JPH07117750B2 - Photosensitive resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photosensitive resin composition, and more particularly to a photosensitive resin composition suitable for lithography using a KrF excimer laser (249 nm). The composition is used for forming a fine pattern necessary for manufacturing semiconductor devices and the like.

[Conventional technology]

As a pattern forming method for manufacturing an LSI, a reduced projection exposure method using light of g-line (436 nm) or i-line (365 nm) has been conventionally used. However, with lithographic technology using these UV rays, the resolution limit is theoretically 0.8 μm, which corresponds to the minimum line width of 4 Mb DRAM.
Expected to be the maximum line width required for manufacturing 16Mb DRAM 0.5μm
Is believed to be difficult to achieve using conventional lithographic techniques. Therefore, new resist materials, process technology, or hardware for resolving 0.5 μm have been actively researched in recent years. Recently, a reduced projection exposure technology using KrF excimer laser (249 nm) light has been proposed.
It is attracting attention as a powerful lithographic technique for resolving line widths of μm or less. This technology attempts to increase the resolution by using light with a shorter wavelength than UV light, but the shorter the wavelength of the light used, the more
If it is less than 300 nm, a serious problem occurs in the resist material.
For example, the novolak-based resist (composition of novolak resin and naphthoquinone diazide sulfonate) that has been put into practical use for a long time has a poor light transmittance at 249 nm because it contains an aromatic ring in the base polymer and the photosensitizer. Light does not reach the bottom of the resist. Further, the bleaching action of the photosensitizer which brings about high resolution does not occur. Therefore, a good pattern cannot be obtained by KrF excimer laser irradiation with these resists. On the other hand, in order to improve the light transmittance of the resist at 249 nm, PM containing no aromatic ring is used.
MA-based resists have been evaluated as excimer laser resists, but although these resists have good patterns, they have poor sensitivity and their resistance to reactive ion etching (RIE) due to the absence of aromatic rings. Is inferior.

Thus, up to now, no resist material having excellent sensitivity, resolution and RIE resistance has been found as a KrF excimer laser resist, and development of a new resist material has been desired. In addition, as a literature on the evaluation of a commercial resist by a KrF excimer laser, there is a report by Endo et al. (Technical Research Report of the Institute of Electrical Communication, Vol.

[Problems to be solved by the invention]

As described above, the conventional resist material does not satisfy all the characteristics of sensitivity, resolution, and RIE resistance as a resist for KrF excimer laser, and cannot be put to practical use.

An object of the present invention is to provide an excimer laser resist capable of simultaneously satisfying the above three basic characteristics.

[Means for solving problems]

In order to achieve the above object, the present inventors have studied various materials, a photosensitive resin composition containing an aromatic ring-containing alkali-soluble resin and an aliphatic diazoketone as a main component, as a KrF excimer laser resist. The inventors have found that they are excellent and have reached the present invention.

First, in consideration of the fact that the resist material currently in practical use is a positive resist of an alkali development system, the present inventors have developed a KrF excimer laser resist as an alkali development so that it can be used without changing the current process. We decided to consider positive type resist.

Typical examples of the alkali-developable positive photoresist include a composition of an alkali-soluble cresol novolak resin and a photosensitive dissolution inhibitor naphthoquinone diazide sulfonate. However, although these resists have excellent resistance to reactive ion etching (RIE) as described above, their sensitivity and resolution have not reached the practical level. Therefore, we decided to search for the most suitable materials for the KrF excimer laser resist for the alkali-soluble base polymer and the photosensitive dissolution inhibitor.

Considering the main characteristics required for the base polymer for the KrF excimer laser resist, it has a large light transmission property at 249 nm. Great RIE resistance. There are two of them. Considering only the required characteristics, copolymers of methacrylic acid and methyl methacrylate are excellent, but their resistance to RIE is insufficient. In order to improve RIE resistance, it is necessary to introduce an aromatic ring into the base polymer. On the other hand, considering only the required characteristics, cresol novolac resin and the like are good, but the light transmittance at 249 nm is poor. In order to improve the light transmission, it is necessary to reduce the number of aromatic rings. Thus, it is very difficult to satisfy the required characteristics at the same time because the aromatic ring required for expressing RIE resistance inhibits the light transmittance at 249 nm, but in any case, It is necessary to add an aromatic ring to the base polymer. Therefore, as a result of examining various materials among the alkali-soluble resins containing an aromatic ring, which have excellent light transmittance at 249 nm, the following formulas (5), (6) and (7) are shown. It was found that the alkali-soluble resin represented by the formula (3) has a relatively excellent light transmittance at 249 nm and exhibits a transmittance of 50% or more at a film thickness of 1 μm.

It is not known how many of these resins have excellent light transmittance at 249 nm, but the common point is that the substitution mode of the benzene ring is symmetric with respect to the molecular axis passing through the OH group. These resins may be used alone, or two or more resins may be mixed and used.

On the other hand, the main characteristic required for a photosensitive dissolution inhibitor for KrF excimer laser resist is that it has a large light absorption at 249 nm. High quantum yield of photoreaction. In addition to the fact that the photoreaction product does not have absorption at 249 nm, in general, there is a large difference in the effect of inhibiting alkali dissolution before and after the photoreaction, a large compatibility with the base polymer, or an appropriate amount. Having crystallinity is also an important factor. The naphthoquinone diazide sulfonic acid ester conventionally used for UV does not satisfy the required characteristics because it has an aromatic ring in the molecule and cannot be used for KrF excimer laser. Therefore, we decided to study an aliphatic diazoketone that does not contain an aromatic ring so that the photoreaction product does not absorb light at 249 nm. First, as a result of various studies on aliphatic diazoketones satisfying the required characteristics, it was found that the compound represented by the following general formula (8) was an aliphatic diazoketone satisfying the above characteristics.

Here, R ₃ and R ₄ are monovalent organic groups containing no aromatic ring, and specifically, R ₃ is a C _{1 to} C ₁₀ alkyl group or And so on. R ₄ is a C ₁ -C ₁₀ alkoxy group. However, these compounds are generally required as photosensitive dissolution inhibitors. The characteristics such as a large difference in dissolution inhibitory effect, compatibility with the base polymer, and appropriate crystallinity were insufficient, and it was difficult to use as it was. Therefore, as a result of searching for a high-molecular-weight matrix capable of binding with an ester bond as R ₄ , it was found that licholic acid, deoxycholic acid, and lithocholic acid derivatives represented by the following general formulas (1), (2), and (3) are good. It was

However, R ₁ is H or a C _{1 to} C ₁₀ alkyl group, R ₂ is H or a group excluding R ₄ from the general formula (8), and the case where all OR ₂ groups are OH groups is excluded.

These compounds satisfy all the required properties as a photosensitive dissolution inhibitor for KrF excimer laser resist, and these compounds can be used alone or in the form of a mixture.

The composition of the alkali-soluble resin and the photosensitive dissolution inhibitor most suitable for the KrF excimer laser resist as described above becomes a KrF excimer laser resist excellent in sensitivity, resolution and RIE resistance.

Here, a general method of using the composition of the present invention for forming a pattern on a semiconductor device or the like will be described. 50 to 95 parts by weight of an alkali-soluble resin containing an aromatic ring (formulas (5), (6) and (7), which are used alone or in the form of a mixture) and an aliphatic diazoketone (general formulas (1) and (2)) ，
A compound represented by (3). These are used alone or in the form of a mixture. ) 50 to 5 parts by weight of a photosensitive resin composition is dissolved in an ordinary organic solvent, spin-coated on a silicon wafer, and prebaked at an appropriate temperature to form a film of the photosensitive resin composition of the present invention. To get Then, irradiate the desired pattern with KrF excimer laser light,
By developing using an alkaline aqueous solution, a positive pattern having a good shape can be obtained. In addition, the formed pattern exhibits excellent resistance to RIE such as CF ₄ RIE, and functions sufficiently as an etching mask.

[Action]

The alkali-soluble resin in the photosensitive resin composition of the present invention retains the excellent RIE resistance of the conventional resist material by containing an aromatic ring, and is also excellent in light transmittance at 249 nm to improve sensitivity and resolution. It is believed to help. Further, the photosensitive dissolution inhibitor used in the photosensitive resin composition of the present invention photoreacts effectively with 249 nm light, and since the reaction product has no light absorption at 249 nm, this is a bleaching action. It is considered that the sensitivity, resolution and resolution have been improved. It is considered that the sensitivity, resolution, and RIE resistance required for the KrF excimer laser resist could be satisfied at the same time by combining the above two main components.

〔Example〕

Hereinafter, some of the examples of the present invention will be specifically described, but the present invention is not limited thereto.

Example 1 80 parts by weight of the alkali-soluble resin represented by the formula (5) and the aliphatic diazoketone represented by the formula (1) (R ₁ is an isopropyl group, R ₃ is a methyl group, and the esterification rate of the OR ₂ group is 100%. ) 20
A weight part of the resist solution was spin-coated on a silicon wafer and prebaked at 85 ° C. for 30 minutes to form a resist film having a thickness of 0.8 μm.

This was exposed to various different doses of KrF excimer laser light, developed with an aqueous solution of tetramethylammonium hydroxide for 1 minute, and then washed with water for 1 minute, and then the thickness of the residual resist film was measured. Then, the residual film thickness (normalized) was plotted against the exposure dose (mJ / cm ² ), and the minimum exposure dose (sensitivity) at which the residual film thickness was zero was obtained, and it was about 100 mJ / cm ² It was confirmed to be a positive resist for the sensitive KrF excimer laser. Next, the resist film obtained in the same manner as above was subjected to reduction projection exposure (about 150 m) using a quartz mask.
J / cm ² ) and then developed under the same conditions as above,
It was confirmed that 0.5 μmL & S was able to be resolved, and the above resist had high resolution. In addition, the silicon wafer on which the resist pattern is formed is processed by a parallel plate type RIE device (CF ₄ = 0.
CF ₄ RIE was performed using 04torr, RF = 0.32W / cm ² ) and the etching rate of the resist was excellent at about 20nm / min.
It was confirmed to show RIE resistance.

Example 2 80 parts by weight of the alkali-soluble resin represented by the formula (5) and the aliphatic diazoketone represented by the formula (1) (R ₁ is an isopropyl group, R ₃ is a methyl group, and the esterification rate of the OR ₂ group is 75%). A resist film of 20 parts by weight was prepared in the same manner as in Example 1 and
When exposed and developed in the same manner as above, the sensitivity was about 130 mJ / cm ² , and 0.5
μmL & S was resolved. The CF ₄ RIE rate was almost the same as the value in Example 1.

Example 3 80 parts by weight of the alkali-soluble resin represented by the formula (5) and the aliphatic diazoketone represented by the formula (1) (R ₁ is an isopropyl group, R ₃ is a methyl group, and the esterification rate of the OR ₂ group is 40%). A resist film of 20 parts by weight was prepared in the same manner as in Example 1 and
When exposed and developed in the same manner as above, the sensitivity was about 170 mJ / cm ² , and 0.5
μmL & S was resolved. The CF ₄ RIE rate was almost the same as the value in Example 1.

From the above examples, it was confirmed that the compositions according to any of the examples were excellent in sensitivity, resolution and RIE resistance and were useful as a KrF excimer laser positive resist.

〔The invention's effect〕

As described above, the photosensitive resin composition of the present invention is 0.5
As a resist used in KrF excimer laser lithography for resolving line widths of μm or less, sufficient sensitivity,
It has resolution and RIE resistance is the same as the conventional one. Further, the photosensitive resin composition of the present invention can be handled in the same manner as the conventional one because it is of the alkali developing system, like the alkali developing resist which is the mainstream resist at present. As described above, the photosensitive resin composition of the present invention is extremely effective as a KrF excimer laser resist.

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Claims (3)

[Claims] 1. An alkali-soluble organic resin containing an aromatic ring,
A photosensitive resin composition containing, as a main component, at least one kind of an aliphatic diazoketone derived from cholic acid, deoxycholic acid or lithocholic acid. 2. The aliphatic diazoketone derived from cholic acid, deoxycholic acid or lithocholic acid is a derivative represented by the following general formulas (1), (2) and (3), respectively. The photosensitive resin composition according to claim 1. However, R ₁ is H or a C ₁ -C ₁₀ alkyl group, R ₂ is H or a diazoketone group represented by the following general formula (4),
Except when all of the OR ₂ groups are OH groups. Here, R ₃ is a monovalent organic group containing no aromatic ring. 3. A patent characterized in that the alkali-soluble organic resin containing an aromatic ring contains at least one kind of alkali-soluble organic resins represented by the following general formulas (5), (6) and (7). The photosensitive resin composition according to claim 1.