Valves and valve actuation – Rotary valves – Butterfly
Reexamination Certificate
2003-02-20
2004-10-26
Look, Edward K. (Department: 3754)
Valves and valve actuation
Rotary valves
Butterfly
Reexamination Certificate
active
06808163
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to valves for regulating chamber pressures of process chambers used in the fabrication of semiconductor integrated circuits. More particularly, the present invention relates to multi-unit pressure control valves for the rapid and accurate attainment of interior chamber gas pressures of process chambers such as etch chambers and CVD chambers.
BACKGROUND OF THE INVENTION
Integrated circuits are formed on a semiconductor substrate, which is typically composed of silicon. Such formation of integrated circuits involves sequentially forming or depositing multiple electrically conductive and insulative layers in or on the substrate. Chemical vapor deposition (CVD) processes are widely used to form layers of materials on a semiconductor wafer. CVD processes include thermal deposition processes, in which a gas is reacted with the heated surface of a semiconductor wafer substrate, as well as plasma-enhanced CVD processes, in which a gas is subjected to electromagnetic energy in order to transform the gas into a more reactive plasma. Forming a plasma can lower the temperature required to deposit a layer on the wafer substrate, to increase the rate of layer deposition, or both.
After the material layers are formed on the wafer substrate, etching processes may be used to form geometric patterns in the layers or vias for electrical contact between the layers. Etching processes include “wet” etching, in which one or more chemical reagents are brought into direct contact with the substrate, and “dry” etching, such as plasma etching. Various types of plasma etching processes are known in the art, including plasma etching, reactive ion (RI) etching and reactive ion beam etching. In each of these plasma processes, a gas is first introduced into a reaction chamber and then plasma is generated from the gas. This is accomplished by dissociation of the gas into ions, free radicals and electrons by using an RF (radio frequency) generator, which includes one or more electrodes. The electrodes are accelerated in an electric field generated by the electrodes, and the energized electrons strike gas molecules to form additional ions, free radicals and electrons, which strike additional gas molecules, and the plasma eventually becomes self-sustaining. The ions, free radicals and electrons in the plasma react chemically with the layer material on the semiconductor wafer to form residual products which leave the wafer surface and thus, etch the material from the wafer.
Referring to the schematic of
FIG. 1
, an etch reactor
30
, such as an eMax etch reactor available from Applied Materials, Inc. of Santa Clara, Calif., includes a grounded reaction chamber
32
, typically fitted with liners (not shown) to protect the interior wall surfaces thereof. A wafer
34
is inserted into the chamber
32
typically through a slit valve opening
36
and is placed on a cathode pedestal
38
having an electrostatic chuck
40
that clamps the wafer
34
in place. A cooling fluid circulates through cooling channels (not shown) in the pedestal
38
to control the temperature of the pedestal
38
, and thus, the temperature of the wafer
34
. A thermal transfer gas such as helium may be supplied to grooves (not shown) provided in the upper, wafer-supporting surface of the pedestal
38
. The thermal transfer gas enhances the efficiency of thermal coupling between the pedestal
38
and the wafer
34
.
An RF power supply
42
is connected to the cathode pedestal
38
and generates the etchant plasma while controlling the DC self-bias. Magnetic coils
44
encircle the chamber
32
and generate a slowly-rotating, horizontal, essentially DC magnetic field to increase the intensity of the plasma. A vacuum pump
46
pumps the gaseous contents of the chamber
32
through an adjustable throttle valve
48
. Shields
50
,
52
may serve to both protect the chamber
32
and pedestal
38
from the etchant plasma and define a pumping channel
54
connected to the throttle valve
48
.
Processing gases are supplied from gas sources
58
,
60
,
62
through respective mass flow controllers
64
,
66
,
68
to a quartz gas distribution plate
70
positioned in the top of the chamber
32
overlying and separated from the wafer
34
across a processing region
72
. The gas distribution plate
70
includes a manifold
74
that receives the processing gas and communicates with the processing region
72
through a showerhead having a large number of distributed apertures
76
which facilitate a substantially uniform flow of processing gas into the processing region
72
.
By regulating the flow of gases from the interior of the vacuum chamber
32
to the vacuum pump
46
, the throttle valve
48
of the etch reactor
30
is typically used to control the interior pressures of the chamber
32
. As shown in
FIGS. 2 and 3
, the throttle valve
48
typically contains a valve frame
78
having a circular valve opening
79
. A pair of adjacent valve blades
80
is pivotally mounted in the valve opening
79
, and each of the valve blades
80
is operably engaged by a stepper motor (not shown). As shown in
FIG. 2
, in the closed position the valve blades
80
are disposed in coplanar relationship to each other and interlock to close the valve opening
79
. As shown in
FIG. 3
, upon flow of gases
81
from the vacuum chamber
32
to the vacuum pump
46
, the valve blades
80
are pivoted from the coplanar configuration to angled positions in stepwise fashion, thereby opening the valve opening
79
to varying degrees and regulating the rate of flow of the gas from the vacuum chamber
32
to the vacuum pump
46
, and thus, the interior pressure of the chamber
32
. The valve blades
80
can typically be incrementally opened throughout a range of finely-graded “steps” from 0 (in which the valve blades
80
are disposed in substantially coplanar relationship, or 0 degrees, with respect to the planar surface
82
of the valve frame
78
), through 800 (in which the valve blades
80
are disposed at a substantially 90-degree angle with respect to the planar surface
82
). The “0” step corresponds to the configuration of the valve blades
80
at which the valve opening
79
presents no area for gas flow, whereas the “800” step corresponds to the configuration of the valve blades
80
at which the valve opening
79
presents the largest area for gas flow through the throttle valve
48
.
Referring next to the graph of
FIG. 4
, wherein the area of the valve opening
79
available for flow of gas through the throttle valve
48
is plotted on the Y axis as a function of the various step positions of the valve blades
80
, which are plotted along the x axis. It can be seen from the graph that a typical etch process is carried out in the chamber
32
when the valve blades
80
are between steps
10
and
45
. In this relatively narrow process region interval, which begins when the valve blades
80
are close to the 0-step position, PI is aggressive and pressures in the chamber
32
are optimal for the etch process; on either side of the process region interval, pressures in the chamber
32
fluctuate rapidly and are unstable. Accordingly, a throttle valve is needed which is characterized by a wider process region interval that begins at a higher valve blade step to enhance pressure stability and maintain aggressive PI over a broader valve blade step range to increase throughput of wafers through the chamber and prolong hardware lifetime.
An object of the present invention is to provide new and improved blades for a throttle valve used in conjunction with a process chamber for substrate processing.
Another object of the present invention is to provide new and improved throttle valve blades which facilitate a broader process interval for the processing of substrates.
Still another object of the present invention is to provide new and improved throttle valve blades which enhance stability in chamber pressures during the processing of substrates.
Yet another object of the present invention is to provide new and improved thr
Chen Kun-Yi
Kuo Hue-Ming
Lee Ta-Chin
Fristoe Jr. John K.
Look Edward K.
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
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