JPH083627B2 - Radiation sensitive material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a highly sensitive radiation-sensitive material capable of forming a uniform film by a simple and inexpensive wet coating method.

[Prior Art] Conventionally, in an inorganic resist material using the photosensitivity of an amorphous chalcogenide thin film, a vacuum technique such as vapor deposition or sputtering is used for forming the thin film as described in JP-A-56-27137. Was needed. These so-called dry processes have drawbacks in that they require expensive equipment and complicated operations, and that film formation takes time and productivity is insufficient. On the other hand, organic resists based on organic polymer materials have been widely used because a uniform and good coating film can be obtained by a simple and inexpensive wet coating method. Inorganic resist materials have features that organic resists do not have, such as strong resistance to oxygen plasma and strong light absorption.
There has been a strong demand for an inorganic resist material capable of forming a film by a simple coating method.

In order to meet the above demands, a condensed tungsten-based inorganic resist material disclosed in Japanese Patent Application No. 60-114081 (Japanese Patent Laid-Open No. 61-273539) has been proposed.

[Problems to be solved by the invention]

The above-mentioned condensed tungsten-based inorganic resist material has a drawback that its sensitivity to various radiations is slightly smaller than that of conventional organic resists.

The present invention aims to improve the sensitivity of this condensed tungstic acid-based inorganic resist.

[Means for solving problems]

The above object is achieved by substituting a part of the tungsten atoms of condensed tungstic acid with niobium (Nb) and / or titanium (Ti).

The condensed tungstic acid described in Japanese Patent Application No. 60-114081 (Japanese Patent Application Laid-Open No. 61-273539) is obtained only as an amorphous substance, so the structure is not clear. However, by analogy with other condensed acids, WX ₆ (X is oxygen, peroxo group (0-
0) or negative ion such as OH) is considered to have a network structure in which octahedra are connected directly or through other molecules such as water. Considering the Nb-substituted form of the present invention, it is considered that a part of this WX ₆ is replaced with an NbX ₆ octahedron.

The condensed acid of the present invention is obtained by reacting a metal tungsten powder (or tungsten carbide) and a mixture of niobium carbide (or niobium metal) and / or titanium carbide (or titanium metal) powder with an aqueous hydrogen peroxide solution. Elemental analysis and thermal analysis are determined from an empirical formula (general formula) _{is, (1-xl) WO 3} · x / 2Nb 2 O 5 · lTiO 2 · yH 2 O 2 · zH 2 O · mCO 2 ( where 0 < x + 1 <1,0 <y1,0.16 <z <4.0m
The range is 0.25).

The radiation-sensitive material of the present invention comprises x or l of the above general formula.
One of the values may be 0, and the value of x + 1 is 0 <x +
The range of 0.5 is a particularly preferable range.

The radiation-sensitive material of the present invention can be used by dissolving it in water or a mixed solvent of water and an organic solvent. Any organic solvent may be used as long as it is almost uniformly mixed with water. To prevent evaporation during storage, room temperature (20
Those having a low vapor pressure of 100 Torr or less at (° C) are particularly preferable. As an example, ethyl cellosolve, butyl cellosolve, diglyme (bis (2-methoxyethyl) ether), 2-butanol and the like can be used by mixing two or more kinds. Even if the amount of the organic solvent is small, it has the effect of improving the coating property, etc.
Is preferred.

As the developing solution for the material of the present invention, various ones described in the examples can be used. As a preferable developing solution, an acetic acid salt is added to an aqueous solution of pH 2 to 5, for example, an aqueous sulfuric acid solution such as sodium acetate or potassium acetate Some have added acetate. When such a developing solution is used, the film loss in the exposed area is reduced, and a resist pattern with high contrast can be obtained.

[Action]

The radiation-sensitive material comprising a condensed acid of tungsten and niobium and / or titanium of the present invention has advantages in that it can form a uniform thin film by wet coating and has strong resistance to oxygen plasma. 60-11
It is the same as the condensed acid containing only tungsten described in JP-A No. 4081 (JP-A-61-273539). The point that the material of the present invention is improved over the condensed acid of tungsten alone is that the sensitivity to ultraviolet rays, electron beams or X-rays is increased by the addition of niobium and / or titanium.

As mentioned above, tungsten and niobium and / or
Alternatively, the condensed acid containing titanium provides a radiation-sensitive material having the ability to form a uniform coating film by a wet coating method.

Further, an example of a pattern forming method by the two-layer resist method using the material of the present invention will be described. An organic polymer film is formed as a lower layer and a coating film of the material of the present invention is formed as an upper layer. A desired pattern is formed on this coating film by using the linography technique. The pattern can be transferred by oxygen plasma etching the lower organic polymer film using the upper coating film having strong resistance to oxygen plasma as an etch mask.

〔Example〕

 Hereinafter, details of the present invention will be specifically shown in Examples.

Example 1. A condensed acid containing tungsten and niobium was synthesized by the method shown below. 8.82 g of metallic tungsten powder and 1.26 g of niobium carbide powder are collected, mixed and transferred to a beaker, to which 70 ml of a 15% H ₂ O ₂ aqueous solution is added. When the vigorous reaction accompanied by foaming had almost ended, about 15 ml of 30% H ₂ O ₂ aqueous solution was added and left at room temperature. Almost all contents dissolve, giving a pale yellow acidic solution. Insoluble or undissolved components are removed by filtration to give a clear solution. A platinum net with platinum black is immersed in this to decompose unreacted H ₂ O ₂ and then dried at room temperature to 120 ° C. to obtain a yellow, amorphous solid. This material, as a result of elemental analysis and thermogravimetric _{analysis, (1-x) WO 3} · x / 2Nb 2 O 5 · yH 2 O 2 · zH 2 O · mCO 2 ( where, x ≒ 0.2, 0 <y1, It was found that the empirical formula is 0.16 <z <4,0 <m0.06). Here, y, z, and m are not constant values, but are shown as ranges, such as the standing time in the synthesis process, the drying conditions, the degree of removal of excess H ₂ O ₂ , or the storage atmosphere after obtaining the solid. This is because y, z, and m change depending on conditions such as humidity that are difficult to control.

One part by weight of the thus obtained condensed acid containing tungsten and niobium was dissolved in one part by weight of water, and ethoxyethanol was added thereto to prepare a photosensitive solution. This photosensitive solution was spin-coated on a silicon wafer having an oxide film formed thereon and dried to form a coating film of about 0.1 μm. continue,
This substrate was exposed for 1 second at a distance of 35 cm from the lamp through a chromium mask using a 600 W xenon mercury lamp.
After exposure, the film was developed with a pH 2 sulfuric acid aqueous solution and the unexposed portion of the photosensitive film was dissolved and removed. As a result, a repeating pattern of 0.5 μm wide lines and 0.5 μm wide spaces was formed.

Examples 2 to 5. Condensation containing niobium having different Nb: (W + Nb) molar ratios in the condensed acid by the same method as described in Example 1 while changing the mixing ratio of the metal tungsten powder and the niobium carbide powder. Four kinds of acids were synthesized. These are shown in Table 1. A photosensitive solution similar to that in Example 1 was prepared using these condensed acids, and 0.5 μm was prepared by the same method as in Example 1.
m repeating patterns were formed. The minimum exposure time required for pattern formation is also shown in Table 1.

The comparative example in Table 1 is a condensed acid of only tungsten synthesized by the same method as in Example 1 from only metallic tungsten powder. In this case, an exposure time of 90 seconds was required to obtain a line / space repeating pattern of 0.5 μm, whereas the light-sensitive materials made of condensed acids containing Nb in Examples 1 to 5 of the present invention had 0.8 to 1.5 seconds. Exposure time is enough,
The sensitivity improving effect of Nb is clear.

An attempt was made to synthesize a condensed acid of niobium alone containing no tungsten, but it could not be obtained by the same method as in Example 1.

Example 6. Metallic tungsten powder 8.82 g and metallic niobium powder 1.1
1 g was collected, and the same synthetic procedure as in Example 1 was performed thereafter to obtain a condensed acid containing no carbon and containing tungsten and niobium. This infrared spectrum is almost the same as the condensed acid of Examples 1 to 5 containing carbon except that the carbon-based band at 1300 to 1400 cm ⁻¹ is not present, and the basic structure of the condensed acid is carbon. It seems that it does not matter whether or not.

A photosensitive solution was prepared in the same manner as in Example 1 from this carbon-free condensed acid. Further, in the same manner as in Example 1, 0.5
A line / space pattern of μm could be formed. The exposure time required for patterning was about 1 second, which is the same as the sensitivity of Example 1 containing carbon.

Example 7. Tungsten carbide powder 9.40 g and niobium carbide powder 1.2.
A condensed acid containing tungsten and niobium was synthesized from 6 g in the same manner as in Example 1. In this condensed acid, C: (W + N
It was found that the molar ratio of b) was 0.25. This coating film was exposed and developed in the same manner as in Example 1 to obtain a good negative pattern. The exposure time required to obtain the pattern was about 1 second.

2 parts by weight of the thus-obtained condensed acid containing peroxo was dissolved in 1 part by weight of water to prepare a photosensitive solution. This photosensitive liquid
A silicon wafer having an oxide film formed thereon was spin coated and dried to form a coating film of about 0.3 μm. When this coating film was exposed and developed in the same manner as in Example 1,
The same results as in Example 1 were obtained.

Example 8. The coating film of condensed acid containing tungsten and niobium obtained in Example 1 was irradiated with an electron beam (accelerating voltage) at an irradiation dose of 1 × 10 ⁻⁵ C / cm ^2.
20 kV). After irradiation, it was developed with a mixed solvent of water and isopropyl alcohol (9: 1, volume ratio) to obtain a good negative pattern.

Example 9. A coating of the condensed acid containing peroxo obtained in Example 6 with 2 ×
Electron beam drawing was carried out at an irradiation dose of 10 ^-5 C / cm ² , and the same development treatment as in Example 8 was carried out to obtain a good negative pattern.

Embodiment 10. First, as shown in FIG. 1 (a), there is a step on the surface.
An Al film 2 as a film to be processed was formed on the Si substrate 1. The lower organic polymer film layer 3 for flattening the step is formed by spin-coating a deep-ultraviolet resist polymethylmethacrylate (manufactured by DuPont, trade name Elvasite 2041) and heating at 160 ° C. for 30 minutes. did. On the other hand, a solution obtained by dissolving 2 parts by weight of a condensed acid containing tungsten and niobium in 1 part by weight of water, obtained in the same manner as in Example 1, was spin-coated to form a resist upper layer 4 composed of a condensed acid coating film having a thickness of 0.1 μm.
Was formed. Thereafter, this substrate was exposed for 1 second at a distance of 50 cm from the lamp using a 600 W Xe-Hg lamp, a filter that passed light having a wavelength of 280 to 330 nm and a chrome mask. After the exposure, the photosensitive film in the unexposed area was dissolved and removed by developing with a developing solution containing dilute sulfuric acid having a pH of 2 to form a desired resist pattern 4'shown in FIG. 1 (b). Then, using the resist pattern 4'as an exposure mask, the lower layer polymethylmethacrylate was exposed with light having a wavelength of 200 to 300 nm. After the exposure, the polymethylmethacrylate layer was developed with chlorobenzene, and as shown in FIG. 1 (c), patterns 3'and 4'having a good dimensional accuracy and good shape could be formed.

Example 11. Instead of the polymethylmethacrylate of Example 10, a novolac resin-diazonaphthoquinone-based resist (trade name AZ1350J) was used as the organic polymer film 3, spin-coated, and heated at 200 ° C. for 1 hour. A lower layer was formed. On the other hand, 2 parts by weight of the condensed acid containing tungsten and niobium obtained in Example 7 was dissolved in 1 part by weight of water, and ethyl cellosolve was added thereto and spin-coated to form an upper layer resist 4 consisting of a condensed acid coating film of 0.1 μm in thickness. Was formed. Then, in the same manner as in Example 10, the lower novolac resin film was removed by reactive sputter etching using oxygen gas, using the pattern 4'shown in FIG. 1 (b) as an etch mask. As a result, as shown in FIG. 1 (c), it was possible to form patterns 3'and 4'having a good shape with high dimensional accuracy.

Example 12. Silicon wafer for semiconductor device Wiring material Prepared by vapor deposition of aluminum. The condensed acid aqueous solution containing tungsten and niobium obtained in Example 1 is spin-coated on the substrate wafer. X-ray exposure is performed through the X-ray mask. X
The heat source is a rotating anticathode type of molybdenum target,
Electron acceleration voltage is 20kV and tube current is 500mA. X-ray dose is 1
It was exposed at 00 mJ / cm ² . Next, water / isopropyl alcohol = 1/3 was used for the developing solution, and development was performed for 30 seconds to form a resist pattern. Then, reactive ion etching of aluminum was performed after post-baking at 100 ° C. for 20 minutes. BCl ₃ is used as the etching gas, and the applied voltage is 500 W
Is. Next, the resist was washed away with water to obtain an aluminum wiring pattern.

According to the embodiment, with X-ray exposure, with practical sensitivity,
A fine pattern of condensed acid resist can be formed,
Using this as a mask, aluminum wiring can be processed with high precision.

Example 13. Photoresist on a silicon wafer coated with PSG (silicon glass containing phosphorus) film as a semiconductor element insulating material
AZ1350J is applied to a thickness of 2 μm and baked at 200 ° C. for 30 minutes. Next, the condensed acid aqueous solution obtained in Example 1 is spin-coated. Then, X-ray exposure and development are performed by the method described in Example 12 to form a condensed acid resist pattern. Next, using the resist film as a mask, the underlying AZ
1350J is etched by oxygen RIE (Reactive Ion Etching). Next, using the AZ1350J as a mask, the PSG in the lower layer is etched by RIE. The etching reaction gas was CHF ₃ + O ₂ (4%), and the applied power was 500 W.
After removing the condensed acid film by washing with water, AZ1350J is removed by oxygen plasma ashing.

According to this example, it is possible to provide a highly accurate two-layer resist method due to the high resolution of the condensed acid resist against X-ray exposure and the excellent resistance to oxygen ion etching.

Example 14. 70 ml of 15 in a mixture of 9.93 g of metallic tungsten powder (average particle size 1 μm) and titanium carbide powder (average particle size 1 μm).
% H ₂ O ₂ aqueous solution to add strong acidity. A platinum net with platinum black is immersed in this to decompose and remove excess H ₂ O ₂ and then dried to obtain a reddish brown, amorphous (amorphous) solid. The substance was a peroxo-condensed acid containing tungsten and titanium as metal element components, and the molar ratio of Ti: (Ti + W) was 0.1. In the infrared spectrum, in addition to the absorption band derived from water molecules, the wave number is 1340 cm ^-1 , 970 cm ^-1 , 880 cm ^-1
And a characteristic absorption band was observed at 550 cm ^-1 . When this solid was decomposed by heating, oxygen was released, and it was found that the solid contains a peroxo group. The Raman spectrum of the aqueous solution of this solid has a wave number of 965 cm ^-1 , 880 cm ^-1 , 610 cm ^-1 and 560 cm ^-1.
A characteristic scattering signal was observed at cm ^-1 .

A photosensitive solution was prepared by dissolving 1 part by weight of a peroxy-condensed acid containing the thus obtained tungsten and titanium as metal element components in 3 parts by weight of water. This photosensitive solution is spin-coated on a silicon wafer with an oxide film formed on top, dried and
A 0.1 μm coating film was formed. Then, this board 600W
Was exposed for 5 seconds through a chromium mask at a distance of 35 cm from the lamp using a xenon-mercury lamp. PH2 after exposure
When the unexposed portion of the photosensitive film was dissolved and removed by developing with an aqueous solution of sulfuric acid, a repeating pattern of 0.5 μm wide lines and 0.5 μm wide spaces was formed.

Example 15. A coating film of peroxo-condensed acid containing tungsten and titanium as metal element components, which was obtained by the same method as in Example 14, was applied at 20 μc / cm ^2.
The electron beam (accelerating voltage 30 kV) with the intensity of was irradiated. This is pH
Development was carried out with an aqueous solution of sulfuric acid of 2 to obtain a good negative pattern.

Example 16. 180 mJ / cm ² was applied to a coating film of a peroxo-condensed acid containing tungsten and titanium as metal element components, which was obtained in the same manner as in Example 14.
Was irradiated with X-rays (MoL rays). This was developed with a sulfuric acid aqueous solution having a pH of 2 to obtain a good negative pattern.

Examples 17 to 19. By changing the compounding ratio of the metal tungsten powder and the titanium carbide (provided that the total mole number of both is 0.06 moles), the Ti: (W + Ti) mole ratio is changed by the same method as in Example 14. 0.05 (Example 17), 0.2 (Example 18), and 0.3
A condensed acid containing tungsten and titanium as metal element components was obtained (Example 19).

These coating films were prepared in the same manner as in Example 14. This was exposed with a 600 W xenon-mercury lamp at a distance of 35 cm and developed with a pH 2 developer to obtain a good negative pattern.
The minimum exposure time required to obtain a negative pattern was as follows.

In Table 2, Comparative Examples are peroxo-condensed acids containing no Ti and having only tungsten as the metal element component.
From this result, the effect of containing titanium is clear.

Example 20. 9.93 g of metallic tungsten powder and metallic titanium powder (particle size
(1.0 μm) 0.287 g of the mixture was dissolved in 70 ml of 15% H ₂ O ₂ aqueous solution, and then a reddish brown amorphous solid was obtained in the same manner as in Example 14. The infrared spectrum of this material is 1340 cm
It was in agreement with the spectrum of the solid of Example 14 except that there was no ^-1 band. Therefore, this substance is a peroxo-condensed acid containing tungsten and titanium as metal element components and does not contain carbon as a hetero atom.

A coating film of this substance was prepared in the same manner as in Example 14, and exposed and developed in the same manner to obtain a good negative pattern. The required minimum exposure time for obtaining the pattern was 6 seconds. Therefore, it is clear that the peroxo-condensed acid containing the heteroatom carbon-free tungsten and titanium as the metal element components exhibits the same photosensitivity as that containing carbon.

Example 21. Polyimide-based polymer resin formed on a silicon substrate by the same method as in Example 14 (Hitachi Chemical Co., Ltd., trade name)
A photosensitive film of peroxo-condensed acid containing tungsten and titanium as metal element components was formed on the upper layer of the (PIQ) film (1.5 μm thick). This was exposed and developed in the same manner as in Example 14 to form an inorganic resist pattern at 0.5 μm intervals on the lower resin film. Subsequently, when oxygen ion etching was performed for 1 hour under the conditions of 100 W and oxygen pressure of 10 ⁻³ Torr, the upper layer inorganic resist pattern was transferred to the lower layer resin, and PIQ patterns at 0.5 μm intervals were obtained.

Example 22. Tungsten and niobium were obtained by dissolving 9.9 g of metal tungsten powder, 0.63 g of niobium carbide powder and 0.36 g of titanium carbide powder in 70 ml of 14% H ₂ O _{2 in} the step of synthesizing the peroxo-condensed acid of Example 14. , And a peroxo-condensed acid containing titanium as a metal element component were synthesized. The molar ratios of niobium and titanium in the metal element were each 0.1. 1 part by weight of the thus obtained peroxo-condensed acid was dissolved in 3 parts by weight of water to obtain a photosensitive composition. This is spin coated on a silicon wafer to form a coating film with a thickness of 0.1 μm,
Example 14 was exposed for 5 seconds by the same method and developed, and as a result, the same fine pattern as in Example 14 was obtained.

Example 23. The photosensitive film described in Example 14 was developed with the following developer. The above exposed sample was immersed by using a mixed solution of a sulfuric acid aqueous solution (A) having a pH of 2 containing 0.49 g of H ₂ SO ₄ in 1 and an aqueous solution containing 12 g of acetic acid and 15 g of sodium acetate in 1 (B). Then, the unexposed portion was dissolved to form a resist pattern.
The residual film ratio of the resist pattern (the ratio of the film thickness after development to the film thickness before development) when using a developing solution in which A and B were mixed at various volume ratios, the rise of the resist pattern from the substrate, and the angle The changes are shown in Table 3.

From the above table, the effect of improving the contrast of the resist pattern by adding sodium acetate to the developing solution is clear.

〔The invention's effect〕

As described above in detail, according to the present invention, a highly sensitive inorganic resist thin film can be formed by a simple and inexpensive wet coating method, and its industrial value is high.

[Brief description of drawings]

FIG. 1 is a process chart for explaining the process of the two-layer resist method according to the present invention. 1 ... Si substrate, 2 ... Al film, 3 ... lower layer of organic polymer film,
3 '... Lower layer pattern, 4 ... Condensed acid coating upper layer, 4' ...
Upper pattern.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuichi Kudo 1-280 Higashi Koigakubo, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Fumio Murai 1-280 Higashi Koigakubo, Kokubunji, Tokyo Hitachi Ltd. (72) Inventor Shinji Okazaki, 1-280 Higashi Koigakubo, Kokubunji, Tokyo, Hitachi, Ltd. Central Research Institute, Ltd. (72) In Katsumi Miyauchi, 1-280, Higashi Koigakubo, Kokubunji, Tokyo Hitachi Research Institute, Ltd. In-house (56) Reference JP-A-61-273539 (JP, A)

Claims (3)

[Claims] 1. A radiation sensitive material comprising a condensed acid containing tungsten and at least one of niobium and titanium. 2. The condensed acid has the general formula (However, x, y, z, l and m are respectively 0 <x + 1 <1,0
<Y1,0.16 <z <4.0m is a value in the range of 0.25)
The radiation-sensitive material according to claim 1, which is a peroxo-condensed acid represented by: 3. The value of x + l in the above general formula is 0 <x + l0.
The radiation-sensitive material according to claim 2, which has a range of 5.