JPH07333850A - Photosensitive composition - Google Patents

Abstract

PURPOSE:To obtain a photosensitive compsn. transmitting ArF excimer laser light and excellent in dry etching resistance. CONSTITUTION:This photosensitive compsn. is based on PVA and contains a thioctate and a sulfonium salt. This compsn. transmits ArF excimer laser light and functions as a negative type resist whose exposed part is made soluble. The thioctate is a sulfur-contg. compd. In dry etching with a pattern formed using this photosensitive compsn. as a mask, a protective film consisting of sulfur and sulfur compds. formed by the decomposition of the thioctate is formed on the exposed face of the pattern and the side wall.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photosensitive composition,
In particular, it relates to a photosensitive composition used for lithography.

[0002]

2. Description of the Related Art In the manufacturing process of semiconductor devices, miniaturization of element structures has been achieved by the progress of fine processing technology. In order to further miniaturize the device structure in the future, it is essential to shorten the exposure light used in the lithography. Then, a resist pattern is formed by lithography using the exposure light whose wavelength has been shortened, and in order to perform fine processing of a semiconductor device using this resist pattern as a mask, it has transparency to exposure light of a short wavelength. Moreover, development of a photosensitive composition having excellent dry etching resistance is required.

As the photosensitive composition, there is a chemically amplified resist based on polyvinylphenol. Polyvinylphenol has higher transparency and is soluble in an alkali developing solution, as compared with the novolac resin used as a resist material. Further, since it contains a benzene ring, it has excellent dry etching resistance.

[0004]

However, in the above-mentioned photosensitive composition based on polyvinylphenol, the benzene ring in the photosensitive composition exhibits strong absorption for wavelengths in the far ultraviolet region. And, in particular, argon fluorine (hereinafter referred to as ArF) excimer laser light (wavelength 193n
For m), the photosensitive composition has a low transmittance. Therefore, the above-mentioned photosensitive composition cannot be applied to lithography using ArF excimer laser light as exposure light.

Therefore, the present invention aims to provide a photosensitive composition which is transparent to ArF excimer laser light and has excellent dry etching resistance, thereby promoting miniaturization of semiconductor devices. To do.

[0006]

The first photosensitive composition of the present invention for achieving the above object comprises polyvinyl alcohol or a derivative of polyvinyl alcohol, a compound salt containing sulfur, and an onium salt. .

The second photosensitive composition comprises a polymethacrylate derivative, a sulfur-containing compound, and a photoacid generator.

[0008]

Function: In FIG. 1, polyvinyl alcohol (hereinafter, PV
The chart of the infrared spectroscopic analysis of a system in which an onium salt is added to (A) is shown. As shown here, in the above system, Ar
It is confirmed that the hydroxyl groups of PVA are reduced by irradiating the F excimer laser light. The first photosensitive composition is one in which PVA or its derivative contains an onium salt, and as described above, when the hydroxyl group of PVA or its derivative decreases by exposure with ArF excimer laser light,
The exposed area becomes insoluble in water. Further, PVA and its derivative have transparency with respect to the ArF excimer laser light. Therefore, Ar irradiated on the first photosensitive composition is
The F excimer laser light is difficult to be absorbed by the first photosensitive composition. Therefore, the first photosensitive composition is A
It is fully exposed by rF excimer laser light. Since the first photosensitive composition contains a sulfur-containing compound salt, the exposed area is in a state in which the sulfur-containing compound salt is wrapped in PVA or a derivative thereof. For this reason, the above-mentioned first formed by the development after the exposure.
When dry etching is performed by masking the pattern made of the photosensitive composition of, the compound salt containing sulfur in the pattern is decomposed and the sulfur and the sulfur compound adhere to the exposed surface of the pattern and the etching side wall to protect it. A film is formed.

Next, since the second photosensitive composition contains a photo-acid generator, an acid is generated by irradiation with light. By the generation of the acid, the acid-eliminating protective group of the methacrylate compound is eliminated to generate a carboxylic acid, and the exposed portion of the methacrylate compound becomes soluble. Further, the methacrylate compound has transparency to the ArF excimer laser light. Therefore, the ArF excimer laser light applied to the second photosensitive composition is
Difficult to be absorbed by the photosensitive composition of. Therefore, the second
The photosensitive composition (1) is sufficiently exposed by ArF excimer laser light. Since the second photosensitive composition contains a compound containing sulfur, dry etching is performed using the pattern of the second photosensitive composition formed by development after exposure as a mask. In this case, the sulfur-containing compound in the pattern is decomposed, and the sulfur and the sulfur compound adhere to the exposed surface and the etching sidewall of the pattern to form a protective film.

[0010]

EXAMPLES The photosensitive composition of Example 1 of the present invention and dry etching using the same will be described below. The photosensitive composition of the first embodiment comprises polyvinyl alcohol or a derivative of polyvinyl alcohol, a compound salt containing sulfur,
It is composed of an onium salt.

The above polyvinyl alcohol (hereinafter, PVA
And the PVA derivative are the bases of the photosensitive composition. The PVA derivative is obtained by substituting the hydroxyl group of PVA shown in Chemical formula 1 (1) with another substituent. Here, when the PVA derivative is used in the photosensitive composition, one having a substitution rate of the hydroxyl group of 40% or less is used so that the PVA derivative is soluble in water and mixed with the compound salt containing sulfur. . Further, in order to ensure the transparency of the photosensitive composition to the argon fluorine (hereinafter, referred to as ArF) excimer laser light, the substituent preferably has no π → π * transition. Such P
As an example of the VA derivative, there is a vinyl acetal compound shown in Chemical formula 1 (2).

[Chemical 1]

As the compound salt containing sulfur, for example, a salt having no π → π * transition is used. Examples of such a compound salt containing sulfur include thioctoate shown in Chemical formula 2 (1), 1,3 dithiolane dicarboxylic acid salt shown in Chemical formula 2 (2), and 1,3 shown in Chemical formula 2 (3). Examples include dithiane dicarboxylic acid salt.

[Chemical 2]

As the onium salt, for example, a salt containing sulfur is used. Examples of such an onium salt include a sulfonium salt shown in Chemical formula 3 (1) or a derivative thereof, an iodonium salt containing sulfur shown in Chemical formula 2 (2), a derivative shown in Chemical formula 2 (3), and the like.

[Chemical 3]

An example of the method for synthesizing the above-mentioned photosensitive composition is shown below. Here, among the compounds shown above,
Chemical formula 1 (1) PVA, and chemical formula 2 (1) thioctoate,
The case of synthesizing a photosensitive composition composed of the sulfonium salt of Chemical formula 3 (1) will be described. First, the PVA 1.1
2 g and 14.2 g of tetramethylammonium thioctic acid as a thioctoate are added to 10.04 g of water and stirred. Further, 0.17 g of the sulfonium salt is dissolved in 3.0 g of dimethylacetamide. The above mixture is then combined and stirred, which is filtered through a 0.2 μm membrane filter. This gives 1 sulfur
The photosensitive composition introduced at a rate of about 2.5 ωt% is synthesized.

When the above photosensitive composition is patterned by lithography, it is carried out as follows. First,
The photosensitive composition dissolved in a solvent as described above is spin-coated on a wafer made of, for example, silicon. Then, for the photosensitive composition on the wafer, a wavelength of 1
Pattern exposure is performed using ArF excimer laser of 93 nm as exposure light. After the above, post exposure bake (PEB) is performed at 110 ° C. for 90 seconds, and then development processing is performed using water as a developing solution.

FIG. 1 shows an IR chart of a system in which an onium salt is added to PVA. As shown here, in the above-mentioned system, by irradiation with ArF excimer laser light, P
The hydroxyl groups of VA decrease, and the exposed area becomes insoluble in water. Therefore, this photosensitive composition functions as a negative resist. Since the photosensitive composition is based on PVA, it has transparency to the ArF excimer laser light. Therefore, in the above exposure, the exposed portion is sufficiently exposed. Therefore, a pattern made of the photosensitive composition is formed in the exposed area by the development processing.
In addition, the photosensitive composition contains a thioctoate. For this reason, as shown in FIG.
The thioctoate 2 is enclosed in A1.
Therefore, when dry etching is performed using this pattern as a mask, the thioctoate in the pattern is decomposed, and sulfur and sulfur compounds adhere to the exposed surface of the pattern and the etching side wall to form a protective film. At that time, since sulfur is introduced into the photosensitive composition at an introduction rate of about 12.5 ωt%, a sufficient amount of sulfur for protecting the sidewall of the pattern is attached to the sidewall of the pattern by etching. . Therefore, dry etching of the wafer is sufficiently performed using the pattern of the photosensitive composition as a mask. Further, in the dry etching, since the protective film is formed also on the etching side wall, it is possible to perform the dry etching in which the dimensional conversion difference between the pattern and the etching pattern formed by the dry etching is suppressed to be small.

The synthesis example of the photosensitive composition shown in the first embodiment is not limited to the above, and the photosensitive composition functions as a negative resist and serves as a protective film during dry etching. It suffices that the photosensitive composition is synthesized in such a ratio that sulfur and sulfur compounds are sufficiently supplied.

Next, the photosensitive composition of the second embodiment and dry etching using the same will be described. The photosensitive composition of the second example comprises a polymethacrylate compound, a sulfur-containing compound, and a photoacid generator.

The polymethacrylate compound is the base of the photosensitive composition. As the polymethacrylate compound, a compound in which an acid-eliminating protecting group is bent is used so that a carboxylic acid is produced in the presence of an acid. As the acid-eliminating protecting group, one having no π → π * transition is used. An example of such a compound is each compound shown in Chemical formula 4.

[Chemical 4]

The sulfur-containing compound exhibits good compatibility with the polymethacrylate compound and has a π
→ It is desirable to have no π * transition. Examples of such compounds include thioctic acid shown in Chemical formula 5 (1), 1,3 dithiolane dicarboxylic acid shown in Chemical formula 5 (2), and Chemical formula 5
There is a 1,3 dithiane dicarboxylic acid shown in (3). In addition to these, carbonyloxy-based or ether-based compounds applicable to the above may be used.

[Chemical 5]

The above photo-acid generator effectively generates an acid by irradiation with light. Here, of the compounds generally used as the acid generator, those containing, for example, sulfur are used. As an example,
Sulfonium salt or derivative thereof shown in (1)
(2) Sulfur-containing iodonium salt or compound 6
There are derivatives thereof shown in (3).

[Chemical 6]

An example of the method for synthesizing the above-mentioned photosensitive composition is shown below. Here, among the compounds shown above,
A case of synthesizing a photosensitive composition composed of the polymethylmethacrylate of Chemical formula 4, the thioctic acid of Chemical formula 5 (1), and the sulfonium salt of Chemical formula 6 (1) will be described. First, 1.0 g of the above polymethylmethacrylate was added to cyclohexanone 9
g. Further, 0.5 g of thioctic acid and 0.17 g of sulfonium salt are dissolved in 3.0 g of cyclohexanone. The above mixture is then mixed and stirred,
This is filtered with a 0.2 μm membrane filter. As a result, a photosensitive composition having sulfur introduced at an introduction rate of about 10 ωt% is synthesized.

When the above-mentioned photosensitive composition is patterned by lithography, it is carried out as follows. First,
The photosensitive composition dissolved in a solvent as described above is spin-coated on a wafer made of, for example, silicon. Then, for the photosensitive composition on the wafer, a wavelength of 1
Pattern exposure is performed using ArF excimer laser of 93 nm as exposure light. After that, PEB is performed, and then
The development process is performed using water, warm water, or an alkaline aqueous solution such as tetramethylammonium hydroxide (TMAH).

Since the above-mentioned photosensitive composition contains a photoacid generator composed of a sulfonium salt, an acid is generated by irradiation with light. By the generation of acid, the methyl group is eliminated from polymethylmethacrylate to form a carboxylic acid, and the exposed portion of the photosensitive composition becomes soluble. Therefore,
The photosensitive composition functions as a positive resist. The photosensitive composition is based on polymethylmethacrylate and has a low content of π → π * transition.
Therefore, the photosensitive composition has transparency with respect to the ArF excimer laser light and is sufficiently exposed by the ArF excimer laser light. Therefore, a pattern made of the photosensitive composition is formed in the unexposed portion by the above-mentioned development processing. Then, thioctic acid is contained in the second photosensitive composition. Therefore, when dry etching is performed on the pattern, thioctic acid in the pattern is decomposed and sulfur and sulfur compounds adhere to the sidewalls of the pattern. At that time, since sulfur is introduced into the photosensitive composition at an introduction rate of about 10 ωt%, a sufficient amount of sulfur for protecting the sidewall of the pattern adheres to the sidewall of the pattern by etching. Therefore, dry etching of the wafer using the pattern as a mask is sufficiently performed.

The example of synthesizing the photosensitive composition shown in the second embodiment is not limited to the above, and the photosensitive composition functions as a positive resist and forms a sidewall protective film during dry etching. It suffices that the resin is synthesized in such a ratio that the sulfur and the sulfur compound will be sufficiently supplied.

[0026]

As described above, according to the photosensitive composition of the present invention, the photosensitive composition is composed of polyvinyl alcohol or its derivative, a compound salt containing sulfur and an onium salt, or polymethacrylate. Since the photosensitive composition is composed of the system compound, the sulfur-containing compound, and the photo-acid generator, transparency with respect to the exposure light of ArF excimer laser light is secured, and a pattern is formed by lithography using this as the exposure light. It will be possible. Further, by dry etching using this pattern as a mask, a sidewall protective film made of sulfur and a compound containing sulfur can be formed on the sidewall of the pattern. Therefore, it becomes possible to secure the dry etching resistance of the above pattern. Therefore, miniaturization of the semiconductor device can be promoted.

[Detailed Description of Drawings]

FIG. 1 is an IR chart of a system in which an onium salt is added to polyvinyl alcohol.

FIG. 2 is a diagram showing a state of the photosensitive composition of the first example.

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Claims (2)

[Claims] 1. A photosensitive composition comprising polyvinyl alcohol or a derivative of polyvinyl alcohol, a compound salt containing sulfur, and an onium salt. 2. A photosensitive composition comprising a polymethacrylate compound, a sulfur-containing compound, and a photo-acid generator.