Bearings – Linear bearing – Fluid bearing
Reexamination Certificate
2000-07-24
2002-12-10
Joyce, William C (Department: 3682)
Bearings
Linear bearing
Fluid bearing
C384S007000, C414S935000, C414S676000
Reexamination Certificate
active
06491435
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to semiconductor process equipment, and more particularly, to a linear robot and method of using the same.
2. Description of the Related Art
Semiconductor processing typically involved the formation of one or more layers on a semiconductor substrate. As those of skill in the art understand, it was, critical to avoid particulate contamination of the formed layers.
Disadvantageously, mechanical bearings employed with the semiconductor processing equipment were a primary source of particulate generation and contamination. For example, when the mechanical bearing was a ball bearing, friction on the balls of the bearing generated particulates.
For this reason, air bearings were frequently employed. An air bearing used a layer of gas between moving parts thus avoiding particulate generation from friction between the parts. Although reducing particulate generation compared to a mechanical bearing, as discussed in greater detail below with reference
FIGS. 1 and 2
, an air bearing was still a significant source of particulate generation and contamination.
FIG. 1
is a perspective view of an air bearing
10
in accordance with the prior art.
FIG. 2
is a cross-sectional view of air bearing
10
of
FIG. 1
along the line II—II. Referring now to
FIGS. 1 and 2
together, air bearing
10
included a rectangular slide
12
and an air bearing body
14
. Pressurized gas, e.g., air or nitrogen, indicated as arrow
16
, was supplied to air bearing body
14
through a pressurized gas port
18
. This pressurized gas passed through a channel in air bearing body
14
and was supplied at the interface of slide
12
and air bearing body
14
, hereinafter called an air bearing region
20
.
Due to this pressurized gas, slide
12
floated on air bearing body
14
. Stated another way, a layer of gas, sometimes called an air bearing, was located between slide
12
and air bearing body
14
. Accordingly, slide
12
moved on a layer of gas thus avoiding particulate generation due to friction between slide
12
and air bearing body
14
.
To maintain the air bearing, pressurized gas was continuously supplied to air bearing region
20
. This pressurized gas continuously escaped from air bearing region
20
into a clean area
30
as indicated by arrows
22
. Clean area
30
was an area in which particulates were undesirable, e.g., an area in which silicon wafers or other substrates were handled.
Although great care was taken to supply only the highest purity pressurized gas, the pressurized gas inherently contained particulates. As the pressurized gas escaped from air bearing region
20
into clean area
30
, the particulates contained within the pressurized gas also escaped from air bearing region
20
into clean area
30
. These particulates were a significant source of particulate contamination of clean area
30
.
Further, as the pressurized gas escaped from air bearing region
20
, the pressurized gas had a tendency to dislodge and move about particulates within the vicinity of air bearing
10
in clean area
30
. This also was a significant source of particulate contamination of clean area
30
.
SUMMARY OF THE INVENTION
In accordance with the present invention, a particulate free air bearing and seal is formed between a slide and an air bearing body. Pressurized gas is supplied to an air bearing region between a first air bearing surface of the slide and a second air bearing surface of the air bearing body. The pressurized gas is supplied to the air bearing region through a distributor in the second air bearing surface of the air bearing body. The pressurized gas causes the slide to float on the air bearing body avoiding particulate generation due to friction between the slide and the air bearing body.
As pressurized gas is supplied to the air bearing region, vacuum is simultaneously supplied to a collector also in the second air bearing surface of the air bearing body. The collector captures the pressurized gas escaping from the air bearing region and prevents the pressurized gas from entering a clean area.
Since the pressurized gas from the air bearing region is prevented from entering the clean area, any possibility of particulate contamination of the clean area from particulates entrained within the pressurized gas is eliminated.
This is in contrast to a prior art air bearing where the pressurized gas, which escaped from the air bearing region, entrained particulates into the clean area within the vicinity of the air bearing. These particulates were a significant source of particulate contamination in the prior art.
Further, since the pressurized gas escaping from the air bearing region is prevented from entering the clean area, any possibility of the pressurized gas dislodging and moving about particulates within the clean area is eliminated. This is in contrast to a prior art air bearing where the pressurized gas, which escaped from the air bearing region into the clean area, had a tendency to dislodge and move about particulates in the clean area. These particulates were also a significant source of particulate contamination in the prior art.
In an alternative embodiment, the slide and the air bearing body are stationary and do not move with respect to one another or, alternatively, move on mechanical bearings between the slide and the air bearing body. In accordance with this embodiment, the air bearing functions as a seal instead of as an air bearing. The air bearing prevents particulates from passing between the air bearing body and the slide.
Since the air bearing region is supplied with pressurized gas from the distributor, the air bearing region is at a higher pressure than areas adjacent the air bearing region (the adjacent areas), e.g., the air bearing is between the clean area and a dirty area in which motors are located. Thus, any leakage of gas is pressurized gas leakage from the air bearing region into the adjacent areas and not vice versa. This prevents gas and particulates in the adjacent areas from entering into the air bearing region.
Further, even if gas and particulates do enter the air bearing region, the gas and particulates are captured by the collector and prevented from escaping from the air bearing region. In the above manner, the air bearing forms a seal between the air bearing body and the slide.
In one embodiment, the air bearing body is a tabletop, which remains stationary. The slide is a robot pedestal, which rotates and moves upwards and downwards during substrate handling. An air bearing between the tabletop and the robot pedestal forms a seal which prevents particulates from escaping between the tabletop and the robot pedestal as the robot pedestal moves.
In another embodiment, a robot arm-includes a slide and an end effector arm mounted to the slide. The slide is supported on a hanger. An air bearing between the slide and the hanger allows the slide to freely move on the hanger along a linear axis of the robot arm. Advantageously, the slide moves on the hanger without generating any particulates.
The slide has a base, which has a first surface. A vacuum coupler trench and a pressurized gas coupler trench are in the first surface of the base. The hanger has a vacuum channel and a pressurized gas channel. The vacuum channel extends to a first aperture in a lower surface of the hanger. The first aperture is aligned with the vacuum coupler trench.
The pressurized gas channel extends to a second aperture in the lower surface of the hanger. The second aperture is aligned with the pressurized gas coupler trench.
The pressurized gas coupler trench is coupled to a distributor in an air bearing surface of the slide. During use, pressurized gas is supplied through the pressurized gas channel in the hanger to the pressurized gas coupler trench of the slide. The pressurized gas is supplied from the pressurized gas coupler trench to the distributor, thus forming the air bearing between the slide and the hanger.
Of importance, the entire periphery of the air bearing surface of the slide is li
Carlos Thomas F.
Nishikawa Katsuhito
Gunnison McKay & Hodgson, L.L.P.
Hodgson Serge J.
Joyce William C
Moore Epitaxial Inc.
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