KR20220081693A - Resist composition for Lift-off process - Google Patents

Abstract

The present invention relates to a positive resist composition for a lift-off process, an alkali-soluble base resin comprising a polymer of 2-(methacryloyloxy)ethyl acetoacetate and methacrylic acid, and an acid generating acid upon exposure It is a composition consisting of agents and solvents.
With the composition of the present invention, a pattern having an undercut shape for which high heat resistance is required is obtained, and a strong film is obtained by prebaking and post-exposure heating, and it becomes possible to obtain a pattern excellent in shape.
In addition, compared to the conventional resist composition for a single-layer lift-off process, the adhesion to the substrate is high and the transmittance is excellent, so that the photosensitive efficiency by exposure is improved.

Description

Resist composition for Lift-off process

The present invention relates to a resist composition for a lift-off process.

A lift-off method is known as a means for forming various metal wiring patterns, such as aluminum, copper, and tantalum, on a semiconductor substrate. In the lift-off method, for example, a resist composition is applied on a substrate, exposed through a mask, developed to form a resist pattern on the substrate, and then a metal film is formed on the resist pattern and on the metal substrate by sputtering or vapor deposition. Then, the resist pattern and the metal film on the pattern are peeled together to form a metal wiring on the substrate. A preferable resist pattern shape used in this lift-off method is a shape having an undercut called a microgroove in the lower portion of the resist pattern (substrate grounding portion).

On the other hand, known chemically amplified resist compositions are made by dissolving a base resin and an acid generator that generates an acid upon exposure in a solvent, and in which alkali solubility changes due to the action of the acid by the acid generator.

As a patent for a conventional positive lift-off resist composition having an undercut shape, the demonstration of an undercut by an aromatic hydroxy compound is described in Japanese Patent Application Laid-Open Nos. 8-69111 and Hei 10-97066. has been This is because the aromatic hydroxy compound has an alkali solubility suitable for generating an undercut near the substrate and controlling its size.

However, the conventional technique using a composition of such a novolak resin and a quinonediazide compound has a problem in that, when a high temperature is maintained when forming a film, the pattern is easily deformed under the influence of heat and a desired film cannot be formed. That is, it was difficult to obtain a resist pattern having a good shape because the allowable range of the temperature to be treated during the heat treatment was narrow.

An object of the present invention is to provide a lift-off resist composition capable of forming a pattern that is not deformed even at a high temperature of 120° C. or higher in order to solve the above problems.

In order to solve the above problems, the present invention provides a lift-off process comprising 0.5 to 5.0 parts by weight of an acid generator that generates an acid by exposure and 100 to 400 parts by weight of a solvent based on 100 parts by weight of a solid content of an alkali-soluble base resin A positive resist composition for a lift-off process is provided, wherein the base resin is a polymer of 2-(methacryloyloxy)ethyl acetoacetate and methacrylic acid.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to obtain the pattern which has an undercut shape by which high heat resistance is calculated|required.

Moreover, a strong film|membrane is obtained by prebaking and heating after exposure, and it becomes possible to obtain the pattern excellent in shape.

On the other hand, there is provided a resist composition for a lift-off process in which photosensitivity efficiency by exposure is improved due to high adhesion to a substrate and excellent transmittance compared to a conventional resist composition for a single-layer lift-off process.

The present invention provides a positive resist composition for a lift-off process comprising a base resin, an acid generator and a solvent, wherein the base resin is composed of a polymer of 2-(methacryloyloxy)ethyl acetoacetate and methacrylic acid. do it with

The base resin is a material that accounts for most of the solid content of the resist, and should have excellent film forming ability and high thermal stability, and at the same time exhibit a property of being soluble in an aqueous alkali solution, which is a developer. The first characteristic to be considered in the design of the base resin is the improvement of solubility in aqueous alkali solution. This improves the solubility of the exposed part and suppresses the solubility of the unexposed part to maximize the difference in solubility, thereby making it possible to make a highly sensitive resist, and to obtain a good profile in a thick film.

In the present invention, as a base resin, a polymer obtained by polymerizing 2-(methacryloyloxy)ethyl acetoacetate (MA(acac)) of the following formula (1) and methacrylic acid (MAA) of the following formula (2) as a monomer may be used. .

The polymer is prepared by dissolving 2-(methacryloyloxy)ethyl acetoacetate (MA(acac)) and methacrylic acid (MAA) in tetrahydrofuran at 30-35° C., and azobismethylbuty as an initiator in a nitrogen atmosphere. Ronitrile (2,2'-azobis(methylbutyronitrile, AMBN)) or azobisisobutyronitrile (AIBN) is added, and the temperature is slowly raised to 60~80℃ to dissolve and react, and the reaction solution is diethyl ether It can be prepared by treatment with a polymer to precipitate, filtration and drying.

In the reaction, the molar ratio of 2-(methacryloyloxy)ethyl acetoacetate (MA(acac)) and methacrylic acid (MAA) is preferably 1 to 1.5 to 2.5, and the initiator is the 2-(methacryl It is preferable that it is 0.1-0.3 mol with respect to 1 mol of royloxy)ethyl acetoacetate (MA(acac)).

The reaction time is preferably 12 to 15 hours.

The polymer preferably has a weight average molecular weight of 3,000 to 18,000. If the weight average molecular weight is small, it is difficult to maintain the coating film, and the decrease in the coating film after development occurs too large. If the weight average molecular weight is large, the solubility in the solvent is poor and the sensitivity is lowered, the development speed may be deteriorated, and the resist pattern cross-sectional shape may be deteriorated.

The acid generator is converted from poorly soluble in alkaline aqueous solution to soluble in alkaline aqueous solution by an acid component generated by exposure.

As the acid generator, any known acid generator used in conventional chemically amplified resist compositions may be used without limitation. Such acid generators include iodonium salt or sulfonate acid generators, oximesulfonate acid generators, bisalkyl or bisarylsulfonyl diazomethanes, poly(bissulfonyl)diazomethanes, diazomethanes Various types of acid generators such as diazomethane acid generators such as nitrobenzyl sulfonates, iminosulfonate acid generators, and disulfone acid generators are known.

In addition, as a sulfonic acid ester compound, 1,2-benzoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinone-2-diazide-5-sulfonic acid ester, 1,2-naphthoquinone-2 -Diazide-4-sulfonic acid ester, 1,2-naphthoquinone-2-diazide-5-sulfonic acid ester-orthocresol ester, 1,2-naphthoquinone-2-diazide-5-sulfate Phonic acid ester-paracresol ester etc. are mentioned. Examples of the esterification component include 2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone, 2,2',3 ,4,4'-pentahydroxybenzophenone, phenol, 1,3-dihydroxybenzene, 1,3,5-trihydroxybenzene, bisphenol A, bisphenol F, bisphenol S, novolak resin, methyl gallic acid , ethyl gallate, phenyl gallate, and the like.

The blending amount is preferably 0.5 to 5.0 parts by weight based on 100 parts by weight of the solid content of the base resin.

In general, resist consists of more than 50% solvent, and its properties are to first dissolve the photosensitive material, the resin that becomes the basic skeleton, and other additives so that the resist constituents are uniformly mixed. For this, it is necessary to maintain an appropriate level of vapor pressure. In addition, an organic solvent having a boiling point of 100° C. or higher is used to maintain an appropriate amount of residual solvent in the baking process such as pre-bake and post exposure bake. can be used

As the organic solvent, propylene glycol monomethyl ether acetate (PGMEA), ethyl lactate (EL), methyl amyl ketone (MAK), propylene glycol monomethyl ether (PGME), γ-butyrolactone, etc. are each alone, Or it is used as a mixed solvent.

The organic solvent can reduce the concentration of the solids because the resist solids at least form a hard film, and a film having sufficient etching resistance can be formed.

The positive resist composition for the lift-off process of the present invention also contains, if desired, additives that are miscible, for example, an additional resin for improving the performance of the resist film, a surfactant for improving coatability, a dissolution inhibitor, a plasticizer, A stabilizer, a coloring agent, an antihalation agent, etc. can be added and contained suitably.

Hereinafter, the present invention will be specifically described by way of synthesis examples and examples. However, the following examples are only for illustrating the present invention, and the present invention is not limited by the following examples, and can be changed to other examples that are substituted and equivalent within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains.

[Synthesis Example 1]

Dissolve 2-(methacryloyloxy)ethyl acetoacetate (MA(acac)) 5g (23mmol) and methacrylic acid (MAA) 5g (58mmol) in 50 mL of tetrahydrofuran (THF) at room temperature, 35 ℃ It was homogenized by stirring for 30 minutes. After that, 0.7 g (3.6 mmol) of azobismethylbutyronitrile (2,2'-azobis(methylbutyronitrile, AMBN)) was added as an initiator in a nitrogen atmosphere and dissolved while slowly raising the temperature to 70° C. to dissolve azobismethylbutyronitrile After confirming that this was dissolved, a polymerization reaction was carried out for a predetermined time to confirm an increase in viscosity. Thereafter, the reaction solution was treated with diethyl ether to precipitate a white polymer, filtered and dried in an oven at 70° C. to obtain a polymer of Formula 3 below.

At this time, the weight average molecular weight of the obtained polymer was 4500.

[Synthesis Example 2]

In Synthesis Example 1, the polymerization reaction was controlled for the predetermined time so that the weight average molecular weight of the obtained polymer was 15000.

[Synthesis Example 3]

In Synthesis Example 1, 5 g (23 mmol) of 2-(methacryloyloxy) ethyl acetoacetate (MA (acac)) and 3.5 g (41 mmol) of methacrylic acid (MAA) were dissolved at room temperature, and polymerized for the predetermined time. The reaction was adjusted so that the obtained polymer had a weight average molecular weight of 8000.

*[Example 1]

To 100 parts by weight of the polymer of Synthesis Example 1, 200 parts by weight of propylene glycol monoethyl ether was added to dissolve the polymer, and 3 parts by weight of triphenylsulfonium trifluoromethanesulfonate was added to obtain a resist composition.

[Examples 2-3]

A resist composition was obtained in the same manner as in Example 1, except that Synthesis Examples 2 and 3 were used in Example 1.

[Test Example]

Each of the above compositions was applied on a silicon wafer by a spin coater, and pre-baked for 120 seconds on a hot plate at 170°C to form a resist film having a thickness of 2.5 µm. Then, it exposed with the projection exposure apparatus through the mask. Thereafter, the wafer was heated on a hot plate at 120° C. for 120 seconds, and then developed with a 2.4 wt% tetramethyl ammonium aqueous solution.

The obtained resist pattern did not peel all about the pattern by a 1.0 micrometer line and space, but formation was performed favorably.

The above examples were evaluated in the following manner.

1. Viscosity

A cotton wool was rubbed against the dried (pre-baked) film applied to the substrate, and the film's viscosity was evaluated.

It can be confirmed that all of the compositions according to the above Examples do not stick to the cotton wool, and thus the coating film handling workability is good.

2. Transmittance (%)

Without exposing the resist film prebaked in the above example, the silicon wafer was heated in a clean oven at 220 DEG C for 1 hour to obtain a cured film. The transmittance (%) at a wavelength of 400 nm was measured and evaluated using a spectrophotometer (150-20 double beam, manufactured by Hitachi, Ltd.). When the transmittance is less than 90%, transparency is judged to be poor.

As a result of the measurement, it can be confirmed that, when all of the compositions according to Examples have a transmittance of 95%, light is sufficiently transmitted to exhibit good photosensitivity.

3. Heat resistance (%)

In the above embodiment, the pre-baked resist film was exposed and developed through a mask having a line and space (1 to 1) pattern of 100 µm. The development time was set to 80 seconds. Then, the pattern was formed by performing 1 minute running water washing with ultrapure water, and drying after that. The pattern height (T1) after development was measured by a stylus type film thickness measuring device α-step (manufactured by KLA Denkor). Then, the pattern-formed silicon substrate was heated in a clean oven at 220 degreeC for 1 hour, and the pattern after thermosetting was obtained. In this way, the pattern height t1 after thermosetting is measured, the thermal contraction rate (%) before and behind thermosetting is computed from a following formula, and let this be heat resistance (%).

Heat resistance (%) = {(T1-t1)/T1} × 100

It can be said that the crosslinking reaction progresses, so that the value of heat resistance is large. In addition, the heat contraction which generate|occur|produced in this way is a level which does not have an influence especially on actual use.

As a result of the measurement, the heat resistance of all of the compositions according to the examples was 95%, and a strong film was obtained even after post-baking, and it became possible to obtain a pattern excellent in shape.

4. Adhesive

In the above embodiment, the composition of the present invention was spin-coated on a silicon wafer and heat-treated in a nitrogen oven at 100° C. for 15 minutes, 180° C. for 30 minutes, 230° C. for 30 minutes, and 300° C. for 40 minutes to form a resist film formed at 121° C., 2 atm. , PCT (pressure cooker test) was carried out for 100 hours, 300 hours, and 500 hours under 100 %RH conditions. Then, 100 pieces were crosscutted to 1mm X 1mm in a state in close contact with the silicon wafer, and a peel test was performed using a scotch tape. Even if the PCT treatment is carried out for a long time, the adhesive strength is better when it is kept in close contact with the wafer.

As a result of the measurement, it can be confirmed that all of the compositions according to Examples have excellent adhesive strength because pieces do not fall off by the peel test even after a PCT treatment time of 500 hours.

5. Peelability

With respect to the pattern formed in the above example, gold (Au) was deposited to a thickness of 5000 Å using a vacuum deposition apparatus, treated with an N-methylpyrrolidone solvent, and whether the resist was peeled off by observing it with an electron microscope.

As a result of the measurement, it can be confirmed that all of the compositions according to the examples serve as a resist for the lift-off process because no residue of the resist was observed and no gold peeling occurred.

Claims (5)

A positive resist composition for a lift-off process comprising 0.5 to 5.0 parts by weight of an acid generator that generates an acid upon exposure and 100 to 400 parts by weight of a solvent based on 100 parts by weight of the alkali-soluble base resin solid content,
The resist composition for a lift-off process, characterized in that the base resin is a polymer of 2-(methacryloyloxy)ethyl acetoacetate and methacrylic acid. The method of claim 1,
The polymer is prepared by polymerizing 2-(methacryloyloxy)ethyl acetoacetate (MA(acac)) and methacrylic acid (MAA) in a molar ratio of 1 to 1.5 to 2.5 using an initiator. A resist composition for a lift-off process. 3. The method of claim 2,
The resist composition for a lift-off process, characterized in that the initiator is reacted in an amount of 0.1 to 0.3 moles based on 1 mole of 2-(methacryloyloxy)ethyl acetoacetate (MA(acac)). The method of claim 1,
The resist composition for a lift-off process, characterized in that the polymer has a weight average molecular weight of 3,000 to 18,000. The method of claim 1,
The resist composition for a lift-off process, characterized in that the solvent is at least one selected from propylene glycol monomethyl ether acetate, ethyl lactate, methyl amyl ketone, propylene glycol monomethyl ether and γ-butyrolactone.