JPH02222955A - Positive type photosensitive composition - Google Patents

Abstract

PURPOSE:To provide the composition having excellent dimensional accuracy and pattern shape, and good heat resistance and long-term preservable stability by dissolving a specific photosensitizer and cresol novolak resin into ethyl lactate. CONSTITUTION:The cresol novolak resin is dissolved as a resin component into the ethyl lactate and the ester compd. which is derived from one kind of the polyhydroxy compd. selected from 2,3,4-trihydroxybenzophenone, 2,2',4,4'- tetrahydroxybenzophenone, 2,3,3',4-tetrahydroxybenzophenone, and 2,3,4,4'- tetrahydroxybenzophenone and at least one kind of the sulfonic acid compd. selected from 1,2-naphthoquinonediazide-4-sulfonic acid and 1,2- naphthoquinonediazide-5-sulfonic acid and has >=75% average degree of esterification is dissolved as the photosensitizer therein. The photosensitive compsn. having the excellent dimensional accuracy and pattern shape and the good heat resistance and preservable stability is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel positive-working photosensitive composition. More specifically, the present invention has excellent dimensional accuracy and pattern shape, as well as good heat resistance and storage stability.
The present invention relates to a positive photosensitive composition suitable for forming fine patterns in the manufacture of semiconductor integrated circuit devices such as VLSIs.

Conventional technology In recent years, demand for industrial computers, office automation, personal computers, etc. has expanded dramatically in the semiconductor industry11, and the technology has continued to develop rapidly. However, the density and degree of integration are rapidly increasing. In addition, in forming fine patterns, the pattern width is approximately 2
μm 1.0 to 1.3 μm for 11 megabit DRAM,
Furthermore, as 4 megabit DRAMs are integrated to a size of 0.7 to 0.8 .mu.m, microfabrication technology on the so-called submicron order is becoming necessary.

Currently, pattern formation in the manufacture of semiconductor integrated circuit devices is carried out by photolithography, and positive photoresist I. is widely used for microfabrication with a pattern width of about 2 μm or less. .

This positive photoresist is usually composed of an alkaline solution-soluble novolak resin and a photodegradable component called a photosensitizer. As for the alkaline solution-soluble novolak resin, the use of phenol-formaldehyde novolac resin has been disclosed, for example. (U.S. Pat.
980)].

Furthermore, by appropriately selecting the blending ratio of cresol isomers during the production of cresol novolac resin, we can produce highly sensitive positive photo-type photo[/cyst (Japanese Patent Application Laid-open No. 171-171-2) and positive-type photopolymer with excellent dimensional accuracy. It is also known that a deaf photoresist (Japanese Unexamined Patent Publication No. 62-35349) can be obtained.

On the other hand, as a photosensitizer, for example, gostyl sulfonate, which is a combination of the photodegradable component naphthoquinonediazide sulfonic acid and a compound having a 7I-nol hydroxyl group, is often used.
, various disclosures have been made so far (), '''° Pano (Saikoku Patent No. 30M11.8 Specification, Saikoku Patent No. 1306465-1 Specification, Saikoku Patent No. 3148983 Specification, Japanese Patent Publication No. 1984-284)
Publication No. 57).

By the way, when etching a substrate using a submicron-order resist pattern formed on the substrate by photolithography as a mask, a dry etching method using plasma or the like with a small amount of side etching is usually used. . In this dry etching method, the resist pattern used as a mask is damaged and the film is gradually reduced when etching the substrate, but the etched substrate also has a pattern that faithfully corresponds to the mask pattern. Good dimensional accuracy and cross-sectional shape are required for the 2nd, 2nd, and 5th patterns. Furthermore, in order to reduce film loss of the resist pattern, it is effective to increase the post-baking temperature after development, and therefore, the resist pattern is required to have excellent heat resistance.

However, conventional positive 1 photosensitive compositions do not necessarily fully satisfy these requirements. In addition, it is usually composed of an alkali-soluble novolac resin and a photosensitizer, and if a solution is prepared by dissolving these in a solvent, the solution may decompose during storage and the sensitivity may change, or once dissolved. It has drawbacks in terms of storage stability, such as the photosensitizer recrystallizing and precipitating, impairing the uniformity of the solution.

When considering the interaction between the solute and the solvent regarding the stability of a solution, it is necessary that the solvent has a large solute-dissolving power and that the solute is kept stable for a long period of time. The solvent in the positive photosensitive composition has a strong dissolving power for both the photosensitizer and the coating film forming material,
It is important to form a uniform solution regardless of its concentration and to be able to provide a uniform and smooth coating film. Such solvents are appropriately selected depending on the type of solute, but since many compounds containing quinone diazide groups, which are photocene compounds, are generally poorly soluble, solvents such as methylpyrrolidone, cyclopenta, non-, Only specific ones such as cyclohexanone, en-1/glycol monoethyl goteracetate-1, ethoxypropyl acetate can be used.

However, methylpyrrolidone, cyclopentanone,
In photosensitive compositions using cyclohexanone as a solvent, the photosensitizer gradually decomposes during storage.
In addition to inevitably reducing photosensitivity, this solvent is expensive, making it unsuitable for practical use. Furthermore, in photosensitive compositions using ethylene glycol monoethyl ether acetate and ethoxypropyl acetate as solvents, photosensitizer tends to precipitate as crystals during long-term storage. When the material is applied onto a substrate, it tends to form crystals, which has a negative effect on the formation of fine patterns, so its range of use is inevitably limited.

Therefore, in this technical field, there has been a strong desire to develop a practical positive-working photosensitive composition that has excellent dimensional accuracy and pattern shape, good heat resistance, and excellent storage stability.

Problems to be Solved by the Invention The present invention has been developed to meet these demands and to provide a positive-type photosensitive material that has excellent dimensional accuracy and pattern shape, good heat resistance and long-term storage stability, and is practical for forming fine patterns. It was made for the purpose of providing a sexual composition.

Means for Solving the Problems The present inventors have conducted extensive research in order to develop a positive photosensitive composition having the above-mentioned preferable properties. As a result, the present inventors have discovered that a specific photosensitizer and a cresol novolac resin are dissolved in ethyl lactate. As a result, the inventors discovered that the object could be achieved, and based on this knowledge, they completed the present invention.

That is, in the present invention, in ethyl lactate, (A) a cresol novolac resin as a resin component, and (B) 2.3.4-trihydroxybenzophenone, 2.2', 4.4'- as a photosensitizer. At least one polyhydroxy compound selected from tetrahydroxybenzophenone, 2.3.3',4-tetrahydroxybenzophenone and 2.3.4.4'-tetrahydroxybenzophenone and 1.2-naphthoquinone diazide. 4
-sulfonic acid and 1,2-naphthoquinonediazide-5-
Provided is a positive photosensitive resin composition comprising a solution in which at least one sulfonic acid compound selected from sulfonic acids and an ester compound derived from sulfonic acids and having an average degree of esterification of 75% or more are respectively dissolved. It is.

The present invention will be explained in detail below.

In the composition of the present invention, the cresol novolac resin used as the resin component (A) is composed of m-cresol and p-cresol.
- those obtained from cresol mixtures with -cresol are preferred, in particular from 10 to 45% by weight of m-cresol and p-cresol.
Those obtained from a cresol mixture containing 90 to 55% by weight of cresol are suitable because they provide a resist pattern with extremely excellent heat resistance, dimensional accuracy, and pattern shape.

On the other hand, the photosensitizer (B) includes 2.3.4-trihydroxybenzophenone, 2.2',4.4'-tetrahydroxybenzophenone, 2.3.3',4-tetrahydroxybenzophenone and 2,3 .4.4'-
at least one polyhydroxybenzophenone selected from tetrahydroxybenzophenones, and 1.2
-su7toquinone diazido 4-sulfonic acid or 1,2-
It is an ester compound obtained by reacting naphthoquinonediazide-5-sulfonic acid or a mixture thereof.

This ester compound is preferably one in which all the hydroxyl groups of the polyhydroxybenzophenone are esterified with the sulfonic acid, but in reality, in the esterification reaction, an average of 7 hydroxyl groups of the polyhydroxybenzophenone
It can be used as long as 5% or more is esterified.

If the esterification of the hydroxyl groups of the polyhydroxybenzophenone is less than 75% on average, the dimensional accuracy and pattern shape of the resulting resist pattern will deteriorate. Further, in the composition of the present invention, any photosensitizer that is esterified to an average of 75% or more can be used;
If the photosensitive component of the composition contains 80% by weight or more of the -E esterified compound, a resist pattern with improved heat resistance can be obtained.

Such a photosensitizer is, for example, 2.3°4-
Trihydroxybenzophenone, 2.2',4.4'-
Tetrahydroxybenzophenone, 2.3.3',4-
Tetrahydroxybenzophenone and 2.3.4.4'
- Preferably at least 3 times the mole of 1,2-naphthoquinonediazide-4-sulfonyl chloride or 1,2-7toquinonediazide per mole of at least one polyhydroxybenzophenone selected from tetrahydroxybenzophenones. It can be easily produced by a known method of reacting in an organic solvent in the presence of 5-sulfonyl chloride. Note that the average degree of esterification can be determined by liquid chromatography.

Regarding the blending ratio of the cresol novolak resin, which is the resin component (A), and the photosensitizer (B) in the composition of the present invention, the photosensitizer is blended at a ratio of 10 to 30 parts by weight per 100 parts by weight of the cresol novolac resin. It is preferable to do so.

If the amount of the photosensitizer is less than 10 parts by weight, dimensional accuracy, pattern shape, heat resistance, etc. will be poor.

The purpose of the present invention cannot be fully achieved, and if it exceeds 30 parts by weight, sensitivity decreases, which is not preferable.

In the composition of the present invention, ethyl lactate is used as a solvent for dissolving the cresol novolak resin and photosensitizer. The amount of ethyl lactate to be used is not particularly limited as long as it can be applied to the coated substrate to form a uniform thin film layer, but it is usually based on the total solid content, that is, the Frazier crucible resin and the photosensitizer. and the total amount thereof is in the range of 3 to 50% by weight based on the total amount of the composition. If the solid content is less than 3% by weight, the residual film rate in unexposed areas tends to decrease, and if it exceeds 50% by weight, the sensitivity tends to decrease, which is not preferable.

This ethyl lactate has a large dissolving power for the photosensitizer, suppresses recrystallization of the photosensitizer, has excellent stability, and has low toxicity, making it extremely useful in practice. be.

The compositions of the present invention may also contain, for example, sensitizers, other additional resin plasticizers, stabilizers, or additional colorants to make the formed image more visible, as well as other materials commonly used in the art. Various additives can be included.

By the way, when high resolution is required, such as with a photoresist for manufacturing a hard mask, it is preferable to set the photoresist film thickness to about 0.2 μm, but if the composition of the present invention is used, the solid content concentration can be reduced. 3 to 5% by weight.
Spin code may be performed at a rotational speed of 000 rpm. In addition, if it is necessary to coat a substrate with large differences in level,
In the conventional method, a so-called multilayer resist method was used in which a photosensitive composition was applied after filling the recesses, but with the composition of the present invention, the solid content can be reduced to 40 to 50% by weight.
Since there is almost no increase in viscosity even at high concentrations, spin footing is possible, and even for substrates with steps, it is possible to create a thick film of about 3 μm by simply spin-coding directly onto the substrate without filling the recesses in advance. you can get
A fine pattern with high resolution can be formed on a substrate with steps.

Next, to give an example of a preferred method of using the composition of the present invention, first, on a support such as silicone foam,
A positive photosensitive composition prepared by dissolving the cresol novolac resin as the resin component (A) and the photosensitizer (B) in ethyl lactate is coated with a spin coater or the like, and then dried to form a photoresist. Let it form.

Next, using a light source that emits ultraviolet rays, such as a low-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, arc lamp, or xenon lamp, exposure is performed through a required mask pattern, or irradiation is performed while scanning an electron beam. Next, when this is immersed in a developer, for example, a weak alkaline aqueous solution such as a 1 to 2% by weight aqueous sodium hydroxide solution or an organic alkaline aqueous solution such as a tetramethylammonium hydroxide aqueous solution, the portions made solubilized by exposure to light are selectively removed. After being dissolved and removed, a positive image faithful to the mask pattern is obtained.

Effects of the Invention The positive photosensitive composition of the present invention has significantly higher stability than conventional compositions, and ethyl lactate has extremely weak decomposition or decomposition-promoting power on the photosensitizer used in the present invention. The photosensitive composition does not deteriorate in photosensitive properties, retains high resolution even after long-term storage, has excellent storage stability, and produces fine patterns that have excellent dimensional accuracy, pattern shape, and good heat resistance. can be formed. In addition, the composition is extremely advantageous in practice since it is safe to work with since the toxicity of ethyl lactate used as a solvent is low. teeth,
Because it has excellent solubility in both the photosensitizer and cresol novolak resin used in the present invention,
Even if the solid content concentration is increased, the viscosity will not increase.It can be applied directly to substrates with steps, and even when applied to substrates with steps, the resolution remains high regardless of the coating thickness. It is possible to form a fine pattern with excellent dimensional accuracy and pattern shape, and good heat resistance, without reducing the heat resistance.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

Example 1 Esterification reaction product of 1 mole of 2.2',4.4'-tetrahydroxybenzophenone and 4 moles of 1,2-naphthoquinonediazide-5-sulfonyl chloride in 75 g of ethyl lactate (average degree of esterification 85%) ) Cresol novolak resin 209 obtained by condensing formalin with a cresol mixture of 40% by weight of m-cresol and 60% by weight of p-talesol is dissolved, and this is passed through a membrane filter with a pore size of 0.45 μm. − filtered with
A positive photosensitive composition solution was prepared. This stuff at 25℃
The temperature was maintained at a constant temperature, and a time-course test was conducted to determine the generation of gel-like substances. To confirm the gel-like substance in the aging test, coat a 3.00 g
We investigated a method of applying the composition at a rotation speed of 0 rpm and observing it with a spotlight to confirm whether or not a gel-like substance is generated. According to this method, the temporal deterioration and stability of the composition after filtration can be easily determined.

As a result of this time-lapse test, no gel-like substance was observed even after 3 months had passed after filtration, and the composition had extremely excellent storage stability.

This composition was coated with a spin coater 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 1.28 μm thick resist layer. formed. Next, reduction projection exposure device N5R-1505c4
After exposure treatment using a method (manufactured by Kon Co., Ltd.), 100
A resist pattern was obtained by heat-treating for 90 seconds at 'o' and immersing it in a 2.38 wt % tetramethylammonium hydroxide aqueous solution for 65 seconds. As a result of observing the obtained resist pattern with an electron microscope, a resist pattern of 0.55 um in thickness, faithful to the mask, and having a good cross-sectional shape cut perpendicularly from the silicon wafer surface was obtained. This cross-sectional shape is shown in FIG.

Next, this resist pattern was heated with a hot plate, and the temperature at which flow occurred was measured, and it was found to be 135° C., confirming that the resist pattern had excellent heat resistance.

Examples 2 to 17, Comparative Examples 1-10 Storage stability, The results of evaluating the cross-sectional shape and heat resistance are shown in Tables 1 and 2.

[Note] l) Storage stability (1) Foreign matter O: No gel-like substance was observed even after 3 months in a time-course test for the generation of gel-like substances at a constant temperature of 25°C ×: 25°C (2) Sensitivity O: No change in sensitivity in the resist properties after storage at a constant temperature of 25°C for 1 month. Not observed ×: Changes in sensitivity were observed in the resist properties after storage at a constant temperature of 25°C for one month 2) Cross-sectional shape Figure 1 shows the cross-sectional shape of the resist pattern obtained after the development process. Corresponding to a1 Corresponding to Figure 2 b1
The one corresponding to FIG. 3 is shown as C.

3) °Bake the sample after heat-resistant development on a hot plate kept at 130°C for 5 minutes, check for flow phenomenon in the resist pattern, and mark those with no flow phenomenon as 70-
Items where a phenomenon occurred are marked with an x.

[Brief explanation of the drawing]

1, 2 and 3 are diagrams showing different cross-sectional shapes of resist patterns, respectively.

Claims (1)

[Claims] 1. In ethyl lactate, (A) cresol novolak resin as a resin component, (B) 2,3,4-trihydroxybenzophenone, 2,2 as a photosensitizer
',4,4'-tetrahydroxybenzophenone, 2,
3,3',4-tetrahydroxybenzophenone and 2
, 3,4,4'-tetrahydroxybenzophenone, 1,2-naphthoquinone diazide-4-sulfonic acid and 1
, 2-naphthoquinonediazide-5-sulfonic acid, and an ester compound derived from the group consisting of at least one sulfonic acid compound having an average degree of esterification of 75% or more. sexual composition. 2 Cresol novolac resin is m-cresol 10~
2. The positive-working photosensitive composition according to claim 1, which is obtained from a cresol mixture of 45% by weight of p-cresol and 90 to 55% by weight of p-cresol.