Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2001-02-27
2003-01-28
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S331000
Reexamination Certificate
active
06511792
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for developing a positive-type radiation resist, a process for forming a pattern using a positive-type radiation resist (according to GHOST method, in particular), a process for forming a pattern suitable for preparing a photomask and a process for preparing a semiconductor device in which a pattern is formed by using a positive-type radiation resist. Specifically, it relates to a developing process which are used for forming a pattern on a resist material such as a radio-sensitive resist; a process for forming a pattern, in particular, a process for forming a pattern of a photomask used for forming a micro-pattern of a semiconductor device such as ultra LSI; and a process for preparing a semiconductor device in order to form a micro-pattern of a semiconductor device such as ultra LSI.
In accordance with the increasing demand on the high integration of semiconductor devices, the micro-processing technology is developed. For a successful micro-pattern forming, exposure processes according to ultraviolet ray, X-ray or electron beam (EB) are being proposed. The micro-pattern forming requires a highly precise mask, the pattern of which is formed by using an EB resist. As a positive EB resist for a mask, a resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin is widely used.
A mixed solvent, trade name: ZED-500 available from Nippon Zeon Co. Ltd., comprising diethylketone and diethyl malonate as a developer is mainly used for developing resist. Since this developer is a mixture of the two organic solvents and evaporation amount of each solvent differs from each other during development, there arises a difference in development proceedings, and thus the solution had a defect in critical dimension (CD) uniformity. Also, since the solvents had high solubility against a low exposed area of the resist and resist thickness is largely reduced at the non-exposed area, there was a problem that a highly contrastive pattern is difficult to prepare. The contrast herein refers to normalized residual film thickness at the non-exposed area against exposure dose. The higher the contrast, the larger the resist thickness, and a resist pattern can be formed excellently.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a developing process; a process for forming a pattern, wherein an excellent resist pattern can be formed uniformly on a substrate surface by using positive-type radiation resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin; a process for preparing a photomask; and a process for preparing a semiconductor device.
The present invention is based on the fact discovered by the inventors through intense study for solving the above problem, that a highly contrastive resist pattern can be obtained by using a developer consisting essentially of one particular organic solvent for developing positive-type radiation resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin.
Namely, the present invention relates to:
a developing process comprising using a developer consisting essentially of one organic solvent selected from the group consisting of a ketone having 3 to 8 carbon atoms, a carboxylate ester having 3 to 8 carbon atoms, which may have an alkoxy group, and a dicarboxylate ester having 3 to 8 carbon atoms for developing positive-type radiation resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin (the first invention);
a process for forming a pattern using a positive-type radiation resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin, wherein a developer consisting essentially of one organic solvent selected from the group consisting of a ketone having 3 to 8 carbon atoms, a carboxylate ester having 3 to 8 carbon atoms, which may have an alkoxyl group, and a dicarboxylate ester having 3 to 8 carbon atoms is used (the second invention); and
a process for preparing a semiconductor device comprising a step for forming a resist film on a semiconductor substrate, a step for exposing the resist to be patterned, and a step for developing the resist after the exposure, wherein the resist is a positive-type radiation resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin is used, and wherein a developer consisting essentially of one organic solvent selected from the group consisting of a ketone having 3 to 8 carbon atoms, a carboxylate ester having 3 to 8 carbon atoms, which may have an alkoxyl group, and a dicarboxylate ester having 3 to 8 carbon atoms (the third invention).
Preferably, the developer consists essentially of one organic solvent selected from the group consisting of propyleneglycol monomethylether acetate, 2-pentanone and ethyl-3-ethoxypropionate in the first, second and third inventions, respectively.
The process of the second invention is preferably a process for forming a pattern according to GHOST method. Also, the second invention is suitable for forming a photomask pattern.
DETAILED DESCRIPTION
Embodiment 1
(Developing process)
The first embodiment (Embodiment 1) of the present invention relates to a process for developing a positive-type radiation resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin, wherein a developer consisting essentially of one organic solvent selected from the group consisting of a ketone having 3 to 8 carbon atoms, a carboxylate ester having 3 to 8 carbon atoms, which may have an alkoxy group, and a dicarboxylate ester having 3 to 8 carbon atoms is used.
The organic solvent having more carbon atoms than the above range has an extremely high solubility against a resist causing an increase of dissolution rate at non-exposed area, and therefore, a contrast tends to be decreased while a sensitivity is improved. An organic solvent having less carbon atoms than the above range has extremely low solubility against a resist causing a decrease of a sensitivity and making a development difficult, and therefore, a development tends to take much time.
As a ketone having 3 to 8 carbon atoms, a ketone having 4 to 6 carbon atoms is preferable. Examples thereof are acetone, methyl ethyl ketone, 2-pentanone, 3-methyl-2-butanone, 2-hexanone, 4-methyl-2-pentanone (MIBK), 2-heptanone, diethylketone, 3-hexanone, 3-heptanone, 4-heptanone, cyclohexanone and the like.
As a carboxylate ester having 3 to 8 carbon atoms, which may have an alkoxyl group, a carboxylate ester having 3 to 6 carbon atoms with no alkoxyl group and a carboxylate ester having 5 to 7 carbon atoms with an alkoxyl group are preferable. Examples thereof are methyl acetate, ethyl acetate, n-propyl acetate, butyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, ethyl-3-ethoxypropionate (EEP), propyleneglycol monomethylether acetate (PGMEA), methyl-3-methoxypropionate (MMP), propyleneglycol monoethylether acetate and the like.
As a dicarboxylate ester having 3 to 8 carbon atoms, a dicarboxylate ester having 4 to 8 carbon atoms is preferable. Examples thereof are diethyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, diethyl succinate and the like.
When mass production is considered, it is effective to use a developer consisting essentially of one organic solvent selected from the group consisting of PGMEA, 2-pentanone and EEP from the viewpoints of solubility characteristics, a sensitivity, the price of the solvent and the like.
As a positive-type radiation resist containing a copolymer of an &agr;-methyl styrene compound and an &agr;-chloroacrylate ester compound as a base resin, a positive-type radiation resist having a reaction system such as PMMA can be used. I
Fujino Atsuko
Fukuma Hitoshi
Kumada Teruhiko
Oshida Atsushi
Tange Koji
Duda Kathleen
Mitsubishi Denki & Kabushiki Kaisha
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