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The present application incorporates by reference each of the following
applications which are related cases of a common assignee and contain
related subject matter:
Ser. No. 060,991, filed 06/12/87, pending, Vacuum Slice Carrier; which is a
continuing application of Ser. No. 790,918, filed 10/24/85 by Davis, Cecil
and Matthews, Robert; now abandoned;
Ser. No. 060,976 filed 06/12/87, pending, Advanced Vacuum Processor; which
is a continuing application of Ser. No. 790,708, filed 10/24/85 by Davis,
Cecil; Spencer, John; Wooldridge, Tim; and Carter, Duane; now abandoned;
U.S. Pat. No. 4,687,542, issued Aug. 18, 1987, entitled Vacuum Processing
System by Davis, Cecil; Matthews, Robert; and Hildenbrand, Randall;
Ser. No. 790,707, filed 10/24/85, Pat. No. 4,685,999, entitled Apparatus
for Plasma-Assisted Etching by Davis, Cecil; Carter, Duane; and Jucha,
Rhett;
Ser. No. 061,017, filed 06/12/87, abandoned, entitled Integrated Circuit
Processing System; which is a continuing application of Ser. No. 824,342,
filed 1/30/86, abandoned, by Davis, Cecil; Bowling, Robert; and Matthews,
Robert; and
Ser. No. 915,608, filed 10/06/86, Pat. No. 4,718,975, entitled Movable
Particle Shield by Bowling, Robert; Larrabee, Graydon; and Liu, Benjamin;
Ser. No. 074,448, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Matthews, Robert; Loewenstein, Lee; Abernathy,
Joe; and Wooldridge, Timothy;
Ser. No. 075,016, filed 7/17/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Loewenstein, Lee; Matthews, Robert; and Jones,
John;
Ser. No. 073,943, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee; Rose, Alan; Kennedy, Robert III; Huffman,
Craig; and Davis, Cecil;
Ser. No. 073,948, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee;
Ser. No. 073,942, filed 7/16/87, pending entitled Processing Apparatus and
Method; by Jucha, Rhett; and Davis, Cecil;
Ser. No. 074,419, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; and Matthews, Robert;
Ser. No. 074,377, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Jucha, Rhett; Hildenbrand, Randall; Schultz,
Richard; Loewenstein, Lee; Matthews, Robert; Huffman, Craig; and Jones,
John;
Ser. No. 074,398, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Davis, Cecil; Loewenstein, Lee; Jucha, Rhett; Matthews,
Robert; Hildenbrand, Randall; Freeman, Dean; and Jones, John;
Ser. No. 074,456, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Jucha, Rhett; Luttmer, Joseph; York, Rudy;
Loewenstein, Lee; Matthews, Robert; and Hildenbrand, Randall;
Ser. No. 074,399, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Jucha, Rhett; and Davis, Cecil;
Ser. No. 074,450, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Jucha, Rhett; Davis, Cecil; and Jones, John;
Ser. No. 074,375, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Jucha, Rhett; Carter, D.; Davis, Cecil; and Crank S.;
Ser. No. 074,411, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Jucha, Rhett; Davis, Cecil; Carter, D.; Crank, S.; and Jones,
John;
Ser. No. 074,390, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Jucha, Rhett; Davis, Cecil; and Crank S.;
Ser. No. 074,114, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Davis, Cecil; Loewenstein, Lee; Freeman, Dean; and Burris,
James;
Ser. No. 074,373, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Freeman, Dean; Burris, James; Davis, Cecil; and Loewenstein,
Lee;
Ser. No. 074,391, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Freeman, Dean; Burris, James; Davis, Cecil; and Loewenstein,
Lee:
Ser. No. 074,415, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Freeman, Dean; Burris, James; Davis, Cecil; Loewenstein, Lee;
Ser. No. 074,451, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Luttmer, Joseph; Davis, Cecil; Smith, Patricia; York, Rudy;
Loewenstein, Lee; and Jucha, Rhett;
Ser. No. 073,945, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Luttmer, Joseph, Davis, Cecil; Smith, Patricia; and York, Rudy;
Ser. No. 073,936, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Luttmer, Joseph, Davis, Cecil; Smith, Patricia, and York, Rudy;
Ser. No. 074,111, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Luttmer, Joseph, York, Rudy; Smith, Patricia; and Davis,
Cecil;
Ser. No. 074,386, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by York, Rudy; Luttmer, Joseph; Smith, Patricia; and Davis, Cecil;
Ser. No. 074,407, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by York, Rudy; Luttmer, Joseph; Smith, Patricia; and Davis,
Cecil;
Ser. No. 075,018, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Abernathy, Joe; Matthews, Robert; Hildenbrand,
Randall; Simpson, Bruce; Bohlman, James; Loewenstein, Lee; and Jones,
John;
Ser. No. 074,112, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Matthews, Robert; York, Rudy; Luttmer, Joseph;
Jakubik, Dwain; and Hunter, James;
Ser. No. 074,449, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Smith, Greg; Matthews, Robert; Jones, John;
Smith, James; and Schultz, Richard;
Ser. No. 074,406, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Davis, Cecil; Freeman, Dean; Matthews, Robert; Tomlin,
Joel,
Ser. No. 073,941, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Loewenstein, Lee; Tipton, Charlotte; Smith,
Randee, Pohlmeier, R.; Jones, John; Bowling, Robert; and Russell, I;
Ser. No. 074,371, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee; and Davis, Cecil;
Ser. No. 074,418, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Fisher, Wayne;
Ser. No. 073,934, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Fisher, Wayne; Bennett, Tommy; Davis, Cecil; and Matthews,
Robert;
Ser. No. 074,403, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Davis, Cecil; Matthews, Robert; and Fisher, Wayne;
Ser. No. 075,019, filed 7/17/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Freeman, Dean; Matthews, Robert; and Tomlin,
Joel;
Ser. No. 073,939, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Davis, Cecil; Abernathy, Joe; Matthews, Robert,
Hildenbrand, Randy; Simpson, Bruce; Bohlman, James; Loewenstein, Lee; and
Jones, John;
Ser. No. 073,944, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Cecil, Davis and Jucha, Rhett;
Ser. No. 073,935, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Liu, Jiann; Davis, Cecil; and Loewenstein, Lee;
Ser. No. 074,129, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee; Freeman, Dean; and Davis, Cecil;
Ser. No. 074,455, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee; Freeman, Dean; and Davis, Cecil;
Ser. No. 074,453, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee; Freeman, Dean; and Davis, Cecil;
Ser. No. 073,949, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Loewenstein, Lee; and Davis, Cecil;
Ser. No. 074,379, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee; and Davis, Cecil;
Ser. No. 073,937, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Loewenstein, Lee; and Davis, Cecil;
Ser. No. 074,425, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Loewenstein, Lee; Davis, Cecil; and Jucha, Rhett;
Ser. No. 074,452, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Jucha, Rhett; Davis, Cecil; and Loewenstein, Lee;
Ser. No. 074,454, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Jucha, Rhett; Davis, Cecil; and Loewenstein, Lee;
Ser. No. 074,422, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Matthews, Robert; Jucha, Rhett; and Loewenstein,
Lee;
Ser. No. 074,113, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; Matthews, Robert; Loewenstein, Lee; Jucha, Rhett;
Hildenbrand, Randy; and Jones, John;
Ser. No. 073,940, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; and Matthews, Robert;
Ser. No. 075,017, filed 7/17/87, pending, entitled Processing Apparatus and
Method; by Loewenstein, Lee;
Ser. No. 073,946, filed 7/16/87, pending, entitled Processing Apparatus and
Method; by Davis, Cecil; and Matthews, Robert; and
Ser. No. 073,938, filed 7/16/87, abandoned, entitled Processing Apparatus
and Method; by Davis, Cecil; and Matthews, Robert.
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to apparatus and methods for manufacturing
integrated circuits and other electronic devices.
One of the basic problems in integrated circuit manufacturing is defects
caused by the presence of particulates. For example, if photolithography
with 0.8 micron minimum geometry is being performed to pattern a conductor
layer, the presence of a 0.5 micron particle can narrow the patterned line
enough to cause a defect which will prevent the circuit from operating
(either immediately due to an open circuit, or eventually due to
electromigration). For another example, if a 100 .ANG. particle of silicon
adheres to the surface and is included in a 200 .ANG. nitride layer being
grown, the dielectric will have greater chances of breaking down at that
point, even assuming that no subsequent process step disturbs the silicon
particle.
This problem is becoming more and more troublesome because of two trends in
integrated circuit processing: First, as device dimensions become smaller
and smaller, the size of a "killing defect" becomes smaller, so that it is
necessary to avoid the presence of smaller and smaller particles. This
makes the job of making sure that a clean room is really clean
increasingly difficult. For example, a clean room which is Class 1 (i.e.
has an atmosphere with less than one particle per cubic foot) for
particles of one micron and larger may well be Class 1000 or worse if
particle sizes down to 100 Angstroms are counted.
Second, there is an increased desire to use large size integrated circuits.
For example, integrated circuit sizes larger than 50,000 square mils are
much more commonly used now than they were five years ago. This means that
each fatal defect is likely to destroy a larger area of processed wafer
than was previously true. Another way to think of this is that not only
has the critical defect size decreased, but the critical defect density
has also decreased.
Thus, particulates are not only an extremely important source of loss in
integrated circuit manufacturing yields, but their importance will
increase very rapidly in the coming years. Thus, it is an object of the
present invention to provide generally applicable methods for fabricating
integrated circuits which reduce the sensitivity of the process to
particulate contamination.
One of the major sources of particulate contamination is human-generated,
including both the particles which are released by human bodies and the
particles which are stirred up by equipment operators moving around inside
a semiconductor processing facility (front end). To reduce the potential
for particulate contamination from this major source, the general trend in
the industry has been to make more use of automatic transfer operations.
Using such operations, for example, a cassette of wafers can be placed
into a machine, and then the machine automatically transfers the wafers,
one by one, from the cassette through the machine (to effect the
processing steps necessary) and back to the cassette, without manual
assistance.
However, efforts in the area of automatic transfer operations have served
to highlight the importance of a second source of particles, namely
particles generated by the wafers and the transfer mechanisms during
handling and transport operations. When the surface of the wafer jostles
slightly against any other hard surface, some particulate (of silicon,
silicon dioxide, or other materials) is likely to be released. The
particulate density inside a conventional wafer carrier is typically quite
high, due to this source of particulate. Moreover, many of the prior art
mechanisms for wafer transport generate substantial quantities of
particulate. The general problem is discussed in U.S. Pat. Nos. 4,439,243
and 4,439,244, which are incorporated by reference hereinto.
Some types of wafer processing are shown in U.S. Pat. Nos. 4,293,249 by
Whelan issued on Oct. 6, 1981, 4,306,292 by Head issued on Dec. 15, 1981,
and 3,765,763 by Nygaard issued on Oct. 16, 1973, which are incorporated
by reference hereinto.
The prior applications of common assignee discussed above addressed this
facet of the problem by providing a vacuum wafer carrier in which
particulate generation due to abrasion of the surface of the wafer during
transport is reduced. The teachings of these prior applications enabled
not only reduced generation of particulate in the carrier during transport
and storage, but also reduced transport of particulate to the wafer's
active face during transport and storage by carrying the wafers face down
under a high vacuum. This allowed the rapid settling of both ambient and
transport generated particulate on other than the active wafer face.
The wafers can therefore be transported, loaded, unloaded and processed
without ever seeing atmospheric or even low vacuum conditions. This is
extremely useful, because, at pressures of less than about 10.sup.-5 Torr,
there will not be enough Brownian motion to support particles of sizes
larger than about 100 .ANG., and these particles will fall out of this
low-pressure atmosphere relatively rapidly.
FIG. 2 shows the time required for particles of different sizes to fall one
meter under atmospheric pressure. Note that, at a pressure of 10.sup.-5
Torr or less, even 100 .ANG. particles will fall one meter per second, and
larger particles will fall faster. (Large particles will simply fall
ballistically, at the acceleration of gravity.) Thus, an atmosphere with a
pressure below 10.sup.-5 Torr means that particles one hundred angstroms
or larger can only be transported ballistically, and are not likely to be
transported onto the critical wafer surface by random air currents or
Brownian drift.
The relevance of this curve to the various embodiments described in the
present application is that the prior applications were the first known
teachings of a way to process wafers so that the wafers are never exposed
to airborne particulates, from the time they are loaded into the first
vaccum process station (which might well be a scrubbing and pumpdown
station) until the time when processing has been completed, except where
the processing step itself requires higher pressures (e.g. for
conventional photolithography stations or for wet processing steps). This
means that the total possibilities for particulate collection on the
wafers are vastly reduced.
The prior applications cited above also taught use of the vacuum wafer
carrier design together with a load lock and vacuum wafer transport
mechanism at more than one process module, to provide a complete
low-particulate wafer transfer system. These vacuum load locks can
usefully incorporate mechanisms for opening a vacuum wafer carrier after
the load lock has been pumped down, for removing wafers from the carrier
in whatever random-access order is desired, and for passing the wafers one
by one through a port into an adjacent processing chamber. Moreover, the
load lock mechanism can close and reseal the vacuum wafer carrier, so that
the load lock itself can be brought up to atmospheric pressure and the
vacuum wafer carrier removed, without ever breaking the vacuum in the
vacuum wafer carrier. This process takes maximum advantage of the settling
phenomena illustrated in FIG. 2 and described in more detail below. The
wafer can then be moved in a virtually particulate free environment from
the carrier to the load lock into the process chamber and back through the
load lock to the carrier for, potentially, an entire manufacturing
sequence.
A process station (which may optionally contain one process module or more
than one process module) has more than one load lock attached to it. This
has several actual and potential advantages. First, processing can
continue on wafers transferred in from one load lock while the other load
lock is being reloaded, so that throughput is increased. Second, with some
types of mechanical malfunction it will be possible to move at least the
in-process wafers out of the central module area (into one of the load
locks, or even into one of the process modules) to keep them from exposure
to ambient if it is necessary to vent the process module to correct the
malfunction. This means that even fairly severe faults may be recoverable.
Third, if separate transfer arms are provided inside each of the load
locks, this provides the further advantage that, if a mechanical problem
occurs with one transfer apparatus inside its load lock, the process
station can continue in production, using transfer through the other load
lock, while maintenance is summoned to correct the mechanical malfunction.
The various process modules disclosed in the present application provide a
tremendous improvement in the modularity of processing equipment. That is,
a reactor can be changed to any one of a very wide variety of functions by
a relatively simple replacement. It may be seen from the detailed
descriptions below that most of the different functions available can be
installed merely by making replacements in the wafer susceptor and related
structures--i.e. in the top piece of the reactor, which bolts on--or in
the feed structures, i.e. the structures directly below the wafer. Thus,
the basic configuration of the vacuum chamber and wafer transfer interface
is changed very little.
This capability confers tremendous advantages. First, the marginal capital
cost of adding a new processing capability is greatly decreased. Second,
the flexibility of manufacturing space is greatly increased, since
machines can be reconfigured with relative ease to perform new functions.
Third, the design development time for reactor structures is greatly
decreased. Fourth, the time required to train personnel in use of a new
reactor is also greatly decreased, since many key functions will be
performed identically across a wide variety of reactors. Fifth, the cost
of mistakes will be reduced, since operators will less frequently make
mistakes due to unfamiliarity or confusion due to variety of equipment.
Sixth, the carrying cost of an adequate spare parts inventory will be
reduced. Seventh, the delay cost of repair and maintenance functions can
be reduced, since many such functions can be performed off-line after an
appropriate replacement module is swapped into the production reactor.
Eighth, the presence of disused and obsolete machines in manufacturing
space can be minimized, because a machine which had been configured to
perform an unneeded function can be reconfigured.
The various classes of modules disclosed herein provide the advantage that
the "footprint" required to emplace them is minimal. That is, if one or
more process modules like those described is located in a clean room, only
a minimum of clean room floor space (which is very expensive) will be
required.
The capability for transferring wafers from one process chamber to another
without breaking vacuum is enhanced by the modular compatibility of the
below described embodiments. In particular, one of the advantages of
modular processing units of the kind disclosed herein is that a single
process station may advantageously contain several process modules like
those described, so that wafers need not even go through the load lock to
be transferred between two modules which are in a common station.
One way to think about the advantages of the various module designs
discussed below might be to consider that they provide a super-capable
reactor, i.e. has more adaptation capability than can ever be used for any
single process. Viewed in this light, it may also be seen that their
features are advantageous in sequential processing. That is, it has been
recognized as desirable to perform more than one process in the same
chamber without removing the wafer. The reactor designs disclosed herein
are particularly advantageous in doing this, since the "excess" capability
of the reactor design means that it is easier to configure it to perform
two sequential steps.
Other and further advantages are set forth within and toward the end of the
Description of the Preferred Embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described with reference to the accompanying
drawings, wherein:
FIG. 1 shows a sample embodiment of a load lock which is compatible with
vacuum processing and transport of semiconductor integrated circuit
wafers.
FIG. 2 shows a graph of the time required to fall through air at various
pressures for particulates of various sizes.
FIG. 3 shows a sample wafer transfer structure, in a process station,
wherein the wafer is placed onto three pins by the transfer arm 28
reaching through the inter-chamber transfer port 30 from the adjacent
vacuum load lock chamber 12.
FIG. 4 shows a closer view of a sample embodiment of a multi-wafer vacuum
wafer carrier 10, docked onto the position registration platform 18 inside
a load lock like that of FIG. 1.
FIGS. 5A and 5B show a plan view of a sample process stations including
process modules and wafer transfer stages, and a load locks.
FIG. 6 shows a configuration for a process module, which can be used as one
of the process modules inside the process station shown in FIGS. 5A and
5B.
FIG. 7 shows the plasma reactor of FIG. 6 in the closed position, as it
would be during the actual etch process.
FIG. 8 shows a plan view of the reactor of FIG. 6.
FIG. 9 shows an improved version of the process module of FIG. 6, in a
sample embodiment which includes the capability for process enhancement by
ultraviolet light generated in situ and also the capability is also
provided for providing activated species (generated by gas flows through
an additional plasma discharge which is remote from the wafer face) to the
wafer face. The module is shown in a process station which includes only
one module and one load lock, but can also be used in embodiments like
that of FIGS. 5A and 5B.
FIG. 10 shows a physical configuration for a process station which can be
used for implementing some of the embodiments described herein.
FIG. 11 shows a flow chart for a load lock control system which provides
particulate protection in a vacuum process system.
FIG. 12 is a detailed view of the structure to realize the capability for
process enhancement by ultraviolet light generated in situ, in embodiments
such as that of FIG. 9.
FIG. 13 shows an alternative version of the structure of FIG. 12, without
the isolator window which (in the embodiment of FIG. 12) helps separate
the gas flows of the ultraviolet source plasma from the process gas flows
near the wafer face.
FIG. 14 shows a further alternative version of the structure of FIG. 12,
wherein the plasma which provides the ultraviolet source is generated
between electrodes which are approximately cylindrical, and wherein
capability is also provided for providing activated species (generated by
gas flows through an additional plasma discharge which is remote from the
wafer face) to the wafer face.
FIG. 15 shows an example of a structure which generates activated species
by gas flows through a plasma discharge which is remote from the wafer
face, in embodiments like that of FIG. 14.
FIG. 16 shows an example of a module which provides the combined
capabilities of plasma bombardment from a plasma in close proximity to the
wafer face, and provision of activated species from a remote discharge,
and illumination of the wafer face with intense ultraviolet light.
FIG. 17 shows an example of a process module which provides two separate
gas feed distributors, and which is particularly advantageous for chemical
vapor deposition operations using two sourc | | |
