Electricity: motive power systems – Positional servo systems – With particular motor control system responsive to the...
Reexamination Certificate
2001-07-06
2003-06-24
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular motor control system responsive to the...
C318S649000, C318S038000, C318S135000
Reexamination Certificate
active
06583597
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains generally to equipment for executing fabrication protocols directed at producing ultraminiature devices such as microelectronic devices, integrated circuits, display matrices, and the like on a substrate such as a semiconductor wafer. More specifically, the invention pertains to holding and moving mechanisms that provide precision movement and positioning of the reticle and/or substrate during execution of a process such as microlithography is performed on the substrate. The stages according to the invention are especially suitable for operation in a vacuum environment in which microlithography is performed using a charged particle beam.
BACKGROUND OF THE INVENTION
In view of the extremely high accuracy and precision required in contemporary fabrication processes performed on semiconductor wafers and other substrates, various configurations of substrate stages (generally termed “wafer stages” herein) have been developed for use in providing high-precision movement and positioning of the substrate. Similar developments also have occurred with respect to reticle stages. The respective configurations often reflect the particular fabrication process and process conditions in which the stages are used. The various configurations also reflect the urgent need to minimize vibration and friction in the stage as much as possible.
An example conventional wafer stage assembly is disclosed in Japan Kôkai Patent Document No. Sho 62-182692. This wafer-stage assembly includes dual guide shafts and is suspended on box-shaped air bearings (gas bearings). An oblique view of the stage assembly
140
is shown in FIG.
30
. The stage assembly
140
includes a base
141
and a pair of box-shaped base guides
142
mounted on the base
141
. Permanent magnetic plates (not detailed) are affixed to the inside surfaces of the base guides
142
, thereby forming respective motor yokes
142
a
. Engaged at the upper portion of each of the two base guides
142
is a respective box-shaped coil bobbin
143
. The motor yokes
142
a
and coil bobbins
143
collectively comprise a first linear motor providing movement of a wafer stage
146
in the X direction. A box-shaped movable guide member
144
extends between the coil bobbins
143
, thereby connecting the coil bobbins together. A permanent magnetic plate (not detailed) is affixed to the inside surface of the movable guide member
144
, thereby forming a motor yoke
144
a
. Engaged at the upper portion of the movable guide member
144
is a box-shaped coil bobbin
145
. The motor yoke
144
a
and coil bobbin
145
collectively comprise as second linear motor providing movement of the wafer stage
146
in the Y direction. The wafer stage
146
is mounted to the coil bobbin
145
.
To form air bearings, air-discharge holes (not shown in
FIG. 30
) are defined on respective surfaces inside the coil bobbins
143
,
145
at locations opposite the respective motor yokes
142
a
,
144
a
. The air bearings are constituted by discharging air from the air-discharge holes into gaps between the coil bobbins
143
,
145
and the respective motor yokes
142
a
,
144
a.
The wafer-stage assembly shown in
FIG. 30
has a configuration in which one movable body (i.e., the guide member
144
and coil bobbin
145
) is situated over the upper portion of the other movable body (i.e., the base guide
142
and coil bobbin
143
). In other words, the movable body constituted by the guide member
144
and coil bobbin
145
is stacked relative to the movable body constituted by the base guide
142
and coil bobbin. With this stacked configuration, the lower movable body must be large to support the upper movable body adequately. Also, the configuration of
FIG. 30
cannot be used in a vacuum because this stage assembly provides no way in which to recover air discharged from the air bearings.
Another conventional wafer stage assembly, disclosed in International application no. WO 99/66221, has a single-shaft configuration that can be used in a vacuum environment. The stage assembly includes a movable body including air-bearing pads. An elevational section of this stage assembly
150
is shown in FIG.
31
and an oblique view of certain details of an air bearing in this stage assembly
150
is provided in FIG.
32
.
The stage assembly
150
is mounted on a surface S of a base
151
. Two C-shaped guide members
152
are mounted to the bench
151
via respective support members
155
. The respective openings in the guide members
152
face each other so as to guide movement of a movable member
153
. The fit of the movable member
153
in the openings of the guide members
152
allows a small gap between the movable member
153
and the inside surfaces of the openings. The gap provides an air bearing between the movable member
153
and the guide members
152
. A wafer stage
161
is mounted to an upper surface of the movable member
153
. A wafer
163
or other suitable substrate is mounted to the wafer stage
161
.
The lower surface of the movable member
153
is mounted to a moving member (armature)
156
having a downwardly protruding (
) tongue. The tongue fits into an upwardly opening groove defined in a stator
157
having a
-shaped section. The stator
157
extends along a center line (extending in the Y direction) of the stage assembly
150
on the installation surface S. The tongue of the armature
156
fits into the groove in the stator
157
with a small gap therebetween, thereby forming a linear motor. Thus, the member
153
is movable in the Y direction (perpendicular to the plane of the page).
The configuration of an air bearing is described further, with reference to FIG.
32
. As noted above, air bearings are defined between the opposing faces of a guide member
152
and the movable member
153
that slides between opposing faces of the guide member
152
. Each guide member
152
comprises an upper portion
152
a
, a side portion
152
b
, and a lower portion
152
c
. In
FIG. 32
, an upper portion
152
a
has been pivoted upward (note arc-shaped arrow A
1
) from the position indicated by broken lines to reveal detail, and the side portion
152
b
has been pivoted downward (note arc-shaped arrow A
2
) from the position indicated by broken lines to reveal detail.
Defined on the depicted upper surface and end surface of the movable member
153
are respective pairs of air pads
153
a
. Each air pad
153
a
comprises a porous material transmissive to a gas. The gas is supplied from a gas source
158
to the air pads
153
a
via a conduit
153
b
. Each pair of air pads
153
a
is surrounded by a respective “guard ring”
153
c
. A respective gas-exhaust port
154
a
is defined in the upper portion
152
a
and the side portion
152
b
opposite the respective guard ring
153
c
on the movable member
153
. A rotary exhaust pump
159
is connected to the gas-exhaust port
154
a
via an exhaust conduit
154
b
. Thus, gas discharged from the air pads
153
a
is exhausted by the exhaust pump
159
.
The movable member
153
moves in the Y direction in
FIGS. 31 and 32
. In
FIG. 32
, selected end positions of the movement range of the guard ring
153
c
are shown by the broken lines on the inside surface of the side portion
152
b
. As can be understood from this figure, within the range of movement of a guard ring
153
c
, the guard ring
153
c
remains at all times in communication with the respective gas-exhaust port
154
a
. Thus, gas discharged from the air pads
153
a
is collected by the respective gas-exhaust ports
154
a
and exhausted with almost no leakage to the chamber or other vacuum environment in which the stage assembly is located.
The stage assembly disclosed in WO 99/66221 can be used in a vacuum. However, this stage assembly has several disadvantages. First, it is based on a single movable member
153
that moves only along one axis (X or Y). If two-dimensional movement of the wafer stage
161
is required or desired, then two movable members are required that must be stacked relative to each other, resulting in a lar
Kakizaki Yukio
Narushima Hiroaki
Okubo Yukiharu
Tanaka Keiichi
Yoda Yasushi
Klarquist & Sparkman, LLP
Martin Edgardo San
Nappi Robert E.
LandOfFree
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