JPS61275748A - Positive type photoresist composition - Google Patents

Abstract

PURPOSE:To obtain a resist adapted to use in formation of highly integrated circuits and the like, high in sensitivity and dry etching resistance, and superior in heat resistance, and capable of forming a pattern high in resolution and precision by incorporating a specified alkali-soluble novolak resin and a photosensitive agent contg. a quinonediazide group. CONSTITUTION:The positive type resist film capable of forming a pattern higher in resolution than conventional ones with higher sensitivity and suitable for manufacture of LSI or the like by coating a support with a solution prepared by dissolving in an org. solvent a mixture of the alkali-soluble resin component (A) obtained by mixing m-cresol (I) with 3,5-dimethylphenol (II) in the range of a molar ratio satisfying the equation shown on the right, and additionally polymerizing this mixture with formaldehyde; and the photosensitive agent component (B) having the quinonediazide group, such as naphthoquinonediazide or benzoquinonediazide group, in a (B)/(A) weight ratio of 1:1-1:7; and drying the coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive photoresist composition having improved S degree, heat resistance, and dry etching resistance.

A photosensitive resin composition containing a compound having a quinonediazide group such as a naphthoquinonediazide group or a benzoquinonediazide group changes from an alkali-insoluble state to an alkali-soluble state by decomposing the quinonediazide group and producing a carboxyl group when irradiated with light of 300 to 500 nm. It is used as a positive photoresist by taking advantage of the fact that

In this case, borac resins are usually used in combination. . Novolalik resin is important for obtaining uniform and durable resist coatings. This positive photoresist has a feature of significantly superior resolution compared to negative photoresists.

Taking advantage of this high resolution, steel-clad laminates for printed wiring, I
It is used to manufacture integrated circuits such as C and LSI.

Among these circuits, the miniaturization of 'a' product circuits has progressed as a result of higher integration, and it is now required to form a pattern with an IBtn width. Conventionally, a mask contact method has been used to form integrated circuits, but this method is said to have a limit of 2 μm, and a reduction projection exposure method is attracting attention as an alternative.

This method is a method in which the pattern of a master mask (reticle) is reduced and projected using a lens system for exposure, and the resolution can be up to about 1^m.

However, one of the problems with this reduction projection exposure method is that
One problem is that the throughput is low. That is, unlike a batch exposure method such as the conventional mask contact method, the reduction projection exposure method involves division (repeated exposure), so the problem is that the total exposure time per sea urchin becomes longer.

The most important way to solve this problem is to improve the sensitivity of the resist used, as well as improving the equipment. If exposure time can be shortened by increasing sensitivity, throughput and yield can be improved.

From this point of view, the 4e di-type photoresists currently used are not necessarily satisfactory in terms of sensitivity. Generally, digital photoresists have lower sensitivity than negative photoresists, and improvements are desired.

The easiest way to achieve high sensitivity is to lower the molecular weight of the novolatile resin used in positive photoresists.

When the molecular weight of the novolak resin is low, its dissolution rate in an alkaline developer increases, and the apparent sensitivity of the resist increases. However, with this method, the film thickness in the unexposed area becomes thicker (the so-called film remaining rate decreases), the pattern shape deteriorates, and the difference in dissolution rate in the developer between the exposed area and the unexposed area becomes smaller. In addition to the problem of a decrease in the so-called r (gamma) value caused by this, the extremely serious disadvantage of a decrease in the heat resistance of the resist occurs.

The heat resistance of a positive photoresist here means the resistance of a resist pattern to heat after development. More specifically, when heat is applied from the outside world to a resist pattern formed on a substrate, the resist pattern will sag or deform if the temperature exceeds a certain level. The heat resistance of the resist is measured by whether the pattern can maintain its sharp shape without deformation. If the resist pattern is sagged or deformed, the dimensions of the species to be etched after etching may be distorted or variations may occur, and the resist cannot function as an etching protective film required of the resist. In other words, the yield is significantly reduced, which is not preferable.

Now, as the degree of integration of LSI increases, the pattern line width continues to become finer, and dry etching technology is increasingly being used to replace the conventional wet etching as one means of achieving finer patterning. It is used.

-There are various methods for dry etching the mouth. Among them, the method most commonly used these days is called reactive ion etching (RIE). This is an anisotropic etching that combines the sputtering effect of directional ions and chemical etching using highly reactive plasma, and is suitable for obtaining extremely fine patterns. The advantages of this method are that it does not require treatment of waste liquid such as hydrofluoric acid, which is required in the case of wet etching, and it eliminates the side etching (wrapping into the resist base) that is often seen in wet etching. Since there is no such thing, it is easy to obtain fine patterns. The disadvantage that was previously said to be that the wafer processing speed was slower than wet etching is being overcome through improvements in equipment, and now,
It can be said that this technology is indispensable for improving the degree of integration.

On the other hand, from the viewpoint of cysts, the current situation is that with the spread of dry etching technology, the resist itself is increasingly required to have dry etching resistance. During dry etching, the resist is required to maintain its sharp pattern shape.

Generally, "B selectivity" is used as an index of this dry etching resistance. This is defined as the ratio of the etching speed of the underlying layer (the pattern to be etched) to the etching speed of the resist, and the larger the value, the better.

The selection ratio of currently used positive photoresists is not necessarily satisfactory, although it depends on the underlying material (the pattern to be etched), the etching gas, etc. In particular, when the substrate is aluminum, or even more special metals such as molybdenum, tungsten, etc., or their silicides are being used, the dry etching conditions become stricter and the selectivity decreases, making it difficult for current positive photoresists. It is difficult to say that it has sufficient dry etching resistance.

On the other hand, according to the study results of the present inventors, it was found that there is an extremely strong correlation between the dry etching resistance and heat resistance. In other words, if the resist has low heat resistance,
It is easily deformed and carbonized during dry etching.

This is thought to be due to the fact that considerable heat is generated during dry etching.

There is also a relationship between dry etching resistance and heat resistance in another sense. That is, in order to improve the dry etching resistance, a method is often used in which the temperature of the so-called "bost bake" which is usually carried out after the formation of the etched pattern and before etching is increased. Although the detailed reason is unknown, increasing the post-bake temperature tends to improve dry etching resistance.

However, if the post-bake temperature is increased when the heat resistance of the resist is low, the resist pattern will already be sagging or deformed at that stage, and this will be exacerbated during dry etching, making it difficult to obtain a desirable etching result. is insolent.

From these facts, it can be said that improving the heat resistance of a resist is nothing but improving its dry etching resistance.

Now, the three major characteristics required of a resist are "sensitivity".
Examples include "resolution" and "dry etching resistance."

Sensitivity is important for throughput, and resolution and dry etching resistance are important for integration density. any one of these
If one is missing, it can no longer be used as a resist, so all three must be excellent.

Now, if we look at these three, they tend to be contradictory in some respects in terms of "sensitivity" and "dry etching resistance." That is, as mentioned above, in the case of a di-type photoresist, if the molecular weight of the novolac resin is lowered in order to increase the sensitivity, the heat resistance deteriorates, and as a result, the dry etching resistance is impaired. Conversely, if the molecular weight is increased in order to improve dry etching resistance, the dissolution rate in the developer decreases and the sensitivity decreases. That is, at present 7, there is no commercially available positive photoresist that has both sensitivity and dry etch resistance, and an extremely inconvenient situation exists in which if an attempt is made to improve one, the other becomes even worse.

In view of the current situation, the present inventors have developed a positive photoresist that improves both "sensitivity" and "dry etching resistance" without impairing the other, and has excellent resolution. As a result of intensive study, it was discovered that this object could be achieved by using a specific novolac resin, and the present invention was achieved.

That is, the present invention comprises (B) a photosensitizer component containing a quinone azide group and (B) an alkali-soluble resin component containing metacresol (rito 3,5-dimethylphenol (I)) as represented by the following formula. The present invention provides a positive photoresist composition containing a novolak resin obtained by addition-condensation reaction of phenols and formaldehyde mixed in such a ratio.

The present invention will be described in more detail below.

The photosensitizer containing a quinonediazide group (B) is a compound containing a naphthoquinonediazide group or a benzoquinonediazide group. It can be obtained by condensation in the presence of Examples of compounds having a hydroxyl group include hydroquinone, resorcinol, phloroglucin, 2.4-dihydroxybenzophenone, 2.3.4-)dihydroxybenzophenone, gallic acid alkyl ester, 2.2,4.4-tetrahydroxybenzophenone. etc.

Next, the alkali-soluble resin component of @ will be described. The alkali-soluble resin component that can be used in the present invention is a novolak resin obtained by an addition condensation reaction from a phenolic compound and formaldehyde, but the phenols that are the raw materials for the novolak resin include metacresol (I) shown below. ) and 3,5-dimethylphenol (Nioga formula (
It is necessary for the mixture to have a proportion that satisfies the following.

(I) (IO) When the ratio of formula (e) is smaller than 0.3, the rate at which the novola drop resin dissolves in the developer becomes slow, causing a problem that it takes time to develop the exposed area.

If this ratio exceeds 0.9, the resist's heat resistance and dry etching resistance will deteriorate.

More preferably, the formula (equation) is in the range of 0.5 to 0.7.

Next, formaldehyde to be subjected to an addition condensation reaction with phenols will be explained.

As formaldehyde, formaldehyde aqueous solution (
Formaldehyde (formalin) and paraformaldehyde, which is an oligomer of formaldehyde, can be used. Especially 37%
Formalin is conveniently produced in large quantities industrially.

These phenols and formaldehyde are polymerized using a commonly used acid or an organic acid salt of a divalent metal as a catalyst to obtain a novola-type resin.

The acid used as a catalyst may be either an inorganic acid or an organic acid. Specific examples include hydrochloric acid, sulfuric acid, phosphoric acid, P-)luenesulfonic acid, oxalic acid, and trichloroacetic acid.

Examples of organic acid 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. Further, the reaction can be carried out either in bulk or by using a suitable solvent. The reaction is usually 60-120℃, 2 hours-20
Do time.

Next, regarding the molecular weight of novolak resin, the optimum range varies depending on the mixing ratio of phenols, type of catalyst, and reaction conditions, but in general, the weight average molecular weight Mw determined by GPC is 2.000 to 30,000. , more preferably 4,000 to 20,000.

The Mw shown here is a value calculated from a GPC chromatogram using a calibration curve obtained using monodisperse polystyrene. As, H2C-15, H2C-40, manufactured by Shimadzu Corporation.
Using one H2C-60 each connected in series,
Also, using tetrahydrofuran as a carrier solvent,
Flow velocity 1. It was performed at Ott/min.

Further, the blending ratio of the quinonediazide compound and the novolak resin is preferably in the range of 1:1 to 1 (it amount).

The resist solution is prepared by mixing and dissolving a quinonediazide compound and a novolak resin in a solvent. The solvent used here is preferably one that provides a uniform and smooth heavy film after the solvent evaporates at an appropriate drying rate. Examples of such solvents include ethyl cellosolve acetate, methyl cellosolve acetate, ethyl cellosolve, methyl cellosolve,
Butyl acetate, methyl isobutyl ketone, xylene, etc. are removed.

The positive photoresist composition described above may further contain small amounts of additional resins, plasticizers, dyes, etc. as additional additives.

According to the present invention, "dry etching resistance" can be improved without reducing "sensitivity", and conversely, a highly sensitive positive photoresist can be obtained without impairing "dry etching resistance", and Each of these properties has better performance and resolution than conventional positive photoresists, making it extremely suitable for use in the semiconductor industry, which is expected to continue to become more highly integrated and miniaturized in the future. It is possible to obtain a positive-type photoresist that can be used.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples.

Reference example 1 Production example of novolac sul (1) Metacresol/3,5-dimethylphenol-1/1 (molar ratio of charge) (purity 99.0%) 37.5 F, formalin (37%)
Aqueous solution) 44.9F, 5% oxalic acid aqueous solution 12.5N, ion-exchanged water 66.0 II, and ethyl cellosolve acetate 61.5F were heated in a 100℃ oil bath for 15 hours, stirred, and reacted, neutralized, washed with water, Dehydrated and novolac mat
An ethyl cellosolve acetate solution was obtained.

Weight average molecular weight by GPC chromatography is 6.50
It was 0.

Reference Example 2 Production example of novolak resin (Kumetacresol 73.5-dimethylphenol-1/1 (molar ratio of charge) (purity 99.0%) 37.51, formalin (37% aqueous solution) 44.91, zinc acetate dichloride After charging 0.661 g of hydrate and heating, stirring, and reacting in a 100°C oil bath for 0.5 hours, 1.02 f of oxalic acid dihydrate, 6 g of ion-exchanged water, and 60 g of ethyl cellosolve acetate were charged. The mixture was reacted for 8 hours, neutralized, washed with water, and dehydrated to obtain a solution of novolac resin in ethyl cellosolve acetate.

Weight average molecular weight by GPC chromatography is 5.90
It was 0.

Reference Example 3 Production example of Novola 9-resin (3) Meta-cresol 73.5-dimethylphenol-773 (charged molar ratio) Other than that, the same procedure as Reference Example 1 was carried out, M2 average molecular t7,50
0 novolac resin was obtained.

Reference Example 4 Manufacture example of novolac mat (4) Metacresol 73.5-dimethylphenol = 2/8 (Mole ratio of charging) The same procedure as Reference Example 1 was carried out except that the time was changed to 20 hours, and the weight average molecular weight was 6.100. A novolac resin of 100% was obtained.

Reference Example 5 Manufacture example of Novolac mlli (5) Metacresol 73.5-dimethylphenol = 1/9 (Mole ratio of charge) The reaction time after adding metacresylic acid dihydrate to the charge in Reference Example 2 was 15 A novola resin having a weight average molecular weight of 5.300 was obtained in the same manner as in Reference Example 2 except that the time was changed.

Reference Example 6 Production Example of Novolac Resin (6) Metacresol 73.5-dimethylphenol = 9.510.5 (Mole ratio of charge) The same procedure as Reference Example 1 was carried out except that 10 hours was used, and the weight average molecular weight was 7.80.
0 novolac resin was obtained.

Examples 1-3. Comparative Examples 1 to 3 As shown in Table 1, the novolac resins shown in Reference Examples 1 to 6 were mixed together with a photosensitizer and a dye in a solvent with a mixing ratio of ethyl cellosolve acetate/n-butyl acetate/xylene = 8/1/1. A resist solution was prepared. (The amount of solvent was adjusted to give a 1.25 μm groove under the coating conditions shown below.) These compositions were filtered through a filter with a pore size of 0.2 μm. This was coated at 4.0007 pm on a silicon wafer which had been cleaned using a conventional method using a spin coater. This silicon wafer was then placed in a clean oven at 90°C and baked for 20 minutes. Then, using a contact mask aligner using a 250W ultra-high pressure mercury lamp as the light source,
Exposure was made for 3 seconds through a step-table lat mask with graded optical transmission. The film was then developed with 5OPD (aqueous tetramethylammonium hydroxide solution manufactured by Sumitomo Chemical Co., Ltd.) for 70 seconds, rinsed, and dried. Table 1 shows the results.
Shown below. As is clear from Table 1, Examples 1 to 3 are significantly superior to Comparative Examples 1 to 3 in terms of sensitivity and heat resistance.

Claims (1)

[Scope of Claims] Metacresol (I) represented by the following formula and 3,5-dimethylphenol (A) a photosensitizer component containing a quinonediazide group and (B) an alkali-soluble resin component
II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I)▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) Formula (III) 0.3≦(I)/((±)+(II)) A positive photoresist composition containing a novolac resin obtained by addition condensation reaction of phenols and formaldehyde mixed in a ratio satisfying ≦0.9 (molar ratio)