Cluster tool batchloader of substrate carrier

A system is provided for batch loading semiconductor wafers into a load lock from a portable carrier used for supporting a plurality of the wafers in spaced relationship and transporting them in a particle free environment. The carrier is supported adjacent a load lock chamber also having a particle free environment. A multilevel end effector associated with the load lock chamber includes a plurality of spaced end effector sets, each set being adapted to support a wafer thereon and aligned with an associated wafer supported in the carrier. The plurality of wafers are engaged and simultaneously retrieved as a grouping, then held in the load lock chamber for subsequent transport, one at a time, into an adjacent transport chamber for delivery to a specified one of a plurality of processing stations. A mini-environment sealingly isolates the load lock chamber and the interior of the carrier from the surrounding atmosphere. After transfer of the plurality of wafers from the carrier to the load lock chamber, the carrier and the load lock chamber are sealed and the load lock chamber and transport chambers are evacuated. A variety of mechanisms are provided for moving the end effector sets, both elevationally and into and out of the carrier and load lock chamber, and for moving a carrier door and a load lock door between closed, sealed, positions and open positions and to a parked position remote from the region between the carrier and the load lock chamber.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to standardized mechanical interface systems 
for reducing particle contamination and more particularly to apparatus 
employing sealed containers suitable for use in semiconductor processing 
equipment to prevent particle contamination. Still more particularly, the 
invention relates to such systems enabling transfer of multiple 
semiconductor wafers at a time between a transportable container or 
carrier and a load lock chamber with a controllable environment as they 
await further transfer to a processing station of a cluster tool. 
Throughput of the manufacturing process is thereby significantly 
increased. 
Throughout this disclosure, the term "wafer" will be used for purposes of 
consistency to refer to planar substrates such as silicon wafers and glass 
flat panels, but it will be understood that it is intended to be used in 
the broad context so as to be applicable to all substrates. Typically, 
such substrates are circular and have a diameter of 200 mm and a thickness 
of approximately 0.760 mm although, more recently, the diameter of choice 
has evolved to 300 mm with the same thickness. 
2. Description of the Prior Art 
Control of particulate contamination is imperative for cost effective, 
high-yielding and profitable manufacturing of VLSI circuits. Because 
design rules increasingly call for smaller and smaller lines and spaces, 
it is necessary to exert greater and greater control on the number of 
particles and to remove particles with smaller and smaller diameters. 
Some contamination particles cause incomplete etching in spaces between 
lines, thus leading to an unwanted electrical bridge. In addition to such 
physical defects, other contamination particles may cause electrical 
failure due to induced ionization or trapping centers in gate dielectrics 
or junctions. 
The main sources of particulate contamination are personnel, equipment, and 
chemicals. Particles given off by personnel are transmitted through the 
environment and through physical contact or migration onto the wafer 
surface. People, by shedding of skin flakes, for example, are a 
significant source of particles that are easily ionized and cause defects. 
Modern processing equipment must be concerned with particle sizes which 
range from below 0.01 micrometers to above 200 micrometers. Particles with 
these sizes can be very damaging in semiconductor processing. Typical 
semiconductor processes today employ geometries which are 1 micrometer and 
under. Unwanted contamination particles which have geometries measuring 
greater than 0.1 micrometer substantially interfere with 1 micrometer 
geometry semiconductor devices. The trend, of course, is to have smaller 
and smaller semiconductor processing geometries. 
In the recent past, "clean rooms" were established in which through 
filtering and other techniques, attempts were made to remove particles 
having geometries of 0.03 micrometer and above. There is a need, however, 
to improve the processing environment. The conventional "clean room" 
cannot be maintained as particle free as desired. It is virtually 
impossible to maintain conventional clean rooms free of particles of a 
0.01 micrometer size and below. Although clean room garments reduce 
particle emissions, they do not fully contain the emissions. It has been 
found that as many as 6000 particles per minute are emitted into an 
adjacent one cubic foot of space by a fully suited operator. 
To control contamination particles, the trend in the industry is to build 
more elaborate (and expensive) clean rooms with HEPA and ULPA 
recirculating air systems. Filter efficiencies of 99.999% and up to ten 
complete air exchanges per minute are required to obtain an acceptable 
level of cleanliness. 
Particles within the equipment and chemicals are termed "process defects." 
To minimize process defects, processing equipment manufacturers must 
prevent machine generated particles from reaching the wafers, and 
suppliers of gases and liquid chemicals must deliver cleaner products. 
Most important, a system must be designed that will effectively isolate 
wafers from particles during storage, transport and transfer into 
processing equipment. The Standard Mechanical Interface (SMIF) system has 
been devised, and used, to reduce particle contamination by significantly 
reducing particle fluxes onto wafers. This end is accomplished by 
mechanically ensuring that during transport, storage and processing of the 
wafers, the gaseous media (such as air or nitrogen) surrounding the wafers 
is essentially stationary relative to the wafers and by ensuring that 
particles from the ambient outside environment do not enter the immediate 
internal wafer environment. 
The SMIF concept is based on the realization that a small volume of still, 
particle-free air, with no internal source of particles, is the cleanest 
possible environment for wafers. 
A typical SMIF system utilizes (1) minimum volume, dustproof boxes or 
carriers for storing and transporting (2) open rack wafer cassettes, and 
(3) doors on the boxes or carriers designed to mate with doors on the 
interface ports on the processing equipment and the two doors being opened 
simultaneously so that particles which may have been on the external door 
surfaces are trapped ("sandwiched") between the doors. 
In a typical SMIF system, a box or carrier is placed at the interface port 
and latches release the box door and the port door simultaneously. A 
mechanical elevator lowers the two doors, with the cassette riding on top. 
A manipulator picks up the cassette and places it onto the cassette 
port/elevator of the equipment. After processing, the reverse operation 
takes place. 
SMIF systems have proved to be effective and this fact has been shown by 
experiments using SMIF components both inside and outside a clean room. 
The SMIF configuration achieved a ten-fold improvement over the 
conventional handling of open cassettes inside the clean room. 
Using SMIF systems, it was customary to carry a large number of the wafers 
within the box or carrier by supporting them in a spaced relationship by 
means of a cassette. Using this technique, the cassette would be loaded 
with a supply of wafers, transported into the box or carrier, then 
subsequently wafers would be removed from the cassette in the carrier one 
by one for placement into a reception chamber at a cluster tool or other 
site of further processing. 
Unfortunately, the use of cassettes required additional equipment 
inventory, increased the volume requirement for the box or carrier, added 
to the complexity of the system, increased its cost for original equipment 
and for upkeep of the equipment of the system. 
It was in light of the foregoing state of the art that the present 
invention has been conceived and is now reduced to practice. Specifically, 
the invention results from efforts to reduce equipment inventory and 
therefore initial cost, provide a simpler and more compact construction, 
reduce the cost of maintenance, and increase throughput of processed 
items. 
SUMMARY OF THE INVENTION 
According to the invention, a system is provided for batch loading 
semiconductor wafers into a loadslock from a portable carrier used for 
supporting a plurality of the wafers in spaced relationship and 
transporting them in a particle free environment. The carrier is supported 
adjacent a load lock chamber also having a particle free environment. A 
multilevel end effector associated with the load lock chamber includes a 
plurality of spaced end effector sets, each set being adapted to support a 
wafer thereon and aligned with an associated wafer supported in the 
carrier. The plurality of wafers are engaged and simultaneously retrieved 
as a grouping, then held in the load lock chamber for subsequent 
transport, one at a time, into an adjacent transport chamber for delivery 
to a specified one of a plurality of processing stations of a cluster 
tool. An isolation housing or mini-environment sealingly isolates the load 
lock chamber and the interior of the carrier from the surrounding 
atmosphere. After transfer of the plurality of wafers from the carrier to 
the load lock chamber, the carrier and the load lock chamber are sealed 
and the load lock chamber and transport chambers are evacuated. A variety 
of mechanisms are provided for moving the end effector sets, both 
elevationally and into and out of the carrier and load lock chamber, and 
for moving a carrier door and a load lock door between closed, sealed, 
positions and open positions and to a parked position remote from the 
region between the carrier and the load lock chamber. 
The invention serves to interface a wafer carrier directly to a load lock 
while maintaining the clean environment of the substrate carrier. No 
elevator is needed in the transfer of wafers since the load lock arm has a 
batch end effector which acts as a cassette in the load lock, yet has none 
of the constraints inherent in a cassette construction. Gaseous 
contamination from the cassette (typically a polymer which outgasses) is 
also eliminated thereby improving wafer process quality. Also, improved 
vacuum levels can be reached in shorter times since the arm assembly is 
primarily metal which outgasses minimally. 
The invention results in a construction by reason of which the purposes of 
the carrier and cassette are unified while eliminating the need for a 
cassette and the inventory which is undesirably associated with the use of 
cassettes. The risk of exposing wafers to undesirable particle 
contamination present in moving air as in traditional SMIF loaders where 
the cassette is lowered from a SMIF box then transferred to a load lock is 
eliminated. In the instance of the invention, wafers are loaded in a batch 
configuration which reduces overhead time and results in higher tool 
throughput. 
Other and further features, advantages, and benefits of the invention will 
become apparent in the following description taken in conjunction with the 
following drawings. It is to be understood that the foregoing general 
description and the following detailed description are exemplary and 
explanatory but are not to be restrictive of the invention. The 
accompanying drawings which are incorporated in and constitute a part of 
this invention, illustrate one of the embodiments of the invention, and, 
together with the description, serve to explain the principles of the 
invention in general terms. Like numerals refer to like parts throughout 
the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turn now to the drawings and, initially, to FIG. 1 which illustrates a 
processing system 20 for operating on silicon planar substrates such as 
wafers and flat panels. As noted above, throughout the remainder of this 
disclosure, the term "wafer" will be used for purposes of consistency to 
refer to such substrates, but it will be understood that it is intended to 
be used in the broad context so as to be applicable to all substrates. The 
invention is especially beneficial for operating on the newer size of 
substrates. 
The processing system 20 includes a load lock 22 for initially receiving 
wafers to be processed and a plurality of single-wafer processing stations 
24 for operations on the surfaces of the wafers such as imaging, plasma 
etching, and the like. It is typical for the processing stations 24 to be 
arranged about a closed locus as indicated by a dashed line 26. A 
transport chamber 28 is disposed concentrically within the load lock 22 
and processing stations 24 for singly transferring wafers to be processed 
and after processing between the load lock and one or more of the 
processing stations 24. A plurality of isolation valves 30 are 
individually provided at the interfaces of the several processing stations 
24 and the transport chamber 28 and between the load lock 22 and the 
transpert chamber 28. 
As previously noted, for some time now, it has been known to employ 
transportable SMIF boxes or containers, herein referred to as "carriers", 
for maintaining articles, such as semiconductor wafers, clean. This has 
been achieved by maintaining within each carrier a substantially particle 
free environment while the wafers are being brought to, or removed from, 
the processing system 20. Previously, it was customary to carry a large 
number of the wafers within the carrier by supporting them in a spaced 
relationship by means of a cassette (not shown). Using this technique, the 
cassette would be loaded with a supply of wafers, transported into the 
carrier, then subsequently wafers would be removed from the cassette 
within the carrier one by one for placement in the load lock 22 or the 
cassette would be transferred with the wafers within the clean 
mini-environment existing between the carrier, SMIF box, or the like, and 
the wafer processing equipment. 
According to the invention, turning now to FIGS. 2 and 3, a modified 
portable carrier 32 is provided for supporting and transporting a 
plurality of wafers 34 in spaced relationship in a substantially particle 
free environment. The carrier 32 has a plurality of rack member sets 36 
for supporting the wafers generally horizontally, in a generally 
vertically spaced relationship. 
The carrier 32 includes a carrier port 38 for providing access to the 
interior 40 thereof. A carrier door 42 on the carrier is movable between a 
closed position (FIG. 3) overlying the carrier port and an open position 
(FIG. 4) spaced from the carrier port. The carrier door 42 is illustrated 
as including a generally rectangular plate 44 and has a peripherally 
extending continuous transverse flange 46. A suitable seal 48 is 
interposed between the flange 46 and the carrier port 38 for sealing the 
interior 40 of the carrier from the surrounding atmosphere when the 
carrier door is in the closed position. 
At least a pair of opposed locking tabs 50 extend in a direction toward the 
carrier 32 from the flange 46 and each locking tab has a hole 52 
therethrough. Associated with each of the locking tabs 50 is a locking 
member 54 which may be in the form of a solenoid for operating a locking 
pin 56. Viewing especially FIG. 5, the locking member is suitably mounted 
on the carrier 32. When the locking pins 56 are engaged with their 
associated holes 52, the carrier door 42 is held closed with the flange 46 
bearing firmly against the carrier port 38 with the seal 48 interposed 
between the flange and the port to maintain the particle free environment 
within the interior 40 of the carrier. When the locking pins 56 are 
withdrawn from their associated holes 52, the carrier door 42 is then free 
to be removed from the carrier in a manner to be described below. 
Also, according to the invention, an isolation housing or mini-environment 
58 (see especially FIG. 2) is provided for sealingly isolating the load 
lock 22 and the interior 40 of the carrier 32 from the surrounding 
atmosphere. The carrier is brought in some suitable fashion from a remote 
location, then placed on a platform 60 which is a part of the 
mini-environment 58 and projects in a direction away from the processing 
system 20. An upper surface 62 of the platform 60 is formed with a 
plurality of depressions 64 properly spaced to receive feet 66 which 
project from the bottom of the carrier. When the feet 66 are fully engaged 
with the depressions 64, a front surface 68 of the carrier 32 is proximate 
an outer surface 70 of the mini-environment 58. 
The mini-environment has an aperture 72 which is generally aligned with the 
load lock 22 but spaced therefrom and when the carrier is seated on the 
platform 60, the carrier door 42 projects through the aperture into the 
interior of the mini-environment. A suitable seal 74 is provided between 
the mini-environment 58 and the carrier when supported on the platform and 
encompasses the carrier port 38 and the aperture 72 in the 
mini-environment for isolating the interior of the carrier, the interior 
of the mini-environment and the load lock from the surrounding atmosphere. 
With the carrier 32 positioned on the platform 60 in the manner 
illustrated in FIG. 3, a plurality of clamps 300 (FIG. 3A) pivotally 
mounted on the outer surface 70 of the mini-environment 58 may be 
selectively operated to engage with associated clamp recesses 302 provided 
in the outer peripheral surface of the carrier. In each instance, a clamp 
actuator 304 extends or retracts an actuator rod 306 which is pivotally 
attached to the clamp 300 at an end distant from the part engaging the 
recess 302. On signal, the clamp actuator 304 is effective to move the 
clamp 300 from the solid line position engaging the recess 302 to a broken 
line position disengaged from the recess. When all of the clamps 300 for 
the carrier 32 assume the solid line position, the seal 74 is compressed 
tightly between the carrier and the mini-environment. 
The load lock 22 defines a chamber 76 therein having a substantially 
particle free environment and includes a load lock port 78 opening into 
the load lock chamber. As noted previously, the load lock 22 is positioned 
intermediate the carrier 32 and the transport chamber 28. A load lock door 
80 is suitably mounted on the load lock for movement between a closed 
position overlying the load lock port 78 and an open position spaced 
therefrom. 
A load lock arm 82 within the load lock chamber 76 is movable between an 
inactive position distant from the carrier 32 (see FIG. 2) and an active 
position proximate the carrier (see FIG. 3). The load lock arm and its 
operating mechanism may be of the construction disclosed in commonly 
assigned and copending application Ser. No. 08/498,835 filed Jul. 6, 1995 
entitled "Load Arm for Load Lock", pending, the disclosure of which is 
incorporated herein in its entirety, by reference. 
With continuing reference to FIGS. 3 and 4, and with new reference to FIG. 
6, a multilevel end effector 84 is mounted on the load lock arm 82. As 
seen more clearly in FIG. 6, the multilevel end effector 84 includes a 
mounting manifold 86 which is suitably mounted on and projects upwardly 
from the load lock arm 82 and, more specifically, from an elongated joint 
88 of an articulated pair of such joints 88, 90 pivotally mounted on the 
load lock arm. A plurality of vertically spaced end effector sets 92 are 
integral with the mounting manifold and project outwardly from the 
mounting manifold in the direction of the carrier and lie in equally 
spaced parallel planes. 
The spacing between the end effector sets 92 is substantially greater than 
the thickness of a wafer 34 for reasons which will become clear as this 
description proceeds. Each end effector set 92 includes a pair of parallel 
laterally spaced end effector fingers 94 (see FIG. 7) which together are 
adapted to support a wafer in a generally horizontal plane. Each of the 
plurality of spaced end effector sets 92 is aligned with one of the rack 
member sets 36 when the load arm is in the active position and, therefore, 
with an associated wafer 34 supported in the carrier. In order for 
movement of the multilevel end effector 84 toward and into the carrier 32 
to commence in the manner about to be described, the load lock door 80 and 
the carrier door 42 must both be opened and moved to a remote location as 
seen in FIG. 8. 
The multilevel end effector 84 is then movable, when the load lock arm 82 
is in the active position, from a retracted position distant from the 
wafers to an advanced position within the interior 40 of the carrier 32 
and extending through the load lock port 78 and through the carrier port 
38 for engaging and simultaneously retrieving the wafers as a grouping. 
The load lock arm 82 is operated in such a manner as to proceed to move 
the multilevel end effector 84 to the left (FIG. 9) with each of the end 
effector sets 92 advancing beneath and out of engagement with its 
associated wafer 34. When the multilevel end effector 84 reaches its 
extreme leftward movement, the load lock arm, and with it the multilevel 
end effector 84, is raised a sufficient distance to lift the wafers, as a 
grouping, off their associated spaced rack member sets. Thereupon, while 
retaining that elevated positioning, the load lock arm 82 is again 
operated, this time in such a manner as to move the multilevel end 
effector 84 to the right, to the retracted position, for holding the 
grouping of the wafers 34 on the multilevel end effector 84 in the load 
lock chamber 76. See FIG. 11. 
After the grouping of the wafers 34 is so positioned on the multilevel end 
effector 84 in the load lock chamber 76, a transport arm 96 within the 
transport chamber 28 may be operated for retrieving the wafers 34, one at 
a time, from the multilevel end effector and delivering it to a specified 
one of the plurality of processing stations 24. 
In order to operate the multilevel end effector 84 in the manner just 
described, it is necessary first to coordinate the opening of the carrier 
door 42 and of the load lock door 80. The mechanism for achieving this 
coordinated operation will now be described. Initially, the carrier door 
is opened, then the load lock door is opened, then both doors together are 
moved to a location remote from the region between the interior of the 
carrier and the load lock chamber. 
The carrier door drive mechanism includes a coupling device 98 which is 
selectively engageable with the carrier door 42 and movable between a 
first position (FIG. 2) remote from the carrier door and adjacent the load 
lock door 80 and a second position (FIG. 3) adjacent the carrier door and 
remote from the load lock door. A first actuator 100 is mounted on the 
carrier door and, via a drive rod 102, serves to move the coupling device 
98 between the first and second positions. The coupling device includes a 
coupler frame 103 mounted on the drive rod and a pair of opposed axially 
aligned gripper members 104, 106 supported on and guided by the coupler 
frame. The gripper members 104,106 include opposed axially aligned gripper 
rods 108 which are supported on and guided by the coupler frame 103 for 
movement between non-gripping positions and the gripping positions. 
Specifically, each gripper member 104, 106 has a transverse gripper finger 
110 at its terminal end, the gripper fingers being engaged with a 
peripheral rim 112 of the carrier door 42 when the gripper members are in 
their gripping positions. 
Thus, the gripper fingers are movable between non-gripping positions (FIG. 
2) free of engagement with the carrier door 42 and gripping positions 
(FIG. 4) in gripping engagement with the peripheral rim 112. Such gripping 
engagement of the carrier door by the gripper members 104, 106 can only 
occur when the coupling device 98 is in the second position. A second 
actuator 114 on the coupler frame 103 serves to move the gripper members 
104, 106 between the non-gripping positions and the gripping positions via 
the suitably constrained gripper rods 108. 
Proceeding through the operational sequence for opening the carrier door 
42, operation of the first actuator 100 is initiated to move the coupling 
device 98 to the left to a location proximate the carrier door such that 
the gripper fingers 110 lie within the plane of the peripheral rim 112. 
Thereupon, operation of the second actuator 114 initiated to move the 
gripping members radially until the gripping fingers firmly engage the 
peripheral rim 112. Thereupon, the first actuator 100 is again operated, 
this time to move the coupling device toward the right thereby causing an 
extremity 116 of the inwardly directed flange 46 to withdraw from the seal 
48 which had, until now, maintained an environment isolated from the 
surrounding atmosphere. By means of the drive rod 102, the coupling device 
98 and, with it, the carrier door 42 are moved to the right to a position 
adjacent the load lock door 80. 
With the carrier door 42 so positioned adjacent the load lock door 80, a 
load lock door drive mechanism 118 is then operated for moving the load 
lock door and, with it, the unit comprising the coupling device 98 and the 
carrier door 42 from the closed position to the open position. In the 
closed position, the load lock door 80 is held firmly against a suitable 
seal 120 interposed between the load lock door and the load lock 22 for 
isolating the load lock chamber 76 from the atmosphere (see FIGS. 2 and 
12). This may be achieved, for example, by means of spaced, opposed, 
generally vertically oriented guide channels 121 integral with the load 
lock 22 and provided on opposite sides of the load lock door 80. 
The load lock door drive mechanism 118 includes a drive actuator 122 
mounted on a base 124 of the mini-environment 58. The drive actuator 122 
is vertically disposed with a drive actuator shaft 123 suitably attached 
to the load lock door 80 to move it between its raised closed position and 
a lowered open position remote from the region intermediate the carrier 
and the load lock chamber 76. 
It will be appreciated that operation of the multilevel end effector 84 
cannot be achieved until the drive mechanism 118 has been operated to move 
the load lock door, the coupling device 98, and the carrier door 42 all to 
the lowered position as indicated in FIG. 8. 
An index drive mechanism 126 is provided for moving the load lock arm 
between the inactive position (FIG. 11) and the active position (FIG. 10). 
As previously mentioned, the load lock arm 82 and its operating mechanism, 
herein the index drive mechanism 126, may be of the construction disclosed 
in commonly assigned and copending application Ser. No. 08/498,835 filed 
Jul. 6, 1995, pending. 
The index drive mechanism 126 includes a suitable index actuator 128 which 
is of the type which can advance an index actuator shaft 130, as desired, 
either in a macro fashion rapidly over a relatively long distance or in a 
micro fashion, that is, in incremental steps. Thus, the index actuator, in 
one mode of operation, can move the load lock arm between an active 
position (FIGS. 8-10) at which all of the end effector sets 92 are aligned 
with their associated rack member sets 36 in the interior 40 of the 
carrier 42 and an inactive position (FIG. 11) at which all of the end 
effector sets are not so aligned with their associated rack member sets. 
In the former instance, a clutch 132 is engaged; in the latter instance, 
the clutch is disengaged. 
An arm drive mechanism 134 includes a suitable rotary actuator for moving 
the load lock arm 82 and, with it, the multilevel end effector 84 between 
the retracted and advanced positions. The arm drive mechanism 134 further 
includes engageable clutch elements 132a and 132b which only engage when 
the index drive mechanism moves the load lock arm and the multilevel end 
effector to the active position. When that occurs, the end effector 84 can 
be advanced into the interior of the carrier as previously described. 
It was previously mentioned that a transport arm 96 within the transport 
chamber 28 may be operated for retrieving the wafers 34, one at a time, 
from the multilevel end effector and delivering it to a specified one of 
the plurality of processing stations 24. The index drive mechanism 126 may 
also be operated in its incremental mode to adjust the level of a 
particular end effector set 92 with robot end effector fingers 138 on the 
transport arm 96 within the transport chamber 28. In this manner, with the 
clutch elements 132a, 132b disengaged, the transport arm 96 driven by a 
transport actuator 140 is effective to retrieve wafers one at a time from 
the multilevel end effector 84 for delivery to a specified one of the 
processing stations 24. The transport arm 96 and its associated transport 
actuator 140 may be of the construction disclosed in commonly assigned 
U.S. Pat. No. 5,180,276 to Hendrickson, the disclosure of which is 
incorporated herein in it entirety, by reference. 
A suitable isolation valve 30, previously mentioned, is provided 
intermediate the load lock chamber 76 and the transport chamber 28. The 
isolation valve is sufficiently large to permit passage therethrough of 
the robot end effector fingers supporting a wafer 34 and is selectively 
operable to permit fluid intercommunication between the load lock chamber 
and the transport chamber in one instance and to prevent fluid 
intercommunication therebetween. 0f course, failure to permit fluid 
intercommunication between the chambers also results in prevention of 
passage therethrough of the robot end effector fingers supporting a wafer 
34. Additionally, a suitable seal 142 is interposed between the load lock 
22 and the transport chamber 28 for isolating the load lock and the 
transport chamber from the surrounding atmosphere when the isolation valve 
is positioned to permit fluid intercommunication between the load lock 
chamber and the transport chamber. 
A source of vacuum 144 is provided for selectively evacuating the load lock 
chamber 76 and the transport chamber 28. A conduit 146 extends between the 
source of vacuum 144 and the load lock chamber and a selectively operable 
valve 148 in the conduit 146 interconnects the vacuum source and the load 
lock chamber 76 when the load lock door 80 is closed and disconnects the 
vacuum source from the load lock chamber when the load lock door is open. 
In a similar manner, a conduit 150 extends between the source of vacuum 
144 and the transport chamber. A selectively operable valve 152 in the 
conduit 150 interconnects the vacuum source and the transport chamber when 
the transport chamber is isolated from the surrounding atmosphere. 
Turn now to FIGS. 13-15 for a description of another, and preferred, 
embodiment of the invention, namely, carrier door drive mechanism 160. In 
this instance, a carrier 162 is similar to the carrier 32 previously 
described for supporting and transporting a plurality of wafers 34 in 
spaced generally stacked relationship. As before, the carrier 162 has a 
carrier port 164 for providing access to its interior 166. Again, there is 
a mini-environment 168 for sealingly isolating the load lock chamber and 
the interior of the carrier from the surrounding atmosphere. Again, the 
carrier 162 includes a carrier door 170 which is movable between a closed 
position overlying the carrier port 164 for sealing the interior 166 from 
the surrounding atmosphere and an open position spaced from the carrier 
port. 
A load lock door 172 on the load lock is movable in the manner previously 
described between a closed position overlying the load lock port for 
sealing the load lock chamber from the surrounding atmosphere and an open 
position spaced therefrom. The carrier door drive mechanism and its 
operation are also as previously described. 
The mini-environment 168 has an aperture generally aligned with the load 
lock port but spaced therefrom and includes the platform 60 for supporting 
the carrier 162 thereon such that the carrier port 164 is proximate the 
aperture 174 in the mini-environment. A suitable seal 176 is provided 
between the mini-environment and the carrier when the carrier is supported 
on the platform and encompasses the carrier port and the aperture in the 
mini-environment for isolating the interior of the carrier, the interior 
of the mini-environment and the load lock chamber from the surrounding 
atmosphere. 
The carrier door drive mechanism 160 includes a coupling mechanism 178 
which is selectively engageable with the carrier door 170 and movable 
between a first position remote from the carrier door and adjacent the 
load lock door and (as depicted by broken lines in FIG. 13) and a second 
position adjacent the carrier door and remote from the load lock door (as 
depicted by solid lines in FIG. 13). A first actuator 180 is mounted on 
the load lock door 172 and includes a drive rod 182 for moving the 
coupling mechanism 178 between the first and second positions. 
The carrier door 170 is recessed as at 184 (FIGS. 14 and 15) and has a 
gripper slot 186 therein. The coupling mechanism 178 includes a door 
gripper plate 188 mounted on the drive rod 182 and matingly receivable 
with the carrier port 164 when the coupling mechanism is in the second 
position as mentioned earlier. A door gripper bar 190 on a second actuator 
192 which, in turn, is mounted on the door gripper plate 188 has a pair of 
bent fingers 194 at a distal end thereof movable between a gripping 
position grippingly engaging the gripper slot 186 in the carrier door 170 
and a release position disengaged therefrom. 
Additionally, a latch mechanism 196 is provided on the carrier door for 
selective engagement with the carrier for securely attaching the carrier 
door to the carrier. For this purpose, the carrier 162 has a latch recess 
198 (FIG. 14) in the carrier port 164. Cooperating with the latch recess 
198, the latch mechanism 196 includes a latch 200 pivotally mounted, as at 
201, on the carrier door 170 for movement between a latching position 
engaged with the latch recess and an unlatching position disengaged from 
the latch recess. A retention pin 202 is pivotally connected to the latch 
at a first end 204 within the recess 184 and has a second turned end 206 
opposite the first end. The turned end 206 is receivable in a slot 208 
between the pair of bent fingers 194 and is engageable with the door 
gripper bar 190. 
A compression spring 210 encircles the retention pin 202 and is suitably 
supported within the recess 184 for biasing the latch 200 to the latching 
position. At its left end (viewing FIGS. 14 and 15) the spring is seated 
against opposed shoulder members 212 which project into the recess from 
opposite walls of the recess 198 in the carrier door 170. The right end of 
the spring 210 bears against a c-clamp 214 fixed to the retention pin 202 
an appropriate distance from the shoulder members 212. With this 
construction, the retention pin and its second, turned, end 206 is biased 
toward the right, viewing FIGS. 13-15. In this manner, the spring 210 is 
effective to hold the latch 200 in a normally closed position in 
engagement with the latch recess 198. However, the movement of the door 
gripper bar 190 to move the pair of bent fingers 194 into the gripping 
position grippingly engaging the gripper slot 186 is effective to 
simultaneously move the latch to the unlatching position disengaged from 
the latch recess. With continued operation of the actuator 192 to hold the 
bent fingers 194 in engagement with the gripper slot 186 and to hold the 
latch 200 swung in the open position (all as shown in FIG. 14), the 
carrier door 170 and the door gripper plate 188 operate as a unit and can 
be moved by the actuator 180 to the open, broken line, position indicated 
in FIG. 13. 
While preferred embodiments of the invention have been disclosed in detail, 
it should be understood by those skilled in the art that various other 
modifications may be made to the illustrated embodiments without departing 
from the scope of the invention as described in the specification and 
defined in the appended claims.