JPS63271253A - Positive type radiation sensitive resist having high resolution - Google Patents

Abstract

PURPOSE:To obtain the titled resist having the excellent dry etching resistance and available for a large scale integrated circuit by comprising a monodispersive copolymer obtd. by allowing one or more kinds of specified monomer groups to react with a crosslinkable alpha-cyanoacrylate, as a main component. CONSTITUTION:The composition contains the monodispersive copolymer of the alpha-cyanoacrylate having a crosslinking group in a molecule and the monomer shown by the formula as the main component, and said composition is crosslinked before or after irradiating a radiation to improve a dry etching resistance. In the formula, X is CN, NO2 or COOR, Y is CN, H or COOR, R is alkyl group or a halogenated alkyl group. Thus, the resolution or the dry etching resistance are improved, and the titled resist is suitable for super high density engraving in an electron beam or a X ray lithography step at the time of forming the large scale integrated circuit of a D-RAM semiconductor of larger than 64 megabit.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to a positive polymer whose main ingredient is a monodisperse copolymer of a heptamine represented by the general formula (I) and a crosslinkable α-cyanoacrylic acid ester. It concerns high-sensitivity, high-resolution, radiation-sensitive resists.

[Technical background of the invention]

0.5μ- which is the limit of optical exposure of semiconductor integrated circuits
Exposure technologies using electron beam direct FI imaging, X-ray lithography, and focused ion beams have been proposed as lithography technologies at the following level, and are already reaching the stage of realization, but the development of resists that can support these technologies has been delayed. ing. When these resist materials are irradiated with radiation, a cross-linking reaction occurs, making them insoluble in the developer.By irradiation with radiation, the main polymer of the resist causes a main chain splitting reaction, resulting in a lower molecular weight. As a result, there is a positive type that is easily dissolved in a developer and the resist in the irradiated area is removed.

Negative resists are characterized by high sensitivity and excellent etching resistance, but low resolution.

In contrast, positive resists have high resolution, but
The etching resistance and sensitivity are poor.

Recently, the industrial world's desire for higher integration of semiconductor integrated circuits has been increasing, and negative resists, which have high sensitivity and excellent productivity, have been forced into decline due to their low resolution, and positive resists have been forced to decline. Type resists are becoming mainstream.

[Prior art and its problems]

Polymethyl methacrylate (P-MMA) is a typical main polymer for positive resists, and its resolution is 0.
Although it is said to have a resistance of 3 to 0.5μ, its sensitivity to electron beams is extremely low at 5×10-'C/cj, and its etching resistance is also inferior to that of negative resists, making it far from a practical resist. .

Positive resists are being intensively studied because most of the conventionally developed resists have inferior sensitivity and etching resistance compared to their resolution, and lack a balance of performance.

Many of the proposals for improving these sensitivities are based on C
1, by the introduction of electron-withdrawing groups such as Br, F, S, O, N, etc. - Examples include polyhexafluorobutyl methacrylate, polytrichloroethyl methacrylate, polybutene-1 sulfone, polytrifluoroethyl α-chloroacrylate, novolac-poly2
-Methylpentene-l sulfone mixtures, etc., but there are few cases where sensitivity can be improved without reducing dry etching resistance.On the other hand, to improve etching resistance, benzene is added to the side chains of the resist main polymer. Introduction of a ring, introduction of a crosslinking group, introduction of an alkyl group with a large molecular weight, and addition of a radical scavenger have been proposed, but these often result in a decrease in sensitivity.

Styrene, P-
It has been reported that monodisperse polymers are synthesized from dimethylaminomethylstyrene, isoprene, etc. using anionic polymerization initiators such as alkyl lithium, and the resolution is significantly improved.

[Purpose of the invention]

The present invention can improve etching resistance, for example, by crosslinking a monodisperse copolymer made of a crosslinkable α-cyanoacrylic acid ester with one or more of the group of monomers represented by the general formula (I) described above. Excellent 64 megapix) D-R
The present invention aims to provide a resist composition for large-scale integrated circuits after AM.

[Structure of the invention]

The present invention is α-cyano having a crosslinking group in the molecule (wherein, X is CM, Hog, C0OR, Y is C
N.

H, COOR, R are alkyl groups and halogenated alkyl groups) The composition is crosslinked before or after radiation irradiation to improve dry etching resistance.

α-Cyanoacrylic acid ester and the polymer of the general formula (r) have electron-withdrawing groups CN, N, 0 and halogen elements such as CI, F, and Or in their molecules, and have excellent sensitivity to radiation. The copolymers composed of these are capable of increasing sensitivity due to the synergistic effect. Furthermore, these copolymers are not only extremely easy to decompose, but also have excellent monodisperse copolymer properties. By forming a fusion, the resolution can be greatly improved. Furthermore, the etching resistance can be improved by employing an α-cyanoacrylic acid ester having a crosslinkable group in its side chain.

The α-cyanoacrylic acid ester having a crosslinkable group in the side chain used in the present invention is represented by the following formula.

CN CH2= C-C0OR However, R in the formula is a crosslinkable group such as an alkoxyalkyl group, a hydroxyalkyl group, an allyl group, an alkynyl group, and specifically, 2-methoxyethyl α-cyanoacrylate, These include 2-hydroxyethyl α-cyanoacrylate, propargyl α-cyanoacrylate, and allyl α-cyanoacrylate.

Corresponding monomers of general formula (I) are, for example, vinylidene cyanide, nitroethylene, diethyl methylenemalonate, and the like.

These monomers may be obtained by conventional synthesis methods, and may be mixed with an anionic polymerization inhibitor.

The above copolymers usually have a molecular weight of 20,000 to 2,000,000, but preferably 200,000 to 1,000,000.

〔Effect of the invention〕

The positive resist material according to the present invention has a 64 Mbit D-
It is suitable for ultra-high-density engraving such as the electron beam and XL lithography process used in the manufacturing of semiconductor large-scale integrated circuits after RAM, and guarantees a significant improvement in processing accuracy and circuit design with a wide latitude, as well as eliminating radiation. The extremely high sensitivity to X-ray lithography has a significant effect on high productivity and cost reduction in one process of X-ray lithography. Examples of the present invention will be shown below, but electron beams can also be used for soft
Humans) have the same chemical effect on substances, and the sensitivity of a resist to electron beams and sensitivity to X-rays are in a proportional relationship (
For example 10-'C/cj = 10a+J/cd
) is in Proc International
Conf, Microlithography+
Paris, July+261 (I977), etc., so in order to avoid complications, the results of electron beam irradiation will be used as examples.

It goes without saying that the present invention is not limited to these examples.

The present invention will be further explained below with reference to Examples.

Example 1 700 mj containing 5xto-' moles of anionic polymerization initiator thiosemicarbazide! An acetone solution was introduced into the flask, and the inside of the flask was cooled to -60°C.

While stirring the system thoroughly, add the anionic polymerization inhibitor S.
100 ml of acetone solution containing 0.01 mol of propargyl α-cyanoacrylate containing 50 ppm of Og was gradually added and reacted while keeping the system temperature below -60°C, and the resulting Ping polymer was inhibited from anionic polymerization. Vinylidene cyanide 0.09 containing 50pp+I agent SO1
100ml of acetone solution containing mol.
The copolymerization reaction was carried out by adding the mixture while keeping the temperature at 60° C. or lower and stirring thoroughly, and the anionic polymerization terminator was added to terminate the reaction.

This copolymer was purified by reprecipitation method and gel permini
When the molecular weight was measured by silane chromatography (GPC)-light scattering method, the molecular weight was 20.7 million, and the degree of dispersion (L/Mn) was 1.05.

A resist was prepared by adding a thermal crosslinking agent to a 5% by weight cyclohexanone solution of this copolymer. This resist was coated on a thermally oxidized silicon layer with a thickness of 0.5 .mu.m by a spin coating method to obtain a copolymer film with a thickness of 0.43 .mu.m. This was heat-treated at 150°C for 30 minutes, and after thermal crosslinking, the acceleration voltage was 10
KV, 4 X l O-'C/c+1 electron beams were irradiated onto the resist film surface according to a predetermined pattern. continue,
This was taken out into the atmosphere and developed by immersing it in a 1=2 developer solution of cyclohexanone and methyl isobutyl ketone at 25°C for 3 minutes, rinsing with isopropyl alcohol and drying.Then, it was heated at 130°C for 30 minutes. This treated (post-baked) resist film was etched with CP4+5% Ox IO using a CF4-reactive ion etching device.
SCCM 60mTorr, applied power 13.56
When etched under the conditions of MHz and 150H,
While the etching rate of P-MMA was 750 people/sin, the etching rate of this resist film was 4.
It showed better tolerance than P-MMA at 80 people/1n.

In addition, this system's reactive ion etching apparatus (RIE)
As a result of scanning electron microscopy (SEM) observation of the etching results, it was confirmed that a linear pattern with a diameter of 0.3 μm was formed.

Note: The molecular weights of the polymers in Examples and Comparative Examples were all measured by GPC-light scattering method.

Example 2 A monodisperse copolymer of propargyl α-cyanoacrylate and nitroethylene in a molar ratio of 1:9 was obtained by a low-temperature anionic polymerization method according to Example 1, and its molecular weight was 189,000.
The degree of dispersion (Mw/Mn) was 1.04. This 5% by weight cyclohexanone solution was prepared, and a thermal crosslinking agent was added thereto to prepare a resist. This resist was applied onto a thermally oxidized silicon layer with a thickness of 0.5 .mu.m by a spin coating method to obtain a copolymer film with a thickness of 0.4 .mu.m. This was subjected to thermal crosslinking, electron beam irradiation, development, rinsing, drying, and post-baking according to Example 1. When this resist film was etched under the same conditions as in Example 1, the etching rate of this resist film was 420 people/sin, which showed better resistance than P-MMA. When the result of patterning the silicon oxide layer by RIE of this system was observed by SEM, it was confirmed that a sharp linear pattern of 0.3 μ- was formed.

Example 3 A monodisperse copolymer of allyl α-cyanoacrylate and diethyl methylenemalonate at a molar ratio of 1:9 was obtained by a low-temperature anionic polymerization method according to Example 1, and its molecular weight was 34.4.
The dispersity (Mw/Mn) was -1.05.

Make a 5% by weight solution of this polymer in cyclohexanone,
A resist was prepared by adding an ultraviolet crosslinking agent to this. This resist was coated on a thermally oxidized silicon layer with a thickness of 0.5 μm by a spin coating method to obtain a copolymer film with a thickness of 0.54 μm. This was prebaked, crosslinked with ultraviolet rays, irradiated with an electron beam, developed, rinsed, dried, and postbaked in accordance with Example 1.

When this resist film was etched under the conditions of Example 1, the etching rate of this resist film was 440 people/s.
In, it showed better resistance than P-MMA.

As a result of patterning the silicon oxide layer by RIH in this system, it was observed by SEM that a linear pattern of 0.3β was formed in good condition as in Example 1.

Example 4 A monodisperse copolymer of 2-hydroxyethyl α-cyanoacrylate and dimethyl methylenemalonate with a molar ratio of 3 was obtained by a low-temperature anionic polymerization method according to Example 1, and its molecular weight was 351,000. , dispersion degree (Mw/Mn) = 1.0
It was 4. This 5% by weight cyclohexanone solution was prepared, and a thermal crosslinking agent was added thereto to prepare a resist. This resist was coated on a thermally oxidized silicon layer with a thickness of 0.5 μm by a spin coating method to obtain a copolymer film with a thickness of 0.56 μm.

This film was subjected to thermal crosslinking, electron beam irradiation, development, and
Rinsing, drying, and post-bake were performed.

When this resist film was etched under the conditions of Example 1, the etching rate of this resist film was 470 people/w.
In, it showed better resistance than P-MMA. Note that the resolution of this resist is 0.3 μ-, and according to SEM observation, sharp pattern edges are observed with i! ! ! It was done.

Comparative Example 1 A monodisperse copolymer of trifluoroethyl α-cyanoacrylate and diethyl methylenemalonate in a molar ratio of 6:4 was obtained by a low-temperature anionic polymerization method according to Example 1, but its molecular weight was 36.1. 10,000, degree of dispersion (Mw/Mn) = 1.04
Met. Make this 5% by weight cyclohexanone solution,
It was coated on a thermally oxidized silicon layer with a thickness of 0.5 mm by a spin coating method to obtain a copolymerized film with a thickness of 0.54 μm. This was prebaked at 130° C. for 30 minutes, and subjected to electron beam irradiation, development, rinsing, and postbaking in the same manner as in Example 1.

When this resist film was etched, the etching rate was 885 people/sin, which showed lower resistance than P-MMA.

When the result of patterning the silicon oxide layer by RIH in this system was observed by SEM, it was confirmed that a sharp linear pattern with an error of 0.3 μm was formed.

Comparative Example 2 5 parts of vinylidene cyanide, 10 parts of ethyl α-cyanoacrylate, 3 parts of acetic acid, 0.1 part of azobisisobutyronitrile
A portion of the mixture was placed in a glass sealed tube and polymerized at 50° C. for 15 hours in nitrogen. This was poured into ethyl ether to precipitate the polymer, which was vacuum dried at 40"C to obtain 12.5 parts of a non-monodisperse copolymer in the form of a white powder. The molecular weight of this copolymer was 2.
It was 9.3 million.

A 5% by weight cyclohexane solution of this copolymer was made,
A copolymer film with a thickness of 0.51 tIm was obtained by coating on a silicon monoxide layer with a thickness of 0.5 μm by a spin coating method.

After heating (pre-baking) at 130"C for 130 minutes, electron beam irradiation, development, rinsing, drying, and post-baking were performed according to Example 1. When this resist film was etched according to Example 1, this The resist etching rate was 850 people/min, the same as in Example 1.
- showed lower resistance than MMA. In addition, when etched with RfH and observed with SEM, it was found that 0.5 μ-
The formation of a pattern was confirmed.

As described above, from Examples 1 to 4 and Comparative Example 1.2, the introduction of the monodisperse polymer, crosslinkable α-cyanoacrylic acid ester, and sensitizing monomer (general formula (I)) improves resolution, dry etching resistance, and sensitivity. It is clear that it has a critical effect on improving.

Claims (1)

[Claims] General formula (I) ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (However, in the formula, A high-resolution positive-working radiation-sensitive resist whose main ingredient is a monodisperse copolymer obtained by reacting one or more of the monomer group represented by (alkyl group) with a crosslinkable α-cyanoacrylic acid ester.