An apparatus platform for semiconductor device manufacturing and a method of operation thereof
By introducing multiple transfer cavities and buffer cavities into the equipment platform, synchronous and independent transfer of the transfer cavities is achieved, solving the problem of insufficient wafer processing output capability in traditional equipment platforms, and in particular improving the wafer processing efficiency of short-time process technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI ANBANG SEMI EQUIPMENT CO LTD
- Filing Date
- 2021-12-24
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional cluster-type equipment platforms have insufficient wafer processing output capabilities in medium and short-duration process technologies, especially the transfer rate of the transfer cavity has become a bottleneck.
The design employs multiple transfer cavity groups and buffer cavity groups. Each transfer cavity group includes multiple transfer cavities, and each buffer cavity group includes multiple buffer cavities. The transfer cavities can synchronously and independently transfer wafers between corresponding buffer cavities and process cavities, thereby improving the output capability of the equipment platform.
It improves the wafer processing output capability of the equipment platform, especially the wafer processing efficiency of short-time process technology.
Smart Images
Figure CN114284190B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing, and more particularly to an equipment platform for manufacturing semiconductor devices and its operating method. Background Technology
[0002] In a typical plasma etching process, different combinations of process gases are excited by radio frequency (RF) to form plasma in a radio frequency (RF) environment. The resulting plasma, under the influence of the electric fields of the upper and lower electrodes of the etching chamber, physically bombards and chemically reacts with the wafer surface, completing the processing of the designed patterns and key processes on the wafer surface. Typical etching chambers include capacitively coupled cavities (CCP) and inductively coupled cavities (ICP).
[0003] Traditional cluster-type equipment platforms for semiconductor device manufacturing include: a front-end module (including an atmospheric transfer robot) for wafer transfer under atmospheric conditions, a transfer cavity (including a vacuum transfer robot) for wafer transfer under vacuum conditions, several buffer cavities between the front-end module and the transfer cavity, and several wafer processing cavities arranged in a cluster around the transfer cavity. Cluster-type equipment platforms for semiconductor device manufacturing also include some auxiliary modules, such as isolation valve groups between the buffer cavities and the front-end module, between the buffer cavities and the transfer cavities, and between the transfer cavities and the wafer processing cavities.
[0004] Typically, the output capacity of the entire equipment platform for wafer processing is determined by the following factors: 1. The wafer transfer rate V1 of the equipment front-end module, which includes the process of an atmospheric transfer robot transferring unreacted wafers from the wafer cassette to the buffer chamber and the process of transferring reacted wafers from the buffer chamber back to the wafer cassette; 2. The buffer rate V2 of the buffer chamber, which is the speed at which the buffer chamber switches between atmospheric and vacuum; 3. The wafer transfer rate V3 of the transfer chamber, which includes the process of a vacuum transfer robot transferring unreacted wafers from the buffer chamber to the wafer processing chamber and the process of transferring reacted wafers from the wafer processing chamber back to the buffer chamber; 4. The wafer processing rate V4 within the processing chamber.
[0005] Typically, V2 >> V1 > V3. Factors 1, 3, and 4 are operated synchronously as a single entity. The impact of different wafer processing rates on the output capability of the entire equipment platform is as follows: For longer process times, the wafer processing rate is much lower than the transmission rate of the transport system, and the output capability of the entire equipment platform for wafer processing is approximately: P ≈ V4; For medium-duration process times, the output capability of the equipment platform is approximately: P ≈ Min[V1, V3, V4] = Min[V3, V4]; For very short process times, the output capability of the equipment platform is approximately: P ≈ V3.
[0006] Clearly, for medium- and short-duration process technologies, the bottleneck of the entire equipment platform's wafer processing output capability lies in the wafer transfer rate of the transfer chamber. The traditional cluster structure of a single transfer chamber for multiple wafer processing chambers is no longer sufficient to meet the equipment platform's wafer processing output capability for short-duration process technologies. Summary of the Invention
[0007] The problem solved by this invention is to provide an equipment platform and its working method for semiconductor device manufacturing, thereby improving the output capability of the equipment platform.
[0008] To address the aforementioned technical problems, the present invention provides an equipment platform for semiconductor device manufacturing, comprising: a transfer cavity group including multiple transfer cavities; a buffer cavity group and a process cavity group arranged around the sides of the transfer cavity group, the process cavity group including multiple process cavities arranged around a portion of the sides of the transfer cavity group, and the buffer cavity group including multiple buffer cavities, the buffer cavities being located on the sides of the transfer cavity group.
[0009] Optionally, the transmission cavity group includes a first transmission cavity to an Nth transmission cavity, where N is an integer greater than or equal to 2; the buffer cavity group includes a first buffer cavity to an Nth buffer cavity, where the jth buffer cavity is located on the side of the jth transmission cavity, and j is an integer greater than or equal to 1 and less than or equal to N.
[0010] Optionally, the conveying cavity group and the buffer cavity group are arranged along a first direction; the first conveying cavity to the Nth conveying cavity are arranged along a second direction; the first buffer cavity to the Nth buffer cavity are arranged along a second direction; the second direction is perpendicular to the first direction.
[0011] Optionally, the transfer cavity group has a first side and a second side opposite to each other along a first direction, and a third side and a fourth side opposite to each other along a second direction; the plurality of process cavities include a first process cavity to a N+2th process cavity; the buffer cavity group is located on the first side of the transfer cavity group, the first process cavity to the Nth process cavity are located on the second side of the transfer cavity group, the N+1th process cavity is located on the third side of the transfer cavity group, and the N+2th process cavity is located on the fourth side of the transfer cavity group; the jth transfer cavity is located between the jth buffer cavity and the jth process cavity.
[0012] Optional, N equals 2.
[0013] Optionally, it may also include: a first transfer robot located in each of the transfer cavities.
[0014] Optionally, it may also include: a device front-end module, which is located on the side of the buffer cavity group facing away from the transmission cavity group.
[0015] Optionally, the device front-end module includes: a device front-end module body; a second transfer robot located in the front-end module body; a wafer cassette carrier located on the side of the front-end module body facing away from the buffer cavity group; and a wafer cassette group located on the wafer cassette carrier.
[0016] Optionally, the buffer cavity includes: a buffer cavity body; a first isolation door located between the buffer cavity body and the front end mold of the equipment; a second isolation door located between the buffer cavity body and the conveying cavity; the process cavity includes a process cavity body and a third isolation door located between the process cavity body and the conveying cavity.
[0017] The present invention also provides a method of operating an equipment platform for semiconductor device manufacturing, comprising: synchronously and independently transferring several pairs of wafers between corresponding buffer cavities and process cavities using the plurality of transfer cavities.
[0018] Optionally, the transfer cavity group includes a first transfer cavity to an Nth transfer cavity, where N is an integer greater than or equal to 2; the buffer cavity group includes a first buffer cavity to an Nth buffer cavity, where the jth buffer cavity is located on the side of the jth transfer cavity, and j is an integer greater than or equal to 1 and less than or equal to N; the plurality of wafer pairs include a first pair of wafers to an Nth pair of wafers; the step of synchronously and independently transferring wafers between corresponding buffer cavities and process cavities using the plurality of transfer cavities includes: transferring the jth pair of wafers from the jth buffer cavity to the jth process cavity using the jth transfer cavity; after transferring the jth pair of wafers from the jth buffer cavity to the jth process cavity using the jth transfer cavity, performing process processing on the jth pair of wafers in the jth process cavity; after performing process processing on the jth pair of wafers in the jth process cavity, transferring the jth pair of wafers from the jth process cavity to the jth buffer cavity using the jth transfer cavity.
[0019] Optionally, the equipment platform further includes: an equipment front-end module, the equipment front-end module being located on the side of the buffer cavity group facing away from the transfer cavity group; the working method further includes: before transferring the j-th pair of wafers from the j-th buffer cavity to the j-th process cavity using the j-th transfer cavity, transferring the j-th pair of wafers from the equipment front-end module to the j-th buffer cavity; after transferring the j-th pair of wafers from the j-th process cavity to the j-th buffer cavity using the j-th transfer cavity, transferring the j-th pair of wafers from the j-th buffer cavity to the equipment front-end module.
[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0021] In the equipment platform for semiconductor device manufacturing provided by the technical solution of the present invention, the transfer cavity group includes multiple transfer cavities, and the buffer cavity group includes multiple buffer cavities. The buffer cavities are respectively located on the side of the transfer cavity. The multiple transfer cavities can synchronously and independently realize the transfer of wafers between the corresponding buffer cavity and the process cavity, thereby improving the output capability of the equipment platform, especially the output capability of wafers for short-time process. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of an equipment platform for semiconductor device manufacturing according to an embodiment of the present invention. Detailed Implementation
[0023] One embodiment of the present invention provides an equipment platform for semiconductor device manufacturing, see reference. Figure 1 The system includes: a conveying cavity group comprising multiple conveying cavities; a buffer cavity group and a process cavity group arranged around the sides of the conveying cavity group, the process cavity group comprising multiple process cavities arranged around a portion of the sides of the conveying cavity group; and the buffer cavity group comprising multiple buffer cavities, each located on a side of the conveying cavity group. The equipment platform also includes: a front-end module 10 located on the side of the buffer cavity group facing away from the conveying cavity group.
[0024] The transmission cavity group includes a first transmission cavity to an Nth transmission cavity, where N is an integer greater than or equal to 2; the buffer cavity group includes a first buffer cavity to an Nth buffer cavity, where the jth buffer cavity is located on the side of the jth transmission cavity, and j is an integer greater than or equal to 1 and less than or equal to N.
[0025] The conveying cavity group and the buffer cavity group are arranged along the first direction X; the first conveying cavity to the Nth conveying cavity are arranged along the second direction Y; the first buffer cavity to the Nth buffer cavity are arranged along the second direction Y; the second direction Y is perpendicular to the first direction X.
[0026] The transfer cavity group has a first side and a second side opposite to each other along a first direction X, and a third side and a fourth side opposite to each other along a second direction; the plurality of process cavities include a first process cavity to a N+2th process cavity; the buffer cavity group is located on the first side of the transfer cavity group, the first process cavity to the Nth process cavity are located on the second side of the transfer cavity group, the N+1th process cavity is located on the third side of the transfer cavity group, and the N+2th process cavity is located on the fourth side of the transfer cavity group; the jth transfer cavity is located between the jth buffer cavity and the jth process cavity.
[0027] In this embodiment, please refer to Figure 1 N equals 2. The conveying cavity group includes a first conveying cavity 231 and a second conveying cavity 232; the buffer cavity group includes a first buffer cavity 21 and a second buffer cavity 22. The plurality of process cavities include a first process cavity, a second process cavity, a third process cavity, and a fourth process cavity. The first buffer cavity 21 and the second buffer cavity 22 are located on the first side of the conveying cavity group, the first process cavity and the second process cavity are located on the second side of the conveying cavity group, the third process cavity is located on the third side of the conveying cavity group, and the fourth process cavity is located on the fourth side of the conveying cavity group. The first conveying cavity 231 is located between the first buffer cavity 21 and the first process cavity, and the second conveying cavity 232 is located between the second buffer cavity 22 and the second process cavity.
[0028] It should be noted that in other embodiments, N can also be an integer greater than or equal to 3, and the number of N is not limited.
[0029] In this embodiment, the first transmission cavity to the Nth transmission cavity are connected; specifically, the first transmission cavity 231 and the second transmission cavity 232 are connected. In other embodiments, the first transmission cavity to the Nth transmission cavity are separate from each other.
[0030] In this embodiment, the first buffer cavity to the Nth buffer cavity are independent of each other. Any two of the first buffer cavities to the Nth buffer cavity are not connected.
[0031] The buffer chamber includes: a buffer chamber body; a first isolation door located between the buffer chamber body and the front-end mold of the equipment; and a second isolation door located between the buffer chamber body and the conveying chamber. Specifically, the first buffer chamber 21 includes: a first buffer chamber body 212; a first isolation door 211 located between the first buffer chamber body 212 and the front-end mold of the equipment 10; and a second isolation door 213 located between the first buffer chamber body 212 and the first conveying chamber 231. The second buffer chamber 22 includes: a second buffer chamber body 222; a first isolation door 221 located between the second buffer chamber body 222 and the front-end mold of the equipment 10; and a second isolation door 223 located between the second buffer chamber body 222 and the second conveying chamber 232.
[0032] The first isolation door is an atmospheric isolation door. The second isolation door is a vacuum isolation door.
[0033] The process chamber includes a process chamber body and a third isolation door located between the process chamber body and the transfer chamber. Specifically, the first process chamber includes: a first process chamber body 32; and a third isolation door 252 located between the first process chamber body 32 and the first transfer chamber 231. The second process chamber includes: a second process chamber body 33; and a third isolation door 253 located between the second process chamber body 33 and the second transfer chamber 232. The third process chamber includes: a third process chamber body 31; and a third isolation door 251 located between the third process chamber body 31 and the first transfer chamber 231. The fourth process chamber includes: a fourth process chamber body 34; and a third isolation door 254 located between the fourth process chamber body 34 and the second transfer chamber 232. The third isolation door is a vacuum isolation door.
[0034] In this embodiment, the device platform further includes: a first transfer robot located in each of the transfer cavities. A first transfer robot 241 is located in the first transfer cavity 231. A first transfer robot 242 is located in the second transfer cavity 232. The first to Nth transfer cavities are adapted to transfer wafers under vacuum conditions. The first transfer robot is adapted to transfer wafers under vacuum conditions.
[0035] The device front-end module 10 includes: a device front-end module body 11; a second transmission robot 12 located in the front-end module body 11; a wafer cassette carrier 13 located on the side of the front-end module body 11 facing away from the buffer cavity group; and a wafer cassette group located on the wafer cassette carrier 13.
[0036] The wafer cassette group includes a first wafer cassette to an Mth wafer cassette, where M is an integer greater than or equal to 2. In this embodiment, M is greater than N. This embodiment uses M equal to 4 as an example for illustration. The wafer cassette group includes a first wafer cassette 141, a second wafer cassette 142, a third wafer cassette 143, and a fourth wafer cassette 144. In this embodiment, the first wafer cassette to the Mth wafer cassette are arranged along the second direction Y.
[0037] The device front-end module 10 is adapted to transport wafers in an atmospheric environment. The second transport robot 12 transports wafers in an atmospheric environment.
[0038] In this embodiment, the transfer cavity group includes multiple transfer cavities, and the buffer cavity group includes multiple buffer cavities. The buffer cavities are located on the side of the transfer cavity group. The multiple transfer cavities can synchronously and independently realize the transfer of wafers between the corresponding buffer cavities and process cavities, which improves the output capability of the equipment platform, especially the output capability of wafers for short-time process processes.
[0039] Accordingly, this embodiment also provides a method for operating the above-mentioned equipment platform for semiconductor device manufacturing, including: synchronously and independently transferring several pairs of wafers between corresponding buffer cavities and process cavities using the multiple transfer cavities.
[0040] The transfer cavity group includes a first transfer cavity to an Nth transfer cavity, where N is an integer greater than or equal to 2; the buffer cavity group includes a first buffer cavity to an Nth buffer cavity, where the jth buffer cavity is located on the side of the jth transfer cavity, and j is an integer greater than or equal to 1 and less than or equal to N; the plurality of wafer pairs include a first pair of wafers to an Nth pair of wafers; the step of synchronously and independently transferring wafer pairs between corresponding buffer cavities and process cavities using the plurality of transfer cavities includes: transferring the jth pair of wafers from the jth buffer cavity to the jth process cavity using the jth transfer cavity; after transferring the jth pair of wafers from the jth buffer cavity to the jth process cavity using the jth transfer cavity, performing process processing on the jth pair of wafers in the jth process cavity; after performing process processing on the jth pair of wafers in the jth process cavity, transferring the jth pair of wafers from the jth process cavity to the jth buffer cavity using the jth transfer cavity.
[0041] Specifically, when N equals 2, the first transfer robot 241 in the first transfer cavity 231 transfers the first pair of wafers from the first buffer cavity to the first process cavity. Then, the first pair of wafers undergoes processing in the first process cavity. Afterwards, the first transfer robot 241 in the first transfer cavity 231 transfers the first pair of wafers from the first process cavity to the first buffer cavity 21. Similarly, the first transfer robot 241 in the first transfer cavity 231 transfers the third pair of wafers from the first buffer cavity to the third process cavity. Then, the third pair of wafers undergoes processing in the third process cavity. Finally, the first transfer robot 241 in the first transfer cavity 231 transfers the third pair of wafers from the third process cavity to the first buffer cavity. In step 21, the first transfer robot 242 in the second transfer cavity 232 transfers the second pair of wafers from the second buffer cavity 22 to the second process cavity. The second pair of wafers then undergoes processing in the second process cavity. Afterwards, the first transfer robot 242 in the second transfer cavity 232 transfers the second pair of wafers from the second process cavity to the second buffer cavity 22. The first transfer robot 242 in the second transfer cavity 232 transfers the fourth pair of wafers from the second buffer cavity 22 to the fourth process cavity. The fourth pair of wafers then undergoes processing in the fourth process cavity. Afterwards, the first transfer robot 242 in the second transfer cavity 232 transfers the fourth pair of wafers from the fourth process cavity to the second buffer cavity 22.
[0042] The equipment platform further includes: an equipment front-end module, which is located on the side of the buffer cavity group facing away from the transfer cavity group; the working method further includes: before transferring the j-th pair of wafers from the j-th buffer cavity to the j-th process cavity using the j-th transfer cavity, transferring the j-th pair of wafers from the equipment front-end module to the j-th buffer cavity, specifically, using the second transfer robot 12 to transfer the j-th pair of wafers from the wafer cassette to the j-th buffer cavity; after transferring the j-th pair of wafers from the j-th process cavity to the j-th buffer cavity using the j-th transfer cavity, transferring the j-th pair of wafers from the j-th buffer cavity to the equipment front-end module, specifically, using the second transfer robot 12 to transfer the j-th pair of wafers from the j-th buffer cavity to the wafer cassette.
[0043] Specifically, when N equals 2, before the first pair of wafers is transferred from the first buffer cavity to the first process cavity by the first transfer robot 241 in the first transfer cavity 231, the first pair of wafers is transferred from the equipment front-end module to the first buffer cavity 21; before the second pair of wafers is transferred from the second buffer cavity to the second process cavity by the first transfer robot 242 in the second transfer cavity 232, the second pair of wafers is transferred from the equipment front-end module to the second buffer cavity 22; after the first pair of wafers is transferred from the first process cavity to the first buffer cavity 21 by the first transfer robot 241 in the first transfer cavity 231, the first pair of wafers is transferred from the first buffer cavity 21 to the equipment front-end module 10; after the second pair of wafers is transferred from the second process cavity to the second buffer cavity 22 by the first transfer robot 242 in the second transfer cavity 232, the second pair of wafers is transferred from the second buffer cavity 22 to the equipment front-end module 10.
[0044] It should be noted that before the j-th pair of wafers is transferred from the front-end module of the equipment to the j-th buffer cavity, the main body of the j-th buffer cavity needs to be vented. After the venting of the main body of the j-th buffer cavity, the first isolation door of the j-th buffer cavity is opened. After the first isolation door of the j-th buffer cavity is opened, the j-th pair of wafers is transferred from the front-end module of the equipment to the j-th buffer cavity.
[0045] It should be noted that after the j-th pair of wafers is transferred from the front-end module of the equipment to the j-th buffer cavity, and before the j-th pair of wafers is transferred from the j-th buffer cavity to the j-th process cavity, the j-th buffer cavity body needs to be evacuated. After the j-th buffer cavity body is evacuated, the second isolation door of the j-th buffer cavity is opened. After the second isolation door of the j-th buffer cavity is opened, the j-th pair of wafers is transferred from the j-th buffer cavity to the j-th process cavity.
[0046] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A cluster-type equipment platform for semiconductor device manufacturing, characterized in that, include: A transfer cavity group, wherein the transfer cavity group includes multiple transfer cavities; A buffer cavity group and a process cavity group are arranged around the side of the conveying cavity group. The process cavity group includes multiple process cavities arranged around a portion of the side of the conveying cavity group. The buffer cavity group includes multiple buffer cavities, which are respectively located on the side of the conveying cavity group. The conveying cavity group includes a first conveying cavity to an Nth conveying cavity, where N is an integer greater than or equal to 2; the buffer cavity group includes a first buffer cavity to an Nth buffer cavity, where the jth buffer cavity is located on the side of the jth conveying cavity, and j is an integer greater than or equal to 1 and less than or equal to N. The conveying cavity group and the buffer cavity group are arranged along a first direction; the first conveying cavity to the Nth conveying cavity are arranged along a second direction; the first buffer cavity to the Nth buffer cavity are arranged along a second direction; the second direction is perpendicular to the first direction; The transfer cavity group has a first side and a second side opposite to each other along a first direction, and a third side and a fourth side opposite to each other along a second direction; the plurality of process cavities include a first process cavity to a N+2th process cavity; The buffer cavity group is located on the first side of the transfer cavity group; the first process cavity to the Nth process cavity are located on the second side of the transfer cavity group; the N+1th process cavity is located on the third side of the transfer cavity group; the N+2th process cavity is located on the fourth side of the transfer cavity group; the jth transfer cavity is located between the jth buffer cavity and the jth process cavity. The first buffer cavity, the first transfer cavity, and the first process cavity constitute the independent transfer channels for the first pair of wafers; The first buffer cavity, the first transfer cavity, and the N+1th process cavity constitute the independent transfer channel for the N+1th pair of wafers. The Nth buffer cavity, the Nth transfer cavity, and the Nth process cavity constitute the independent transfer channel for the Nth pair of wafers; The Nth buffer cavity, the Nth transfer cavity, and the N+2th process cavity constitute the N+2th independent transfer channel for wafers; In this process, multiple transfer cavities are used to synchronously and independently transfer several pairs of wafers between corresponding buffer cavities and process cavities.
2. The cluster-type equipment platform for semiconductor device manufacturing according to claim 1, characterized in that, N equals 2.
3. The cluster-type equipment platform for semiconductor device manufacturing according to claim 1, characterized in that, Also includes: The first transfer robot is located in the transfer cavity.
4. The cluster-type equipment platform for semiconductor device manufacturing according to claim 1, characterized in that, Also includes: The device front-end module is located on the side of the buffer cavity group that faces away from the transmission cavity group.
5. The cluster-type equipment platform for semiconductor device manufacturing according to claim 4, characterized in that, The device front-end module includes: a device front-end module body; a second transmission robot located in the front-end module body; a wafer cassette carrier located on the side of the front-end module body facing away from the buffer cavity group; and a wafer cassette group located on the wafer cassette carrier.
6. The cluster-type equipment platform for semiconductor device manufacturing according to claim 4, characterized in that, The buffer cavity includes: a buffer cavity body; a first isolation door located between the buffer cavity body and the front end mold of the equipment; and a second isolation door located between the buffer cavity body and the conveying cavity. The process cavity includes a process cavity body and a third isolation door located between the process cavity body and the transfer cavity.
7. A method of operating a cluster-type equipment platform for semiconductor device manufacturing as described in any one of claims 1 to 6, characterized in that, include: The multiple transfer cavities are used to synchronously and independently transfer several pairs of wafers between corresponding buffer cavities and process cavities. The several pairs of wafers include the first pair of wafers to the Nth pair of wafers.
8. The method of operating the cluster-type equipment platform for semiconductor device manufacturing according to claim 7, characterized in that, The steps of synchronously and independently transferring wafers between corresponding buffer cavities and process cavities using the multiple transfer cavities include: transferring the j-th pair of wafers from the j-th buffer cavity to the j-th process cavity using the j-th transfer cavity; after transferring the j-th pair of wafers from the j-th buffer cavity to the j-th process cavity using the j-th transfer cavity, performing process processing on the j-th pair of wafers in the j-th process cavity; and after performing process processing on the j-th pair of wafers in the j-th process cavity, transferring the j-th pair of wafers from the j-th process cavity to the j-th buffer cavity using the j-th transfer cavity.
9. The method of operating the cluster-type equipment platform for semiconductor device manufacturing according to claim 8, characterized in that, The equipment platform further includes: an equipment front-end module, which is located on the side of the buffer cavity group facing away from the transmission cavity group; The working method further includes: before transferring the j-th pair of wafers from the j-th buffer cavity to the j-th process cavity using the j-th transfer cavity, transferring the j-th pair of wafers from the equipment front-end module to the j-th buffer cavity; after transferring the j-th pair of wafers from the j-th process cavity to the j-th buffer cavity using the j-th transfer cavity, transferring the j-th pair of wafers from the j-th buffer cavity to the equipment front-end module.