JPH087443B2 - High resolution positive type radiation sensitive resist - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a positive-type high-polymerization agent containing a monodisperse copolymer of a monomer represented by the general formula (I) and a crosslinkable α-cyanoacrylic acid ester as a main component. It relates to a high-sensitivity, high-resolution, radiation-sensitive resist.

[Technical background of the invention]

Electron beam direct writing, X-ray lithography, and focused ion beam exposure technology have been proposed as lithography technology at the level of 0.5 μm or less, which is the limit of optical exposure of semiconductor integrated circuits, and they are already at the stage of realization. However, the development of a resist that can cope with this is delayed. By irradiating these resist materials with radiation, a cross-linking reaction occurs, and by irradiating with a negative type that becomes insoluble in the developing solution, the main polymer of the resist undergoes a main chain splitting reaction to lower the molecular weight. Therefore, there is a positive type in which the resist is easily dissolved in the developing solution and the resist in the irradiation region is removed.

The features of the negative resist are high sensitivity and excellent etching resistance, but low resolution.

On the other hand, the positive resist is characterized by high resolution but poor etching resistance and sensitivity.

Recently, the industry's desire for high integration of semiconductor integrated circuits has been escalated more and more, and negative resists with high sensitivity and excellent productivity have been forced to recede because of their low resolution. Mold resists have become mainstream.

[Prior art and its problems]

Polymethylmethacrylate (P-MMA) is a typical base polymer for positive resist, and its resolution is 0.3-
Although it is said to be 0.5 μm, the sensitivity to electron beam is extremely low at 5 × 10 ⁻⁵ C / cm ^2, and the etching resistance is inferior to that of the negative resist, which is far from a practical resist.

Most of the conventionally developed resists have poor sensitivity and etching resistance compared to the resolution, and lack of balance in performance, so they are being studied intensively.

Many proposed for improving these sensitivity,
This is due to the introduction of electron withdrawing groups such as Cl, Br, F, S, O, N. As an example, polyhexafluorobutyl methacrylate, polytrichloroethyl methacrylate, polybutene-1 sulfone, polytrifluoroethyl α -Chloroacrylate, novolac-poly-2-methylpentene-1 sulfone mixture and the like are available, but there are few cases where the sensitivity can be improved without lowering the dry etching resistance. On the other hand, it has been proposed to improve the etching resistance by introducing a benzene ring into the side chain of the resist base polymer, introducing a cross-linking group, introducing an alkyl group with a large molecular weight, and adding a radical scavenger, but this leads to a decrease in sensitivity. There are many cases.

To improve resolution, use styrene, P- for negative resist.
It is reported that dimethylaminomethylstyrene, isoprene and the like are used to synthesize a monodisperse polymer by using an anionic polymerization initiator such as alkyllithium and the resolution is remarkably improved.

[Object of the Invention]

The present invention comprises, for example, etching resistance by cross-linking one or more of the monomer group represented by the general formula (I) described above and a monodisperse copolymer composed of a crosslinkable α-cyanoacrylate ester. Excellent 64 Mbit D-RA
It is intended to provide a resist composition for a large-scale integrated circuit of M or later.

[Structure of Invention]

The present invention relates to an α-cyanoacrylic acid ester having a crosslinking group in the molecule and a compound of the general formula (I) (However, X in the formula is CN, NO ₂ , COOR, Y is CN, H, COOR, R
Is characterized in that a composition containing a monodisperse copolymer of monomers of an alkyl group and a halogenated alkyl group as a main component is crosslinked before or after irradiation with radiation to improve dry etching resistance.

The α- / cyanoacrylic acid ester and the polymer of the general formula (I) have electron withdrawing groups CN, N, O and Cl, in the molecule.
It possesses halogen elements such as F and Br and has excellent sensitivity to radiation, and the copolymers composed of these elements can increase the sensitivity due to the synergistic effect. Not only is extremely easily degradable, but also forms an excellent monodisperse copolymer, so that the resolution can be greatly improved. Further, the etching resistance can be improved by adopting an α-cyanoacrylic acid ester having a crosslinkable group in the 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.

However, R in the formula is a crosslinkable group such as an alkoxyalkyl group, a hydroxyalkyl group, an allyl group and an alkynyl group, and specifically, 2-methoxyethyl α-cyanoacrylate, α-cyanoacrylic acid 2 -Hydroxyethyl, propargyl α-cyanoacrylate, allyl α-cyanoacrylate and the like.

Corresponding monomers of general formula (I) are, for example:
Examples include vinylidene cyanide, nitroethylene, and diethyl methylene malonate.

These monomers may be those obtained by a usual synthetic method, and the anionic polymerization inhibitor may be left mixed therein.

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

〔The invention's effect〕

The positive resist material according to the present invention is 64 Mbit D-
It is suitable for electron beam and ultra-high-density engraving in the X-ray lithography process when manufacturing large-scale integrated circuits of semiconductors after RAM, and guarantees a large improvement in processing accuracy and a wide latitude circuit design, and its radiation. The extremely high sensitivity to X-ray greatly contributes to high productivity and cost reduction in the X-ray lithography process. Examples of the present invention will be shown below, but electron beams are also used for soft X-rays (wavelengths 4 to 10
Å) also has the same chemical action on the substance, and the sensitivity of the resist to electron beam and X-ray has a proportional relationship (eg 10 ⁻⁷ C / cm ² = 10 mJ / cm ² ).
ternational Conf.Microlithography, Paris, July, 261
(1977) and the like, the result obtained by electron beam irradiation is used as an example in order to avoid complication. Needless to say, the present invention is not limited to these embodiments.

 Hereinafter, the present invention will be further described with reference to examples.

Example 1 700 ml of an acetone solution containing 5 × 10 ⁻⁵ mol of anionic polymerization initiator thiosemicarbazide was introduced into the flask, and the inside of the flask was cooled to −60 ° C. While sufficiently stirring the system, 100 ml of an acetone solution containing 0.01 mol of α-cyanoacrylate propargyl containing 50 ppm of anionic polymerization inhibitor SO ₂ was gradually added to the reaction while maintaining the system temperature at -60 ° C or lower. Then, to the living polymer obtained, 100 ml of an acetone solution containing 0.09 mol of vinylidene cyanide containing 50 ppm of an anionic polymerization inhibitor SO ₂ is added with sufficient stirring while keeping the system temperature at −60 ° C. or lower to carry out the copolymerization reaction. Proceed,
The reaction was stopped by adding an anionic polymerization terminator.

This copolymer was purified by the reprecipitation method, and the molecular weight was measured by gel permeation chromatography (GPC) -light scattering method. The molecular weight was 207,000, and the dispersity (w / n) was 1.05. It was

A resist was prepared by adding a thermal crosslinking agent to a 5 wt% cyclohexanone solution of this copolymer. This resist was coated on a 0.5 μm thick thermally-oxidized silicon layer by a spin coating method to obtain a copolymer film having a thickness of 0.43 μm. 150 this
After heat treatment and thermal crosslinking for 30 minutes at ℃, acceleration voltage 10KV, 4 × 10 ^-7 C /
The resist film surface was irradiated with an electron beam of cm ² according to a predetermined pattern. Then, this was taken out into the air, and developed by immersing it in a developing solution of cyclohexanone and methyl isobutyl ketone of 1: 2 at 25 ° C. for 3 minutes, rinsed with isopropyl alcohol and dried. Then, heat treatment (post-baking) was performed at 130 ° C. for 30 minutes. This resist film is CF ₄
- a reactive ion etching _{apparatus, CF 4 + 5% O 2} 10SC
Etching under the conditions of CM 60mtorr, applied power 13.56MHz, 150W, the etching rate of P-MMA is 750Å / m.
In contrast to this, the etching rate of this resist film was 480 Å / min, which was superior to P-MMA. The scanning electron microscope (SEM) observation of the etching result by the reactive ion etching system (R1E) of this system confirmed the formation of a linear pattern of 0.3 μm.

Note: The molecular weights of polymers in Examples and Comparative Examples were 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 the low temperature anionic polymerization method according to Example 1, and its molecular weight was 189,000 and its degree of dispersion ( w / n) = 1.04. This 5 wt% cyclohexanone solution was prepared, and a thermal crosslinking agent was added thereto to prepare a resist. This resist is applied by spin coating method to 0.
It was applied on a thermally oxidized silicon layer having a thickness of 5 μm to obtain a copolymer film having a thickness of 0.4 μm. According to Example 1, this was subjected to thermal crosslinking, electron beam irradiation, development, rinsing, drying, and post-baking. When this resist film was etched under the same conditions as in Example 1, the etching rate of this resist film was
At 420 Å / min, it 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 0.3 μm linear pattern was sharply formed.

Example 3 A monodisperse copolymer of allyl α-cyanoacrylate and diethyl methylenemalonate in a molar ratio of 1: 9 was obtained by the low temperature anionic polymerization method according to Example 1, and its molecular weight was 344,000.
The dispersity (w / n) was 1.05.

A 5 wt% cyclohexanone solution of this polymer was prepared, and an ultraviolet crosslinking agent was added thereto to prepare a resist. This resist was applied on a thermally oxidized silicon layer having a thickness of 0.5 μm by a spin coating method to obtain a copolymer film having a thickness of 0.54 μm. This was prebaked, crosslinked with ultraviolet rays, irradiated with an electron beam, developed, rinsed, dried, and postbaked according to Example 1.

When this resist film was etched under the conditions of Example 1, the etching rate of this resist film was 440 Å / min.
, The resistance was superior to that of P-MMA.

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

Example 4 A monodisperse copolymer of 2-hydroxyethyl α-cyanoacrylate and dimethyl methylenemalonate in a molar ratio of 3: 7 was obtained by the low temperature anionic polymerization method according to Example 1, and its molecular weight was 351,000. The dispersity (w / n) was 1.04. This 5 wt% cyclohexanone solution was prepared, and a thermal crosslinking agent was added thereto to prepare a resist. This resist was applied on the thermally oxidized silicon layer having a thickness of 0.5 μm by a spin coating method to obtain a copolymer film having a thickness of 0.56 μm. This film 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 conditions of Example 1, the etching rate of this resist film was 470 Å / min.
, The resistance was superior to that of P-MMA. The resolution of this resist was 0.3 μm, and a sharp pattern edge was confirmed by SEM observation.

Comparative Example 1 A monodisperse copolymer of trifluoroethyl α-cyanoacrylate and diethyl methylene malonate in a molar ratio of 6: 4 was obtained by the low temperature anionic polymerization method according to Example 1, and its molecular weight was 361,000. The dispersity (w / n) was 1.04. This 5 wt% cyclohexanone solution was prepared and applied by spin coating onto a 0.5 μm thick thermally oxidized silicon layer to give 0.54
A copolymer film having a thickness of μm was obtained. This was pre-baked at 130 ° C. for 30 minutes, and electron beam irradiation, development, rinsing and post-baking were performed according to Example 1. When this resist film was etched, the etching rate was 885Å / min and P
-Lower resistance than MMA.

When the patterning result of the silicon oxide layer by RIE of this system was observed by SEM, the formation of a 0.3 μm sharp linear pattern was confirmed.

Comparative Example 2 5 parts of vinylidene cyanide, 10 parts of α-cyanoacrylate, 3 parts of acetic acid and 0.1 part of azobisisobutyronitrile were charged in a glass sealed tube and polymerized in nitrogen at 50 ° C. for 15 hours.
Pour this into ethyl ether to precipitate the polymer,
White powdery non-monodisperse copolymer 12.5 after vacuum drying at 40 ℃
I got a part. The molecular weight of this copolymer was 293,000.

A 5 wt% cyclohexane solution of this copolymer was prepared and applied onto a 0.5 μm thick thermally oxidized silicon layer by a spin coating method to obtain a 0.51 μm thick copolymer film. After heating (pre-baking) this at 130 ° C. for 30 minutes, electron beam irradiation, development, rinsing, drying, and post-baking were carried out according to Example 1. When this resist film was etched according to Example 1, the etching rate of this resist was 85.
At 0Å / min, the resistance was lower than that of P-MMA as in Example 1. Further, etching by RIE and observation by SEM confirmed the formation of a 0.5 μm pattern.

As described above, from Examples 1 to 4 and Comparative Examples 1 and 2, the introduction of the monodisperse polymer, the crosslinkable α-cyanoacrylic acid ester, and the sensitizing monomer (general formula (I)) resulted in resolution, dry etching resistance and sensitivity. It is clear that there is a critical effect on the improvement of

Claims (1)

[Claims] 1. A general formula (I) (However, in the formula, X is CN, NO ₂ , COOR, Y is CN, H, COO.
R, R is an alkyl group or a halogenated alkyl group) and is obtained by reacting one or more kinds of monomers represented by the following formula with a crosslinkable α-cyanoacrylic acid ester having a crosslinkable group in its side chain. High-resolution positive-working radiation-sensitive resist based on a monodisperse copolymer with a dispersity (Mw / Mn) of 1.05 or less.