JP2643879B2 - Fine pattern forming 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 photolithography step in a semiconductor manufacturing process, and more particularly to a method for forming a fine pattern by a silylation method.

[0002]

2. Description of the Related Art In recent years, in the field of various electronic devices that require microfabrication such as semiconductor devices, demands for higher density and higher integration of devices have been more and more increased. It is becoming essential to make the pattern finer. And in the semiconductor device manufacturing process,
A photolithography process plays an important role in forming a fine pattern. Furthermore, in the photolithography process, with the miniaturization of semiconductor devices,
There is a demand for a method of transferring a resist pattern onto a substrate with high accuracy, and dry etching using gas plasma or the like is being used instead of conventional wet etching. In particular, as a method of transferring a resist pattern using oxygen plasma, a single-layer silylation method for selectively introducing a silicon compound having high oxygen plasma resistance to a resist surface has been actively studied.

[0003] In the conventional single-layer silylation method, a light-irradiated portion or an unirradiated portion is selectively silylated after pattern exposure, followed by dry development with oxygen plasma and patterning. As a method of selectively silylating an exposed portion, for example, Journal of Vacuum Science and Technology (Journalof)
Vacuum Science & Techno
b) (Ki-Ho) described in B, Vol. 9, No. 6, pp. 3399-3405 (1991).
Baik et al., DESIRE (Diffusion E)
enhancedSilylation Resist)
There is a process. In the DESIRE process, after pattern exposure and baking, the resist is subjected to silylation using a silylating agent (for example, hexamethyldisilazane), followed by dry development with oxygen plasma to form a pattern. . At this time, by the silylation in the exposed part,
The hydroxyl group (-) of the resin (for example, novolak resin)
OH group) and the silylating agent react to form a silyl ether (-
Since OSi (CH ₃ ) ₃ ) is formed, etching resistance to oxygen plasma is improved. On the other hand, in the unexposed portion, a baking treatment after exposure causes a cross-linking reaction between the photosensitive agent (for example, a photosensitive agent containing a naphthoquinonediazide group) and the resin, so that no silylation reaction occurs. as a result,
A difference in the etching rate due to oxygen plasma occurs between the exposed part and the unexposed part, and a negative pattern can be formed. Bake et al. Described above also reported an example in which bis (dimethylamino) methylsilane was used as a silylating agent in this technique.

As a method of selectively silylating unexposed portions, for example, a resist comprising a resin, a photoacid generator, and a crosslinking agent which causes a crosslinking reaction with the resin by the action of an acid is used. JP-A-4-28704
No. 7, there is a method of Fujino et al. In this method, the pattern exposure, baking, silylation, and dry development using oxygen plasma are the same as the above-described method and steps, but in this method, the exposed portion is crosslinked with the resin by the action of the acid generated by the exposure. Since the agent causes a crosslinking reaction,
The silylating agent cannot diffuse into the resist, and the silylation reaction does not occur. On the other hand, in the unexposed area, since such a crosslinking reaction does not occur, it is silylated. As a result, a difference in etching rate occurs between the exposed portion and the unexposed portion, and a positive pattern can be formed.

As another method for selectively silylating unexposed portions, for example, an ArF excimer laser (19
By irradiating high-energy rays such as 3 nm),
By causing a crosslinking reaction of the resin only in the exposed portion and then silylating with dimethylsilyldimethylamine or the like, selectively forming a silylated region only in the unexposed portion, and etching the exposed region with oxygen plasma. Form a positive pattern. An example of using this method is the Japanese Journal of Applied Physics.
Plied Physics) Pt. 1, 31 volumes, N
o. 12B, pp. 4321-4326 (1992), by Donald W. Jo.
hnson) et al.

[0006]

However, the silylating agent used for silylation in the conventional single-layer silylation method, particularly in the single-layer silylation method in which a silylated region is formed in an unexposed area, is hexadecyl. Methyldisilazane, dimethylsilyldimethylamine, tetramethyldisilazane, N, N-dimethylaminotrimethylsilane, 1,1,3,3,5
Only compounds such as 5-hexamethylcyclotrisilazane, which can introduce only one silicon atom into one hydroxyl group of a resin (for example, novolak resin or polyvinylphenol) by silylation. Therefore, the concentration of silicon atoms introduced into the resist is low, and the etching resistance to oxygen plasma is not sufficient. As a result, the shape of the fine pattern is particularly severely degraded after etching by oxygen plasma, and it is difficult to control the dimension of the fine pattern.

Accordingly, in the silylation method of the unexposed portion of the single-layer resist, there is a demand for a method of forming a silylated region at a higher concentration and improving the etching resistance of the silylated layer.

Therefore, a technical problem in this field is to develop a method capable of silylation at a higher concentration. The prior art is inadequate in these respects, and development of a method capable of silylation at a higher concentration is desired.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have solved the above-mentioned problems by a silylation method using bis (dimethylamino) methylsilane (hereinafter abbreviated as B (DMA) MS) as a silylating agent. The present invention has been found.

The method for forming a fine pattern according to the present invention will be described below. The resist is spin-coated on the substrate to be processed, exposed and baked, and then the unexposed portion is silylated using B (DMA) MS as a silylating agent to form a silylated region. Next, a fine pattern is obtained by etching the resist layer with oxygen plasma using the silylated region as a mask.

The silylation method using B (DMA) MS according to the present invention has a higher silicon atom concentration and a higher oxygen plasma resistance than the conventional silylation method using a silylating agent. It was confirmed that the pattern was excellent and the pattern shape after dry development was good. From this, it became clear that the silylation method of the unexposed portion using B (DMA) MS was effective as a silylation method of the resist, and was excellent in fine pattern forming ability.

In the above-mentioned method of forming a silylated region in an exposed area by Ki-Ho Baik et al., An example in which B (DMA) MS is used as a silylating agent is disclosed. Was not seen. The present invention discloses for the first time that an unprecedented effect can be obtained by using B (DMA) MS for silylation of an unexposed portion.

[0013]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

(Example 1) Polyvinylphenol (MW)
= 34000) was dissolved in 80 g of ethyl lactate, and filtered through a 0.2 μm-pore membrane filter to prepare a resist solution. The obtained solution was spin-coated on a silicon substrate, and baked on a hot plate at 100 ° C. for 60 seconds to form a 0.7 μm-thick resist film. B (DMA) MS 10%,
The resist film was immersed in a mixed solution of 87% xylene and 3% N-methylpyrrolidone at room temperature for 120 seconds, and then rinsed with xylene to silylate the resist film. Next, the silylated resist film was removed from Rutherford using a backscattering analyzer AN-2500 (incident ion: ⁴ He ⁺ , incident energy: 2.0 MeV, beam current: 1.0 nA) manufactured by Nissin High Voltage Co., Ltd. Scattering analysis (hereinafter abbreviated as RBS) was performed to measure the Si concentration of the silylated layer. Table 1 shows the results.

(Comparative Example 1) As Comparative Example 1, while the resist film was heated to 100 ° C., the resist film was subjected to RBS by exposing it to dimethylsilyldimethylamine vapor of 10 Torr for 2 minutes. Table 1 shows the results.

(Comparative Example 2) As Comparative Example 2, the resist film was made of bis (dimethylamino) dimethylsilane 10%,
The resist film was immersed in a mixed solution containing 87% of xylene and 3% of N-methylpyrrolidone at room temperature for 120 seconds, and then rinsed with xylene for silylation of the resist film to perform RBS. Table 1 shows the results.

[0017]

[Table 1]

From these results, it has been clarified that the silylation method using B (DMA) MS has a higher Si concentration in the silylated region than the conventional method.

Example 2 An FTIR spectrum of a resist film formed under the same conditions as in Example 1 was measured. Next, the resist film is made of B (DMA) MS 10%, xylene 8
The resist film was immersed in a mixed solution of 7% and 3% N-methylpyrrolidone at room temperature for 120 seconds, and then rinsed with xylene to silylate the entire resist film, and the FTIR spectrum after the silylation was measured. FTIR at that time
The difference spectrum is shown in FIG. From FIG. 1, after silylation, S
The absorption at 1098 cm -1 due to the i-O-Si bond was increased. From these results, it was revealed that in the silylation using B (DMA) MS, a plurality of silicon atoms were introduced into one hydroxyl group of the resin (polyvinyl phenol).

Comparative Example 3 A comparative example was carried out in the same manner as in Example 2, except that the resist film was exposed to dimethylsilyldimethylamine vapor at 10 Torr for 2 minutes while heating at 100 ° C. . As a result, F
In the TIR difference spectrum, there was no absorption derived from the Si—O—Si bond. From this, it became clear that in the silylation using dimethylsilyldimethylsilane, only one silicon atom was introduced into one hydroxyl group of the resin (polyvinyl phenol).

(Embodiment 3) The resist film was entirely silylated under the same conditions as in Embodiment 1. _Then, O 2 -ECR (P
power = 50 W, pressure = 5 mTorr, temperature = −50
C.). As a result, it took 700 seconds to completely etch the resist film. As a comparative example, while heating the resist film to 100 ° C., 10
Exposure to rr dimethylsilyldimethylsilane vapor for 2 minutes also etched the silylated resist film. As a result, the time required to etch the entire resist film was 380 seconds. From this, it became clear that the photosensitive composition of the present invention has excellent resistance to oxygen plasma.

Example 4 Polyvinylphenol (MW)
= 34000) was dissolved in 80 g of ethyl lactate, and filtered through a 0.2 μm-pore membrane filter to prepare a resist solution. The obtained solution was spin-coated on a silicon substrate, and baked on a hot plate at 100 ° C. for 60 seconds to form a 0.7 μm-thick resist film. The film thus formed was exposed using an ArF excimer laser exposure device (NA = 0.55). After exposure, the resist film was converted to B (DMA) MS 10%, xylene 87%,
1% at room temperature in a mixed solution of 3% N-methylpyrrolidone.
The unexposed areas were silylated by immersing for 20 seconds and then rinsing the resist film with xylene. Then O
_2- ECR (Power = 50W, pressure = 5mTorr)
r, temperature = −50 ° C., time = 120 seconds). FIG. 2 shows an SEM photograph of the resist pattern when the exposure amount is 215 mJ / cm ² . As shown in FIG. 2, a rectangular pattern of 0.12 μmL / S was obtained. From these results, it has been clarified that the silylation method using B (DMA) MS has extremely excellent resolution.

[0023]

As described above, B (DMA) MS
Is effective as a method for silylating a resist because the silicon atom concentration in the silylated region is high, the resistance to oxygen plasma is excellent, and the fine pattern forming ability is excellent.

[Brief description of the drawings]

FIG. 1 shows an FTIR difference spectrum of a resist silylated by the silylation method shown in Example 2 of the present invention.

FIG. 2 shows an SEM photograph of a fine pattern formed by the method shown in Example 4 of the present invention.

[Explanation of symbols]

 None

Claims (1)

(57) [Claims] 1. A step of applying at least a resist on a substrate to be processed, a step of exposing after prebaking, a step of silylating an unexposed portion using a silylating agent to form a silylation region, and Etching a resist layer using gas plasma using a region as a mask, wherein bis (dimethylamino) methylsilane is used as a silylating agent.