JPH086253A - Photosensitive composition - Google Patents

Abstract

PURPOSE:To obtain a photosensitive compsn. capable of precisely forming a pattern by lithography using ArF excimer laser beam exposure light. CONSTITUTION:This photosensitive compsn. consists essentially of a base resin obtd. by protecting at least part of the hydroxyl groups of a polyol compd. with protective groups releasable by an acid, photo-acid initiator and a nitroxy radical polymn. inhibitor. In this functional photosensitive compsn. as a positive type chemical amplification type resist, the polymn. of a compd. at the hydroxyl group parts of the base resin is prevented and the solubility of an exposed part, is ensured. Since the nitroxy radical polymn. inhibitor is used, transparency to ArF excimer laser beam is ensured.

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, in order to accurately form a pattern made of a photosensitive composition by lithography using the exposure light having the shortened wavelength, it is necessary to develop a photosensitive composition having transparency to the exposure light having the short wavelength. It has been demanded.

As the above-mentioned photosensitive composition, for example, a chemically amplified photosensitive composition in which a photo-acid generator is added to a base resin in which a hydroxyl group of a polyol compound is protected by an acid-eliminating protecting group is noted. Has been done. In this photosensitive composition, the photoacid generator in the photosensitive composition generates an acid when exposed to exposure light. The acid releases the acid-eliminating protective group from the base resin, and this portion returns to a hydroxyl group. As a result, the exposed portion of the base resin becomes soluble. Therefore, the photosensitive composition functions as a positive resist. In the chemically amplified photosensitive composition as described above, a large number of reactions are caused even if the amount of acid generated by exposure is small. Therefore, it is possible to achieve high sensitivity in pattern formation of the photosensitive composition by lithography. In addition, generally, the addition amount of the photo-acid generator having a structure having high absorptivity for exposure light in the far ultraviolet region can be suppressed to a small amount. Therefore, for example, it is possible to form a photosensitive composition having transparency to exposure light in the far ultraviolet region, such as argon fluorine (hereinafter, referred to as ArF) excimer laser light.

[0004]

However, the above-mentioned photosensitive composition has the following problems. That is, in the photosensitive composition, the reaction of solubilizing the base resin by the irradiation of the exposure light simultaneously with the reaction of polymerizing the compound in the photosensitive composition to the hydroxyl group portion of the base resin. This is confirmed by irradiating a system consisting of polyvinyl alcohol (hereinafter referred to as PVA), which is one of the polyol-based compounds, and a photoacid generator with exposure light to reduce the hydroxyl groups in the PVA. As described above, when the reaction of reducing the hydroxyl groups of the base resin proceeds due to the exposure, the exposed portion of the base resin cannot exhibit sufficient solubility in the developing solution. For this reason,
It is not possible to accurately form a pattern made of the above photosensitive composition.

Therefore, the present invention solves the above problems,
It is an object of the present invention to provide a photosensitive composition capable of accurately forming a pattern by lithography using ArF excimer laser light as exposure light.

[0006]

The photosensitive composition of the present invention for achieving the above object comprises a base resin obtained by protecting at least a part of hydroxyl groups of a polyol compound with an acid-eliminating protecting group. , A photoacid generator and a nitroxy radical-based polymerization inhibitor.

[0007]

The photosensitive composition contains a base resin obtained by protecting at least a part of hydroxyl groups of a polyol compound with an acid-eliminating protecting group and a photoacid generator. The composition functions as a positive chemically amplified resist. Further, since the photosensitive composition contains a polymerization inhibitor, the polymerization reaction is suppressed in the photosensitive composition. Therefore, the compound is prevented from polymerizing on the hydroxyl group portion of the base resin, and the hydroxyl group of the base resin is maintained. Therefore, the photosensitive composition ensures the solubility of the exposed area. Furthermore, since the above-mentioned polymerization inhibitor is a nitroxy radical type, it has transparency to ArF excimer laser light. Therefore, the ArF of the photosensitive composition may be changed by the polymerization inhibitor.
The transparency with respect to the excimer laser light is not impaired.

[0008]

EXAMPLES Hereinafter, the patterning of the photosensitive composition according to the first embodiment of the present invention and the patterning of the photosensitive composition by lithography will be described. The photosensitive composition of the first example comprises a butyral resin, a photoacid generator, and a nitroxy radical-based polymerization inhibitor.

The butyral resin serves as a base resin for the photosensitive composition. This butyral resin is polyvinyl alcohol (hereinafter,
The hydroxyl group of PVA) is protected by a butyral group which is an acid-eliminating protective group. Here, those in which 50 to 80 mol% of the hydroxyl groups are protected by butyral groups are used.

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The above-mentioned photo-acid generator effectively generates an acid upon irradiation with light. Here, for example, the sulfonium salt shown in Chemical formula 2 is used from the compounds generally used as the photoacid generator.

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The above-mentioned nitroxy radical type polymerization inhibitor suppresses the polymerization reaction in the photosensitive composition. Here, 2,2,5,5-tetramethyl-1-pyrrolidinyloxy-3-carboxylic acid shown in Chemical formula 3 is used as the nitroxy radical-based polymerization inhibitor.

[Chemical 3]

An example of a method for synthesizing the above photosensitive composition is shown below. First, 1.0 g of the butyral resin and 0.17 g of a sulfonium salt are dissolved in 12 g of ethyl cellosolve acetate (hereinafter referred to as ECA). And 7.
7 mg of the above polymerization inhibitor is dissolved in 3.3 g of ECA. Here, the polymerization inhibitor is set to about 0.1 to 50 mol% with respect to the photo-acid generator. next,
The above two solutions are mixed, and the mixed solution is filtered with a 0.2 μm membrane filter. As a result, the ECA
A photosensitive composition in a state of being dissolved in is synthesized.

When the photosensitive composition in the above state is patterned by lithography, it is carried out as follows. First, the photosensitive composition dissolved in the solvent as described above is spin-coated on a wafer made of, for example, silicon. Then, the photosensitive composition on the wafer is subjected to pattern exposure using ArF excimer laser light having a wavelength of 193 nm as exposure light. Then 80-90
Post exposure bake (PE for 90 seconds)
B: Posi Exposure Bake) is performed, and then development processing is performed using water as a developing solution. As a result, a pattern made of the photosensitive composition is formed on the wafer.

Since the above-mentioned photosensitive composition contains a photo-acid generator, an acid is generated in a portion irradiated with light.
The butyral resin, which is the base resin of this photosensitive composition, is obtained by protecting the hydroxyl group of PVA with a butyral group that is an acid-eliminating protective group. Therefore, due to the generation of the acid, the butyral group is eliminated from the butyral resin and this portion returns to the hydroxyl group. This makes the exposed areas of the photosensitive composition soluble in the developer. On the other hand, the unexposed portion of the photosensitive composition has a hydroxyl group of 50-80.
Since mol% is protected by a butyral group, it is insoluble in the developer. Therefore, this photosensitive composition functions as a positive resist. Further, since the photosensitive composition contains a polymerization inhibitor, the polymerization reaction can be suppressed in the photosensitive composition. Therefore, in this photosensitive composition, the hydroxyl groups of the butyral resin are prevented from decreasing due to the polymerization reaction, and the solubility of the exposed area is secured. Further, the above-mentioned polymerization inhibitor is a nitroxy radical type and absorbs ArF excimer laser light π →
Does not include π * transition. Therefore, the π → π * transition in the photosensitive composition is an extremely small amount contained in the sulfonium salt used as the photoacid generator. Therefore,
The transparency of the photosensitive composition to ArF excimer laser light is ensured, and the exposure of the photosensitive composition is sufficiently performed with ArF excimer laser light in the above-mentioned lithography. From the above, in the above-mentioned lithography, the pattern made of the above-mentioned photosensitive composition is accurately formed on the unexposed portion on the wafer.

In the above-mentioned first embodiment, the case where a butyral resin is used as a base resin obtained by protecting at least a part of hydroxyl groups of a polyol compound with an acid-eliminating protecting group has been described. However, the above-mentioned other vinyl acetal resin may be used as the base resin, and in this case, the same effect as that of the first embodiment can be obtained.

Next, the patterning of the photosensitive composition of the second embodiment and the photosensitive composition by lithography will be described. The photosensitive composition of the second example comprises a base resin obtained by protecting the hydroxyl group of PVA with an acid-eliminating protective group containing sulfur,
It is composed of a photo-acid generator and a nitroxy radical type polymerization inhibitor.

As the acid-eliminating protective group containing sulfur of the above-mentioned base resin, for example, one having a small absorption of ArF excimer laser light is used. As such an acid-eliminating protective group containing sulfur, there is a thioctocarbonyl group. Here, P
The base resin shown in Chemical formula 4 in which 50 to 80 mol% of the hydroxyl group of VA is protected by this thioctocarbonyl group is used.

[Chemical 4]

As the photoacid generator and the nitroxy radical type polymerization inhibitor, the compounds shown in the first embodiment are used.

An example of a method for synthesizing the above photosensitive composition is shown below. First, the base resin shown in Chemical Formula 4 above is synthesized.
1 g of PVA and 5.2 g of thioctic acid are dissolved in 20 ml of dimethylformamide (DMF). Then, dicyclohexylcarbodiimide (D
CC) is added and refluxed for 5 to 10 hours. Next, the solution is added to a large amount of water, the precipitate is filtered, and the precipitate is dissolved in acetone. Then, the above-mentioned acetone solution is poured into water and reprecipitation is repeated several times, and the purified product is vacuum dried. As a result, a base resin in which a part of the hydroxyl groups of PVA shown in Chemical formula 4 is protected with a thioctocarbonyl group is synthesized. Sulfur is introduced into this base resin at a rate of 23 to 26 wt%.

Next, 100 parts of the base resin and 10 parts of the photo-acid generator are dissolved in propylene glycol methyl ether acetate (PGMEA). The nitroxy radical-based polymerization inhibitor is added to the PG at a ratio of about 0.1 to 50 mol% with respect to the photoacid generator.
Dissolve in MEA solution. Then, the above two solutions are mixed and filtered with a 0.2 μm membrane filter. As a result, the photosensitive composition dissolved in the solvent is synthesized.

When the photosensitive composition in the above state is patterned by lithography, it is carried out in the same manner as in the first embodiment.

The photosensitive composition constituted as described above is
Since the thioctocarbonyl group is eliminated from PVA by the acid generated by the exposure, it functions as a positive resist as in the first embodiment. Further, since the photosensitive composition contains the same polymerization inhibitor as in the first embodiment, the photosensitive composition ensures the solubility in the exposed area. Since the polymerization inhibitor and the thioctocarbonyl group which is the acid-eliminating protecting group do not have a π → π * transition, the exposure of the photosensitive composition with ArF excimer laser light is performed as in the first embodiment. Is fully done. Therefore, in the above-mentioned lithography, a pattern made of the above-mentioned photosensitive composition is accurately formed on the unexposed portion on the wafer as in the first embodiment.

Further, this photosensitive composition uses a compound containing sulfur as an acid-eliminating protecting group. For this reason,
In the dry etching using the pattern of the photosensitive composition as a mask, the acid-eliminating protective group containing sulfur pendant on the side chain of the resin is decomposed and sulfur or a sulfur compound adheres to the exposed surface of the pattern and the etching sidewall. To do. At that time, the resin of the photosensitive composition contains 23 to 26 wt% of sulfur.
Since it is introduced at an introduction rate of about%, a sufficient amount of sulfur to protect the pattern exposed surface and the etching sidewall is attached to form a protective film. Therefore, it is possible to sufficiently perform dry etching using the above pattern as a mask and to form an etching pattern with a small conversion difference with respect to the pattern size.

In the second embodiment, a thioctocarbonyl group was shown as the sulfur-containing acid-eliminating protecting group. But,
As the acid-labile protecting group, 1,3 dithiolane-2-carbonyl group and 1,3 dithian-2-carbonyl group may be used. These carbonyl groups are ethyl 1,3 dithiolane-
Given by 2-carboxylate or ethyl 1,3 dithian-2-carboxylate. In addition, Japanese Patent Application No. 6-1
In the photosensitive composition shown in Example 5963 in which a nitroxy radical-type polymerization inhibitor is added, the same effect as in the above-mentioned second example can be obtained.

In the first and second embodiments, the case where the photoacid generator shown in Chemical formula 2 and the nitroxy radical type polymerization inhibitor shown in Chemical formula 3 are used has been described. However, the photosensitive composition of the present invention is not limited to the above. As the photoacid generator, for example, an onium salt which is widely used as a photoacid generator can be used. In addition to the above, nitroxy radical-based polymerization inhibitors include 2,2,5,5-tetramethyl-1-pyrrolidinyloxy-3-carboxamide, 2,2,5,5-tetramethyl- 3-pyrroline-1-oxyl-
3-carboxylic acid N-hydroxysuccinimide ester,
2,2,5,5-Tetramethyl-3-pyrrolin-1-yloxy-3-
Carboxamide and the like are applicable.

[0026]

As described above, according to the photosensitive composition of the present invention, a base resin obtained by protecting at least a part of hydroxyl groups of a polyol compound with an acid-eliminating protecting group, and a photoacid generator. By composing the photosensitive composition with the nitroxy radical-based polymerization inhibitor, it is possible to prevent the compound in the photosensitive composition from polymerizing with the hydroxyl group of the base resin. Therefore, the solubility of the base resin is ensured in the exposed portion. Further, by using a nitroxy radical-based polymerization inhibitor, it becomes possible to ensure the transparency of the photosensitive composition to ArF excimer laser light. Therefore, it is possible to accurately form a pattern made of the photosensitive composition by lithography using ArF excimer laser light as exposure light.

Claims (1)

[Claims] 1. A base resin obtained by protecting at least a part of hydroxyl groups of a polyol compound with an acid-eliminating protective group, a photo-acid generator and a nitroxy radical-type polymerization inhibitor. A photosensitive composition to be used.