Fluid handling – Systems – With pump
Reexamination Certificate
2000-02-16
2004-11-16
Rivell, John (Department: 3753)
Fluid handling
Systems
With pump
C137S565300, C137S565330, C118S715000, C118S719000
Reexamination Certificate
active
06817377
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for processing substrates with an integrated pumping system for evacuating gas.
2. Background of the Related Art
FIG. 1
is a cross sectional view of a conventional apparatus
15
for processing a substrate
20
. The apparatus
15
comprises process chambers
25
a
, transfer chambers
25
b
, and load-lock chambers
25
c
mounted contiguously on a platform
28
with openings for transferring substrates between the chambers. In the process chamber
25
a
, a process gas is used to etch features, deposit layers of material on a substrate
20
, or clean the chamber. The apparatus
15
, is isolated in a clean room or semi clean room
30
to separate and protect the substrates from other potentially harmful equipment.
A pumping system
35
is provided to evacuate the gas and create vacuum conditions within the chambers
25
a-c
. Pumping system
35
typically comprises a high vacuum pump
40
, such as a turbo molecular pump; a low vacuum pump
45
, such as a rotary blower pump; and a pre-vacuum pump
50
a-c
, such as a dry vacuum pump. Conventionally, the large low vacuum or pre-vacuum pumps are stored in enclosures or “garages” in a remote location in the fabrication facility. To detect and contain any leaks of the gases being pumped, the air around the pumps is ventilated by a large air collector located at the top of the garage. The high vacuum pump
40
can be housed in the clean room, as shown in
FIG. 1
, because it is smaller in size, relatively quiet and creates less noise and vibration than low vacuum and pre-vacuum pumps
45
,
50
a-c
. Additionally, the high vacuum pump
40
, unlike the low and pre-vacuum pumps
45
,
50
a-c
, exhausts gas to another pump, not to atmosphere. Typically, the inlet
55
of the high vacuum pump
40
is connected to the process chamber
25
, and its outlet
60
is connected to a foreline
65
a
that extends from the chamber to which it is connected to the intake
70
of the low vacuum pump
45
, which in turn, is coupled to the intake of the pre-vacuum pump
50
a
. The pre-vacuum pump
50
a
exhausts to an exhaust scrubber
72
. The pre-vacuum pump
50
a
reduces the pressure of the process chamber
25
a
from atmospheric pressure (760 Torr) down to a pressure of about 0.01 Torr; the low vacuum pump
45
reduces the chamber pressure for higher gas flows; and only when the chamber pressure is below 0.1 Torr is the high vacuum pump
40
operated to achieve a high vacuum below 0.1 Torr down to 10
−7
Torr. Another type of high vacuum pump is the cryopump, which is used alone or in conjunction with the turbomolecular pump. The pre-vacuum pump
50
is also used in conjunction with a cryopump (not shown) to pump down the process chambers fast. Pre-vacuum pumps
50
and low vacuum-pumps
45
are most commonly used in semiconductor processing apparatus. However, some semiconductor processing apparatus also use high vacuum pumps or cryopumps in conjunction with the pre-vacuum and low vacuum pumps to achieve higher vacuum levels within the chambers to which they are connected. A low vacuum pump
45
is essentially a single stage blower typically mounted on top of the pre-vacuum pump
50
in order to increase the pumping performance of the pre-vacuum pump.
As depicted in FIG.
1
and discussed below, the pre-vacuum pumps and low vacuum pumps have traditionally been placed outside of the clean room in an adjacent room or basement. There are a number of reasons for this remote placement of the pumps. First, the low and pre-vacuum pumps are large pumps that occupy an envelope of about 0.4 m
2
each. An “envelope” of space is typically a rectangle having sides defined by the edges of a component or components making up an apparatus. A “footprint” is the envelope of an apparatus with an additional two feet added to each side. As a point of reference, the entire envelope of some processing apparatus like the one shown in
FIG. 1
, is only about 6 m
2
. Therefore, six of the low or pre-vacuum pumps could occupy about one-half the space needed for an entire processing apparatus. The space problem associated with the large conventional pumps is magnified by the fact that the pumps are not designed to service more than one chamber and, therefore, each chamber requires its own dedicated pump. The conventional pumps disposed remotely from the processing systems also have intake ports, exhaust ports and other machine interfaces dispersed around various pump surfaces. The distribution of the connection points further increases the space required by each pump.
One problem associated with conventional pumps is contamination and heat generation which necessitate their separation from the processing apparatus. For example, conventional the low and pre-vacuum pumps are mounted in a frame built around their interior components allowing them to be arranged in rows or stacked on shelves in their remote location. With no enclosure to separate the inner workings of the pump from the surrounding environment, any equipment nearby is subject to the discharge of heat and particles from the pump.
Conventional low and pre-vacuum pumps are also heavy, noisy and cause vibration. For example, each pump weighs about 450 lbs. or more and creates noise of at least 65 db. Vibration of a single pump weighing 450 lbs. can exceed 3.0 m/s
2
. This level of vibration is not allowable near a process apparatus where robot arms are moving delicate wafers to and from process stations and wafer structures are being created in the 0.18-0.25 10
−6
m range.
As a result of the location of the pumps relative to the processing system, the forelines
65
a-c
between the pumps
40
,
45
,
50
a-c
and the chambers
25
a-c
have a large diameter to provide a high conductance pathway that has a reduced pumping load and resistance. The distance between the clean room and the low and pre-vacuum pumps can often require a 50 to 100 foot length of foreline
65
a-c
. These extended lengths require that the forelines
65
a-c
have a large diameter to operate the low and pre-vacuum pumps with reasonable efficiency. Typically, the foreline
65
a-c
is a stainless steel pipe, which resists corrosion from the process gas, having a diameter of 50 to 100 mm (2 to 4 inches). However, the large diameter stainless steel pipe is expensive and a long length of pipe can cost as much as the pump itself. In addition, the large number of elbow joints and connections in the long foreline extending from the clean room to a separate room, have to be carefully sealed with non-corrodible gas seals to avoid leaks and releasing hazardous and toxic gases during operation, which further adds to large capital costs in semiconductor fabrication facilities. Also, the pipes are sometimes heated to reduce the deposition of condensates on the inside surfaces of the pipes, another high expense associated with long, large diameter forelines.
Furthermore, even with large diameter forelines
65
a-c
, the efficiency of the low and pre-vacuum pumps
45
,
50
a-c
is often decreased by a factor of 2 to 4 because of the loss in pumping efficiency caused by the large length of intervening pipeline. Additionally, the large diameter and long length of the forelines
65
a-c
provide a large surface area that serves as a heat sink upon which condensates are deposited from the process gas flowing in the lines. In some processes, these condensates are dislodged and loosened by vibrations from the pumps
45
,
50
a-c
and can diffuse back into the chambers
25
a-c
and contaminate substrates processed therein.
The remote location of the low and pre-vacuum pumps also prevents pressure within the chambers
25
a-c
from being reduced in a responsive or fast manner because of the distance between the chamber and the pump. Typically, the chamber pressure is measured by the pressure gauge
80
which feeds a pressure signal to a throttle valve controller
90
which opens or closes the throttle valve
75
a,b
to control the pressure of gas in the chamber
25
a
Reimer Paul
Sabouri Pedram
Smith Dennis
Applied Materials Inc.
Moser Patterson & Sheridan LLP
Rivell John
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