Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
1999-12-14
2002-03-26
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S320000, C430S330000, C065S017500
Reexamination Certificate
active
06361927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating a grating pattern.
2. Discussion of Related Art
An optical pick-up unit is an element, which is constructed of a semiconductor laser, an object lens, an optical diode converting an optical signal into an electrical signal, and an actuator. This is also called an optical head as it becomes small. The optical head is divided into a separation type which generally names the optical pick-up unit including optical systems, a one-body type in which the object lens, actuator and optical elements are mounted on a single base, and a hologram laser in which a prism is replaced by a flat hologram (grating).
The optical pick-up unit is used in the appliances using optical disks such as CD-ROM player, optical magnetic disk, video CD, and MD, as well as the audio field like CD player. Furthermore, there is growing demand for the optical pick-up unit for DVD. Currently, optical pick-up elements become small, thin, light and high-speed.
FIGS. 1A
,
1
B,
1
C and
1
D are cross-sectional views showing a conventional method of fabricating a grating pattern. Referring to
FIG. 1A
, a silicon oxide layer
11
is deposited on a glass substrate
10
by sputtering process, photoresist is coated thereon by spin coating method and heat treatment is performed, to form a photoresist layer
12
. Referring to
FIG. 1B
, exposure is carried out through a mask
13
in order to fabricate a grating pattern. Referring to
FIG. 1C
, exposed photoresist layer
12
is developed, and silicon oxide layer
11
is selectively etched by 15:1 buffered oxide etchant(BOE) using the photoresist layer as a mask. Referring to
FIG. 1D
, the photoresist used as the mask is developed to form silicon oxide layer pattern
11
, thereby fabricating the grating pattern.
FIGS. 2A
,
2
B,
2
C and
2
D are cross-sectional views showing another conventional method of fabricating a grating pattern. Referring to
FIG. 2A
, photoresist is coated on the glass substrate
20
by spin coating method and heat treatment is performed, to form a photoresist layer
21
. Referring to
FIG. 2B
, photoresist layer
21
is exposed through a mask
22
in order to form a grating pattern. Referring to
FIG. 2C
, exposed photoresist layer
21
is developed, and a silicon oxide layer
23
and
23
′ is deposited by sputtering process. Referring to
FIG. 2D
, photoresist is coated on the silicon oxide layer
23
and
23
′, silicon oxide layer
23
′ formed on the photoresist layer
21
is etched using 15:1 BOE by masking process, and the photoresist layer (not shown) which was coated on the silicon oxide layer
23
and used as the mask is developed to form silicon oxide layer pattern
23
, thereby fabricating the grating pattern.
In the above-mentioned conventional methods of fabricating the grating pattern, however, the silicon oxide layer is not uniformly deposited over the entire glass substrate because it is formed by sputtering process. That is, its thickness at the center of the substrate is different from that at the peripheral region. Furthermore, the fabrication of the silicon oxide layer requires an expensive vacuum apparatus, deteriorating productivity.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for fabricating a grating pattern in which SOG solution is coated on a glass substrate by spin-coating method and heat-treated to easily form a silicon oxide layer.
In order to achieve the above object of the present invention, the present invention provides a method for fabricating a grating pattern, including the steps of: coating an SOG solution on a glass substrate by spin coating method; heat-treating the SOG thin film coated on the glass substrate, to form a silicon oxide layer; coating a photoresist on the silicon oxide layer and exposing the photoresist layer by masking process; developing the exposed photoresist layer and wet-etching the silicon oxide layer; and developing the photoresist layer used as a mask.
The SOG thin film is heat-treated at a temperature of 80-170° C. The silicon oxide layer has a wet etch selectivity to the glass substrate of above 100:1, and its refractive index varies according to a gas atmosphere for the heat treatment. The silicon oxide layer is a multilevel silicon oxide layer, which is fabricated in such manner that the heat treatment is repeated at the temperature range of 80-170° C., carrying out from a high temperature to a low temperature (each heat treatment being conducted a lower temperature than the prior treatment). Also, the silicon oxide layer pattern is formed a step shape by one-time wet etching.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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patent: 6249335 (2001-06-01), Hirukawa et al.
patent: 04-206820 (1992-07-01), None
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KR 9501841B (abstract only), Mar. 1995.*
Elliott, D.J., “Integrated Circuit Fabrication Technology”, pp. 250-254 &260, 1982.
Angebranndt Martin
Dykema Gossett PLLC
Havit Co., Ltd.
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