JPH0743907A - Chemically amplified resist pattern forming method - Google Patents

Abstract

(57) [Summary] [Objective] To construct a simple and highly safe pattern formation method that suppresses deterioration of resist characteristics over time due to the time between the exposure of a chemically amplified resist and the heat treatment for chemical amplification. The purpose is to A pattern forming method comprising the steps of applying a chemically amplified resist to a substrate, applying a protective film, exposing, heat treatment for chemical amplification, selectively removing the protective film, and developing the chemically amplified resist, A pattern forming method in which a protective film is applied using a solvent containing an aromatic hydrocarbon as a main component, and is selectively stripped with an alkaline aqueous solution diluted with a resist developing solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a chemically amplified resist pattern in a lithography technique.

[0002]

2. Description of the Related Art Chemically amplified resists use a strong acid (hereinafter referred to as a catalytic acid) generated by exposure as a catalyst and undergo a heat treatment after exposure (post exposure bake, hereinafter PEB).
Abbreviated) is to promote decomposition of the acid-decomposable functional group or crosslinking of the acid-crosslinkable functional group in the pattern formation reaction. Since the catalytic acid is easily deactivated by an impurity component mainly composed of a basic compound contained in the air, its resist characteristics are significantly deteriorated depending on the time between exposure and PEB (time delay effect, hereinafter referred to as TED). Is a well-known fact. As a method for improving this TED, a method of performing from exposure to PEB in an atmosphere in which the impurity component is removed (for example, S.
A. MacDonald et al., SPIE, Volume 1466, page 2, 1991.
), A method of applying a protective film on the film of chemically amplified resist (for example, Oikawa et al., IEICE Tech. SDM 92-157, 1993),
Etc. are known. However, in the former method of cleaning the atmosphere, the equipment is huge and expensive, and there is a problem in stable operation and maintenance of the equipment over a long period of time. In this respect, the latter using a protective film is more advantageous. The protective film acts as a blocking film that prevents the resist from directly contacting the atmosphere, and unless a basic component that deactivates the catalytic acid is included in the stoichiometric composition or as an impurity, many organic high The molecule shows the function of improving TED. For example, polystyrene, poly (α-methylstyrene), saturated aliphatic polymer and the like show an excellent TED improving effect. However, with these materials, a large amount of organic solvent is used in the peeling process, so there is a high risk from the viewpoint of disaster prevention, and the treatment of organic waste liquid is complicated, and further, the process steps are complicated. Had. From this point of view, it is safer to use a water-soluble material, and since it can be peeled off by an ordinary photoresist developing apparatus, it has a feature that it is simple in terms of process. However, it has been clarified by our previous studies that polyacrylic acid or polyvinyl alcohol deteriorates the pattern forming ability of the chemically amplified resist due to the use of water as a coating solvent. This effect is due to 2-ethoxyethyl acetate (ECA)
Although it is still relatively small for chemically amplified resist coated with as a solvent, it became noticeable when propylene glycol monomethyl ether acetate (PGMEA) or ethyl lactate, which are considered as safer solvents, were used. . ECA is becoming obsolete due to its harmful effects on the human body. From the above, T using the conventional protective film
The ED improvement method was insufficient.

[0003]

SUMMARY OF THE INVENTION The present invention has been proposed in order to overcome the drawbacks caused by the conventional protective film material, and the purpose thereof is to provide a process which does not impair the resist characteristics and is highly safe. To provide a method for forming a chemically amplified resist pattern capable of constructing.

[0004]

In order to achieve the above object, the present invention applies a chemically amplified resist to a substrate, applies an organic film on the resist, exposes it, and heat-treats it for chemical amplification. A pattern forming method including the steps of selectively peeling the organic film and developing the resist with a resist developer, wherein an organic solvent containing an aromatic hydrocarbon as a main component is used as a solvent for the organic film, and The subject of the invention is a method for forming a pattern of a chemically amplified resist, characterized in that an alkaline aqueous solution having a pH lower than that of the resist developing solution is used as a stripping solution for the organic film. In other words, the present invention is a pattern including the steps of coating a substrate with a chemically amplified resist, coating a protective film, exposing, heat treatment for chemical amplification, selectively removing the protective film, and developing the chemically amplified resist. In the forming method, the protective film is applied using a solvent containing an aromatic hydrocarbon as a main component, and is selectively peeled off with an alkaline aqueous solution diluted with a developing solution. .

As a result of intensive studies, we found that a copolymer of styrene and partially esterified maleic acid was dissolved in a solvent containing an aromatic hydrocarbon as a main component, and the solution contained polyhydroxystyrene or a novolac resin as a main component. It has been found that the chemically amplified resist can be coated without damaging the resist and can be stripped in a short time by using an alkaline aqueous solution diluted with a developing solution of the resist. The meaning of dilute in this case means that the hydroxyl ion concentration in the solution is low, that the pH is low, and that the pH is close to neutral.
By verifying using this material, the usefulness of the present invention can be clarified, and the present invention has been completed.

What is important when a protective film is further applied onto the resist is that the resist and the protective film do not intermix. For this reason, it is necessary to use a solvent that does not dissolve the resist as a coating solvent for the protective film. Polyhydroxystyrene and novolac resin,
Alternatively, a chemically amplified resist whose main component is a polymer chemically modified by introducing a substituent into these is generally insoluble in aromatic hydrocarbons such as toluene and xylene. Therefore, the requirement of coating with a solvent containing an aromatic hydrocarbon as a main component in the present invention brings out the characteristic that intermixing does not occur in a normal chemically amplified resist. It is difficult to strictly define the ratio of aromatic hydrocarbons because intermixing is greatly affected not only by the solvent but also by the resist composition, but at least 85 wt% or more of the solvent mixture ratio is aromatic hydrocarbons. is necessary.

On the other hand, the requirement of peeling the protective film with an aqueous alkali solution in the present invention is useful in simplifying the process and in safety in disaster prevention. At this time, it is necessary for the pattern formation that the protective film has a solubility much better than that of the resist and that the protective film can be selectively peeled off without attacking the resist. If selective peeling cannot be performed, it may cause an error in the pattern dimension, or in some cases, the pattern cannot be formed.

[0008]

In the present invention, since the protective film can be peeled off with an alkaline aqueous solution having a low pH, the peeling step can be carried out simply and safely. Moreover, since the protective film can be applied with an organic solvent,
The TED of the chemically amplified resist is improved over the conventional water-soluble protective film.

[0009]

EXAMPLES Next, examples of the present invention will be described. [Example 1] Using PGMEA as a solvent, a three-component chemically amplified positive resist containing polyhydroxystyrene as a main component was applied to a Si substrate and heat-treated at 100 ° C for 120 seconds. At this time, the resist film thickness was 1.00 μm. Structural formula

[0010]

[Chemical 1]

A solution of 7 parts by weight of a random copolymer having a weight average molecular weight of about 2000, 80 parts by weight of xylene, and 10 parts by weight of ethyl lactate is coated on the resist film and then at 60 ° C. at 85 ° C. Heat treated for seconds. The resist was not attacked by the application of this organic film. 30 with soft X-rays
from mJ / cm ² up to 70mJ / cm ² 5mJ / cm ²
The exposure was changed by changing the exposure amount. 1 at 85 ° C after exposure
Heat treatment was performed for 20 seconds. The tetramethylammonium hydroxide (TMAH) aqueous solution having a pH of about 12 and 0.1N was used for 40 seconds to dissolve the copolymer by the paddle method.
It was washed with water for 2 seconds. Next, the pH is higher than 0.1 N, and the pH =
The resist was developed for 60 seconds with a 0.2 N TMAH aqueous solution of about 12.5 and washed with water. PE within 1 hour after exposure
When B was performed, the resist sensitivity was constant at 40 mJ / cm ² .

Comparative Example 1 Poly (α-methylstyrene) was applied in place of the copolymer in Example 1 using xylene as a solvent, and after PEB, peeling was performed using xylene. The resist sensitivity obtained by development is 40 mJ / cm ^2.
Thus, there was no change from the sensitivity obtained in Example 1. [Comparative Example 2] In Example 1, when polyacrylic acid was applied as a solvent in place of the copolymer and water was used as a solvent and peeled off with water after PEB, a resist was obtained even when PEB was performed within 10 minutes after exposure. The sensitivity was 50 mJ / cm ² , which was 25% lower than that of Example 1.

Example 2 The copolymer of Example 1 was coated on the resist using a mixed solvent of 80 wt% xylene and 20 wt% ethyl acetate. At this time, when light was applied to the substrate in the vertical direction, scattered light was observed from the interface between the resist and the copolymer, and it was found that the resist surface was slightly rough. However, the film thickness of the resist was reduced by only 50 nm. The resist sensitivity is
It was 35 mJ / cm ² , and the sensitivity was improved as compared with the case of Example 1. [Example 3] In Example 1, as a solvent for the copolymer, xylene was 85 wt%, ethyl acetate was 15 wt%,
A mixed solvent consisting of The resist was not attacked by applying this organic film. [Example 4] In Example 1, as a solvent for the copolymer, 80 parts by weight of toluene, 10 parts by weight of PGMEA,
Was used. This organic film could be applied without attacking the resist, and the resist characteristics were in agreement with those of Example 1. [Example 5] In Example 1, as the copolymer, a structural formula was used.

[0014]

[Chemical 2]

The random copolymer of was used. This organic film could be applied without attacking the resist, and the resist characteristics were in agreement with those of Example 1.

[0016]

According to the present invention, a pattern formation process using a chemically amplified resist can be simply and safely constructed, and the characteristics of the resist can be sufficiently exhibited. The contribution is very large.

Front page continuation (72) Inventor Kokichi 1-16 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A substrate is coated with a chemically amplified resist, an organic film is coated on the resist, exposed, and heat-treated for chemical amplification to selectively peel off the organic film to resist the resist. In a pattern forming method including a step of developing with a developing solution, an organic solvent containing an aromatic hydrocarbon as a main component is used as a solvent for the organic film, and an alkaline aqueous solution having a lower pH than the alkaline aqueous solution for the resist developing solution is used. A method for patterning a chemically amplified resist, which is used as a stripping solution for the organic film.