JPH05181280A - Resist - Google Patents

Abstract

PURPOSE:To provide a resist having excellent dry etching resistance as well as photosensitivity and capable of forming a fine high accuracy pattern by alkali development. CONSTITUTION:This resist is prepd. with polysilane represented by formula I or 11. In the formulae I, II, each of R1-R14 is hydroxyl, H, vinyl, alkyl, alkoxy or an arom. group, at least one of R1-R5 is hydroxyl and at least one of R6-R12 is hydroxyl.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist suitable for use in a multi-layer resist system.

[0002]

2. Description of the Related Art In the field of electronic parts, such as semiconductor integrated circuits, which require various types of fine processing, patterns have been widely formed using resists. As such a pattern forming method, conventionally, for example, a so-called single-layer resist method in which only one resist film is formed on a wafer has been generally used. In the manufacture of semiconductor integrated circuits, however, the minimum processing size has been reduced year by year, and various problems have been pointed out regarding this single-layer resist method.

That is, in the semiconductor integrated circuit, the vertical dimension is not reduced so much as compared with the horizontal dimension, so that the ratio of the height to the width of the resist pattern must be large. Therefore, it has become more difficult to suppress the dimensional change of the resist pattern on the wafer having a complicated step structure as the pattern becomes finer.

Further, in various exposure methods, another problem has arisen with the reduction of the minimum size. For example, in light exposure, the interference effect of reflected light due to a step on the semiconductor substrate has a great influence on dimensional accuracy. on the other hand,
In the electron beam exposure, there is a problem that the height-to-width ratio of a fine resist pattern cannot be increased due to the proximity effect caused by backscattering of electrons.

As one method for solving the above-mentioned problems,
Multilayer resist systems have been developed. For such a multilayer resist system, see Solid State Technology 74 (1981) [Solid State Technology 74 (198).
1)], but many other studies have been published on this system. At present, a method that has been generally tried in many cases is a three-layer resist system, which is used for flattening the steps of a semiconductor substrate and for preventing reflection from the substrate, and for etching the bottom layer. And an uppermost layer as a photosensitive layer.

However, although the above three-layer resist system has an advantage that fine patterning can be performed as compared with the single-layer resist method, it has a problem that the number of steps until pattern formation is increased. That is, de
Since there is no resist that satisfies both the sensitivity to radiation such as epUV and the resistance to reactive ion etching by oxygen plasma (oxygen RIE resistance), these functions are provided in separate layers. There is a problem that the number of processes increases.

[0007]

As described above, in the conventional multi-layer resist system, there is no resist satisfying both photosensitivity and oxygen RIE resistance. Therefore, it is necessary to separately form layers having these functions. Therefore, there is a problem that the number of steps until pattern formation is increased.

An object of the present invention is to solve the above problems and to provide a resist having photosensitivity and excellent dry etching resistance and capable of forming a fine and highly precise pattern by alkali development.

[0009]

Means and Actions for Solving the Problems The present invention, which has been made to achieve the above object, is a resist comprising polysilane represented by any one of the following general formulas [1] and [2]. That is, the resist of the present invention is characterized by being composed of polysilane in which an aryl group having a phenolic hydroxyl group is introduced into a side chain.

[0010]

[Chemical 2] (In the formula, R _{1 to} R ₁₄ are selected from a hydroxyl group, hydrogen, a vinyl group, an alkyl group, an alkoxy group or an aromatic group, and at least one of R _{1 to} R ₅ and R _{6 to} R ₁₂ At least one is a hydroxyl group.) In the resist of the present invention, the polysilane is decomposed by irradiation with energy rays such as light, electron beams, and X-rays, and thus the energy-irradiated portion is selectively dissolved by a developing solution. It functions as a positive resist to be removed.

In the present invention, the molecular weight of the above polysilane is preferably in the range of 500 to 500000, particularly 1000 to 30000 from the viewpoint of solubility and sensitivity. Such polysilane can be easily obtained by reacting dichlorosilane having a phenolic hydroxyl group protected by silyl ether with metallic sodium in xylene, and is synthesized by, for example, the following method. After protecting the hydroxyl group of m-phenoldichlorosilane with a trimethylsilyl group and reacting with sodium metal in toluene or xylene, the protective group is solvolytically decomposed in methanol to introduce a phenyl group having a phenolic hydroxyl group into the side chain. The obtained polysilane is obtained. In the present invention, such polysilane is used alone or in the form of a mixture.

Next, a pattern forming method using the resist of the present invention will be described.

First, after applying a flattening agent on a substrate, it is dried at usually 50 to 250 ° C., preferably 80 to 220 ° C. for 0.5 to 120 minutes, preferably 1 to 90 minutes to form a flattening layer having a desired thickness. Form. Examples of the substrate used here include a silicon wafer, a silicon wafer having various insulating films, electrodes, wirings and the like formed on the surface thereof and having a step, a blank mask and the like. The leveling agent may be any one as long as it has such a purity that it does not hinder the manufacturing of semiconductor integrated circuits and the like. Examples of such a leveling agent include positive resists composed of substituted naphthoquinonediazide and novolac resin, polystyrene, polymethylmethacrylate, polyvinylphenol, novolac resin, polyester, polyvinyl alcohol, polyethylene, polypropylene, polyimide, polybutadiene, polyvinyl acetate and polyvinyl. Butyral and the like can be mentioned. These resins are used alone or in the form of a mixture.

Then, a resist solution prepared by dissolving the resist of the present invention in an organic solvent is applied onto the flattening layer, and then at 50 to 200 ° C., preferably 80 to 120 ° C. for 0.5 to 120 minutes, preferably 1 to 60. The film is dried for a minute to form a resist film having a desired thickness. Examples of the organic solvent used at this time include toluene, xylene, o-dichlorobenzene, chloroform, ethanol, i-propyl alcohol, cyclopentanone, cyclohexanone, methyl cellosolve, ethyl cellosolve acetate, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate. Etc. These organic solvents may be used alone or in the form of a mixture. As the coating means, for example, a spin coating method using a spinner, a dipping method, a spraying method, a printing method or the like can be adopted. The thickness of the resist film can be arbitrarily adjusted by the coating means, the polysilane concentration in the resist solution, the viscosity, and the like.

Then, by exposing a desired portion of the resist film on the planarizing layer, the exposed portion becomes more soluble in a developing solution such as an alkaline aqueous solution than the unexposed portion. This exposure is performed by irradiating energy rays such as visible, infrared, and ultraviolet rays or electron rays according to a conventional method, and the optimum exposure amount at the time of exposure depends on the kinds of components constituting the resist film, Usually, the range of 1 mJ / cm ² to 10 J / cm ² is preferable. For exposure, either contact exposure or projection exposure can be used. Then, the exposed portion of the resist film is dissolved and removed by developing the resist film exposed with a developing solution such as an alkaline aqueous solution or an organic solvent to form a desired pattern. Before such development processing, for example, on a hot plate at 50 to 120 ° C., 0.5 to
The heat treatment may be carried out for about 15 minutes, while after the development treatment, the heat treatment is usually carried out at 50 to 120 ° C. for about 0.5 to 120 minutes. As the above-mentioned alkaline aqueous solution used in the development treatment, specifically, tetramethylammonium hydroxide, an organic alkaline aqueous solution such as choline or sodium hydroxide, an inorganic alkaline aqueous solution such as potassium hydroxide, and the like, an organic solvent Examples of such are acetone and the like.
The alkaline aqueous solution as described above is preferably used at a concentration of 15% by weight or less, and the developing method is a dipping method,
The spray method is not particularly limited.

Next, the flattening layer exposed by using the formed pattern as a mask is etched using oxygen gas plasma or a suitable solvent. At this time, more preferable is an oxygen reactive ion etching method (oxygen RIE method) using oxygen gas plasma, and in this case, usually 1 × 10 5 is used.
^-4 to 1 × 10 ^-1 Torr, 0.01 to 10 w / cm ² for 1 to 120 minutes. At this time, the pattern formed using the resist of the present invention is exposed to oxygen RIE to form silicon dioxide (SiO ₂ ) or a film similar thereto on the surface layer, and the exposed flattening layer 10 to 10 100 times more oxygen resistant RIE
To have sex. Therefore, the flattening layer portion exposed from the pattern is selectively removed by the oxygen RIE method, and the optimum pattern profile is obtained.

Finally, the substrate is etched by using the pattern thus obtained as a mask. As the etching means, a wet etching method or a dry etching method is adopted, but a dry etching method is preferable when forming a fine pattern of 3 μm or less. As the wet etching agent, a hydrofluoric acid aqueous solution, an ammonium fluoride aqueous solution or the like is used when the silicon oxide film is an etching target, and a phosphoric acid aqueous solution, an acetic acid aqueous solution, a nitric acid aqueous solution or the like is used when the aluminum is an etching target, When the chromium-based film is to be etched, an aqueous solution of cerium ammonium nitrate or the like is used. As the dry etching gas, CF ₄ , C ₂ F ₆ , CCl ₄ , B is used.
Examples include Cl ₃ , Cl ₂ , HCl, H _{2 and the} like. These gases are used in combination as required. The etching conditions are, based on the combination of the type of material used to form the fine pattern and the resist used, the concentration of the wet etching agent in the reaction tank, the concentration of the dry etching gas, the reaction temperature, and the reaction time. Etc., but the method is not particularly limited.

After the above-mentioned etching, a pattern formed using the flattening layer remaining on the substrate and the resist of the present invention is used as a pattern, for example, manufactured by Nagase Kasei Co., Ltd., trade name: J-10.
It is removed by a stripping agent such as 0, oxygen gas plasma, or the like.

In addition to the steps described above, it does not matter at all that additional steps may be added depending on the purpose. For example, in order to improve the adhesion between the resist film and the flattening layer or the flattening layer and the substrate made of the resist of the present invention, a pretreatment step performed before the application of each liquid, the developer is removed after the development of the resist film. Examples include a rinsing step performed for the purpose and an ultraviolet ray re-irradiation step performed before dry etching. In the above, the case of using the resist of the present invention in a multi-layer resist system has been described, but the resist of the present invention can also be used as a conventional single layer resist.

Further, in the resist of the present invention, in order to improve storage stability, a thermal polymerization inhibitor, an antihalation agent for preventing halation from the substrate, and an improvement in adhesion to the substrate, if necessary. Adhesion improvers, ultraviolet absorbers, surfactants, sensitizers and other additives, and alkali-soluble resins other than the above polysilanes may be added.

[0021]

【Example】

Example 1 A solution of novolac resin in cellosolve acetate was applied onto a silicon wafer with a spinner and dried at 220 ° C. for 1 hour to form a planarizing layer having a thickness of 2.0 μm. Then, 20 parts by weight of polysilane represented by the following structural formula [3] is dissolved in 450 parts by weight of cyclohexanone to prepare a resist solution, which is applied onto the planarizing layer with a spinner and dried at 90 ° C. for 2 minutes. To form a resist film having a thickness of 0.4 μm.

Next, a predetermined region of the resist film is 313
nm monochromatic light, then developed with a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 45 seconds,
The desired pattern was formed by drying at 200 ° C. for 30 minutes. Then, using this pattern as a mask, the exposed flattening layer is etched using oxygen gas plasma (2.0 × 10
^-2 Torr, 0.06W / cm ² ) for 30 minutes,
A highly precise pattern with a line width of 0.6 μm was formed.

[0023]

[Chemical 3] Example 2 After forming a planarization layer on a silicon wafer in the same manner as in Example 1, a resist solution similar to that in Example 1 was prepared except that polysilane represented by the following structural formula [4] was used, This was applied onto the flattening layer with a spinner and dried at 90 ° C. for 2 minutes to form a resist film having a thickness of 0.3 μm.

Next, a predetermined region of the resist film is exposed 365 times.
nm monochromatic light, then developed with a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 45 seconds,
The desired pattern was formed by drying at 200 ° C. for 30 minutes. Then, using this pattern as a mask, the exposed flattening layer is etched using oxygen gas plasma (2.0 × 10
^-2 Torr, 0.06W / cm ² ) for 30 minutes,
A highly precise pattern with a line width of 0.6 μm was formed.

[0025]

[Chemical 4] Example 3 A solution of 100 g of m-bromophenol in 100 g of THF (tetrahydrofuran) was added to a THF solution of 40 g of trimethylsilyl chloride and 60 g of triethylamine (40
0 g). After the dropping was completed, the reaction mixture was refluxed for 2 hours. Then, the mixture was filtered in a nitrogen atmosphere, THF was distilled off under normal pressure, hexane was added, and the precipitated salt was filtered off again. The filtrate was concentrated and then distilled under reduced pressure (68 ° C / 0.1 mmHg) to obtain m-trimethylsilyloxybromobenzene. (Yield 95%) Next, the above-mentioned m-trimethylsilyloxybromobenzene
24.5 g, methyltrichlorosilane 18 g, metallic magnesium 2.4 g, and THF 200 g were mixed, and iodine was added as a catalyst, followed by heating under reflux. After refluxing for 36 hours to remove insoluble matter by filtration, concentration and distillation under reduced pressure (105 ° C./0.1 mmHg) were carried out to obtain m-trimethylsilyloxyphenylmethyldichlorosilane. (Yield 35%) Next, 27.9 g of a THF solution (60 g) of m-trimethylsilyloxyphenylmethyldichlorosilane was added to a THF solution (60 g) in which 2.3 g of metallic sodium was dispersed.
Dropwise at ° C. After completion of dropping, the mixture was reacted at 110 ° C. for 3 hours, then returned to room temperature and insoluble matter was filtered off. Further, the filtrate was concentrated and then stirred in methanol to synthesize polysilane. Then, the obtained methanol solution of polysilane was dropped into toluene and the insoluble matter was dried to purify the polysilane. (Yield 6.5%) N of polysilane
The MR spectrum is shown in FIG. This confirmed that the polysilane had a structure represented by the following structural formula [5].

[0026]

[Chemical 5] 20 g of this polysilane was added to 80 g of ethyl cellosolve acetate.
To prepare a resist solution, and dissolve it in 2.0 μm, 1.0 μm
After pressure filtration with a filter having a pore size of m, 0.5 μm, and 0.2 μm, a resist film was formed on the silicon wafer with a spinner. Then, after heat treatment at 90 ℃ for 5 minutes,
A pattern was formed by exposing (450 mJ / cm ² ) with a KrF excimer laser stepper (NA; 0.37) and developing with a 3.5 wt% aqueous solution of tetramethylammonium hydroxide.
After that, when the formed pattern was observed, it was 0.325.
It was found to have a steep profile of μm lines and spaces. The heat resistance of this pattern was evaluated by heating it on a hot plate.
It was confirmed that the pattern shape did not deform up to 0 ° C and that it had good heat resistance. Example 4 Polysilane represented by the structural formula [5] (Mw; 8500)
Mw containing 30 g and m-cresol and 3,4-xyresole as an alkali-soluble resin in a molar ratio of 6: 4, 70 g of novolak resin of 8500 was dissolved in 300 m of acetate cellosolve, mixed and stirred to form a resist. A solution was prepared. Then, this solution was filtered in the same manner as in Example 3 and applied on a silicon wafer with a spinner, and then 100
The resist film having a thickness of 1.2 μm was obtained by drying at 5 ° C. for 5 minutes.
After that, the resist film obtained was exposed (230 mJ / cm ² ) using a contact exposure machine using a mercury lamp as a light source, and developed with a 0.79 wt% aqueous solution of tetramethylammonium hydroxide. And a pattern having a steep profile of space was formed. Furthermore, when the pattern was heated on a hot plate, 15
It was confirmed that the pattern shape was not deformed even if it was held at 0 ° C. for 5 minutes, and that it had good heat resistance. Example 5 First, in accordance with the polysilane synthesis method in Example 3,
Polysilane represented by the following structural formula [6] was synthesized (yield 10%). With respect to this polysilane, a resist solution was prepared in the same manner as in Example 3, a resist film was formed on a silicon wafer, and then heat treatment, exposure, and development were sequentially performed to form a pattern. After that, when the formed pattern was observed, it was found that it had a steep profile of lines and spaces of 0.3 μm. Further, when this pattern was heated on a hot plate and its heat resistance was evaluated, it was confirmed that the pattern shape did not deform up to 150 ° C. and that it had good heat resistance.

[0027]

[Chemical 6] Example 6 First, according to the synthesis method of polysilane in Example 3,
A polysilane represented by the following structural formula [7] was synthesized (yield 6.5%). With respect to this polysilane, a resist solution was prepared in the same manner as in Example 3, a resist film was formed on a silicon wafer, and then heat treatment, exposure, and development were sequentially performed to form a pattern. After that, when the formed pattern was observed, it was found that it had a steep profile of lines and spaces of 0.325 μm. Further, when this pattern was heated on a hot plate and its heat resistance was evaluated, it was confirmed that the pattern shape did not deform up to 130 ° C. and that it had good heat resistance.

[0028]

[Chemical 7] Example 7 First, according to the synthesis method of polysilane in Example 3,
Polysilane represented by the following structural formula [8] was synthesized (yield 6.0%). With respect to this polysilane, a resist solution was prepared in the same manner as in Example 3, a resist film was formed on a silicon wafer, and then heat treatment, exposure, and development were sequentially performed to form a pattern. After that, when the formed pattern was observed, it was found that it had a steep profile of lines and spaces of 0.3 μm. Further, when this pattern was heated on a hot plate and its heat resistance was evaluated, it was confirmed that the pattern shape did not deform up to 130 ° C. and that it had good heat resistance.

[0029]

[Chemical 8]

[0030]

As described in detail above, according to the present invention, it is possible to realize a resist which has photosensitivity and is excellent in dry etching resistance, and which enables fine and highly precise pattern formation by alkali development.

[Brief description of drawings]

FIG. 1 is an NMR spectrum diagram of polysilane synthesized in an example of the present invention.

Front Page Continuation (72) Inventor Akiko Hirao 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Toshiba Research Institute, Ltd.

Claims (1)

[Claims] 1. A resist comprising a polysilane represented by any one of the following general formulas [1] and [2]. [Chemical 1] (In the formula, R _{1 to} R ₁₄ are selected from a hydroxyl group, hydrogen, a vinyl group, an alkyl group, an alkoxy group or an aromatic group, and at least one of R _{1 to} R ₅ and R _{6 to} R ₁₂ At least one is a hydroxyl group.)