JPH087441B2 - Positive type high sensitivity radiation sensitive resist - Google Patents

Description

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

[Technical background of the invention]

For semiconductor integrated circuits, techniques such as electron beam direct writing and X-ray lithography have been developed as a lithography technique at a level of 0.5 μm or less, which is the limit of optical exposure, but the development of a resist suitable for this is also urgent. It is in stages.

When these resist materials are exposed to radiation, they undergo a cross-linking reaction and become insoluble in the developing solution.When exposed to radiation, the main polymer of the resist undergoes main chain splitting and becomes readily soluble in the developing solution. There is a positive type resist.

The characteristics 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 is inferior to the negative resist in sensitivity and etching resistance.

Since the demand for higher integration of semiconductor integrated circuits in the industry has become stronger and stronger recently, negative resists with high sensitivity and excellent productivity are also forced to retreat because of their low resolution. However, it is difficult to put a positive resist having excellent resolution into practical use unless the problems of low sensitivity and lack of etching resistance are solved.

[Problems of conventional technology]

Polymethylmethacrylate (P-MMA) is a typical main component for positive resist, and its resolution is 0.3-0.5.
Excellent at μm, but sensitivity to electron beam is 5 × 10
^It is markedly inferior to ^-5 C / cm ² , has low etching resistance, and is far from a practical resist. This sensitivity to radiation and etching resistance are contradictory functions, and it is difficult to achieve both at the same time. In order to improve the sensitivity of the resist, a method of introducing an electron withdrawing group such as Cl, F, Br, S, O, N is generally tried, and a base polymer such as polyhexafluorobutyl methacrylate or polytrichloroethyl methacrylate is proposed. However, the sensitivity was improved, but the reduction in etching resistance was unavoidable. In order to improve the etching resistance, introduction of a benzene ring into the side chain, introduction of an alkyl group having a large molecular weight, introduction of a cross-linking group, addition of a radical scavenger, etc. have been proposed. Very few resists have the three major characteristics of sensitivity and etching resistance.

α-Cyanoacrylic acid ester has an electron-withdrawing group CN group in its molecule and has excellent sensitivity to radiation,
Excellent resolution but poor etching resistance. Improving etching resistance is an immediate goal, but if sensitivity can be further improved in addition to this, productivity will be improved.

[Object of the Invention]

INDUSTRIAL APPLICABILITY The present invention provides a compound represented by the general formula (I) which has extremely excellent sensitivity characteristics
Copolymerization of monomer and crosslinkable α-cyanoacrylic acid ester to improve sensitivity characteristics and crosslink to improve etching resistance, resulting in high productivity, for example, large-scale integration after 16-megabit D-RAM. The purpose is to provide circuit resists.

[Structure of Invention]

In the present invention, the sensitivity characteristics are extremely excellent, but as the main component of the resist, the general formula (I) is difficult to use, such as poor solubility, heat resistance and etching resistance. (However, X in the formula is CH ₃ , Cl, F, Br, CN, NO ₂ , COOR, Y is C
N, H, COOR, R is an alkyl group or a halogenated alkyl group), and a crosslinkable α-cyanoacrylate ester is copolymerized with the monomer to bring out the sensitivity characteristic which is the maximum advantage of the monomer of the general formula (I). A synergistic effect with the sensitivity characteristics of α-cyanoacrylic acid ester improves sensitivity, and crosslinkability α is used to improve heat resistance and dry etching resistance.
-Achieved by cross-linking of cyanoacrylates.

The crosslinkable α-cyanoacrylic acid ester used in the present invention is represented by the following formula.

However, R in the formula is a cross-linking group such as an alkoxyalkyl group, a hydroxyalkyl group, an alkynyl group, and an allyl group, and specifically, 2-methoxyethyl α-cyanoacrylate, hydroxyethyl α-cyanoacrylate, Examples include α-propanoyl cyanoacrylate and allyl α-cyanoacrylate. Corresponding monomers of general formula (I) are specifically vinylidene cyanide, nitroethylene, diethyl methylenemalonate, trichloroethyl methacrylate, hexafluorobutyl methacrylate and the like. These monomers may be those obtained by a usual synthetic method,
The anionic polymerization inhibitor may remain mixed.

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

〔The invention's effect〕

The dry-etching-resistant positive resist material of the present invention is a resist material having an extremely excellent sensitivity characteristic that a radiation dose of 1/100 or less is sufficient as compared with the conventional P-MMA resist. Etching property is the above P-MM
It is a full-scale positive resist that has better resistance than A-resist, and has a great effect on high productivity and cost reduction when manufacturing large-scale semiconductor integrated circuits after 16 megabit D-RAM.

Examples of the present invention will be shown below, but the chemical action of the electron beam and the soft X-ray (wavelength 4 to 10Å) used in X-ray lithography on the substance is the same, and the sensitivity of the resist to the electron beam and the X-ray are the same. Is proportional to the sensitivity to (eg 10 ^-7
C / cm ² ＝ 10mJ / cm ² ), Proc International
Since it is well known in Conf. Microlithography, Paris, July, 261 (1977), etc., in order to avoid complication, it was decided to use the result of electron beam irradiation as an example.

Hereinafter, the present invention will be further described with reference to examples, but it goes without saying that the present invention is not limited to these examples.

Example A Propagyl α-cyanoacrylate 1 part, vinylidene cyanide 13 parts, acetic acid 3 parts, azobisisobutyronitrile 0.
One part was placed in a glass sealed tube and polymerized in nitrogen at 50 ° C. for 15 hours. This was poured into ethyl ether to precipitate a polymer, which was vacuum dried at 40 ° C. to obtain 12.8 parts of a white powdery copolymer. When this copolymer was measured by gel permeation chromatography (GPC) single light scattering method, the molecular weight was about 315,000.

The molecular weights of the polymers in the following Examples and Comparative Examples were measured by the GPC single light scattering method.

Example B 5 parts of 2-hydroxyethyl α-cyanoacrylate, 12 parts of nitroethylene, 3 parts of acetic acid and 0.1 part of azobisisobutyronitrile were polymerized and purified in the same manner as in Example A,
11.6 parts of a pale yellow powdery copolymer was obtained. The molecular weight of this copolymer was about 290,000.

Example C 1 part of allyl α-cyanoacrylate, 13 parts of α-chloroacrylate hexafluorobutyl, 3 parts of acetic acid and 0.1 part of azobisisobutyronitrile were polymerized and purified in the same manner as in Example A, and white 12.1 parts of a powdery copolymer was obtained. The molecular weight of this copolymer was about 335,000.

Example D 2-hydroxyethyl α-cyanoacrylate 1 part, trichloroethyl methacrylate 13 parts, acetic acid 3 parts, and azobisisobutyronitrile 0.1 part were polymerized and purified in the same manner as in Example A to give a white powder. 11.8 parts of a copolymer of The molecular weight of this copolymer was about 353,000.

Comparative Example A 15 parts of ethyl α-cyanoacrylate, 3 parts of acetic acid and 0.1 part of azobisisobutyronitrile were polymerized and purified in the same manner as in Example A to obtain 12.2 parts of a white powdery homopolymer.
The molecular weight of this polymer was about 275,000.

Comparative Example B 15 parts of diethyl methylenemalonate, 3 minutes of acetic acid and 0.1 part of azobisisobutyronitrile were subjected to polymerization purification in the same manner as in Example A to obtain 12.1 parts of a white powdery homopolymer.
The molecular weight of this copolymer was about 330,000.

Example 1 A resist was prepared by adding a thermal crosslinking agent to a 5 wt% cyclohexanone solution of the copolymer obtained in Example A. 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 about 0.54 μm. This film was heat-treated at 160 ° C. for 30 minutes, thermally crosslinked, and then irradiated with an electron beam having an accelerating voltage of 10 KV and 4 × 10 ⁻⁷ C / cm ² . After irradiation, the film was taken out, immersed in a 1: 2 developer of cyclohexanone and methyl isobutyl ketone for 2 minutes at 25 ° C., developed, rinsed with isopropyl alcohol, and heat-treated (post-baked) at 130 ° C. for 30 minutes. This resist film is CF ₄ + 5% O ₂ 10SCCM 60m with CF ₄ -reactive ion etching equipment.
When etching was performed under the conditions of torr, applied power 13.56MHz, 150W, the etching rate of P-MMA was 750Å / min, whereas the etching rate of this resist film was 450Å / min.
At min, the resistance was superior to that of P-MMA. On the other hand, in the area irradiated with the electron beam, the resist was removed and a positive image was formed. When this was observed with a scanning electron microscope (SEM), there was no residual film, and the silicon oxide of the resist had a sharp edge pattern. The adhesiveness with the layer was also good.

Example 2 A resist was prepared by adding a thermal crosslinking agent to a 5 wt% cyclohexanone solution of the copolymer obtained in Example B. This resist was applied onto 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 about 0.49 μm. This film was subjected to thermal crosslinking, electron heat irradiation, development, rinsing, and post-baking according to Example 1. This resist film was etched under the same conditions as in Example 1, and the etching rate of this resist film was determined to be 470 Å / min.
, The resistance was superior to that of P-MMA. On the other hand, the resist was removed from the region irradiated with the electron beam, and a positive image was formed. When this was observed by SEM, a sharp pattern was confirmed without a residual film.

Example 3 A resist was prepared by adding an ultraviolet crosslinking agent to a 5 wt% cyclohexanone solution of the copolymer obtained in Example C. This resist was spin-coated on the thermally oxidized silicon layer having a thickness of 0.5 μm to obtain a copolymer film having a thickness of 0.57 μm. This film was heat-treated at 130 ° C. for 30 minutes, crosslinked with ultraviolet rays, and subjected to electron beam irradiation, development, rinsing, and post-baking according to Example 1. This resist film was used in Example 1.
When the etching rate of this resist was determined by etching under the same conditions as above, it showed a resistance higher than that of P-MMA at 550 Å / min. On the other hand, the resist was removed from the area irradiated with the electron beam, and a positive image was formed. SEM this
As a result, it was confirmed that there was no residual film and a sharp pattern was observed.

Example 4 A resist was prepared by adding a thermal crosslinking agent to a 5 wt% cyclohexanone solution of the copolymer obtained in Example D. This resist was coated on a 0.5 μm thick thermally oxidized silicon layer in the same manner as in Example 1 to obtain a copolymer film having a thickness of 0.55 μm. This film was subjected to thermal crosslinking, electron beam irradiation, development, rinsing, and post-baking according to Example 1. This resist film was etched under the same conditions as in Example 1, and the etching rate of this resist was determined to be 520Å / min and P
-Showed better resistance of MMA.

On the other hand, a sharp pattern was confirmed in the area irradiated with the electron beam without a residual film.

Comparative Example 1 A 5% by weight solution of the homopolymer obtained in Comparative Example A in cyclohexanone was coated on a 0.5 μm thermally oxidized silicon layer in the same manner as in Example 1 to form a polymer film having a thickness of 0.47 μm. Obtained. After heat-treating this at 130 ℃ for 30 minutes, accelerating voltage 10KV,
Irradiation with an electron beam of 6 × 10 ⁻⁷ C / cm ² was performed.

After irradiation, development, rinsing, and heat treatment were performed according to Example 1. When this resist film was etched under the same conditions as in Example 1 and the etching rate of this resist was determined, it was 820 Å / min, which was lower than that of P-MMA. Also, the resist is removed from the area irradiated with the electron beam.
The observation result by SEM was also good.

Comparative Example 2 A 5% by weight toluene solution of the homopolymer of diethyl methylenemalonate obtained in Comparative Example B was prepared and applied onto a 0.5 μm thick thermally oxidized silicon layer by spin coating.
A resist film of about 0.54 μm was obtained. This film is heat-treated (pre-baked) at 140 ℃ for 30 minutes, acceleration voltage 10KV, 6 × 10 ^-7 C / cm
Irradiated with ² electron beams. After irradiation, it was taken out and developed with a mixed solvent of ethyl cellosolve and butyl cellosolve.
Heat treatment (post-baking) was performed at 30 ° C for 30 minutes. When this resist film was etched under the same conditions as in Example 1, the etching rate of this resist film was 780 Å / min, which was lower than that of P-MMA.

A sharp positive image was obtained in the electron beam irradiation region of this resist.

The results of Comparative Examples 1 and 2 and Examples 1 to 4 show that the introduction of the monomer of the general formula (I) having excellent sensitivity characteristics and the introduction of the crosslinkable α-cyanoacrylate ester are remarkable in sensitivity and dry etching resistance. It shows that it brings improvement.

Claims (1)

[Claims] 1. A general formula (I) (However, X in the formula is CH ₃ , C 1, F, Br, CN, COOR, N
O ₂ , Y is CN, H, COOR, R is an alkyl group or a halogenated alkyl group) and a crosslinkable α-cyanoacryl having a crosslinkable group in the side chain A positive-type highly sensitive radiation-sensitive resist whose main component is a copolymer obtained by reacting with an acid ester.