Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-05-11
2002-02-05
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S405000, C392S410000, C118S724000
Reexamination Certificate
active
06344631
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to processing chambers for processes such as chemical vapor deposition of thin films onto substrates and, more particularly, to low mass substrate support assemblies for use in thin film deposition and rapid thermal processing chambers.
BACKGROUND
Thermal processes such as deposition of thin films onto substrates have many applications. One example of such an application is the processing of silicon substrates for the manufacture of integrated circuits. An important part of integrated circuit manufacturing is processing of the semiconductor substrate in which active devices such as transistors and capacitors that comprise the integrated circuit are formed. Any one of a number of processing steps may be carried out including deposition of a layer of material onto the wafer, etching a layer of material that is formed on the wafer or causing chemical reactions or temperature-enhanced mass transport within material formed on the wafer. Examples of materials that can be deposited during such processing include epitaxial silicon or polycrystalline silicon, or a thermal oxide or thermal nitride layer over silicon, and the like.
Processing chambers in which these processes can be performed typically include a platform such as a susceptor or an edge ring, a substrate support mechanism, a quartz housing or cover, and an array of lamps that provide radiant heat energy to the interior of the chamber and the substrate being processed. One or more of these processing steps may be carried out in a chemical vapor deposition processing chamber such as the processing chamber
100
shown in
FIG. 1A. A
wafer
102
is inserted through an opening (not shown) into the processing chamber
100
and located on a susceptor
104
. Upper heat lamps
106
are generally used to radiate infrared light through an upper dome
108
of the processing chamber
100
onto the wafer
102
. Lower heat lamps
107
may also be used to radiate infrared light through a lower dome
109
of the processing chamber
100
onto the susceptor
102
. Upper dome
108
and lower dome
109
are typically made of quartz. One or more gasses are then introduced into the processing chamber
100
. These gasses then carry out one or more of the processing steps, as previously discussed, with the wafer
102
being maintained at a required processing temperature.
By controlling power supplied to the heat lamps
106
and
107
the wafer
102
can be maintained at a required processing temperature.
FIG. 1B
is a top view of one example of an annular array
105
of upper heat lamps
106
that can be used with chamber
100
.
FIG. 2
shows a top view of an example of another processing chamber
200
in which the substrate or wafer rests on an edge ring (not shown) rather than a susceptor. The edge ring supports the wafer circumferentially at the wafer's edge. The edge ring (shown in
FIG. 3
) defines a central opening such that the bottom surface of the substrate is exposed to radiant heat from heat lamps positioned below the edge ring. The top surface of the wafer is exposed to an radiant heat of an array of upper heat lamps (not shown). In this type of chamber, the heat lamps are typically provided in an array referred to as a “honeycomb” array.
FIG. 2
shows a top view of an example of a honeycomb array. The honeycomb array of lamps is particularly suited to a chamber that uses an edge ring rather than a susceptor as the substrate support because the heating pattern produced by the honeycomb array is generally more controllable over the entire surface of the wafer as compared to the annular array of lamps. The honeycomb array, however, has a relatively large number of lamps, which can be relatively expensive to achieve an acceptable level of reliability. An annular array of lamps is typically more suited for use in a chamber having a susceptor as the wafer support because the susceptor provides a better distribution of heat to the substrate via conduction even though the heating pattern of the annular array may be somewhat uneven. The annular array has relatively fewer lamps compared to the honeycomb array.
Many tppes of thin film deposition chambers or reactors use silicon carbidecoated, graphite susceptors to hold the substrate or wafer during the deposition process. In addition to providing mechanical support for the wafer, the susceptor also absorbs and distributes the energy from the heating lamps to achieve a more uniform temperature distribution over the entire surface of the wafer resting on the susceptor during processing. A consequence of this design is that the reactor must provide enough energy to heat up not only the wafer but also the susceptor, which has a thermal mass several times larger than that of the wafer itself. Consequently, chamber throughput is limited as a significant fraction of the overall process time is spent heating up and cooling down the reactor between consecutive wafers. For this reason, and since the susceptor's diameter is fixed by the size of the wafers being processed, the trend over the years has been to decrease the thickness of the susceptor as much as current manufacturing techniques will allow.
There are, however, at least two major problems associated with this approach to reducing the susceptor's thermal mass. First, as susceptors become thinner, they inevitably lose mechanical strength, which makes them prone to deformation and even breakage. Even though manufacturers have proven adept at continuously improving their manufacturing capabilities for thinner susceptors, there are indications that it is becoming increasingly difficult for them to continue this trend. The second issue is that, with a reduced cross sectional area available for heat conduction, thinner susceptors have a diminished capacity to redistribute lamp heat, resulting in the possibility of uneven heating due to the heating pattern of the lamp array, especially in the case of an annular lamp array such as the type shown in FIG.
1
B.
SUMMARY
In one embodiment, a substrate processing assembly includes an edge support defining a substrate support location to support a substrate at an edge of the substrate during processing. The assembly further includes a first beat distributing plate positioned generally parallel to the edge support. A plurality of edge support holding arms is coupled to the edge support. The plurality of edge support holding arms is also coupled to the first heat distributing plate to hold the first heat distributing plate spaced apart from the edge support. In another embodiment, the assembly can include a second heat distributing plate spaced apart from the edge support. In yet another embodiment, the substrate processing assembly can be used in a substrate processing apparatus that includes a chamber within which the assembly is located and a radiant heat source to provide radiant heat to the chamber.
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Applied Materials Inc.
Blakely & Sokoloff, Taylor & Zafman
Fuqua Shawntina T.
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