WO2013143079A1

WO2013143079A1 - Vacuum chuck for electropolishing and/or electroplating

Info

Publication number: WO2013143079A1
Application number: PCT/CN2012/073172
Authority: WO
Inventors: Jian Wang; Yinuo JIN; Yong Shao; Hui Wang
Original assignee: Acm Research (Shanghai) Inc.
Priority date: 2012-03-28
Filing date: 2012-03-28
Publication date: 2013-10-03
Also published as: CN104541367B; CN104541367A

Abstract

The present invention discloses a vacuum chuck for electropolishing and/or electroplating wafers, which includes a supporting assembly having a receiving groove and at least one first vacuum aperture defined in the receiving groove. A seal unit includes a seal ring bulging to form a vacuum trough. The seal ring is fixed in the receiving groove of the supporting assembly and has at least one second vacuum aperture communicating with the first vacuum aperture. A chuck connector fastened with the supporting assembly has at least one vacuum port and at least one vacuum orifice communicating with the vacuum port. At least one vacuum hose connects the first vacuum aperture, the second vacuum aperture with the vacuum orifice and the vacuum port of the chuck connector for evacuating the air of the vacuum trough to hold and position a wafer on the seal ring and the supporting assembly. An electrode connecting with a power supply, a subsidiary metal ring and an insulating ring disposed between the electrode and the subsidiary metal ring are fixed on the supporting assembly and encircle the receiving groove. The diameter of the subsidiary metal ring is smaller than the diameter of the electrode and the subsidiary metal ring is close to the wafer held on the vacuum chuck.

Description

VACUUM CHUCK FOR ELECTROPOLISHING AND/OR

ELECTROPLATING

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention generally relates to a chuck for holding and positioning semiconductor workpieces during various processing procedures, and more particularly relates to a vacuum chuck for electropolishing and/or electroplating the semiconductor workpieces.

2. The Related Art

[0002] In a semiconductor device manufacturing process, semiconductor workpieces such as wafers need to undergo various processing procedures. The polishing process and the plating process are two essential processing procedures for manufacturing the semiconductor device. Besides, as the feature size of the semiconductor device has decreased, the density of interconnections on the semiconductor device has increased. Therefore, the semiconductor industry has started to use copper rather than aluminum to form metal interconnections on the semiconductor device because of copper having greater conductivity than aluminum. A copper layer is formed on the wafer by using an electroplating process and/or etched from the wafer by using an electropolishing process. The wafer is usually held and positioned on a chuck to be electropolished and/or electroplated.

[0003] A vacuum chuck which holds and positions the wafer thereon by vacuum drawing force is disclosed in US patent No.6164633. The vacuum chuck has a generally square body. The body has a first surface and a second opposing surface. The first surface has a first circular platform and a second circular platform for receiving two different diameter wafers. The second surface has a third circular platform for receiving a wafer having a third diameter. A first vacuum trough and a second vacuum trough are respectively formed in the first platform and the second platform. A third vacuum trough is formed in the third platform. Three vacuum passageways are formed and extend from the interior portions of the body to three exterior vacuum ports located at one side of the body. Each vacuum passageway corresponds to a single vacuum trough and links the respective vacuum trough to a vacuum source and so that the air is evacuated from the vacuum trough to hold the wafer on the corresponding platform.

[0004] However, the vacuum chuck described above has at least two disadvantages. One disadvantage of the vacuum chuck is that the vacuum chuck has very weak airtightness, which easily causes the wafer held thereon to come off the vacuum chuck and damage the wafer. The other more important disadvantage of the vacuum chuck is that when the vacuum chuck is used for electropolishing and/or electroplating the copper layer on the wafer, the copper is easy to accumulate on the outer edge of the wafer. When in electropolishing process, the outer edge of the wafer is electropolished more slowly than the portion which is near the center of the wafer, and more seriously, the copper on the outer edge of the wafer is hard to be electropolished. When in electroplating process, the outer edge of the wafer is electroplated more quickly than the portion which is near the center of the wafer. The wafer is electropolished and/or electroplated not evenly. Therefore the copper layer distributed on the wafer is nonuniform, which reduces the precision of the semiconductor device.

SUMMARY OF THE INVENTION

[0005] Accordingly, one aspect of the present invention is to provide a vacuum chuck for electropolishing and/or electroplating wafers more evenly.

[0006] Another aspect of the present invention is to provide a vacuum chuck for holding and positioning wafers thereon stably and securely during the electropolishing process and/or the electroplating process.

[0007] In order to realize the two aspects of the present invention, in an exemplary embodiment, the vacuum chuck includes a supporting assembly having a first receiving groove and a second receiving groove. At least one first vacuum aperture is defined in the first receiving groove. The supporting assembly has a vacuum passageway encircled by the second receiving groove. A first seal unit and a second seal unit are respectively disposed in the first receiving groove and the second receiving groove. The first seal unit includes a first seal ring bulging to form a vacuum trough. The first seal ring is fixed in the first receiving groove of the supporting assembly and has at least one second vacuum aperture communicating with the first vacuum aperture. The second seal unit includes a second seal ring fixed in the second receiving groove. A chuck connector fastened with the supporting assembly has at least one vacuum port and at least one vacuum orifice communicating with the vacuum port. The chuck connector has a vacuum passageway communicating with the vacuum passageway of the supporting assembly for evacuating the air enclosed by the second seal ring and the wafer. At least one vacuum hose connects the first vacuum aperture, the second vacuum aperture with the vacuum orifice and the vacuum port of the chuck connector for evacuating the air of the vacuum trough to hold and position the wafer on the seal rings and the supporting assembly. An electrode connecting with a power supply, a subsidiary metal ring and an insulating ring disposed between the electrode and the subsidiary metal ring are respectively fixed on the supporting assembly and encircle the receiving grooves. The diameter of the subsidiary metal ring is smaller than the diameter of the electrode and the subsidiary metal ring is close to the wafer held on the vacuum chuck.

[0008] As described above, when the vacuum chuck is used for electropolishing and/or electroplating the wafer, electrolyte solution is ejected on the vacuum chuck and the wafer, and a circuit is formed to electropolish and/or electroplate the wafer. Because the subsidiary metal ring encircles the wafer and an interval is formed between the subsidiary metal ring and the wafer, copper accumulates on the subsidiary metal ring rather than the outer edge of the wafer, which eliminates the copper accumulating on the outer edge of the wafer. The wafer is electropolished and/or electroplated evenly, and has a uniform copper layer thereon. Meanwhile, the insulating ring separates the electrode from the outer edge of the wafer, causing the copper on the outer edge of the wafer easily to be electropolished. The wafer is held and positioned on the seal rings and the supporting assembly through vacuum drawing force. Compared to the known vacuum chuck, the vacuum chuck of the present invention holds and positions the wafer more stably and securely. Besides, the first seal ring prevents the electrolyte solution from permeating to the backside of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which:

[0010] FIG. 1 is a top view of a vacuum chuck in accordance with the present invention;

[0011] FIG. 2 is a bottom view of the vacuum chuck;

[0012] FIG. 3 is a top view of a supporting body of the vacuum chuck;

[0013] FIG. 4 is a bottom view of the supporting body of the vacuum chuck;

[0014] FIG. 5 is a top view of a middle plate of the vacuum chuck;

[0015] FIG. 6 is a bottom view of the middle plate of the vacuum chuck;

[0016] FIG. 7 is a top view of a bottom pedestal of the vacuum chuck;

[0017] FIG. 8 is a bottom view of the bottom pedestal of the vacuum chuck;

[0018] FIG. 9 is a cross-sectional view of a supporting assembly assembling with a chuck connector, an electrode, an insulating ring and a subsidiary metal ring of the vacuum chuck;

[0019] FIG. 10 is a cross-sectional view of the vacuum chuck;

[0020] FIG. 11 is another cross-sectional view of the vacuum chuck;

[0021] FIG. 12 is an exploded view of a first seal unit and a second seal unit of the vacuum chuck;

[0022] FIG. 13 is a perspective view of a connecting head of the vacuum chuck;

[0023] FIG. 14 is a perspective view of the chuck connector of the vacuum chuck; and

[0024] FIG. 15 is a cross-sectional view of the chuck connector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] Referring to FIGS. 1 to 11, a vacuum chuck 100 of the present invention will be described in detail with reference to the accompanying drawings. The vacuum chuck 100 is substantially circular. The vacuum chuck 100 includes a supporting assembly 10 and a chuck connector 20 coupled with each other. The supporting assembly 10 includes a supporting body 11, a bottom pedestal 13 and a middle plate 12 disposed between the supporting body 11 and the bottom pedestal 13. The supporting body 11, the middle plate 12 and the bottom pedestal 13 are fastened together through screws in the preferred embodiment. Without doubt, there are other ways to fasten the supporting body 11, the middle plate 12 and the bottom pedestal 13 together.

[0026] The supporting body 11 is in disk-shape and made of insulating material having a character of resisting to corrosion. The supporting body 11 has a body portion 111 and a sidewall 112 protruding downwardly from the edge of the body portion 111. The body portion 111 and the sidewall 112 define a receiving portion 113 to receive the middle plate 12 and the bottom pedestal 13. The center of the body portion 111 defines a circular mating hole 114 wherein the chuck connector 20 is fixed. The body portion 111 defines four locating holes 115 passing therethrough. A top surface of the body portion 111 defines four holding trenches 116. One end of each holding trench 116 communicates with the corresponding locating hole 115, and the other end of each holding trench 116 communicates with the mating hole 114. The four locating holes 115 and the four holding trenches 116 are distributed on the body portion 111 symmetrically. The body portion 111 defines three groups of first wire holes 117. Each group of the first wire holes 117 has two the first wire holes 117. Three wire grooves 118 are arranged on the top surface of the body portion 111. Two opposite ends of each wire groove 118 respectively communicate with one first wire hole 117 of each group of the first wire holes 117.

[0027] The middle plate 12 is made of conducting material and has a first aligning hole 121 at the center thereof. A first vacuum passageway 122 is defined on the middle plate 12 and adjoining the first aligning hole 121. The middle plate 12 has first spindle holes 123 and first fixing holes 124. Preferably, there are three the first spindle holes 123 and three the first fixing holes 124, and the first spindle holes 123 and the first fixing holes 124 are distributed alternately and around the first aligning hole 121 and the first vacuum passageway 122. A top surface and a bottom surface of the middle plate 12 respectively define a circular recess 125 encircling the first aligning hole 121, the first vacuum passageway 122, the first spindle holes 123 and the first fixing holes 124. Two seal members 30 are fixed in the recesses 125 respectively for sealing the juncture place between the middle plate 12 and the chuck connector 20, and the juncture place between the middle plate 12 and the bottom pedestal 13, avoiding the air entering into the vacuum chuck 100. The middle plate 12 defines three second wire holes 126.

[0028] The bottom pedestal 13 is in circular-shape. The bottom pedestal 13 is made of insulating material having a character of resisting to corrosion and has a top surface and a bottom surface holding a wafer which needs to be processed. The top surface of the bottom pedestal 13 defines a hollow portion 130 at the center thereof for receiving the middle plate 12. The bottom surface of the bottom pedestal 13 defines a first receiving groove 131 and a second receiving groove 132. The two receiving grooves 131, 132 are circular and concentric. The diameter of the first receiving groove 131 is greater than the diameter of the second receiving groove 132, which means the first receiving groove 131 is located near the outer edge of the bottom surface of the bottom pedestal 13 and the second receiving groove 132 is located near the center of the bottom surface of the bottom pedestal 13. A plurality of screw holes 133 are defined in the first receiving groove 131 and the second receiving groove 132. The first receiving groove 131 has four first vacuum apertures 134 distributed symmetrically and passing through the bottom pedestal 13. The bottom surface between the first receiving groove 131 and the second receiving groove 132 defines a plurality of interconnected air slots 135. Three pressure releasing holes 140 are symmetrically defined in the air slots 135 for releasing the vacuum drawing force between the first receiving groove 131 and the second receiving groove 132 when the wafer is taken away from the vacuum chuck 100. The center of the bottom pedestal 13 has a second aligning hole 136. A second vacuum passageway 137 is defined and passes through the bottom pedestal 13 and adjoining the second aligning hole 136. Three second spindle holes 138 and three second fixing holes 139 pass through the bottom pedestal 13. The second spindle holes 138 and the second fixing holes 139 are distributed alternately and around the second aligning hole 136 and the second vacuum passageway 137. The second aligning hole 136, the second vacuum passageway 137, the second spindle holes 138 and the second fixing holes 139 are surrounded by the second receiving groove 132. The bottom surface surrounded by the second receiving groove 132 defines a plurality of the air slots 135 communicating with the second vacuum passageway 137. The bottom pedestal 13 has three third wire holes 1311 passing therethrough.

[0029] The vacuum chuck 100 further includes an electrode 200 connecting with a power supply, a subsidiary metal ring 400 and an insulating ring 300 disposed between the electrode 200 and the subsidiary metal ring 400. The electrode 200, the insulating ring 300 and the subsidiary metal ring 400 are fixed on the bottom surface of the bottom pedestal 13 and encircle the first receiving groove 131. The electrode 200, the insulating ring 300, the subsidiary metal ring 400, the first receiving groove 131 and the second receiving groove 132 of the bottom pedestal 13 are concentric. The diameter of the electrode 200 is greater than the diameter of the subsidiary metal ring 400. The outer periphery of the electrode 200 resists against the inner periphery of the sidewall 112 of the supporting body 11. Three wires 500 are provided to electrically connect the electrode 200 and the middle plate 12. The three wires 500 respectively settle in the three wire grooves 118 of the supporting body 11. One end of each wire 500 passes through the first wire hole 117 and the third wire hole 1311 to be fixed with the electrode 200, and the other end of the wire 500 passes through the other first wire hole 117 and the second wire hole 126 to be fixed with the middle plate 12.

[0030] Please refer to FIG. 12 as well as FIGS. 9 to 11. A first seal unit 40 and a second seal unit 50 of the vacuum chuck 100 is illustrated. The first seal unit 40 includes a pair of first metal rings 41 and a first seal ring 42. The middle of the first seal ring 42 bulges to form a vacuum trough 421, and one of the first metal rings 41 is disposed in the vacuum trough 421. The pair of first metal rings 41 and the first seal ring 42 are fixed together through screws, and the first seal ring 42 is disposed between the pair of first metal rings 41. The first seal unit 40 is assembled in the first receiving groove 131 of the bottom pedestal 13 by inserting screws in the screw holes 133. Either of the first metal rings 41 and the first seal ring 42 have four second vacuum apertures 43 corresponding to the four first vacuum apertures 134 of the bottom pedestal 13. The second seal unit 50 includes a pair of second metal rings 51 and a second seal ring 52. The pair of second metal rings 51 are located at both sides of the inner edge of the second seal ring 52. The pair of second metal rings 51 and the inner edge of the second seal ring 52 are fixed together through the screws, and the inner edge of the second seal ring 52 is disposed between the pair of second metal rings 51. The second seal unit 50 is assembled in the second receiving groove 132 of the bottom pedestal 13 by inserting the screws in the screw holes 133. The first seal ring 42 and the second seal ring 52 are made of acid-resisting material.

[0031] With reference to FIG. 13 as well as FIGS. 9 to 10, a connecting head 60 of the vacuum chuck 100 is illustrated. The connecting head 60 is hollow and substantially L-shaped. One end of the connecting head 60 has screw threads and is located in the corresponding first vacuum aperture 134 of the bottom pedestal 13. The other end of the connecting head 60 is substantially cone-shaped and is disposed in the corresponding locating hole 115 of the supporting body 11 to be inserted into a vacuum hose 70 which is received in the holding trench 116 of the supporting body 11. There are four connecting heads 60 and four vacuum hoses 70 to mate with the four first vacuum apertures 134 of the bottom pedestal 13, and the four locating holes 115 and the four holding trenches 116 of the supporting body 11 respectively.

[0032] Please refer to FIGS. 14 to 15 as well as FIGS. 1, 9, 10, 11. The chuck connector 20 defines two parallel elongated vacuum ports 21 on a top surface thereof. A sidewall of the chuck connector 20 defines four vacuum orifices 22. The four vacuum orifices 22 communicate with the two vacuum ports 21 respectively. A bottom surface of the chuck connector 20 defines a third aligning hole 23 at the center thereof. A third vacuum passageway 24 is defined and adjoining the third aligning hole 23 and passes through the chuck connector 20. Three third spindle holes 25 and three third fixing holes 26 are defined on the bottom surface of the chuck connector 20. The third spindle holes 25 and the third fixing holes 26 are distributed alternately and around the third aligning hole 23 and the third vacuum passageway 24. Two elongated seal elements 80 are provided and installed around the vacuum ports 21 for seal function when the chuck connector 20 is coupled with a vacuum source (not shown). The chuck connector 20 is fixed in the mating hole 114 of the supporting body 11 and is fastened with the middle plate 12 and the bottom pedestal 13 through inserting the screws in the first, second and third fixing holes 124, 139, 26. Three spin spindles (not shown) are installed in the first, second and third spindle holes 123, 138, 25. An aligning tool is located in the first, second and third aligning hole 121, 136, 23 for aligning the wafer on the vacuum chuck 100. The chuck connector 20 connects with a power supply to provide electric current to the middle plate 12 and the electrode 20.

[0033] When the vacuum chuck 100 is used for electropolishing and/or electroplating a wafer, the bottom surface of the bottom pedestal 13 contacts with the backside of the wafer. More specifically, the first seal ring 42 contacts with the outer edge part of the backside of the wafer and the air in the vacuum trough 421 is evacuated from the vacuum apertures 43, 134, the connecting heads 60, the vacuum hoses 70, the vacuum orifices 22 and the vacuum ports 21 successively. The second seal ring 52 contacts with the middle part of the backside of the wafer and the air enclosed by the second seal ring 52 and the wafer is evacuated from the air slots 135 and the vacuum passageways 137, 122, 24. Then the wafer is held and positioned on the vacuum chuck 100 stably and securely. Meanwhile, there is an interval between the wafer and the subsidiary metal ring 400. Electrolyte solution is ejected on the vacuum chuck 100 and the wafer, and a circuit is formed to electropolish and/or electroplate the wafer. Because the subsidiary metal ring 400 encircles the wafer, copper accumulates on the subsidiary metal ring 400 rather than the outer edge of the wafer. The wafer is electropolished and/or electroplated evenly, and has a uniform copper layer thereon. Meanwhile, the insulating ring 300 separates the electrode 200 from the outer edge of the wafer, causing the copper on the outer edge of the wafer easily to be electropolished. Besides, the first seal ring 42 has another function of preventing the electrolyte solution from permeating to the backside of the wafer.

[0034] The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.

Claims

WHAT IS CLAIMED IS

1. A vacuum chuck for electropolishing and/or electroplating wafers, comprising: a supporting assembly having a receiving groove and at least one first vacuum aperture defined in the receiving groove,

a seal unit including a seal ring bulging to form a vacuum trough, the seal ring fixed in the receiving groove of the supporting assembly and having at least one second vacuum aperture communicating with the first vacuum aperture,

a chuck connector fastened with the supporting assembly and having at least one vacuum port and at least one vacuum orifice communicating with the vacuum port,

at least one vacuum hose connecting the first vacuum aperture, the second vacuum aperture with the vacuum orifice and the vacuum port of the chuck connector for evacuating the air of the vacuum trough to hold and position a wafer on the seal ring and the supporting assembly,

an electrode connecting with a power supply, the electrode fixed on the supporting assembly and encircling the receiving groove,

a subsidiary metal ring fixed on the supporting assembly and encircling the receiving groove, the diameter of the subsidiary metal ring being smaller than the diameter of the electrode, the subsidiary metal ring being close to the wafer, and

an insulating ring fixed on the supporting assembly and disposed between the electrode and the subsidiary.

2. The vacuum chuck as claimed in claim 1, wherein the seal ring is made of acid-resisting material.

3. The vacuum chuck as claimed in claim 1, wherein the seal unit further comprises a pair of fixing rings, either of the fixing rings has at least one vacuum aperture

corresponding to the second vacuum aperture of the seal ring, one of the fixing rings is disposed in the vacuum trough, the pair of fixing rings and the seal ring are fixed together, which is further fixed in the receiving groove of the supporting assembly, the seal ring is disposed between the pair of fixing rings.

4. The vacuum chuck as claimed in claim 3, wherein the pair of fixing rings are two metal rings.

5. The vacuum chuck as claimed in claim 1, wherein the supporting assembly includes an insulating supporting body and an insulating bottom pedestal, the insulating supporting body has a body portion and a sidewall protruding from the body portion, the body portion and the sidewall define a receiving portion to receive the insulating bottom pedestal, the body portion defines a mating hole, wherein the chuck connector is fixed, and at least one locating hole, a top surface of the body portion defines at least one holding trench, one end of the holding trench communicates with the locating hole, and the other end of the holding trench communicates with the mating hole, the receiving groove and the first vacuum aperture are defined on the insulating bottom pedestal, the first vacuum aperture communicates with the locating hole, and the vacuum hose is located in the holding trench.

6. The vacuum chuck as claimed in claim 5, further comprising a hollow connecting head, one end of the connecting head located in the first vacuum aperture of the insulating bottom pedestal, and the other end of the connecting head disposed in the locating hole of the insulating supporting body to be inserted into the vacuum hose.

7. The vacuum chuck as claimed in claim 6, wherein the connecting head is substantially L-shaped, one end of the connecting head located in the first vacuum aperture of the insulating bottom pedestal has screw threads, and the other end of the connecting head inserted into the vacuum hose is substantially cone-shaped.

8. The vacuum chuck as claimed in claim 5, wherein the insulating bottom pedestal defines a plurality of interconnected air slots encircled by the receiving groove.

9. The vacuum chuck as claimed in claim 8, wherein at least one pressure releasing hole is defined in the air slots.

10. The vacuum chuck as claimed in claim 5, wherein the supporting assembly further includes a conducting middle plate disposed between the insulating supporting body and the insulating bottom pedestal, the middle plate is fastened with the chuck connector connecting with a power supply, the insulating supporting body has at least two first wire holes and at least one wire groove, the conducting middle plate has at least one second wire hole, the insulating bottom pedestal has at least one third wire hole, at least one wire settles in the wire groove, one end of the wire passes through one of the first wire holes and the third wire hole to be fixed with the electrode, and the other end of the wire passes through the other first wire hole and the second wire hole to be fixed with the conducting middle plate.

11. A vacuum chuck for electropolishing and/or electroplating wafers, comprising: a supporting assembly having a first receiving groove and a second receiving groove, at least one first vacuum aperture defined in the first receiving groove, the supporting assembly having a vacuum passageway encircled by the second receiving groove,

a first seal unit and a second seal unit, the first seal unit including a first seal ring bulging to form a vacuum trough, the first seal ring fixed in the first receiving groove of the supporting assembly and having at least one second vacuum aperture communicating with the first vacuum aperture, the second seal unit including a second seal ring fixed in the second receiving groove,

a chuck connector fastened with the supporting assembly and having at least one vacuum port and at least one vacuum orifice communicating with the vacuum port, the chuck connector having a vacuum passageway communicating with the vacuum passageway of the supporting assembly for evacuating the air enclosed by the second seal ring and the wafer,

at least one vacuum hose connecting the first vacuum aperture, the second vacuum aperture with the vacuum orifice and the vacuum port of the chuck connector for evacuating the air of the vacuum trough to hold and position the wafer on the seal rings and the supporting assembly,

an electrode connecting with a power supply, the electrode fixed on the supporting assembly and encircling the first receiving groove and the second receiving groove,

a subsidiary metal ring fixed on the supporting assembly and encircling the first receiving groove and the second receiving groove, the diameter of the subsidiary metal ring being smaller than the diameter of the electrode, the subsidiary metal ring being close to the wafer, and

12. The vacuum chuck as claimed in claim 11, wherein the first receiving groove and the second receiving groove are concentric, and the diameter of the first receiving groove is greater than the diameter of the second receiving groove.

13. The vacuum chuck as claimed in claim 11, wherein the first seal ring and the second seal ring are made of acid-resisting material.

14. The vacuum chuck as claimed in claim 11, wherein the first seal unit further comprises a pair of first fixing rings, either of the first fixing rings has at least one vacuum aperture corresponding to the second vacuum aperture of the first seal ring, one of the first fixing rings is disposed in the vacuum trough, the pair of first fixing rings and the first seal ring are fixed together, which is further fixed in the first receiving groove of the supporting assembly, the first seal ring is disposed between the pair of first fixing rings.

15. The vacuum chuck as claimed in claim 11, wherein the second seal unit further comprises a pair of second fixing rings located at both sides of the inner edge of the second seal ring, the pair of second fixing rings and the inner edge of the second seal ring are fixed together, which is further fixed in the second receiving groove of the supporting assembly, and the inner edge of the second seal ring is disposed between the pair of second fixing rings.

16. The vacuum chuck as claimed in claim 14 or 15, wherein the first fixing rings and the second fixing rings are metal rings.

17. The vacuum chuck as claimed in claim 11, wherein the supporting assembly includes an insulating supporting body and an insulating bottom pedestal, the insulating supporting body has a body portion and a sidewall protruding from the body portion, the body portion and the sidewall define a receiving portion to receive the insulating bottom pedestal, the body portion defines a mating hole, wherein the chuck connector is fixed, and at least one locating hole, a top surface of the body portion defines at least one holding trench, one end of the holding trench communicates with the locating hole, and the other end of the holding trench communicates with the mating hole, the first receiving groove and the second receiving groove are defined on the insulating bottom pedestal, the first vacuum aperture communicates with the locating hole, the vacuum hose is located in the holding trench.

18. The vacuum chuck as claimed in claim 17, further comprising a hollow

connecting head, one end of the connecting head located in the first vacuum aperture, and the other end of the connecting head disposed in the locating hole of the insulating supporting body to be inserted into the vacuum hose.

19. The vacuum chuck as claimed in claim 18, wherein the connecting head is substantially L-shaped, one end of the connecting head located in the first vacuum aperture has screw threads, and the other end of the connecting head inserted into the vacuum hose is substantially cone-shaped.

20. The vacuum chuck as claimed in claim 17, wherein the insulating bottom pedestal between the first receiving groove and the second receiving groove has a plurality of interconnected air slots.

21. The vacuum chuck as claimed in claim 20, wherein at least one pressure releasing hole is defined in the air slots.

22. The vacuum chuck as claimed in claim 17, wherein the insulating bottom pedestal surrounded by the second receiving groove has a plurality of the air slots communicating with the vacuum passageway.

23. The vacuum chuck as claimed in claim 17, wherein the supporting assembly further includes a conducting middle plate disposed between the insulating supporting body and the insulating bottom pedestal, the conducting middle plate is fastened with the chuck connector connecting with a power supply, the insulating supporting body has at least two first wire holes and at least one wire groove, the conducting middle plate has at least one second wire hole, the insulating bottom pedestal has at least one third wire hole, at least one wire settles in the wire groove, one end of the wire passes through one of the first wire holes and the third wire hole to be fixed with the electrode, and the other end of the wire passes through the other first wire hole and the second wire hole to be fixed with the insulating middle plate.

24. The vacuum chuck as claimed in claim 23, wherein the conducting middle plate defines a first vacuum passageway, the insulating bottom pedestal defines a second vacuum passageway, the first and second vacuum passageways communicate with the vacuum passageway of the chuck connector.

25. The vacuum chuck as claimed in claim 24, wherein the conducting middle plate defines a recess on a top surface and a bottom surface thereof, the two recesses respectively encircles the first vacuum passageway, two seal members are fixed in the recesses respectively.

26. The vacuum chuck as claimed in claim 25, wherein the conducting middle plate, the insulating bottom pedestal and the chuck connector respectively have an aligning hole at the center thereof, the aligning hole of the conducting middle plate is encircled by the recesses, the aligning hole of the insulating bottom pedestal is encircled by the second receiving groove, the vacuum passageways of the conducting middle plate, the insulating bottom pedestal and the chuck connector are respectively adjoining the aligning holes.

27. The vacuum chuck as claimed in claim 26, wherein the conducting middle plate, the insulating bottom pedestal and the chuck connector respectively have several fixing holes distributed around the aligning holes and the vacuum passageways.

28. The vacuum chuck as claimed in claim 26, wherein the conducting middle plate, the insulating bottom pedestal and the chuck connector respectively have several spindle holes around the aligning holes and the vacuum passageways.