JPH033215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to radiation-sensitive/particle beam materials, specifically, radiation-sensitive materials such as electron beams, Concerning polymeric materials that are sensitive to

Conventionally, photolithography technology, which forms a resist pattern by irradiating light, has been used to manufacture devices that require minute processing, such as integrated circuits and bubble memory devices, but the wavelength of the light depends on the processing accuracy. It is well known that due to the order limit, techniques for forming even finer patterns by irradiation with deep ultraviolet rays, x-rays, electron beams, etc. have been developed and are already being put into practical use.

In the early stages of research, photoresists were sometimes used as resists for forming patterns by irradiating electron beams, x-rays, or deep ultraviolet rays, but in recent years, photoresists have been used to Research and development of materials suitable for deep ultraviolet irradiation is being carried out at home and abroad, and there are already many publications, and some materials are commercially available as products.

As is well known, there are two types of resist: positive type and negative type. Positive type resists become easily soluble in solvents when irradiated, and are dissolved and removed during development, resulting in a pattern in which only the unirradiated areas remain. It is something that can be obtained. In the negative type, the resist in the irradiated area becomes insoluble or hardly soluble, and a pattern in which the irradiated area remains is obtained by development. In other words, when the same pattern is irradiated, an image of the irradiation pattern or its inverse image can be obtained depending on whether the resist is negative or positive, so both types of resist can be used depending on the purpose. is advantageous.

As a positive type of electron beam resist,
Many materials have been proposed, including polymethyl methacrylate, polybudeso-1-sulfone, and polymethyl isopropenyl ketone.
Many negative-type materials have been provided, including polyglycidyl methacrylate, copolymers containing glycidyl methacrylate, epoxidized polybutadiene, and polydiallyl orthophthalate.

Some of the materials listed above have already been put into practical use, and chrome masks have already been manufactured by electron beam lithography. However, in recent years, in order to improve the accuracy of the etching process, dry processes, i.e. ion milling,
As techniques such as sputter etching and plasma etching are used to etch substrates, resist materials are required to have high resistance to these etching methods, that is, dry etching resistance. It has become like this. Conventionally, resists used primarily for mask manufacturing have been required to have sensitivity, resolution, and wet etching resistance; for example, for chrome mask manufacturing, resistance to ceric ammonium nitrate aqueous solution, which is an etching solution for chromium, has been required, and dry etching has been required. Resistance in the process was not considered.

As a result of research on the dry etching resistance of resist materials, it has been found that the resistance is significantly improved when a conjugated ring such as a phenyl group is included in the molecule. The photoresist AZ resist (trade name of Shippray, Inc., USA) has good dry etching resistance, but
It also contains many phenyl groups. but,
Polystyrene is the most important polymer containing many phenyl groups, and in fact, polystyrene has been considered to have the best dry etching resistance.

The present inventors have already searched for materials with better dry etching resistance. As a result, polymer materials with naphthalene groups in their side chains, such as polyvinylnaphthalene, are much more resistant to dry etching than polystyrene, which has phenyl groups in their side chains. They found that the resistance was improved and proposed using it as a negative resist material.

The present inventors conducted further research and discovered that among polymer materials containing vinylnaphthalene as a component, a copolymer of vinylnaphthalene and chlorostyrene has good stability and is easy to synthesize. I arrived at the eggplant.

That is, the resist material of the present invention is a polymer made of random copolymerization of vinylnaphthalene and chlorostyrene. The dry etching resistance increases as the proportion of vinylnaphthalene increases; therefore, the copolymerization ratio is 50% of chlorostyrene in terms of the number of monomer units.
% or less, preferably 5 to 30%, the significance of the present invention will be diminished. The sensitivity increases as the proportion of chlorstyrene increases, but it also increases with increasing molecular weight. However, if the average molecular weight exceeds 1,000,000, it may be difficult to apply uniformly and the resolution may decrease due to swelling during development, and if the average molecular weight is less than 10,000, the sensitivity may be insufficient.

Regarding resolution, molecular weight polydispersity (Mw/
It is known that the smaller the Mn (Mw is the weight average molecular weight, Mn is the number average molecular weight), the better, and it is desirable that it be as close to monodisperse (Mw/Mn=7) as possible. In addition, the resolution of the resist itself may be impaired during development, especially when using high molecular weight materials, which do not swell the resist material and require a solvent to dissolve and remove the portions that were not exposed to irradiation. It is desirable to use it.

Therefore, the molecular weight and copolymerization ratio can be selected depending on the required sensitivity and processability.

According to the present invention, when dry etching is performed in the manufacturing process of semiconductors, integrated circuits, etc., a material with better etching resistance than previously known resist materials is used, so the etching process is safe. It becomes certain.

Furthermore, improved dry etching resistance also contributes to a substantial improvement in resolution. That is, in the resist of the present invention with improved etching resistance,
The thickness of the resist coating can be reduced. As is well known, in electron beam exposure, for example, electrons implanted into a resist material are scattered within the resist, so that as the film thickness increases, resolution decreases.

The copolymer of the present invention can be easily obtained by a conventional radical polymerization method. To give an example, 2
- 0.01 mol of vinylnaphthalene and 0.002 mol of parachlorostyrene, with 1 mol% of AIBN (azobisbu 40 nitrile) added as a reaction initiator based on the monomer concentration, are dissolved in 20 ml of purified benzene, and this solution is put into a polymerization tube. After freezing and degassing, polymerization was carried out in a sealed tube (70°C, 24 hours). Afterwards,
This solution was poured into 100 ml of methanol to separate the polymer. Further, the obtained polymer was dissolved in methylene chloride and purified by adding it to methanol for reprecipitation, which was repeated three times, and then the polymer was dried under reduced pressure. The copolymerization ratio was determined from the elemental analysis value (chlorine content) of the obtained polymer.

Under these conditions, the polymer was obtained almost quantitatively, and the copolymerization ratio of the polymer was almost the same as the initial composition ratio.

Molecular weight and polydispersity were measured using GPC (gel permeation chromatography).

The invention will be explained in detail below using examples.

Example 1 Copolymer of 77.2% 2-vinylnaphthalene and 22.8% P-chlorostyrene (weight average molecular weight 22,000,
Polydispersity 1.8) was dissolved in xylene at 10% by weight,
A resist solution was prepared by filtering it through a 0.2 μm filter. Spin coating onto the substrate at 2000 rpm,
A uniform coating film with a thickness of approximately 0.5 μm was obtained by baking at 100°C for 30 minutes. Using an electron beam exposure device (JBX-5A manufactured by JEOL Ltd.), the acceleration voltage was 20KV.
Then, various patterns were drawn by changing the exposure amount. Thereafter, it was taken out from the apparatus and developed by immersing it in benzyl acetate for 60 seconds, followed by rinsing by immersing it in isopropanol for 30 seconds to obtain a resist pattern. After post-baking at 150°C for 30 minutes, the film thickness was measured using a stylus method (using Talysurf manufactured by Taylor Hobson), and the remaining film thickness at different exposure doses was measured, as shown in curve 1 in the figure. A sensitivity curve was obtained. The horizontal axis of the figure represents the exposure amount, and the vertical axis represents the film thickness after development normalized by the film thickness before development. This is the practical sensitivity of negative resist. Exposure amount (D ^0.5 g) so that the residual film thickness is 1/2 of the initial film thickness
It was found that the sensitivity was 3.5×10 ⁻⁴ coulombs/cm ² , which is twice as high as that of poly-2-vinylnaphthalene having the same molecular weight. The obtained resist pattern sufficiently resolved fine patterns of 1 μm or less.

Next, in order to examine the dry etching resistance of this copolymer, a coating film was formed on the substrate using the same method as described above.
AZ resist was prepared with a coating film formed in the same way, and Av ion milling was performed using equipment manufactured by Vico, and CCL ₄ gas plasma etching was performed.
The etching rate was measured using a device manufactured by ETE.

As a result, the etching rate of this copolymer was found to be approximately 70% that of polystyrene or AZ resist. However, it was found that the etch rate was about 20% faster and the resistance was slightly impaired when compared with poly-2-vinylnaphthalene homopolymer. Therefore, in the dry etching process, this copolymer can be used with polystyrene or AZ
It was found that a film thickness of 70% of that of the resist is sufficient and can also contribute to improved resolution.

Example 2 8% by weight of a copolymer (25.8% chlorstyrene, 74.2% 2-vinylnaphthalene, weight average molecular weight 222,000, polydispersity 2.1) was dissolved in xylene, filtered through a 0.2 μm filter, and mixed with a resist solution. did.

When this was evaluated in the same manner as described in Example 1, a sensitivity curve shown as curve 2 in the figure was obtained. However, development was performed by immersing the film in a mixed solvent of 3 volumes of tetrahydrofuran and 1 volume of ethanol for 60 seconds, followed by rinsing for 30 seconds with a mixed solvent of 1 volume of methyl ethyl ketone and 2 volumes of ethanol.

The exposure amount D ⁱ _g at the gel point is 2.3×10 ^-5 coulombs/cm ² ,
D ^0.5 g was 3.6×10 ⁻⁵ coulombs/cm ² .

[Brief explanation of the drawing]

The figure is a diagram showing a sensitivity curve of the resist material of the present invention to electron beam irradiation. Curve 1 is a copolymer of 2-vinylnaphthalene (77.2%) and P-chlorostyrene (22.8%) with a weight average molecular weight of 22,000 (Example 1), and curve 2 is a copolymer of 2-vinylnaphthalene (74.2%) with a weight average molecular weight of 222,000.
%) and chlorstyrene (25.8%) copolymer (Example 2).

Claims (1)

[Scope of Claims] 1. A resist material comprising a copolymer of vinylnaphthalene and chlorostyrene as a radiation-sensitive or particle beam material. 2. The resist material according to claim 1, wherein the copolymerization ratio of vinylnaphthalene and chlorostyrene is 5 to 50% of chlorstyrene in terms of monomer ratio.