Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
2002-05-30
2004-03-02
Mathews, Alan (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S053000, C355S067000, C355S069000
Reexamination Certificate
active
06700647
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to Korean Patent Application No. 2001-55065 filed on Sep. 7, 2001.
BACKGROUND
1. Technical Field
The present invention relates to an exposure system of a semiconductor wafer and a method for operating the same, and more particularly, to an exposure system of a semiconductor wafer which determines whether a shutter for shutting a light source is fully opened or closed to prevent defects in a photolithographic process.
2. Description of Related Art
A photolithographic process in manufacturing a semiconductor device comprises an exposure process in which a pattern shape of a reticle having predetermined patterns is transferred to a photoresist layer. There are exposure apparatuses such as an aligner for exposing the entire surface of a wafer or a stepper for exposing a partially divided wafer. An exposure apparatus comprises a shutter that controls the transfer of a proper amount of light from an exposure source to a photoresist layer at desired times.
FIG. 1
shows a conventional exposure apparatus of a semiconductor wafer. Referring to
FIG. 1
, the conventional exposure apparatus comprises a light source
10
and a stage
50
for seating a wafer
60
. The light radiated from the light source
10
is transferred to the wafer
60
. The apparatus further comprises a shutter
20
for selectively closing off light radiated from the light source
10
, a reticle
30
having patterns to be transferred to the surface of the wafer
60
, and a lens assembly
40
for reducing and projecting the shape of the reticle
30
.
The shutter
20
, as shown in
FIG. 2A
, comprises a pair of shutters, i.e., a first shutter
22
and a second shutter
24
to rapidly open and close the light source
10
. The first and second shutters
22
and
24
are opened and closed based on operation of first and second cylinders
26
and
28
. FIGS.
2
A~
2
C respectively illustrate a standby state, an open state and a closed state of the first and second shutters
22
and
24
.
When the light source
10
is opened, as shown in
FIG. 2B
, air is supplied to the second cylinder
28
of the second shutter
24
and thus, the second shutter
24
is opened. In such a case, the first shutter
22
is at the standby state.
When the light source
10
is closed, as shown in
FIG. 2C
, the first and second shutters
22
and
24
are simultaneously closed. Since it is faster to simultaneously drive the first and second shutters
22
and
24
than it is to drive only the second shutter
24
, the first and second shutters
22
and
24
are simultaneously driven to rapidly close the light source
10
. After that, the first shutter
22
is returned to an initial position, i.e., the standby state, as shown in FIG.
2
A. Typically, the light source
10
is opened and closed by the second shutter
24
, and the first shutter
22
is driven only to rapidly close the light source
10
.
However, when the first and second cylinders
26
and
28
for driving the shutter
20
are worn or damaged, or when there is damage of an air line for supplying air to the first and second cylinders
26
and
28
, or when bearings for supporting the first and second cylinders
26
and
28
are worn, the shutter
20
may not be fully exposed or closed. Consequently, the light source may not be completely closed or opened as required.
For example, if the shutter
20
is not completely opened during an exposure process, the quantity of transferred light is reduced. Thus, it would be difficult to form a photoresist pattern having a desired shape. If the shutter
20
is not completely closed, a photolithographic process is performed in a state where light leaks from the light source
10
. In such a case, either a photoresist pattern having an undesired shape is formed or no photoresist pattern is formed.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an exposure system of a semiconductor wafer which determines whether a shutter for shutting a light source is completely opened to prevent defects in a photolithographic process.
It is another object of the present invention to provide an exposure system of a semiconductor wafer which checks whether a shutter for shutting a light source is completely closed to prevent defects in a photolithographic process.
It is a further object of the present invention to provide a method for operating the exposure system of a semiconductor wafer.
According to one aspect of the present invention, an exposure system of a semiconductor wafer comprises first and second shutters for opening or closing a light source, a first sensing circuit for sensing a position of the first shutter and for generating a first sensed signal, a second sensing circuit for sensing a position of the second shutter and for generating a second sensed signal, and a controller for determining whether the first and second shutters are completely opened in response to the first and second sensed signals and for generating a control signal when either the first shutter or the second shutter is not completely opened.
According to another aspect of the present invention, a method for operating an exposure system of a semiconductor wafer, the exposure system comprising first and second shutters for closing or opening a light source and first and second cylinders for driving the first and second shutters, the first and second cylinders comprising magnets, is provided. The method comprises the steps of sensing positions of the first and second shutters and generating first and second sensed signals, determining whether the first and second shutters are completely opened, in response to the first and second sensed signals, and performing a warning operation when the first and second shutters are not completely opened, thereby turning off the exposure system.
According to another aspect of the present invention, an exposure system of a semiconductor wafer comprises first and second shutters for selectively opening or closing a light source, a first sensing circuit for sensing the extent of a closed state of the first shutter and for generating a first sensed signal, a second sensing circuit for sensing the extent of an opened state of the first shutter and for generating a second sensed signal, a third sensing circuit for sensing the extent of a closed state of a second shutter and for generating a third sensed signal, a fourth sensing circuit for sensing the extent of an opened state of the second shutter and for generating a fourth sensed signal, and a controller for determining whether the first and second shutters are completely opened or closed, in response to the first through the fourth sensed signals and for generating a control signal when either the first shutter or the second shutter is not completely opened or closed.
According to further aspect of the present invention, a method for operating an exposure system of a semiconductor wafer, the exposure system comprising first and second shutters for closing or opening a light source and first and second cylinders for driving the first and second shutters, the first and second cylinders comprising magnets, is provided. The method comprises the steps of sensing the extent of a closed state of the first shutter to generate a first sensed signal, sensing the extent of an opened state of the first shutter to generate a second sensed signal, sensing the extent of a closed state of the second shutter to generate a third sensed signal, sensing the extent of an opened state of the second shutters to generate a fourth sensed signal, determining whether the first and second shutters are completely opened, in response to the first through fourth sensed signals, and performing a warning operation when the first and second shutters are not completely opened or closed, thereby turning off the exposure system.
These and other aspects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which is to be read in
F. Chau & Associates LLC
Mathews Alan
Samsung Electronics Co,. Ltd.
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