JP2003243480A - Automatic conveying system and method for semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic conveying system and method for a semiconductor wafer which can some energy consumed for ensuring a downflow and illuminance in a clean room, and further which is easy to ensure moving routes of facilities with large sizes. <P>SOLUTION: A plurality of bays (BAY 1 to 4) as moving areas between wafer processes are arranged in a clean room CR, and a plurality of semiconductor manufacturing apparatuses Mn1, Mn2, Mn3, etc., (any of n=1 to 4) are arranged. Stockers S1 to S8 are arranged at each of both side parts of the bays BAY 1 to 4, and is stood by a plurality of wafer cassettes OWC. Conveying mechanism CONV of the wafer cassettes OWC are disposed between a plurality of the stockers S1 to S8 to constitute mutual conveying routes between the plurality of bays BAY 1 to 4. It is desirable that the conveying mechanism CONV has a structure that a conveying wafer is not directly affected by a downflow. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor device manufacturing, and more particularly to a semiconductor wafer automatic transfer system and a wafer transfer method used in a semiconductor manufacturing line in a clean room.

[0002]

2. Description of the Related Art A clean room is an essential work space in a semiconductor device manufacturing line. In a clean room, a filter unit with a fan mounted on the ceiling controls the air flow (downflow) from the ceiling to the floor. As a result, the dust in the air is removed and the cleanliness level (cleanliness class) is regulated. Various wafer processes such as a lithography process, a film forming process, an etching process, a cleaning process, and an inspection process are processed by equipment of a semiconductor manufacturing apparatus in a clean room.

FIG. 5 is a schematic diagram showing a main part of a conventional automatic wafer transfer system in a clean room. The movement between the wafer processes in the clean room CR is automatic transfer by the wafer cassette WC, and a method of suspending rails from the ceiling is adopted as the method. That is, the automated guided vehicle VC carrying the wafer cassette WC moves along the rail RL suspended from the ceiling. Further, a filter unit FFU with a fan is mounted on the ceiling. As a result, the downflow from the top to the bottom removes dust in the air, and the atmosphere in the clean room CR is controlled to a prescribed cleanliness level (cleanliness class).

A plurality of wafer cassettes WC can be put on standby in a storage box called a stocker (S). The stocker S is arranged according to a wafer inter-process moving area BAY called a bay in which the front surface of the semiconductor manufacturing apparatus is lined up. The wafer cassette WC on the rail RL is stored in a predetermined stocker S by the transfer robot RB. After that, it is transferred to the automatic guided vehicle AGV, moved to the carry-in entrance of the target semiconductor manufacturing apparatus MC, and loaded (carried-in). After the processing, the wafer cassette is unloaded (removed) and the wafer cassette is transferred to the AGV again. This movement area BA between wafer processes
The unmanned guided vehicle AGV is also used for moving the wafer process by another semiconductor manufacturing apparatus provided in Y.

Moving area between other wafer processes (not shown)
The wafer is moved to the wafer cassette W as described above.
C is transferred from the automatic guided vehicle AGV to the stocker S to the automatic guided vehicle VC on the rail RL. Then, although not shown, the wafer cassette is moved to the front of the target semiconductor manufacturing apparatus via a stocker and an unmanned transportation vehicle that belong to a predetermined movement area between wafer processes. After the processing, the wafer cassette is stored in a predetermined stocker again using the automatic guided vehicle.

[0006]

According to the above construction, the rail is installed near the ceiling in the clean room, and the mechanism for moving the wafer cassette by the automatic carrier is arranged. Such equipment has the following problems. The downflow in the clean room is affected not a little, and a considerable amount of air is required to maintain the specified cleanliness. In addition, since the illuminance near the rail is reduced, preparation of a considerable lighting fixture also causes an increase in energy consumption. Further, there is a possibility that a movement route of equipment having a large height, such as replacement and arrangement of semiconductor manufacturing equipment, cannot be secured.

The present invention has been made in consideration of the above-mentioned circumstances, and a downflow in a clean room,
An object of the present invention is to provide an automatic transfer system for a semiconductor wafer and an automatic transfer method for the semiconductor wafer, which can save energy spent for securing the illuminance and can easily secure a movement path of equipment having a large height.

[0008]

According to another aspect of the present invention, there is provided an automatic transfer system for semiconductor wafers, wherein a plurality of semiconductor manufacturing apparatuses are lined up and a plurality of transfer areas between wafer processes are arranged, and a plurality of wafer cassettes are on standby. The stocker to be moved is located in a clean room arranged at a plurality of locations according to the inter-wafer-process moving area, and an automatic transfer mechanism for the wafer cassette is provided between the plurality of stockers. It is characterized in that it constitutes a transport path of.

A semiconductor wafer automatic transfer system as a more preferred embodiment of [claim 2] according to the present invention is:
A plurality of semiconductor manufacturing apparatuses are arranged in a clean room, and a plurality of semiconductor manufacturing apparatuses are lined up between the wafer steps. An unmanned transfer vehicle for transferring a wafer cassette in the wafer steps movement area and a plurality of wafers are arranged according to the wafer steps movement area. A stocker that is provided to hold a plurality of wafer cassettes on standby, and a transfer mechanism for the wafer cassettes provided between the stockers and between the plurality of stockers are provided.

In the semiconductor wafer automatic transfer system according to the present invention as set forth in each of the above claims, the transfer path between the plurality of wafer process transfer areas is realized by the transfer mechanism of the stockers. Undesirable effects on cleanliness, illuminance, equipment, etc., such as a transport mechanism using rails suspended from the ceiling are reduced.

An automatic transfer system for semiconductor wafers according to [Claim 3] according to the present invention is related to [Claim 1] or [Claim 2]. The transfer mechanism is for transferring a wafer cassette provided in the stocker. The robot section and the stocker are connected to each other.

An automatic transfer system for semiconductor wafers according to [Claim 4] according to the present invention relates to [Claim 1] or [Claim 2], wherein the transfer mechanism is for transferring a wafer cassette provided in the stocker. The robot unit and the stocker are connected to each other, and the conveyor unit has a predetermined height from the level of the inter-wafer-process moving area and includes a disposition.

An automatic transfer system for semiconductor wafers according to [Claim 5] according to the present invention is related to [Claim 1] or [Claim 2]. The transfer mechanism is for transferring a wafer cassette provided in the stocker. The robot unit and the stocker are connected to each other, and the conveyor unit is covered with a protection member so that the wafer cassette is not exposed to the clean room atmosphere.

An automatic transfer system for semiconductor wafers according to [Claim 6] according to the present invention relates to any one of [Claim 1] to [Claim 5], and the clean room has different cleanliness depending on locations. It is characterized in that it is configured.

An automatic transfer system for semiconductor wafers according to [Claim 7] of the present invention relates to any one of [Claim 1] to [Claim 6]. In the wafer cassette, the wafer is directly exposed to the clean room atmosphere. It is characterized by being a pod with an openable door.

According to an eighth aspect of the present invention, there is provided a semiconductor wafer automatic transfer method, wherein a plurality of wafer manufacturing process moving areas in which a plurality of semiconductor manufacturing apparatuses are arranged are arranged, and a wafer cassette is arranged in accordance with the wafer manufacturing process moving area. In a clean room in which a plurality of stockers for holding a plurality of wafers are provided, a transfer mechanism for the wafer cassette is provided between the stockers and is used for moving a semiconductor wafer between the plurality of wafer process moving areas. And

According to the above-described semiconductor wafer automatic transfer method of the present invention, the transfer path between the plurality of wafer process transfer areas is realized by the transfer mechanism of the stockers. It is possible to eliminate the transport mechanism by rails that are hung from the ceiling.

An automatic transfer method for semiconductor wafers according to [Claim 9] according to the present invention relates to [Claim 8], wherein a wafer cassette before and after wafer processing by an arbitrary semiconductor manufacturing apparatus is set in the wafer inter-process moving area. It is characterized in that an automated guided vehicle for transportation is used.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram showing an automatic transfer system for semiconductor wafers according to a first embodiment of the present invention. The inside of the clean room CR is managed to a cleanliness level (cleanliness class) defined by downflow. In this clean room CR, a plurality of bays (BAY1 to 4), which are movement areas between wafer processes, are arranged. A plurality of semiconductor manufacturing apparatuses Mn1, Mn2, Mn3 ... (N = 1 to 4) are arranged in each of the bays BAY1 to BAY4 with the front side having the wafer carry-in port facing. The bay (BAY1 to 4) areas are separated from other areas by the partition 11, and the level of cleanliness is set high.

The stockers S1 to S8 are arranged in bays BAY1 to BAY4.
A plurality of wafer cassettes OWC are arranged on both sides of the wafer cassette OWC. The automated guided vehicle AGV has a bay (BAY1) to which it belongs.
4), the wafer cassette OWC is transported between the stocker (S1 to S8) and the semiconductor manufacturing apparatus (Mn1, Mn2, Mn3 ... (N = 1 to 4)). That is, the movement of wafers before and after processing by the semiconductor manufacturing apparatus installed in one predetermined bay is achieved by the AGV. In addition, adjacent bays (between BAY1-4, BA
Between Y2 and 3), that is, S1, S2,
The automatic guided vehicle AGV is also used for transporting the wafer cassette OWC between S7 and S8 and between S3, S4, S5 and S6.

In this embodiment, the transfer mechanism CONV of the wafer cassette OWC is connected between the plurality of stockers S1 to S8.
Are provided to form a transport path between the plurality of bays BAY1 to BAY4. The transfer mechanism CONV preferably has a structure in which the transferred wafer is not directly affected by the downflow.

In addition, between stockers S2-S7, between S3-S6
The transport mechanism CONV between may be omitted.
In addition, the stockers S1-S2, S3-S4, and S5-S.
The transport mechanism CONV between 6 and S7-S8 may be added.

FIG. 2 is a schematic view showing the structure of the transport mechanism CONV between the stockers, which is a part of FIG. Here, the configuration of the transport mechanism CONV between the stockers S2 and S3 is representatively shown, but the same applies to other stockers. For example, a wafer cassette OW provided in each of the stockers S2 and S3
The configuration of the transfer robot 21 of C and the slide conveyor 22 between the stockers is shown. The inside of each stocker is also cleaned by generating downflow (broken line arrow) with clean air.

The robot 21 is involved in the delivery of the wafer cassette to and from the AGV, the delivery of the wafer cassette at a predetermined storage position in the stocker, and the delivery of the wafer cassette in the slide conveyor 22. There may be a plurality of robots 21. It would be even better if a configuration such as division of labor could be realized in this way.

The slide conveyor 22 is covered with a protective cover 23 so as not to be affected by dust in the clean room outside the stocker. The transport mechanism CONV is passed to a position of a predetermined height between the stockers S2-S3.
The predetermined height means a sufficient height that does not hinder the movement or replacement work of the equipment of the semiconductor manufacturing apparatus.

An example of a wafer automatic transfer method will be described with reference to FIGS. The wafer cassette OWC is transferred from a predetermined stocker S1 to the automated guided vehicle AGV by the transfer robot 21, is moved to the carry-in port of the target semiconductor manufacturing apparatus M12 in the bay BAY1, and is loaded (carried-in). After the processing, the wafer cassette is unloaded (removed) and the wafer cassette is transferred to the AGV again. The unmanned guided vehicle AGV is also used for moving the wafer process by another semiconductor manufacturing apparatus provided in the bay BAY1.

After the predetermined processing in each semiconductor manufacturing apparatus provided in the bay BAY1, the wafer cassette OWC enters the stocker S2 and is transferred to the slide conveyor 22 by the transfer robot 21. Slide conveyor 22
Thus, the wafer cassette OWC enters the stocker S3. The wafer cassette OWC is transferred to the automated guided vehicle AGV by the transfer robot 21 in the stocker S3, and the bay BAY2.
The target semiconductor manufacturing apparatus M23 is moved to and loaded (loaded) therein. After the processing, the wafer cassette is unloaded and the wafer cassette is again unmanned AGV.
Reprinted in. The unmanned guided vehicle AGV is also used for moving the wafer process by another semiconductor manufacturing apparatus provided in the bay BAY2.

As described above, the movement area between other wafer processes, that is, the movement of wafers between BAYs is achieved by the wafer cassette OWC passing through the slide conveyor 22 between the stockers as described above. If the slide conveyors 22 and the automatic guided vehicle AGV at a plurality of locations are continuously used, it is possible to carry the wafers to the bays BAY which are not adjacent to each other and are apart from each other.

According to the configuration of the above embodiment, the transport mechanism C
By arranging the ONV, it is possible to eliminate the transfer mechanism using the rails hung from the ceiling. As a result, the influence of downflow in the clean room is also reduced, and the airflow is considerably reduced to maintain the specified cleanliness. For example, it is possible to lower the cleanliness level (cleanliness class) from the areas of the bays BAY1 to BAY4 divided by the partitions 11 (shown in FIG. 1) in the arrangement area (shaded areas) of the transport mechanism CONV that connects the stockers. is there. This can be expected to reduce the number of filter units with a fan (FFU) mounted on the ceiling. In addition, the efficiency of illuminance can be improved and energy consumption can be reduced as compared with the rail suspended from the ceiling. Further, since the transport mechanism CONV can be installed at a high position, it is possible to secure a moving path for equipment having a large height, such as replacement and arrangement of semiconductor manufacturing equipment equipment.

FIG. 3 is a schematic diagram showing an automatic transfer system for semiconductor wafers according to the second embodiment of the present invention.
The inside of the clean room CR is managed to a cleanliness level (cleanliness class) defined by downflow. In this clean room CR, a plurality of bays (BAY1 to 6) which are transfer areas between wafer processes are arranged. A plurality of semiconductor manufacturing devices Mn are provided in each of the bays BAY1 to BAY6.
1, Mn2, Mn3 ... (N = 1 to 6) are lined up with the front side having the wafer carry-in port facing. Bay (BAY1
~ 4) Areas are not separated by partitions,
The cleanliness level is the same as other areas.

Unlike the open cassette of the wafer cassette OWC used in the first embodiment, the wafer cassette PWC used in this embodiment is a pod with an opening / closing door in which the wafer is not directly exposed to the clean room atmosphere. Therefore, each of these semiconductor manufacturing devices Mn1 and Mn
2, Mn3 ... (n = 1 to 6), a mini-environment chamber 32 and a load port opener 31 with a high level of cleanliness in which a wafer transfer machine (33) is provided adjacently are provided. There is.

The stockers S1 to S12 are bays BAY1 to BAY1.
A plurality of wafer cassettes PWC are arranged on both sides of the wafer cassette 6 to wait. The automated guided vehicle AGV is
1 to 6), the wafer cassette PWC is transported between the stocker (S1 to S12) and the semiconductor manufacturing apparatus (Mn1, Mn2, Mn3 ... (N = 1 to 6)). That is, the movement of wafers before and after processing by the semiconductor manufacturing apparatus installed in one predetermined bay is achieved by the AGV.

In this embodiment, the stockers S1 to S12 are used.
Transfer mechanism CON for wafer cassette PWC between a plurality of units
V is provided to form a transport path between the plurality of bays BAY1 to BAY6. The transfer mechanism CONV is configured to transfer the wafer cassette PWC in which the wafer is not directly affected by the downflow.

The stockers S1-S2, S3-S4
, S5-S6, S7-S8, S9-S10, S
11-S12, S2-S11, S3-S10, S
The transport mechanism CONV between 4-S9 and S5-S8 may have a configuration in which a part or the front part is omitted. However, if countermeasures are taken for a route structure for rapid transport between all bays BAY1 to BAY6, the configuration may be one in which all transport systems as shown in the figure are prepared.

FIG. 4 is a schematic diagram showing the construction of the mini-environment chamber 32 and the load port opener 31 which are parts of FIG. Pod type wafer cassette P with open / close door
The WC is moved from the AGV to the load port 311 and directly connected to the mini-environment chamber 32 by the opener 312 without being exposed to the clean room atmosphere. A transfer machine 33 in the mini-environment chamber 32 loads / unloads a wafer to / from a semiconductor manufacturing apparatus.

Since the basic structure of the transfer mechanism CONV between the stockers S in this embodiment is the same as that shown in FIG. 2, the description thereof will be omitted. However, the wafer cassette PWC in which the wafer is not directly exposed to the clean room atmosphere
Therefore, the protective cover 23 of the slide conveyor 22 may be simpler or may be omitted as compared with the configuration of FIG. In addition, the flow rate of downflow can be reduced or eliminated inside the stocker.

An example of an automatic wafer transfer method will be described with reference to FIGS. 3, 4, and 2. The wafer cassette PWC is
The transfer port 21 from the predetermined stocker S1 is transferred to the automatic guided vehicle AGV by the transfer robot 21, and the load port opener 31 of the target semiconductor manufacturing apparatus M12 in the bay BAY1.
And, it is loaded (loaded) into the apparatus through the mini-environment chamber 32. After processing, it is unloaded (unloaded) and the mini-environment chamber 32 and load port opener 31
The wafer cassette PWC is transferred to the automated guided vehicle AGV again without being affected by the outside atmosphere via the. The unmanned guided vehicle AGV is also used for moving the wafer process by another semiconductor manufacturing apparatus provided in the bay BAY1.

After the completion of predetermined processing in each semiconductor manufacturing apparatus provided in the bay BAY1, the wafer cassette PWC enters the stocker S2 and is transferred to the slide conveyor 22 by the transfer robot 21. Slide conveyor 22
Thus, the wafer cassette PWC enters the stocker S3. Further, the wafer cassette PWC enters the stocker S10 by the transfer robot 21 in the stocker S3 via the slide conveyor 22 to the stocker S10. Then, the robot 21 is transferred to the automatic guided vehicle AGV by the transfer robot 21 in the stocker S10 and loaded into the apparatus via the load port opener 31 and the mini-environment chamber 32 of the target semiconductor manufacturing apparatus M53 in the bay BAY5.
To be done. After the processing, the wafer cassette PWC is transferred to the automatic guided vehicle AGV again via the mini-environment chamber 32 and the load port opener 31 without being influenced by the external atmosphere. This bay BAY5
The automated guided vehicle AGV is also used to move the wafer process by another semiconductor manufacturing apparatus provided therein.

In this way, the movement area between other wafer processes, that is, the movement of wafers between BAYs, is achieved by the wafer cassette PWC passing through the slide conveyor 22 between the stockers as described above. By using the slide conveyors 22 and the automatic guided vehicle AGV at a plurality of locations, it is possible to carry and process wafers to separate bays BAY which are not adjacent to each other.

In the configuration of the above-described embodiment as well, as with the first embodiment, by providing the transport mechanism CONV,
It is possible to eliminate the transport mechanism by rails that are hung from the ceiling. As a result, the efficiency of illuminance can be improved and the energy consumption can be reduced. Further, by using the wafer cassette PWC in which the wafer is not directly exposed to the clean room atmosphere, a considerable amount of air that maintains the specified cleanliness in the entire clean room CR is significantly reduced. This can be expected to greatly reduce the number of filter units (FFUs) with fans to be installed on the ceiling. However, since a wafer is taken out from the cassette PWC in the mini-environment chamber 32, a considerable cleanliness level is required. Further, since the transport mechanism CONV can be installed at a high position, it is possible to secure a moving path for equipment having a large height, such as replacement and arrangement of semiconductor manufacturing equipment equipment.

Incidentally, the transport path constituting the transport mechanism CONV is not limited to the configurations of the above-mentioned embodiments, and various routes are conceivable. Further, the slide mechanism 22 is included as the transfer mechanism CONV, but the present invention is not limited to this, and a bridge may be installed between the stockers to control the transfer of the wafer cassette carriage in the hollow.

[0042]

As described above, according to the present invention,
A transfer path between a plurality of bays (moving areas between wafer processes) is realized by a transfer mechanism of the stockers. This reduces undesired effects on cleanliness, illuminance, equipment, etc., such as those of a transport mechanism using rails suspended from the ceiling. As a result, it is possible to provide an automatic transfer system for a semiconductor wafer and an automatic transfer method thereof in which downflow in a clean room, energy spent for securing illuminance can be saved, and a movement route of equipment having a large height can be easily secured. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an automatic transfer system for semiconductor wafers according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a transfer mechanism between stockers, which is a part of FIG.

FIG. 3 is a schematic configuration diagram showing an automatic transfer system for semiconductor wafers according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a mini-environment chamber and a load port opener which are parts of FIG.

FIG. 5 is a schematic view showing a main part of a conventional automatic wafer transfer system in a clean room.

[Explanation of symbols]

CR ... Clean room BAY, BAY1 to 6 ... Bay (moving area between wafer processes) Mn1, Mn2, Mn3 ... (n = 1 to 6), M
C ... Semiconductor manufacturing equipment S, S1 to S12 ... Stockers OWC, PWC, WC ... Wafer cassette AGV ... Unmanned guided vehicle CONV ... Transport mechanism RL ... Rail VC ... Automatic guided vehicle FFU ... Fan-equipped filter unit 11 ... Partition 21, RB ... Delivery robot 22 ... Slide conveyor 23 ... Protective cover 31 ... Load port opener 311 ... Load port 312 ... Opener 32 ... Mini environment chamber 33 ... Wafer transfer machine

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B65G 49/07 B65G 49/07 LF term (reference) 3F022 AA08 BB09 CC02 EE05 KK20 LL12 LL31 MM04 5F031 CA02 DA01 DA08 DA17 EA14 FA01 FA05 FA07 FA09 FA11 FA12 FA14 GA51 GA58 NA02 NA10 NA16 NA18 PA30

Claims (9)

[Claims] 1. A clean room is provided in which a plurality of wafer manufacturing process moving areas in which a plurality of semiconductor manufacturing apparatuses are arranged are arranged, and a stocker for waiting a plurality of wafer cassettes is provided in a plurality of locations according to the wafer manufacturing process moving areas. An automatic transfer system for semiconductor wafers, wherein an automatic transfer mechanism for the wafer cassette is provided between the plurality of stockers to form a transfer path between the plurality of wafer process movement areas. 2. An inter-wafer process transfer area in which a plurality of semiconductor manufacturing devices are arranged in a clean room, an unmanned transfer vehicle for transferring a wafer cassette in the inter-wafer process transfer area, and the inter-wafer process transfer area. According to the above, a plurality of stockers are provided for waiting a plurality of wafer cassettes, and a transfer mechanism for the wafer cassettes provided between the stockers and for a plurality of stockers, the semiconductor wafer automatic transfer. system. 3. The automatic semiconductor wafer as claimed in claim 1, wherein the transfer mechanism is composed of a robot unit for delivering a wafer cassette provided in the stocker and a conveyor unit connecting the stockers. Transport system. 4. The transfer mechanism is composed of a robot section for delivering a wafer cassette provided in the stocker and a conveyor section connecting between the stockers, and the conveyor section has a predetermined height from the level of the inter-wafer transfer area. 1 or 2 including a transverse arrangement having
A semiconductor wafer automatic transfer system as described above. 5. The transfer mechanism is composed of a robot unit for transferring wafer cassettes provided in the stocker and a conveyor unit connecting the stockers, and the conveyor unit protects the wafer cassette from being exposed to the clean room atmosphere. 3. The automatic transfer system for semiconductor wafers according to claim 1, wherein the automatic transfer system is a structure covered with a member. 6. The automatic transfer system for semiconductor wafers according to claim 1, wherein the clean room is configured so that the cleanliness varies depending on the location. 7. The automatic transfer system for semiconductor wafers according to claim 1, wherein the wafer cassette is a pod with an opening / closing door that does not directly expose the wafer to the clean room atmosphere. 8. A clean room in which a plurality of transfer areas between wafer processes in which a plurality of semiconductor manufacturing apparatuses are lined up are arranged, and a plurality of stockers for waiting a plurality of wafer cassettes corresponding to the transfer areas between wafer processes are arranged, A method of automatically transporting a semiconductor wafer, characterized in that a transport mechanism for the wafer cassette is provided between the stockers and is used for transporting the semiconductor wafer between the plurality of wafer process transfer areas. 9. The automatic transfer of semiconductor wafers according to claim 8, wherein an unmanned transfer vehicle that transfers a wafer cassette before and after wafer processing by any of the semiconductor manufacturing apparatuses is used in the transfer area between wafer processes. Method.