Accurate positioning device and positioning method for wafer measurement

Abstract

The invention belongs to the field of vacuum measurement, and relates to an accurate positioning device and positioning method for wafer measurement. The wafer accurate positioning device comprises a driving mechanism, a positioning mechanism and a bearing mechanism which are installed in the transmission cavity. The driving mechanism is used for pushing the wafer falling on the bearing mechanism to the positioning mechanism, the driving mechanism comprises an elastic piece, an armature, a push block and an electromagnet, the elastic piece is fixed in the transfer cavity and is provided with a free end for releasing elastic force, the armature and the push block are installed at the free end, and the electromagnet fixed in the transfer cavity is arranged on the opposite side of the armature; after being electrified, the electromagnet adsorbs the armature, so that the elastic sheet deforms, and the push block positioned above the armature pushes the wafer towards the direction of the positioning mechanism; the armature is released after the electromagnet is powered off, and the free end of the elastic piece resets the armature and the push block backwards. According to the invention, the wafer can be accurately positioned, the operation is simple, the wafer is not damaged, the method can be used for positioning detection of the transparent wafer, and the heat dissipation performance in the cavity is good.

Description

Technical Field

[0001] The invention belongs to the field of vacuum measurement, and in particular relates to a precise positioning device and a positioning method for wafer measurement. Background Art

[0002] With the rapid development of the integrated circuit industry, the demand for chip testing equipment is growing, especially the market demand for critical dimension measurement equipment (Critical Dimension Scanning Electron Microscope, CD-SEM) has increased significantly. CD-SEM equipment uses scanning electron microscope (SEM) technology to accurately measure chips, and SEM technology requires operation in a high vacuum environment, so the chip must be transferred from the atmospheric environment to the high vacuum environment where the SEM equipment is located. At present, this transfer process is mainly achieved through the semiconductor equipment front end module (Equipment Front End Module, EFEM), which is responsible for taking out the wafer from the wafer box and transferring it to the CD-SEM's transmission chamber. After the transmission chamber is evacuated to a predetermined vacuum degree, the isolation valve connected to the vacuum manipulator chamber can be opened, and the vacuum manipulator transfers the wafer to the SEM for inspection.

[0003] First of all, the current focus of technological development is to improve the repeatability of the EFEM manipulator and the vacuum manipulator to ensure the positioning accuracy of the wafer under the SEM. The key to positioning accuracy lies in the transfer accuracy of the wafer between the two manipulators. Specifically, in the current EFEM manipulator design, the internal transfer process of the wafer usually directly places the wafer on a column or other supporting device in the chamber, and then the vacuum manipulator performs the wafer removal operation in the chamber. This process requires extremely high positioning accuracy of the manipulator, and has strict requirements on the stability and repeatability of the manipulator. Therefore, a positioning device that is easy to operate is needed to accurately position the wafer while ensuring that the fragile wafer is not damaged.

[0004] Secondly, in order to accurately measure this accuracy, at least three digital laser sensors are usually used to measure synchronously. The digital laser sensor emits a light spot with a small diameter, and the receiver detects the corresponding change in light flux. The light flux value is changed by the wafer blocking part of the light spot to determine the position of the wafer. Subsequently, it is necessary to verify whether each wafer passed through the EFEM falls within the predetermined accuracy range. However, this measurement method is only applicable to non-transparent wafers, and has significant limitations for transparent wafers. In addition, the debugging process of the digital laser sensor is very complicated, and technicians need to invest a lot of time to adjust the position and verticality.

[0005] On the other hand, during the wafer transfer process, the transfer chamber needs to frequently establish and destroy the vacuum. Although the time to destroy the vacuum is short, it takes a long time to establish a high vacuum state. In order to improve the wafer transfer efficiency of CD-SEM, the transfer chamber is usually designed to be smaller to shorten the time required to reach a high vacuum state. After the high vacuum is established, the vacuum robot needs to complete the wafer picking and placing actions in the transfer chamber before the vacuum can be broken. After taking the wafer, the wafer needs to be sent to the SEM for inspection and then put back into the transfer chamber after the inspection is completed. During the interval between taking and placing the wafer, the transfer chamber must continue to maintain a high vacuum state. Therefore, in a high vacuum environment, the heat dissipation performance of the wafer positioning device is required not to be significantly affected. Summary of the invention

[0006] The first purpose of the present invention is to solve the problem that it is difficult to accurately position the wafer in the transmission cavity of the CD-SEM in an efficient and simple manner during the existing wafer measurement process. The present invention provides a precise positioning device for wafer measurement. The invention content is as follows:

[0007] The precise positioning device for wafer measurement includes a driving mechanism, a positioning mechanism and a bearing mechanism installed in the transfer cavity;

[0008] The driving mechanism is used to push the wafer placed on the carrying mechanism to the positioning mechanism, and the driving mechanism includes a spring, an armature, a push block and an electromagnet. The spring is fixed in the transfer cavity and has a free end for releasing the elastic force, the armature and the push block are assembled on the free end, and an electromagnet fixed in the transfer cavity is arranged on the opposite side of the armature;

[0009] When the electromagnet is energized, it attracts the armature, causing the spring to deform, and the push block located above the armature pushes the wafer toward the positioning mechanism;

[0010] The electromagnet releases the armature after power is cut off, and the free end of the spring piece resets the armature and the push block backwards under the action of the elastic restoring force.

[0011] Preferably, at least two of the positioning mechanisms are installed on opposite sides of the driving mechanism to position two opposite shoulders of the wafer;

[0012] The positioning mechanism comprises a positioning seat and a positioning column fixed on the positioning seat, and the top end of the positioning column is a cone.

[0013] Preferably, the positioning seat is locked in the transfer cavity by screws, and the positioning seat is rotated to a set position before being locked, so that the positioning column can abut against the wafer.

[0014] Furthermore, the driving mechanism also includes a base, the base is fixed on the bottom wall of the transfer chamber, and the electromagnet is installed on the base; the fixed end of the spring is installed on the base in an upright state.

[0015] The positioning method of the precise positioning device for wafer measurement comprises the following steps:

[0016] The wafer is fed into the transfer chamber and supported by the carrying mechanism;

[0017] When the electromagnet is energized, it attracts the armature, which drives the push block at the free end of the spring to move, pushing the wafer toward the positioning mechanism until it rests against the positioning column of the positioning mechanism, thereby accurately positioning the wafer.

[0018] When the electromagnet is powered off, the armature is released, and the armature and the push block return to their initial positions under the elastic force of the shrapnel.

[0019] The driving mechanism of the present invention pushes the wafer close to the positioning mechanism and cooperates with the positioning mechanism to position the wafer. Even if the wafer does not fall accurately on the supporting mechanism, it can be accurately positioned, which significantly improves the positioning accuracy of the wafer, thereby improving the reliability of the measurement data and reducing the workload of the debugging personnel.

[0020] The driving mechanism of the present invention uses an electromagnet to cooperate with an armature and a spring to push the wafer, which has the advantages of simple structure, stable performance and small size compared to a commonly used motor or cylinder. In addition, by adjusting the current of the electromagnet to control its attraction, the device can effectively prevent the wafer from being crushed even in unexpected situations such as the wafer falling or tilting.

[0021] The positioning post of the present invention adopts a conical head design, which not only plays a guiding role in the falling process of the wafer to prevent the wafer from falling and tilting, but also can quickly detach from the positioning post during the rising process of the wafer, avoiding the robot arm accidentally hitting the positioning post due to its own movement accuracy problems when moving upward, thereby preventing the wafer from shifting and ensuring that the final positioning accuracy is not affected.

[0022] The second object of the present invention is to provide a position accuracy detection device suitable for transparent / semi-transparent wafers based on the above-mentioned wafer precise positioning device, which automatically completes the positioning accuracy detection during the wafer positioning process, thereby improving the work efficiency and detection accuracy. The invention content is as follows:

[0023] The driving mechanism further includes two photoelectric sensors 1 and 2 which are staggeredly installed in the front-to-back direction;

[0024] A position detection sheet is installed at the free end of the elastic sheet, and the position detection sheet includes a baffle plate 1 and a baffle plate 2 which are sequentially spaced apart in the left-right direction;

[0025] The baffle plate 1 follows the free end of the spring to move forward to between the photoelectric sensor 1, triggering the photoelectric sensor 1 to send a wafer in place signal; the baffle plate 2 follows the free end to move backward to between the photoelectric sensor 2, triggering the photoelectric sensor 2 to send a reset in place signal.

[0026] Preferably, the position detection piece comprises a detection piece body installed in a horizontal shape, and the baffle plate 1 and the baffle plate 2 are both vertically fixed below the detection piece body;

[0027] The photoelectric sensor 1 and the photoelectric sensor 2 are both through-beam sensors.

[0028] The positioning method of the above wafer positioning device is:

[0029] The wafer is fed into the transfer chamber and supported by the carrying mechanism;

[0030] After the electromagnet is energized, it attracts the armature, which drives the push block at the free end of the spring to move, and the position detection sheet moves synchronously with the push block; when the wafer is pressed against the positioning column by the push block, the baffle plate 1 of the position detection sheet enters between the photoelectric sensor 1, thereby judging that the wafer has been moved into position, and at this time, the baffle plate 2 is away from the photoelectric sensor 2;

[0031] After the electromagnet is powered off, the armature is released, and the armature and the push block automatically move backward under the elastic force of the shrapnel. The position detection sheet follows the push block to reset, and the baffle plate 2 enters between the photoelectric sensor 2, thereby judging that the push block is reset in place. At this time, the baffle plate 1 is away from the photoelectric sensor 1.

[0032] The position detection sheet of the present invention moves synchronously with the push block, and the two groups of photoelectric sensors and two baffles cooperate with each other to detect the movement state of the electromagnet and analyze the measurement results of the position detection sheet. By analyzing the feedback signals of the two photoelectric sensors, firstly, it can be judged whether the electromagnet functions normally; secondly, it can be accurately judged whether the wafer has been accurately pushed into the specified position; thirdly, it can monitor whether there are abnormal conditions such as falling, tilting or fragmentation during the wafer transfer process. This method is also applicable to the detection of transparent wafers.

[0033] The third purpose of the present invention is to improve the heat dissipation performance of the wafer positioning device in a high vacuum environment based on the above-mentioned wafer precise positioning device.

[0034] The iron core of the electromagnet of the present invention is a soft magnetic alloy; the material of the push block is nylon or Teflon; the material of the armature is a soft magnetic alloy.

[0035] The electromagnet uses a soft magnetic alloy as its core, making full use of the high magnetic saturation, high magnetic permeability and low coercivity of the soft magnetic alloy to achieve rapid magnetic conversion and complete the work of pushing the wafer with lower electrical energy. This not only improves work efficiency, but also reduces heat generation, especially in a high vacuum environment, where the heat dissipation efficiency of the electromagnet is low. Therefore, the non-vacuum state is only achieved when the wafer is transferred on the atmospheric side, and the generated heat can be quickly dissipated within a limited time.

[0036] Preferably, at least three supporting mechanisms are provided for stably supporting the wafer; the supporting mechanism includes a supporting seat fixed in the transfer cavity, a supporting column installed on the supporting seat, and a supporting ring installed at the front end of the supporting column, and the supporting ring protrudes from the supporting column and is in point contact with the wafer.

[0037] The use of a carrier ring as a contact part with the wafer achieves point contact with the wafer, thereby reducing friction. This enables the drive mechanism to use less force to push the wafer to move, while reducing power requirements and helping to reduce the accumulation of heat energy.

[0038] In summary, the beneficial effects of the present invention are:

[0039] During the wafer measurement process, the present invention can efficiently, simply and reliably position the wafer accurately in the transmission cavity of the CD-SEM.

[0040] The present invention adopts a mechanical detection method and is widely applicable to position accuracy detection devices for all transparent wafers. It automatically completes positioning accuracy detection during wafer positioning, thereby improving work efficiency and detection accuracy.

[0041] The invention significantly improves the heat dissipation performance of the wafer positioning device in a high vacuum environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0043] Figure 1 It is a schematic diagram of the internal structure of the transfer chamber of the present invention;

[0044] Figure 2 It is a partial enlarged schematic diagram of the driving mechanism and the bearing mechanism of the present invention;

[0045] Figure 3 It is a partially enlarged schematic diagram of the driving mechanism and the bearing mechanism of the present invention from another perspective;

[0046] Figure 4 is a schematic diagram of the positioning mechanism of the present invention;

[0047] Figure 5 It is a schematic diagram of the present invention when accurately positioning a wafer.

[0048] The markings in the figure are:

[0049] 1. Driving mechanism; 1-1. Electromagnet; 1-2. Armature; 1-3. Spring piece; 1-4. Push block; 1-5. Position detection sheet; 1-6. Photoelectric sensor 1; 1-7. Photoelectric sensor 2; 1-8. Base; 1-9. Baffle 1; 1-10. Baffle 2;

[0050] 2. Positioning mechanism; 2-1. Positioning column; 2-2. Positioning seat;

[0051] 3. Carrying mechanism; 3-1. Carrying ring; 3-2. Carrying column; 3-3. Carrying seat;

[0052] 4. Transfer cavity. DETAILED DESCRIPTION

[0053] Example 1

[0054] like Figures 1 to 5 As shown, this embodiment provides a precise positioning device for wafer measurement, including a transfer chamber 4 that can be evacuated to a high vacuum, in which a driving mechanism 1, a positioning mechanism 2 and a supporting mechanism 3 are installed. There is at least one driving mechanism 1, which is used to push the wafer toward the positioning mechanism 2. There are at least two positioning mechanisms 2, which are located on the opposite side of the driving mechanism 1, and cooperate with the driving mechanism 1 to abut and position the wafer. There are at least three supporting mechanisms 3, which are evenly distributed in the same horizontal plane in the transfer chamber 4 to ensure stable support of the wafer on the horizontal plane.

[0055] The specific structure of the driving mechanism of this embodiment is introduced below.

[0056] Please focus on Figure 2 and Figure 3 The driving mechanism 1 includes a base 1-8, a spring 1-3, an armature 1-2, a push block 1-4 and an electromagnet 1-1. The base 1-8 is fixed on the bottom wall of the transfer chamber 4. The base 1-8 is a T-shaped structure as a whole. The electromagnet 1-1 is installed on the longitudinal seat of the base. The fixed end of the spring 1-3 is installed on the transverse seat end of the base. The spring 1-3 is arranged in an upright shape. The end of the spring 1-3 away from the fixed end is a free end. The armature 1-2 and the push block 1-4 are installed on the free end of the spring 1-3. The armature 1-2 and the iron core of the electromagnet 1-1 are arranged opposite to each other. In the initial state, there is a gap between the armature 1-2 and the electromagnet 1-1.

[0057] In an optional embodiment, the push block 1-4 is fixed above the armature 1-2 to facilitate pushing the wafer. The push block 1-4 is the contact part with the wafer, and preferably uses soft wear-resistant materials, including but not limited to nylon, Teflon, etc.

[0058] The specific structure of the positioning mechanism is introduced below.

[0059] Please focus on Figure 1 and Figure 4 The positioning mechanism 2 includes a positioning seat 2-2 and a positioning column 2-1 fixed on the positioning seat 2-2. The positioning seat 2-2 is locked in the transfer cavity 4 by screws. Before the positioning seat 2-2 is locked, the placement position of the wafer is set first, and then the positioning seat 2-2 is rotated to the installation angle that allows the positioning column 2-1 to just abut against the wafer, and then the screws are tightened to position the shoulder of the wafer.

[0060] In a specific embodiment, two positioning mechanisms are provided so that the two positioning columns 2 - 1 thereof clamp the two opposite shoulders of the wafer and simultaneously position the wafer longitudinally and transversely, thereby positioning the wafer more stably and accurately.

[0061] In a preferred embodiment, the top of the positioning post 2-1 is a cone, which not only guides the wafer during its fall to prevent it from falling or tipping over, but also allows the wafer to quickly detach from the positioning post 2-1 during its rise, preventing the manipulator from accidentally hitting the positioning post 2-1 due to its own movement accuracy during upward movement. If the positioning post 2-1 is accidentally hit, the wafer will shift, affecting the final positioning accuracy. In addition, the material selection of the positioning post 2-1 is also crucial, and a soft material with high wear resistance, such as nylon and Teflon, is used to reduce potential damage to the wafer surface. Of course, the positioning post 2-1 can also be made of other soft materials well known in the art, and this application does not limit this.

[0062] The specific structure of the bearing mechanism of this embodiment is introduced below.

[0063] Please focus on Figure 1 and Figure 2 The bearing mechanism 3 includes a bearing seat 3-3 and a bearing column 3-2. The bearing seat 3-3 is installed on the side wall or the bottom wall of the transfer chamber 4, and the bearing column 3-2 is horizontally installed on the bearing seat 3-3. The present application does not limit the distribution mode of the bearing mechanism 3, which can be uniformly distributed or non-uniformly distributed. In a specific embodiment, four bearing mechanisms 3 are provided, and they are distributed relative to each other in pairs, so as to support the wafer more evenly.

[0064] The transfer chamber 4 of this embodiment is only a schematic diagram, which is different from its actual structure. Since the existing transfer chamber 4 is a sealed structure, in order to facilitate the display of the structure of the components in the chamber, some components of the transfer chamber 4 are disassembled.

[0065] The working process of this embodiment is:

[0066] The wafer is transferred from the atmosphere side outside the transfer chamber 4 to the transfer chamber 4 by the robot at the EFEM, and then descends to the set height after reaching the set position. At this time, the wafer also lands on the carrying mechanism 3.

[0067] The coil of the electromagnet 1-1 is energized to generate a magnetic field, which attracts the armature 1-2 to move forward. When the armature 1-2 moves, the free end of the spring 1-3 bends and deforms forward, and the push block 1-4 on the spring 1-3 moves forward with the armature 1-2, thereby pushing the wafer toward the positioning mechanism 2 until the two opposite shoulders of the wafer abut against the two positioning pillars 2-1, thereby completing the precise positioning of the wafer.

[0068] Then, the coil of the electromagnet 1-1 is powered off, and the armature 1-2 returns to its initial position under the elastic force of the spring 1-3 because the magnetic force of the electromagnet 1-1 disappears, and the push block 1-4 also retreats and returns to its initial position, preparing for the next wafer movement.

[0069] The transfer chamber 4 is evacuated. After the evacuation, the vacuum robot reaches under the wafer, lifts the wafer, and places it accurately under the lens of the subsequent measuring device.

[0070] Example 2

[0071] This embodiment is based on Embodiment 1 and provides a position accuracy detection device suitable for transparent / semi-transparent wafers, which automatically completes positioning accuracy detection during wafer positioning, thereby improving work efficiency and detection accuracy.

[0072] Please focus on Figure 2 and Figure 3 The driving mechanism 1 of this embodiment further includes a position detection sheet 1-5 and two photoelectric sensors. Among them, the photoelectric sensor 1-6 and the photoelectric sensor 2-1-7 are staggered and installed on the base along the front-back direction. The photoelectric sensor is a beam sensor, that is, it includes a transmitting end and a receiving end arranged oppositely.

[0073] The position detection sheet 1-5 is also installed on the free end of the spring sheet 1-3. The position detection sheet 1-5 includes a horizontal detection sheet body. The detection sheet body is located above the photoelectric sensor. Baffle 1-9 and baffle 2 1-10 are vertically fixed below the detection sheet body. Baffle 1-9 and baffle 2 1-10 are spaced apart from each other.

[0074] The working principle of this embodiment is:

[0075] In the process of pushing the wafer by the push block 1-4, the position detection piece 1-5 moves forward following the push block 1-4. When the wafer reaches the predetermined position, the baffle 1-9 just enters between the transmitting end and the receiving end of the photoelectric sensor 1-6 and completely blocks the light. The photoelectric sensor 1-6 generates a signal change by detecting the blockage and sends a signal to the control system. At the same time, the photoelectric sensor 1-7 does not detect the baffle 1-10. The control system can determine that the wafer has moved into place, realize real-time monitoring and adjustment, and ensure the stability of high-precision positioning.

[0076] When the push block 1-4 moves away from the wafer, the position detection sheet 1-5 moves backward with the push block 1-4, and the baffle 1-10 enters the detection range of the photoelectric sensor 1-7. When the push block 1-4 returns to the initial position, the baffle 1-10 also completely blocks the light of the photoelectric sensor 1-7, and the photoelectric sensor 1-7 generates a signal change and sends a signal to the control system. At the same time, the photoelectric sensor 1-6 does not detect the baffle 1-9, and the control system can determine that the push block 1-4 is reset in place.

[0077] If the wafer falls accidentally during the wafer transfer process of the robot at the EFEM, the wafer will be pushed by the push block 1-4 without the blocking of the positioning column 2-1. The push block 1-4 will continue to move forward, and the baffle 1-9 will follow the push block 1-4 and continue to move forward and pass directly through the photoelectric sensor 1-6. At this time, the photoelectric sensor 1-6 and the photoelectric sensor 2 1-7 do not detect the baffle, and the control system immediately recognizes the abnormality, triggers an alarm and stops the current operation. At this time, the equipment operator can intervene in time to eliminate the fault and ensure the safety of the wafer and the normal operation of the equipment.

[0078] This embodiment has no requirement on the transparency of the wafer and is applicable to positioning detection of various transparent or opaque wafers.

[0079] Example 3

[0080] Based on the second embodiment, this embodiment can further improve the heat dissipation performance of the wafer positioning device in a high vacuum environment.

[0081] The core of the electromagnet 1-1 of the device is a soft magnetic alloy, which fully utilizes the characteristics of high magnetic saturation, high magnetic permeability and low coercive force of the soft magnetic alloy to achieve rapid magnetic conversion and complete the work of pushing the wafer with lower electrical energy, reducing heat generation. Especially in a high vacuum environment, the heat dissipation efficiency of the electromagnet 1-1 is low.

[0082] The device also installs a carrying ring 3-1 at the front end of the carrying column 3-2. The carrying ring 3-1 protrudes outward relative to the carrying column 3-2. The carrying ring 3-1 is preferably a conical ring. There is point contact between the carrying ring 3-1 and the bottom of the wafer, which is beneficial to reduce the friction of the wafer and reduce the heat energy accumulated in the transfer cavity 4.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A precise positioning device for wafer measurement, characterized in that: It includes a driving mechanism, a positioning mechanism and a bearing mechanism installed in the transfer cavity; The driving mechanism is used to push the wafer placed on the carrying mechanism to the positioning mechanism, and the driving mechanism includes a spring, an armature, a push block and an electromagnet. The spring is fixed in the transfer cavity and has a free end for releasing the elastic force, the armature and the push block are assembled on the free end, and an electromagnet fixed in the transfer cavity is arranged on the opposite side of the armature; When the electromagnet is energized, it attracts the armature, causing the spring to deform, and the push block located above the armature pushes the wafer toward the positioning mechanism; The electromagnet releases the armature after power is cut off, and the free end of the spring piece resets the armature and the push block backwards under the action of the elastic restoring force.

2. The precise positioning device for wafer measurement according to claim 1, characterized in that: At least two of the positioning mechanisms are installed on opposite sides of the driving mechanism to position two opposite shoulders of the wafer; The positioning mechanism comprises a positioning seat and a positioning column fixed on the positioning seat, and the top end of the positioning column is a cone.

3. The precise positioning device for wafer measurement according to claim 2, characterized in that: The positioning seat is locked in the transfer cavity by screws. Before being locked, the positioning seat is first rotated to a set position so that the positioning column can abut against the wafer.

4. The precise positioning device for wafer measurement according to claim 1, characterized in that: The driving mechanism further comprises a base, the base is fixed on the bottom wall of the transfer cavity, the electromagnet is mounted on the base; the fixed end of the spring is mounted on the base in an upright position.

5. The precise positioning device for wafer measurement according to any one of claims 1 to 4, characterized in that: The driving mechanism further includes two photoelectric sensors 1 and 2 which are staggeredly installed in the front-to-back direction; A position detection sheet is installed at the free end of the elastic sheet, and the position detection sheet includes a baffle plate 1 and a baffle plate 2 which are sequentially spaced apart in the left-right direction; The baffle plate 1 follows the free end of the spring to move forward to between the photoelectric sensor 1, triggering the photoelectric sensor 1 to send a wafer in place signal; the baffle plate 2 follows the free end to move backward to between the photoelectric sensor 2, triggering the photoelectric sensor 2 to send a reset in place signal.

6. The precise positioning device for wafer measurement according to claim 5, characterized in that: The position detection piece includes a detection piece body installed in a horizontal shape, and the baffle plate 1 and the baffle plate 2 are both vertically fixed below the detection piece body; The photoelectric sensor 1 and the photoelectric sensor 2 are both through-beam sensors.

7. The precise positioning device for wafer measurement according to claim 6, characterized in that: The iron core of the electromagnet and the armature are made of soft magnetic alloy; the push block and the positioning column are made of nylon or Teflon.

8. The precise positioning device for wafer measurement according to claim 5, characterized in that: At least three of the bearing mechanisms are provided to stably support the wafer; The bearing mechanism comprises a bearing seat fixed in the transfer cavity, a bearing column installed on the bearing seat and a bearing ring installed at the front end of the bearing column. The bearing ring protrudes from the bearing column and is in point contact with the wafer.

9. The positioning method of the precise positioning device for wafer measurement according to claim 1, characterized in that: The following steps are involved: The wafer is fed into the transfer chamber and supported by the carrying mechanism; When the electromagnet is energized, it attracts the armature, which drives the push block at the free end of the spring to move, pushing the wafer toward the positioning mechanism until it rests against the positioning column of the positioning mechanism, thereby accurately positioning the wafer. When the electromagnet is powered off, the armature is released, and the armature and the push block return to their initial positions under the elastic force of the shrapnel.

10. The positioning method of the precise positioning device for wafer measurement according to claim 9, characterized in that: After the electromagnet is energized, the position detection sheet moves synchronously with the push block; when the wafer is pressed against the positioning column by the push block, the baffle plate 1 of the position detection sheet enters between the photoelectric sensor 1, thereby judging that the wafer has been moved into position, and at this time, the baffle plate 2 is away from the photoelectric sensor 2; After the electromagnet is powered off, the position detection sheet follows the push block to reset, and the baffle plate 2 enters between the photoelectric sensors 2, thereby judging that the push block is reset in place, and at this time, the baffle plate 1 is away from the photoelectric sensor 1.

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