Wafer carrying platform with wafer flatness detection function and wafer fixing method

Abstract

The invention relates to the technical field of wafer cutting, in particular to a wafer carrying table with a wafer flatness detection function and a wafer fixing method, and the wafer carrying table comprises a bottom plate, a driving device, a flatness detection device, a clamping assembly and a switching valve; the driving device comprises a lifting power assembly and four driving units; each driving unit comprises a driving rack; the flatness detection device comprises a detection body, a pore plate and a conductive disc. The detection body is provided with a groove and an annular air cavity; the conductive disc is arranged in the groove; the pore plate is arranged at the opening of the groove; a detection cavity is defined by the pore plate, the conductive disc and the detection body; an air pipe extends from each hole position of the pore plate; a conductive elastic film is arranged at the tail end of the air pipe; the clamping assembly comprises a bearing ring and four clamping units; the bearing ring is in transmission connection with the lifting power assembly; each clamping unit comprises a clamping arm; the clamping arm is provided with a gear part; and the switching valve is connected with the annular air cavity. According to the invention, flatness detection is carried out on the wafer unit before vacuum adsorption.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer cutting, and in particular to a wafer carrier capable of detecting wafer flatness and a wafer fixing method. Background Art

[0002] In the semiconductor wafer processing process, to ensure stability and accuracy during the cutting process, it is usually necessary to use blue film tape to affix the wafer to the retaining ring before cutting to form a wafer unit. The main function of this operation is to provide stable support for the wafer, preventing displacement or damage during transportation, positioning and cutting, thereby ensuring the smooth progress of subsequent processing steps.

[0003] However, during the actual blue-film tape application process, due to the influence of various factors such as the operating environment, the application force, and the tape tension, it is very easy for raised defects such as bubbles and wrinkles to form between the back of the wafer and the blue-film tape. The existence of these raised defects brings serious potential risks to the subsequent wafer cutting process: if such raised areas are not discovered in time before the wafer is cut, when the wafer is adsorbed onto the cutting table, the raised areas will generate an upward thrust on the wafer. Under the action of the workbench's adsorption force, the wafer is subjected to uneven force, which can cause the wafer to crack at the very least, resulting in the entire wafer being scrapped, directly increasing production costs; in severe cases, due to the certain height of the raised areas, during the wafer cutting process, the high-speed rotating cutting blade will violently collide or rub against the raised areas, which will not only damage the cutting blade, but may also damage the precision components of the wafer cutting machine due to the excessive impact force, thereby affecting the service life and cutting accuracy of the equipment, causing greater economic losses and production delays.

[0004] Therefore, how to effectively detect the flatness of wafer units before wafer cutting has become a technical problem that needs to be solved urgently in the field of semiconductor wafer processing. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a wafer carrier and wafer fixing method that can detect the flatness of the wafer unit before vacuum adsorption, so as to avoid damage to the wafer unit or the cutting machine due to wafer unit flatness problems.

[0006] To achieve the above object, the specific solutions of the present invention are as follows:

[0007] On one hand, the present invention provides a wafer stage capable of detecting wafer flatness, comprising a base plate, a driving device, a flatness detection device, a clamping assembly, and a switching valve;

[0008] The driving device includes a lifting power assembly provided on the bottom plate and four driving units distributed on the bottom plate in a cross shape; each of the driving units includes a driving rack;

[0009] The flatness detection device includes a detection body, an orifice plate, and a conductive disk; the detection body is provided with a groove and an annular air cavity; the conductive disk is disposed in the groove; the orifice plate is disposed at the opening of the groove; the orifice plate, the conductive disk, and the detection body together enclose a detection cavity that is connected to the annular air cavity; each hole of the orifice plate has an air tube extending into the detection cavity; the end of the air tube is provided with a conductive elastic membrane;

[0010] The clamping assembly includes a carrying ring and four clamping units distributed in a cross shape on the carrying ring; the carrying ring is transmission-connected to the lifting power assembly; each clamping unit includes a clamping arm; the clamping arm is provided with a gear portion for cooperating with a drive rack;

[0011] The switching valve is connected to the annular air cavity.

[0012] The present invention further provides that the conductive disk includes a plurality of conductive strips arranged at intervals; each of the conductive strips includes two conductors arranged side by side at intervals; the orifice plate includes a plurality of rows of air hole groups arranged at intervals; the air hole groups are arranged one by one above and below the conductive strips; and an abnormal detection signal is generated when the conductive elastic membrane contacts the two conductors of the corresponding conductive strip.

[0013] Furthermore, the present invention comprises a driving unit and a first spring; the driving rack is vertically slidably arranged on the driving seat; the first spring is arranged on the driving seat; and the two ends of the first spring are respectively in contact with the bottom of the driving seat and the driving rack.

[0014] Furthermore, the present invention provides a limit bar hole vertically extending through the driving seat; a pin is provided on the side wall of the driving rack; and the pin movably extends through the limit bar hole.

[0015] Furthermore, the present invention further comprises a clamping unit and a torsion spring; one end of the clamping arm is hinged on the clamping body; the gear portion is arranged at the end of one end of the clamping arm; the two ends of the torsion spring are respectively connected to one end of the clamping arm and the clamping body; the stiffness of the torsion spring is less than the stiffness of the first spring.

[0016] Furthermore, the present invention provides a clamping block at the other end of the clamping arm.

[0017] Furthermore, the present invention is provided with a limiting arc hole at one end of the clamping arm; and the clamping body is provided with a limiting pin which movably passes through the limiting arc hole.

[0018] The present invention further provides that the lifting power assembly includes a power member, four synchronous wheels distributed in a cross shape on the periphery of the flatness detection device, and a synchronous belt wound around the four synchronous wheels; the power member is in transmission connection with one of the synchronous wheels; a nut is fixedly sleeved at the center of each synchronous wheel;

[0019] A screw is provided on the bottom surface of the bearing ring corresponding to each synchronous wheel; the screw movably passes through the nut.

[0020] The present invention further provides that the switching valve is arranged directly below one of the clamping units; the switching valve includes a valve seat, a valve core and a second spring; the valve seat is provided with a valve cavity and a positive pressure hole and a negative pressure hole respectively connected to the valve cavity; the valve cavity is connected to the annular air cavity through a connecting pipe; the positive pressure hole and the negative pressure hole are arranged at intervals above and below; the lower end of the valve core is movable to penetrate into the valve cavity; the upper end of the valve core is movable upward to penetrate the valve seat; the second spring is arranged in the valve cavity, and the two ends of the second spring are respectively in contact with the lower end of the valve core and the valve seat, so that the valve core remains in an extended state, so that the positive pressure hole is opened and the negative pressure hole is closed at the same time.

[0021] Another aspect of the present invention provides a wafer fixing method using the wafer stage described above, which specifically includes the following steps:

[0022] Clamping and fixing: The lifting power assembly drives the carrying ring to move downward, and the driving rack drives the clamping arm to swing through the gear part. The clamping arm clamps and fixes the wafer unit on the carrying ring;

[0023] Flatness detection: The carrying ring moves further downward until the distance between the bottom surface of the wafer unit and the orifice plate is 1-1.5mm; the switching valve puts the detection chamber in a positive pressure state. If there is a protrusion on the bottom surface of the wafer unit, the conductive elastic membrane at the end of the outlet pipe protrudes downward and abuts against the conductive disk, and the conductive disk generates an abnormal detection signal.

[0024] Vacuum adsorption: If the bottom surface of the wafer unit is flat and has no protrusions, the carrier ring continues to move downward, the switching valve switches the detection chamber to a negative pressure state, and the wafer unit is vacuum adsorbed and fixed on the orifice plate.

[0025] The beneficial effects of the present invention are as follows: the present invention cooperates with the driving unit through the clamping unit to clamp and fix the wafer unit during the downward movement of the wafer unit, and at the same time uses the switching valve to put the detection chamber in a positive pressure state, so that when there is a protrusion on the wafer unit, the outlet pressure in the air outlet of the orifice plate is used to make the conductive elastic membrane protrude downward until it contacts the conductive disk, thereby generating a detection abnormality signal, and when the wafer unit detects that there is no protrusion, the switching valve is used to put the detection chamber in a negative pressure state, so that the wafer unit is vacuum adsorbed on the orifice plate; in this way, the flatness detection of the wafer unit is realized before vacuum adsorption, which is beneficial to avoid damage to the wafer unit or the cutting machine due to wafer unit flatness problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the present invention;

[0027] Figure 2 It is a cross-sectional schematic diagram of the present invention;

[0028] Figure 3 yes Figure 2 A partial enlarged schematic diagram of point A in the middle;

[0029] Figure 4 It is a schematic structural diagram of the present invention when the wafer unit is vacuum-adsorbed;

[0030] Figure 5 is a cross-sectional schematic diagram of the present invention when the wafer unit is vacuum-adsorbed;

[0031] Figure 6 yes Figure 5 A partial enlarged schematic diagram of point B in the middle;

[0032] Figure 7 It is a structural schematic diagram of the clamping assembly of the present invention;

[0033] Figure 8 It is a structural schematic diagram of the clamping unit of the present invention;

[0034] Figure 9 It is a structural schematic diagram of the drive unit of the present invention;

[0035] Explanation of Reference Numerals: 1. Bottom plate; 211. Power member; 2111. Motor; 2112. First gear; 2113. Second gear; 212. Synchronous wheel; 213. Synchronous belt; 214. Nut; 22. Driving unit; 221. Driving seat; 2211. Limiting bar hole; 222. Driving rack; 2221. Pin; 223. First spring; 31. Detection body; 311. Annular air cavity; 32. Orifice plate; 321. Air pipe; 322. Through hole; 33. Conductive disk; 331. Conductive tape; 332. Conductor; 34. Detection chamber; 35. Conductive elastic membrane; 4. Clamping assembly; 41. Carrying ring; 411. Screw; 42. Clamping unit; 421. Clamping body; 422. Clamping arm; 4221. Gear part; 4222. Limiting arc hole; 423. Torsion spring; 424. Clamping block; 425. Limiting pin; 5. Switching valve; 51. Valve seat; 511. Positive pressure hole; 512. Negative pressure hole; 52. Valve core; 53. Second spring; 54. Connecting pipe. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of implementation of the present invention is not limited thereto.

[0037] like Figures 1 to 9As shown, the wafer stage with wafer flatness detection function described in this embodiment includes a base plate 1, a driving device, a flatness detection device, a clamping assembly 4 and a switching valve 5;

[0038] The driving device includes a lifting power assembly provided on the bottom plate 1 and four driving units 22 distributed in a cross shape on the bottom plate 1; each driving unit 22 includes a driving rack 222; the flatness detection device includes a detection body 31, a hole plate 32 and a conductive disk 33; the detection body 31 is provided with a groove and an annular air cavity 311; the conductive disk 33 is provided in the groove; the hole plate 32 is provided at the opening of the groove; the hole plate 32, the conductive disk 33 and the detection body 31 are jointly surrounded to form a hole in the hole 311 and a hole in the hole 311. Detection cavity 34; each hole of the orifice plate 32 has an air tube 321 extending into the detection cavity 34; the end of the air tube 321 is provided with a conductive elastic membrane 35; the clamping assembly 4 includes a carrying ring 41 and four clamping units 42 distributed in a cross shape on the carrying ring 41; the carrying ring 41 is transmission-connected to the lifting power assembly; each clamping unit 42 includes a clamping arm 422; the clamping arm 422 is provided with a gear portion 4221 for mating with the drive rack 222; the switching valve 5 is connected to the annular air cavity 311. The switching valve 5 switches the detection cavity 34 between a positive pressure state and a negative pressure state through the annular air cavity 311. The positions of the four clamping units 42 correspond one-to-one to the positions of the four drive units 22.

[0039] The wafer stage with wafer flatness detection function of this embodiment is initially configured as follows: Figure 1 and Figure 2As shown, the clamping arm 422 is in an open state; the switching valve 5 puts the detection chamber 34 in a positive pressure state through the annular air cavity 311. In actual use, the wafer unit is placed on the carrier ring 41. The wafer unit includes a fixed ring, a blue film fixed in the fixed ring, and a wafer arranged on the top surface of the blue film; the lifting power assembly drives the carrier ring 41 to move downward, and the carrier ring 41 drives the wafer unit and each clamping unit 42 to move downward. After the gear part 4221 of the clamping arm 422 contacts the driving rack 222, the carrier ring 41 moves downward at any time, and the driving rack 222 drives the clamping arm 422 to swing through the gear part 4221 until the clamping arm 422 clamps the wafer unit and fixes it on the carrier ring 41. After the clamping is completed, the clamping arm 422 cannot continue to rotate. As the carrier ring 41 moves further downward, the clamping The arm 422 presses down the drive rack 222 through the gear part 4221, so that the drive rack 222 moves downward synchronously until the distance between the bottom surface of the blue film of the wafer unit and the orifice plate 32 is 1-1.5mm. At this time, if there are bubbles, wrinkles and other protrusions on the bottom surface of the blue film, these protrusions will block the air outlet of the orifice plate 32, so that the area of ​​the air outlet opening corresponding to the protrusion is reduced, and the air outlet pressure of the air outlet is increased. The increased air outlet pressure causes the conductive elastic membrane 35 at the end of the air outlet pipe 321 to protrude downward and abut against the conductive disk 33, so that the conductive disk 33 generates a detection abnormality signal. After receiving the detection abnormality signal, the control system of the wafer cutting machine issues an alarm to notify the staff to handle it.

[0040] If the bottom surface of the blue film is flat and has no protrusions, the control system of the wafer cutting machine will not receive a detection abnormality signal, and the carrying ring 41 will continue to move downward, so that the height of the fixing ring of the wafer unit is lower than the height of the orifice plate 32. At the same time, the switching valve 5 switches the detection chamber 34 to a negative pressure state, thereby vacuum-adsorbing and fixing the wafer unit on the orifice plate 32 to achieve adsorption fixation. Figure 4 and Figure 5 At this time, since the height of the fixing ring is lower than the height of the orifice plate 32, the blue film generates a downward force on the wafer, thereby making the wafer close to the orifice plate 32, so as to ensure stable cutting of the wafer.

[0041] In this embodiment, the clamping unit 42 cooperates with the driving unit 22 to clamp and fix the wafer unit during the downward movement of the wafer unit, and at the same time, the switching valve 5 is used to put the detection chamber 34 in a positive pressure state. When there is a protrusion on the wafer unit, the outlet pressure in the air outlet of the orifice plate 32 is used to make the conductive elastic membrane 35 protrude downward until it contacts the conductive disk 33, thereby generating a detection abnormality signal. When the wafer unit detects that there is no protrusion, the switching valve 5 is used to put the detection chamber 34 in a negative pressure state, so that the wafer unit is vacuum-adsorbed on the orifice plate 32; in this way, the flatness detection of the wafer unit is realized before vacuum adsorption, which is beneficial to avoid damage to the wafer unit or the cutting machine due to wafer unit flatness problems.

[0042] like Figure 2 、 Figure 3 and Figure 5 As shown, in some embodiments of the wafer stage capable of wafer flatness detection, the conductive plate 33 includes a plurality of spaced conductive strips 331; each conductive strip 331 includes two spaced-apart conductors 332; the orifice plate 32 includes multiple rows of spaced-apart pore groups; the pore groups are arranged one above and one below the conductive strips 331; and a detection abnormality signal is generated when the conductive elastic film 35 contacts the two conductors 332 of the corresponding conductive strip 331. With this arrangement, when there are protrusions such as bubbles or wrinkles on the bottom surface of the blue film, the protrusions will block the air outlet holes of the orifice plate 32, reducing the area of ​​the air outlet hole corresponding to the protrusion, thereby increasing the outlet pressure of the air outlet hole. The increased outlet pressure causes the conductive elastic film 35 at the end of the outlet pipe 321 to protrude downward and contact the two conductors 332 of the corresponding conductive strip 331, short-circuiting the two conductors 332 and triggering the detection abnormality signal, thereby achieving wafer unit flatness detection.

[0043] It should be noted that a through hole 322 is provided on the side wall of the air pipe 321 to connect the detection cavity 34 with the air outlet of the orifice plate 32 .

[0044] like Figure 2 、 Figure 6 and Figure 9 As shown, in some embodiments of the wafer stage capable of wafer flatness detection, the drive unit 22 further includes a drive seat 221 and a first spring 223; the drive rack 222 is vertically slidably mounted on the drive seat 221; the first spring 223 is mounted on the drive seat 221; and the two ends of the first spring 223 respectively abut against the bottom of the drive seat 221 and the drive rack 222. The first spring 223 ensures that the drive rack 222 initially protrudes upward. In some embodiments of the wafer stage capable of wafer flatness detection, the clamping unit 42 further includes a clamping body 421 and a torsion spring 423; one end of the clamping arm 422 is hinged to the clamping body 421; the gear portion 4221 is mounted at one end of the clamping arm 422; the two ends of the torsion spring 423 are respectively connected to one end of the clamping arm 422 and the clamping body 421; and the stiffness of the torsion spring 423 is less than that of the first spring 223. The clamping arm 422 is initially in an open state by the torsion spring 423 .

[0045] In actual use, the carrying ring 41 drives each clamping arm 422 to move downward. After the gear portion 4221 of the clamping arm 422 contacts the driving rack 222, as the carrying ring 41 moves further downward, since the stiffness of the torsion spring 423 is less than the stiffness of the first spring 223, the driving rack 222 drives the clamping arm 422 to overcome the torsion force of the torsion spring 423 and swing toward the wafer unit until the clamping arm 422 clamps the wafer unit on the carrying ring 41. After the clamping is completed, since the clamping arm 422 can no longer swing, as the carrying ring 41 moves further downward, the clamping arm 422 presses the driving rack 222 through the gear portion 4221, so that the driving rack 222 overcomes the elastic force of the first spring 223 and moves downward synchronously until the distance between the bottom surface of the blue film of the wafer unit and the orifice plate 32 is h, so as to detect the flatness of the wafer unit;

[0046] When no protrusion is detected, the carrying ring 41 continues to move downward, so that the height of the fixing ring of the wafer unit is lower than the height of the orifice plate 32. At the same time, the switching valve 5 switches the detection chamber 34 to a negative pressure state, thereby vacuum-adsorbing and fixing the wafer unit on the orifice plate 32 to achieve adsorption fixation. Figure 5 At this time, since the height of the fixing ring is lower than the height of the orifice plate 32, the blue film generates a downward force on the wafer, so that the wafer is in close contact with the orifice plate 32 to cut the wafer unit.

[0047] After the cutting is completed, the lifting power assembly drives the carrying ring 41 to move upward. Since the stiffness of the torsion spring 423 is less than the stiffness of the first spring 223, the gear part 4221 of the clamping arm 422 drives the rack 222 to move upward, and the first spring 223 gradually resets. After the first spring 223 resets, the carrying ring 41 drives the clamping arm 422 to continue to move upward, and at the same time the torsion spring 423 resets, causing the clamping arm 422 to swing upward until the gear part 4221 disengages from the driving rack 222, and the torsion spring 423 causes the clamping arm 422 to completely reset.

[0048] like Figure 9 As shown, in some embodiments of the wafer stage with wafer flatness detection function of this embodiment, the drive base 221 is vertically penetrated by a limit bar hole 2211; a pin 2221 is provided on the side wall of the drive rack 222; and the pin 2221 is movably inserted into the limit bar hole 2211. Through this arrangement, the limit bar hole 2211 cooperates with the pin 2221 to limit and guide the drive rack 222, making the movement of the drive rack 222 more stable.

[0049] like Figure 6 and Figure 8As shown, in some embodiments of the wafer stage with wafer flatness detection function of this embodiment, the other end of the clamping arm 422 is provided with a clamping block 424. This arrangement allows the clamping arm 422 to reliably clamp and secure the wafer unit. Preferably, to protect the wafer unit, the clamping block 424 can be made of an elastic material.

[0050] like Figure 8 As shown, in some embodiments of the wafer stage with wafer flatness detection capabilities of this embodiment, a clamping arm 422 is provided with a limit arc hole 4222 at one end, and a clamping body 421 is provided with a limit pin 425 that movably extends through the limit arc hole 4222. Through this arrangement, the limit arc hole 4222 cooperates with the limit pin 425 to limit the swing range of the clamping arm 422, thereby protecting the wafer unit and the torsion spring 423.

[0051] like Figure 1 As shown, the wafer carrier of this embodiment has the function of wafer flatness detection. In some embodiments, the lifting power assembly includes a power piece 211, four synchronous wheels 212 distributed in a cross shape on the periphery of the flatness detection device, and a synchronous belt 213 wrapped around the four synchronous wheels 212; the power piece 211 is transmission-connected to one of the synchronous wheels 212; a nut 214 is fixedly sleeved on the center of each of the synchronous wheels 212; a screw 411 is provided on the bottom surface of the carrying ring 41 corresponding to each synchronous wheel 212; the screw 411 movably passes through the nut 214.

[0052] In actual use, the power member 211 drives the rotation of each synchronous wheel 212 and the synchronous belt 213. Each synchronous wheel 212 drives the corresponding nut 214 to rotate. The nut 214 cooperates with the corresponding screw 411 to drive the carrier ring 41 up and down, achieving stepless adjustment of the wafer unit height and facilitating height control of the wafer unit. The synchronous wheels 212 and the synchronous belt 213 cooperate to ensure the synchronization of the four screws 411 of the carrier ring 41, so that the carrier ring 41 can drive the wafer unit up and down stably and reliably.

[0053] For example, Figure 1 As shown, the power member 211 includes a motor 2111, a first gear 2112, and a second gear 2113. The motor 2111 is mounted on the base plate 1. The first gear 2112 is connected to the output end of the motor 2111. The second gear 2113 is fixed to the end face of one of the synchronous wheels 212. The second gear 2113 meshes with the first gear 2112. Through this arrangement, the motor 2111 drives the first gear 2112 to rotate, the first gear 2112 drives the second gear 2113 to rotate, and the second gear 2113 drives the synchronous wheel 212 to rotate, thereby driving the carrying ring 41 to move up and down.

[0054] like Figure 2 、 Figures 4 to 6 As shown, in the wafer carrier with wafer flatness detection function of this embodiment, in some embodiments, the switching valve 5 is arranged directly below one of the clamping units 42; the switching valve 5 includes a valve seat 51, a valve core 52 and a second spring 53; the valve seat 51 is provided with a valve cavity and a positive pressure hole 511 and a negative pressure hole 512 respectively connected to the valve cavity; the valve cavity is connected to the annular air cavity 311 through a connecting pipe 54; the positive pressure hole 511 and the negative pressure hole 512 are arranged at intervals up and down; the lower end of the valve core 52 is movable to penetrate into the valve cavity; the upper end of the valve core 52 is movable upward to penetrate the valve seat 51; the second spring 53 is arranged in the valve cavity, and the two ends of the second spring 53 are respectively in contact with the lower end of the valve core 52 and the valve seat 51, so that the valve core 52 remains in an extended state, so that the positive pressure hole 511 is opened and the negative pressure hole 512 is closed at the same time.

[0055] Specifically, initially, Figure 2 As shown, the second spring 53 keeps the upper end of the valve core 52 extending out of the valve seat 51, thereby blocking the negative pressure hole 512 and opening the positive pressure hole 511; at this time, the positive pressure hole 511 is connected to the valve cavity, thereby pumping gas into the annular air cavity 311 and the detection cavity 34, and the gas entering the detection cavity 34 is discharged through the various air outlets of the orifice plate 32. When the blue film has a bulge that blocks the air outlet, the air outlet pressure of the air outlet can be increased, so that the conductive elastic membrane 35 protrudes downward to contact the two conductors 332, thereby connecting the two conductors 332 to generate a detection abnormality signal.

[0056] When there is no bulge on the blue film, the carrying ring 41 drives each clamping unit 42 to continue to move downward. Since the switching valve 5 is located directly below one of the clamping units 42, as the clamping unit 42 moves downward, the clamping body 421 will move the valve core 52 downward, so that the valve core 52 overcomes the elastic force of the second spring 53 and shrinks inward, thereby driving the valve core 52 to close the positive pressure hole 511 and open the negative pressure hole 512. At this time, the negative pressure hole 512 is connected to the valve cavity, as shown in FIG. Figure 6 As shown, the annular air cavity 311 and the detection cavity 34 are evacuated through the negative pressure hole 512, thereby vacuum adsorbing the wafer unit; in this way, the flatness detection of the wafer unit is performed before vacuum adsorption, so that the flatness detection and vacuum adsorption are carried out in an orderly manner.

[0057] The above description is only a preferred embodiment of the present invention. Therefore, any equivalent changes or modifications made according to the structure, characteristics and principles described in the scope of the patent application of the present invention are included in the protection scope of the patent application of the present invention.

Claims

1. A wafer stage capable of detecting wafer flatness, characterized in that: It includes a base plate, a driving device, a flatness detection device, a clamping assembly and a switching valve; The driving device includes a lifting power assembly provided on the bottom plate and four driving units distributed on the bottom plate in a cross shape; each of the driving units includes a driving rack; The flatness detection device includes a detection body, an orifice plate, and a conductive disk; the detection body is provided with a groove and an annular air cavity; the conductive disk is disposed in the groove; the orifice plate is disposed at the opening of the groove; the orifice plate, the conductive disk, and the detection body together enclose a detection cavity that is connected to the annular air cavity; each hole of the orifice plate has an air tube extending into the detection cavity; the end of the air tube is provided with a conductive elastic membrane; The clamping assembly includes a carrying ring and four clamping units distributed in a cross shape on the carrying ring; the carrying ring is transmission-connected to the lifting power assembly; each clamping unit includes a clamping arm; the clamping arm is provided with a gear portion for cooperating with a drive rack; The switching valve is connected to the annular air cavity.

2. The wafer stage according to claim 1, wherein: The conductive disk includes multiple conductive strips arranged at intervals; each conductive strip includes two conductors arranged side by side at intervals; the orifice plate includes multiple rows of air hole groups arranged at intervals; the air hole groups are arranged one by one above and below the conductive strips; and a detection abnormality signal is generated when the conductive elastic membrane contacts the two conductors of the corresponding conductive strip.

3. The wafer stage according to claim 1, wherein: The driving unit further includes a driving seat and a first spring; the driving rack is vertically slidably arranged on the driving seat; the first spring is arranged on the driving seat; the two ends of the first spring are respectively in contact with the bottom of the driving seat and the driving rack.

4. The wafer stage according to claim 3, wherein: A limiting strip hole is vertically passed through the driving seat; a pin is provided on the side wall of the driving rack; and the pin movably passes through the limiting strip hole.

5. The wafer stage according to claim 1, wherein: The clamping unit also includes a clamping body and a torsion spring; one end of the clamping arm is hinged on the clamping body; the gear part is arranged at the end of one end of the clamping arm; the two ends of the torsion spring are respectively connected to the one end of the clamping arm and the clamping body; the stiffness of the torsion spring is less than the stiffness of the first spring.

6. The wafer stage according to claim 5, wherein: The other end of the clamping arm is provided with a clamping block.

7. The wafer stage according to claim 5, wherein: One end of the clamping arm is provided with a limiting arc hole; the clamping body is provided with a limiting pin which movably passes through the limiting arc hole.

8. The wafer stage according to claim 1, wherein: The lifting power assembly includes a power member, four synchronous wheels distributed in a cross shape on the periphery of the flatness detection device, and a synchronous belt wrapped around the four synchronous wheels; the power member is connected to one of the synchronous wheels in a transmission manner; a nut is fixedly sleeved at the center of each synchronous wheel; A screw is provided on the bottom surface of the bearing ring corresponding to each synchronous wheel; the screw movably passes through the nut.

9. The wafer stage according to claim 1, wherein: The switching valve is arranged directly below one of the clamping units; the switching valve includes a valve seat, a valve core and a second spring; the valve seat is provided with a valve cavity and a positive pressure hole and a negative pressure hole respectively connected to the valve cavity; the valve cavity is connected to the annular air cavity through a connecting pipe; the positive pressure hole and the negative pressure hole are arranged at intervals up and down; the lower end of the valve core is movable to penetrate into the valve cavity; the upper end of the valve core is movable upward to penetrate the valve seat; the second spring is arranged in the valve cavity, and the two ends of the second spring are respectively in contact with the lower end of the valve core and the valve seat, so that the valve core remains in an extended state, so that the positive pressure hole is opened and the negative pressure hole is closed at the same time.

10. A wafer fixing method using the wafer stage according to any one of claims 1 to 9, characterized in that: The steps include: Clamping and fixing: The lifting power assembly drives the carrying ring to move downward, and the driving rack drives the clamping arm to swing through the gear part. The clamping arm clamps and fixes the wafer unit on the carrying ring; Flatness detection: The carrier ring is further moved downward until the distance between the bottom surface of the wafer unit and the orifice plate is 1-1.5mm. The switching valve puts the detection chamber in a positive pressure state. If there is a protrusion on the bottom surface of the wafer unit, the conductive elastic membrane at the end of the outlet pipe protrudes downward and abuts against the conductive disk, which generates an abnormal detection signal. Vacuum adsorption: If the bottom surface of the wafer unit is flat and has no protrusions, the carrier ring continues to move downward, the switching valve switches the detection chamber to a negative pressure state, and the wafer unit is vacuum adsorbed and fixed on the orifice plate.

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