JP2583600B2 - Negative electron beam resist composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel negative-type electron beam resist composition. More specifically, the present invention can form a resist pattern having particularly excellent image contrast and cross-sectional shape, and can be developed with an organic alkali aqueous solution, for example, in the production of semiconductor devices such as transistors, ICs, LSIs, and super LSIs. The present invention relates to a negative electron beam resist composition suitably used.

Conventional technology Semiconductor devices such as transistors, ICs, LSIs, and VLSIs usually irradiate a light beam through a required patterning mask to a photosensitive resin film laminated on a substrate such as a silicon wafer, that is, a lithography method. By performing development and rinsing processing, after forming a resist pattern, it is manufactured by a method of forming a circuit on the substrate by repeating the operation of selectively etching or diffusing impurities several times to several tens of times the substrate. I have.

By the way, the recent miniaturization of processing dimensions in the semiconductor industry is remarkable, and the integration density of semiconductor memory is 16MDRAM, 64MDR
AM, 256MDRAM, and 1GDRAM are expected to evolve, and with this, many improvements in resist materials, reduction projection exposure apparatuses, and the like have been proposed in order to further reduce the processing dimensions.

For example, by combining an improved positive photoresist comprising a novolak resin and a naphthoquinonediazide compound with a reduction projection exposure apparatus, a resist pattern having a width of 0.4 to 0.5 .mu.m has been obtained. However, it has been difficult to achieve a processing size smaller than that even by such a combination.

On the other hand, recently, ASICs (Ap
As the demand for replication specific ICs is increasing, preparing a mask to create an ASIC that requires only a small amount with such special specifications is time-consuming and time-consuming. Therefore, a method of forming an electron beam resist film directly on a silicon wafer and directly drawing a resist pattern without using a mask has been studied. However, in this method, although a resist pattern of 0.5 μm or less can be relatively easily formed on a silicon wafer due to the process, it is necessary to draw directly by narrowing an electron beam irradiation spot.
In addition, in order to prevent the adjacent resist patterns from joining to each other in the resist material used in this method, the image contrast is good, that is, the difference in solubility between the electron beam irradiated part and the non-irradiated part in the developing solution is large, and Strict requirements are placed on characteristics such as the need to have an excellent cross-sectional shape.

On the other hand, as a photoresist material, for example, a photosensitive resin composition for printing comprising an amino resin, a melamine resin, and an organic halide (US Pat. No. 3,697,274),
A photosensitive coating composition comprising a novolak resin, a diazonaphthoquinone-based photosensitive acid generator and methylated melamine formaldehyde aminoplast (Japanese Patent Application Laid-Open No. 60-263143) is known. In general, there is no commonality between a photoresist material and an electron beam resist material, and it is not always possible to apply a photoresist to an electron beam resist. Therefore, conventional electron beam resists include, for example, polymethyl methacrylate (Japanese Patent Publication No. 45-30225), polyglycidyl methacrylate [Journal
Of the Electrochemical Society [J. Electroche
m. Soc.), Vol. 118, p. 669 (1974)], and chloromethylated polystyrene (JP-A-57-176034).

However, since these electron beam resists are developed with an organic solvent, there is a problem in the working environment.In addition, scum is likely to be generated in the resist pattern after development, and deterioration of the precision of the resist pattern such as bonding of adjacent fine patterns occurs. This has the disadvantage that it is difficult to obtain a resist pattern with good cross-sectional shape and image contrast.

On the other hand, thermosetting resin and photoacid generator 210-2
Aqueous developable resist composition comprising an irradiation source of excimer laser, marginal ultraviolet rays, X-rays, etc., comprising a halogenated organic compound absorbing actinic radiation in the range of 99 nm (JP-A-62-16)
No. 4045).

However, although this resist composition has been shown to be sensitive to electron beams, resist patterns obtained by irradiating electron beams have poor image contrast and
It is difficult to obtain high resolution because the cross-sectional shape is easy to pull out, and it takes a long development time to obtain a high-resolution pattern, which is not practical.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of the conventional electron beam resist composition, and can form a resist pattern having particularly excellent image contrast and cross-sectional shape, and can be developed with an organic alkali aqueous solution. The object of the present invention is to provide a negative-type electron beam resist composition having excellent characteristics such as being able to.

Means for Solving the Problems The present inventors have conducted intensive studies to develop a negative-type electron beam resist composition having the above excellent characteristics,
It has been found that the object can be achieved by a composition containing a specific triazine compound, a specific cresol novolak resin, an alkoxymethylated melamine resin and a specific ester compound, and the present invention is completed based on this finding. Reached.

That is, the present invention relates to (A) (Z in the formula is R ¹ and R ² are an alkyl group having 1 to 5 carbon atoms, R ³ and
R ⁴ is a hydrogen atom, a hydroxyl group or a carboxyl group, which may be the same or different from each other), (B) m-cresol
Cresol novolak resin obtained from cresol containing 30% by weight or more, (C) alkoxymethylated melamine resin, and (D) polyhydroxybenzophenone,
It is intended to provide a negative electron beam resist composition comprising an ester compound with 2-naphthoquinonediazide-4-sulfonic acid or 1,2-naphthoquinonediazide-5-sulfonic acid.

 Hereinafter, the present invention will be described in detail.

In the composition of the present invention, the triazine compound used as the component (A) has a structure represented by the general formula (I), and a typical example of such a compound is 2- (p-methoxyphenyl). ) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (p-ethoxyphenyl) -4,6-bis (trichloromethyl) -1,
3,5-triazine, 2- (p-propoxyphenyl)-
4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (p-butoxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (4-methoxynaphthyl) -4,6-bis (trichloromethyl) -1,3, 5−
Triazine, 2- (4-ethoxynaphthyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2-
(4-propoxynaphthyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (4-butoxynaphthyl) -4,6-bis (trichloromethyl) -1,3,5- Triazine and the like. These triazine compounds may be used alone or in combination of two or more.

A photopolymerizable composition using a triazine compound having a chloromethyl group as a photopolymerization initiator and a monomer having an ethylenically unsaturated group is known (Japanese Patent Application Laid-Open No. 62-212401). No examples have been known for use in electron beam resist compositions.

In the composition of the present invention, the cresol novolak resin used as the component (B) is m-cresol 30% by weight.
Cresol containing the above, preferably m-cresol
A mixed cresol containing at least 30% by weight and at least one selected from the group consisting of p-cresol, 2,5-xylenol and 3,5-xylenol as the remaining component, more preferably m-cresol; It must be obtained from a mixed cresol consisting of 30 to 70% by weight of cresol and at least 70 to 30% by weight of at least one selected from p-cresol and 3,5-xylenol.

By using such a cresol novolak resin, it is possible to form a resist pattern having excellent heat resistance and an excellent cross-sectional shape rising vertically from the substrate.

The cresol novolak resin is, for example, m-cresol, p-cresol, 2,5-xylenol and 3,5-
It can be easily produced by subjecting a mixed cresol containing at least one selected from xylenol at a predetermined ratio to formaldehyde to a condensation reaction in the presence of an acid catalyst. Further, in order to increase the solubility difference in the developer between the irradiated part and the non-irradiated part of the electron beam and to improve the image contrast, the weight average molecular weight of the cresol novolak resin is 2,000 to 20,000, preferably 3,000 to 15,000. Is practical.

In the composition of the present invention, the alkoxymethylated melamine resin used as the component (C) is obtained by converting a methylol group of a methylolated melamine obtained by an ordinary method into an alkoxymethyl group. By using a melamine resin converted to an alkoxymethyl group having an average of 2.5 or more, preferably 3.5 or more, a resist solution having extremely excellent storage stability can be obtained.
The type of the alkoxymethylated melamine resin is not particularly limited, and for example, methoxymethylated melamine resin, ethoxymethylated melamine resin, propoxymethylated melamine resin, butoxymethylated melamine resin, and the like can be used, but are commercially available in practical use. Nikarac Mx-750, Nikarac Mx-032, Nikarac Mx-706,
Nikarac Mx-708, Nikarac Mx-40, Nikarac Mx
-31, Nikarac Ms-11, Nikarac Mw-22, Nikarac Mw-30 (all trade names, manufactured by Sanwa Chemical Co., Ltd.) and the like can be preferably used. One of these alkoxymethylated melamine resins may be used alone, or two or more thereof may be used in combination.

In the composition of the present invention, as component (D), polyhydroxybenzophenone and 1,2-naphthoquinonediazide-
4-sulfonic acid or 1,2-naphthoquinonediazide-5
An ester compound with sulfonic acid is used. Preferred examples of the polyhydroxybenzophenone include, for example, 2,3,4-trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone, and 2,2 ', 4,4'-tetrahydroxybenzophenone. These polyhydroxybenzophenones may be used alone or in combination of two or more.

In the composition of the present invention, any ester compound as described above can be used. Particularly preferred ester compounds are those in which the hydroxyl groups of the polyhydroxybenzophenone used are 40% or more on average (hereinafter referred to as average esterification). 40% or more). By using a resist pattern having an average degree of esterification of 40% or more, the obtained resist pattern can significantly improve image contrast and cross-sectional shape.

In the present invention, the average degree of esterification means that the ester compound is analyzed by liquid chromatography (GPC), the number of hydroxyl groups and the number of naphthoquinone diazide groups in the ester compound are measured, and the number of naphthoquinone diazide groups /
It is a value calculated by (the number of hydroxyl groups + the number of naphthoquinonediazide groups) × 100.

The weight ratio of the cresol novolak resin of the component (B) to the alkoxymethylated melamine resin of the component (C) in the composition of the present invention is 6%.
It is desirable to use a ratio such that the ratio is 0:40 to 95: 5, preferably 75:25 to 90:10. (B) component and (C)
If the proportion of the components deviates from the above range, scum is generated in the development processing, or the cross-sectional shape of the obtained resist pattern is deteriorated, it is difficult to obtain a good image contrast, and Storage stability may also decrease, which is not preferred.

The triazine compound as the component (A) is used in an amount of usually 2 to 10% by weight, preferably 3 to 10% by weight, based on the total amount of the cresol novolak resin and the alkoxymethylated melamine resin.
-7% by weight. 2% by weight
If the amount is less than 10%, the object of the present invention cannot be sufficiently achieved.

On the other hand, the ester compound of the component (D) is usually 1 to 15% by weight, preferably 3 to 15% by weight, based on the total amount of the cresol novolak resin and the alkoxymethylated melamine resin.
It is blended in the range of 10% by weight. If the amount is less than 1% by weight, the object of the present invention cannot be achieved, and a practical resist pattern cannot be obtained. If the amount exceeds 15% by weight, the solubility of unexposed portions in a developing solution decreases. do it,
The contrast may be lowered, which is not preferable.

The negative-type electron beam resist composition of the present invention is usually used in the form of a solution obtained by dissolving the above components in an organic solvent. As the organic solvent used at this time, for example, ketones such as acetone, methyl ethyl ketone, cyclohexanone, and isoamyl ketone; ethylene glycol, propylene glycol, ethylene glycol monoacetate, diethylene glycol or diethylene glycol monoacetate monomethyl ether, monopropyl ether, monobutyl ether or Polyhydric alcohols such as monophenyl ether and derivatives thereof; cyclic ethers such as dioxane; and esters such as methyl acetate, ethyl acetate, butyl acetate and ethyl lactate.
These may be used alone or as a mixture of two or more.

The compositions of the present invention may, if desired, make compatible additives, such as additional resins, plasticizers, stabilizers or developed images more visible, as long as they do not detract from the objects of the present invention. Conventional additives such as a coloring agent and an antihalation dye can be added.

Next, a method for forming a fine pattern using the solution of the electron beam resist composition adjusted as described above will be described. First, a solution of the electron beam resist composition is formed on a substrate such as a silicon wafer. Is coated with a spinner or the like, dried and provided with an electron beam sensitive layer, and then selectively irradiated with an electron beam, and further heated at a temperature in the range of 90 to 140 ° C. to sensitize the developing sensitivity. And then for example 2
By developing using an organic alkali aqueous solution such as an aqueous solution of 5 to 5% by weight of tetramethylammonium hydroxide or choline, the non-irradiated portion of the electron beam is selectively dissolved and removed, and the image contrast and the cross-sectional shape are excellent. The resulting resist pattern can be obtained.

The heat treatment after the electron beam irradiation is a treatment for sensitizing the development sensitivity, and is indispensable to achieve the object of the present invention. When the processing temperature is lower than 90 ° C., practical sensitivity cannot be obtained. When the processing temperature is higher than 140 ° C., adjacent resist patterns in a fine pattern are easily bonded to each other, and it is difficult to obtain a good image contrast.

Although the composition of the present invention is an electron beam resist composition, X-rays or the like can be used as an irradiation source in addition to an electron beam.

Effect of the Invention The negative electron beam resist composition of the present invention comprises polyhydroxybenzophenone and 1,2-naphthoquinonediazide-4.
-By mixing an ester compound with sulfonic acid or 1,2-naphthoquinonediazide-5-sulfonic acid,
It is considered that the solubility of the electron beam irradiation portion in an alkali developing solution can be suppressed, and a practical resist pattern having an excellent cross-sectional shape can be obtained.

Since the composition of the present invention can form a resist pattern having excellent image contrast and cross-sectional shape and can be developed with an organic alkali aqueous solution, it is extremely useful as a resist for forming a fine pattern indispensable for the production of semiconductor devices such as VLSI. Useful.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 m-cresol and p-cresol were mixed at a weight ratio of 60:40, to which formalin was added, and a cresol novolak resin (weight-average molecular weight) obtained by condensation using a oxalic acid catalyst in a conventional manner. 4000) 4.5 g and 0.5 g of Nicalac Mx-750 (manufactured by Sanwa Chemical Co., Ltd.), which is a methoxymethylated melamine resin having an average degree of alkoxymethylation of 3.5, were dissolved in 15 g of ethyl lactate. 4% by weight of 2- (p-methoxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, based on the total amount of methoxymethylated melamine resin, is obtained by known methods. 1,2-naphthoquinonediazide-5-sulfonic acid ester of 2,3,4-trihydroxybenzophenone (average degree of esterification: 95 mol%) was added at a ratio of 3% by weight, respectively. Solution pore size 0.2μ
The resulting solution was filtered under pressure using a membrane filter of m to obtain a resist solution.

Next, the resist solution obtained in this manner is spin-coated at 4000 rpm for 20 seconds on a 4-inch silicon wafer surface-treated with hexamethyldisilazane, and dried on a hot plate at 80 ° C. for 90 seconds to form a 0.5 μm thick film. Was obtained. Next, the resist layer was selectively irradiated with an electron beam at an accelerating voltage of 20 kW using HHS-2R manufactured by Hitachi, Ltd., and then heat-treated at 110 ° C. for 90 seconds, and then 2.38 wt% tetramethylammonium hydroxide By dipping in an aqueous solution for 4 minutes, the non-irradiated portion of the electron beam was dissolved and removed to obtain a resist pattern. This resist pattern was confirmed by an electron microscope to be a 0.3 μm resist pattern having a residual film ratio of 90% or more in the irradiated area and a good cross-sectional shape that stood perpendicular to the silicon wafer surface. Was also very good, and there was no bonding between adjacent patterns. This cross-sectional shape is shown in the drawing.

Examples 2-11, Comparative Examples 1-6 Composition of cresol component in cresol novolak resin, type of alkoxymethylated melamine resin, mixing ratio of cresol novolak resin and alkoxymethylated melamine resin, type and amount of triazine compound and The same operation as in Example 1 was performed except that the type and the amount of the ester compound were changed as shown in the table, and the cross-sectional shape of the pattern of each resist composition was evaluated. The results are shown in the table. In Examples 2 to 11, resist patterns having a residual film ratio of 90% or more were obtained, and no joining between adjacent patterns could be confirmed. In contrast, Comparative Example 1
In Nos. To 6, many joints between adjacent patterns were confirmed in the fine pattern portion.

The cross section a of the pattern is shown in FIG.
FIG. 3 (c) means the one shown in FIG.

Note 1) The compounding amount based on the total amount of the component (B) and the component (C). 2) Nicalac Mx-750: the average degree of alkoxymethylation is 3.
5) Methoxymethylated melamine resin 3) Nicalac Mw-30: average degree of alkoxymethylation is 5.5
4) (A) -1: 2- (p-methoxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine 5) (A) -2: 2- (4-methoxynaphth) -4,6-bis (trichloromethyl) -1,3,5-triazine 6) (D) -1: 1,2-naphthoquinonediazide-5 of 2,3,4-trihydroxybenzophenone Sulfonate 7) (D) -2: 1,2-Naphthoquinonediazide-5-sulfonic acid ester of 2,2,3,4,4'-tetrahydroxybenzophenone 8) (D) -3: 2,2 ', 4 1,2-naphthoquinonediazide-5-sulfonic acid ester of 4,4'-tetrahydroxybenzophenone 9) (D) -4: 1,2-naphthoquinonediazide-4 of 2,2 ', 4,4'-tetrahydroxybenzophenone -Sulfonic acid esters

[Brief description of the drawings]

1, 2 and 3 are different cross-sectional shapes of the resist pattern.

Claims (7)

(57) [Claims] (1) General formula (A) (Z in the formula is R ¹ and R ² are an alkyl group having 1 to 5 carbon atoms, R ³ and
R ⁴ is a hydrogen atom, a hydroxyl group or a carboxyl group, which may be the same or different from each other), (B) m-cresol
Cresol novolak resin obtained from cresol containing 30% by weight or more, (C) alkoxymethylated melamine resin, and (D) polyhydroxybenzophenone,
A negative electron beam resist composition comprising an ester compound with 2-naphthoquinonediazide-4-sulfonic acid or 1,2-naphthoquinonediazide-5-sulfonic acid. 2. The cresol novolak resin contains at least 30% by weight of m-cresol, and at least one selected from p-cresol, 2,5-xylenol and 3,5-xylenol as a remaining component. 2. The negative electron beam resist composition according to claim 1, wherein the composition is obtained from a mixed cresol. 3. The mixed cresol comprises 30 to 70% by weight of m-cresol and 70 to 30% by weight of at least one selected from p-cresol and 3,5-xylenol. Negative electron beam resist composition. 4. The negative electron beam resist composition according to claim 1, wherein the alkoxymethylated melamine resin has an average degree of alkoxymethylation of 2.5 or more. 5. The method of claim 2, wherein the polyhydroxybenzophenone is 2,3,4-
5. The method according to claim 1, which is at least one selected from trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone and 2,2 ', 4,4'-tetrahydroxybenzophenone. The negative-type electron beam resist composition as described in the above. 6. An ester compound having an average degree of esterification of 40%.
The negative electron beam resist composition according to any one of claims 1 to 5, which is as described above. 7. The negative electron beam resist composition according to claim 1, wherein the ester compound is blended in an amount of 1 to 15% by weight based on the total amount of the cresol novolak resin and the alkoxymethylated melamine resin. Stuff.