Automatically loadable multifaceted electrode with load lock mechanism

Automatic loading mechanism for automatically transferring semiconductor wafers from storage cassettes onto disk shaped electrodes carried on a hexagonal electrode structure within a plasma reaction chamber. The system includes a reactor chamber, a transport mechanism for transporting semiconductor wafers from storage cassettes and to storage cassettes and a loading mechanism for transferring semiconductor wafers from said transport mechanism onto the electrode structure within the reactor chamber and for transferring processed wafers from said reactor chamber back to said transport means for transport to an output cassette.

This invention relates in general to semiconductor processing and more 
particularly to a gas plasma reaction system for processing semiconductor 
wafers including mechanisms for automatically loading and unloading the 
wafers into a reaction chamber. 
Semiconductor devices are typically manufactured in four inch, generally 
circular wafers, which are processed by both etching and depositing 
materials in dry plasma processes. In these processes wafers are inserted 
into an evacuated chamber, which is then pressurized with appropriate gas 
compositions to carry out the processing in a plasma produced within that 
chamber by the application of a radio frequency field. There are, of 
course, a number of different geometric configurations for this 
processing. Some involve multiple wafer processing and others employ 
chambers which process but a single wafer at a time. In general, high 
throughput is a desirable characteristic of any such system, as is also 
automatic loading and unloading features which permit continuous or 
semicontinuous processing. 
One advantageous chamber configuration is illustrated in U.S. Pat. No. 
4,298,443. In this system, the reaction chamber includes a multifaceted 
central electrode structure, typically a hexagon, in which the central 
electrode is a cylinder of hexagonal cross-section with each side of the 
hexagon being formed of an extended flat face, each face having on it 
several disk shaped planar electrodes on which the semiconductor wafers 
are placed during processing. The system is operated by manually loading 
semiconductor wafers on each of the electrode faces, with the hexagonal 
cylindrical structure vertically oriented and then lowering the outer wall 
of the chamber over this electrode, evacuating the chamber and 
subsequently filling it with gas for the processing itself. The process 
involved is then a batch process and it is not provided with any automatic 
loading and unloading features. 
SUMMARY OF THE INVENTION 
Broadly speaking, the present invention provides a system for automatically 
loading and unloading semiconductor wafers into a plasma reaction chamber 
having a multifaceted central electrode structure, wherein each face of 
the electrode structure carries a number of wafers on planar disk shaped 
electrodes. In general, the system may be considered as having three major 
components: the reaction chamber, which includes the faceted central 
electrode, a transport mechanism for carrying individual wafers from 
storage containers to the reaction system for processing and for carrying 
processed wafers away from the reaction system to either storage or to the 
next stage in processing, and a load/unload mechanism for receiving wafers 
from the transport system and automatically loading them onto the disk 
shaped electrodes in the reaction chamber prior to processing, and for 
removing the wafers from the electrodes after processing and returning 
them to the transport mechanism. 
The reaction chamber must be evacuated prior to being filled with reaction 
gas and, in order to facilitate this process, the load/unload mechanism is 
contained within a vacuum lock chamber connected through a slit valve to 
the reaction chamber. The transport mechanism is operated under ambient 
atmospheric conditions. 
In order to effect the transfer of the wafers from the transport mechanism 
to the loading system and from the loading system to the transport 
mechanism, the loading system is sealed by means of the slit valve from 
the reaction chamber and is allowed to come to ambient atmospheric 
pressure. The wafers are transferred from the transport system through a 
loading port to and from the load mechanism, the loading port is 
thereafter sealed and the housing containing the loading and unloading 
mechanism is evacuated prior to opening the slit valve for the actual 
loading and unloading process into the reaction chamber. The multifaceted, 
typically hexagonal, electrode structure is rotatable about its axis and 
the system may be operated either by loading all of the faces of the 
electrode structure with wafers and thereafter processing for the full 
processing time prior to unloading or, alternatively, one face may be 
loaded, and, in the case of a hexagonal structure, one-sixth of the 
processing time may take place prior to rotation of the structure and 
loading of the next face. 
The plasma reactor chamber has a centrally located electrode structure 
formed of a series of longitudinally extended faces, each of the faces 
being positioned so that in cross-section the electrode structure has a 
regular polygonal shape, the faces being extended in a horizontal 
direction, each of the faces having on its surface a plurality of planar 
disk shaped electrodes for carrying semiconductor wafers to undergo the 
plasma reaction during operation, each of the faces being covered by a 
generally flat tray member having circular openings therein corresponding 
to the positions of the electrode disks, each of the trays being hinged 
for pivotal motion from a first position in close parallel juxtaposition 
with the electrode face to a second position angularly displaced 
therefrom. 
A loading mechanism is disposed generally beneath the reaction chamber, the 
loading mechanism including a plurality of vertically extending support 
arms, each of the support arms being configured to carry a semiconductor 
wafer and formed such that the reactive surface of the semiconductor wafer 
is not touched by any portion of the vertically extending arm, the number 
of vertically extending arms being at least equal to the number of 
electrode disks on a single face of the reactor electrode structure. 
The system includes means for imparting motion to the arms for moving the 
arms from a position beneath the reactor chamber to a position within the 
reactor chamber such that each arm is in close juxtaposition to a 
corresponding one of the disk electrodes, and for thereafter withdrawing 
the arm from the position in close juxtaposition back to a position 
beneath the reactor chamber, and control means for controlling the timing 
of the load mechanism motion such that the arms are moved into and away 
from close juxtaposition to the disk electrodes only when the tray members 
are in the second angularly displaced position. 
The system may further include a plurality of resilient members mounted 
around the periphery of each of the circular openings in the tray 
elements, the resilient members being formed such that when the tray 
element is in its first position the resilient members clamp a 
semiconductor wafer to the disk shaped electrode and when the tray member 
is in its second position the resilient members are not clamping the 
semiconductor wafers to the disk shaped electrodes. 
Preferably, the tray member has a third position in which it is angularly 
displaced from its first position by an amount less than the angular 
displacement of its second position and the electrode faces include at 
least two additional resilient members mounted thereon such that when the 
tray element is in its third position, the additional resilient members 
can retain a semiconductor wafer in position on the disk shaped electrode 
and when the tray element is in its second position, the additional 
resilient elements release the semiconductor wafer from its position on 
the disk shaped electrode. The control means operates the vertical arm 
such that the tray element is moved to its second position and thereafter 
the arms are moved vertically into close juxtaposition with a 
corresponding one of the disk shaped electrodes such that each 
semiconductor wafer carried on each arm is positioned on and generally 
concentric with a corresponding one of said disk shaped electrodes, and 
thereafter the tray element is moved to its third position, such that the 
additional resilient members mounted on the electrode face retain the 
semiconductor wafer carried by the corresponding vertical arm onto the 
disk shaped electrode, the control means operating while the tray element 
is in its third position to cause the reciprocating means to withdraw the 
arms from within the reaction chamber to a position beneath the reaction 
chamber and to cause the tray element to move to its first position after 
the vertical arms have withdrawn to a position below the electrode face. 
Also, the control means operates the vertical arms and the tray elements 
during an unloading cycle in a sequence such that the tray element moves 
from its first position to its third position, thereafter the vertical 
arms are reciprocated into position to accept the semiconductor wafers 
from a corresponding one of the disk shaped electrodes, then the tray 
element is moved to its second position to release the semiconductor 
wafers from the disk shaped electrodes, and then the vertical arms are 
reciprocated to a position beneath and outside of the reaction chamber. 
The load mechanism may comprise a pair of blade elements mounted within the 
housing positioned beneath the reaction chamber, means for imparting 
reciprocating vertical movement to the blades, the vertical arms 
consisting of a first group, equal in number to the number of disk shaped 
electrodes on each face of the electrode structure, and a second group 
equal in number to the first group, the first group being mounted on a 
first one of the blades, and the second group being mounted on a second 
one of the blades, and means for imparting pivotal movement to the blades 
such that in a first pivoted position the first group of vertical arms are 
positioned so that upon reciprocating movement they are carried into close 
juxtaposition with the disk shaped electrodes and in a second pivoted 
position, the second group of vertical arms are positioned such that upon 
reciprocating upward movement they are carried into close juxtaposition 
with the disk shaped electrodes, the control means being operated such 
that one group of vertical arms carries semiconductor wafers from the 
transport mechanism into position on the disk shaped electrode when the 
blades are in one pivoted position and the other group of vertical arms 
carries semiconductor wafers from the disk shaped electrodes when the 
blades are in the second pivoted position. 
The vertical support arms may be each formed of a support strut and a 
spring clip positioned to hold a semiconductor wafer against the support 
strut, the spring clip having a cam tip shaped such that when the arm 
moves into close juxtaposition to the disk electrodes, the cam tip is 
moved behind the disk electrode, moving the spring clip away from the 
semiconductor wafer, and freeing the wafer such that it is retained on the 
support strut only by gravity. 
The load mechanism may include a housing formed with a passage between it 
and the reaction chamber, and means for providing a vacuum tight seal 
between the housing and the reaction chamber when the arms are in position 
beneath and outside of the reaction chamber, the housing having a second 
opening for receiving semiconductor wafers from the transport mechanism 
only when the reaction chamber passage is closed, and means for providing 
a vacuum tight closing for the opening. 
The transport mechanism preferably includes a conveyor system for moving 
the semiconductor wafer from a cassette into individual spaced positions 
adjacent to the second opening, means for opening the vacuum tight 
closing, and wafer carrier means for lifting the wafers from the conveyor, 
through the second opening into a position adjacent to the loading 
mechanism such that the loading mechanism in its upward reciprocating 
motion can transfer the wafers from the carrier to the vertical arms. 
The carriers may be generally rectangular shaped vacuum chucks mounted on 
swing arms, and the system includes means for providing a vacuum to the 
chucks to retain the wafers on the chucks when the carriers are moving the 
wafers from the transport mechanism to the loading mechanism vertical 
arms, and to remove the vacuum when the vertical arms have engaged the 
wafers. 
Alternatively, the support arms are each formed of a support strut and a 
pawl means for holding a semiconductor wafer against the support strut, 
including vertically movable means on which the pawl means is mounted, 
whereby when the arm moves into close juxtaposition to the disk 
electrodes, the pawl means is moved down from the semiconductor wafer, 
freeing said wafer such that it is retained on the support strut only by 
gravity. Furthermore, the vertically movable means preferably includes a 
movable pawl support, resiliently mounted on the vertical support arm, and 
guide means for guiding the movable pawl support, the guide means being 
arranged to guide the movable pawl support so that the pawl means is moved 
transversely away from the semiconductor wafer as well as down from the 
wafer when the arm moves into close juxtaposition to the disk electrodes. 
Also, the pawl means may have an electrode contact surface for contacting 
the disk electrode to cause the pawl means to move down from the 
semiconductor wafer as the arm moves into close juxtaposition to the disk 
electrode. 
Also, the system may include a ring of insulating material defining the 
circular openings in the tray elements, the resilient members being 
mounted in the ring on support elements, and the ring defines bores in 
which the support elements are slidable. 
In an alternative embodiment, the additional resilient members comprise a 
block means and a tab means mounted on the block means, the disk electrode 
face defining a recess for resiliently, closely seating the block means, 
and linking means connecting the block means to the tray element whereby 
the tray element moves the block means from a position in which the tab 
means engages the semiconductor wafer to a position in which the tab means 
does not engage the wafer when the tray element moves from the tray 
element third to the tray element second position. Biasing means urges the 
tab means mounted on the block means toward engagement with the 
semiconductor wafer, the block means defining a bore through which the 
linking means extends to engage the block means, the tray element defining 
a portion closing off the bore when the tray element is in its first 
position.

DESCRIPTION OF PREFERRED EMBODIMENT 
In FIG. 1 there is illustrated in perspective view a semiconductor 
processing system. It includes a transport system generally indicated at 
11, a loading system generally indicated at 13 and a plasma reaction 
chamber generally indicated at 12. The purpose of this system is to 
provide for automatic processing of semiconductor wafers in the plasma 
reaction chamber. The wafers, which are illustrated at 21 in FIG. 1, are 
standardized in the industry and are a four inch circular wafer having one 
surface which is to be treated, either by etching or deposition, which is 
the sensitive surface. Each of the wafers has a primary flat side for 
purposes of orientation. In the semiconductor processing industry there is 
at present a standardized cassette which loads twenty-four of these 
wafers. In the operation of the present system, a cassette is placed in 
dispensing position 19 from which the wafers are fed one at a time onto a 
belt conveyor system formed of two generally parallel strands 23 and 48 
which carry the wafers first to a wafer flat orientation station 52a. Once 
the wafers have been aligned with the flat side in a specific position, 
they are transported further along until a parallel array of four wafers, 
as illustrated in FIG. 1, is positioned above each of four individual 
transport carriers, shown more clearly in FIGS. 2 and 3. The individual 
wafers are now in a position to be transferred to the loading mechanism 13 
by opening the vacuum tight closure 15 covering the loading port 51. 
The plasma reaction chamber is formed of a gas-tight housing 16 enclosing 
within it a hexagonal electrode 18, which carries on each of its faces a 
series of disk shaped electrodes 24. The hexagonal electrode structure is 
rotated by a drive mechanism operated by a control system, both included 
in housing 14. In operation the electrode structure can be rotated to 
bring, in any desired sequence, each of the faces of the hexagon to proper 
alignment positions for a loading action. Details of such a hexagonal 
electrode system are described in U.S. Pat. No. 4,298,443. The reaction 
chamber 12 is coupled through a slit valve 22 to the loading mechanism 13. 
During the loading portion of the cycle, the function of the loading 
mechanism 13 is to transfer the semiconductor wafers 21 from their 
respective carriers elements 30 to transfer elements within the loading 
mechanism. Once the transfer to the transfer elements has been completed, 
the loading port 51 is resealed with door 15, and the housing of the load 
mechanism 13 is evacuated with slit valve 22 closed. Once both the load 
mechanism 13 and the reaction chamber 12 have been evacuated, slit valve 
22 is opened and the loading mechanism is actuated to transfer the 
semiconductor wafers from the loading mechanism into position on the disk 
shaped electrodes 24. In the unload cycle, the reverse of this process is 
carried out and the semiconductors which have undergone the processing are 
transferred back to the carrier elements 30 on the transport mechanism and 
then are released to the belt conveyor which carries them either to output 
cassette 27 or to a buffer station 25, which may for example be used to 
store wafers until a photoresist stripper element 28 is empty. 
THE TRANSPORT SYSTEM 
The transport system 11 is most clearly illustrated in FIGS. 1, 2 and 3. As 
above mentioned, the function of the transport system is to convey the 
semiconductor wafers from the dispenser cassette 19 to bring them into 
position to be transferred directly to the loading mechanism. It is also a 
function of the transport system to accept the transfer of processed 
wafers from the loading mechanism and convey them to either an output 
storage cassette 27 or to a photoresist stripper or other additional 
processing stage, generally indicated in FIG. 1. The storage cassettes are 
standard in the industry and will not be described further here. The basic 
conveyor system is shown as a rubber belt system with a single outer 
strand 23 carried over a series of pulleys 40. Parallel with the outer 
strand 23 are a series of shorter rubber belts 48 forming a segmented 
track with the openings 49a between the segments 48 providing clearance 
for passage of the carrier arms 30 rotating up to the position shown in 
FIG. 3. The belts 23 and 48 are driven by a step motor programmed sequence 
so that the wafers, as they are removed from the dispenser 19, are carried 
under influence of the programmed control (not shown) to each of the 
desired station. After removal from the dispensing cassette 19, the first 
station at which each wafer is stopped is the flat orientation device 52a, 
which is described in detail in an application filed of even date herewith 
and assigned to the assignee of this application. After each wafer is 
aligned with its flat in a specific position, it is moved along the 
conveyor to a position over an appropriate one of the carrier elements 30. 
Thus the first wafer of each group of four conveyed from the dispensing 
cassette 19 is carried by the conveyor up to the position overlying 
carrier element 30(a), while the next in the sequence is carried to a 
position overlying carrier 30(b), the next to a position overlying carrier 
30(c) and the fourth to a position overlying carrier 30(d). 
The carrier elements are formed of generally rectangular pedestals 31 
welded or otherwise attached to tubular right-angled arms 32 which are 
mounted on rotating shaft 36. 
Shaft 36 is rotated by a small DC motor (not shown) under the control of 
the program control to drive the carrier arm 30 from its normal, or rest, 
position as indicated in phantom in FIG. 3 to one of two transfer 
positions, as generally indicated in FIG. 3 where the vacuum chuck 31 is 
positioned to transfer the semiconductor wafers to or from the loading 
mechanism. In its rest position the carrier arms 32 are mechanically 
stopped in the position shown in phantom in FIG. 3, and in the transfer 
position, the arms are mechanically stopped in either of two positions, 
one corresponding to the transfer position when one blade of the loading 
mechanism is reciprocating for effecting the transfer of the wafers, and 
the other corresponding to the transfer positions when the other blade in 
the load mechanism is effecting the transfer. These latter stops can be 
accomplished, for example, by a fixed screw 35 representing the stop for 
the transfer position at the maximum arc from the rest position, while 
adjustable air cyclinder controlled stop 37 is employed for the transfer 
position intermediate the maximum pivot arc and the rest position. 
When each of the wafers 21 are positioned over the respective carrier arms 
in their normal position, a vacuum is drawn through the hollow tubing of 
the right angled tube 32 so that the vacuum chuck 31 has a vacuum being 
drawn through a small central hole. The shaft 33 is then rotated such that 
the vacuum chucks 31 lift the wafers 21 from the conveyor belts. The 
wafers are now held by the vacuum chucks 31, and the motion of the arms 30 
is continued until the vacuum chucks are in one of the two positions 
indicated for transfer of the wafers. 
Prior to rotating motion being imparted to the carrier arms 30, an 
electrically actuated hydraulic or air piston 49 is actuated to open the 
load lock cover 15 to allow for passage through the load lock 51 of the 
carrier arms 30. A latch mechanism for maintaining the port cover 15 in a 
vacuum tight seal when closed is provided by a latch arm 17(a) driven by a 
rotary motor 17 so that, when the cover 15 is to be opened the latch arm 
is rotated out of the way, and after it is closed it is rotated in the 
opposite direction to ensure a vacuum tight seal. 
What has been above described is the operation of the transport system 
during the load cycle. In the unload cycle, when the loading mechanism has 
removed already processed wafers from the electrode assembly 18 and the 
wafers are in position to be transferred to the transport system, the 
program controller opens the cover 15 of the load lock port 51 and causes 
the carrier arms 30 to be rotated into position adjacent to the path of 
travel of the wafer elements in the load mechanism. The exact mechanism 
for effecting the transfer from the load mechanism to the wafer and the 
operation of that mechanism will be described subsequently in the section 
directed to the loading mechanism. When the carrier arms 30 are in 
position to receive the processed wafers, a vacuum is again drawn on the 
vacuum chucks so that the wafers may be transferred to the carrier arms 
and the vacuum chucks 31 will retain the wafers, while the carrier arms 
rotate back toward the normal or rest positions, and, as the wafers are 
brought into contact with the rubber belts of the conveyor system the 
vacuum is removed. The conveyor belts then carry the processed wafers to 
the photoresist strip station 28 or to the buffer cassette 25 if the 
photoresist strip station 28 is occupied or may be carried directly to the 
receiver cassette 27. 
THE LOAD MECHANISM ASSEMBLY 
The function of the loading mechanism is to receive the semiconductor 
wafers 21 from the transport system and load them onto the individual disk 
electrodes 24 in the hexagonal electrode structure 18. Since the plasma 
reaction chamber 12 is operated at very low pressures and requires 
accurate control of the purity of the gases, it is advantageous from an 
efficiency point of view to maintain the atmosphere within the chamber 12 
either at vacuum or at the low gaseous pressure. Accordingly, when the 
loading mechanism 13 is opened through slit valve 22 to move the wafers 
either into or out of the reaction chamber, it is desirable that the 
environment within the loading mechanism be maintained at vacuum. On the 
other hand, when wafers are being transferred from the transport system 
through the loading port 51 to the loading mechanism, the loading 
mechanism must necessarily be exposed to the ambient pressure. 
Accordingly, the loading mechanism assembly is contained within a 
generally vacuum tight housing 13 provided with a loading port 51 
providing access to it from the outside atmosphere, with the loading port 
51 having, as indicated above, a cover 15 which can be opened to permit 
transfer of wafers through the port or closed to form a vacuum tight seal. 
When the loading port 51 is open, then slit valve 22 which provides for a 
vacuum tight seal between the housing 13 and the reaction chamber 12 is 
closed to seal the interior of the reaction chamber 12 from the outside 
atmosphere. After the loading, or unloading, step between the transport 
system and the loading mechanism has been completed, the load port cover 
51 is closed, providing a vacuum tight seal and the interior of the 
loading mechanism housing 13 can then be evacuated prior to opening the 
slit valve 22 and transporting wafers to the reaction chamber 12. 
The details of the loading mechanism assembly are most clearly shown in 
FIGS. 4, 4a, 5, 6 and 7. The mechanism includes a frame 104 pivotally 
mounted at pivot points 81 within the chamber with the frame being given 
pivotal motion back and forth by virtue of cyclinder 109 driving an arm 
111 on an eccentric shaft 112. A physical limit stopping element 113 
provides that the frame has only two positions, one in which it is tilted 
forward toward the transport system and one in which it is tilted away 
from the transport system. The frame 104 has mounted in it for vertical 
reciprocating motion a pair of blade elements 82 and 80. Each blade 
travels on a pair of rails 105 formed on the inner portion of the frame 
104 with wheels 78 on the blades engaging the rails for guiding the 
vertical movement. Each of 80 and 82 can be moved vertically on the frames 
by virtue of individual stainless steel straps 74 and 75 attached to the 
frame and around capstans 70 and 72 on shafts 69 and 69a. Each of the 
shafts are rotated by respective motors 57 and 57a which, when rotated in 
one direction, cause the respective blade to be raised and in the other 
allow the respective blade to drop. 
Each of the blades 80 and 82 carries a series of four vertical support 
arms, or paddles, 52 laterally spaced to correspond to the spacing of the 
disk shaped electrodes 24 on the hexagonal electrode structure 18. The 
paddles include the base element 52, formed of a suitable material such as 
Teflon (TFE). Extending vertically from each of the base members 52 is a 
flat metal spring element 56, capped with a retaining top 58. The paddle 
elements 52 are mounted in cutout slots in the respective blade and 
supported by springs 65, thereby allowing a small amount of resilient 
vertical movement of the paddle with respect to its supporting blade. Both 
the cap 58 and base member 52 of the paddle have recesses such that a 
semiconductor wafer can be supported on the ridge on the base portion 52 
and against the ridge in the cap element 58 (as is particularly shown in 
FIG. 14) so that only the outer rim of the wafer touches the support arm 
when a wafer is positioned on it. This prevents contamination or damage to 
the sensitive surface of the wafers 21. 
In its vertical travel each blade has three vertical positions, a lowermost 
position, an intermediate position in which the support arms are generally 
aligned with the loading port 51, and an upper position in which the 
support paddles 52 are positioned adjacent to the disk shaped electrodes 
24. The position of the blade for each of these positions is determined by 
a series of optical sensors 100, 101, and 102, each of which are formed 
with a light emitting diode and a light sensor positioned such that when 
the tab element 103 attachned to each blade passes through the sensor, a 
signal is generated to the program controller. Thus, depending upon the 
sequence being followed by the program control, the motors 57 and 57a are 
stopped to position the blade at the appropriate vertical stop. 
Each of the support arms in 52 also provided with a pair of spring clips 
61, capped with a cam element 62 with the spring clips being mounted 
directly to the respective blade through a block 63. A pin 66 mounted in 
the block extends through a slot opening 67 in the paddle base 52 and 
provides a limitation on the travel of the paddle 52 with respect to the 
slot in the blade. The spring clips 61 serve to hold the semiconductor 
wafers 21 in position on the support arms 52 while the arms are in transit 
between the transport system and the electrode structure. 
By including the pair of blades 80 and 82 in a tilting mechanism, the 
sequence can be arranged such that after the slit valve 22 is opened, and 
while the housing 13 of the load mechanism assembly remains pumped down to 
a vacuum, wafers may be loaded or unloaded from one face of the hexagonal 
electrode structure 18 and then with rotation of the electrode structure, 
the second blade may load or unload wafers from a second face of the 
electrode. 
THE ELECTRODE STRUCTURE 
The details of construction of the electrode structure 18 are illustrated 
in FIGS. 8 through 13. The electrode structure is formed of a frame 18 
which is hexagonal in cross section, and includes on each face of the 
hexagon a series of disk shaped electrodes 24, formed of a highly 
conductive metal such as aluminum. Each face is covered by a rectangular 
tray element 29, which may be formed of metal and coated with an 
insulating surface. Tray element 29 is connected to the main structure 18 
through a hinge element 19a, which allows the tray element 29 to swing 
from its position in close parallel contact with the face of the electrode 
structure to two positions angularly displaced from it. This motion is 
provided by a crank 150, driven by a rack and pinion arrangement, which is 
mounted outside of and therefore does not rotate with the hexagonal frame 
18. The crank 150 engages a tab 128 on the edge of each of the tray 
elements 29 when the respective face is in alignment with the crank arm 
150. A series of springs 132a are mounted to bias the tray element 29 
toward a closed position in contact with the electrode structure 18 and 
the force of the crank arm overcomes this spring resistance in moving the 
tray element to the angularly displaced positions. Each of the tray 
elements 29 has a series of circular openings therein corresponding to the 
position of the disk shaped electrode and each opening has affixed to it a 
series of four resilient members 120, which may be formed of a suitable 
material such as a thermoplastic polyarylate manufactured by Union Carbide 
Corp. under the trade name of "Ardel". As is illustrated most clearly in 
FIG. 11, tab elements 120 are fastened to the tray element with spring 
elements to provide them sufficient resilience to retain wafer disk 21 in 
position over electrode face 24 when the tray 29 is in the closed 
position. 
An additional pair of resilient tab elements 122 is fastened to each of the 
faces of the hexagon by leaf springs 132. When the tray element 29 is in 
the partially opened position, these elements 122 retain a wafer 21 in 
position on the face of the disk electrode 24. On the other hand, when the 
tray element 29 is pivoted to its outermost position, the arm 130 attached 
to it pushes the resilient tabs 122 forcing them outwardly away from the 
face of the disk electrode 24, thereby releasing any semiconductor wafer 
21 which was being retained by these tabs. 
In FIG. 16 there is illustrated in detail the mechanism for effecting the 
pivotal motion of the tray elements 29. A crank arm 150 is pivoted at 
pivot 154 and, as the rack 157 is driven forward by pinion 158, the pivot 
point is brought forward and the roller 151 forces the crank to rotate to 
the position shown in phantom in FIG. 16. When the roller 159 on the end 
of the crank 150 engages the tab 128 it drives the lower edge of the tray 
element 29 outward. The program controller controls the drive of the 
pinion 158 such that the rack is driven to a first displaced position with 
the tray element 29 pivoted out from the face of the electrode structure 
18 sufficiently far to allow the paddle support arm 52 to be inserted 
between the face and the tray element 29 and it can be driven to a still 
further out pivoted position where the arm 130 will engage the resilient 
tab elements 122. 
The entire hexagonal electrode structure is carried on a pivot bearing and 
can be rotated by a rotational drive 130a so as to position any selected 
face of the hexagonso that its disk electrodes lie in vertical alignment 
above the slit valve 22. 
THE SLIT VALVE 
The slit valve 22 is most clearly illustrated in FIGS. 3, 14 and 15. The 
sealing elements of the valve include an upper block 143 and a linked 
lower block 142. The lower block 142 has a series of roller bearings 144 
permitting it to travel freely along the lower plate 140 of the slit valve 
assembly and, at the same time, providing rolling contact against the 
sealing plate 143 when in motion. The lower element 142 is carried on the 
end of the drive rod 146, which extends from an air cyclinder 150a which 
is once again operated under the control of the program controller. Thus, 
on the forward stroke of the cyclinder the roller element 142 is driven 
across the opening 148 in the slit valve of the reaction chamber until it 
pivots up the sealing plate 143. The configuration of the lower block 142 
of the valve element applies vertical upward pressure against the block 
143 causing the gasket 145 carried in that block to effectively seal the 
opening 148. On the withdrawal stroke, block 143 is lowered somewhat 
vertically and pivoted down from the opening 148 thereby opening the 
passage and permitting the support arms 52 to move therethrough. 
OPERATION OF THE LOAD MECHANISM 
At the commencement of the loading cycle, when the cover 15 for the loading 
port 51 is opened, both of the blades 80 and 82 are in their lowermost 
position when the slit valve 22 is closed. The carrier arms 30 then are 
rotated through the loading port 51, with the semiconductor wafers 21 
being retained on them by the vacuum action of the vacuum chucks 31 with 
the flat on the wafere oriented horizontally on the lower side. As 
described previously, depending upon the pivoted position of the frame 
104, either blade 80 or 82 is then raised such that the recessed edge of 
the paddle block 52 engages the flat on the semiconductor wafer 21 while 
the cam tips 62 ride behind the vacuum chucks 31. The intermediate 
stopping position of the blade elements is such that the wafer is now 
supported on the paddle with the upper peripheral edge of the wafer 
resting on the ridge of the support arm cap 58. Upon release of the 
vacuum, the blade is now withdrawn downwardly to its lowermost position, 
allowing the cam tips 62 to slip from behind the vacuum chucks 31 and 
engage the back (non-sensitive) surface of each of the semiconductor 
wafers. At this point the carriers 30 are withdrawn through the loading 
port 51 and returned to their original or rest position. The cylinder 49 
is then actuated to close the cover 15 of the loading port 51 into a 
sealed position. A vacuum is then drawn on the loading mechanism assembly 
housing 13 and, when sufficient time has elapsed for this vacuum to be 
achieved, the slit valve 22 is opened. The tray element 29 which is in a 
vertical plane generally aligned with the blade element carrying the 
semiconductor wafers 21 is now pivoted outwardly to its outermost position 
and the blade element carrying the semiconductor wafers 21 is driven 
upwardly to its topmost position in which the semiconductor wafers 21 
carried on the support arms 52 are positioned immediately adjacent to and 
generally concentric with corresponding ones of said disk shaped 
electrodes. The cam tips 62 on each of the support arms 52 ride behind the 
electrode faces during this upward movement so that the semiconductors 
wafers 21 are retained in position only by virtue of their resting on the 
support arm in close juxtaposition to the disk shaped electrodes 24. 
Once this upward position of the blade has been achieved, the tray member 
29 is pivoted back to the intermediate position, allowing the resilient 
tabs 122 to engage the outer rim of the wafers 21 clamping them to the 
respective disk shaped electrodes 24. At this point the blade carrying the 
support arm elements is reciprocated downwardly to its lowermost position 
and, once the support arms have cleared the lower edge of the tray 
elements 29, the tray element is returned to its closed position in which 
the additional resilient elements 120 now aid in clamping the 
semiconductor wafers 21 to the disk shaped electrodes 24. The slit valve 
22 is closed and sealed and the reaction chamber 16 may be filled with gas 
and the process carried out in the usual manner. 
In order to provide for more efficient operation both blades may be used 
during a single portion of the cycle when the housing 13 of the load 
mechanism assembly is evacuated. In one such arrangement, two of the faces 
of the hexagon may be loaded with wafers for each such evacuation. The 
sequence in this operation proceed with the initial transfer of the wafers 
from the carriers to the support arms in the same fashion as described 
above. However, once the wafers are mounted on the support arms 52, and 
the carrier elements 30 are withdrawn to their normal or rest position, 
the cover 15 of the loading port 51 is not closed. An additional set of 
four wafers is transported onto each of the carrier arms 30 and, at the 
same time, the blade element which now carries the semiconductor wafers 21 
is withdrawn to its lowermost position and the frame 104 is pivoted to 
bring the other blade element to position for receiving a transfer of 
wafer elements. The carriers 30, carrying a second set of semiconductor 
wafers 21, rotate upwardly into poisiton to align with the support arms 
carried on the second blade when it is raised and the second blade is 
raised to receive the second set of semiconductor wafers 21 in the same 
fashion as the first blade received the first set of four. The second 
blade is now withdrawn to its lowermost position and the cover 15 of the 
loading port 51 is closed and sealed. 
The loading mechanism housing 13 is now evacuated with both blades carrying 
a set of four semiconductor wafers within it and the slit valve 22 is 
opened after this vacuum has been achieved. 
The blade carrying the second set of wafers 21 which have just been 
transferred from the transport system is now raised vertically to its 
uppermost position, with the tray element 29 being pivoted outwardly to 
allow transfer of this set of wafers to the corresponding disk shaped 
electrodes in the same fashion as was described previously. After the 
transfer has been accomplished and this blade is withdrawn into the 
housing 13, the slit valve is not closed, but rather the hexagonal 
electrode structure 18 is rotated to align a new face of the hexagon with 
the slit valve. Frame 104 carrying the blades 80 and 82 is now pivoted to 
bring the other blade whose support arms are carrying the other set of 
semiconductor wafers 21 into alignment with the slit valve and upon 
raising this blade vertically, the second set of wafers can be transferred 
to the second face of the hexagon in the same fashion as was the first 
set. Upon completion of this transfer this second blade is withdrawn into 
the load mechanism housing 13, and the slit valve is closed. The hexagonal 
reactor chamber can be operated either such that the process is carried 
out only after all of the electrode faces have been loaded for the full 
time required for the plasma processing, or if only one face is loaded for 
each cycle, one-sixth of the process can be carried out and the 
load/unload mechanism can be actuated. Still another alternative with the 
system described herein would be to load two faces of the electrode 
structure at a time and process for one-third of the total process time 
before again actuating the load mechanism. Since the general purpose is to 
provide for a continuous or semicontinuous processing, it is preferred to 
have the semiconductor wafers which have completed their processing be 
withdrawn in the unloading cycle while a new set of unprocessed wafers is 
transferred onto that face without requiring an additional evacuation 
cycle of the load mechanism housing. One way of accomplishing this is to 
provide that one of the blades withdraws the already processed 
semiconductor wafers from a hexagonal face and the other blade carries new 
unprocessed wafers and transfers them onto the same face. 
While there has been no specific description of the program control for 
operating the device in any of the various sequences described, it will be 
understood that there are a number of suitable program controllers. If a 
fixed sequence is desired, the program controller can consist of a series 
of cam operated electrical switches to actuate the various pistons and 
motors in appropriate sequence as described above. More flexible programs 
can be carried out by using a computer with appropriate software to 
provide electrical signals to actuate the appropriate electric motors and 
pistons. Of course, the hydraulic or pneumatic pistons can be controlled 
by electrically operated valves responding to these electrical signals. 
As indicated, the preferred form of controller is a programmed digital 
computer system. In the present exemplary embodiment, the digital computer 
system includes a BAL11ME backplane and power supply, a PDP11/23 digital 
computer board, a MSV11L memory board, three DLV11J parallel input/output 
boards and a DLV11J serial line interface for a CRT terminal, all 
manufactured by Digital Equipment Corporation, Maynard, Mass., and a 
Visual100 CRT terminal, manufactured by Visual Technology, Inc., 
Tewksbury, Mass. The program, implemented in Pascal, for the exemplary 
digital computer system is shown in Appendix A. In other embodiments, 
different computer configurations may be used, as well as different 
programs, to control the functional operation of the system as described 
above. 
FIGS. 17-27 show features of a second embodiment of the system. In the 
second embodiment, elements of the loading mechanism 13 and the hexagonal 
electrode assembly 18 have been modified to eliminate or minimize cavities 
or recesses in the reaction chamber 12. Such cavities and recesses may 
under some circumstances accumulate gas plasma and lead to arcing during 
high energy operation of the chamber. 
FIG. 17 is a view like that of FIG. 8, showing the electrode assembly 18. 
The same reference numerals will be used in the description and drawings 
of the second embodiment as in the first for elements that are common to 
both embodiments. Thus, FIG. 17 shows an electrode structure formed of a 
rotatable frame 18 that is hexagonal, and that has a series of disk shaped 
electrodes 24 on each face of the hexagon and a rectangular tray 29 
hingedly connected to each face of the hexagon. The tray 29 is swingable 
between a first position in close parallel contact with each hexagon face 
and two other positions each angularly displaced from the first poisiton 
(and angularly displaced from each other). 
As explained in the description of the first embodiment, the movement of 
the tray 29 between these positions occurs in conjunction with movement of 
the paddles 52 mounted on vertically movable blades 80,82 of the load 
mechanism to capture wafers from or release them to the paddles 52. 
FIGS. 18 and 19 show a paddle 52 of the second embodiment, mounted on one 
of the vertically reciprocating blades 80. The paddle 52 includes a lower 
main section 160 with a curved stepped groove 162 for receiving and 
supporting the bottom of a wafer 21, and an upper retaining top 164 
against which the top of a wafer 21 may rest. The retaining top 164 is 
connected to the lower main section 160 by a flat metal spring element 
166. The lower main section 160 is fastened to a connecting block 168 
which in turn is screwed onto the blade 80. 
The paddle 52 of this second embodiment shown in FIGS. 18 and 19 includes a 
vertically retractable pawl 170. The pawl 170, made out of a polymer sold 
by Union Carbide Corp. under the trademark "Delrin," has a curved front 
surface 172 for contacting the wafer 21 and holding it in place while the 
paddle 52 transfers it to and from the gas reaction chamber 12 (see FIGS. 
19 and 20). 
The pawl 170 is fixed atop a stainless steel rod 174 whose lower portion is 
slidable through a hole in a bracket 176 fixed to the blade 80. 
Intermediate the pawl 170 and the bracket 176 are a pair of cam guides 
178, made also from Delrin material, and positioned on either side of the 
rod 174. The cam guides 178 define cam slots 180 into which extends a 
transverse axle 182 on the rod 174. A coil spring 184 surrounds the rod 
174 and extends between the axle 182 and the pawl bracket 176. The cam 
slots 180 in the cam guides 178 are arranged so that as the pawl 170 is 
forced downward against the bias of spring 184, the axle 182 travelling in 
the cam slots 180 causes the pawl 170 to move transversely away from, as 
well as downward from, its position against a wafer 21. The pawl 170 is 
forced downward when its upper surface 186 meets an object during upward 
travel of the blade 80. Such an event occurs when the paddle 52 rises on 
the blade 80 (or blade 82) to meet a wafer 21 on a vacuum chuck 31, when 
the pawl upper surface 186 meets the bottom of the vacuum chuck 31 (see 
FIGS. 2 and 3). It also occurs during transfer of the wafer 21 from the 
paddle 52 to the electrodes 24 within the plasma reaction chamber 12. 
The transfer of a wafer 21 from the paddle 52 to the electrodes 24 is 
illustrated in FIGS. 19 and 20. FIG. 19 shows a wafer 21, carried through 
the slit valve 22 by the paddle 52, in the direction of the arrow, 
beginning to engage an electrode 24. The pawl 170, which has been seating 
the wafer 21 against the paddle top 164 and paddle groove 162, meets the 
bottom of the electrode 24. As the blade 80 continues to proceed upward in 
the direction of the arrow the pawl 170 moves transversely away from, and 
downwardly from, contact with the wafer 21 (see FIG. 20). 
With the pawl 170 of this second embodiment moving downward from the wafer 
21, there is no need for a recess behind the face of the electrode 24, as 
there is in the first embodiment (see FIGS. 14 and 15), where such a 
recess is necessary to accommodate the paddle clips 62 of the paddle 52 of 
the first embodiment. 
As shown in FIG. 20, the pivotable tray 29 of the electrode assembly 18 is 
still in its outermost position, which it takes while a wafer 21 is 
brought to the electrode assembly 18. As in the first embodiment, the next 
step is for the tray 29 to move to an intermediate position, where a pair 
of intermediate holding tabs 190 engage the wafer 21 and press it against 
the face of an electrode 24 while the paddle 52 is retracted. Then the 
tray 29 moves, in accordance with the programmed movements of the system, 
to a fully closed position, where four additional tabs, full engagement 
tabs 192, press the wafer 21 against the electrode face. 
In the second embodiment of the invention, as shown in FIGS. 17 and 21, the 
four full engagement tabs 192 are seated in a ring 194 of "Ardel" 
material, rather than directly in the tray 29. Each ring 194 is seated in 
a groove surrounding each opening of the tray 29, so that the general 
relationship of the full engagement tabs 192 to the remainder of the 
electrode assembly 18 is the same as in the first embodiment. 
As shown in FIG. 22, the tabs 192 are fixed to the ends of shoulder screws 
196 made from "Ardel" material that are spring loaded in recesses 198 
formed in the ring 194. The recesses 198 are small and open to a side of 
the ring 194 that is pressed against the electrode assembly structure 
during operation of the gas reaction chamber. The shoulder screws 196 
extend through holes 200 in the bottom of the recesses 198 to thread into 
the tabs 192. 
As shown in FIGS. 21-24, the second embodiment has a different arrangement 
and configuration of the structure supporting the intermediate holding 
tabs 190. FIG. 21 shows the tabs 190 in a mounting 202 embedded in the 
electrode assembly 18. FIG. 22 shows the intermediate holding tab 190 
arrangement from a view looking up, and showing the tabs 190. FIG. 23 is a 
similar view, with the tray 29 lifted to its intermediate position. FIG. 
24 is another view of the tab arrangement, but from a direction 90.degree. 
changed from FIGS. 22 and 23, and also with the tray 29 lifted to its 
fully open position. FIG. 24 shows more clearly the spring loading 
arrangement of the intermediate tab assembly. 
As seen in FIGS. 21-24, the intermediate holding tabs 190 comprise lateral 
extensions from a tab block 204 seated in the mounting 202. The tab block 
204 is resiliently seated in the mounting 202 by way of spring loaded 
screws 206, so that the tabs 190 are biased toward the electrode assembly 
18. The tab block 204 defines an axial bore 208 with a narrow upper 
portion 210 and a lower bottom portion 212. 
A linkage rod 214, with a ball 216,218 fixed at each end, connects the 
hexagon electrode assembly tray 29 to the intermediate tab block 204. The 
ball 216 at one end of the rod 214 is seated in the tray 29. The ball 218 
at the other end is movable in the block bore bottom portion 212, the rod 
214 extending through the bore upper portion 210. 
When the tray 29 is in its fully closed position the ball 218 at the end of 
rod 214 is located at the very bottom of bore portion 212 (see FIG. 22). 
When the tray 29 moves to its intermediate open position (see FIG. 23) the 
ball 218 travels up the bore portion 212 to a ball seat 220, as the 
linkage rod 214 travels up the bore 208. In this situation, the 
intermediate holding tabs 190 still are resiliently holding the wafer 21 
to the face of an electrode 24. When the tray 29 moves to its outermost 
open position (see FIG. 24) the ball 218 engages the ball seat 220 of the 
block 204 and pulls the block 204 including the tabs 190 up and out of the 
mounting 202, disengaging the tabs 190 from the wafer 21. 
In a wafer loading operation, the steps would be reversed. That is, the 
tray 29 would be fully open while a wafer 21 is brought to the face of the 
electrode 24, and neither the full engagement tabs 192, nor the 
intermediate engagement tabs 190 engage the wafer 21. When the tray 29 
moves to its intermediate position (FIG. 23), the intermediate tabs 190 
engage the wafer 21. Then the paddle 52 which brought the wafer 21 up is 
retracted, and the tray 29 move to its fully closed position. Then the 
full engagement tabs 192 also engage the wafer 21, the intermediate tabs 
190 continuing to engage the wafer 21 as well. 
FIG. 25 shows a spring loaded ball plunger 222 screwed into a threaded hole 
224 in the face of an electrode 24 approximately beneath the positions of 
the intermediate holding tabs 192. The ball 226 of the plunger 222 is 
resiliently urged against a wafer 21 placed on the electrode face to 
positively urge the wafer 21 off the electrode face when the intermediate 
holding tabs 192 are disengaged. The balls 226 also enhance the gripping 
of the wafers 21 when the intermediate holding tabs 192 are engaged with 
the wafer 21 because the balls 226 push the wafers 21 from the opposite 
side. 
FIG. 27 shows in detail the mechanism of the second embodiment for 
effecting the pivotal motion of the trays 29. As in the first embodiment, 
the mechanism includes a gear rack 157 and pinion 158. The gear rack 157 
has a forward push rod portion 228 on which is mounted at the very end 229 
a small wheel 230. The mechanism is housed in a dark space shield 232 that 
has a forward wall portion 234. The push rod 228 is drivable by the pinion 
158 (under the control of the program controller) through a close fitting 
hole 236 in the forward wall portion 234. 
When the tray 29 is closed, the push rod 228 is retracted such that the end 
229 of the push rod 228 is flush with the outside surface 238, thereby 
providing an essentially cavity-free surface. 
To open the tray 29, the push rod 228 is driven out of the dark space 
shield 232 to contact and push a tray tab 240 mounted on the outside of 
the tray 29, and extending approximately one inch beyond the end of the 
electrode assembly 18. The tab 240 thus extends directly over the location 
where the push rod 228 exits the dark space shield 232 so that no 
clearance slots need to be machined into the end of the electrode assembly 
18 as in the first embodiment. 
As the push rod 228 contacts and pushes the tray tab 240 (with the wheel 
230 at the end of the push rod 228) it causes the tray 29 to swing outward 
toward the tray's intermediate and final open positions. To close the tray 
29, the push rod 228 is retracted into the dark space shield 232, and the 
tray 29 returns to its closed position. 
The use of "Ardel" material for the elements of the system, as a coating, 
or as the material for a complete element, such as the ring 194, is to 
minimize arcing when the reaction process is carried out. For oxide 
etching, "Ardel" is generally used to coat the electrodes and any other 
exposed parts that will be at RF potential during the process. In aluminum 
etching, "Ardel" may be used only for items such as the tabs. Where an 
insulating coating is needed, aluminum oxide may be used. The ring 194, 
fully composed of "Ardel" in the embodiment shown, may, if the operation 
of the system proceeds successfully with the substitution, be replaced by 
a metal ring, with an "Ardel" coating or an "Ardel" gasket. 
Having described the invention various other modifications and improvements 
may occur to those skilled in the art and the invention is defined by the 
following claims.