JPH0654391B2 - Positive resist composition for electron beam or X-ray - Google Patents

Description

TECHNICAL FIELD The present invention relates to a positive resist composition having high sensitivity to electron beams or X-rays, and particularly to a positive resist for electron beams or X-rays having a remarkably excellent resolution. It relates to a composition.

<Prior Art> The miniaturization of semiconductor integrated circuits has advanced along with the increase in density, and at present, submicron level pattern formation is required. Along with this, the era of using electron beams or X-rays for forming fine patterns is approaching even in the lithography technology.

Of these, especially electron beam lithography has already been put to practical use in the manufacture of high-precision photomasks, but the development of a straight line drawing system for performing fine processing directly on a semiconductor element substrate is also in progress. Generally, the biggest drawback of this system is that the writing speed is slow (that is, the throughput is low) as compared with the case of optical lithography.

From a practical point of view, if a resist that is highly sensitive to electron beams and has high resolution is developed, the utility value of this system will be further enhanced.

From this point of view, looking at electron beam resists currently being developed, it cannot be said that all of the required performances described above are satisfied. For example, in terms of sensitivity, a negative electron beam resist is generally superior to a positive electron beam resist, but in terms of resolution, particularly in the case of a negative resist using an organic solvent for development, swelling during development, The resolution tends to be inferior to that of a positive resist. On the other hand, a positive type electron beam resist is generally superior in resolution but tends to be inferior to a negative type in terms of sensitivity. That is, there is no satisfactory electron beam resist having high sensitivity and high resolution, and there is a strong demand for excellent materials.

<Problems to be Solved by the Invention> By the way, an important index corresponding to the resolution is the γ value. As the definition of the γ value, here the exposure dose is E ₁
When the developing speed of the exposed area changes from R ₁ to R ₂ when changing from E ₂ to E ₂ , γ = (log R ₂ −log R ₁ ) / (log E ₂
-Log E ₁ ). The larger this value, the larger the change in the developing speed with respect to the change in the exposure amount, and the better the pattern cuts.

An object of the present invention is to obtain a positive resist composition for electron beam or X-ray, which has excellent resolution (that is, high γ value) and improved sensitivity.

<Specific Means for Solving Problems> As a result of intensive studies, the inventors of the present invention used a composition containing a quinonediazide compound and a specific cresol-formaldehyde novolac resin in a specific ratio, which was surprising. In particular, they have found that both the resolution and the sensitivity are significantly improved, and have completed the present invention.

That is, the present invention provides a positive resist composition containing a quinonediazide compound and a cresol-formaldehyde novolak resin, wherein (1) the resin is meta-cresol / para-cresol = 30/7
A cresol-formaldehyde novolak resin having a weight average molecular weight of 2,000 to 15,000 obtained by addition-condensing meta- and para-mixed cresol and formaldehyde in a proportion of 0 to 50/50 (weight ratio) (2) Quinonediazide compound and the resin The ratio of 1: 2
The positive resist composition for electron beam or X-ray is characterized by being in a range of 1: 5 (weight ratio).

The present invention will be described in more detail below.

The quinonediazide compound used in the present invention is a compound containing a naphthoquinonediazide group or a benzoquinonediazide group, and these are, for example, a compound having a naphthoquinonediazidesulfonic acid chloride or benzoquinonediazidesulfonic acid chloride and a hydroxyl group in the presence of a weak alkali. Obtained by condensation. Examples of the compound having a hydroxyl group include hydroquinone, resorcin, phloroglucin, 2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone,
Examples thereof include alkyl hydroxyesters of gallic acid, tetrahydroxybenzophenones such as 2,2 ′, 4,4′-tetrahydroxybenzophenone and 2,3,4,4′tetrahydroxybenzophenone, and pentahydroxybenzophenones.

Next, the resin component will be described.

As a raw material of the novolac resin used in the present invention, meta- and para-mixed cresols having a ratio of meta-cresol / para-cresol = 30/70 to 50/50 (weight ratio) are used. The ratio of meta-cresol to para-cresol greatly affects the sensitivity and resolution of the resist. That is, if the proportion of para-cresol is increased, the resolution is improved, but the sensitivity is lowered. When the ratio of meta-cresol / para-cresol is 20/80 or less, the molecular weight of the polymer is hard to increase, which is not practical. On the contrary, if the proportion of meta-cresol is increased, the sensitivity is improved but the resolution is lowered.

As a result of diligent studies to balance such contradictory sensitivity and resolution, the present inventors used metacresol / paracresol = mixed cresol in the range of 30/70 to 50/50 as a raw material to obtain sensitivity and resolution. It was found that a well-balanced resist composition can be obtained.
As the mixed cresol of the present invention, meta-cresol and para-cresol may be mixed and used in the above-mentioned ratio, or meta- and para-mixed cresol commercially available may be used.

As the formaldehyde to be subjected to the addition condensation reaction with the meta- and para-mixed cresol, an aqueous formaldehyde solution (formalin) or paraformaldehyde which is an oligomer of formaldehyde is used. In particular, 37% of formalin is industrially mass-produced, which is convenient.

The novolak resin is obtained by polymerizing these phenols and formaldehyde using a commonly used acid or an organic acid salt of a divalent metal as a catalyst.

The acid used as a catalyst may be either an inorganic acid or an organic acid. Specific examples thereof include hydrochloric acid, sulfuric acid, phosphoric acid, p-toluenesulfonic acid, acid and trichloroacetic acid.

Examples of organic salts of divalent metals include acetates, formates, lactates and benzoates of metals such as magnesium, manganese, zinc, cadmium, cobalt and lead. Alternatively, it may be a combination of the above-mentioned acids and an organic acid salt of a divalent metal. The reaction can be carried out in bulk or using a suitable solvent. The reaction is usually carried out at 60 to 120 ° C. for 2 to 20 hours.

Next, regarding the molecular weight of the novolac resin, the optimum range will differ depending on the mixing ratio of meta-cresol and para-cresol, the type of catalyst, and the reaction conditions.
The weight average molecular weight (Mw) calculated from 2,000 to 15,000,
More preferably, 3,000 to 12,000 is suitable.

The Mw shown here is a value calculated from a GPC chromatogram using a calibration curve obtained using monodisperse polystyrene, and the GPC chromatogram is measured by a column of a 635 type liquid chromatograph manufactured by Hitachi, Ltd. As HSG-15, HSG-4 manufactured by Shimadzu Corporation
0 and HWG-60 each connected in series were used, and tetrahydrofuran was used as a carrier solvent at a flow rate of about 1.0 ml / min.

Moreover, it is preferable to use the compounding ratio of the quinonediazide compound and the novolak resin in the range of 1: 2 to 1: 5 (weight ratio). If it deviates from this range, the sensitivity and / or the resolution as a positive resist will be impaired, which is not preferable.

The resist solution is prepared by mixing and dissolving the quinonediazide compound and the novolac resin in a solvent. The solvent used here is preferably one which gives a uniform and smooth coating film after the solvent is evaporated at an appropriate drying rate. As such, ethyl cellosolve acetate, methyl cellosolve acetate, ethyl celloselbu, methyl celloselbu,
Examples include propylene glycol monomethyl ether, propylene glycol methyl ether acetate, butyl acetate, methyl isoptyl ketone, and xylene.

The positive resist composition described above may further contain a small amount of a resin, a plasticizer, a dye or the like as an additional addition.

<Effects of the Invention> According to the present invention, a positive resist composition having remarkably excellent resolution and improved sensitivity can be obtained.

<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.

Reference Example 1 Metacresol 108 was added to a three-neck flask with an internal volume of 1,000 ml.
After charging 162 g of para-cresol (meta-cresol / para-cresol = 40/60 weight ratio), 30 g of 5% oxalic acid water and 130 g of 37% formalin were added. The novolak resin was synthesized by immersing the flask in an oil bath with stirring to control the reaction temperature at 95 to 100 ° C. and reacting for 9 hours.

After the reaction, the mixture was neutralized with an alkali, 200 g of ethyl cellosolve acetate was added, washed with water and dehydrated to obtain an ethyl cellosolve acetate solution of novolak resin.

The weight average molecular weight of this novolak resin was 5,400.

Reference Example 2 In the same device as in Reference Example 1, 81 g of meta-cresol and 189 g of para-cresol (meta-cresol / para-cresol = 30 /
70% by weight), 5% oxalic acid 50% and 37% formalin 140 g were added. Immerse the flask in an oil bath with stirring to control the reaction temperature at 95-100 ° C and
A novolak resin was synthesized by reacting for a time.

After the reaction, the mixture was neutralized with an alkali, 200 g of ethyl cellosolve acetate was added, washed with water and dehydrated to obtain an ethyl cellosolve acetate solution of novolak resin.

The weight average molecular weight of this novolak resin was 3,300.

Reference Example 3 In the same device as in Reference Example 1, 135 g of meta-cresol and 135 g of para-cresol (meta-cresol / para-cresol = 50 /
50% by weight), then 5% oxalic acid water 50g, 37%
Formalin 140 g was added. While stirring, immerse the flask in an oil bath to control the reaction temperature at 95-100 ° C,
A novolak resin was synthesized by reacting for 9 hours.

After the reaction, the mixture was neutralized with an alkali, 200 g of ethyl cellocerve acetate was added, washed with water, and dehydrated to obtain a solution of novolac resin in ethyl cellosolve acetate. The weight average molecular weight of this novolak resin was 6,500.

Reference Example 4 In the same device as in Reference Example 1, 189 g of metal cresol and 81 g of paracresol (metacresol / paracresol 70
(/ 30 weight ratio), then 5% oxalic acid 50g, 37%
142 g of formalin was added. While stirring, immerse the flask in an oil bath to control the reaction temperature at 95-100 ° C,
A novolak resin was synthesized by reacting for 7 hours.

After the reaction, the mixture was neutralized with an alkali, 200 g of ethyl cellocerve acetate was added, washed with water, and dehydrated to obtain a solution of novolac resin in ethyl cellosolve acetate.

The weight average molecular weight of this novolak resin was 5,500.

Reference Example 5 In the same device as in Reference Example 1, 216 g of meta-cresol and 54 g of para-cresol (meta-cresol / para-cresol 80/2
Then, 30 g of 5% oxalic acid and 182 g of 37% formalin were added. Immerse the flask in an oil bath with stirring to control the reaction temperature at 95-100 ° C, and
A novolak resin was synthesized by reacting for a time.

After the reaction, the mixture was neutralized with an alkali, 200 g of ethyl cellosolve acetate was added, and the mixture was washed with water and dehydrated to obtain an ethyl cellosolve acetate solution of novolak resin.

The weight average molecular weight of this novolak resin was 7,100.

Examples and Comparative Examples The novolak resins obtained in Reference Examples 1 to 5 were dissolved in ethyl cellosolve acetate with the composition shown in Table 1 together with the quinonediazide compound to prepare resist solutions. The amount of ethyl cellosolve acetate was adjusted so that the resist film thickness would be 4,000Å under the coating conditions shown below.
As the quinonediazide compound, naphthoquinone- (1,2) -diazide (2) -5-sulfonic acid chloride and 2,3,4-trihydroxybenzophenone are used herein as 1.
A condensation reaction was performed at a ratio of 2: 1 (molar ratio).

Each of these compositions was filtered through a 0.2 μm Teflon filter to prepare a resist solution. This was washed on a silicon wafer by a conventional method with a spin coater at 4,000 rp.
applied at m. Then, this silicon wafer was put in a clean oven previously kept at an internal temperature of 80 ° C. for 30 minutes to be dried.

Then, this wafer was exposed stepwise using an electron beam irradiation device at an acceleration voltage of 20 kv and an incident dose of 0.1 to 30 μc / cm ² .

This was developed with a 2.5% aqueous solution of tetramethylammonium hydroxide for 1 minute to obtain a positive pattern. Amount of resist film variation (or development speed) with respect to exposure amount
The resist sensitivity and the γ value were determined by plotting

These results are summarized in Table-1. As is clear from Table-1, the γ values of Examples 1 to 3 are superior to those of Comparative Examples 1 to 4.

It should be noted that almost the same results were obtained even when the X-ray irradiation device was used instead of the electron beam irradiation device and the same operation was performed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kokazu Uemura 3-98 Kasugade, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Chemical Co., Ltd. (72) Inventor Katsumi Tanigaki 5-chome, Shiba, Minato-ku, Tokyo No. 33-1 NEC Corporation (72) Inventor Makoto Kita No. 33-1, Shiba 5-chome, Minato-ku, Tokyo Inside NEC Corporation (56) Reference JP-A-62-27732 (JP, A) JP-A-60-42753 (JP, A) JP-A-62-35349 (JP, A)

Claims (1)

[Claims] 1. A positive resist composition containing a quinonediazide compound and a cresol formaldehyde novolac resin, wherein (1) the resin is metacresol / paracresol = 30 /
A cresol-formaldehyde novolak resin having a weight average molecular weight of 2000 to 15000, obtained by addition-condensing meta- and para-mixed cresol and formaldehyde in a proportion of 70 to 50/50 (weight ratio), which comprises (2) a quinonediazide compound and Resin ratio is 1: 2
A positive resist composition for electron beam or X-ray, which is in a range of 1: 5 (weight ratio).