Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
1999-08-31
2001-10-16
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S312000, C430S323000
Reexamination Certificate
active
06303277
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pattern forming method and a method of manufacturing a device having a fine pattern. The device having a fine pattern represents, for example, a semiconductor device or a recording medium that has a fine pattern and requires a microscopical processing technology for the manufacture thereof.
A lithography technology using photoresist, etc. is widely used nowadays in the technical field requiring a microscopical processing technology as in the manufacture of a semiconductor device. The lithography technology permits forming a relatively fine pattern.
However, the degree of integration of a semiconductor dievice such as DRAM is made higher and the density of a recording medium such as DVD is made higher in recent years. As a result, attentions are paid to the development of a microscopical processing technology of nanometers scale.
In the lithography technology, the resolution can be increased by forming, for example, a resist film very thin. To be more specific, where a resist film formed on a film to be etched is irradiated with light, the photoresist is sensitive to both the incident light emitted from a light source and a reflected light from the film to be etched. The reflected light from the underlying layer runs through an optical path differing from that of the incident light or is scattered within the resist film so as to give an adverse effect to the resolution. The adverse effect is rendered prominent with increase in the thickness of the resist film. Therefore, a high resolution can be achieved by forming the resist film very thin.
For improving the resolution by this method, it is considered most effective to use a monomolecular film, e.g., a Langmuir-Blodget film (hereinafter referred to as LB film), as a resist film. In fact, various researches are being made on the use of an ultra thin film such as a monomolecular film as a resist film.
For example, M. J. Lercel et al. report in “J. Vac. Sci. Technol. B11(6), 2823 (1993)” that a monomolecular film of n-octadecyl trichlorosilane formed on a surface of a SiO
2
substrate or a monomolecular film of n-octadecane thiol formed on a surface of a GaAs substrate was exposed to an electron beam to form a pattern of the monomolecular film. M. J. Lercel et al. also report that a grating having a width of 25 nm was formed by applying a wet etching to the substrate surface using the pattern thus obtained as a mask.
Also, the technology of exposing a monomolecular film to an ion beam is disclosed by P.C. Reike et al. in “Langmuir 10, 619 (1994)” and by G. Gillen et al. in “Appl. Phys. Lett. 65, 534 (1994)”. K. K. Berggren et al. disclose the technology of exposing a monomolecular film to an atomic beam in “Science 269, (1995)”. Further, the technology of exposing a monomolecular film to light using a probe of a scanning probe microscope is disclosed by L. Stockman et al. in “Appl. Phys. Lett. 62, 2935 (1993)”, by S. Yamamoto et al. in “Jpn. J. Appl. Phys. 34, 3396 (1995)”, by C. R. K. Marrian et al. in “Appl. Phys. Lett. 64, 390 (1994)” and by Y. -T. Kim et al. in “Langmuir 8, 1096 (1992)”. It is also reported in each of these documents that a pattern of scores of nanometers scale was formed successfully.
However, it is reported by M. J. Lercel et al. in “J. Vac. Sci. Technol. B11 (6), 2823 (1993)” that an ultra thin film such as a monomolecular film has fine defects and, thus, fails to exhibit a sufficient resistance to etching for using the monomolecular film as an etching mask. Therefore, it was difficult to form a fine pattern with a high resolution by the methods exemplified above.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a pattern forming method that makes it possible to form a fine pattern with a high resolution.
Another object of the present invention is to provide a method of manufacturing a device that makes it possible to manufacture a device having a high density or a high degree of integration with a high accuracy.
According to an aspect of the present invention, there is provided a pattern forming method comprising the steps of forming a first thin film on an object to be etched, forming a first surface region and a second surface region on a surface of the object by modifying or removing a portion of the first thin film, the first and second surface regions differing from each other in the surface state, forming a second thin film on the first surface region by utilizing the difference in the surface state between the first and second surface regions, the second thin film being amorphous and thicker than the first thin film, and etching the object using the second thin film as an etching mask.
According to another aspect of the present invention, there is provided a method of manufacturing a device having a fine pattern, comprising the steps of forming a first thin film on an object to be etched, forming a first surface region and a second surface region on a surface of the object by modifying or removing a portion of the first thin film, the first and second surface regions differing from each other in the surface state, forming a second thin film on the first surface region by utilizing the difference in the surface state between the first and second surface regions, the second thin film being amorphous and thicker than the first thin film, and etching the object using the second thin film as an etching mask, the etched object forming a fine pattern and constituting at least a part of the device.
In the present invention, a first thin film is formed first on a surface of an object to be etched. The first thin film, which is not used as an etching mask, is for forming a first region and a second region differing from each other in the surface state on a surface of the object. Therefore, the first thin film need not be resistant to etching.
Also, the first thin film, which is not used as an etching mask, can be formed very thin like an ultra thin film, making it possible to suppress the adverse effect given by, for example, the reflected light to the resolution. As a result, the first and second regions can be formed with a high resolution.
In the present invention, a second thin film is selectively formed on the first region by utilizing the difference in the surface state between the first and second regions. It is necessary for the second thin film, which is used as an etching mask, to be resistant to etching and to be thicker than the first thin film.
The second thin film is patterned by utilizing the difference in the surface state between the first and second regions. In other words, a light irradiation is not utilized for patterning the second thin film. Also, the first and second regions are formed with a high resolution, as already described. It follows that the second thin film can also be formed with a high resolution.
In the present invention, the second thin film is amorphous. If the second thin film is crystalline, an undesired crystal growth or the like takes place, making it difficult to allow the shape of the second thin film to conform with the shape of the first region. In other words, it is difficult to form the second thin film in a desired pattern.
As described above, the second thin film used as an etching mask can be formed with a high resolution in the present invention. Also, the second thin film is resistant to etching and can be formed thick. It follows that an object can be patterned with a high resolution by etching the object using the second thin film as an etching mask. In other words, the present invention makes it possible to form a fine pattern with a high resolution.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 4174217 (1979-11-01), Flately
pa
Hieda Hiroyuki
Ishino Takashi
Naito Katsuyuki
Tanaka Kuniyoshi
Baxter Janet
Clarke Yvette M.
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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