Method for Removing Material from Semiconductor Wafer and Apparatus for Performing the Same
by Inventors
Mikhail Korolik, Mike Ravkin, John deLarios, Fritz Redeker, John Boyd
BACKGROUND
[0001] During semiconductor fabrication, integrated circuits are created on a
semiconductor wafer ("wafer") defined from a material such as silicon. To create the integrated circuits on the wafer, it is necessary to fabricate a large number (e.g., millions)
of electronic devices such as resistors, diodes, capacitors, and transistors of various types. Fabrication of the electronic devices involves depositing, removing, and implanting
materials at precise locations on the wafer. A process called photolithography is commonly
used to facilitate deposition, removal, and implantation of materials at precise locations on
the wafer.
[0002] In the photolithography process, a photoresist material is first deposited onto the
wafer. The photoresist material is then exposed to light filtered by a reticle. The reticle is
generally a glass plate that is patterned with exemplary feature geometries that block light
from passing through the reticle. After passing through the reticle, the light contacts the surface of the photoresist material. The light changes the chemical composition of the exposed photoresist material. With a positive photoresist material, exposure to the light
renders the exposed photoresist material insoluble in a developing solution. Conversely,
with a negative photoresist material, exposure to the light renders the exposed photoresist material soluble in the developing solution. After the exposure to the light, the soluble
portions of the photoresist material are removed, leaving a patterned photoresist layer.
[0003] The wafer is then processed to remove, deposit, or implant materials in the wafer
regions not covered by the patterned photoresist layer. Such wafer processing often modifies the photoresist layer in such a way as to make removal of the photoresist more
difficult. For example, in the case of a plasma etch process, the outer layer of the
photoresist is transformed into a hard crust that is significantly less reactive that the
underlying photoresist. After the wafer processing, the patterned photoresist layer, its debris, as well as other types of polymer debris left after plasma etching, need to be
removed from the wafer in a process called photoresist stripping. It is important to
completely remove the photoresist and polymer material during the photoresist stripping process because such materials remaining on the wafer surface may cause defects in the
integrated circuits. Also, the photoresist stripping process should be performed carefully to avoid chemically modifying or physically damaging underlying materials present on the
wafer. A need exists for improvement in the photoresist stripping process such that more
complete removal of the photoresist and polymer material can be achieved while inflicting
less chemical modification and/or damage to the underlying wafer materials.
SUMMARY
[0004] In one embodiment, a method is disclosed for removing material from a
semiconductor wafer. The method includes an operation for maintaining a pressure in a
volume within which the semiconductor wafer resides to be sufficient to maintain a liquid state of a precursor fluid to a non-Newtonian fluid. The method also includes an operation
for disposing the precursor fluid on the semiconductor wafer while maintaining the
precursor fluid in the liquid state. More specifically, the precursor fluid is disposed proximate to the material that is to be removed from the semiconductor wafer. The method
further includes an operation for reducing the pressure in the volume within which the
semiconductor wafer resides. The reduction in pressure causes the precursor fluid to
transform into the non-Newtonian fluid. An expansion of the precursor fluid during the
transformation into the non-Newtonian fluid causes the resulting non-Newtonian fluid to remove the material from the semiconductor wafer.
[0005] In another embodiment, a method is disclosed for removing photoresist and polymer material from a semiconductor wafer. The method includes an operation for
disposing a solution on a semiconductor wafer to remove a bulk photoresist material. The
solution penetrates through a photoresist material to remove the bulk photoresist material
while leaving a photoresist crust. Following removal of the bulk photoresist material, a precursor fluid to a non-Newtonian fluid is disposed on the semiconductor wafer while
being maintained in a liquid state. Also, the precursor fluid is disposed to penetrate through
the photoresist crust to vacant regions underlying the photoresist crust. The method further
includes an operation for reducing a pressure ambient to the semiconductor wafer to transform the precursor fluid into the non-Newtonian fluid. An expansion of the precursor fluid during the transformation into the non-Newtonian fluid causes the resulting non-
Newtonian fluid to remove the photoresist crust and polymer material.
[0006] In another embodiment, an apparatus is disclosed for removing material from a
semiconductor wafer. The apparatus includes a chamber having a fluid input connected thereto. The fluid input is configured to dispose a precursor fluid to a non-Newtonian fluid on the semiconductor wafer to be supported within the chamber. The apparatus also
includes a pressurization device configured to control a pressure within the chamber. The pressurization device is capable of controlling a pressure within the chamber to maintain
the precursor fluid in a liquid state when being disposed on the semiconductor wafer. The
apparatus further includes a pressure release device configured to release a pressure within
the chamber to a lower pressure environment. Release of the pressure within the chamber
is sufficient to cause the precursor fluid to transform from the liquid state into the non-
Newtonian fluid. An expansion of the precursor fluid during the transformation into the non-Newtonian fluid is sufficient to cause the resulting non-Newtonian fluid to remove the
material from the semiconductor wafer.
[0007] Other aspects and advantages of the invention will become more apparent from the
following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure IA is an illustration depicting a semiconductor wafer having a patterned photoresist layer defined thereon;
Figure IB is an illustration depicting the semiconductor wafer and patterned
photoresist layer of Figure IA after having the plasma etching process performed thereon;
Figure 1C is an illustration depicting the semiconductor wafer, photoresist crust, and polymer material of Figure IB following removal of the bulk photoresist portion using a conventional wet strip chemistry;
Figure 2 is an illustration showing a flowchart of a method for removing material
from a semiconductor wafer, in accordance with one embodiment of the present invention;
Figure 3 A is an illustration depicting the configuration of Figure 1C following performance of operations 201 and 203 of the method of Figure 2, in accordance with one embodiment of the present invention;
Figure 3B is an illustration depicting the configuration of Figure 3 A following the
operation 205 of the method of Figure 2, in accordance with one embodiment of the
present invention;
Figure 3 C is an illustration depicting the semiconductor wafer following a rinse and
dry process to clean the removed photoresist crust, the removed polymer material, and non-
Newtonian fluid from the semiconductor wafer, in accordance with one embodiment of the
present invention;
Figure 4 is an illustration showing a flowchart of a method for removing
photoresist and polymer material from a semiconductor wafer, in accordance with one
embodiment of the present invention; and
Figure 5 is an illustration showing a processing chamber within which the method
for removing material from the semiconductor wafer can be performed, in accordance with
one embodiment of the present invention.
DETAILED DESCRIPTION
[0008] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to
one skilled in the art that the present invention may be practiced without some or all of
these specific details. In other instances, well known process operations have not been
described in detail in order not to unnecessarily obscure the present invention.
[0009] Figure IA is an illustration depicting a semiconductor wafer 101 having a patterned photoresist layer 103 defined thereon. It should be appreciated that the semiconductor
wafer 101 can include a buildup of many different materials in various geometric arrangements, depending on the extent of semiconductor fabrication that has occurred thus
far. The patterned photoresist layer 103 can be defined on the semiconductor wafer 101
using a common photolithography process. In the present discussion, the patterned
photoresist layer 103 serves as a mask to protect covered portions of the semiconductor
wafer 101 from a plasma used in a plasma etching process. Thus, the patterned photoresist
layer 103 also defines a pattern that will be etched into the semiconductor wafer 101.
[0010] Some wafer processing operations, such as the plasma etching process of the
present discussion, can transform a thickness of a patterned photoresist layer that is
exposed to the plasma into a photoresist crust. Figure IB is an illustration depicting the
semiconductor wafer 101 and patterned photoresist layer 103 of Figure IA after having the plasma etching process performed thereon. As shown in Figure IB, following the plasma etching process, the patterned photoresist layer 103 is defined by a bulk photoresist portion
103a and a photoresist crust 103b, wherein the bulk photoresist portion 103a underlies the
photoresist crust 103b.
[0011] The photoresist material defining the bulk photoresist portion 103a is essentially the same as the photoresist material defining the patterned photoresist layer 103 prior to
performing the plasma etching process. However, the photoresist crust 103b differs
significantly from the bulk photoresist portion 103 a. For example, in contrast to the bulk
photoresist portion 103 a, the photoresist crust 103b is a more rigid and porous material that
adheres tenaciously to the semiconductor wafer 101 surface.
[0012] Additionally, the plasma etching process can leave a polymer material 104 on the
semiconductor wafer 101 surface. During the etching process the polymer material 104 can
be created by reaction of species within the plasma with by-products of the etching process.
For example, the polymer material 104 can be a fluorocarbon based material that includes species from the substrate.
[0013] Following the plasma etching process, it is necessary to completely remove the bulk photoresist portion 103a, the photoresist crust 103b, and the polymer material 104.
Additionally, the photoresist and polymer materials should be removed without causing
chemical or physical damage to the underling features of the semiconductor wafer 101.
One method for removing the bulk photoresist portion 103a involves performing a wet
stripping operation. In the wet stripping operation, a wet strip chemistry is disposed over
the semiconductor wafer 101 and photoresist materials. The wet strip chemistry is designed
to penetrate through the porous photoresist crust 103 a and remove the bulk photoresist portion 103 a through a dissolution process. Some example wet strip chemistries include
AP902 produced by ATMI, Inc. and EZStrip 523 produced by Air Products and Chemicals, Inc., among others. Many of the conventional wet strip chemistries are
tetramethylammonium hydroxide (TMAH) based solutions that are designed to provide rapid removal of the bulk photoresist portion 103 a while remaining benign to underlying
features of the semiconductor wafer 101.
[0014] However, those skilled in the art will appreciate that while conventional wet strip
chemistries are effective at removing the bulk photoresist portion 103a, the conventional
wet strip chemistries are not capable of effectively removing the photoresist crust 103b
without causing damage to the underlying features of the semiconductor wafer 101. Thus,
conventional wet strip chemistries that are touted as being capable of removing the photoresist crust 103b are so aggressive that they cause damage to the underlying features of the semiconductor wafer 101.
[0015] Figure 1C is an illustration depicting the semiconductor wafer 101, photoresist
crust 103b, and polymer material 104 of Figure IB following removal of the bulk
photoresist portion 103 a using a conventional wet strip chemistry. Due to the conventional wet strip chemistry being capable of removing the bulk photoresist portion 103 a but not the
photoresist crust 103b, the photoresist crust 103b remains attached to the semiconductor
wafer 101 following the conventional wet strip process. It should be appreciated that due to
the porous nature of the photoresist crust 103b, the conventional wet chemistry process is capable of penetrating through the photoresist crust 103b and removing the bulk
photoresist portion 103a that underlies the photoresist crust 103b. Consequently, following
the conventional wet strip process, a shell of photoresist crust 103b remains attached to
each feature of the semiconductor wafer 101. Additionally, due to the chemical
characteristics of the photoresist crust 103b, a tenacious bond exists between the
photoresist crust 103b and the semiconductor wafer 101 at the interfaces 105 therebetween. Therefore, a method is needed to remove the photoresist crust 103b and polymer material
104 without damaging the underlying semiconductor wafer 101.
[0016] Figure 2 is an illustration showing a flowchart of a method for removing material from a semiconductor wafer, in accordance with one embodiment of the present invention.
The method includes an operation 201 for maintaining a pressure within a volume within
which a semiconductor wafer resides to be sufficient to maintain a precursor fluid to a non-
Newtonian fluid in a liquid state. Li one embodiment, the volume is pressurized to greater
than one atmosphere (1 arm) to maintain the precursor fluid in the liquid state. In another embodiment, the precursor fluid is formulated to be maintained in the liquid state at
atmospheric (1 ami) pressure within the volume. In yet another embodiment, the precursor fluid is formulated to be maintained in the liquid state at a volume internal pressure less
than one atmosphere (1 atm). The precursor fluid is described in more detail below. The
method then proceeds with an operation 203 for disposing the precursor fluid on the
semiconductor wafer while maintaining the precursor fluid in the liquid state. It should be
understood that the precursor fluid in the liquid state is capable of being disposed within
vias and between adjacent high-aspect ratio features defined on the semiconductor wafer. Additionally, the precursor fluid in the liquid state is capable of penetrating through the
porous photoresist crust to reach vacant regions that may underlie the photoresist crust.
Therefore, when the precursor fluid is disposed on the semiconductor wafer in the
operation 203, the precursor fluid is disposed proximate to material that is to be removed from the semiconductor wafer. Examples of such materials to be removed from the
semiconductor wafer can include photoresist, photoresist crust, polymer material, and
essentially any other unwanted residual material.
[0017] Following the operation 203, the method proceeds with an operation 205 in which
the pressure in the volume within which the semiconductor wafer resides is reduced to cause the precursor fluid to transform into the non-Newtonian fluid. A non-Newtonian
fluid is a fluid in which the viscosity changes with the applied shear force. An example of a
non-Newtonian fluid is a soft, condensed matter which occupies a middle ground between the extremes of a solid and a liquid, wherein the soft condensed matter is easily deformed
by external stresses. Foam is one example of a non-Newtonian fluid, as referenced herein,
wherein gas bubbles are defined within a liquid matrix. It should be appreciated, however,
that the non-Newtonian fluid associated with the present invention is not limited to a particular type of foam.
[0018] A volume expansion of the precursor fluid during its transformation into the non-
Newtonian fluid causes the resulting non-Newtonian fluid to remove the unwanted
materials, e.g., photoresist crust, polymer material, etc., from the semiconductor wafer. It
should be appreciated that as the precursor fluid transforms into the non-Newtonian fluid, expansion of the precursor fluid to the non-Newtonian fluid and the relative motion of the
non-Newtonian fluid with respect to the substrate, i.e., semiconductor wafer, causes the
non-Newtonian fluid to apply a mechanical force against the photoresist crust and polymer material such that the photoresist crust and polymer material are removed from the
semiconductor wafer. Thus, the liquid to non-Newtonian fluid transformation of the
precursor fluid present below and adjacent to the unwanted materials causes a mechanical
removal of the unwanted materials from the semiconductor wafer.
[0019] Because the precursor fluid works its way uniformly into spaces between features present on the semiconductor wafer, the transformation of the precursor fluid into the non-
Newtonian fluid with the accompanying expansion will exert substantially uniform
hydrostatic pressure on each side of the features present on the semiconductor wafer.
Therefore, the non-Newtonian fluid will not exert differential forces on semiconductor wafer features, thus avoiding damage to the features. Additionally, the non-Newtonian
fluid acts to entrain the materials that are removed from the semiconductor wafer.
Therefore, the removed materials such as photoresist crust and polymer material will not
resettle on and re-adhere to the semiconductor wafer.
[0020] As discussed above, the precursor fluid has a liquid state when maintained above a particular pressure. When exposed to a low enough pressure, the precursor fluid transforms
into the non-Newtonian fluid. For discussion purposes, the particular pressure below which the precursor fluid transforms into the non-Newtonian fluid is referred to as a
transformation pressure of the precursor fluid, hi one embodiment the precursor fluid is defined as a liquid having a propellant included therein by one of a number of methods
such as dissolution, mixing, emulsification, etc. When the pressure is lowered below the
transformation pressure, the propellant in the precursor fluid will expand to transform the precursor fluid into the non-Newtonian fluid.
[0021] The propellant in the precursor fluid is defined to maintain a liquid state above the
transformation pressure and a gas state below the transformation pressure. For example, in
one embodiment, propane (C3H8) can be used as the propellant. However, it should be
understood that in other embodiments the propellant material can be essentially any
material that satisfies the physical state requirements relative to the transformation pressure
and is chemically compatible with the precursor fluid, the semiconductor wafer, and the
processing environment/structures. At a pressure above the transformation pressure the propellant in the liquid state is added to the precursor fluid, hi one embodiment, an amount of propellant added to the precursor fluid is within a range extending from about 5% by
weight to about 20% by weight of the precursor fluid following addition of the propellant
therein. The largest amount of propellant that can be dissolved in the precursor fluid is
generally limited by the solubility of the propellant (in the liquid state) in the precursor
fluid.
[0022] In one embodiment of the present invention, the transformation of the precursor
fluid to the non-Newtonian is accomplished through a rapid decompression from a pressure
greater than the transformation pressure to a pressure lower than the transformation pressure. In one embodiment, the pressure ambient to the precursor fluid is reduced at a rate such that the precursor fluid in the liquid state is transformed into the non-Newtonian
fluid within a duration extending from about 0.01 second to about 2 seconds. As used
herein, the term "about" refers to being within plus or minus twenty percent of a given value, hi another embodiment, the pressure ambient to the precursor fluid is reduced at a
rate such that the precursor fluid in the liquid state is transformed into the non-Newtonian
fluid within a duration extending from about 0.05 second to about 0.2 second. In yet
another embodiment, the pressure ambient to the precursor fluid is reduced at a rate such that the precursor fluid in the liquid state is transformed into the non-Newtonian fluid
within a duration of about 0.01 second.
[0023] For the non-Newtonian fluid to exert a sufficient amount of force on the photoresist
crust and polymer material to cause their removal from the semiconductor wafer, the
volume ratio of the non-Newtonian fluid to the precursor fluid should be sufficiently large.
In one embodiment, the volume of the non-Newtonian fluid following expansion of the
propellant in the precursor fluid is within a range extending from about 2 times to about
100 times the volume of the precursor fluid in the liquid state. In another embodiment, the volume of the non-Newtonian fluid following expansion of the propellant in the precursor
fluid is within a range extending from about 5 times to about 20 times the volume of the
precursor fluid in the liquid state.
[0024] In one embodiment, the base precursor fluid, i.e., the non-propellant portion of the precursor fluid, is defined by adding various components to an amount of deionized water.
For example, the base precursor fluid can be formulated to include surfactants for reducing
surface tension and other additives capable of stabilizing bubbles that form during
transformation of the precursor fluid into the non-Newtonian fluid. Examples of such
additives can include fatty acids, cellulose, oils, and proteins, among others. The base precursor fluid can also include detergents and/or soaps. Additionally, hydrotropes can be
included in the base precursor fluid to bind strongly to the surface of micelles, thus controlling the size of the micelles. Additives that are capable of reducing the adhesion at
the interface between the photoresist crust and the semiconductor wafer can also be
included in the base precursor fluid. In one embodiment, an amount of the wet strip
chemistry used to remove the bulk photoresist can be added to the precursor fluid so that
residual bulk photoresist can continue to be removed during the removal of the photoresist crust.
[0025] With reference to the method of Figure 2, the ambient pressure relative to the
semiconductor wafer during operations 201 and 203 can be maintained just above the transformation pressure. However, during operations 201 and 203, there is no specific limit
on the ambient pressure from the precursor fluid perspective. Additionally, in some embodiments the propellant used in the precursor fluid may partially liquefy at pressures
approaching the complete liquefication pressure of the propellant. In these embodiments,
the precursor fluid can be defined to include an amount of propellant that is less than the
amount of propellant expected at full liquefication pressure. Thus, in these embodiments, the ambient pressure relative to the semiconductor wafer during operations 201 and 203 can be maintained at a pressure less than but approaching the complete liquefication
pressure of the propellant.
[0026] As the pressure is decreased below the transformation pressure and the propellant in the precursor fluid changes from liquid state to gas state, the propellant in the gas state
will behave as an ideal gas. Thus, according to the ideal gas law (PV=nRT), the volume of
the propellant in the gas state can be influenced by the temperature of the propellant in the
gas state. At a given pressure, a higher gas temperature will reflect a correspondingly
higher gas volume, vice-versa. It should also be appreciated that the pressure inside
bubbles will be affected by the size of the bubbles and the surface tension of the liquid
between the bubbles. At a fixed ambient pressure, smaller sized bubbles will have higher inside pressures relative to larger size bubbles. With an increased gas volume upon
transition of the propellant from the liquid state to the gas state, the resulting non- Newtonian fluid will occupy an increased volume. Thus, the method of Figure 2 can also
include an operation for controlling a temperature to control the volume expansion of the
precursor fluid during the transformation from the liquid state into the non-Newtonian
fluid. It should be appreciated that the temperature should be controlled with consideration
for preserving the chemistry of the precursor fluid.
[0027] Figure 3 A is an illustration depicting the configuration of Figure 1C following performance of operations 201 and 203 of the method of Figure 2, in accordance with one
embodiment of the present invention. As previously described a precursor fluid 301 in a
liquid state is disposed on the semiconductor wafer 101. The precursor fluid 301 is
disposed between features present on the semiconductor wafer 101. The precursor fluid 301 also penetrates through the porous photoresist crust 103b to regions underlying the
photoresist crust 103b that were previously occupied by the bulk photoresist portion 103 a. hi one embodiment, the semiconductor wafer 101 can be subjected to a rinse and dry
procedure prior to performing the method of Figure 2.
[0028] Figure 3B is an illustration depicting the configuration of Figure 3A following the operation 205 of the method of Figure 2, in accordance with one embodiment of the
present invention. As previously discussed, in the operation 205, the pressure is reduced
below the transformation pressure, thereby transforming the precursor fluid 301 into the non-Newtonian fluid 303. The fluid expansion and fluid motion associated with the
transformation of the precursor fluid 301 into the non-Newtonian fluid 303 causes the non-
Newtonian fluid to exert mechanical force on the photoresist crust 103b and polymer material 104, thereby removing the photoresist crust 103b and polymer material 104 from
the semiconductor wafer 101. The removed photoresist crust 103b and polymer material
become entrained in the non-Newtonian fluid 303, such that removed photoresist crust
103b and polymer material cannot resettle on and re-adhere to the semiconductor wafer 101. Figure 3 C is an illustration depicting the semiconductor wafer 101 following a rinse
and dry process to clean the removed photoresist crust 103b, the removed polymer material
104, and non-Newtonian fluid 303 from the semiconductor wafer 101, in accordance with one embodiment of the present invention.
[0029] The method for removing photoresist crust from the semiconductor wafer, as
previously described with respect to Figure 2, can be incorporated as part of a method for
general removal of photoresist material from a semiconductor wafer. Figure 4 is an
illustration showing a flowchart of a method for removing photoresist and polymer material from a semiconductor wafer, in accordance with one embodiment of the present
invention. The method includes an operation 401 for disposing a solution on the semiconductor wafer to remove a bulk photoresist material. The disposed solution is
capable of penetrating through a photoresist material to remove the bulk photoresist
material while leaving a photoresist crust.
[0030] Following removal of the bulk photoresist material, the method continues with an
operation 403 for disposing a precursor fluid to a non-Newtonian fluid on the
semiconductor wafer. The precursor fluid of the present method is equivalent to the
precursor fluid previously discussed. Thus, the precursor fluid is maintained in a liquid state when disposed on the semiconductor wafer. The precursor fluid is disposed to
penetrate through the photoresist crust to vacant regions underlying the photoresist crust. Then, in an operation 405, a pressure ambient to the semiconductor wafer is reduced to
transform the precursor fluid into the non-Newtonian fluid. A volume expansion of the precursor fluid during the transformation into the non-Newtonian fluid causes the non-
Newtonian fluid to exert mechanical force on and remove the photoresist crust and
polymer material.
[0031] Figure 5 is an illustration showing a processing chamber 501 within which the method for material from the semiconductor wafer can be performed as previously
described, in accordance with one embodiment of the present invention. The chamber 501
is capable of maintaining a chamber internal pressure greater than the operating pressure at
which the precursor fluid is maintained in the liquid state. A wafer support 503 is disposed within the chamber 501. The wafer support 503 is defined to hold a semiconductor wafer
505 during the material removal process.
[0032] The chamber 501 includes an input 507 connected to a precursor fluid source 509.
During operation, the precursor fluid is provided from the precursor fluid source 509
through the input 507 to be disposed on the semiconductor wafer 505, as indicated by arrow 511. The chamber 501 also includes an input 513 connected to a pressurization device 515. During operation, the pressurization device 515 is used to control the pressure
within the chamber 501 through addition or removal of a process atmosphere gas, as
indicated by arrow 517. The chamber 501 further includes an input 531 connected to a
temperature control 533. During operation the temperature control 533 is capable of
conditioning the process atmosphere gas via the input 531 to maintain a desired
temperature within the chamber 501. Also, in one embodiment, the temperature control
533 can be used to control a temperature of the wafer support 503 to in turn control a temperature of the semiconductor wafer 505.
[0033] A pressure release device 521 is connected to the chamber 501 through a connection 519. During operation, the pressure release device 521 is capable of rapidly
releasing the pressure within the chamber 501, as indicated by arrow 523, to cause the
precursor fluid to transform into the non-Newtonian fluid on the semiconductor wafer 505 surface. Following the transformation of the precursor fluid into the non-Newtonian fluid,
the resulting non-Newtonian fluid and removed materials, e.g., photoresist and polymer
material, can be removed through a connection 525 by a drain system 527, as indicated by
arrow 529. It should be appreciated that to avoid obscuring the present invention many additional details of the chamber 501 have not been described herein. However, one skilled
in the art will appreciated that the chamber 501 may include many features commonly associated with pressure chambers used for semiconductor wafer processing.
[0034] While this invention has been described in terms of several embodiments, it will be
appreciated that those skilled in the art upon reading the preceding specifications and
studying the drawings will realize various alterations, additions, permutations and equivalents thereof. Therefore, it is intended that the present invention includes all such alterations, additions, permutations, and equivalents as fall within the true spirit and scope
of the invention.
What is claimed is: