Multi-position load lock chamber

A machine for manufacturing semiconductor devices has a. processing chamber for processing the semiconductor wafer. A transfer chamber has at least two positions, one position to facilitate the transfer of a wafer to be processed into the transfer chamber and to facilitate the transfer of a processed wafer from the transfer chamber to the cassette from which the wafer originated. The second position facilitates the transfer of a wafer to and from the processing chamber. A transfer arm simultaneously transfers an unprocessed wafer from the first position to the second position with the transfer of a processed wafer from the second position to the first position.

BACKGROUND OF THE INVENTION 
The present invention relates to the field of semiconductor wafer 
processing, and more specifically, to a multi position load lock chamber 
used in semiconductor wafer processing. 
FIG. 1 is an isometric view of a piece of semiconductor manufacturing 
equipment (an epitaxial reactor 10). The epitaxial reactor 10 is 
partitioned into the wafer handling chamber 16, load locks 14 and 15, and 
a process chamber 20 that is isolated from the load locks 14 and 15 and 
the wafer handling chamber 16 by isolation gate valve 18. 
In operation, cassettes of semiconductor wafers (not shown) are placed in 
the load locks 14 and 15 through load lock portals 32 and 34. After 
loading the wafer cassettes into the load locks 14 and 15, the load lock 
portals 32 and 34 are closed to isolate the wafers from the surrounding 
atmosphere. The load locks are purged by the purge gas that purges out 
oxygen, moisture and any undesirable particles that may have inadvertently 
entered the load locks 14 and 15 while the load lock portals 32 and 34 are 
opened to receive the wafer cassettes. 
After completing the purge, the load locks 14 and 15 are opened to the 
wafer handling chamber by lowering the cassette in an elevator (not shown) 
which breaks an air tight seal. The wafers are then transported 
sequentially from the cassettes to the process chamber 20 by a transfer 
arm 29 that has, for example, a Bernoulli wand end effector 36. 
Subsequent to the purging of the load locks 14 and 15 and wafer handling 
chamber 16, the isolation valve 18 is opened. The transfer arm 29 is used 
to move the wafers from the load lock 14 or 15 into the process chamber 20 
for wafer processing. The transfer arm 29, including a low ingestion 
Bernoulli wand 36, is within the wafer handling chamber 16. In operation, 
the Bernoulli wand 36 picks up the semiconductor wafers one at a time from 
the cassettes (not shown) in one of the load locks 14 and 15. Each wafer 
is then transported through the open isolation gate valve 18 to a 
susceptor 38 within the process chamber 20. 
After the processing of the wafer is completed, the isolation gate valve 18 
is opened and the Bernoulli wand 36 picks up the wafer and returns it to 
the slot within the same cassette that the wafer was originally retrieved 
from. 
Although the above system is very successful, there is always a desire by 
the semiconductor manufacturers to increase the throughput of their 
equipment. However, factory space comes at a premium so that the use of 
factory floor area for processing equipment must be maintained at a 
minimum. Additionally, the semiconductor manufacturers appreciate the 
advantage of performing both preprocessing and post processing operations 
on semiconductor wafers without affecting the throughput of the processing 
equipment or the footprint of the equipment on the factory floor. 
SUMMARY OF THE INVENTION 
A machine for manufacturing semiconductor devices has a processing chamber 
for processing the semiconductor wafer. A transfer chamber has at least 
two positions. One position facilitates the transfer of a wafer to be 
processed into the transfer chamber and facilitates the transfer of a 
processed wafer from the transfer chamber to the location from which the 
wafer originated. The second position facilitates the transfer of a wafer 
to and from the processing chamber. A transfer arm simultaneously 
transfers an unprocessed wafer from the first position to the second 
position with the transfer of a processed wafer from the second position 
to the first position. 
In other embodiments there are multiple wafer positions identified that 
enable the increase in the throughput of the semiconductor apparatus over 
the prior art machines. At each position, prior to processing, there can 
be preprocessing operations performed such as cleaning of the wafer, gas 
treatment, measurements and even a processing step. Similarly, at the 
wafer position following the processing of a wafer, different post 
processing procedures can be performed such as measuring the results of 
the processing step, allowing the wafer to cool down prior to returning it 
to the cassette, or even performing an additional processing step.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
Turning now to the drawings, there is shown in FIG. 2 a block diagram of a 
processing unit 100 constructed according to the present invention. As 
shown in FIG. 2, a processing unit 100 that includes a processing chamber 
20, a wafer handling module 50, a cassette to load lock transfer module 30 
and a cassette placement module 12. Cassette placement module 12 is where 
an operator or mechanical device places cassettes 65 and 66 for processing 
and retrieving the cassettes 65 and 66 at the completion of the processing 
of all of the wafers. The cassette to load lock transfer module 30 
includes a mechanical arm 26 with an end effector, which is known in the 
art, and is adapted to retrieve a wafer from either cassette 65 or 66 and 
place the retrieved wafer in a load lock 60 and to retrieve a wafer from 
the load lock 60 following processing and transfer it to the originating 
slot within either the cassette 65 or 66 from which it was initially 
retrieved. The mechanical arm 26 must be able to move in all three 
coordinates or the cassettes 65 and 66 must be adjustable to the 
appropriate elevation and/or orientation to allow the mechanical arm to 
retrieve and return the wafer to the location in the respective cassette. 
The processing chamber 20 is separated from the wafer handling module 50 by 
a gate valve 62. A mechanism 70 in a chamber 24 is used to transfer wafers 
through gate valve 62 is a Bernoulli wand (such as the devices described 
in U.S. Pat. Nos. 5,080,549 and 5,324,115 that are incorporated herein by 
reference). Mechanism 70 transfers wafers between the wafer handling 
module 50 and the process chamber 20 and in particular to a susceptor 
within the process chamber 20. 
As best seen in FIGS. 2 through 5, wafer handler module 50 having walls 52, 
54, 56, and 58 contains a load lock 60 that has a gate valve 61, which is 
opened and closed by a gate valve actuator. The wafer handler module 50 
has four stations that include: a load lock station 90, a preprocessing 
station 92, a wand station 94, and a post processing station 96. Wafers 
within the preprocessing station 92 can be pre-measured and pre-cleaned 
using techniques known in the art. Similarly, wafers in the post 
processing station can be cooled down after processing and post 
measurement can be performed such as measuring the thickness of the 
epitaxial growth layer if the processing chamber is an epitaxial growth 
chamber and can be measured using techniques known in the art. 
The load lock 60 provides access to the wafer handling module 50 for the 
mechanical arm 26 so that a wafer can be transferred between a source, 
such as cassettes 65 and 66, and the load lock station 90. A wafer handler 
80, shown in a rest position 86 between the four stations, is comprised of 
arms 82 and end effectors 84a, 84b, 84c, and 84d for carrying the wafers. 
The wafer handler 80 rotates between the wafer stations 90, 92, 94 and 96, 
in such a way that when properly oriented in each position 90, 92, 94 and 
96, end effectors 84a through 84d of the wafer handler 80 are selectively 
centered over load lock station 90, preprocessing station 92, wand station 
94, and post processing station 96. When at rest, the arms 82 of the wafer 
handler are centered between the stations as is shown in FIG. 3. Load lock 
station 90, preprocessing station 92, wand station 94, and post processing 
station 96 include a base plate 21 that is approximately the same size as 
the wafer to be processed and three wafer support pins 91, 93, and 95, 
which support the wafers at the associated stations. The elevation and 
orientation of the pins facilitate the end effectors 84a through 84d of 
the arm 82 to be disposed under the wafers positioned on the pins when the 
wafer handler 80 is in the low position and is rotating counterclockwise. 
The geometric orientation of the pins is illustrated in FIG. 4 where pin 
95 is the base pin, pin 93 is 105.degree. counterclockwise from pin 95, 
and pin 91 is 210.degree. counterclockwise from pin 95. 
Although the pins 91, 93, and 95 have the same elevation and are fixed to 
the baseplate it is known in the art to have moveable and retractable pins 
in wafer processing equipment. 
The wafer handler 80 rotates under the control of the actuator 74 and is 
raised and lowered by lift actuator 76, which are both located underneath 
the wafer handler module 50. The load lock 60 is mounted above the load 
lock station 90. An elevator 37 including shaft 63 raises and lowers the 
plate 21 between the load lock 60 and the wafer handler module 50. When 
the plate 21 is level with line 35, the top of the pins 91, 93, and 95 are 
positioned within the gate valve 61 to receive the wafers from the 
mechanical arm 26. The low position is when the plate 21 of the load lock 
station 90 is in line with elevation line 41. 
The edge 39 of the plate 21 is designed to form an air tight seal with the 
load lock chamber 60 when the elevator 37 is in the raised position, i.e. 
the plate 21 is level with line 35. When in the raised position and the 
gate valve 61 is closed, the load lock chamber 60 may be purged with a 
purge gas. The purging of load lock is known in the art. 
In a similar manner, the gate valve 62 is positioned adjacent a chamber 22 
which is over the wand station 94. An elevator 23 including shaft 64 moves 
the wafers from level 41 to level 27 for positioning the wafers to be 
retrieved by the end effector mechanism 70. Although end effector 70 can 
be a standard paddle type end effector, it is preferred that a Bernoulli 
wand construction be used. In the embodiment shown, the elevators 23 and 
37 and actuators 74 and 76 are pneumatic devices. 
The operation of the rotary load lock can be better understood by referring 
to the FIGS. 2 through 6, 8a, 8b, 9, and 11 through 13 which shows the 
apparatus, in conjunction with FIGS. 7 and 10, which shows the positioning 
of each apparatus. In FIG. 6, the wafer handler 80 is shown in its rest 
position, a wafer W1 is being processed within the process module 20, a 
wafer W2 is waiting to be processed in the position 92, and a wafer W3 is 
being purged in the load lock 60. The elevator 37 is raised into the load 
lock 60 and the elevator 23 is raised into the gate valve 62. While the 
elevator 37 is in the raised position and the gate valve 61 is closed, the 
load lock 60 is purged with a purge gas, simultaneously with the process 
of wafer W1. 
After the processing of wafer W1 is completed, the end effector mechanism 
70 transfers the wafer W1 from the processing module 20 onto the pins 
91,93 and 95 of the plate 21 located at the wand station 94, which has 
been raised into the chamber 22 adjacent the gate valve 62. The elevator 
23 is then lowered to position 41. Following the purge of the load lock 
60, the elevator 37 is lowered to position level 41. The timing for the 
above operation is given in FIGS. 7a through 7d. 
In particular, referring to FIGS. 2 and 5 and the timing diagram 
illustrated in FIG. 7a the transfer of the wafer from the cassette to the 
load lock station 90 is depicted. During the first period, the mechanical 
arm 26 retrieves a wafer from either cassette 66 or 65 and the gate valve 
61 is opened. Following the retrieval of the wafer, the mechanical arm 26 
places the wafer on the load lock station 90 during the second period. 
After the mechanical arm 26 is removed, the gate valve 61 is closed during 
the third period and following that, the load lock 60 is purged. In the 
fifth period, the elevator 37 is lowered to become in alignment with 
position line 41. 
FIG. 7b illustrates the retrieval of a processed wafer from the load lock 
station 90 by the mechanical arm 26 and provides for, in the first period, 
the elevator 37 to raise the wafer to position line 35. In this position, 
the load lock 60 can then be purged and following which, during the third 
period, the gate valve 61 is opened. The mechanical arm 26 retrieves the 
wafer from the pins and places the wafer within one of the cassettes 65 or 
66 during the fifth period. Simultaneously with the placement of the 
wafer, the gate valve 61 is closed. 
FIG. 7c illustrates the sequence of operations of the wand station 94. 
During the first period, the end effector mechanism 70 is positioned to 
retrieve a wafer from the wand station 94. The wand station is raised into 
alignment with gate valve 62 which is indicated by position level 51. The 
end effector mechanism 70 lifts a wafer from the wand station 94 following 
which the wand station 94 is lowered during the fourth period. In the 
fifth period, the end effector mechanism 70 and the wafer are positioned 
to enter the process chamber 20. The gate valve is opened in the sixth 
period and the wafer is placed on a susceptor within the process chamber 
20 and the end effector mechanism 70 leaves the process chamber 20 after 
which the gate valve 62 is closed during the eighth period. 
FIG. 7d provides for removing the processed wafer from the process chamber 
20 in which in the first period gate valve 62 is opened and during the 
second period the end effector mechanism 70 retrieves the wafer. The wafer 
and end effector mechanism are positioned over the wand station 94 during 
the fourth period. The wand station 94, in the fourth period, is lifted up 
and during the fifth period the end effector mechanism 70 places the wafer 
on the wand station 94 and is removed following which the gate valve is 
closed and during the sixth period, the wand station 94 is lowered to line 
41. 
In FIG. 8a, the wafer handler 80 has been rotated 450 counterclockwise so 
that the end effector 84a is located under wafer W3, end effector 84b is 
located under wafer W2, end effector 84c is located under the processed 
wafer W1 and end effector 84d is located at the post processing station 
96. At this point the lift actuator 76 raises the wafer handler 80 above 
the level of the pins 91, 93 and 95 as illustrated by dotted line 51 as 
shown in FIG. 5 and rotates 90.degree. counter clockwise as is shown in 
FIG. 9. 
In FIG. 8b, the wafer handler 80 has been lowered by the lift actuator 76 
to rest wafer W3 on the pins 91, 93, and 95 located at preprocessing 
station 92. The wafer handler is then rotated in the rest position as 
shown in FIG. 3. While at the preprocessing station 92, there can be 
measurements made on the wafer W3, preprocessing cleaning can be performed 
on the wafer W3, or as is illustrated in FIG. 11, an initial preprocessing 
step may be completed. Wafer W2 rests on the pins 91, 93, and 95 at the 
wand station 94 while wafer W1 is at the post processing station 96. Wafer 
W2 is waiting to be raised and placed into the processing chamber 20 as is 
discussed in FIG. 7c. At the post processing station 96, wafer W1 can be 
cooled down. Additionally, at post processing station 96 measurements can 
be made such as the thickness of the epitaxial layer that has been made on 
top of the wafer W1 while it was going through the processing steps or 
alternatively as can be seen from FIG. 11, other processes may be 
completed at the post processing station 96. 
In FIG. 9 elevator 23 has raised wafer W2 into alignment with the gate 
valve 62 where the end effector 70 retrieved it and placed the wafer W2 in 
the process chamber 20. Similarly, elevator 37 has been raised into the 
load lock 60 where mechanical arm 26 has retrieved the wafer W4 from one 
of the cassettes 65 and 66 and placed in the load lock. 
This process is repeated and continues until all of the wafers have been 
processed. 
FIGS. 10a through 10c are timing diagrams for the processing of a series of 
six wafers and should be used in conjunction with FIGS. 2 through 6, 8a, 
8b, 9 and 11 through 13. Referring to FIG. 10a, in the 1st. period a wafer 
W1 is retrieved from a cassette either 65 or 66 located within the 
cassette placement module 12. The mechanical arm 26 transfers the wafer W1 
to the load lock station 90. The rotary handler 80 is then indexed or 
rotated during the 2nd. period. 
In the 3rd. period, the wafer W1 is transferred to the preprocessing 
station 92 due to the indexing of the rotary handler 80 and a new wafer W2 
is transferred from the cassette placement module 12 by the mechanical arm 
26 to the load lock station 90. In the 4th. period, the rotary handler 80 
is indexed once more, the wafer W1 to the wand station 94 and the wafer W2 
to the preprocessing station 92. The wafer W1 next is transferred to the 
processing chamber by the end effector in the 5th. period. 
While the wafer W1 is being processed during the 6th. period, a new wafer 
W3 is transferred to the load lock station 90 by the mechanical arm 26. 
After processing, the 7th. period, the wafer W1 is transferred from the 
process chamber 20 by the end effector to the wand station 94. 
The rotary handler 80 is now ready to be indexed in the 8th. period and in 
the 9th. period. Thus, wafer W2 is transferred to the process chamber 20 
from the wand station 94 by the end effector. The wafer W1 is now in the 
post processing station 96 where different post processing procedures may 
be implemented or the wafer will just be allowed to cool, and the wafer W3 
is located in the preprocessing station 92. The load lock station 90 is 
now free to receive another wafer which occurs during the 10th period when 
the mechanical arm retrieves wafer W4 from a cassette in the cassette 
placement module 12 and loads it into the load lock station 90. 
In the 11th. period, the wafer W2 is transferred to the wand station 94 and 
the rotary handler 80 is now ready to be indexed which it does in 12th. 
period. In the 13th. period, the wafer W3 is now in the wand station 94 
and can be transferred into the process chamber 20 by the end effector 36 
during the 13th. period. During the 14th. period, wafer W1 is located at 
the load lock station 90 and can be retrieved by the mechanical arm 26 and 
placed within the cassette within the cassette placement module 12. The 
load lock station 90, thus being empty, is ready to receive another wafer 
during the 15th. period in which case the mechanical arm 26 transfers 
wafer W5 from a cassette in the cassette placement module 12 to the load 
lock station 90. In the 16th. period, wafer W3 is transferred from the 
process chamber 20 by the Bernoulli wand 70 back to the wand station 94. 
The rotary handler 80 is now ready to be indexed which it does during the 
17th. period. In the 18th. period, the wafer W4 is now in the wand station 
94 and can be transferred to the process chamber 20 by the end effector 
70. Similarly, the wafer W2 which has been processed is now in the load 
lock station 90 and can be retrieved and placed within a cassette within 
the cassette placement module 12 by the mechanical arm 26 during the 19th. 
period. The placement of the wafer W2 or within a cassette within the 
cassette placement module 12 frees the load lock station 90 for the 
receipt of a new wafer W6 from the cassette placement module 12 which the 
mechanical arm does retrieve and place within the load lock station 90 
during the 20th. period. 
In the 21st. period, the processing of wafer W4 is now completed and the 
end effector 70 retrieves the processed wafer W4 and places it within the 
wand station 94. The rotary handler 80 indexes during the 22nd. period. 
FIG. 10c provides for the final sequence to complete the cycle of 
processing of the six semiconductor wafers. During the 23rd., wafer W5 is 
transferred from the wand station into the process chamber 20 by the end 
effector 70. In the 24th. period the wafer W3 being in the load lock 
station 90 is transferred to the cassette placement module 12 by the 
mechanical arm 26. Following the processing of wafer W5, it is transferred 
during the 25th. period from the process chamber 20 to the wand station 94 
by the end effector 70. 
The rotary handler 80 is indexed during the 26th. period to place the wafer 
W4 in the load lock station 90 and wafer W6 in the wand station 90 with 
wafer W5 being in the post processing station 96. Wafer W6, during the 
27th. period is transferred to the process chamber 20 by the end effector 
70. In the 28th. period, wafer W4 is transferred from the load lock 
station 90 to the cassette placement module 12 by the mechanical arm 26. 
In the 29th. period, the processing of wafer W6 is completed, the end 
effector 70 retrieves the wafer W6 and places it in the wand station 94. 
The rotary handler 80 indexes during the 30th. period and in the 31st. 
period the wafer W5 is brought into the load lock station 90 where it is 
transferred to a cassette within the cassette placement module 12 by the 
mechanical arm 26. 
The rotary handler 80 then indexes in the 32nd. period to place wafer W6 at 
the load lock station 90. This facilitates the mechanical arm 26 
retrieving the wafer W6 and placing it within a cassette within the 
cassette placement module 12. Thus, all of the wafers have been retrieved 
from a cassette, purged, preprocessed, processed, post processed and 
returned back to the originating cassette slot. 
For more than six wafers, it is obvious that the steps in the 15.sup.th 
through 19.sup.th periods must be repeated. In every repeat cycle of steps 
in the 15.sup.th through 19.sup.th periods, all the wafer numbers are 
increased by one. In FIG. 11 there is shown a top view of a wafer transfer 
chamber 50 having three stations which are a load lock station 90, a 
preprocessing station 92 and a wand station 94. As can be seen in FIG. 12, 
a load lock 60 is positioned above the load lock station 90 that has an 
elevator lift mechanism 37 associated with the load lock station 90. 
Similarly, the preprocessing station 92 includes a gate valve 60a. 
Associated with the gate valve 60a is an elevator mechanism 22a. 
Additionally, the wand station 94 is situated to interface to the gate 
valve 62 which is associated with an elevator 23. 
As seen in FIGS. 11 and 12, the different positions on the wafer handler 
module 50 facilitates multiple processes being performed during the 
transfer of wafers through the different stations instead of preprocessing 
of post processing stations. There can be a load lock 60 located over 
station 92 (or the post processing station 96 as described in relation to 
FIG. 3). This is in addition to its location at the load lock station 90. 
As discussed, whenever a wafer at the load lock station 90 is located 
within the load lock 60 the wafer can be subjected a gas purge. 
Additionally, the wafer can be subjected to an etching step while in that 
position or some other type of gas treatment. Thus, having the 
capabilities to locate processing stations or steps with the preprocessing 
station 92 or the post processing station 96 provides additional 
versatility to the practitioner of the invention. 
Although the invention provides for the raising and lowering of the wafer 
handler 80, pins 91, 93 and 95 could be raised and lowered. Thus, wafer 
handler 80 would only be required to rotate in the counterclockwise and 
clockwise directions. 
Finally, to protect the wafers during indexing of rotary handler 80, the 
wafers are located on wafer holder 21a. The wafer holder is supported by 
the pins 91, 93 and 95. The wafer, and the end handler 80 is positioned 
under both the wafer holder 21a and the wafer effector 84 lifts both to 
index them to the next station. In all other aspects, the rotary load lock 
50 operates in the same manner as was previously described except that 
instead of wafers on the locations 90, 92, 94 and 96, now there are wafer 
holders and wafers on those locations. The wafer holders support the 
wafers in the handler module, but are not transferred in the process 
chamber or cassette. 
FIG. 13 is an isometric drawing of the wafer holder 21a. It is a light 
weight metal and formed with three arms 43, 45 and 47 rather than a solid 
plate so as to be lighter than the plate 21 described in the previous 
embodiment. Additional weight reduction is provided by opening 48 to 
support the wafer. At the end of each arm is a quartz wafer support 44. 
The quartz wafer support has a formed recess to match the outer 
circumference of the wafer so that only the backside and outer edge of the 
wafer is in contact with the wafer support 44.