Cluster valve for semiconductor wafer processing systems

Details Cluster valve for semiconductor wafer processing systems Cluster valve for semiconductor wafer processing systems

1999-05-25

2001-08-14

Fox, John (Department: 3753)

Fluid handling

Systems

With flow control means for branched passages

C137S613000

Reexamination Certificate

active

06273140

ABSTRACT:

BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The invention relates to a vacuum valve assembly and, more particularly, to a cluster valve for use with semiconductor wafer processing systems.
2. Description of the Background Art
Semiconductor wafer processes such as plasma etching and chemical vapor deposition (CVD) are often performed in sub-atmospheric conditions. To ensure peak performance in wafer processing, efficient operation of an exhaust assembly is required in order to pump away reaction by-products and maintain a fresh supply of reactant gases to the process chamber.
FIG. 1
illustrates schematically a typical exhaust assembly
100
connected to a chamber body
101
. The exhaust assembly
100
comprises for example, a vacuum coupler
102
, with an isolation valve
104
and a throttle valve
106
for control of the pumping operation. Diagnostic accessories (not shown) may also be connected to the vacuum coupler
102
via a valve
108
. The isolation valve
104
is used to isolate the process chamber body
101
from the pumping foreline
110
, while the throttle valve
106
allows control of the pumping capacity. O-ring seals are typically used to provide vacuum sealing between the flanges of the vacuum components. The existing design of vacuum flange couplings incorporating an O-ring seal usually leaves a space between the mating vacuum flanges. This is illustrated in
FIG. 1
by the gaps
112
,
114
and
116
between the chamber body
101
, vacuum coupler
102
, isolation valve
104
, and the throttle valve
106
. The non-metallic O-ring material is also a poor thermal conductor. As such, there is minimal heat transfer between the process chamber body
101
and components in the exhaust assembly
100
, such as the isolation valve
104
and the throttle valve
106
.
In many CVD applications, the process gases and by-products are often non-volatile or readily condensable, and may result in undesirable deposits inside the chamber body
101
or the exhaust assembly
100
. For example, in the deposition of silicon using a reaction of tetraethyl orthosilicate (TEOS) and ozone (O
3
) , TEOS and reaction by-products tend to condense onto cold interior surfaces of the exhaust assembly
100
. The accumulation of these deposits leads to clogging of the vacuum components such as the isolation valve
104
and the throttle valve
106
, and contributes to a deterioration of the pumping capacity and process performance. At a pressure of about 200 torr, TEOS condenses at temperatures below about 65° C. Therefore, it is common practice to maintain the chamber body
101
and the exhaust assembly
100
at some elevated temperature to minimize the formation of these deposits. The chamber body
101
, for example, may be heated by a resistive heater embedded in a chamber liner (not shown). In certain applications, a heater used to maintain a wafer support pedestal at an optimal processing temperature may also contribute to heating the chamber body
101
. The exhaust assembly
100
is typically heated externally by heating tapes or cartridge heaters (not shown) around the various vacuum components. However, these heaters invariably add to the cost and complexity of the operation of the exhaust assembly
100
. The need for external heaters for the exhaust assembly
100
can be eliminated if thermal conduction can be improved between the heated chamber body
101
and the exhaust assembly
100
.
In addition to heating, the process chamber
101
and the exhaust assembly
100
are also subjected to periodic dry cleaning procedures using chlorine (Cl
2
) or nitrogen fluoride (NF
3
) gases in either thermal or plasma conditions. The throttle valve
106
, being located farthest downstream in the exhaust assembly
100
, may not be as efficiently cleaned as, for example, the isolation valve
104
, due in part to the depletion of the reactive cleaning gas.
Therefore, there is an ongoing need for alternatives to facilitate equipment maintenance by providing a more compact design and improved thermal conduction between the chamber body
101
and the exhaust assembly
100
.
SUMMARY OF THE INVENTION
The present invention is a vacuum exhaust assembly designed for efficient maintenance and improved thermal conduction. The exhaust/valve assembly comprises a valve body having an interior valve seat and several adapter ports for connection to other vacuum components. Direct physical contacts are maintained between adjacent mating surfaces to ensure good thermal conduction among the vacuum components.
When the valve assembly is used as an exhaust assembly for a wafer processing system, the valve body is connected directly to a process chamber, which is maintained at an elevated temperature to minimize undesirable deposits inside the chamber. The present embodiment allows the entire exhaust assembly to be maintained at substantially the same elevated temperature without the need for external heaters. The compact design of the present invention also results in more efficient dry cleaning of the valve components in the exhaust assembly.


REFERENCES:
patent: 3076631 (1963-02-01), Grove
patent: 5232023 (1993-08-01), Zimmerly
patent: 5467796 (1995-11-01), Pettinaroli et al.

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