Coating apparatus – Gas or vapor deposition
Reexamination Certificate
2003-05-02
2004-12-14
Ghyka, Alexander (Department: 2812)
Coating apparatus
Gas or vapor deposition
C118S719000, C118S7230ER, C438S758000, C438S680000
Reexamination Certificate
active
06830624
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to apparatus for substrate processing and, more particularly, to a structure allowing remote plasma clean gases to by-pass a blocker plate.
The fabrication of semiconductor products, such as integrated circuits, often involves the formation of layers on a substrate, such as a silicon wafer. Various techniques have been developed for the deposition processes, as the layers often involve different materials. For example, a metal layer might be deposited and patterned to form conductive interconnects, or a dielectric layer might be formed to electrically insulate one conductive layer from another. Some types of layer formation processes that have been used to form layers of dielectric materials and other materials are chemical vapor deposition (CVD) processes.
CVD processes include thermal deposition processes, in which precursor gases or vapors react in response to the heated surface of the substrate, as well as plasma-enhanced CVD (“PECVD”) processes, in which electromagnetic energy is applied to at least one precursor gas or vapor to transform the precursor into a more reactive plasma. Forming a plasma can lower the temperature required to form a film, increase the rate of formation, or both. Therefore, plasma-enhanced process are desirable in many applications.
When a layer is formed on a substrate, some material is usually also deposited on the walls of the deposition chamber and other components of the deposition system as residue. The material on the walls of the chamber is generally undesirable because the residue can build up and become a source of particulate contamination, causing wafers to be rejected. Several cleaning procedures have been developed to remove residue from inside the chamber. One type of procedure, known as a “wet-clean” is performed by partially disassembling the deposition chamber and wiping the surfaces down with appropriate cleaning fluids. Other types of cleaning processes utilize a plasma to remove the residue by converting it to a volatile product that can be removed by the chamber exhaust system. These processes are known as “dry” cleans.
There are two general types-of plasma dry cleaning processes. One type forms a plasma inside the processing chamber, or “in situ”. An example of an in situ plasma clean uses fluorine-containing gases such as NF
3
, C
2
F
6
, or C
3
F
8
to form free fluorine for removing residue in the chamber interior.
Another approach to cleaning is to form a plasma in a remote plasma generator and then flow the ions into the processing chamber. Such a remote plasma cleaning process offers several advantages, such as providing a dry clean capability to a deposition system that does not have an in situ plasma system. Furthermore, a remote plasma system may be more efficient at converting cleaning plasma precursor gases or vapors into a plasma, and forming the plasma outside the chamber protects the interior of the chamber from potentially undesirable by-products of the plasma formation process, such as plasma heating and sputtering effects.
There are, however, some less advantageous aspects associated with the utilization of remote plasmas. One issue is that the remotely generated plasma may recombine to form less reactive species as the ions are flowed to the chamber. Such unwanted recombination reduces the effective concentration of the ions that are available to react in the chamber.
FIG. 3A
is a simplified schematic view of a conventional chemical vapor deposition (CVD) processing system
310
. CVD processing system
310
includes walls
312
and lid
314
defining deposition chamber
316
housing substrate support
318
. The substrate support member
318
is typically made of a ceramic or aluminum nitride (AIN) and may include a heater such as a resistive heating coil disposed inside the substrate support member, and may also include substrate chucking mechanisms for securely holding a substrate, such as a vacuum chuck or an electrostatic chuck.
Processing gas source
320
is in fluid communication with processing chamber
316
through mixing manifold
322
of gas delivery system
324
. Mixing manifold
322
is also in fluid communication with remote plasma generator
326
featuring RF source
328
and gas source
330
. Gas delivery system
324
further comprises gas box
332
in fluid communication with mixing manifold
322
, blocker plate
334
in fluid communication with gas box
332
, and gas distribution face plate
336
in fluid communication with blocker plate
334
.
Vacuum exhaust system
338
is connected to a gas outlet or foreline
342
of the chamber
316
. The exhaust system
338
includes one or more vacuum pumps
340
, such as a turbomolecular pump, connected to exhaust gases from and maintain vacuum levels in the chamber
316
. The one or more vacuum pumps
340
are connected to the foreline
342
for exhausting gases through a valve such as a gate valve. One or more cold traps
344
may be disposed on foreline
342
to remove or condense particular gases exhausted from the chamber.
FIG. 3B
is a simplified cross-sectional view of the conventional gas distribution system shown in FIG.
3
A. Gas distribution system
324
comprises mixing structure
322
configured to receive a flow of gas or remotely-generated plasma. Gas distribution system
324
also comprises gas box
332
having inlet
332
a
to center bore
332
b
that is configured to receive a flow of gases or ions from mixing structure
322
. Blocker plate
334
having orifices
334
a
is affixed to the bottom of gas box
332
.
Blocker plate
334
is a gas passageway which functions to transform the flow of gases through the relatively narrow conduit of the gas box into a homogenous gas flow over the entire expected surface area of the wafer positioned within the processing chamber. Accordingly, orifices
334
a
of blocker plate
334
are sized and positioned to create an initial, coarse distribution of flowed ions/gases over the expected substrate surface. Due to the configuration of holes in the blocker plate that are necessary to accomplish this initial coarse distribution, gases passing through the distribution system experience a pressure increase in region
399
immediately upstream of the blocker plate.
Ions or gases flowed through blocker plate
334
are in turn conveyed to gas distribution face plate
336
having orifices
336
a
. The orifices
336
a
of gas distribution face plate
336
are designed to accomplish a finer distribution of flowed gases/ions over the entire surface of the substrate, in order to ensure deposition of a layer of material of even thickness thereon. A larger number of orifices are thus typically present in the gas distribution faceplate than in the blocker plate. Because of the relatively large number of orifices in the faceplate, and because coarse distribution of gas flow has already been accomplished by the blocker plate, the increase in pressure upstream of the gas distribution face plate is relatively small compared with that arising upstream of the blocker plate.
Ions or gases flowed out of gas distribution face plate
336
enter the chamber and are available to participate in chemical reactions occurring therein, for example removal of residue formed on exposed surfaces of the chamber. However, ion recombination promoted by high pressure reduces the effective concentration of ions in the chamber and thus their cleaning effectiveness.
Therefore, there is a need in the art for methods and apparatuses which reduce the recombination of ions in a remotely-generated plasma that is flowed into a semiconductor fabrication chamber for processing.
SUMMARY OF THE INVENTION
A flow of a remotely-generated plasma to a processing chamber by-passes a blocker plate and thereby avoids unwanted recombination of active species. By-passing the blocker plate according to embodiments of the present invention avoids the high pressures arising upstream of the blocker plate, inhibiting ion recombination and elevating the concentration of reactive ions available in the pro
Janakiraman Karthik
Suarez Edwin C.
Applied Materials Inc.
Ghyka Alexander
Townsend & Townsend & Crew
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