CN214542176U

CN214542176U - Plasma processing equipment

Info

Publication number: CN214542176U
Application number: CN202120610226.9U
Authority: CN
Inventors: 陈国良; 刘洋; 刘孟勇; 田然; 何俊青
Original assignee: Yangtze Memory Technologies Co Ltd
Current assignee: Yangtze Memory Technologies Co Ltd
Priority date: 2021-03-25
Filing date: 2021-03-25
Publication date: 2021-10-29
Anticipated expiration: 2031-03-25

Abstract

The embodiment of the application provides a plasma processing device which comprises a plasma reaction chamber, a lifting device, a monitoring device, a controller and an adjusting device. The plasma reaction chamber is formed with a process chamber. The lifting device bears the wafer in the process chamber and drives the wafer to ascend or descend. The monitoring device is positioned in the process chamber and is configured to monitor a positional deviation of the wafer in the process chamber. The controller is configured to receive the position deviation monitored by the monitoring device and output a control signal according to the position deviation monitored by the monitoring device. The adjusting device is configured to adjust the position of the lifting device according to the control signal so that the position deviation of the wafer in the process chamber is smaller than or equal to the preset position deviation. The adjusting device adjusts the position of the lifting device according to the control signal so as to adjust the position of the wafer, so that the position deviation of the wafer in the process chamber can be smaller than or equal to the preset position deviation, and the position precision of the wafer in the process chamber is improved to a certain extent.

Description

Plasma processing equipment

Technical Field

The application relates to the technical field of semiconductors, in particular to plasma processing equipment.

Background

In the process of processing the wafer, the precision of the transmission position of the wafer in the machine table has higher requirements. The plasma processing technology belongs to a common technology in the wafer processing process, the position precision of the wafer in the process cavity of the plasma reaction chamber has important influence on the plasma processing of the wafer, and in the related technology, the position precision of the wafer in the process cavity of the plasma reaction chamber is yet to be further improved.

SUMMERY OF THE UTILITY MODEL

In view of the above, it is desirable to provide a plasma processing apparatus to improve the positional accuracy of a wafer within a process chamber of a plasma reaction chamber.

To achieve the above object, an embodiment of the present application provides a plasma processing apparatus, including:

the plasma reaction chamber is provided with a process cavity;

the lifting device is configured to bear the wafer in the process chamber and drive the wafer to ascend or descend;

the monitoring device is positioned in the process chamber and is configured to monitor the position deviation of the wafer in the process chamber;

a controller configured to receive the position deviation monitored by the monitoring device and output a control signal according to the position deviation monitored by the monitoring device; and

and the adjusting device is configured to adjust the position of the lifting device according to the control signal so that the position deviation of the wafer in the process chamber is smaller than or equal to a preset position deviation.

In one embodiment, the monitoring apparatus includes a light emitting device and a light sensing device located in the process chamber, the light emitting device is configured to emit a light beam to monitor a position deviation of the wafer in the process chamber, the light sensing device is configured to receive the light beam emitted by the light emitting device, and the position deviation monitored by the monitoring apparatus is a signal triggered by the light sensing device.

In an embodiment, the plasma reaction chamber is formed with dodge the hole, elevating gear includes first driving piece and is located dodge downthehole lift post, the lift post is configured to bear the weight of the wafer, first driving piece is configured to the drive the lift post is followed the axial displacement who dodges the hole is in order to make the wafer rises or descends, the diameter of dodging the hole is greater than light emitting device shines the twice of the facula diameter that photosensitive device department formed.

In one embodiment, the light emitting device and the light sensing device are oppositely arranged along the lifting direction of the lifting device.

In one embodiment, the plasma reaction chamber comprises:

a reaction chamber body, wherein the process cavity is formed on the reaction chamber body;

the upper electrode is positioned in the process cavity, the upper electrode is connected to the top of the reaction chamber main body, and the light-emitting device is embedded in the upper electrode; and

the lower electrode is positioned in the process cavity, the lower electrode is connected to the bottom of the reaction chamber main body, and the photosensitive device is embedded in the lower electrode.

In one embodiment, the light emitting device is a laser emitter.

In one embodiment, the adjustment device comprises:

the bearing platform is connected with the lifting device; and

and the driving assembly is configured to drive the bearing platform to move according to the control signal so that the position deviation of the wafer in the process chamber is smaller than or equal to a preset position deviation.

In an embodiment, the driving assembly is configured to drive the supporting platform to move along a preset direction according to the control signal, and the preset direction is perpendicular to a lifting direction of the lifting device.

In one embodiment, the number of the monitoring devices is at least three, and projection areas of the at least three monitoring devices are distributed in a triangular shape along the lifting direction of the lifting device.

In one embodiment, the plasma processing apparatus further comprises a pre-alignment device, and the plasma reaction chamber is configured to receive the wafer taken out of the pre-alignment device.

According to the plasma processing equipment, the lifting device can be used for bearing the wafer, the transfer robot can send the wafer into the process cavity of the plasma reaction chamber and place the wafer on the lifting device, and the lifting device bears the wafer. When the position deviation of the wafer in the process cavity measured by the monitoring device is larger than the preset position deviation, the controller receives and outputs a control signal according to the monitored position deviation, and the adjusting device adjusts the position of the lifting device according to the control signal so as to adjust the position of the wafer, so that the position deviation of the wafer in the process cavity can be ensured to be smaller than or equal to the preset position deviation, and the correction of the position deviation of the wafer in the process cavity is realized, and the position precision of the wafer in the process cavity is improved to a certain extent.

Drawings

FIG. 1 is a schematic diagram of a plasma chamber and lift apparatus illustrating a wafer prior to transfer to a process chamber;

FIG. 2 is a schematic view of a wafer being transferred to a process chamber of the plasma chamber of FIG. 1;

FIG. 3 is a schematic structural view of a plasma chamber and a lifting device in the related art, illustrating a state in which a wafer in a process chamber moves down to the bottom of the plasma chamber along with the lifting device;

FIG. 4 is a schematic structural diagram of a plasma processing apparatus according to an embodiment of the present application;

FIG. 5 is a schematic view of a plasma chamber and a monitoring device according to an embodiment of the present disclosure;

FIG. 6 is a view taken along line A of FIG. 5;

FIG. 7 is a view taken along line B of FIG. 5;

FIG. 8 is a schematic structural diagram of an adjustment device according to an embodiment of the present application;

FIG. 9 is a view taken along line C of FIG. 8;

FIG. 10 is a schematic view of a wafer being transferred between a pre-alignment apparatus and a plasma chamber according to an embodiment of the present invention.

Description of reference numerals: a plasma reaction chamber 1; a process chamber 11; a relief hole 12; a reaction chamber main body 13; an upper electrode 14; a lower electrode 15; a lifting column 21; a monitoring device 3; a light emitting device 31; a light sensing device 32; an adjusting device 4; a load-bearing platform 41; a primary stage 411; a secondary stage 412; a drive assembly 42; a first transmission shaft 421; a second driving member 422; a second transmission shaft 423; the third driver 424; a pre-alignment device 100; a wafer 200.

Detailed Description

It should be noted that, in the present application, technical features in examples and embodiments may be combined with each other without conflict, and the detailed description in the specific embodiment should be understood as an explanation of the gist of the present application and should not be construed as an improper limitation to the present application.

In the description of the embodiments of the present application, "upper", "lower", "top", "bottom", orientation or positional relationship is based on the orientation or positional relationship shown in fig. 4. It is to be understood that such directional terms are merely for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the present application.

As part of the inventive concept of the present application, before describing the embodiments of the present application, the reason why the position accuracy of the wafer in the process chamber of the plasma reaction chamber needs to be further improved needs to be analyzed, and the technical solution of the embodiments of the present application is obtained through reasonable analysis.

Referring to fig. 1 to 3, a wafer is transferred into a process chamber 11 of a plasma reaction chamber 1 by a transfer robot, and fig. 1 illustrates a state of the plasma reaction chamber 1 before the wafer is transferred into the process chamber 11 of the plasma reaction chamber 1. Fig. 2 shows a state where the transfer robot places the wafer on the lift device in the process chamber 11. Fig. 3 shows a state where the wafer in the process chamber 11 is lowered to the final position at the bottom of the plasma reaction chamber 1 after the wafer is lowered along with the lifting device. Fig. 1 to 3 show a lifting column 21 in the lifting device. The lifting device can only be raised or lowered. The positional deviation of the wafer in the process chamber cannot be obtained. During the process of the transfer robot placing the wafer on the lifting device and the lowering of the lifting device, a new positional deviation is introduced into the wafer, which is mainly expressed as: the wafer is placed on the lifting device in the process cavity 11 of the plasma reaction chamber 1 from the transfer robot, so that new position deviation can be brought; the lifting device moves downwards, so that new position deviation is brought in the process of lowering the wafer in the process cavity 11 to the final position at the bottom of the plasma reaction chamber 1. If these positional deviations can be appropriately corrected, the positional accuracy of the wafer in the process chamber 11 of the plasma reaction chamber 1 can be improved to some extent.

In view of this, the present embodiment provides a plasma processing apparatus, referring to fig. 4 to 10, which includes a plasma reaction chamber 1, a lifting device, a monitoring device 3, a controller and an adjusting device 4. The plasma reaction chamber 1 is formed with a process chamber 11. The lifting device is configured to carry the wafer 200 in the process chamber 11 and drive the wafer 200 to ascend or descend. The monitoring device 3 is located in the process chamber 11, and the monitoring device 3 is configured to monitor a positional deviation of the wafer 200 in the process chamber 11. The controller is configured to receive the positional deviation monitored by the monitoring device 3 and output a control signal according to the positional deviation monitored by the monitoring device. The adjusting device 4 is configured to adjust the position of the lifting device according to the control signal so that the positional deviation of the wafer 200 in the process chamber 11 is less than or equal to a preset positional deviation. In this configuration, the lifting device can be used to carry the wafer 200, and the transfer robot can transfer the wafer 200 into the process chamber 11 of the plasma reaction chamber 1 and place the wafer on the lifting device, and the lifting device carries the wafer 200. In the process that the lifting device drives the wafer 200 to descend to the final position at the bottom of the plasma reaction chamber 1, the wafer 200 is supported on the lifting device and moves along with the movement of the lifting device, when the position deviation of the wafer 200 in the process chamber 11 measured by the monitoring device 3 is greater than the preset position deviation, the controller outputs a control signal according to the monitored position deviation, the adjusting device 4 adjusts the position of the lifting device according to the control signal so as to adjust the position of the wafer 200, so as to ensure that the position deviation of the wafer 200 in the process chamber 11 can be less than or equal to the preset position deviation, and correct the position deviation of the wafer 200 in the process chamber 11 is realized, thereby improving the position accuracy of the wafer 200 in the process chamber 11 to a certain extent.

In one embodiment, the plasma chamber is used to perform a plasma activation process on the surface of the wafer 200 before bonding the wafer 200.

In one embodiment, the plasma chamber may be a chamber that performs other plasma processing processes. For example, the plasma reaction chamber may be a plasma etch chamber, a plasma enhanced chemical vapor deposition chamber, a physical vapor deposition chamber, a plasma processing chamber, an ion implantation chamber, or other suitable plasma reaction chamber.

In one embodiment, referring to fig. 4, the plasma chamber 1 includes a chamber body 13, an upper electrode 14, and a lower electrode 15. The process chamber 11 is formed in the chamber body 13. An upper electrode 14 is disposed in the process chamber 11, and the upper electrode 14 is connected to the top of the chamber body 13. The lower electrode 15 is located in the process chamber 11, and the lower electrode 15 is connected to the bottom of the chamber body 13.

In one embodiment, referring to fig. 4, when the lifting device is lowered, the wafer 200 supported on the lifting device moves down along with the lifting device and falls on the lower electrode 15, and the wafer 200 is adsorbed by the lower electrode 15.

In one embodiment, referring to fig. 4 to 7, the monitoring apparatus 3 includes a light emitting device 31 and a light sensing device 32 located in the process chamber 11, the light emitting device 31 is configured to emit a light beam to monitor a position deviation of the wafer 200 in the process chamber 11, the light sensing device 32 is configured to receive the light beam emitted by the light emitting device 31, and the position deviation monitored by the monitoring apparatus 3 is a signal triggered by the light sensing device 32. In this configuration, the light beam emitted from the light emitting device 31 is received by the light receiving device 32 to detect whether the position deviation of the wafer 200 is smaller than or equal to the predetermined position deviation. When the position deviation of the wafer 200 in the process chamber 11 is larger than the predetermined position deviation, the light beam emitted from the light emitting device 31 is blocked by the wafer 200 and cannot be received by the light sensing device 32.

In one embodiment, referring to fig. 4 to 7, the light emitting device 31 is embedded in the upper electrode 14. This configuration facilitates the installation of the light emitting device 31 in the process chamber 11.

In one embodiment, referring to fig. 4-7, the photo sensor device 32 is embedded in the bottom electrode 15. This configuration facilitates the installation of the photosensitive device 32 in the process chamber 11.

It is understood that the wafer 200 is finally placed at the bottom of the plasma reaction chamber 1, the final position of the wafer 200 along the elevating direction of the elevating device is substantially determined, and the positional deviation of the wafer 200 is mainly the positional deviation in the plane perpendicular to the elevating direction of the elevating device. In an embodiment, referring to fig. 4 to 7, the number of the monitoring devices 3 is at least three, and the projection areas of the at least three monitoring devices 3 are distributed in a triangle along the lifting direction of the lifting device. In this structure, at least three points that are not on the same straight line form a plane, and when the position deviation of the wafer 200 in the plane perpendicular to the lifting direction of the lifting device is greater than the preset position deviation, at least one of the three monitoring devices 3 in triangular distribution will be triggered to generate a signal indicating that the position deviation of the wafer 200 does not meet the requirement.

In an embodiment, referring to fig. 4 to 7, along the lifting direction of the lifting device, the projection areas of the three monitoring devices 3 are distributed in a triangle. Each monitoring device 3 comprises a light emitting device 31 and a light sensing device 32. Along the lifting direction of the lifting device, the projection areas of the three light-emitting devices 31 are distributed in a triangular shape, and the projection areas of the three light-sensing devices 32 are distributed in a triangular shape.

In an embodiment, referring to fig. 4 to 7, along the lifting direction of the lifting device, the projection areas of the three monitoring devices 3 are distributed in a triangle. When the position deviation of the wafer 200 is smaller than or equal to the preset position deviation, the optical signal emitted by the light emitting device 31 of each monitoring device 3 can be received by the corresponding photosensitive device 32, and the position deviation of the wafer 200 meets the requirement. When the position deviation of the wafer 200 is greater than the preset position deviation, the optical signal emitted by the light emitting device 31 of at least one of the monitoring devices 3 is blocked by the wafer 200 and cannot be received by the corresponding light sensing device 32, and the position deviation of the wafer 200 does not meet the requirement.

It can be understood that the preset position deviation is related to the spot diameter formed by the light-emitting device 31 irradiating the photosensitive device 32, and the smaller the spot diameter is, the smaller the preset position deviation is, the higher the position accuracy of the wafer 200 in the process chamber 11 is. In one embodiment, the light emitting device 31 is a laser emitter. Thus, the laser has better bundling performance, the diameter of the formed light spot is smaller, and the position accuracy of the wafer 200 in the process chamber 11 can be improved to a certain extent by using the laser emitter as the light emitting device 31.

In one embodiment, the preset position deviation may be set according to actual conditions.

In one embodiment, the light emitting device 31 and the light sensing device 32 are disposed opposite to each other along the lifting direction of the lifting device. With such a structure, the wafer 200 can be ensured to be always kept unchanged in the process of being lowered to the bottom of the plasma reaction chamber 1 along with the lifting device.

In an embodiment, referring to fig. 4 to 6, an avoiding hole 12 is formed in the plasma reaction chamber 1, the lifting device includes a first driving member and a lifting column 21 located in the avoiding hole 12, the lifting column 21 is configured to carry the wafer 200, the first driving member is configured to drive the lifting column 21 to move along an axial direction of the avoiding hole 12 so as to raise or lower the wafer 200, and a diameter of the avoiding hole 12 is greater than twice a diameter of a light spot formed by the light emitting device 31 irradiating the photosensitive device 32. In this configuration, the wafer 200 can be supported on the lifting column 21 and move along with the lifting column 21, and the first driving member drives the lifting column 21 to move along the axial direction of the avoiding hole 12 to lift or lower the wafer 200. The diameter of the avoiding hole 12 is larger than twice of the diameter of the light spot, so that the lifting column 21 can have enough radial movement space, and the position deviation of the wafer 200 supported on the lifting column 21 can be adjusted to be smaller than or equal to the preset position deviation.

In one embodiment, the first driving member is a driving motor.

In one embodiment, the drive motor is typically an electric motor.

In an embodiment, referring to fig. 4 to 6, the number of the lifting columns 21 is three, and the three lifting columns 21 are distributed in a triangle. With such a structure, the three lifting columns 21 distributed in a triangular shape can stably support the wafer 200, and the number of the lifting columns 21 is relatively small.

In an embodiment, referring to fig. 4 to 6, each lifting column 21 is provided with an avoiding hole 12.

In one embodiment, three lifting columns 21 may also be disposed through a larger clearance hole 12.

In one embodiment, referring to fig. 4-6, the avoiding hole 12 penetrates the chamber body 13 and the bottom electrode 15.

In one embodiment, referring to fig. 4, 8 and 9, the adjusting device 4 includes a supporting platform 41 and a driving assembly 42. The carrying platform 41 is connected with the lifting device. The driving assembly 42 is configured to drive the loading platform 41 to move according to the control signal so that the position deviation of the wafer 200 in the process chamber 11 is smaller than or equal to a predetermined position deviation. In this structure, the driving assembly 42 drives the supporting platform 41 to move, and the supporting platform 41 drives the lifting device to move, so as to adjust the position of the wafer 200 supported on the lifting device, so that the position deviation of the wafer 200 in the process chamber 11 is smaller than or equal to the preset position deviation.

In one embodiment, the driving assembly 42 is configured to drive the supporting platform 41 to move along a predetermined direction according to the control signal, and the predetermined direction is perpendicular to the lifting direction of the lifting device. In this way, during the process of adjusting the position of the wafer 200 by the driving assembly 42 driving the carrying platform 41 to move, the lifting device will not be affected to ascend or descend, so that the position of the wafer 200 can be adjusted at any height position during the lifting process of the lifting device, so that the positional deviation of the wafer 200 in the process chamber 11 can meet the requirement.

In an embodiment, the predetermined direction may also form a certain included angle with the lifting direction of the lifting device, and the predetermined direction is not perpendicular to the lifting direction of the lifting device.

In one embodiment, the first driving member is connected to the supporting platform 41, and the first driving member is drivingly connected to the lifting column 21 to drive the lifting column 21 to ascend or descend.

In an embodiment, referring to fig. 4, 8 and 9, the supporting platform 41 includes a first supporting platform 411 and a second supporting platform 412, the second supporting platform 412 is connected to the lifting device, and the second supporting platform 412 is movably disposed on the first supporting platform 411. Along the lifting direction of the lifting device, the secondary stage 412 is located between the primary stage 411 and the lifting device. The driving assembly 42 includes a first driving member 421, a second driving member 422, a second driving member 423, and a third driving member 424. The second driving member 422 is drivingly connected to the first transmission shaft 421, and the first transmission shaft 421 is threadedly transmitted to the first stage supporting platform 411. The third driving member 424 is connected to the first stage bearing platform 411, the third driving member 424 is drivingly connected to the second transmission shaft 423, and the second transmission shaft 423 is in threaded transmission with the second stage bearing platform 412. The first transmission shaft 421 is arranged to intersect with the second transmission shaft 423. Like this structural style, first transmission shaft 421 and second transmission shaft 423 cross arrangement, therefore, first transmission shaft 421 and second transmission shaft 423 nonparallel drive first transmission shaft 421 through second driving piece 422, and third driving piece 424 drive second transmission shaft 423 makes one-level plummer 411 and second grade plummer 412 can move along two nonparallel directions respectively, is convenient for adjust the position of the elevating gear of connection on second grade plummer 412.

In one embodiment, the first transmission shaft 421 is perpendicular to the second transmission shaft 423.

In one embodiment, the first driving member and the second driving member are both driving motors.

In one embodiment, referring to fig. 9, the second driving member 422 drives the first stage 411 to move along the direction indicated by the arrow R1 through the first transmission shaft 421, the third driving member 424 is connected to the first stage 411, and the third driving member 424, the second transmission shaft 423 and the second stage 412 move together with the first stage 411. The third driving member 424 drives the secondary carrier 412 to move in the direction of arrow R2 via the second transmission shaft 423. The lifting device connected to the secondary stage 412 can be adjusted to a desired position in the plane formed by the direction indicated by the arrow R1 and the direction indicated by the arrow R2.

It will be appreciated that the drive assembly 42 may take other forms. In an embodiment, the carrying platform 41 may be driven to move by a belt transmission, so as to drive the lifting device connected to the carrying platform 41 to move.

It can be understood that, because the requirement for the position accuracy of the wafer 200 is high, the monitoring device 3 and the adjusting device 4 are usually used to adjust the position of the wafer 200 in a fine adjustment manner, if the position deviation of the wafer 200 entering the process chamber 11 is large, the adjusting device 4 may need to repeatedly adjust to make the position deviation of the wafer 200 less than or equal to the preset position deviation, and the adjusting device 4 has a large adjusting workload and low efficiency. In one embodiment, referring to fig. 10, the plasma processing apparatus further includes a pre-alignment apparatus 100, and the plasma chamber 1 is configured to receive a wafer 200 removed from the pre-alignment apparatus 100. In such a structure, the wafer 200 is pre-aligned by the pre-alignment device 100, and then the pre-aligned wafer 200 is transferred to the process chamber 11, because the pre-alignment operation is performed on the wafer 200, the position deviation of the wafer 200 entering the process chamber 11 is relatively small, the adjusting device 4 only needs to finely adjust the position of the wafer 200 in the process chamber 11 so that the position deviation of the wafer 200 is smaller than or equal to the preset deviation, the workload of the adjusting device 4 for adjusting the position of the wafer 200 is relatively small, and the adjusting efficiency of the adjusting device 4 is improved.

In one embodiment, referring to fig. 4 to 7, when the wafer 200 is pre-aligned by the pre-alignment apparatus 100 and then transferred into the plasma reaction chamber 1 and carried by the lifting apparatus, the position deviation of the wafer 200 in the process chamber 11 is relatively small, and the projection area of the monitoring apparatus 3 is located at the edge of the projection area of the wafer 200 along the lifting direction of the lifting apparatus.

Specifically, referring to fig. 6 and 7, the projection area of the light sensing device 32 is located at the edge of the projection area of the wafer 200, and the projection area of the light emitting device 31 is located at the edge of the projection area of the wafer 200.

The various embodiments/implementations provided herein may be combined with each other without contradiction.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A plasma processing apparatus, comprising:

the plasma reaction chamber is provided with a process cavity;

2. The apparatus of claim 1, wherein the monitoring device comprises a light emitting device and a light sensing device located in the process chamber, the light emitting device is configured to emit a light beam to monitor a positional deviation of the wafer in the process chamber, the light sensing device is configured to receive the light beam emitted by the light emitting device, and the positional deviation monitored by the monitoring device is a signal triggered by the light sensing device.

3. The plasma processing apparatus according to claim 2, wherein the plasma reaction chamber is formed with an avoidance hole, the lifting device includes a first driving member and a lifting column located in the avoidance hole, the lifting column is configured to bear the wafer, the first driving member is configured to drive the lifting column to move along an axial direction of the avoidance hole so as to raise or lower the wafer, and a diameter of the avoidance hole is greater than twice a diameter of a light spot formed by the light emitting device irradiated to the photosensitive device.

4. The plasma processing apparatus according to claim 2, wherein the light emitting device and the photosensitive device are arranged oppositely in a lifting direction of the lifting device.

5. The plasma processing apparatus of claim 2, wherein the plasma reaction chamber comprises:

6. The plasma processing apparatus of claim 2, wherein the light emitting device is a laser emitter.

7. The plasma processing apparatus according to any of claims 1 to 6, wherein the adjusting means comprises:

the bearing platform is connected with the lifting device; and

8. The apparatus of claim 7, wherein the driving assembly is configured to drive the carrier platform to move in a predetermined direction according to the control signal, the predetermined direction being perpendicular to a lifting direction of the lifting device.

9. The plasma processing apparatus according to any of claims 1 to 6, wherein the number of the monitoring devices is at least three, and projection areas of at least three of the monitoring devices are distributed in a triangular shape along a lifting direction of the lifting device.

10. The plasma processing apparatus of any of claims 1 to 6, further comprising a pre-alignment device, wherein the plasma reaction chamber is configured to receive a wafer removed from the pre-alignment device.