Refrigeration – Article moving means
Reexamination Certificate
1999-11-03
2001-10-09
Doerrler, William (Department: 3744)
Refrigeration
Article moving means
Reexamination Certificate
active
06298685
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of semiconductor processing. More specifically, the invention relates to an apparatus and method for carrying substrates through a processing system.
2. Background of the Related Art
In the semiconductor industry, there are two primary methods of moving substrates through a processing system. One traditional method uses a cluster tool arrangement shown in
FIG. 1. A
cluster tool platform
2
generally refers to a modular, multi-chamber, integrated processing system. It typically includes central wafer handling vacuum chambers
20
,
32
and a number of peripheral processing chambers
24
,
26
,
28
, and
36
. Substrates such as wafers
22
, typically stored in cassettes
10
, are loaded and unloaded from load locks
12
,
14
and processed under vacuum in various processing chambers without being exposed to ambient conditions. The transfer of the wafers for the processes is managed by a centralized robot
16
in a wafer handling vacuum chamber
20
or robot
30
in a second wafer handling vacuum chamber
32
which are maintained under vacuum conditions. A microprocessor controller
38
and associated software is provided to control processing and movement of wafers.
For relatively large substrates, such as glass substrates, ceramic plates, plastic sheets, and disks, a second method of moving substrates through a processing system, referred to as an inline system, is typically used. Glass substrates are used in the manufacture of flat panel displays, which are used as active matrix televisions, computer displays, liquid crystal display (LCD) panels, and other displays. A typical glass substrate has dimensions of about 550 mm by 650 mm and the trend is to increase the substrate size to about 650 mm by 830 mm and larger.
FIG. 2
is a schematic side view of a typical modular inline system
40
. The processing system includes a serial arrangement of processing chambers
42
,
44
disposed between a load chamber
46
and an unload chamber
48
on the ends of the series of processing chambers. An elevator
50
is disposed at an entry to the load chamber
46
and another elevator
52
is disposed at an exit from the unload chamber
48
. The processing chambers, such as processing chamber
44
, may include deposition chambers, such as chemical vapor deposition (CVD) chambers, physical vapor deposition (PVD) chambers, etch chambers, electroplating chambers, and other sputtering and processing chambers. A carrier return line
58
is disposed above the processing chambers and coupled to the elevators
50
,
52
. The various processing chambers are under vacuum or low pressure and are separated by one or more isolation valves
60
,
62
,
64
,
66
,
68
as shown in the schematic top view of the inline system in FIG.
3
. Typically, multiple substrates
54
,
56
,
70
,
72
are supported by a carrier
74
, as shown in the schematic front view and side view of the carrier in
FIGS. 4 and 5
. The isolation valves seal the respective chambers from each other in a closed position and allow the substrates
54
,
56
to be transferred through the valves to an adjacent station in an open position.
A carrier
74
, shown in
FIG. 2
, is placed adjacent the elevator
50
where the substrates
54
,
56
,
70
,
72
are manually loaded onto the carrier
74
at a receiving station
51
. A door (not shown) to the elevator
50
opens and allows the carrier
74
to be placed within the elevator on a track (not shown). The temperature and pressure inside the elevator
50
is typically at ambient conditions. An isolation valve
60
opens and allows the carrier
74
to be moved on the track into a load chamber
46
. The load chamber
46
is sealed and pumped down to a typical vacuum in the range of about 10 mTorr to about 50 mTorr for CVD processing and about 1 mTorr to about 5 mTorr for PVD processing. Another isolation valve
62
is opened and the carrier
74
is moved into a processing chamber
42
, where the substrates are heated to a temperature suitable for processing. Another isolation valve
64
is opened and the carrier
74
is moved along the track into the processing chamber
44
. If the processing chamber
44
is a sputtering process chamber, the chamber can include a plurality of targets
76
,
78
that sputter material from the surface of the targets facing the substrates onto the substrates
54
,
56
,
70
,
72
as the substrates move along the track adjacent each target. Each sputtering target is bombarded on the side facing the substrate with ionized gas atoms (ions) created between an anode (typically the target) and a cathode (typically the grounded chamber wall) and particles of the target are dislodged and directed toward the substrates for deposition on the substrates. Each target preferably has a magnet (not shown) disposed on the back side of the target away from the substrates to enhance the sputtering rate by generating magnetic field lines generally parallel to the face of the target, around which electrons are trapped in spinning orbits to increase the likelihood of a collision with, and ionization of, a gas atom for sputtering. The substrates
54
,
56
,
70
,
72
are then moved to an unloading chamber
48
through isolation valve
66
. Isolation valve
66
closes, thereby sealing the processing chamber
44
from the unload chamber
48
. Isolation valve
68
opens and allows the carrier
74
to be removed from the unloading chamber
48
and the substrates
54
,
56
,
70
,
72
are typically unloaded manually from the carrier. The substrates can also be detained in the unloading chamber to allow time for the substrates to cool. After the substrates have been unloaded, the carrier
74
enters the elevator
52
, whereupon the elevator lifts the carrier
74
to the return line
58
. A track system (not shown) in the return line
58
returns the carrier to the elevator
50
, which lowers the carrier into position at the receiving station
51
on the other end of the processing system to receive a next batch of substrates to be processed.
While the inline system
40
is currently used for production, this type of inline system has several disadvantages. The carrier
74
undergoes thermal cycling as it is moved from a processing environment to an ambient environment in the elevators
50
,
52
and carrier return line
58
and back into a processing environment. As a result, deposition material may peel off or be otherwise dislodged from the carrier
74
and cause unwanted particle inclusion on the substrates. Additionally, the track system can generate contaminants in operation that become attached to the carrier and can be brought into the processing chamber. The elevators and track system add a level of complexity to the system and maintenance is required of the various moving components to reduce breakdowns. Additionally, the carrier
74
will absorb oxygen in the ambient environment, which can increase the chamber pressure and cause contamination of deposited film layers when oxygen outgasses therefrom in the vacuum chamber. In addition to the thermal cycling of the carrier
74
, the mean temperature of the carrier
74
typically rises as multiple sets of substrates are processed therewith at temperatures above ambient conditions. Most processes in processing chambers are temperature sensitive and typically a processing regime establishes a desired operating temperature to obtain consistent depositions. Consequently, heat transfer from the carrier
74
can affect the substrate and/or process and the films created at the beginning of production can vary compared to films created at the end of production with the increased mean temperature. Yet another challenge with the typical inline system is cross contamination between processes in adjacent processing chambers, especially those chambers using a reactive process. Reactive processing depends on two or more constituents in proper proportions. An influx of other materials from adjacent processing chambers can cause the reactive proc
Applied Materials Inc.
Doerrler William
Drake Malik N.
Thomason Moser & Patterson LLP
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