Rotary kinetic fluid motors or pumps – Smooth runner surface for working fluid frictional contact
Reexamination Certificate
2000-12-18
2003-01-07
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
Smooth runner surface for working fluid frictional contact
C416S20100A
Reexamination Certificate
active
06503050
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to semiconductor processing. Specifically, the present invention relates to semiconductor processing equipment and a turbo-molecular vacuum pump with increased pumping capacity for evacuating a vacuum processing chamber.
2. Background of the Related Art
Substrates are typically processed through various etch, chemical vapor deposition (CVD), physical vapor deposition (PVD), ion implanting and cleaning steps to construct integrated circuits or other structures thereon. These steps are usually performed in an environmentally isolated and vacuum sealed substrate processing chamber. The substrate processing chamber generally comprises an enclosure having a side wall, a bottom and a lid. A substrate support member is disposed within the chamber to secure a substrate in place during processing by electrical or mechanical means such as an electrostatic chuck or a vacuum chuck. A slit valve is disposed on a chamber side wall to allow the transfer of the substrate into and out of the substrate processing chamber. In CVD processes, various process gases enter into the substrate processing chamber through a gas inlet, such as a shower-head type gas inlet, disposed through the lid of the processing chamber. In PVD processes, various process gases enter into the substrate processing chamber through a gas inlet in the processing chamber. In each type of process, the gases are exhausted from the substrate processing chamber through the use of a vacuum pump, such as a turbomolecular pump, which is attached to a gas outlet of the substrate processing chamber.
Turbo molecular pumps are used in high (10
−7
Torr) or ultra-high (10
−10
Torr) vacuum systems, exhausting to a backing pump that establishes a first pressure in the chamber. The turbo molecular pumps include a rotor with rows of oblique radial blades turning between a stator having inwardly facing rows of blades. The outer tips of the rotor blades approach molecular speed of the gas being pumped and when a molecule strikes the rotor, a significant component of momentum is transferred to the molecule in the direction of rotation. This transferred momentum causes the molecule of gas to move from the inlet side of the pump towards the exhaust side of the pump. Turbo molecular pumps are characterized by a rotational speed of 20,000 to 90,000 rpm and a pumping speed or capacity of 50 liters/sec. to 5,000 liters/sec.
FIG. 1
is a cross-sectional view of a typical turbo-molecular pump
10
. The turbo-molecular pump
10
generally comprises a cylindrical casing
72
, a base
74
closing the bottom of the casing
72
, a rotor
40
disposed coaxially in the casing
72
, a motor
20
coaxially disposed with the rotor
40
, and a stator
30
extending radially inwardly from the casing
72
. The casing
72
provides a support structure for the turbo-molecular pump
10
and includes an inlet port
12
disposed through the top of the casing
72
. An outlet port
14
is disposed through the base
74
and is attached to a backing pump and an abatement system (not shown) for recovery or disposal of the gases. The motor
20
is an electrical motor that rotates the rotor
40
about an axis. The rotor
40
may be suspended by mechanical bearings
37
or by magnetic bearings in a floating condition with the casing.
Rotor blades
46
and stator blades
36
are shaped to pump gas from the inlet port
12
to the outlet port
14
and to prevent gas flow back into the vacuum processing chamber (not shown). The rotor
40
includes rows of rotor blades
46
extending radially outwardly in levels from a central cylindrical portion of the rotor that receives a portion of the motor
20
. The stator
30
, likewise includes rows of blades
36
extending radially inwardly in levels from the casing
72
. The rows of stator blades
36
are arranged at alternating axial levels with the rows of rotor blades
46
, and a plurality of spacer rings
38
separate different levels of stator blades
36
to ensure that the rotor blades
46
can rotate freely between stator blades
36
. A “first stage” of the pump is defined by the first row of rotor blades
46
and the first row of stator blades
36
at the intake end of the pump. Each row of rotor blades
46
and corresponding row of stator blades
36
thereafter make up another stage and there are typically between 5 and 13 stages in a turbo-molecular pump. Additionally, a compound stage including a cylindrical member (not shown) extending from the exhaust end of the rotor
40
may be included to achieve a higher exhaust pressure and a higher inlet pressure.
Because of exacting temperature and cleanliness considerations in substrate processing, the substrate processing vacuum chambers are housed in an isolated clean room. Because the turbo molecular pumps must reduce pressure in the chambers down to 10
−7
Torr, they are necessarily located in the clean room adjacent the chambers to avoid any loss in pumping efficiency that would occur if the pumps were separated from the chambers by vacuum lines. Because the cost of building and maintaining clean rooms is so expensive, the physical size of components therein, including the turbo molecular pumps is always critical.
FIG. 2
is a simplified schematic, cross-sectional view of a vacuum substrate processing chamber
100
having a turbo-molecular pump
10
attached thereto. The turbo molecular pump
10
may be directly under the substrate
160
or offset, as depicted in FIG.
2
. The chamber
100
and pump
10
make up part of a processing apparatus typically comprising several processing chambers and at least one transfer chamber. The substrate processing chamber
100
provides an isolated environment where the substrate
160
is processed through etching, deposition, implanting, cleaning, cooling and/or other pre-processing and post-processing steps. The substrate processing chamber
100
generally comprises an enclosure having side walls
104
, a bottom
106
and a lid
108
. A substrate support member
110
disposed in the bottom
106
of the chamber secures the substrate
160
in place during processing. The substrate support member
110
typically comprises a vacuum chuck or an electrostatic chuck to retain the substrate
160
. A slit valve
112
is disposed on the chamber side wall
104
to allow the transfer of the substrate
160
into and out of the substrate processing chamber
100
. In a CVD process, various process gases enter into the substrate processing chamber
100
through a gas inlet
120
, such as a shower-head type gas inlet or nozzle, disposed through the lid
108
of the processing chamber. To exhaust the gases from the substrate processing chamber, a turbo-molecular pump
10
is attached to a gas outlet
130
of the substrate processing chamber
100
.
Advances in substrate processing and increased capacity of vacuum processing chambers continuously call for higher capacity pumps. Some substrate processes like plasma-based etch and CVD processes require particularly high process gas flow rates and relatively shallow vacuum levels. As the flow rate of the reactants across the substrate processing surface is increased (i.e., the throughput of the vacuum pump increases to exhaust a higher volume), the time required for completion of the process is reduced. Thus, to increase throughput of the processing chamber, the vacuum pumping system used for plasma-based etch and CVD requires a high throughput or exhaust capacity. Furthermore, as the chamber sizes increase to accommodate larger substrates (i.e., 300 mm substrates), the turbo-molecular pumps used for these larger chambers must provide correspondingly larger exhaust capacities. For example, an exhaust capacity of 4000 l/sec. is required for a 300 mm chamber.
One way to decrease exhaust time and increase throughput of the pump is to increase the rotational speed of the rotor of the turbo-molecular pump. However, increasing the rotational speed of a rotor and the rotor blades necessarily results in additio
Patel Jay
Reimer Peter
Smith Dennis R.
Applied Materials Inc.
Bach Joseph
Moser Patterson & Sheridan
Ryznic John E.
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