JPH0615585B2 - Silicon atom-containing ethylene polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silicon atom-containing ethylene polymer, and particularly to a silicon atom-containing ethylene polymer suitable for a fine pattern forming method for semiconductor integrated circuits, magnetic bubble memories and the like. Regarding

[Prior Art] When forming a fine pattern by using optical lithography or electron beam lithography in the production of integrated circuits, valve memory devices, etc., in optical lithography, the influence of reflected waves from the substrate, in electron beam lithography It is known that the resolution decreases when the resist is thick due to the influence of electron scattering. Dry etching is used to accurately transfer the resist pattern obtained by development to the substrate, but if a thin resist layer is used in order to obtain a high-resolution resist pattern, the resist is also etched by dry etching to leave the substrate. The disadvantage is that it does not exhibit sufficient resistance to work. Further, in the step portion, it is necessary to apply a thick resist layer in order to flatten the step, and it can be said that it is extremely difficult to form a fine pattern in the resist layer.

In order to solve such inconvenience, a three-layer structure resist has been proposed by JM Moran et al. In Journal of Vacuum Science and Technology, Vol. 16, 1620.
Page (1979). In the three-layer structure, after applying a thick organic layer to the first layer (bottom layer), an inorganic layer such as a silicon oxide film, a silicon nitride film, or a silicon film which is difficult to be etched by dry etching using O ₂ as an intermediate layer. Form material. Then, a resist is spin-coated on the intermediate layer, and the resist is exposed and developed by an electron beam or light. The obtained resist pattern is used as a mask to dry-etch the intermediate layer, and thereafter,
Using this intermediate layer as a mask, the first thick organic layer is etched by the reactive sputter etching method using O ₂ .
By this method, a thin high-resolution resist pattern can be converted into a thick organic layer pattern. However, in such a method, since the intermediate layer is formed by the vapor deposition method, the sputtering method or the plasma CVD method after the first layer is formed, and the patterning resist is applied, the process is complicated and long. There is.

If the patterning resist is strong against dry etching, the thick organic layer can be etched using the patterning resist as a mask, so that a two-layer structure can be obtained and the process can be simplified.

[Problems to be Solved by the Invention] It is known that polydimethylsiloxane has extremely excellent resistance to oxygen-reactive ion etching (O ₂ RIE) and an etching rate of almost zero (Di-N).
Taylor, TM Wolf and J
M Moran, Journal of Vacuum Science and Technology, 19 (4), 872, 1981 (GN
Taylor, TM Wolf and JM Moran, J.Vacuum Sci. And
Tech., 19 (4), 872, 1981)), but since this polymer is liquid at room temperature, it is not suitable as a resist material because it has the drawbacks that dust easily adheres and it is difficult to obtain high resolution.

We have already proposed a homopolymer and a copolymer of trialkylsilylstyrene as the patterning resist [Japanese Patent Application No. 57-123866 (Japanese Patent Application Laid-Open No. 59-15419), Japanese Patent Application No. 57-123865 (Japanese Patent Application No. 57-123865). JP-A-59-15243))]. However, since these polymers have excellent sensitivity to far-ultraviolet or electron beam exposure, they are suitable as resists for far-ultraviolet or electron beam exposure, but do not crosslink to near-ultraviolet and visible light exposure, It could not be used as a photo resist.

In addition, we have already provided a silane-based polymer as an optical exposure resist for the above patterning (Japanese Patent Application No. 60-
001636, Japanese Patent Application No. 60-001637). However, the resist provided here has a silicon atom concentration of about 10 to 10% relative to the polymer.
Since it is 13% (W / W), when the lower layer is thick, for example, when the thickness of the lower layer is 1.5 μm or more, the dry etching resistance is insufficient as the upper layer for patterning.

The object of the present invention is to form a fine pattern with extremely high sensitivity to electron beams, X-rays, deep ultraviolet rays, ion beams, or in addition to these, near ultraviolet rays, and yet have a stronger resistance to dry etching. To provide a polymer.

[Means for Solving Problems] As a result of continuing the research in view of such a situation, the present inventors have found that the monomer unit of the polymer has two silicon atoms and an allyl group. Extremely strong against reactive sputter etching with oxygen, and can be used as a mask when etching thick organic films.
The inventors have found that they are extremely sensitive to rays, deep ultraviolet rays, and ion beams, and that they are also very sensitive to near ultraviolet rays when added with a bisazide compound, and have completed the present invention.

That is, the present invention is a silicon atom-containing ethylene polymer having a molecular weight of 3,000 to 100,000, the main chain of which is composed of the following structural units.

(In the formula, n represents a positive integer of 1 to 6.) Further, according to the present invention, a resist composition comprising the polymer and bisazide, and a resist layer having an organic film and a predetermined resist pattern on a substrate. In a two-layer structure resist method using the resist pattern as a dry etching mask for an organic film, wherein the resist layer comprises the silicon atom-containing ethylene polymer or the polymer and bisazide. There is provided a pattern forming method formed by.

Further, when the polymer is generally used as a negative resist,
If the molecular weight is high, the sensitivity will be high, but the resolution will be lost due to swelling during development. In general, those having a molecular weight of more than 1 million cannot be expected to have high resolution. On the other hand, reducing the molecular weight improves the resolution, but the sensitivity decreases in proportion to the molecular weight and loses practicality, and it is difficult to form a uniform and firm swell when the molecular weight is 3,000 or less. There is. Therefore, the molecular weight of the silicon atom-containing ethylene polymer is 3000 to 10
Those in the range of 00000 are suitable.

The silicon atom-containing ethylene polymer of the present invention can be produced, for example, as follows.

n is a positive integer of 1 to 6, and x is a positive integer of 15 to 4000. As shown in the above formula, the polymer of the present invention is an anionic polymerization method using n-butyllithium (n-BuLi). Thus, a polymer having a low polydispersity and a low to high molecular weight and having an arbitrary molecular weight can be produced.

This polymer is soluble in common organic solvents such as hexane, benzene, methyl ethyl ketone and chloroform, but insoluble in methanol and ethanol.

The polymer of the present invention can be used as a resist material. When used as a resist material, it is extremely sensitive to electron beams, X-rays, and deep ultraviolet rays as it is, but when bisazide known as a photocrosslinking agent is added, it becomes a highly sensitive resist to ultraviolet rays. Become. The bisazide used in the present invention includes 4,4′-diazidochalcone,
2,6'-di- (4'-azidobenzal) cyclohexanone, 2,6-di- (4'-azidobenzal) -4-methylcyclohexanone, 2,6-di- (4'-azidobenzal) -4-hydroxy Examples thereof include cyclohexanone. If the amount of the photo-crosslinking agent added is too small or too large, the sensitivity to ultraviolet rays is reduced, and the composition added too much deteriorates the resistance to O ₂ dry etching. It is desirable to add%.

It is known that the uniformity of the molecular weight distribution also affects the resolution, and the smaller the polydispersity, the better the resolution. In this respect, the above-mentioned method produced from the anionic polymerization method does not have a molecular weight fractionation but directly has a small polydispersity, for example, 1.2.
Alternatively, since a polymer having a molecular weight of less than that is obtained, the resist material has excellent resolution.

EXAMPLES Next, the present invention will be described with reference to examples.

Raw Material Production Example 1 Production of 1,4-dimethoxytetramethyldisilylethane A 16-liter flask was charged with 16 g (0.5 mol) of methanol, 34.5 g (0.5 mol) of pyridine and 400 ml of carbon tetrachloride and cooled in an ice bath. A solution of 54.2 g (0.25 mol) of 1,4-dichlorotetramethyldisilylethane and 100 ml of carbon tetrachloride was added dropwise to the reaction solution over 2 hours. After the dropping was completed, the reaction was continued for another hour at room temperature. After the reaction was completed, the produced solid matter was removed by filtration, and the solvent of the filtrate was distilled off under reduced pressure. The residue was distilled to obtain the target compound. 87.5 g (85
%) Yield.

Raw Material Production Example 2 Production of 1-allyl-4-methoxytetramethyldisilylethane A 500 ml flask was completely replaced with dry nitrogen gas. Magnesium (4.8 g, 0.2 gram atom) and ether (10 ml) were charged, and a small amount of ethyl bromide was added to activate magnesium. After adding 200 ml of ether, 24.2 g (0.2 mol) of allyl bromide was added dropwise under gentle reflux. After the dropping was completed, the reaction was further continued at room temperature for 2 hours. 1,4-prepared in Raw Material Production Example 1 in another 500 ml flask
41.2 g (0.2 mol) of dimethoxytetramethyldisilylethane and 100 ml of ether were charged, and the Grignard reagent prepared above was added dropwise at room temperature to generate heat and bring to a gentle reflux state. After the dropwise addition was completed, the reaction was continued at room temperature for 4 hours. After the reaction was completed, the solution was filtered and the solvent of the filtrate was distilled off under reduced pressure. The residue was distilled to obtain the target compound. The yield was 30 g (60%).

Raw Material Production Example 3 Production of 1-allyl-4-vinyltetramethyldisilylethane Magnesium 4.8 g (0.2 gram atom) in a 300 ml flask.
Then, 30 ml of tetrahydrofuran (THF) was charged, a small amount of ethyl bromide was added, and the mixture was heated. After returning to room temperature, a solution of 21.4 g (0.2 mol) of vinyl bromide in 50 ml of THF was added over 1 hour. After continuing the reaction for 4 hours under reflux, the mixture was cooled to room temperature. In another 300 ml flask, 32.4 g (0.15 mol) of 1-allyl-4-methoxytetramethyldisilylethane produced in Starting Material Production Example 2 and 50 ml of THF were charged. It was brought to reflux and the Grignard reagent prepared above was added dropwise over a period of 1 hour. Further, the reaction was continued under reflux for 1 hour, and then cooled to room temperature. The reaction solution was poured into a dilute HCl solution, and 500 ml of ether was added for extraction. After drying the ether layer over magnesium sulfate, the ether was distilled off, and the residue was distilled to obtain 15 g of the target compound (45
%) Was obtained.

Example 1 The monomer synthesized in Raw Material Production Example 3 and THF were predried with calcium hydride. All the polymerization reactions described below were carried out under high vacuum.

11 g of the monomer produced in Raw Material Production Example 3 was charged into a 100 ml side-armed flask, the side-arm was sealed with a rubber septum, and the flask was connected to a high vacuum line. It was frozen in a liquid nitrogen bath and then depressurized to return to a liquid state. This operation was repeated four times to deaerate the air contained in the monomer, and then 0.5 ml of n-butyllithium (1.6M in hexane) was added to completely dehydrate the monomer. Then, it distilled to the same side branch flask. 50 ml of THF was also degassed and dehydrated in the same manner and distilled into a polymerization flask. N-Butyllithium (1.6M in hexane) 8 from a rubber septum using a microsyringe at room temperature
Polymerization was carried out by adding 0 μl and immediately cooling in an acetone-dry ice bath. After 2 hours, 1 ml of methanol was added using a syringe to stop the polymerization, the pressure was returned to normal pressure, and the polymer solution was poured into 500 ml of methanol. The polymer was precipitated as a white solid and separated in 3 times. Further, it was dissolved in 100 ml of benzene and added to 500 ml of methanol.
After repeating this operation 3 times, it was dried at 50 ° C. under reduced pressure. The yield of the target compound was 10.5 g (95%).

Weight average molecular weight (Mw) = 55,000 Number average molecular weight (Mn) = 51,000 Polydispersity (Mw / Mn) = 1.07 Since this polymer has two silicon atoms in one unit, the silicon content is 26.4% based on total polymer
(W / W).

Example 2 0.42 g of the polymer prepared in Example 1 and 2,6-di- (4'-
Azidobenzal) -4-methylcyclohexanone 0.021
g was dissolved in 6.0 ml of xylene and stirred thoroughly, then 0.5 μm
It filtered with the filter of No. 3, and was set as the sample solution. This solution was spin-coated (3000 rpm) on a silicon substrate and dried at 80 ° C. for 30 minutes. Exposure was performed through a chrome mask using an ultraviolet exposure device (MANN 4800 DSW (manufactured by GCA)).

After development was carried out by immersing in methyl isobutyl ketone (MIBK) for 1 minute, rinsing was performed with isopropanol for 1 minute. After drying, the film thickness of the irradiated portion was measured by the stylus method. The initial film thickness was 0.25 μm. Whether or not the fine pattern was resolved was examined by drawing line-and-space patterns of various sizes and observing the resist image obtained by the development treatment with an optical microscope or a scanning electron microscope.

From the sensitivity curve, it was found that the gel point (▲ D ⁱ _g ▼) was about 0.78 seconds. The appropriate exposure amount of Shipley MP-1300 (1 μm thick), which is a photoresist widely used for ultraviolet exposure, was 0.38 seconds.

Example 3 A resist material (MP-1300 (manufactured by Shipley Co.)) containing a novolac resin as a main component was applied on a silicon substrate to a thickness of 1.5 μm and baked at 250 ° C. for 1 hour. After that, the solution prepared in Example 2 was spin-coated at 80 ° C.
After drying for 30 minutes, a uniform coating film having a thickness of 0.25 μm was obtained. This substrate was exposed for 10.0 seconds through a chrome mask using an ultraviolet exposure device (4800 DSW (manufactured by GCA)). MIBK / n-BuO
After immersion in H 2 (50/100 V / V) for 1 minute to develop, rinsing with isopropanol for 1 minute was performed. This substrate was etched for 25 minutes under the conditions of O _{2 2} sccm, 3.0 pa, 0.16 W / cm ² using a parallel plate reactive sputter etching apparatus (DEM-451 manufactured by Anerva Co.). As a result of observation with a scanning electron microscope, it was found that the submicron upper layer pattern was accurately transferred to the lower layer resist material to form a more vertical pattern.

[Effect of the Invention] As described above, the polymer of the present invention has two silicon atoms per structural unit. Therefore, when the silicon concentration is high, for example, when n is 2 in the general formula (I), 26.4
% (W / W). Therefore, the resist composition consisting of this polymer is extremely resistant to dry etching,
With a film thickness of about 0.5 μm, it can serve as a mask for etching a thick organic layer of about 1.5 μm. Therefore, the resist film for pattern formation may be thin. In addition, since the proximity effect is reduced in electron beam exposure when a thick organic layer is provided as the underlying layer and the adverse effect of reflected waves is reduced in optical exposure, a high-resolution pattern can be easily obtained. High resolution patterns can also be easily obtained by other exposure methods.

Furthermore, when the polymer of the present invention is synthesized by an anionic polymerization method, a polydispersity of the molecular weight distribution is small,
Therefore, when the composition of the polymer and bisazide is used as a resist, the resolution of the obtained pattern becomes more excellent.

Claims (1)

[Claims] 1. A silicon atom-containing ethylene polymer having a molecular weight of 3,000 to 100,000, wherein the main chain is composed of the following structural units. (In the formula, n represents a positive integer of 1 to 6.)