X-ray or gamma ray systems or devices – Specific application – Lithography
Reexamination Certificate
2002-08-09
2004-06-22
Church, Craig E (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Lithography
Reexamination Certificate
active
06754303
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an exposure apparatus and method utilized in the manufacture of various types of devices, e.g., a semiconductor chip such as an IC or LSI, a display element such as a liquid crystal panel, a detection element such as a magnetic head, and an image sensing element such as a CCD.
BACKGROUND OF THE INVENTION
In recent years, as the packing density and operation speed of semiconductor integrated circuits increase, the pattern line width of the integrated circuits is decreased, and a higher-performance semiconductor manufacturing method is sought for. Accordingly, as an exposure apparatus used for resist pattern formation in the lithography process of the semiconductor fabrication process, a stepper utilizing extreme ultraviolet rays such as a KrF laser (248 nm), an ArF laser (193 nm), or an F
2
laser (157 nm), or a short-wavelength light beam such as X-rays (0.2 to 1.5 nm) has been developed.
In exposure using X-rays, among these light beams, a proximity exposure method of moving an X-ray mask having a desired pattern to be close to a resist-coated wafer, and irradiating the wafer with X-rays through the X-ray mask, thereby transferring the projected image of the mask pattern onto the wafer, has been developed.
In order to obtain high-intensity X-rays, an exposing method using synchrotron radiation is proposed. It is reported that, according to this method, a pattern of 100 nm or less can be transferred. A synchrotron radiation source requires large-scale facilities. A profit cannot be expected unless fabrication is performed by connecting ten or more exposure apparatuses to one light source. Hence, this method is suitable for application to a highly demanded device such as a semiconductor memory. In recent years, a device using GaAs has been put into practical use as a communication device, and a large decrease in line width is required. Communication devices are produced in an amount less than that of semiconductor memories, and many types of communication devices are produced in small amounts. When an X-ray exposure system using synchrotron radiation as the light source is introduced to the fabrication of communication devices, it will probably make no profit. For this reason, an exposure apparatus using a compact X-ray source which generates high-intensity X-rays is used in actual communication device production. The light source is called a laser plasma produced source, and ranges from one which generates a plasma by irradiating a target with a laser beam and uses X-ray beams generated from the plasma, to one which generates X-rays by generating a pinch plasma in a gas. These light sources are called point sources. According to a general exposure apparatus, one exposure apparatus main body which transfers a pattern by aligning a mask and wafer is connected to one point source.
FIG. 3
shows the schematic arrangement of a conventional point source X-ray stepper. Reference numeral
101
denotes an X-ray source unit for generating X-rays. The interior of the X-ray source unit
101
is maintained in a vacuum state. The X-ray source unit
101
irradiates a target
111
with a laser beam (not shown) to generate a plasma, thus generating X-rays
117
. The X-rays
117
globally diverge from a light source
112
. Part of the X-rays
117
is guided into a reduced-pressure He chamber
141
through an X-ray extracting window
113
. A collimator
121
is set in the reduced-pressure He chamber
141
. The collimator
121
sets the incident divergent X-rays to be parallel, and outputs them at an exposure field (reference numeral
118
). The X-rays
117
generated by the light source
112
are divergent light beams. At an exposure position away from the light source
112
, the intensity of the X-rays
117
decreases in inverse proportion to the distance. Hence, to obtain X-rays as much as possible to increase the intensity of the X-rays for exposure is one of the roles of the collimator
121
.
A mask
131
has a transfer pattern on its membrane (not shown). A wafer
132
coated with a photosensitive agent is positioned at a position with a small gap of about 10 &mgr;m from the membrane by an alignment unit (not shown). The wafer
132
is irradiated with the X-rays
118
emerging from the collimator
121
, so the pattern is transferred to the wafer
132
. The wafer
132
is sequentially stepped by a wafer stage
134
and is exposed successively.
The exposure apparatus is mainly comprised of the light source unit
101
and a main body
102
. The X-ray source unit
101
is set on a light source unit frame
115
and is installed on the floor independently of the main body
102
. This prevents heat generated by the light source
112
from being transmitted through the frame to thermally distort the main body
102
, leading to a decrease in alignment precision of the mask
131
and wafer
132
. This also facilitates installation of the apparatus by supporting the X-ray source unit
101
and main body
102
by different structures.
The target
111
is arranged in the X-ray source unit
101
, and is irradiated with a laser beam (not shown) to generate a plasma, thereby generating the X-rays
117
. The interior of the X-ray source unit
101
is a vacuum and is isolated from the reduced pressure He atmosphere of the main body
102
by the Be-made X-ray extracting window
113
with a thickness of several &mgr;m. Thus, the vacuum atmosphere in the X-ray source unit
101
will not be spoiled. Beryllium has a high X-ray transmittance but does not transmit He, so Be is used to form the X-ray extracting window
113
. A bellows A (reference numeral
116
) is set between the X-ray source unit
101
and reduced-pressure He chamber
141
to isolate them from the outside.
The main body
102
is set in the reduced-pressure He chamber
141
, and is entirely maintained with the reduced-pressure He atmosphere by an He atmosphere creating unit (not shown). This is because attenuation of the X-rays can be suppressed by setting the atmosphere where the X-rays as the exposure light pass to reduced-pressure He. The main body
102
is comprised of the collimator
121
of an illumination optical system, a mask stage (not shown) for holding and positioning the mask
131
, the wafer stage
134
for holding, positioning, and stepping the wafer
132
, a transfer system (not shown) for transferring the mask
131
and wafer
132
, and a measurement system (not shown) for measuring the positions of the mask
131
and wafer
132
. The main body
102
is installed on the floor through vibration damping units
136
. A stage surface plate
135
is set on the vibration damping units
136
, and the wafer stage
134
moves on it. A main body frame
137
is set on the stage surface plate
135
, and the collimator
121
is fixed to the main body frame
137
. When the collimator
121
is to be assembled and adjusted, it is built with its position and attitude being adjusted such that the X-rays
118
have a uniform intensity distribution on the mask surface and become incident on the mask
131
to be perpendicular to it.
The vibration damping units
136
prevent the positioning precisions of the mask
131
and wafer
132
, that require precise positioning, from being decreased by vibration from the floor, so the main body
102
maintains a constant attitude. As the vibration damping units
136
are formed of pneumatic springs, it is difficult to remove low-frequency vibration (vibration of several Hertz or less) with them.
Bellows B (reference numeral
142
) are set between the reduced-pressure He chamber
141
and main body
102
so the reduced-pressure He atmosphere will not be spoiled when the attitude of the main body
102
changes.
With the arrangement of the conventional case, when the position of the light source
112
undesirably shifts, its position relative to the collimator
121
of the illumination optical system changes. Then, the X-ray intensity and uniformity on the mask surface, and the exposure optical axis change undesirably. When the X-ray intensity on the mask surf
Canon Kabushiki Kaisha
Church Craig E
Fitzpatrick ,Cella, Harper & Scinto
LandOfFree
Exposure apparatus and exposing method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Exposure apparatus and exposing method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Exposure apparatus and exposing method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3362000