JPS63271252A - Radiation sensitive resist - Google Patents

Abstract

PURPOSE:To improve the resolution of the titled resist by using a monodispersive polymer obtd. by homopolymerizing a crosslinkable alpha- cyanoacrylate for the titled resist. CONSTITUTION:The titled resist contains the monodispersive homopolymer of the crosslinkable alpha-cyanoacrylate or the monodispersive copolymer of two or more kinds of said monomers or the monodispersive copolymer of one or more kinds of said monomers and one or more kinds of a noncrosslinkable alpha-cyanoacrylate as a main component. Thus, as the titled resist has the high dry etching resistance in addition to the excellent resolution and sensitivity, the titled resist is available for the high resolution resist of for example, a D-RAM semiconductor of larger than 64 megabit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radiation-sensitive resist having excellent dry etching resistance and high resolution.

More specifically, by homopolymerizing a crosslinkable α-cyanoacrylate or by copolymerizing this with a crosslinkable or non-crosslinkable α-cyanoacrylate, the resolution can be improved and For example, 64 Mbit D-RA
The purpose is to provide a resist for semiconductor large-scale integrated circuits of M and later.

[Technical background of the invention]

Semiconductor integrated circuits have a line width of 0.5μ, which is the limit of optical exposure.
- Techniques such as electron beam direct writing and X-ray lithography have been developed as below-level adhesive lithography techniques, and the development of resists compatible with these techniques is now at an urgent stage.

By irradiating these resist materials with radiation,
By irradiating a negative type that causes a crosslinking reaction and becomes insoluble in a developer, the main polymer of the resist undergoes a main chain splitting reaction and becomes lower in molecular weight, becoming easily soluble in a developer and reducing the irradiation area. It is a positive type that only removes resist.

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

On the other hand, positive resists have high resolution but are inferior in sensitivity and etching resistance to negative resists.

Recently, the rate of integration of large-scale integrated circuits has been further accelerated, and the mainstream of radiation-sensitive resists has shifted to positive resists. However, this resist has major weaknesses in low sensitivity and dry etching resistance, which have not yet been resolved.

(Prior art and its problems) Polymethyl methacrylate (P-MMA) is a typical main polymer for positive resists, but its excellent resolution (0.3 to 0.5 μ-) is extremely unbalanced. It is not recognized as a practical resist because of its low sensitivity (5×10 −1 c/cd) and insufficient dry etching resistance.

For this reason, the industry's interest is focused on improving dry etching resistance and sensitivity, and many proposals have been made, but since sensitivity to radiation and dry etching resistance are mutually contradictory functions, no critical improvement has been achieved. is not mentioned,
C4 to improve resist sensitivity! +81 F+S,
Introduction of electron-withdrawing groups such as LN is considered, for example, polyhexafluorobutyl methacrylate, polytrichloroethyl methacrylate, polytrifluoroethyl α-chloroacrylate, polybutene-1 sulfone, poly2-
Methylpentene-1-sulfone-novolak resin mixtures have been proposed, but most of them have low dry etching resistance due to the introduction of electron-withdrawing groups, and are far from being suitable as full-scale resists.

Dry etching resistance can be improved by introducing a benzene ring into the side chain of the main polymer, introducing an alkyl group with a large molecular weight, introducing a cross-linking group, adding a radical scavenger, etc. However, this may lead to a decrease in sensitivity and result in an imbalance. Since there is no suitable resist, the actual situation is that resists are selected depending on the conditions of use.

Styrene, P-
It has been reported that the resolution can be significantly improved by using an anionic polymerization initiator such as dimethylaminomethylstyrene, isoprene, or alkyllithium to form a monodisperse polymer.

[Purpose of the invention]

The present invention improves the dry etching resistance, which is considered the biggest drawback of resists whose main polymer is α-cyanoacrylic acid ester, by crosslinking the resist film, and uses a monodisperse polymer to improve resolution. By introducing an electron-withdrawing group into the resist, it is intended to provide a high-resolution resist for D-RAM of, for example, 64 megabits or higher.

[Structure of the invention]

That is, the present invention employs a monodisperse polymer as a crosslinkable α-cyanoacrylate homopolymer or a crosslinkable copolymer to improve resolution, and also crosslinks these crosslinkable polymers before or after radiation irradiation. By this, we succeeded in improving the dry etching resistance.

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

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

The corresponding α-cyanoacrylic acid ester was developed by taking into account various process control conditions that may affect the main properties of the resist, such as etching resistance, heat resistance, and adhesion to the silicon oxide layer of the resist film. In addition to the crosslinkable α-cyanoacrylic acid ester, if necessary,
Non-crosslinkable α-cyanoacrylic esters are also used.

The non-crosslinkable α-cyanoacrylate ester used is specifically methyl α-cyanoacrylate.

α-cyanoacrylate ethyl, α-cyanoacrylate n
-propyl, α-isopropyl cyanoacrylate, α-
n-butyl cyanoacrylate, isobutyl α-cyanoacrylate, n-pentyl α-cyanoacrylate, isoamyl α-cyanoacrylate, an-cyanoacrylate
hexyl, α-cyclohexyl cyanoacrylate, α-
n-octyl cyanoacrylate, 2-ethylhexyl α-cyanoacrylate, trifluoroethyl α-cyanoacrylate, trichloroethyl α-cyanoacrylate, α
- phenyl cyanoacrylate, etc.

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

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

〔Effect of the invention〕

The positive resist material according to the present invention has excellent resolution and excellent sensitivity characteristics not seen in conventional positive resists, as well as high dry etching resistance, making it suitable for use in large-scale semiconductor applications such as D-RAMs of 64 megabits and above. It is suitable for ultra-high-density engraving such as that used in one process of electron beam and Its characteristics and excellent dry etching resistance bring about significant effects in cost reduction and high productivity.

Examples of the present invention will be shown below, but the chemical effects of electron beams and soft X-rays (wavelength 4 to IO) used in X-ray phosphorography are the same, and the sensitivity of the resist to electron beams is the same. and the sensitivity to X-rays are in a proportional relationship (for example, 10
-'C/d -10■J/d) is Proc
International Conf, formerly crol
it-hography, Paris, July
261 (197?), etc., so in order to avoid complications, the results obtained by electron beam irradiation will be used as an example.

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 Anionic polymerization initiator 7 containing 5X10-' moles of thiourea
00 ml of acetone solution was introduced into the flask, and the system temperature was cooled to -70°C. While thoroughly stirring the system, add α containing 50pp of anionic polymerization inhibitor sow.
-Allyl cyanoacrylate 0.01. 1 containing moles
0.00 liters of acetone solution was added while keeping the system temperature below -70°C to form a living polymer, which contained 0.09 mol of cyclohexyl α-cyanoacrylate containing 50 ppm of anionic polymerization inhibitor.
0s+1 acetone solution and then lower the system temperature to -70℃.
After adding and carrying out a copolymerization reaction while keeping the temperature below ℃, a polymerization terminator was added to terminate the polymerization reaction. After the obtained copolymer was purified by reprecipitation method, its molecular weight was measured by gel permeation chromatography (GPC)-light scattering method.The molecular weight was 338,000, and its dispersity (
Mw/Mn) was 05.

Make a 5% by weight solution of this polymer in cyclohexanone,
A UV crosslinking agent was added to this to prepare a resist. This resist was applied onto a thermally oxidized silicone layer having a thickness of 0.5/7 by a spin coating method to obtain a copolymer film having a thickness of 0.53 μm. After heat treatment (pre-baking) at 130°C for 30 minutes, cross-linking with ultraviolet rays, acceleration voltage 10KV, 4
An electron beam of x 10-'C/cj was irradiated onto the resist film surface according to a predetermined pattern. Subsequently, this was taken out into the atmosphere and developed by immersing it in a 1+2 developer of cyclohexanone and methyl isobutyl ketone at 25°C for 3 minutes, and then rinsed with isopropyl alcohol and dried at 130°C for 30 minutes. Heat treated (post-baked).

This resist film was etched using a CF4 reactive ion etching device at CFa+5%Ox IO3CCM 60mTorr+
When etching was performed under the conditions of applied power of 13.56 MHz and 150 W, the etching rate of P-MMA was 75-0 people/sin, whereas the etching rate of this resist was 450 people/sin, and P-MM
It showed better resistance than A. When the pattern of the silicon oxide layer of this system was observed using a scanning electron microscope (SEM), the formation of a linear pattern of 0.3 μm diameter was observed.

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 2-ethylhexyl α-cyanoacrylate and 2-hydroxyethyl α-cyanoacrylate in a molar ratio of 9:1 was obtained by a low-temperature anionic polymerization method according to Example 1. The molecular weight is 418,000, the degree of dispersion (MwMn
)=1.04. A 5% by weight cyclohexanone solution of this polymer was prepared, and a thermal crosslinking agent was added thereto to prepare a resist. This resist was coated with a 0%
．． A copolymer film with a thickness of 0.54 μm was obtained on a thermally oxidized silicon layer with a thickness of 5 μm.

This was heat-treated at 150° C. for 30 minutes to cause crosslinking, followed by electron beam irradiation, development, rinsing, and post-baking in the same manner as in Example 1.

When this resist film was etched under the conditions of Example 1, the etching rate of this resist film was 420 people/
sin and showed better resistance than P-MMA. The patterning results of the silicon oxide layer by RIH of this system are shown in S
Observation by EM confirmed a fine 0.3μ linear pattern.

Example 3 A monodisperse copolymer of propargyl α-cyanoacrylate and hexafluorobutyl α-cyanoacrylate in a molar ratio of 1:9 was obtained by a low-temperature anionic polymerization method according to Example 1. 464,000, degree of dispersion (M-wealth n) = 1.
It was 05. A resist was prepared by preparing a 5% by weight solution of this polymer in cyclohexanone and adding a thermal crosslinking agent thereto. This resist was coated with 0.5μ■ by spin coating method.
A copolymer film of film J1 with a thickness of 0.56 μm was obtained by coating on a thermally oxidized silicon layer with a thickness of 0.56 μm.

This was prebaked, thermally crosslinked, electron beam irradiated, developed, rinsed, and then postbaked in accordance with Example 2. When this resist film was etched according to Example 1, the etching rate of this resist film was 580 people/sin, which showed superior resistance to P-MMA. RIH of this system
When the patterning results of the silicon oxide layer were observed by SEM, a fine 0.3 μm linear pattern was confirmed.

Example 4 A monodisperse copolymer of allyl α-cyanoacrylate and propyl α-cyanoacrylate in a molar ratio of 1:9 was obtained by a low-temperature anionic polymerization method according to Example 1, but its molecular weight was 31.
．． 10,000, and the degree of dispersion (MwMn) was 1.07. A 5% by weight cyclohexanone solution of this polymer was prepared, and a UV crosslinking agent was added thereto to prepare a resist. 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 0.48 μm. This was subjected to prebaking, ultraviolet crosslinking, electron beam irradiation, development, rinsing, and postbaking in accordance with Example 1. This resist film was etched according to Example 1. The etching rate of this resist film was 430 people/+++in, which showed better resistance than P-MMA. When the patterning result of the silicon oxide layer by RIH of this system was observed by SEM, a sharp linear pattern of 0.3 μ- was confirmed.

Example 5 A monodisperse copolymer of propargyl α-cyanoacrylate and cyclohexyl α-cyanoacrylate in a molar ratio of 1:9 was obtained by a low-temperature anionic polymerization method according to Example 1, but its molecular weight was 338,000, Dispersity (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 microns by a spin coating method to obtain a copolymer film with a thickness of 0.51 microns.

This was subjected to prebaking, thermal crosslinking, electron beam irradiation, development, rinsing, and postbaking in accordance with Example 2. This resist film was etched according to Example 1. The etching rate of this resist film is 465 people/■1n and P-MM.
It showed better resistance than A.

When the patterning results of the silicon oxide layer by RIE of this system were observed using SEM, the formation of a 0.3 μl linear pattern was found to be f! iW was done.

Comparative Example 1 A monodisperse homopolymer of ethyl α-cyanoacrylate was obtained by a low-temperature anionic polymerization method according to Example 1, but its molecular weight was 245,000 and the degree of dispersion (Mw/Mn) was −1.06. there were. A 5% by weight cyclohexanone solution of this polymer was prepared and coated on a thermally oxidized silicon layer with a thickness of 0.48 μm by a spin coating method to obtain a polymer film with a thickness of 0.48 μm. After heat treatment (prebaking) at 130''C for 230 minutes, the resist film surface was irradiated with an electron beam of 6X10~'C/cii at an acceleration voltage of 10KV according to a predetermined pattern.Subsequently, development, rinsing, and post-processing were performed in accordance with Example 1. Baked.

When this resist film was etched according to Example 1, the etching rate was 810 people/sin.
showed lower tolerance. The resolution of this resist was 0.3 μm as in Examples 1-5.

Comparative Example 2 A monodisperse copolymer of trifluoroethyl α-cyanoacrylate and ethyl α-cyanoacrylate 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 31. 70,000, dispersion degree (M@/Mn) = 1.04
Met.

This 5% by weight cyclohexanone solution was prepared and applied by spin coating onto a thermally oxidized silicon layer with a thickness of 0.5 μm to obtain a copolymer film with a thickness of 0.46 μm. This was prebaked, electron beam irradiated, developed, and processed according to Example 1.
I did a rinse and post bake.

When this resist film was etched, the etching rate was 860 people/win, which showed lower resistance than P-MMA. The resolution of this resist is 0.3 as in Examples 1 to 5.
It was μ mackerel.

Comparative Example 3 15 parts of ethyl α-cyanoacrylate, 3 parts of acetic acid, and 081 parts of azobisisobutyronitrile were placed in a glass sealed tube and heated in nitrogen at 50°C for 115 hours.
One part of a non-monodisperse homopolymer having a molecular weight of 320,000 was obtained.

This was prepared into a 5% by weight cyclohexanone solution, and 0.0% by weight was prepared.
Coated on a thermally oxidized silicon layer with a thickness of 0.42μ.
A homopolymer film with a film thickness of - was obtained.

This was subjected to pre-baking, electron beam irradiation, development, rinsing and post-baking according to Example 1, and this resist film was R
Etched by IH. When this result was observed with SEM, a 0.4 μ-linear pattern was confirmed.

The results of Comparative Examples 1 to 3 and Examples 1 to 5 demonstrate that the introduction of a monodisperse polymer and a crosslinkable α-cyanoacrylate ester resulted in critical improvements in resolution and dry etching resistance.

Claims (1)

[Claims] 1) A monodisperse homopolymer of crosslinkable α-cyanoacrylate ester, a monodisperse copolymer consisting of two or more of this monomer group, or one or more of these monomers and non-crosslinkable α-
A dry etching-resistant, high-resolution radiation-sensitive resist whose main ingredient is a monodisperse copolymer composed of one or more cyanoacrylic acid esters.