A positioning device for a wafer

Abstract

The application discloses a positioning device for a wafer, comprising a disc body, an edge of a surface of the disc body is provided with a step for supporting an edge of the wafer, so that a groove is formed on an inner side of the step, a gas inlet hole is arranged at a center of a bottom of the groove, and a negative pressure ring groove is arranged around the gas inlet hole and close to the step, the gas inlet hole is used for inputting gas into the groove to form a gas film so that the wafer is in a gas floating state, and the negative pressure ring groove is configured to provide a negative pressure environment to enhance air tightness between the edge of the wafer and the step; a plurality of clamping components are arranged on the step at intervals in a circumferential direction, the clamping components are configured to be thermal expansion bodies, and the plurality of clamping components clamp the wafer after thermal expansion, and a clamping force of the clamping components is suitable for providing friction force to the wafer in a high-speed rotating state of the disc body so that the wafer rotates synchronously with the disc body. The application has the beneficial effects of reducing damage to the wafer and reducing particles generated in a detection environment.

Description

TECHNICAL FIELD

[0001] The present application relates to a positioning device for a wafer, and belongs to the technical field of precision semiconductor equipment. BACKGROUND

[0002] In the process of the wafer, the positioning device is needed to correspond to the clamping and positioning of the wafer position, so as to correspond to guarantee the stability and accuracy in the detection process, so as to meet the requirements of detection. The existing positioning device synchronously rotates at high speed after positioning the wafer to monitor, the bottom surface of the wafer directly contacts with the disc body of the positioning device during positioning, and then the clamping part is abutted on the top of the edge of the wafer, the clamping part and the disc body clamp the wafer up and down, the direct contact between the disc body and the wafer can cause the wafer surface to be easily damaged, and the clamping part needs to apply enough pressure to the top of the wafer edge to generate enough friction force to maintain synchronous high-speed rotation, therefore, the clamping mode of the clamping part, the direct contact mode of the disc body and the wafer can also cause serious particle dropping, which is not conducive to the detection of the wafer. SUMMARY

[0003] The purpose of the present application is to provide a positioning device for a wafer, which reduces the damage to the wafer and reduces the particles generated in the detection environment.

[0004] The present application is realized by the following technical solutions.

[0005] A positioning device for a wafer, comprising:

[0006] The disc body has a step formed by a protrusion on the edge of the surface of the disc body and used for supporting the edge of the wafer, so that the surface of the disc body is formed with a groove inside the step, the bottom surface of the groove is provided with an air inlet hole at the center, and a negative pressure ring groove around the air inlet hole is provided near the step, the air inlet hole is used for inputting gas into the groove to form an air film so that the wafer is in an air floating state, and the negative pressure ring groove is configured to provide a negative pressure environment to enhance the air tightness between the edge of the wafer and the step;

[0007] A plurality of clamping parts are arranged on the step in a circumferential interval, the clamping parts are configured to be heat expansion bodies, and the plurality of clamping parts clamp the wafer after being heated and expanded, and the clamping force is suitable for providing friction force to the wafer under the high-speed rotation state of the disc body to make the wafer rotate synchronously with the disc body.

[0008] As a further improvement of the present application, it further comprises:

[0009] A plurality of jacking rods are arranged on the step in a circumferential interval, the jacking rods are vertically raised for receiving the wafer during the process of moving the wafer to the disc body for positioning, and the jacking rods are vertically raised for lifting and moving away the wafer after the detection is completed, and the jacking rods are vertically lowered for receiving the wafer from the step after receiving the wafer.

[0010] As a further improvement of the present application, the top surface of the lifting rod has a vertical protrusion formed adjusting column, the adjusting column has a sliding adjusting part facing the wafer edge, and the lifting rod is adapted to receive the wafer, and in the case that the wafer has a horizontal offset, the wafer edge can slide along the sliding adjusting part to the top surface of the lifting rod by the self-weight and correct the horizontal position of the wafer relative to the disc body.

[0011] As a further improvement of the present application, it further comprises:

[0012] A plurality of limiting components are arranged on the step at intervals in the circumferential direction, the limiting component comprises a rotating arm rotatably arranged on the step, a limiting head arranged on the rotating arm, and an elastic member for driving the rotating arm to rotate to a reset state; in the state of the elastic potential of the elastic member, the limiting head and the wafer positioned on the disc body are separated, and in the reset state of the rotating arm, the limiting head and the top of the edge of the wafer positioned on the disc body are in contact, for maintaining the stable air floating state of the wafer in the synchronous high-speed rotating state of the disc body and the wafer.

[0013] As a further improvement of the present application, the limiting component further comprises a housing and a pushing member, the rotating arm, the elastic member and the pushing member are arranged in the housing, the housing has an opening allowing the part of the rotating arm with the limiting head to protrude out, one end of the elastic member is supported on the inner wall of the housing, and the other end supports the pushing member, the pushing member and the rotating arm are in contact, and the pushing member is used to push the rotating arm to rotate.

[0014] As a further improvement of the present application, the part of the limiting head in contact with the wafer is in a spherical shape.

[0015] As a further improvement of the present application, the bottom surface of the groove has a protrusion formed on the inner side of the negative pressure ring groove and is in a ring-closed inner side sealing dam, so that the space between the wafer bottom surface and the groove is divided into an air floating area on the inner side of the inner side sealing dam and a negative pressure area between the step side wall and the inner side sealing dam, and an inner side flow-limiting air resistance passage is formed between the inner side sealing dam and the wafer bottom surface, for improving the flow resistance of the air floating area to the negative pressure area.

[0016] As a further improvement of the present application, the bottom surface of the groove has a protrusion formed on the outer side of the negative pressure ring groove and is in a ring-closed outer side sealing dam, and an outer side flow-limiting air resistance passage is formed between the outer side sealing dam and the wafer bottom surface, for blocking the external atmosphere from flowing into the negative pressure ring groove from between the wafer edge and the step.

[0017] As a further improvement of the present application, the clamping component comprises a base arranged on the step, an active heating layer arranged on the base, and a heat-conducting layer arranged on the active heating layer and heated and expanded by the active heating layer to clamp the wafer edge.

[0018] The beneficial effects of the present application are:

[0019] The arrangement of the air inlet holes avoids scratches, abrasion or contamination that may be caused by the direct contact between the surface of the disc body and the bottom surface of the wafer, greatly protecting the wafer surface integrity, and is particularly suitable for the processing of ultra-precision and fragile wafers. On the other hand, the uniform support of the air film can also reduce the wafer deformation, providing a more flat reference plane for high-precision detection. The arrangement of the negative pressure ring groove effectively blocks the path of gas leakage from the edge, thereby maintaining the stability of the air film pressure. Especially when the disc body rotates at high speed, the centrifugal effect and airflow disturbance caused by rotation can destroy the dynamic stability of the air film, which may lead to uneven distribution of air film pressure or changes in thickness. The additional restraining force provided by the negative pressure adsorption can firmly hold the wafer edge, effectively inhibiting the possible radial drift, float or vibration, and ensuring the positioning accuracy under high-speed working conditions. The arrangement of the clamping component avoids any contact and pressure on the functional area of the wafer, i.e. the top surface, eliminating the risk of micro-cracks, stress or mechanical damage on the wafer surface caused by contact pressure. The clamping force required for lateral clamping only needs to provide sufficient lateral friction to resist the tangential force in rotation, and the required force is usually smaller. The optimized design of the contact area and method can greatly reduce the particulate matter generated by friction, significantly improve the cleanliness of the detection environment, meet the stringent requirements of high-end processes for particle control, and set the clamping component as a thermal expansion body, i.e. the advantages of small action stroke are also suitable for the narrow space at the step in this application scenario. BRIEF DESCRIPTION OF DRAWINGS

[0020] The preferred embodiments of the present application will be described in detail below with the help of the accompanying drawings, which are intended to help understand the purposes and advantages of the present application, in which:

[0021] Figure 1 It is a structural schematic diagram of the positioning device;

[0022] Figure 2 It is a partial sectional view schematic diagram of the positioning device and the part of completing positioning about the jacking rod;

[0023] Figure 3 It is a partial sectional view schematic diagram of the positioning device about the limiting component;

[0024] Figure 4 It is a partial sectional view schematic diagram of the positioning device about the clamping component;

[0025] Figure 5 It is a partial sectional view schematic diagram of the positioning device about the negative pressure ring groove, the inner sealing dam and the outer sealing dam. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below according to the drawings and embodiments.

[0027] The orientation terms mentioned or possibly mentioned in the present specification, such as up, down, left, right, front, back, front side, back side, top, bottom, etc., are defined with respect to the configuration shown in the drawings, and the terms "inner" and "outer" refer to the direction toward or away from the geometric center of a particular component, which are relative concepts, and thus can change accordingly depending on the different positions, different use states, etc. Therefore, these or other orientation terms should not be interpreted as restrictive terms.

[0028] The present embodiment shows a positioning device for wafers, with reference to Figures 1-5 , comprising a disc body 1 and a plurality of clamping components 2. The edge of the surface of the disc body 1 has a raised step 11 formed and used to support the edge of the wafer 5, which is usually supported by a width of 1.5-2.0 mm, and the inner side of the step 11 forms a groove 12 with a flat bottom on the surface of the disc body 1, so as to ensure that a uniform gap is formed between the bottom of the groove 12 and the bottom of the wafer 5, and a gas inlet hole 1a is arranged at the center of the bottom of the groove 12, which is used to input gas into the groove 12 to form a gas film under the wafer 5, so that the wafer 5 is in a stable non-contact air floating state. On the one hand, this avoids the possibility of scratches, wear or contamination caused by direct contact between the surface of the disc body 1 and the bottom of the wafer 5, greatly protecting the surface integrity of the wafer 5, especially suitable for the processing of ultra-precision and fragile wafers 5; on the other hand, the uniform support of the gas film can also reduce the deformation of the wafer 5, providing a more flat reference plane for high-precision detection.

[0029] The part of the bottom of the groove 12 close to the step 11 is provided with a negative pressure ring groove 1b surrounding the gas inlet hole 1a, and the bottom of the negative pressure ring groove 1b is connected with a negative pressure suction channel 1c extending to the outside of the disc body 1, and the negative pressure suction channel 1c is connected with an external negative pressure suction device. The negative pressure ring groove 1b can generate a negative pressure environment in the area corresponding to the bottom of the edge of the wafer 5, and the downward suction force can enhance the air tightness between the edge of the wafer 5 and the step 11, effectively blocking the path of gas leakage from the edge, thereby maintaining the stability of the gas film pressure. Especially when the disc body 1 rotates at high speed, the centrifugal effect and airflow disturbance caused by rotation can destroy the dynamic stability of the gas film, which may lead to uneven distribution of gas film pressure or change in thickness, and the additional restraint force provided by the negative pressure suction can firmly hold the edge of the wafer 5, effectively inhibiting the possible radial drift, float or vibration of the wafer 5, and ensuring the positioning accuracy under high-speed working conditions.

[0030] A plurality of clamping components 2 are arranged on the step 11 in a circumferential interval, and the clamping components 2 are configured as thermal expansion bodies, which, after being heated and expanded, will clamp the edge of the wafer 5 from the circumferential side. This side clamping method is different from the prior art method of pressing from the top to the bottom against the top surface of the wafer 5. First, it avoids any contact and pressure on the functional area of the wafer 5, i.e. the top surface, eliminating the risk of micro-cracks, stress or mechanical damage to the surface of the wafer 5 caused by contact pressure, which is very critical for advanced process wafers 5 that are increasingly thin and fragile. Second, when it is necessary to maintain the synchronous high-speed rotation of the wafer 5 and the disc body 1, the conventional top clamping needs to apply sufficient pressure to obtain sufficient static friction, which is extremely easy to produce debris or particle pollution at the clamping point. The lateral clamping of the present solution only needs to provide sufficient lateral friction to resist the tangential force in rotation, usually requiring less force, and the optimized design of the contact area and method can greatly reduce the particles generated by friction, significantly improve the cleanliness of the detection environment, meet the stringent requirements of high-end processes for particle control, and further reduce the damage to the wafer 5, since the action site is the edge of the wafer 5, not the functional area of the wafer 5, i.e. the top surface. In addition, the selection of thermal expansion as the driving mechanism makes the structure simpler and more compact, with no complex moving parts, high reliability and less likelihood of generating particles. Thermal expansion can provide very uniform and controllable clamping force, which can be fine-tuned by precisely controlling the temperature, with fast response speed and high control accuracy, making it very suitable for wafers 5 as clamping objects. In addition, due to the limited space at the step 11 of the disc body 1, mechanical driving solutions with relatively large action stroke are also not suitable. By setting the clamping components 2 as thermal expansion bodies, the advantage of small action stroke is also suitable for this application scenario.

[0031] In the present embodiment, based on the consideration of automation and reliability of wafer 5 transfer and positioning process, the positioning device further comprises a plurality of jacking rods 3 arranged on the step 11 in a circumferential interval, which can be vertically lifted by the drive arranged below the disc body 1. During the wafer 5 transfer process, the jacking rods 3 are first lifted to a position where the top surface is higher than the step 11 of the disc body 1, at which point the wafer 5 is transferred and placed on the top surface of the lifted jacking rods 3 by the EFEM or special robot, completing the initial receiving; then the jacking rods 3 are lowered to smoothly transfer the wafer 5 to the final support and positioning by the step 11 of the disc body 1. After the detection is completed, the clamping components 2 stop heating and shrink to release the clamping of the wafer 5, and the jacking rods 3 are lifted again to lift the wafer 5 away from the step 11, so that it is free from any clamping or adsorption, so that the robot can take it away. The setting of the jacking rods 3 makes the loading and unloading process of the wafer 5 smooth and accurate, and the jacking rods 3 as an intermediate transition carrier improve the safety and reliability of the operation.

[0032] In this embodiment, in order to further improve the centring accuracy and positioning success rate of the wafer 5 when initially placed, the top surface of the lifting rod 3 has an adjusting column 31 formed by a vertical protrusion, which is usually arranged as a tapered column structure with a gradually decreasing diameter from bottom to top, and the side surface thereof constitutes a sliding adjusting part facing the edge of the wafer 5. When the EFEM or the robot places the wafer 5 onto the lifted lifting rod 3, if there is a deviation in the horizontal direction of the wafer 5, the edge of the wafer 5 will first contact the sliding adjusting part, i.e. the tapered inclined surface, of the adjusting column 31, and under the action of the component force of the gravity of the wafer 5 itself, the edge thereof will naturally slide downward along this sliding adjusting part until it is stably seated on the top surface of the lifting rod 3, thereby automatically correcting the deviation in the horizontal position thereof. This self-centring mechanism is very important, because if the centre of the wafer 5 deviates from the centre of the disc body 1 when it is finally supported on the step 11, firstly, it will cause the contact ring of the edge of the wafer 5 with the step 11 to be uneven, which may cause the local gap to be too large to cause gas leakage, thereby destroying the uniformity and stability of the air film, and even possibly causing the wafer 5 to tilt; secondly, it will also cause the contact condition and clamping force of each clamping part 2 with the edge of the wafer 5 to be inconsistent, which not only affects the rotation synchronism, but also may introduce unnecessary stress. The lifting rod 3 and the adjusting column 31 are usually integrally formed by polyether ether ketone (PEEK), which has a moderate surface resistance of 10^6-10^8Ω, can effectively prevent static electricity from accumulating, and has a relatively low friction coefficient of about 0.25 against silicon, which can not only ensure smooth sliding adjustment of the wafer 5, but also greatly reduce the friction and wear during sliding, almost without generating particulate matter, thereby perfectly meeting the stringent requirements of the semiconductor process on cleanliness.

[0033] In the present embodiment, based on the consideration of the extreme stability of the air floating state under the condition of ultra-high speed rotation, the positioning device further comprises a plurality of limiting components 4 arranged on the step 11 in a circumferential direction. The limiting component 4 comprises a rotating arm 41 rotatably arranged on the step 11, a limiting head 42 arranged on the top of the rotating arm 41, and an elastic member 43 for driving the rotating arm 41 to rotate to a reset state in which the limiting head 42 contacts the wafer 5. When it is necessary to load or unload the wafer 5, a driver outside the disc body 1 can act on the rotating arm 41, generally on the top of the rotating arm 41, to overcome the elastic force and make the rotating arm 41 rotate to a separation state in which the limiting head 42 is away from the wafer 5; and when the loading or unloading is completed, the driver is driven again to make the limiting head 42 contact the wafer 5, at which time the elastic potential energy of the elastic member 43 is released to maintain the reset state of the rotating arm 41. It should be noted that the strength of the negative pressure suction force provided by the negative pressure ring groove 1b should not be too large, because the air film generates upward floating force on the central region of the wafer 5, while the negative pressure generates downward suction force on the edge, and the two directions are opposite. If the negative pressure is too strong, it will cause the wafer 5 to generate excessive static displacement, i.e. deformation, for example, to present a "bowl-shaped" depression, which will seriously affect the detection accuracy; however, when the disc body 1 rotates at an ultra-high speed, the air film itself may not be stable due to centrifugal force, turbulence, etc., and there is still a small leakage risk between the edge of the wafer 5 and the step 11, which may cause the wafer 5 to have a slight upward floating tendency. At this time, the slight contact between the limiting head 42 and the top surface of the wafer 5 is not to provide friction force for driving rotation, but only to serve as a physical limit to provide a very small restraining force to effectively prevent any upward floating tendency of the wafer 5 at high speed, thereby perfectly avoiding the vicious cycle of seal failure and further air leakage due to upward floating, and ensuring the air floating state under extreme working conditions. This light touch limiting method is essentially different from the method of relying on clamping and pressing to provide a large friction force in the prior art.

[0034] In the present embodiment, in order to reduce the particle pollution that may be caused by the limiting component 4, the limiting component 4 further comprises a shell 45 and a pushing member 44. A part of the rotating arm 41, the elastic member 43 and the pushing member 44 are all arranged in the shell 45, and the shell 45 is only provided with an opening at a proper position to allow the part of the rotating arm 41 with the limiting head 42 to protrude out. One end of the elastic member 43 is supported on the inner wall of the shell 45, and the other end supports the pushing member 44, which in turn contacts the rotating arm 41 to transmit the elastic force. This design of completely enclosing the kinematic pair and the elastic element inside can completely isolate the metal debris and particulate matter that may be generated by the rotation of the rotating arm 41, the sliding of the pushing member 44 and the deformation of the elastic member 43 due to friction or impact, inside the shell 45, effectively preventing these pollutants from escaping into the ultra-clean detection environment where the wafer 5 is located, and fundamentally solving the contradiction between the wear of the moving parts and the cleanliness requirement.

[0035] In the present embodiment, the contact interface between the limiting head 42 and the wafer 5 is optimized, and the part of the limiting head 42 in contact with the wafer 5 is designed as a spherical surface. The spherical surface contact can minimize the possible contact area and maintain a point contact state regardless of the change of the contact angle, which significantly reduces the local pressure and friction stress that may be caused to the surface of the wafer 5. In the process of high-speed rotation, the spherical surface design with low contact area can also effectively reduce the sliding friction, thereby minimizing the particles and damage caused by the contact. The limiting head 42 is usually made of the same polyether ether ketone (PEEK) material as the lifting rod 3, which ensures excellent performance.

[0036] In the present embodiment, in order to strengthen the stability of the negative pressure area r2, a raised and annularly closed inner sealing dam 121 is arranged on the bottom surface of the groove 12, inside the negative pressure ring groove 1b. The inner sealing dam 121 divides the space between the bottom surface of the wafer 5 and the bottom surface of the groove 12 into two areas: an air floating area r1 inside the inner sealing dam 121 and a negative pressure area r2 between the sidewall of the step 11 and the inner sealing dam 121. A very small gap is reserved between the top end of the inner sealing dam 121 and the bottom surface of the wafer 5, forming a narrow inner flow-limiting air resistance passage d1. The inner flow-limiting air resistance passage d1 generates a very high flow resistance to the gas flowing from the central air floating area r1 to the peripheral negative pressure area r2, greatly limiting the flow of gas leaking into the negative pressure ring groove 1b. This enables the negative pressure air extraction device to establish and maintain a more stable negative pressure environment in the negative pressure ring groove 1b with higher efficiency, thereby achieving a stronger edge adsorption sealing effect with smaller air extraction power consumption. Therefore, the negative pressure air extraction device can be selected as a small power type as much as possible, which is beneficial to the installation in the relatively narrow space below the disc body 1.

[0037] In the present embodiment, in order to isolate external atmospheric interference and further improve the stability of the negative pressure area r2, a raised and annularly closed outer sealing dam 122 is arranged on the bottom surface of the groove 12, outside the negative pressure ring groove 1b. A narrow outer flow-limiting air resistance passage d2 is also formed between the top end of the outer sealing dam 122 and the bottom surface of the wafer 5. The outer flow-limiting air resistance passage d2 greatly increases the flow resistance of the external environment air flowing into the negative pressure ring groove 1b from the gap between the edge of the wafer 5 and the step 11, effectively blocking the interference of external air pressure fluctuations on the negative pressure environment in the negative pressure ring groove 1b like a barrier, ensuring the reliability and stability of the negative pressure adsorption effect.

[0038] In the embodiment, the clamping component 2 comprises a base 21 arranged on the step 11, which is preferably made of a heat-insulating material such as alumina with poor thermal conductivity to prevent heat from spreading to the inside of the disc body 1. The base 21 is provided with an active heating layer 22, which can be embedded with a micro-thick-film heating circuit precisely made by etching process. The principle is similar to that of an electric blanket, which has the advantages of fast heating and cooling speed, small thermal inertia, high temperature control precision, long service life, etc. The active heating layer 22 is provided with a heat-conducting layer 23 made of a high-thermal-conductivity material such as oxygen-free copper alloy to ensure that heat can be quickly and uniformly transmitted to the entire contact surface of the wafer 5 edge, thereby providing uniform and consistent clamping force. In addition, a thin-film piezoresistive sensor can also be embedded in the active heating layer 22 to monitor the pressure on the clamping surface in real time, providing a feedback signal for the closed-loop precise control of the clamping force to ensure that the clamping process is safe and reliable and will not be overloaded.

[0039] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present application, and are not limited thereto. Although the present application has been described in detail with reference to the foregoing implementation cases, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing implementation cases or make equivalent replacements for some of the technical features, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present application.

Claims

1. A positioning device for a wafer (5), characterized in that The application relates to a wafer supporting device, which comprises: a disc body (1), the edge of the surface of the disc body (1) is provided with a step (11) for supporting the edge of a wafer (5), the surface of the disc body (1) is provided with a groove (12) in the inner side of the step (11), the bottom of the groove (12) is a plane, the gap between the bottom of the groove (12) and the bottom of the wafer (5) is uniform, the center of the bottom of the groove (12) is provided with an air inlet hole (1a), the part close to the step (11) is provided with a negative pressure ring groove (1b) surrounding the air inlet hole (1a), the air inlet hole (1a) is used for inputting air into the groove (12) to form an air film so that the wafer (5) is in an air floating state, and the negative pressure ring groove (1b) is configured to provide a negative pressure environment to enhance the air tightness between the edge of the wafer (5) and the step (11); a plurality of clamping components (2) are arranged on the step (11) at intervals in the circumferential direction, the clamping components (2) are configured to be thermal expansion bodies, and the plurality of clamping components (2) clamp the wafer (5) after thermal expansion, and the clamping force is suitable for providing friction force to the wafer (5) in a high-speed rotating state of the disc body (1) to make the wafer (5) rotate synchronously with the disc body (1).

2. The positioning device of claim 1, wherein, Further comprising: a plurality of jacking rods (3) are arranged on the step (11) at intervals in the circumferential direction, the jacking rods (3) are vertically lifted to receive the wafer (5) in the process of moving the wafer (5) to the disc body (1) for positioning, and the jacking rods (3) are vertically lowered to receive the wafer (5) after the wafer (5) is received.

3. The positioning device of claim 2, wherein, The top surface of the jacking rod (3) is provided with an adjusting column (31) which is vertically protruded, the adjusting column (31) has a sliding adjusting part which faces the edge of the wafer (5), and in the case that the wafer (5) is offset in the horizontal direction when the jacking rod (3) receives the wafer (5), the edge of the wafer (5) can slide along the sliding adjusting part to the top surface of the jacking rod (3) and correct the position of the wafer (5) relative to the disc body (1) in the horizontal direction by the action of the self weight.

4. The positioning device of claim 1, wherein, Further comprising: a plurality of limiting components (4) are arranged on the step (11) at intervals in the circumferential direction, the limiting components (4) comprise a rotating arm (41) which is rotatably arranged on the step (11), a limiting head (42) which is arranged on the rotating arm (41), and an elastic member (43) which is used for driving the rotating arm (41) to rotate to a reset state; in the state of the elastic member (43) having elastic potential, the limiting head is separated from the wafer (5) which is positioned on the disc body (1), in the reset state of the rotating arm (41), the limiting head (42) is in contact with the top of the edge of the wafer (5) which is positioned on the disc body (1), and the limiting head (42) is used for maintaining the stable air floating state of the wafer (5) in the high-speed rotating state of the disc body (1) and the wafer (5).

5. The positioning device of claim 4, wherein, The limiting part (4) further comprises a housing (45) and a pushing member (44), the rotating arm (41), the elastic member (43) and the pushing member (44) are all arranged in the housing (45), the housing (45) has an opening allowing the rotating arm (41) to have the limiting head (42) partially protruding, one end of the elastic member (43) is supported on the inner wall of the housing (45), the other end supports the pushing member (44), the pushing member (44) is in contact with the rotating arm (41) for pushing the rotating arm (41) to rotate.

6. The positioning device of claim 5, wherein, The part of the limiting head (42) in contact with the wafer (5) is spherical.

7. The positioning device of claim 1, wherein, The bottom surface of the recess (12) has a protrusion formed on the inner side of the negative pressure ring groove (1b) and is annularly closed to form an inner side sealing dam (121), so that the space between the bottom surface of the wafer (5) and the recess (12) is divided into an air floating area (r1) on the inner side of the inner side sealing dam (121) and a negative pressure area (r2) between the sidewall of the step (11) and the inner side sealing dam (121), an inner side flow limiting air resistance passage (d1) is formed between the inner side sealing dam (121) and the bottom surface of the wafer (5) for improving the flow resistance of the air floating area (r1) to the negative pressure area (r2).

8. The positioning device of claim 1, wherein, The bottom surface of the recess (12) has a protrusion formed on the outer side of the negative pressure ring groove (1b) and is annularly closed to form an outer side sealing dam (122), an outer side flow limiting air resistance passage (d2) is formed between the outer side sealing dam (122) and the bottom surface of the wafer (5) for blocking the external atmosphere from flowing into the negative pressure ring groove (1b) from the edge of the wafer (5) and the step (11).

9. The positioning device of claim 1, wherein, The clamping part (2) comprises a base (21) arranged on the step (11), an active heating layer (22) arranged on the base (21), and a heat conducting layer (23) arranged on the active heating layer (22) and heated and expanded by the active heating layer (22) to clamp the edge of the wafer (5).

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