating the surface of a patterned resist film with far-ultraviolet light while being in contact with an organic silane solution or vapor thereof, depending on the heat treatment conditions of the resist film. A pattern forming method characterized by silylating or non-silylating the surface of a film.