Data processing: generic control systems or specific application – Specific application – apparatus or process – Article handling
Reexamination Certificate
1998-09-01
2001-04-24
Ellis, Christopher P. (Department: 3651)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Article handling
C414S935000
Reexamination Certificate
active
06223096
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an elevator system for transferring a boat during the manufacture of semiconductor devices. More particularly, the present invention relates to an elevator system for transferring a wafer boat such that the wafers in the a boat are maintained horizontal.
2. Description of the Related Art
In general, the fabrication of a semiconductor device involves the execution of a plurality of processes. Therefore, various kinds of equipment and auxiliary devices are used to fabricate a semiconductor device.
These processes include a diffusion process in which a semiconductor device is provided with certain electrical characteristics. The process of diffusion includes a step of forming an oxide film on a wafer, and an annealing step in which the surface of the wafer is exposed to a solid or gas containing boron, phosphorus or the like under a high temperature.
A prior art furnace (
FIG. 1
) in which the diffusion process takes place comprises a quartz tube
19
and a heating chamber
18
for heating the quartz tube. The quartz tube
19
isolates the wafers
10
from the environment while the diffusion process is being carried out.
The auxiliary devices include an elevator
17
for loading/unloading a boat
14
of wafers
10
into/from the furnace, a wafer transfer device
13
for transferring the wafers
10
into and out of the boat
14
, a cassette transfer device
12
for transferring a cassette
11
containing a plurality of the wafers
10
to the wafer transfer device
13
, a control unit (not shown) for controlling the above-mentioned devices, and a gas supply unit for injecting refined gas into the heating chamber
18
.
In addition to the boat
14
, the conventional elevator system comprises a base
15
disposed under and supporting the boat
14
, an elevator
17
for moving up and down, and a horizontal control plate
16
interposed between an upper plate of the elevator
17
and the base
15
. The horizontal control plate
16
is manually adjustable to control the horizontal attitude of the base
15
.
More specifically, as shown in
FIG. 2
, four hex head bolts
20
extend through the horizontal control plate
16
and into the base
15
. The bolts
20
are arrayed along a pair of X and Y axes. The attitude of the wafers
10
with respect to the horizontal is controlled by rotating the hex head bolts
20
clockwise or counterclockwise and thereby adjusting the angle between the base
15
and the horizontal control plate
16
. A respective pair of wing nuts
21
are provided at opposite sides of each hex head bolt
20
to fasten the bolt
20
and prevent the bolt
20
from becoming loose.
The boat
14
should extend vertically from and at a right angle to the base
15
. However, the boat can become inclined when overloaded or due to pressure from the exterior environment. If such a situation were not attended to, the wafers would not be processed properly, and the equipment could be damaged. Accordingly, the operator periodically loosens the wing nuts
21
and rotates the hex head bolts
20
to manually adjust the base
15
by eye. Once the base
15
is adjusted and the boat is perceived by the operator to extend perfectly vertically, the operator tightens the wing nuts
21
to lock the bolts
20
in place.
However, the task of adjusting the base
15
is onerous because the operator must rotate the hex head bolts one or more times depending on his visual acuity, and the work of adjusting the hex head bolts and of loosening and tightening the eight wing nuts is very time-consuming.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to overcome one or more of the problems, disadvantages and limitations of the related art.
More specifically, one object of the present invention is to provide an elevator system for transferring a wafer boat, wherein the wafers in the boat are automatically oriented so as to lie horizontally.
Another object of the present invention is to provide an elevator system for transferring a wafer boat, wherein any deviation from the horizontal of the attitude of the wafers in the boat is corrected without operator intervention.
To achieve these and other advantages, the elevator system of the present invention includes the wafer boat, a base on which the boat is supported, an elevator for elevating the boat into a processing chamber and lowering it out of the chamber, a sensing unit for detecting the inclination of the boat relative to the horizontal, a horizontal control unit which is interposed between the base and the elevator and is drivable to maintain the boat in such a position that the wafers in the boat lie in horizontal planes, and a control unit for receiving information from the sensing unit and, based on the information, outputting a control signal to the horizontal control unit.
The horizontal control unit comprises a horizontal control plate fixed to the elevator, and a plurality of horizontal control driving units interposed between the base and the horizontal control plate. Each of the horizontal control driving units is movable up and down between the base and the horizontal control plate. The horizontal control unit also comprises a driving force generating unit for driving the horizontal control driving units so that the base can be tilted and hence, the inclination of the wafers relative to the horizontal can be adjusted.
The sensing unit can comprise sensors which either detect the actual inclination of the base and/or wafers relative to the horizontal or which provide feedback to indicate that the base and/or wafers are out of alignment with respect to a horizontal plane. For instance, the sensing unit may essentially consist of a level gauge, a pendulum, or two pairs of photo-sensors and light-emitting sensors. In the latter case, the photo-sensors and light-emitting sensors are arrayed such that the incident rays of light from the light-emitting sensors are directed to intersect each other perpendicularly. Receipt or non-receipt of these rays by the photo-sensors is indicative of the axis about which the horizontal control plate must be tilted to bring the wafers back to the horizontal.
The elevator system may also include a display unit connected to the control unit and displaying the information received from the sensing unit. Based on the information displayed, an operator can issue an order to the control unit to effect an alignment of the wafers with the horizontal. In this case, an input unit is connected to the control unit, receives the order keyed into the system by the operator, codes the order, and sends the coded order to the control unit.
REFERENCES:
patent: 5314574 (1994-05-01), Takahashi
patent: 5484483 (1996-01-01), Kyogoku
patent: 5604443 (1997-02-01), Kitamura et al.
patent: 5674039 (1997-10-01), Walker et al.
patent: 5697749 (1997-12-01), Iwabuchi et al.
patent: 5780849 (1998-07-01), Kikuchi
patent: 5857827 (1999-01-01), Asakawa et al.
Han Hyun
Kawk Sun-woo
Nam Ki-huem
Ellis Christopher P.
Jones Volentine, LLC
Samsung Electronics Co,. Ltd.
Tran Khoi H.
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