Multiple independent robot assembly and apparatus for processing and transferring semiconductor wafers

A robot assembly including multiple independently operable robot assemblies are provided for use in semiconductor wafer processing. The robot assembly includes independent co-axial upper and lower robot assemblies adapted to handle multiple objects. The upper robot is stacked above the lower robot and the two robots are mounted concentrically to allow fast wafer transfer. Concentric drive mechanisms may also be provided for imparting rotary motion to either rotate the robot assembly or extend an extendable arm assembly into an adjacent chamber. Each robot can be either a single blade robot or a dual blade robot. Also provided is an apparatus for processing semiconductor wafers comprising a pre/post process transfer chamber housing multiple independent robot assemblies and surrounded by a plurality of pre-process chambers and post process chambers. Within each process, pre-process and post-process chamber is an apparatus for holding a plurality of stacked wafers. The apparatus includes a wafer lifting and storing apparatus exhibiting a plurality of vertically movable lift pins surrounding the chamber pedestal. The lift pins are configured to receive and hold a plurality of stacked wafers, preferably two, therein.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for transferring objects, and 
more particularly to multiple independent robot assemblies for the 
simultaneous and independent manipulation of multiple objects, such as 
semiconductor wafers. 
The use of robot arms is a well established manufacturing expedient in 
applications where human handling is inefficient and/or undesired. For 
example, in the semiconductor arts robot arms are used to handle wafers 
during various process steps. Such process steps include those which occur 
in a reaction chamber, e.g. etching, deposition, passivation, etc., where 
a sealed environment must be maintained to limit the likelihood of 
contamination and to ensure that various specific processing conditions 
are provided. 
Current practice includes the use of robot arms to load semiconductor 
wafers from a loading port into various processing ports within a multiple 
process chamber system. The robot arms are then employed to retrieve the 
wafer from a particular port after processing within an associated process 
chamber. The wafer is then shuttled by the robot arms to a next port for 
additional processing. When all processing of the wafer within the system 
is complete, the robot arm returns the semiconductor wafer to the loading 
port and a next wafer is placed into the system by the robot arm for 
processing. Typically, a stack of several semiconductor wafers is handled 
in this manner during each process run, and several wafers are passing 
through the system simultaneously. 
In multiple chamber process systems, it is desirable to have more than one 
semiconductor wafer in process at a time. In this way, the process system 
is used to obtain maximum throughput. A typical wafer handling sequence to 
switch wafers in a process chamber is to remove a wafer from a process 
chamber, store the wafer in a selected location, pick a new wafer from a 
storage location, and then place the new wafer in the process chamber. 
Although this improves use of the system and provides improved throughput, 
the robot arm itself must go through significant repetitive motion to 
simply exchange wafers. 
To increase the efficiency of robot handling of wafers, a robot arm having 
the ability to handle two wafers at the same time may be provided. Thus, 
some equipment manufacturers have provided a robot in which two carrier 
arms are located at opposed ends of a support, and the support is rotated 
about a pivot. In this way, one wafer may be stored on one arm while the 
other arm is used to retrieve and place a second wafer. The arms are then 
rotated and the stored wafer may be placed as desired. Such a mechanism 
does not allow the two arms to be present in the same process chamber at 
the same time, nor does it allow for the immediate replacement of a fresh 
wafer in a process chamber after a processed wafer is removed, because the 
support must be rotated 180.degree. to place the wafer on the second arm 
in a position for loading into the location from which the first wafer was 
removed. Likewise, simultaneous use of the two arms for placement or 
removal of wafers from process or storage positions is not possible with 
this configuration. 
Another robot configuration includes a central hub having two opposed arms, 
each arm arranged for rotation relative to the hub while arcuately fixed 
in relation to one another. A blade is linked to the free ends of the 
arms, and a drive is provided for rotating the arms in opposite directions 
from each other to extend the blade radially from the central hub, and in 
the same direction to effect a circular movement of the blade about the 
central hub. Preferably, a second pair of arms extend opposed from the 
first pair, on the ends of which is connected a second blade. Opposed 
rotation of the arms in one direction extends the first arm while 
retracting the second arm. Opposed rotation of the arms in the opposite 
direction results in retraction of the first arm and extension of the 
second arm. Simultaneous motion of the arms in the same direction swings 
the blades in a circular or orbital path around the hub. The use of two 
blades increases throughput. However, this device still does not permit 
simultaneous insertion of a fresh wafer into a process chamber as a 
processed wafer is being withdrawn from the same chamber, or independent 
use of the blades to simultaneous load into wafers, unload from, wafers or 
move a wafer between one or more chambers while a second wafer is being 
loaded or unloaded. 
SUMMARY OF THE INVENTION 
The present invention is a multiple robot assembly including at least 
co-axial upper and lower robot assemblies. The upper robot operates 
independently of the lower robot to obtain improved throughput and 
increased wafer handling capacity of the robot assembly as compared to the 
prior art opposed dual blade robots. The upper robot may be stacked above 
the lower robot and the two robots may be mounted concentrically to allow 
fast wafer transfer. Each robot can be either a single blade robot or a 
dual blade robot. 
According to one aspect of the invention, each of the upper and lower robot 
assemblies is a dual blade robot including a pair of extendable arm 
assemblies located within a transfer chamber. Each pair of extendable arm 
assemblies includes a corresponding pair of carrier blades for handling 
various objects, such as semiconductor wafers. The upper robot may be 
provided with a drive mechanism for rotating the pair of extendable arm 
assemblies or for extending one of the arm assemblies into an adjacent 
chamber. The lower robot may also be provided with a drive mechanism that 
is co-axial with the upper robot drive mechanism. The lower robot drive 
mechanism may also function to either rotate the pair of extendable arm 
assemblies or to extend one of the arm assemblies into an adjacent 
chamber. 
According to another aspect of the invention, each of the upper and lower 
robot assemblies is a single blade robot including an extendable arm 
assembly located within a transfer chamber. Each extendable arm assembly 
includes a corresponding carrier blade for handling various objects, such 
as semiconductor wafers. The upper and lower robot assemblies may be 
provided with a drive mechanism for rotating the extendable arm assembly 
or for extending their arm assemblies into an adjacent chamber. 
In a further aspect of the invention, a central transfer chamber is linked 
to multiple object rest positions, and each of the rest positions may be 
independently and, if desired, simultaneously accessed by at least two 
robot assemblies. 
A still further aspect of the present invention is an apparatus for holding 
a plurality of articles within a chamber, such as a pre-process chamber, 
process chamber or post-process chamber, with a pedestal centrally located 
and vertically movable therein. The apparatus exhibits a wafer lifting and 
storing apparatus including a plurality of vertically movable lift pins 
surrounding the pedestal. The lift pins are configured to receive and hold 
a plurality of stacked wafers, preferably two, therein. Each one of the 
plurality of lift pins preferably comprises a lower lift pin segment 
exhibiting a lower wafer support surface proximal to the upper end 
thereof, and an upper lift pin segment hingedly connected to the lower 
lift pin segment and exhibiting an upper wafer support surface proximal to 
an upper end thereof. Means for moving the upper lift pin segment between 
a position in which the lower lift pin segment is exposed and a position 
wherein the lower lift pin segment is covered by the upper lift pin 
segment may also be provided.

DETAILED DESCRIPTION 
The present invention is best understood by referring to the Drawings in 
connection with review of this Description. The present invention is a 
multiple robot assembly including at least independent co-axial upper and 
lower robot assemblies adapted to simultaneously handle multiple objects. 
In a preferred embodiment, the upper robot is stacked above the lower 
robot and the two robots are mounted concentrically to a drive hub to 
allow simultaneous transfer of two wafers between a transfer chamber and 
one or more process chambers. Concentric drive mechanisms may also be 
provided for imparting rotary motion to the connection of the robot 
assembly to the hub to either move the robot assembly in an orbital path 
about the hub, ie, in a sweeping motion, or to extend an extendable arm 
assembly of the robot assembly. Each robot can be either a single blade 
robot or a dual blade robot. The invention may preferably be used in a 
semiconductor wafer processing system. 
The present invention allows multiple objects, such as semiconductor 
wafers, to be handled simultaneously for either extension or retraction, 
with respect to a process chamber position, or rotation about a hub, such 
that a wafer exchange in a process chamber can rapidly be made. For 
instance, a wafer which has just completed processing in a processing 
module can be withdrawn from the module while a fresh wafer is 
simultaneously being inserted into the same processing module, without the 
need to swing the robot arm to locate an opposed robot arm in position to 
insert a new wafer. Alternatively, one robot can be inserting or 
withdrawing a wafer from one processing module while the other robot is 
independently inserting or withdrawing a wafer from another process 
module, even where the access to the two chambers are not co-linearly 
opposed (FIG. 7). Likewise, a wafer may be removed from a process module, 
and a new wafer inserted therein, without the need to rotate the robot 
assembly 180.degree. to affect insertion of the new wafer into the module. 
It is also possible to use the dual robot assembly to simultaneously 
insert a pair of wafers into, or withdraw a pair of wafers from the same 
process module at the same time, provided adequate clearance is maintained 
between the stacked robot assemblies. These unique features enable 
increased throughput of wafers during wafer processing when contrasted to 
prior art robot assemblies, as there is no "dead-time" of one of the 
blades while a processed wafer is replaced within the process module by a 
fresh wafer, or, as the robot has to either rotate 180.degree. where dual, 
opposed, blades are used, or where the removed wafer must be placed in a 
rest location, and a new wafer positioned on the robot and then 
transferred to the process chamber. 
In FIG. 1, one embodiment of a dual robot assembly 10 is shown in the 
context of a semiconductor wafer processing system, when one arm of each 
robot is shown extended into an adjacent chamber 18a, while an opposed arm 
of each robot is fully retracted into the transfer chamber 12 from an 
additional chamber 18b. In this Figure, as well as FIGS. 3, 6, and 9, the 
size of the assembly within which the robot arm drive components are 
located has been exaggerated to enhance detail. The exemplary processing 
system includes a transfer chamber 12, within which the robot assembly 10 
is mounted, which is connected to at least two additional chambers 18a, 
18b. The chambers 18a, 18b may be process chambers, wafer holding 
chambers, loadlock chambers, etc., into which wafers may be located for 
wafer processing and then removed. The dual robot assembly 10 is centrally 
arranged within the transfer chamber 12 of the wafer processing system, 
wherein the upper robot 14 is preferably connected to an upper 
superstructure (or wall) 12a of the transfer chamber 12 and a lower robot 
16 is preferably connected to the bottom wall 12b of the transfer chamber 
12. The upper and lower robots 14, 16 are arranged within the transfer 
chamber 12 such that semiconductor wafers W (best shown in FIG. 2) can be 
transferred to and between wafer rest positions adjacent process or 
reaction chambers 18a, 18b, through apertures between the transfer chamber 
12 and process chambers 18a, 18b. Preferably, the aperture between the 
transfer chamber and process chamber is valved, such as with valves 20a, 
20b, respectively, so that a process or conditioning environment may be 
maintained in process chambers 18a, 18b without affecting the environment 
in the transfer chamber. However, the invention has equal utility where 
the aperture is not valved. The valves 20a, 20b, where used, may be 
Vat.RTM. valves or vat type valves as shown in FIG. 1, alternatively, 
pocket valves, gate type valves, flap type valves, slit valves such as 
those shown and described in U.S. Pat. No. 5,226,632, incorporated herein 
by reference, or other valves known in the art for separating adjacent 
chambers and controlling the passage or port therebetween may be used. It 
should be noted that although the exemplary embodiment of the invention 
shown in FIG. 1 shows a dual robot assembly centrally located within the 
central transfer chamber of a multi chamber wafer processing system, with 
the system including two shown process or reaction chambers (other's being 
blocked by the robot or in the portion removed for sectional viewing). The 
present invention is intended for many different applications, 
particularly those having multiple process and wafer handling chambers 
ported to a transfer chamber. Additionally, it is specifically 
contemplated that several transfer chambers may be ganged together, with 
or without load-locked passages therebetween, and the robot(s) of the 
present invention may be located in one or all of the transfer chambers. 
Thus, the exemplary embodiment should not be considered as limiting the 
scope of the invention. The present invention is readily adapted for use 
with any wafer handling application, including process systems having any 
number of process chambers and any sort of orientation for the dual robot 
assembly. 
Referring still to FIG. 1, a specific configuration of an upper robot 14 
includes a first drive arm 21 and a second drive arm 22 arranged such that 
one end of each arm is independently coupled to a central hub 23. The end 
of each arm 21, 22 coupled to the hub 23 may be moved independently of the 
other arm in either a clockwise or a counter-clockwise fashion about the 
hub 23, enabling the arms 21, 22 to be moved in either the same or opposed 
directions. Movement may be accomplished by any type of drive mechanism, 
such as an electrical, magnetic or electromagnetic motor or motors. The 
drive mechanism is preferably configured to move drive arm 21 and drive 
arm 22 in either opposing directions or in the same direction. By moving 
the hub end of the arms 21, 22 in the same direction about the hub axis A, 
the robot moves in a circular or orbital path about the hub. By moving the 
hub ends of the arms in opposite directions about the hub axis A, 
extension and retraction of the robot is affected. When arm 21 is moved 
clockwise (from a perspective above cover 12a) and arm 22 is rotated 
counterclockwise, the robot blade attached to the arms 21, 22 extends from 
the hub. When the rotation is reversed, that blade retracts toward the 
hub. 
Referring still to FIG. 1, there is shown an enlarged view of the preferred 
robot drive system. This drive system is the preferred drive system for 
each embodiment of the robot described herein. In the embodiment shown, 
each of the upper robot and lower robot assemblies are driven by separate 
magnetic coupling assemblies 1000, 1002 (shown in FIG. 1). The details of 
construction of each magnetic coupling assembly 1000, 1002 are identical, 
except as noted herein. Therefore, only the construction of upper magnetic 
coupling assembly will be discussed. 
Magnetic coupling assembly 1000 is configured to provide arcuate motion of 
arms 21, 22, about axis A, thereby enabling extension and retraction of 
the two robot blades 33, 40 from the hub, and passage of the blades in a 
orbital path about the hub. Additionally, the magnetic coupling assembly 
1000 provides this motion with minimal contacting moving parts within the 
vacuum to minimize particle generation in the vacuum. In this embodiment 
these robot features are provided by fixing first and second syncro motors 
1004, 1006 in a housing 1008 located atop the transfer chamber, and 
coupling the output of the motors 1004, 1006 to magnet ring assemblies 
1010, 1012 located inwardly and adjacent a thin walled section 1014 of 
housing 1008. The thin walled section 1014 is connected to the upper wall 
or cover 12a of the transfer chamber 12 at a sealed connection to seal the 
interior of the transfer chamber 12 from the environment outside of the 
chambers. Driven magnet rings 1016, 1018 are located on the vacuum side of 
housing 1008, adjacent to and surrounding thin walled section 1014 of 
housing 1008. The first magnetic ring assembly 1010 magnetically couples 
to first driven magnetic ring assembly 1016 and the second magnetic ring 
1012 couples to the second driven magnetic ring assembly 1018. Arms 21, 22 
are coupled to receptive ones of the driven magnet rings 1016, 1018. Thus, 
rotary motion of the motors 1002, 1004 is magnetically transferred from 
the atmospheric to vacuum side of the housing 1008, to cause arcuate 
motion of arms 21, 22 to affect movement of the robot blades 33, 40 (FIG. 
1). 
The preferred motor 1004, 1006 construction is a servo motor with a 
synchronous device, wherein a stator is coupled to a rotor and the arcuate 
position of the rotor may be closely controlled. As shown in FIG. 1, each 
motor 1004, 1006 is attached to the housing 1008, at support 1009 such 
that the rotors thereof are directly coupled to the first magnetic ring 
assembly 1010 and second magnetic ring assembly 1012. The output of motor 
1004 is directly coupled to magnetic ring assembly 1010, and motor 1006 is 
coupled to magnetic ring assembly 1012 by extending a shaft 1030 from the 
rotor of motor 1006 and through the center of motors 1004, 1006 where it 
connects to second magnetic ring assembly 1012. Shaft 1030 is preferably 
pivotal and supported on bearing 1032 and internal bearings (not shown) in 
each motor 1004, 1006 between each stator-rotor set ensure centering of 
the shaft 1030. 
Rotation of the motor output thereby causes rotation of the magnet ring 
assemblies 1010, 1012, which magnetically couple to driven magnetic ring 
assemblies 1016, 1018, thereby rotating the base of each arm around the 
perimeter of thin walled section 1014 to affect movement of the blades. 
Operation of the robot blades in and out of valves requires close vertical 
(where the transfer of wafers is horizontal) tolerance on the position of 
the robot blade, to ensure that it, or the wafer attached thereto, does 
not hit the structure of the chamber as it passes through the valve. To 
provide this vertical positioning, the support 1009 extends from between 
motors 1004, 1006 to a flange 1011 which is connected to cover 12a. The 
support 1009, flange 1011 and flange to support distance are sized, with 
respect to the size and tolerance of the robot assemblies, transfer 
chamber 12 and valves 20a, 20b, to ensure that a blade 33, 40 with a wafer 
W thereon will not contact the structure of the chambers or valves. To 
suspend the driven magnetic ring assemblies 1016, 1018, and enable 
rotation thereof relative to the hub 1008, the first driven magnetic ring 
assembly 1018 includes an annular arm support 1040, which is received 
over, and hangs on, race of a first bearing 1042. The first bearing 1042 
is clamped, over its inner race, to the thin walled section 1014. The 
outer race of a second bearing 1044 is clamped to the ring 1040, and ledge 
portion 1046 of the second magnetic ring assembly 1016 is clamped to race 
of the second bearing, securing the second driven magnetic ring assembly 
1018 to the housing 1008. 
Each bearing, is a "cross" type bearing, which provides radial and 
longitudinal, in this case elevational, support to ensure alignment and 
positioning of the driven magnetic ring assemblies 1016, 1018. 
To couple each magnet ring assembly 1010, 1012 to its respective driven 
magnetic ring assembly 1016, 1018, each magnet ring assembly 1010, 1012 
and driven magnetic ring assembly 1016, 1018 preferably include an equal 
plurality of magnets, each magnet on the magnet ring assemblies 1010, 1012 
coupled to one magnet on the driven magnetic ring assembly 1016, 1018. To 
increase coupling effectiveness, the magnets may be positioned with their 
poles aligned vertically, with pole pieces extending therefrom and toward 
the adjacent magnet to which it is coupled. The magnets which are coupled 
are flipped, magnetically, so that north pole to south pole coupling 
occurs at each pair of pole pieces located on either side of the thin 
walled section. 
Lower robot assembly 16 is substantially identical in construction to upper 
robot assembly, except the housing 1008' thereof is suspended from the 
transfer chamber 12, and the driven magnetic ring assemblies 1016', 1018', 
are supported on bearings which rest upon the base of the transfer chamber 
12. 
As best shown in FIGS. 2 and 4 (FIG. 4 being a simplified schematic of FIG. 
2), a pair of extendable arm assemblies are connected to the ends of the 
drive arms 21, 22 to form a pair of compound articulated mechanisms which 
are sometimes referred to in the mechanical arts as frog-leg mechanisms. 
The first extendable arm assembly includes a pair of strut arms 29, 30 
pivotally coupled to the ends of drive arms 21, 22, respectively, at 
respective pivot points 31, 32. The strut arms 29, 30, in turn, are 
coupled by pivots 34, 35 to a first wafer carrier or robot blade 33 which 
forms the object support. The second extendable arm assembly similarly 
includes a pair of strut arms 36, 37 pivotally coupled to the ends of 
drive arms 21, 22, respectively, at respective pivot points 38, 39. The 
strut arms 36, 37 in turn, are coupled by pivots 41, 42 to a second wafer 
carrier or robot blade 40. Each strut arm 29, 30, 36, 37 may include a 
meshing gear 49, shown in FIG. 4, at an end within the carrier 40 (or 33) 
to maintain the carrier in rigid radial alignment with the hub 23 as the 
struts are pivoted during operation of the robot. The first and second 
wafer carriers 33, 40 are maintained 180.degree. apart from each other 
about the axis of the hub. In FIG. 1, the wafer carrier 33 is shown in a 
fully extended position for delivering or retrieving a wafer from reaction 
chamber 18a. 
Like the upper robot, the lower robot 16 includes a first drive arm 51 and 
a second drive arm 52 arranged such that one end of each arm is coupled to 
a central hub 53. The manner of moving the components of the lower robot 
are identical to that described above in connection with the upper robot. 
Similarly, the drive mechanism of the lower robot is identical to that of 
the upper robot. 
Also like the upper robot, in the lower robot 16, a pair of extendable arms 
assemblies are connected to the ends of the drive arms 51, 52 to form a 
pair of frog-leg mechanisms. The first extendable arm assembly includes a 
pair of strut arms 59, 60 pivotally coupled to the ends of drive arms 51, 
52, respectively, at respective pivot points 61, 62. The strut arms 59, 
60, in turn, are coupled by pivots 64, 65 to a first wafer carrier 63. The 
second extendable arm assembly similarly includes a pair of strut arms 66, 
67 pivotally coupled to the ends of drive arms 51, 52, respectively, at 
respective pivot points 68, 69. The strut arms 66, 67 in turn, are coupled 
by pivots 71, 72 to a second wafer carrier 70. Each strut arm 59, 60, 66, 
67 may include a meshing gear 49, shown in FIG. 4, at an end within the 
carrier 70 to maintain the carrier in rigid radial alignment with the hub 
53 as the strut arms are pivoted during operation of the robot. The first 
and second robot blades or carriers, 63, 70 of each robot assembly are 
maintained 180.degree. apart from each other about the axis of the hub. In 
FIG. 1, the wafer carrier 63 is shown in a fully extended position for 
delivering or retrieving a wafer from chamber 18a and blade 70 is fully 
retracted from chamber 18b, as is necessitated where a double frog-leg 
arrangement is used for each robot assembly. In FIG. 2, both wafer 
carriers 63, 70 are shown retracted from adjacent process chambers. 
Referring still to FIGS. 2 and 3, there is shown a detailed side sectional 
view of the dual robot assembly of FIG. 2 wherein, all four wafer carriers 
are in the retracted position and in a transfer chamber 12. To aid 
interpretation of FIGS. 2 and 3, FIG. 4 shows a simplified plan view of 
the dual robot assembly 10. As shown in FIG. 3, the upper robot arm 
assemblies and lower arm assemblies are positioned, with respect to a slit 
valve 20a aperture, such that a robot blade 33 or 63 (or 40 or 70) from 
the upper and lower robot assemblies may be passed through the slit valve 
20a aperture without the need to change the elevation of the robot arms 
with respect to the aperture. Thus uniquely, either, or both, of an upper 
and lower robot carriers 33 and/or 63 (or 40 and or 70) may be passed 
through the aperture to affect wafer transport to or from the process 
chamber 18a without the need to swing a robot arm through a significant 
arc to position the second of the two carriers into a slit valve chamber 
access position. Another feature of the invention is that the upper robot 
assembly 14 can operate completely independently of the lower robot 
assembly 16, allowing the robot assemblies to transfer wafers to or from 
any chamber, including the same chamber, unimpeded by the presence of the 
other robot in the transfer chamber. High speed wafer transfer may be 
accomplished by one robot removing a wafer from a process chamber while 
the other robot simultaneously inserts a fresh wafer into the same process 
chamber, or by enabling simultaneous loading or unloading of different 
chambers, or simultaneous transfer of a wafer in or out of a chamber while 
a second wafer is moving in a path about the hub and between chambers. 
Additionally, each robot may rotate entirely past the other, enabling any 
combination or movement of the upper carriers 33, 40 with respect to the 
lower carriers 63, 70. 
It should be noted that although FIGS. 1-4 show each of the upper and lower 
robot assemblies 14, 16 being configured as dual blade robots, i.e. two 
frog-leg mechanisms each connected to a separate wafer carrier, either the 
upper robot, the lower robot, or both can be a single blade robot. As 
shown in FIGS. 5-10, a dual robot assembly is provided wherein both the 
upper and lower robots are single blade robots. 
An alternative embodiment of the invention is shown in FIGS. 5-7. In this 
embodiment, the dual robot assembly 110 is centrally arranged within the 
transfer chamber 112 of the reaction system as described with respect to 
FIGS. 1 to 4, but a central column 120 spans the gap between the base and 
cover of the transfer chamber 112. This column 120 ensures that the 
spacing between the chamber cover and base will remain constant. The 
column includes an annular clearance recess 121, which provides space for 
the manipulation of the various arms and carriers of the two robot 
assemblies 14, 16. Preferably, the column is provided by extending the 
thin walled sections 114, 114' of the FIG. 1 embodiment through a necked 
down region across the gap between the robot assemblies 14, 16 in the 
transfer chamber 112. Preferably, the thin walled section is formed of 
nonmagnetic stainless or other material capable of having a magnetic field 
passed therethrough. 
According to this embodiment, two robots 14, 16 are provided in the 
transfer chamber, each robot with a single blade assembly. Each robot is 
unrestrained in motion by the other robot, and both robots have 
independent access to all process chambers surrounding the transfer 
chamber. According to one preferred use, the robots are capable of 
simultaneously removing two separate wafers from one or more loadlocks. 
High speed wafer transfer may be accomplished by one robot removing a 
processed wafer from a process chamber while the other robot 
simultaneously delivers a fresh wafer to the same process chamber, by 
simultaneously moving wafer in and out of adjacent or non-adjacent wafer 
cassettes, and by other simultaneous and independent movement of wafers 
through a multi-chamber process device. Additionally, each robot assembly 
14, 16 could be a dual blade assembly as shown and described with respect 
to FIGS. 1-4. 
Referring now to FIGS. 8 to 10, a still further embodiment of the invention 
is shown, wherein the motors for the two robot assemblies 14, 16 are 
suspended from the transfer chamber. To couple the motor outputs to the 
driving magnetic ring assemblies, 1010, 1012, 1010', 1012' for each robot 
assembly, the outputs of the drive motors are coupled to staggered 
concentric shafts, each of which is coupled to a driving magnetic ring 
assembly. 
Referring to FIG. 9, the drive system includes four motors 1004, 1006, 
1004', 1006', having an identical construction as the motor assemblies 
1004, 1006 previously described, coupled to a hub 1100 having the same 
general construction as the central column described with respect to FIGS. 
5 to 7. In contrast to the previous embodiments, motors 1004, 1006, for 
driving the upper robot assembly are suspended below the motors 1004', 
1006' for driving the lower robot assembly, and an additional pair of 
concentric shafts extend from the upper robot assembly motors 1004, 1006 
through the center of the lower robot assembly motors 1004', 1006' and the 
hub 1100, wherein they are connected to magnet ring assemblies 1010, 1012 
as previously described. A simplified view of the single blade, dual 
independent embodiment of the invention is shown in FIG. 10, wherein the 
central column 120 is shrunken in size to better illustrate the linkages 
of the apparatus. 
The drive motors 1004, 1006, 1004', 1006' are housed in an extended housing 
1070, connected to the underside of the transfer chamber 12. The housing 
1070 includes a pair of motor support flanges 1072, 1074 therein, to each 
of which one of upper robot assembly motors 1004, 1006 or lower robot 
assemblies 1004', 1006' are connected for support and alignment. To 
support driving magnetic ring assembly 1012' in column 120, the rotor, or 
output of motor 1004' includes a drive flange 1080 extending therefrom and 
connected to the driving ring assembly. Thus, the flange 1080 provides 
support and rotation to the driven magnetic ring 1012'. The output of 
lower magnetic ring assembly motor 1006' is coupled to a hollow shaft 1082 
which extends through motors 1006', 1004' and flange 1080 where it 
attaches to lower magnetic ring assembly 1010' which is supported on lower 
magnetic ring assembly 1012' by a bearing 1084. Bearing 1084 is preferably 
piloted into the ends of both shaft 1082 and flange 1080. A second shaft 
1086 extends from motor 1006, through shaft 1082 and the necked down 
portion of the hub 120 to upper magnetic ring assembly 1010 which is 
supported on a bearing 1088 connected to the upper surface of the magnetic 
ring assembly 1010'. The output for motor 1004 is coupled to shaft 1090 
which extends through shaft 1086 and connects to magnetic ring assembly 
1012 supported on a bearing 1092 connecting magnetic ring assemblies 1010, 
1012. 
In the embodiment of the invention shown in FIGS. 5 to 7 and FIGS. 8 to 10, 
the robot assemblies are shown as single blade robots, i.e., where each 
robot assembly includes only a single robot blade, carrier or end 
effector. Each embodiment of the drive system may be used with either a 
single or dual blade robot, and, if desired, a single and a dual blade 
robot may be used in a single transfer chamber. Referring again to FIGS. 5 
to 7, each single blade robot assembly is provided with the same structure 
as the robot assemblies, including the drive arms 21, 22, (51, 52 in the 
lower robot assembly 16) coupled to the motors 1004, 1006 and magnetic 
coupling assemblies 1000, 1002 but, only one pair of strut arms 29, 30 
(or, in the lower robot assembly, strut arms 29', 30') coupled to a 
carrier (blade or effector). Thus, unlike the embodiment shown in FIGS. 1 
to 4, each robot assembly 14, 16 can manipulate only a single robot blade, 
and thus only a single wafer, at any time. FIG. 5 shows the retracted 
position for the robot assemblies, and FIG. 7 shows the upper robot 
assembly 14 extended over the lower robot assembly 16 and into an adjacent 
process chamber. By placing an upper robot assembly 14 over, and in 
coaxial alignment with, a lower robot assembly 16, the two robot 
assemblies can be manipulated past one another, an can simultaneously 
access a single wafer rest position, such as a transfer chamber, thereby 
enabling rapid deployment and replacement of wafers in the system. 
A fourth embodiment of the dual robot assembly of the present invention is 
shown in FIGS. 11 & 12. The dual robot assembly 200 according to this 
embodiment includes a central hub 210 about which a pair of single blade 
robots 212a, 212b are rotatably mounted. Each robot 212a, 212b includes a 
drive arm 214a, 214b and a secondary arm 216a, 216b which are connected to 
one another at a pivot joint 218a, 218b. A robot blade 220a, 220b is 
provided with each robot 212a, 212b for cradling a wafer during transfer. 
The robot blades 220a, 220b are connected to one end of the robot drive 
arm 214a, 214b at a pivot joint 222a, 222b and to one end of the secondary 
arm 216a, 216b at a second pivot joint 224a, 224b. As best shown in FIG. 
12, the end effectors 220a, 220b are preferably co-planar in the plane of 
a slit valve. Therefore, each robot's range of rotation about the central 
hub 210 is limited by the relative position of the other robot. The other 
end of each of the drive arms 214a, 214b are pivotally connected to a 
drive block 226a, 226b which are supported on the outer races of bearings 
228a, 228b located on the central hub 210. Similarly, the second end of 
the secondary arms 216a, 216b are pivotally connected to secondary blocks 
230a, 230b which are supported on secondary bearings 232a, 232b in the 
central hub 210. The bearings are preferably situated in a vacuum 
environment. Preferably, each bearing is a "cross" type bearing exhibiting 
both radial and vertical support which is press fit over a central hollow 
shaft to provide position and support for each robot's arms and blades. 
To provide motion to drive arms 214a, 214b of each robot 212a, 212b a 
central drive assembly 1200 is provided. This central drive assembly 1200 
extends inwardly of the chamber 12 to provide positioning and support for 
each robot 212a, 212b, and to provide a coupling mechanism whereby driving 
members providing energy to move the drive arms 214a, 214b located within 
the central drive assembly 1200 and maintained in atmosphere, and driven 
members located on the exterior of the coupling mechanism and physically 
linked to the robots 212a, 212b and non-physically coupled to the driving 
members. 
In the preferred implementation of the invention, the motor and magnet ring 
assembly of FIG. 1 is used to control the movement, or non-movement, of 
each drive arm 214a, 214b. To provide this, the drive system of FIG. 1 is 
modified, such that the driven magnetic rings 1016, 1018 are attached, 
such as by bolts, to the outer races of the bearings 232a, 232b. 
To extend the robot blade the drive block is moved in the direction of the 
secondary block by actuating motor 1004 magnetically coupled to bearing 
232a, which is held stationary by preventing rotation of motor 1006 
magnetically coupled to the outer race of the bearing 232b. Similarly, to 
retract the robot blade, the drive block is moved away from the stationary 
secondary block. Movement of the blocks toward one another causes 
extension of the robot arm. Movement of the blocks away from one another 
causes the robot arm to be retracted. 
The robot 212a, 212b is rotated about the hub by rotating the drive block 
with motor 1004 while simultaneously rotating the secondary block with 
motor 1006 in synchronism with the movement of the drive block. 
As shown in FIG. 13, the dual robot assembly of the present invention is 
preferably utilized to transfer semiconductor wafers between individual 
chambers to affect wafer, processing. FIG. 13 shows a first dual robot 
assembly 200 positioned within a first transfer chamber 234, and a second 
dual robot assembly 200' positioned within a second transfer chamber 236. 
First and second loadlock chambers 238, 240, for loadlocked transfer of 
wafers between atmosphere and first transfer chamber 234 are coupled to 
first transfer chamber 234. First and second pass through chambers 248, 
250 connect first and second transfer chambers 234, 236 to enable the 
passage of wafers W therebetween. Although FIG. 13 shows dual robot 
assemblies according to the fourth embodiment of the present invention, 
any dual blade robot capable of simultaneous independent transfer of two 
wafers such as are disclosed in the other embodiments of the present 
invention, may effectively be used. 
An entry loadlock 238 and an exit loadlock 240 are positioned about the 
periphery of the pre/post process transfer chamber 234 for transferring 
wafers into and out of the system. A plurality of process chambers, such 
as de-gas chamber 242 and preclean chamber 244, and post-processing 
chambers 246 are also positioned about the first transfer chamber 234 for 
carrying out a variety of operations. A plurality of process chambers 252, 
254, 256, 258 may be positioned around the periphery of the process 
transfer chamber 236 for performing various process operations, such as 
etching, deposition, etc. on semiconductor wafers. 
According to the present invention, each of the chambers 242, 244, 246, 
252, 254, 256, 258 are configured to simultaneously hold two wafers within 
the chamber during wafer transfers. This enables the system to "feed 
forward" wafers without the need for a second robot end effector, such as 
is shown in FIG. 4, to store a wafer while an opposing end effector and 
robot arm assembly initiates a transfer. Thus the ability to store two 
wafers within a chamber during wafer transfer can be optimally used in 
association with multiple independent single blade transfer robots, such 
as those shown generally in FIGS. 10 & 11. 
A typical process chamber 260 configured to hold two wafers during transfer 
operations is shown generally in FIG. 14. A wafer W is positioned on a 
pedestal 262 located within the process chamber 260 for processing. A 
shield 263 is located above, and surrounding, the pedestal 262. The 
pedestal 262 can be raised or lowered to desired positions within the 
chamber by a drive mechanism (not shown) such as a stepper motor coupled 
to a lead screw connected to the drive shaft 264. A lift hoop 266 
surrounds the perimeter of the pedestal 262 and can be raised or lowered 
by a lift hoop drive member 268, which may also be a lead screw coupled to 
a stepper motor. A plurality of lift pins 270 extend upwardly from the 
upper surface of the lift hoop 266 to effect wafer placement on the 
pedestal 262. Although, for clarity, the lift hoop is shown as extending 
outwardly from the perimeter of the pedestal 262, in actuality, the hoop 
and pedestal are configured such that the pedestal 262 includes a 
plurality of slots extending inwardly of the perimeter thereof, into each 
of which a lift pin extends. Thus, the engagement of the lift pin to the 
wafer occurs within the envelope of the pedestal, and therefore the wafer 
edge will not overhang the pedestal perimeter. The lift pins according to 
the present invention exhibit a hinge 272 connecting a lower pin segment 
270a to an upper pin segment 270b. The lower pin segment 270a exhibits a 
substantially parallel wafer support surface 274 to the wafer support 
surface 275 of the pedestal 262 for holding a lower of two wafers to be 
held during wafer transfer. When the upper pin segment 270b is in the 
upright position, as shown in FIG. 15A, a wafer support surface 276 is 
oriented in a substantial upper parallel position to surface 274 for 
receiving a second of the two wafers to be held within the chamber. 
In operation, a first wafer is inserted into the chamber 260 by the 
transfer chamber robot in the conventional manner placed above the two pin 
segments 270a, 270b, and picked up by the lift pins 270 on the pin segment 
270b by moving the lift pins 270 upwardly to lift the wafer from the robot 
blade. Then, after the robot blade has been retracted, the pedestal 262 is 
raised to pick the wafer up from the lift pins 270, positioning the wafer 
W on the upper surface of the pedestal 262. Uniquely, the pedestal, 262 
shield 263 and lift pin, 270 cooperate to affect the use of the upper and 
lower pin segments 270a, 270b. To provide this feature, a plurality of 
pedestal pins (or ledges) 278 extend outwardly from the pedestal 262 at 
the location of each lift pin 270, to act as a toggle lever to lift the 
upper pin segment and thereby rotate it into a non-wafer support position. 
To return the upper lift pin segment 270b to its support position, a 
plurality of pins 280 extend inwardly of shield 263 to engage the 
underside of upper lift pin 270b and flip it back into a wafer supporting 
position. After the pedestal 262 lifts the wafer W from the upper pin 
segment the plurality of pedestal pins 278, engage the underside of the 
upper pin segment, to flip the upper lift pin segment 270b to the open 
position shown in FIG. 15B. Preferably, the underside of each of the upper 
pin segments 270b include an extension pin which extends inwardly at the 
pin segment and forms an engagement surface for pin segment 270b pin 278 
contact. The wafer is then processed. After processing, the pedestal 262 
lowers the first wafer. Because the upper pin segment has been flipped 
outwardly, the wafer passes upper pin segment 270b and comes to rest on 
the wafer support surface 274 of the lower pin segment 270a. The lift hoop 
266 carrying the plurality of lift pins 270 is then lowered in 
anticipation of receipt of the next wafer. As the lift pins are lowered, 
the outer surface of the upper pin segment 270b strikes against pin 280, 
extending from shield 263 which causes the upper pin segment 270b to be 
rotated back to the upright or closed position shown in FIG. 15A for 
receipt of an additional wafer thereon. The transfer robot then inserts 
another wafer into the chamber, and the lift pins are raised to position 
the second wafer on the wafer support surface 276 of the upper lift pin 
segment 270b. The transfer robot then removes the first wafer from the 
lower pin segment 270a and the process cycle continues. Thus, the double 
pin segments 270a, 270b enable storage of a processed wafer on the lower 
segment, placement of a new wafer on the upper segment by the robot blade, 
and then removal of the stored wafer with the same blade without the need 
to move the blade in an orbit about the hub, thereby decreasing wafer 
handling time. 
Semiconductor wafers are transferred into the system through the entry 
loadlock 238. A first transfer robot arm assembly 212a picks a wafer from 
the loadlock 238 and moves it into the pre/post processing transfer 
chamber 234 and then into de-gas chamber 242. During the degas process, 
the robot arm assembly 212a picks another wafer from the entry loadlock 
and carries it into the transfer chamber to await de-gas. Once the first 
wafer has been de-gassed, the pedestal 262 within the chamber lowers the 
wafer to the lower horizontal wafer support surface 274. The lift pins are 
then lowered and the upper pin segment is rotated back to the upright 
position. The second wafer may now be inserted into the de-gas chamber and 
placed on the upper wafer support surface 276. Prior to de-gassing the 
second wafer, the robot arm assembly 212a removes the first wafer for 
transfer to the preclean chamber 244. During de-gas of the second wafer 
and preclean of the first wafer, the robot arm assembly 212a picks a third 
wafer from the entry loadlock and carries it into the transfer chamber to 
await de-gas. Once the second wafer has been de-gassed, the pedestal 262 
within the chamber lowers the second wafer to the lower horizontal wafer 
support surface 274. The lift pins are then lowered and the upper pin 
segment is rotated back to the upright position. The third wafer may now 
be inserted into the de-gas chamber and placed on the upper wafer support 
surface 276. The second wafer is now removed from the de-gas chamber for 
transfer to the pre-clean chamber. Once the first wafer has been 
precleaned, the pedestal 262 within the chamber lowers the first wafer to 
the lower horizontal wafer support surface 274. The lift pins 270 are then 
lowered and the upper pin segment 270b is rotated back to the upright 
position. The second wafer may now be inserted into the pre-clean chamber 
and placed on the upper wafer support surface 276. The first wafer is 
removed for transfer to the cooling chamber 248, where it is stored to 
await further processing. The pass through chamber cassette is filled, and 
the wafers are cooled down one at a time. 
In the dual robot assembly of the invention, the upper robot and lower 
robot operate independently from one another. The individual operation of 
each robot is as described in our prior U.S. patent application Ser. No. 
07/873,422, and is expressly incorporated herein by reference. Although 
the invention is described herein with reference to the preferred 
embodiments of the dual robot assembly, it is anticipated that 
modifications will readily suggest themselves to those skilled in the art. 
For example, it is possible to provide a stacked configuration of more 
than two robots without departing from the spirit and scope of the 
invention. Likewise, although the invention has been described herein in 
terms of robots having frog-leg mechanisms, it is equally applicable to 
other robot types, where the operation of at least two of the robots is 
independent of any other in the chamber. 
The present invention, therefore, is well adapted to carry out the objects 
and attain the ends and advantages mentioned as well as others inherent 
therein. While presently preferred embodiments of the invention are given 
for the purpose of disclosure, numerous changes in the details will 
readily suggest themselves to those skilled in the art and which are 
encompassed within the spirit of the invention and the scope of the 
appended claims.