JPS63186233A - Positive type photoresist composition - Google Patents

Abstract

PURPOSE:To increase the gamma and sensitivity by incorporating specified cresol-formaldehyde novolak resin and a specified quinonediazido compd. in a specified ratio. CONSTITUTION:This positive type photoresist compsn. contains cresol- formaldehyde novolak resin (A) and 1,2-naphthoquinone-2-diazido-4-sulfonic ester (B) of one or more kinds of benzophenone drives. such as 2,4- dihydroxybenzophenone and 2,3,4-trihydroxybenzophenone in 95/5-80/20wt. ratio of A/B. The novolak resin is obtd. by bringing the cresol mixture of 20/80-45/55wt. ratio of m-cresol/p-cresol into addition condensation with formaldehyde. When the photoresist compsn. is irradiated with UV having 200-300nm wavelength, the gamma and sensitivity are increased.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a positive photoresist composition, and particularly to a positive photoresist composition.
By irradiating ultraviolet rays with a wavelength in the 00 to 300 nm range, the resolution is significantly superior and the sensitivity is improved.
The present invention relates to a positive resist composition for nm wavelength exposure.

<Prior art> A photosensitive resin composition containing a compound having a quinonediazide group such as a naphthoquinonediazide group or a benzoquinonediazide group becomes alkali-insoluble because the quinonediazide group is decomposed by light irradiation of 300 to 500 nm to produce a carboxyl group. It is used as a positive photoresist by utilizing the fact that it changes from an alkali-soluble state to an alkali-soluble state.

In this case, the photosensitive resin composition is generally used in combination with a novolak resin. Compositions using novolak resins also form uniform and durable resist coatings. This positive-type photoresist has a feature of superior resolution compared to negative-type photoresists, and has been particularly recently used as an etching protective film for photolithography when manufacturing highly integrated circuits such as ICs and LSIs. Its usage is increasing.

By the way, with the progress of semiconductor technology, the degree of integration, that is, the miniaturization has progressed more and more, and submicron resolution of 1 μm or less is now required. Under these circumstances, there is a strong demand for positive photoresists with good pattern shapes and improved resolution.

One way to increase resolution is to expose the resist to light with a shorter wavelength. The exposure wavelength of the reduction projection exposure machine currently generally used for LSI manufacturing is 436
nm (so-called G-rays), but this can be combined with shorter wavelength light, such as deep UV light (200-300nm).
Exposure at m) is expected to improve resolution. However, the commercially available positive photoresists that are currently mainly used have a larger absorption coefficient in the deep LIV region than the G-line, so when exposed to deep UV light, the light does not reach the bottom of the resist. This results in extremely inconvenient problems such as a decrease in sensitivity or a poor profile of the resist pattern after development (a so-called streaked shape).

Therefore, the current situation is that the positive photoresists mainly used at present are not necessarily satisfactory in terms of sensitivity and resolution when an exposure wavelength of 200 to 300 nm is used.

<Problems to be Solved by the Invention> By the way, the γ value is an important index corresponding to resolution. As a definition of γ value, here the exposure amount is E
, when the developing speed of the exposed area changes from R1 to R2, T=(log L-1og
L)/(log Ex-1og E,).

The larger this value is, the larger the change in development speed with respect to the change in exposure amount becomes, meaning that the sharpness of the pattern becomes better.

The purpose of the present invention is to provide extremely high resolution (i.e., γ
The object of the present invention is to obtain a positive photoresist composition for exposure at a wavelength of 200 to 30 Qnm, which has a high value) and improved sensitivity.

<Specific means for solving the problem> The present inventors
As a result of intensive research, we found that a certain type of Talesol-
When a positive photoresist composition containing a formaldehyde novolac resin and a specific quinonediazide compound in a specific ratio was used, it was surprisingly found that
It has been discovered that the γ value is significantly improved and high sensitivity is exhibited when irradiated with ultraviolet light having a wavelength in the nm range, and the present invention has been completed.

That is, the present invention provides meta-cresol/para-cresol=
Cresol-formaldehyde novolac resin (A) obtained by addition condensation of meta- and para-mixed cresol and formaldehyde in a ratio of 20/80 to 45155 (weight ratio), and 2,4-dihydroxybenzophenone, 2
, 3.4-trihydroxybenzophenone, 2.2'
4,4'-tetrahydroxybenzophenone, 2.3,
4,4'-tetrahydroxybenzophenone, 2.2
',3,4゜4'-pentahydroxybenzophenone,
1.2-naphthoquinone-2-diazide-4-sulfonic acid ester of one or more benzophenone derivatives selected from benzophenone derivatives consisting of 2',3,4,5'-pentahydroxybenzophenone (
B) In a positive photoresist composition containing (A
>> (B) = 9515 to 80/20 (weight ratio) A positive photoresist composition for wavelength exposure of 200 to 300 nm.

The present invention will be described in more detail below.

For the cresol-formaldehyde novolak resin (A) used in the present invention, meta- and para-mixed cresol in a ratio of meta-cresol/parasol=20/80 to 45155 (weight ratio) is used as a raw material. The ratio of meta-cresol to para-cresol greatly affects the sensitivity and resolution of the resist.

In other words, when the proportion of para-cresol is increased, the resolution improves, but the sensitivity decreases. If the m-cresol/p-cresol ratio is less than 20/80, it will be difficult to increase the molecular weight of the polymer, making it impractical. Conversely, if the proportion of metacresol is increased, the sensitivity will improve, but the resolution will decrease.

The inventors of the present invention made extensive studies to balance these conflicting sensitivity and resolution, and found that by using a mixed cresol in the range of meta-cresol/para-cresol = 20/80 to 45155, a balance between sensitivity and resolution was achieved. It has been found that a resist composition can be obtained. The mixed cresol of the present invention is a mixture of meta-cresol and para-cresol in the above ratio, but a commercially available mixed cresol of meta- and para-cresol may also be used.

In addition, the formaldehyde to be subjected to the addition condensation reaction with this meta- and para-mixed cresol is a formaldehyde aqueous solution (
Formalin) and paraformaldehyde, which is an oligomer of formaldehyde, are used. In particular, 37% formalin is conveniently produced because it is industrially mass-produced.

Novolak resin is obtained by polymerizing these phenols and formaldehyde using commonly used acids or organic acid salts of divalent metals as catalysts.

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-toluenesulfonic 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 carried out at 60 to 120°C for 2 to 20 hours.

Next, regarding the molecular weight of novolak resin, the optimum range varies depending on the mixing ratio of metacresol and paracresol, the type of catalyst, and the reaction conditions, but in general, G
The weight ratio average and molecular weight (M w ) determined by PC are 2.0
0 (1 to 30,000, more preferably 4°000 to 2
0.000 is appropriate.

The MW shown here is a value calculated from a GPC chromatogram using a calibration curve obtained using monodisperse polystyrene, and the GPC chromatogram was measured using a 635 type liquid chromatograph manufactured by Hitachi as a column. H2C-15, ) (SG-40, H2C manufactured by Shimadzu Corporation)
-60 each connected in series, tetrahydrofuran was used as a carrier solvent, and the flow rate was 1°Qml/min.

Next, the photosensitizer component (B) used in the present invention will be described.

The photosensitizer components used in the present invention include 2.4-dihydroxybenzophenone, 2.3.4-trihydroxybenzophenone, 2.2',4,4'-tetrahydroxybenzophenone, 2.2',3゜4, 1,2-naphthoquinone-2-diazide-4-sulfone of one or more benzophenone derivatives selected from 4'-pentahydroxybenzophenone, 2゜2',3,4,5'-pentahydroxybenzophenone It is an acid ester. These esters are 1,2-naphthoquinone-2-diazide-
It is obtained by condensing 4-sulfonic acid chloride and benzophenone derivatives in the presence of a weak alkali.

In addition, cresol-formaldehyde novolak resin (
The blending ratio of A) and quinonediazide compound (B) is (A)/
(B) must be in the range of 9515 to 80/20 (weight ratio). If it is outside this range, the sensitivity and/or resolution of the positive photoresist may be impaired, which is not preferable.

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 coating film after the solvent evaporates at an appropriate drying rate. Such are methyl cellosolve acetate, methyl cellosolve acetate, ethyl cellosolve, methyl cellosolve,
Examples include propylene glycol monomethyl ether, propylene gelcol methyl ether acetate, butyl acetate, methyl isobutyl ketone, and xylene.

The positive photoresist composition described above may further contain small amounts of resin, plasticizer, dye, etc. as additional additives.

<Effects of the Invention> According to the present invention, it is possible to obtain a positive-working photoresist composition that has extremely excellent resolution and improved sensitivity, particularly to irradiation with ultraviolet rays having a wavelength in the range of 200 to 3 QQ nm. .

<Examples> Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Reference example 1 (Novolac resin synthesis example 1) Internal volume 1.0
Metacresol 108 in a 00+nl Mitsuro flask
After charging 162 g of para-cresol (metacresol/para-cresol = 40/60 weight ratio),
% oxalic acid ice water 50g, 37% formalin 140g
was added. The reaction temperature was controlled at 110 to 115° C. by immersing the flask in an oil bath while stirring, and the reaction was carried out for 10 hours to synthesize a novolac resin. After the reaction, neutralize with alkali and add ethyl cellosolve acetate 200
g 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 8.300.

Reference Example 2 (Synthesis Example 2 of Novolak Resin) Into the same apparatus as Reference Example 1, 81 g of metacresol and 1 g of paracresol were added.
89g (metacresol/valacresol = 30/70
(weight ratio), then add 50 g of 5% ice water,
140 g of 37% formalin was added. While stirring, the flask was immersed in an oil bath to control the reaction temperature at 110 to 115°C, and the reaction was carried out for 15 hours to synthesize a novolac resin. 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 a solution of novolac resin in ethyl cellosolve acetate. The weight average molecular weight of this novolak resin is 7.50.
It was 0.

Reference Example 3 (Synthesis Example 3 of Novolak Resin) Into the same apparatus as in Reference Example 1, 189 g of metacresol 1 81 g of para-cresol (metacresol/para-cresol = 70/30)
(weight ratio), then 50 g of 5% oxalic acid,
140g-ti of 37% formalin was added. While stirring, immerse the flask in an oil bath to bring the reaction temperature to 110-115°C.
A novolak resin was synthesized by controlling the reaction time and reacting for 8 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 a solution of novolac resin in ethyl cellosolve acetate. The weight average molecular weight of this novolac resin is 8.700
Met.

Examples and Comparative Examples The novolak resins obtained in Reference Examples 1 to 3 were added to Table 4 along with various quinonediazide compounds as shown in Table 1.
Dissolved in ethyl cellosolve acetate with the composition shown in 1,
A resist solution was prepared. The amount of ethyl cellosolve acetate is determined when the resist film thickness is 1.5 mm under the coating conditions shown below.
The thickness was adjusted to 27 μm.

Each of these compositions was filtered through a 0.2 μm Teflon product filter to prepare a resist solution. This was applied to a silicon wafer cleaned by a conventional method using a spin coater to coat it for 4.0%.
Coated with OOr, p9m. The silicon wafer was then placed in a clean oven previously kept at 90° C. for 30 minutes to dry. Next, add C to this wafer.
Deep UV aligner-PLA- manufactured by anon■
Using 521F (using cold mirror 250),
Exposure was performed by changing the exposure amount stepwise.

A positive pattern was obtained by developing this with a 2.38% aqueous solution of tetramethylammonium hydroxide for 1 minute. By plotting the amount of resist film wear (or development speed) against the exposure amount, resist sensitivity and γ can be determined.
I found the value.

2 These results are summarized in Table-1. As is clear from Table 1, the γ values of Examples 1 to 4 are much better than those of Comparative Examples 1 to 4.

Claims (1)

[Claims] Meta-cresol/para-cresol = 20/80-45/
Cresol obtained by addition condensation of meta and para mixed cresol and formaldehyde in a ratio of 55 (weight ratio)
Formaldehyde novolac resin (A) and 2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone , 2,2',3,4,4'-pentahydroxybenzophenone, 2,2',3,4,5'-
A positive photoresist composition containing 1,2-naphthoquinone-2-diazide-4-sulfonic acid ester (B) of one or more benzophenone derivatives selected from benzophenone derivatives consisting of pentahydroxybenzophenone, (A)/(B)=95/5~8
20 characterized by being in the range of 0/20 (weight ratio)
A positive photoresist composition for exposure to wavelengths of 0 to 300 nm.