Apparatus for conveying a semiconductor wafer

A transfer apparatus for conveying a semiconductor wafer between a first location and a second location comprises transfer arm means including first and second elongated arm members each having first and second ends. The first end of the first arm member is pivotally supported at a point generally midway between the two locations and the first end of the second arm member is pivotally supported by the first arm member proximate to the second end thereof. The first and second arm members are of sufficient length and are cooperative to pivot to at least a first position in which at least a part of the second arm extends to the first location, a second position in which at least a part of the second arm member extends to the second location and an intermediate position. Arm member actuator means are provided for pivoting the first and second arm members to the first, second and intermediate positions.

BACKGROUND OF THE INVENTION 
The present invention relates to a transfer apparatus for conveying a 
semiconductor wafer between two locations and, more particularly, to such 
a transfer apparatus which can conveniently transfer such a semiconductor 
wafer between two locations having differing pressures without 
substantially affecting or disturbing the pressure at either of the two 
locations. 
The etching of semiconductor wafer materials utilizing a gas plasma 
reaction in an evacuated or vacuum chamber is generally well-known in the 
art. The apparatus for the treatment of semiconductor wafers by such a gas 
plasma reaction can be classified into two major types; (1) batch, in 
which a plurality of sheets of wafers are placed inside of a reaction or 
treatment chamber for simultaneous treatment; and (2) continuous, in which 
the semiconductor wafers are continuously serially introduced into the 
reaction or treatment chamber one at a time and are individually removed 
from the treatment chamber after the gas plasma treatment. 
Numerous prior art devices and methods have been employed for transferring 
the semiconductor wafers into or out of a reaction chamber for continuous 
treatment without disturbing or otherwise affecting the vacuum or pressure 
level within the reaction chamber. Most of the prior art devices employ a 
separate feeding or inlet chamber (air lock) adjacent the reaction or 
treatment chamber. A mechanical device is employed for transferring the 
wafers into the feeding or inlet chamber one at a time and, once the 
pressure within the feeding or inlet chamber has been adjusted to 
correspond to the pressure within the reaction chamber for transferring 
the wafers into the reaction chamber. In some of the prior art transfer 
devices, one or more conveyor belts are employed for the actual movement 
of the semiconductor wafer into and out of the feeding chamber. Other such 
devices employ piston actuated pusher members for moving the semiconductor 
wafers. Yet other prior art devices employ a complicated walking beam 
arrangement for moving the semi-conductor wafers. 
While the prior art devices for moving a semi-conductor wafer into or out 
of a reaction chamber generally function satisfactorily, they are usually 
mechanically complex and, therefore, are expensive to purchase and operate 
and may require frequent service. In addition, because of the way in which 
the prior art devices operate, it is difficult if not impossible to 
ascertain the exact location of a particular wafer being transferred at 
any given time during the transfer cycle. As a result, sometimes wafers 
are damaged or destroyed by the opening or closing of a reaction chamber 
or feeding chamber door when a wafer is in the wrong position. This causes 
not only a loss of the wafer, but also possible contamination of the 
apparatus which must then be cleaned before any wafer processing can be 
resumed. 
In addition to the previously described drawbacks, the prior art transfer 
devices do not lend themselves to the conducting of any pre-treatment or 
post-treatment processing of a wafer within the entry or exit chamber 
while it is being transferred. Pre-treatment processing such as hardening 
the photo resist material or desmearing the wafer to remove any 
accumulated oxide can be helpful in speeding up the etching process which 
occurs within the plasma treatment chamber and/or providing a better 
quality product. Post-treatment processes such as stripping the photo 
resist material off of the wafer can also be useful in speeding up the 
wafer production process. 
The present invention provides a compact, mechanically simple wafer 
transfer apparatus which is inexpensive to produce and operate and yet 
provides a reliable, positive wafer transfer motion which permits the 
location of the wafer to be determined during the transfer process. The 
present invention also permits pre-treatment and post-treatment processing 
of the semiconductor wafer in conjunction with the wafer transfer process. 
SUMMARY OF THE INVENTION 
Briefly stated, the present invention comprises transfer apparatus for 
conveying a semiconductor wafer between a first location at a first 
pressure and a second location at a second pressure without substantially 
affecting the pressure at either location comprising: 
a substantially airtight transfer chamber disposed between the first and 
second locations, the transfer chamber including a first closeable port 
for providing communication between the first location and the transfer 
chamber, a second closeable port for providing communication between the 
second location and the transfer chamber and port actuator means for 
opening and closing the first and second ports; 
transfer means for transferring the wafer between locations including first 
and second elongated arm members each having first and second ends, the 
first end of the first arm member being pivotally supported within the 
transfer chamber and the first end of the second arm member being 
pivotally supported by the first arm member proximate to the second end of 
the first arm member, the second end of the second arm member being 
adapted to receive and support a semiconductor wafer, the first and second 
arm members being of sufficient length and being cooperative to pivot to 
at least three positions, the three positions including 
a first position in which at least a portion of the second end of the 
second arm member extends through the first port, 
a second position in which at least a portion of the second end of the 
second arm member extends through the second port, and 
an intermediate position in which both arm members are located within the 
transfer chamber, 
whereby a semiconductor wafer may be placed upon the second end of the 
second arm member when the arm members are in one of the first or second 
positions and may be removed when the arm members are in the other of the 
first and second positions; 
arm member actuator means for pivoting the first and second arm members to 
the first, second and intermediate positions; 
pressure adjusting means for adjusting the pressure within the transfer 
chamber to either the first or the second pressure; and 
control means for controlling the port actuator means, the arm member 
actuator means and the pressure adjusting means, 
whereby the pressure within the transfer chamber is adjusted only when both 
ports are closed with the arm members in the intermediate position, 
whereby the first port is opened to permit the arm members to pivot to the 
first position only when the pressure within the transfer chamber has been 
adjusted to the first pressure, and, 
whereby the second port is opened to permit the arm members to pivot to the 
second position only when the pressure within the transfer chamber has 
been adjusted to the second pressure.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring in detail to the drawings, wherein like numerals indicate like 
elements throughout the several figures, there is shown in FIG. 1 a 
partially broken away plan view of an apparatus 10 for the continuous or 
in-line treatment of semiconductor wafers by plasma reaction. The 
apparatus 10 comprises a main treatment or reaction chamber 12 within 
which the semiconductor wafers are exposed to the plasma for etching and 
associated transfer apparatus shown generally as 14, for conveying or 
transporting the semiconductor wafers to or from the reaction chamber 12. 
The reaction chamber 12 of the presently preferred embodiment is typical of 
plasma reaction chambers presently employed and well known in the art. A 
detailed description of the structure and operation of the reaction 
chamber 12 is not believed to be necessary to enable one of ordinary skill 
in the art to completly understand the present invention and, therefore, 
will not be presented herein. Such chambers are well known and are 
commercially available from several manufacturers, including Plasma-Therm, 
Inc., the assignee of the present invention. For purposes of describing 
the present invention, suffice it to say that the reaction chamber 12 
comprises a generally hollow, sealed chamber having four side walls 16, 
18, 20 and 22. The reaction chamber 12 is maintained at a controlled 
pressure, typically less than atmospheric pressure (i.e. vacuum) by 
suitable known vacuum pumping means which are not shown in the drawings. A 
flow of plasma gas from a source (not shown) is introduced into the 
reaction chamber 12 by suitable conduit means (also not shown) for the 
treatment or etching of semiconductor wafers. Within the reaction chamber 
12 is a generally circular, flat platen 24 which serves to support a 
semiconductor wafer during the gas plasma treatment and may also serve as 
an electrode or a ground plane as required. 
As discussed above, one of the problems encountered in the continuous or 
in-line production of semiconductor wafers utilizing such a reaction 
chamber under a vacuum pressure is that it is difficult to transfer or 
convey the semiconductor wafers into and out of the reaction chamber 
without disturbing or otherwise detrimentally affecting the pressure or 
vacuum within the chamber. It is important to maintain the vacuum within 
the chamber within a specific predetermined range in order to avoid costly 
delays in the semiconductor wafer production process and to avoid 
undesirable variations in the quality of the semiconductor wafer products 
which are produced. It is therefore necessary to provide a transfer 
apparatus, such as the transfer apparatus 14 of the present invention 
which may be employed for conveying the semiconductor wafers into and out 
of the reaction chamber 12 without significantly affecting or disturbing 
the vacuum pressure within the chamber. 
For the purpose of maintaining clarity and simplicity in showing and 
describing the present invention, only a single transfer apparatus 14 will 
be shown and described. The single transfer apparatus 14 may be employed 
for transferring the semiconductor wafers both into and out of the 
reaction chamber 12. Alternatively, in the presently preferred embodiment 
as shown in the drawings, the transfer apparatus 14 is employed only for 
the purpose of transferring the semiconductor wafers into the reaction 
chamber 12 and a second transfer apparatus 14a (only a portion of which is 
shown in FIGS. 1 and 2) is employed for removing the semiconductor wafers 
from the reaction chamber once the plasma reaction process has been 
completed. The structure of the second transfer apparatus 14a is 
substantially the same as (actually a mirror image of) transfer apparatus 
14 and the operation thereof will be apparent to one skilled in the art 
from the operation of transfer apparatus 14 which will hereinafter be 
described. 
Transfer apparatus 14 comprises a substantially airtight transfer chamber, 
in the present embodiment a wafer inlet chamber 26, adjoining or disposed 
adjacent to the reaction chamber 12 as shown. For purposes which will 
hereinafter become apparent, the transfer chamber 26 shares a common 
sidewall 16 with the reaction chamber 12 and includes three additional 
sidewalls 28, 30 and 32, as well as top and bottom walls 34 and 36, 
respectively. The six walls of the transfer chamber are connected together 
in any known manner capable of providing sealed joints between the walls 
to provide a substantially airtight chamber. In the presently preferred 
embodiment, the transfer chamber 26 is generally square in plan as shown, 
it being understood that the invention is not limited to a chamber having 
any particular shape. Means (not illustrated) well known to those skilled 
in the art, are provided for adjusting the pressure within the transfer 
chamber 26. The pressure adjusting means communicate with the chamber via 
conduits 27. 
The transfer chamber 26 includes a pair of closeable, sealable transfer 
ports or slot valves 38 and 40 disposed on opposite lateral sides thereof 
as shown in FIGS. 1 and 2. The first transfer port 38 serves as an inlet 
port and extends through transfer chamber sidewall 28 to provide 
communication between the transfer chamber 26 and a location outside of 
the transfer chamber 26. 
In the presently preferred embodiment as shown in FIG. 1, the outside 
location comprises a wafer storage area 42 where semiconductor wafers 
which have been previously prepared for etching (i.e. masked, coated with 
photo resistant material, etc.) are temporarily stored prior to being 
introduced into the reaction chamber 12. Typically, such prepared 
semiconductor wafers are stored in a wafer storage device such as a wafer 
cassette apparatus 43 which includes means (not shown in detail) for 
storing a plurality of semiconductor wafers in a vertical stacked relation 
and an elevator means (not shown) for moving the stack of wafers up or 
down to permit the removal of the semiconductor wafers one at a time from 
the top or the bottom of the stack. Conveyor means, such as conveyor belts 
44 or the like may be employed for moving the wafers from the storage 
cassette 43 to the wafer transfer apparatus 14. A wafer stop device 45 may 
be employed to stop the lateral movement of the wafers along the conveyor 
belts 44 at the correct position for depositing the wafers onto the wafer 
transfer apparatus 14. After a wafer is deposited onto the wafer transfer 
apparatus 14 part or all of the conveyor belts 44 may be pivoted or 
otherwise moved (not shown) to a position in which they do not interfere 
with the further movement of the wafer. A more detailed description of the 
structure and operation of the semiconductor wafer storage device 43 and 
the conveyor belts 44 is not believed to be necessary for a complete 
understanding of the present invention and therefore will not be presented 
herein. Wafer storage and conveyor devices are well known and are 
commercially available from manufacturers such as Siltec of Menlo Park, 
Calif. 
In the present embodiment as shown in the drawings, the wafer storage area 
42 is not maintained under any particular pressure and, therefore, is 
generally at atmospheric pressure. It should be understood, however, that 
area 42 could be at some other pressure which may be necessary or 
convenient for the storage or processing of the semiconductor wafers. It 
is therefore apparent that the transfer chamber 26 serves as a buffer or 
transition zone between a location such as the reaction chamber 12, which 
is usually maintained at a vacuum, and any other location, such as storage 
area 42, which in the present embodiment is at atmospheric pressure, but 
may be at any other pressure. In addition, it should be appreciated that 
although area 42 is shown as being generally open, it could be an enclosed 
area or chamber. Thus, the transfer apparatus 14 could be employed to 
transfer the semiconductor wafers between, for example, two chambers of 
differing and preferably, subatmospheric pressures to isolate one chamber 
from the other. 
The second transfer port 40 extends through reaction chamber sidewall 16 as 
shown to provide communication between the transfer chamber 26 and the 
reaction chamber 12. As will hereinafter be described in greater detail, 
port actuator means identified generally as 46 are provided for opening 
and closing the first and second transfer ports 38 and 40. 
Referring now to FIG. 5, there is shown in greater detail the first 
transfer port 38 and the associated transfer port actuator means 46. For 
purposes of clarity and brevity the structure and operation of only the 
first transfer port 38 will be presented, it being understood that the 
structure and operation of the second transfer port 40 is substantially 
the same. As shown in FIG. 5, port 38 comprises an elongated, generally 
rectangularly shaped slot or opening 48 extending through a portion of 
transfer chamber sidewall 28. A corresponding elongated, generally 
rectangularly shaped door member 50 is located proximate the rectangular 
opening 48. The door member 50 is slightly larger than the rectangular 
opening 48 and is shown in the open position in FIG. 5. A generally 
cylindrical pin member 52 is positioned on each of the upper elongated 
ends of the door member 50. The pin members 52 extend through suitably 
sized openings 54 within support blocks 56 which are attached to the 
transfer chamber sidewalls 30 and 32 for supporting the door member 50. As 
shown in FIGS. 1, 2 and 5, the pin members 52 cooperate with the support 
block openings 54 to permit the door member 50 to swing or pivot in a 
clockwise or counterclockwise direction when viewing FIG. 5, to close or 
open, respectively, the rectangular opening 48 when actuated in a manner 
which will hereinafter be described. 
The transfer port actuator means 46 associated with port 38 further 
comprises an elongated actuator shaft 58 positioned proximate to the door 
member 50 and supported for rotation within suitably sized openings 60 
extending through the transfer chamber sidewalls 30 and 32 and through the 
attached supporting blocks 62. One end of the actuator shaft 58 extends 
beyond the transfer chamber wall 30 as shown in FIG. 5. A pinion 64 having 
suitable gear teeth is secured to the outwardly extending portion of the 
shaft 58. The pinion 64 engages a rack 66 having similarly sized gear 
teeth which is attached to or formed on at least a portion of the piston 
rod 68 of cylinder 70. In the present embodiment, the cylinder 70 is an 
air controlled cylinder of a type which is well-known in the art and which 
may be purchased commercially from the Rotomation Corp. of Daytona Beach, 
Fla. Specific details of the structure and operation of the air actuated 
cylinder 70 are not considered to be necessary for a complete 
understanding of the present invention and, therefore, will not be set 
forth herein. Suffice it to say that the introduction of pressurized air 
into the cylinder 70 causes a piston (not shown) and an attached piston 
rod 68 to translate in one direction or the other as indicated by the 
arrows adjacent the piston rod 68. Translational movement of the piston 
rod 68 causes the rack 66 to drive the pinion 64 which in turn rotates the 
shaft 58 as shown by the arrows adjacent the shaft 58 in FIG. 5. 
Attached to the actuator shaft 58 approximately midway along its length is 
a radially outwardly extending flange member or lug 72. A pair of roller 
bearings 74 are supported for rotation upon an axle member 76 extending 
through suitably sized openings within the distal end of the lug 72. A 
central portion of the distal end of lug 72 is cut away or removed at 78 
to expose a portion of the axle 76 which is attached to tension or biasing 
means, such as a coil spring 80. The other end of the coil spring 80 is 
attached to the door member 50 at a point offset from the door member 
pivot pins 52. 
In operation, when it is desired to open the door member 50, air is 
introduced into the lower end (head side) of the cylinder 72 to move the 
piston and piston rod 68 upwardly thereby causing the shaft 58 to rotate 
in a counterclockwise direction as illustrated in FIG. 5. The rotation of 
the shaft 58 and the corresponding rotational movement of the lug 72 
tensions the coil spring 80, thereby causing the lower end of the door 
member 50 to pivot upwardly about the axis and away from the rectangular 
opening to the open position as shown in FIGS. 1, 2 and 5. When it is 
desired to close the rectangular opening 48, pressurized air is introduced 
into the rod side of the cylinder 72 and the piston and piston rod 68 move 
downwardly causing the shaft 58 to rotate in a clockwise direction as 
illustrated in FIG. 5. The clockwise rotation of the shaft 58 causes the 
bearings 74 on the end of the lug 72 to engage the door member 50 causing 
the door member to pivot about the pin members 52 to the closed position 
(shown in FIGS. 1 and 2). Suitable sealing means, for example, neoprene or 
similar seals 82 are provided on the door member 50. The bearings 74 bear 
against the door member 50 in a generally perpendicular manner to put a 
generally normal compression force on the door member 50 to properly 
compress the seals 82 against the sidewall 28 to provide an airtight 
pressure seal. 
Referring to FIGS. 1, 2 and 3, the transfer apparatus 14 further includes a 
transfer arm means identified generally as 84 for receiving unprocessed 
semiconductor wafers from the conveyor belts 44 and for transferring the 
wafers into the reaction chamber 12. In the presently preferred embodiment 
the transfer arm means 84 comprises first and second generally 
horizontally oriented elongated transfer arm members 86 and 88, 
respectively. A first end of the first transfer arm member 86 is pivotally 
supported proximate to the center of the transfer chamber 26 in a manner 
described hereinafter. A first end of the second transfer arm member 88 is 
pivotally supported proximate to the second end of the first transfer arm 
member 86. The second end of the second transfer arm member is adapted to 
receive and support a generally flat semiconductor wafer, shown in phantom 
in FIG. 3 as 90. As best seen in FIG. 3, the second end of the second arm 
member 88 generally has the same shape as the semiconductor wafer. For 
example, where the wafer is circular, the second end of the second arm is 
in the form of an annular ring member 92 having an inner diameter slightly 
greater than the outer diameter of the semiconductor wafer 90. The annular 
ring member 92 has a radially inwardly extending annular flange member or 
lip 94 having an inner diameter which is slightly less than the outer 
diameter of the semiconductor wafer so that the lip 94 forms an annular 
shoulder for supporting the semiconductor wafer as shown. The vertical 
height of the annular ring member 92 is at least slightly greater than the 
overall thickness of the semiconductor wafer 90 so the wafer may be 
retained within the annular ring 92 with little chance of it becoming 
dislodged due to the horizontal pivotal movement of the second arm member 
88. A small arcuate portion of the annular ring member 92 and the annular 
lip member 94 is cut away or removed to form a slot 93 as shown in FIG. 1. 
The purpose of the slot 93 is to permit the second arm member 88 to be 
withdrawn from the reaction chamber 12 after a wafer 90 has been lifted 
upwardly by a wafer lifting device 25 (best seen in FIG. 2) which is 
employed to move the wafer onto the supporting platen 24. 
Referring now to FIG. 1, it can be seen that the first and second arm 
members 86 and 88 cooperate to pivot horizontally through approximately 
180 degrees to at least three different positions. In the first, lefthand 
position as shown in phantom, both of the arm members 86 and 88 extend 
toward the left when viewing FIG. 1, the respective lengths of the arm 
members being such that at least a portion (approximate 3/4 of the length) 
of the second arm member 88 extends through the first transfer port 38 for 
receiving a semiconductor wafer from the conveyor belts 44. In the second, 
righthand position as shown in solid lines in FIG. 1, both of the arm 
members 86 and 88 extend toward the right when viewing FIG. 1. In the 
second position, at least a portion (approximately 3/4 of the length) of 
the second arm member 88 extends into the reaction chamber 12 to permit 
the removal of a semiconductor wafer by the upward movement of the wafer 
lifting device 25. In the intermediate position which is also shown in 
phantom in FIG. 1, both of the arm members 86 and 88 are entirely located 
within the transfer chamber 26 with the second arm member 88 being 
positioned substantially above and parallel to the first arm member 86 as 
shown. 
As will be apparent from the foregoing description, when the arm members 86 
and 86 are in the first position an unprocessed semiconductor wafer 90 may 
be transferred from the conveyor belt 42 onto the second end of the second 
arm member 88. Thereafter, the two arm members 86 and 88 may be pivoted 90 
degrees to the intermediate position in the transfer chamber 26 and an 
additional 90 degrees to the second position where the unprocessed wafer 
90 may be removed for processing within the reaction chamber 12. By 
employing mechanically simple transfer arm members 86 and 88 which 
cooperate in this manner, the size of the transfer chamber 26 can be kept 
relatively small. 
The transfer apparatus 14 also includes arm member actuator means 
identified generally in FIG. 3 as 96 for pivoting the first and second 
transfer arm members 86 and 88 to the first, second and intermediate 
positions as previously described. As best seen in FIGS. 2 and 3, in the 
presently preferred embodiment, the arm member actuator means 96 comprises 
a drive motor 98 (in the present embodiment a reversible electric motor) 
having an output shaft 100 which is coupled to the input shaft 102 of a 
geneva drive mechanism 104. Both the motor 98 and the geneva drive 104 are 
of the type well-known in the art and generally commercially available 
from a variety of manufacturers, such as the Barber-Colman Company of 
Rockford, Ill. in the case of the motor 98 and the PIC Company in the case 
of the geneva drive 104. Therefore, specific details of the structure and 
operation of the motor 98 and the geneva drive 104 will not be presented 
herein. Suffice it to say that the motor 98 is a standard reversible DC 
gear type motor and the geneva drive is of the type which provides 90 
degrees of rotation of the output shaft 106 for every full revolution of 
the input shaft 102 and that the motor 98 and the geneva drive mechanism 
104 cooperate for the 180 degree pivotal movement of the transfer arm 
members 86 and 88. It should be appreciated that the arm member actuator 
means 96 could alternatively comprise a stepper motor (not shown) or any 
other suitable device to provide the desired movement of the arm members 
84 and 86. 
The geneva drive output shaft 106 is coupled to an extension shaft 
(hereinafter called the geneva drive output shaft 106, for simplicity) 
which extends upwardly through a suitable opening in the transfer chamber 
bottom wall 36 as shown. Suitably rotary seals are provided where the 
shaft 106 extends through the transfer chamber bottom wall 36 in order to 
maintain the airtight condition of the transfer chamber. The first end of 
the first transfer arm member 86 is secured to and rotates with the upper 
end of the shaft 106. The first arm member 86 may be secured to the shaft 
106 by any suitable means, for example by one or more inwardly extending 
threaded pins 108 (only one of which is shown). A first sprocket member 
110 is also secured to the chamber so as to not rotate with the first 
transfer arm member 84. 
As best seen in FIG. 3, the second or distal end of the first arm member 86 
includes an double offset portion 112 which is employed for supporting the 
second arm member 88. The portion 112 includes an opening (not shown) 
through which extends a generally vertically oriented supporting shaft 114 
journaled for rotation by suitable bearings (not shown). The first end of 
the second arm member 88 is secured to the upper end of the supporting 
shaft 114 by any suitable means, such as pins (not shown) so that the 
second arm member 88 pivots upon the rotation of the supporting shaft 114. 
A second sprocket member 116 is also secured to the lower end of the 
supporting shaft 114 as shown. A drive belt, in the present embodiment an 
endless stainless steel drive belt 118 having a plurality of notches or 
openings 120 extending therethrough, connects the first sprocket member 
110 to the second sprocket member 116 as best shown in FIGS. 3 and 4. The 
teeth on the first and second sprocket members 110 and 116 engage the 
openings 120 of the drive belt 118 so that rotation of the first arm 
member 84 results in a corresponding rotation of the second sprocket 
member 116. The angular displacement of the upper, second transfer arm 
member 88 with respect to the lower, first transfer arm member 86 is 
determined by the ratio of the diameters of the two sprocket members 110 
and 116. As shown in FIGS. 3 and 4, the first arm member 86 further 
includes a telescoping portion 122 and a biasing means, such as a 
compressed coil spring 124, to maintain a constant tension upon the drive 
belt 118. 
A flat, generally circular cam means, such as a cam member 126 is secured 
to and rotates with the shaft 106. As explained hereinafter, three 
position indicating openings 128 extend through the cam member 126. An 
optically operated switch means, such as an optical switch 130, is 
positioned proximate to the cam member 126 as shown in FIGS. 2 and 3. The 
optical switch 130 is of a type well-known in the art and commercially 
available from the Dyneer Corp. of Chatsworth, Calif. Details of the 
structure of the optical switch 130 are well known and will not be 
presented herein. Operationally, the optical switch 130 provides an 
electrical output signal when a light beam positioned on one side of the 
cam member 126 is sensed on the other side of the cam member 126, 
indicating that one of the three cam members openings 128 is in registry 
with the optical switch 130. By placing the optical switch 130 and the cam 
member openings 128 in the manner as shown an electrical output signal is 
generated by the optical switch 130 when the first and second transfer arm 
members 86 and 88 are in the first, second or intermediate positions as 
described above and as indicated in FIG. 1. The generated electrical 
signals are used to control and coordinate the operation of the transfer 
apparatus as will be described hereinafter. The optical switch 130 and the 
cam member 126 cooperate to provide a positive indication of the position 
of the transfer arm members 84 and 86 and thus the wafer during the 
transfer process. 
The cam member 126 is also adapted to engage a cam follower means 132 which 
is connected to a pressure actuated switch means, such as a microswitch 
134 as shown in FIG. 3. As long as the cam follower 132 engages the 
smaller diameter portion of the cam member 126, the microswitch 134 is not 
actuated. However, if the shaft 106 were to rotate so that the cam 
follower 132 were to engage the larger diameter portion of the cam member 
126, the microswitch 134 would be actuated to turn off the motor 98 to 
prevent any further rotation of the shaft 106. The cam follower 132 and 
microswitch 134 thus serve as a safety device to prevent the geneva drive 
output shaft 106 and thus the two arm members 86 and 88 from rotating 
further than the 180 degrees (90 degrees on either side of the third or 
intermediate position) required for the transfer of the semiconductor 
wafers. 
FIG. 6 illustrates the essential details of means for the pre-treatment of 
a semiconductor wafer within the transfer chamber 26. In the present 
embodiment, the pre-treatment consists of the use of a glow discharge 
process for the purpose of preetching or desmearing of the wafer. However, 
it should be appreciated that any other type of pre-treatment process such 
as photo-resist hardening could alternatively be employed. Additionally, 
although not shown in the drawings, a post-treatment process could be 
similarly employed in connection with the removal of the process 
semiconductor wafers from the reaction chamber utilizing the second 
transfer apparatus 14a. 
In the presently preferred embodiment, the pretreatment means comprises a 
wafer platen 140 which is positioned directly beneath the distal or second 
end of the second transfer arm member 88 when the transfer arm members 86 
and 88 are in the intermediate position (see FIG. 1). The wafer platen 140 
has an outer diameter which is slightly less than the inner diameter of 
the annular lip 94 of the second transfer arm 88 so that the platen 140 
may be moved upwardly to lift the wafer off of the lip 94 and to provide 
firm support over the entire surface of the wafer. In the presently 
preferred embodiment, the platen 140 is moved upwardly and downwardly by 
an air actuated cylinder 142 having a piston (not shown) and a piston rod 
144 connected to a generally cylindrical shaft 146 which supports the 
platen 140. Suitable upper and lower limit stops 148, bearings 150 and 
seals 152 facilitate the upward and downward movement of the shaft 146 and 
maintain the pressure within the transfer chamber 26. The temperature of 
the platen 140 is controlled utilizing suitable means, such as electrical 
wires or fluid conduits (not shown), to maintain the semiconductor wafer 
at a predetermined temperature. 
Positioned directly above the platen 140 is an RF electrode 154 which is 
employed in conjunction with the glow discharge process. Such devices are 
generally well known in the art and will not be described in detail 
herein. 
A control means 158 (shown in functional block diagram form only in FIG. 2) 
coordinates and controls the operation of the transfer port actuator means 
46, the transfer arm member actuator means 96, the pressure adjusting 
means and the pre-treatment means. The control means 158 receives 
electrical signals from the optical switch 130 and other sensor means, 
such as pressure and temperature sensors, (not shown) for controlling and 
coordinating the wafer transfer operation. In the presently preferred 
embodiment, the control means 158 is a preprogrammed microprocessor 
equipped control system. However, it should be appreciated that any other 
conventional type of control system alternately could be employed. 
Referring to FIG. 1, operation of the transfer apparatus 14 will now be 
described. For purposes of illustrating the operation of the transfer 
apparatus 14, the initial position of the transfer arm members 86 and 88 
will assumed to be the intermediate position with both of the transfer 
ports 38 and 40 being closed. 
To begin the transfer operation, the control means 158 activates the 
pressure adjusting means to adjust the pressure within the transfer 
chamber 26 to correspond to the pressure of the wafer storage area 42 
(substantially atmospheric in the present embodiment). Once the pressure 
within the transfer chamber substantially corresponds to the pressure of 
the wafer storage area 42, the control means 158 activates the port 
actuator means 46 to open the first transfer port 38. The motor 98 is then 
energized to pivot the two transfer arm members 86 and 88 to the first 
position as shown in phantom in FIG. 1. When the first and second transfer 
arm members 86 and 88 are in the first position, the control means 
receives an electrical signal from the optical switch 130 and deenergizes 
and reverses the motor 98 to prevent further movement of the transfer arm 
members 86 and 88. The wafer storage device 43 and the conveyor belts 44 
are then activated to transfer a semiconductor wafer and deposit the same 
upon the distal end of the second transfer arm member 88. The conveyor 
belts 44 are then pivoted or otherwise moved out of the way and the motor 
98 is energized to move the first and second transfer arm members in the 
opposite direction to the intermediate position within transfer chamber 26 
as shown in phantom in FIG. 1. When the transfer arm members 86 and 88 
reach the intermediate position, the optical switch 130 generates an 
electrical signal which deenergizes the motor 98 and causes the port 
actuator means 46 to close and seal the first transfer port 38. The platen 
140 is moved upwardly as previously described to engage and support the 
wafer and the preprocessing treatment is conducted. Once the preprocessing 
treatment has been completed, the wafer supporting platen 140 is lowered. 
The pressure adjusting means may be activated either before, during or 
after the preprocessing treatment to adjust the pressure within the 
transfer chamber 26 to substantially correspond to the pressure (usually a 
vacuum) within the reaction chamber 12. Once the pressure within the two 
chambers 12 and 26 substantially correspond, the port actuator means 46 is 
activated to open the second transfer port 40 as shown in FIG. 2. The 
motor 98 is again energized to cause the first and second transfer arm 
members 86 and 88 to pivot 90 degrees to the second position as shown in 
solid lines in FIG. 1. Once the first and second transfer arms 86 and 88 
reach the second position, a signal generated by the optical switch 130 
deenergizes and reverses the motor. The wafer lifting device 25 then moves 
upwardly to lift the wafer 90 above the top of the annular ring member 92 
on the second transfer arm 88 as shown in phantom in FIG. 2. Thereafter, 
the motor 98 is again energized to pivot the first and second transfer arm 
members 86 and 88 back to the intermediate position (the slot 93 
permitting the annular ring 92 to pass through the raised lifting device 
25) and the second port 40 is actuated by the port actuator means 46 to 
the closed position. The wafer lifting device 25 then lowers the wafer 90 
onto the supporting platen 24 and the plasma gas reaction process is 
conducted. 
From the foregoing description it can be seen that the present invention 
comprises an apparatus for conveying a semiconductor wafer between two 
locations, each of which may be at a different pressure, without 
disturbing the pressure at either location. The present invention also 
provides for the possibility of pre-treatment or post-treatment of the 
semiconductor wafer during the transfer operation. It will be recognized 
by those skilled in the art that changes could be made to the 
above-described embodiment of the invention without departing from the 
broad inventive concepts thereof. It is understood, therefore, that this 
invention is not limited to the particular embodiment disclosed, but it is 
intended to cover any modifications which are within the scope and spirit 
of the invention as defined by the appended claims.