EP1182007A1

EP1182007A1 - Carrier head with an elastic ring member

Info

Publication number: EP1182007A1
Application number: EP00307093A
Authority: EP
Inventors: Yasuhide c/o Fujikoshi Machinery Corp. Denda; Yoshio c/o Fujikoshi Machinery Corp. Nakamura; Yoshinobu c/o Fujikoshi Machinery Corp Nishimoto
Original assignee: Fujikoshi Machinery Corp
Current assignee: Fujikoshi Machinery Corp
Priority date: 2000-08-18
Filing date: 2000-08-18
Publication date: 2002-02-27

Abstract

A top ring (30) is mounted on a carrier plate (24), in which the workpiece (20) is adhered on a lower face (26), so as to press the workpiece (20) onto the abrasive face (12). A driving mechanism (80) relatively moves the abrasive plate (10) with respect to the top ring (30) so as to abrade the surface (22) of the workpiece (20). A ring groove (32,34) is formed in a lower face (31) of the top ring (30). An elastic ring member (52,54) is fixed on the lower face (31) of the top ring (30) and covering over the ring groove (32,34). The elastic ring member (52,54) is capable of contacting an upper face (25) of the carrier plate (24). A communicating path (66,68) is communicated to a ring chamber (62,64), which is formed between the ring groove (32,34) and the elastic ring member (52,54). A fluid supplying unit (72,74) supplies a fluid to the ring chamber (52,54) and adjusting fluid pressure therein.

Description

The present invention relates to an abrasive machine, more precisely relates to an abrasive machine, which includes: an abrasive plate having an abrasive face for abrading a work piece; a top ring mounted on a carrier plate, in which the work piece is adhered on a lower face, so as to press the work piece onto the abrasive face of the abrasive plate; a driving mechanism relatively moving the abrasive plate with respect to the top ring so as to abrade the surface of the work piece by the abrasive face of the abrasive plate.
These days, semiconductor devices are highly integrated. So flatness and surface quality of silicon wafers, which will be substrates of semiconductor devices, must be highly improved. Further, insulating layers and cable patterns, which are formed on the surface of the wafer, must be abraded highly flat. Thus, abrasive machines are required to highly precisely abrade or polish surfaces of the wafers (work pieces). In other fields too, abrading or polishing work pieces with higher accuracy is required.
In a conventional abrasive machine, an O-ring is provided on a lower face of the top ring, and a weight load is applied to the top ring so as to press the carrier plate onto the abrasive plate. By employing the O-ring, a whole surface of a wafer, which is held by the carrier plate, can be uniformly pressed onto the abrasive face of the abrasive plate.
To uniformly press the carrier plate, the inventor of the present invention invented an improved polishing machine. The improved machine was disclosed in the Japanese Utility Model Gazette No. 4-40848. The improved machine is shown in Fig. 4.
In Fig. 4, wafers 20 are adhered on a lower face of a carrier plate 24. The carrier plate 24 is pressed onto an upper polishing (abrasive) face of a polishing (abrasive) plate 10 by a top ring 30 so as to polish (abrade) lower faces of the wafers 20. A circular contact section 31 is formed in the lower face of the top ring 30. The contact section 31 is capable of pressing an outer edge of the carrier plate 24. On the other hand, a pressing member 80 is provided to an inner center part of the top ring 30 so as to press a center part of the carrier plate 24. The pressing member 80 can be relatively moved close to and away from the top ring 30 by a cylinder chamber 82, which is formed between the top ring 30 and the pressing member 80. The pressing member 30 cannot be detached from the top ring 30. A plurality of weights 40 are mounted on the top ring 30. A fluid supplying unit 84 supplies a fluid to the chamber 82 so as to press the pressing member 80 toward the carrier plate 24.
In the polishing machine, weight loads, which are applied to the outer edge and the center part of the carrier plate 24, can be adjusted and balanced while polishing the wafers 20. Namely, the weight load applying to the outer edge or the center part of the carrier plate 24 can be selectively made greater. Even if inner parts or outer parts of the wafers 20 are polished more, the wafers 20 can be uniformly polished by adjusting fluid pressure in the chamber 82. By adjusting the fluid pressure, the wafers 20 can be polished with high polishing accuracy.
In the polishing machine, a ring groove 86 is formed in a lower face of the circular contact section 31. An O-ring 88 is fitted in the ring groove 86. The O-ring 88 directly contacts an upper face of the carrier plate 24, and the weight load of the top ring 30 is applied to the carrier plate 24. Ring grooves 87 are formed in a lower face of the pressing member 80, and O-rings 89 are respectively fitted in the ring grooves 87. The O-rings 89 too directly contact the upper face of the carrier plate 24, and the weight load of the top ring 30 is applied to the carrier plate 24 via the pressing member 80. By employing the O- rings 88 and 89, the weight load can be uniformly applied to the carrier plate 24, so that the wafers 20 can be polished with high polishing accuracy.
However, when the weight load is partially applied, it is difficult for the O- rings 88 and 89 to uniformly scatter the unbalanced weight load. Even if the O- rings 88 and 89 are partially pressed and deformed, other parts of the O- rings 88 and 89, which are far from the deformed part, are not deformed. Therefore, the wafer 20 cannot be uniformly pressed onto the polishing face, so that polishing accuracy cannot be improved.
Further, it is difficult to fit the O- rings 88 and 89 in the ring grooves 86 and 87 with uniform extended states, so that the polishing accuracy cannot be improved. If the O- rings 88 and 89 are fitted with ununiform extended states, elasticity of the O- rings 88 and 89 are ununiform, so that the O- rings 88 and 89 cannot uniformly press the whole parts of the carrier plate 24 and the polishing accuracy cannot be improved.
Despite a moving stroke of the pressing member 80 is very short, the cylindrical chamber 82 is formed in the top ring 30 and the pressing member 80 can be slid. Namely, the structure must be complex. The pressing member 80 is moved by a piston which is slid in the cylindrical chamber 82, so frictional resistance badly influences the action of the pressing member 80.
The O-ring 88 is fitted in the ring groove 86 of the contact section 81 of the top ring 30, but the O-ring 88 cannot actively adjust the weight load from the top ring 30.
It would be desirable to be able to provide an abrasive machine having a simple structure and which was capable of uniformly applying weight load to a whole surface of a carrier plate and uniformly pressing a whole surface of a work piece so as to increase abrading accuracy.
The abrasive machine of the present invention comprises:
an abrasive plate having an upper face, which is an abrasive face for abrading a work piece;
a top ring being mounted on a carrier plate, in which the work piece is adhered on a lower face, so as to press the work piece onto the abrasive face of the abrasive plate;
a driving mechanism relatively moving the abrasive plate with respect to the top ring so as to abrade the surface of the work piece by the abrasive face of the abrasive plate; and
at least one ring groove being formed in a lower face of the top ring,

for the or each ring groove, an elastic ring member being made of an elastic material, the elastic ring member being fixed on the lower face of the top ring and covering over the ring groove, the elastic ring member being capable of contacting an upper face of the carrier plate;
for the or each ring groove, a communicating path being formed in the top ring, the communicating path being communicated to a ring chamber, which is formed between the ring groove and the elastic ring member; and
fluid supplying means being communicated to the or each communicating path, the fluid supplying means supplying a fluid to the or each ring chamber and adjusting fluid pressure therein.

In the present invention, the fluid is supplied to the ring chamber. In spite of the simple structure, by employing the pressure transmitting fluid, the whole surface of the carrier plate can be uniformly pressed by the top ring and the elastic ring member. Therefore the surface of the work piece can be uniformly pressed onto the abrasive face of the abrasive plate, so that the surface of the work piece can be uniformly abraded and the abrading accuracy can be increased.
In the case that a plurality of fluid supplying units are respectively communicated to the ring chambers, the fluid pressure in the chambers can be respectively adjusted. And the weight load applying to the carrier plate can be partially controlled, so that the abrading accuracy can be further increased.
In the abrasive machines, the elastic ring member may be fixed by screws. With this structure, the elastic ring member, which has a simple shape, can seal securely.
In the abrasive machines, the elastic ring member may have first fitting sections, which are formed along an inner edge and an outer edge, and
the elastic ring member may be fixed by fitting the first fitting sections to second fitting sections, which are formed in the lower face of the top ring. With this structure, the elastic ring member can be easily fitted, so manufacturing efficiency and maintenance efficiency can be improved.
In the abrasive machines, a plurality of the carrier plates may be provided on the abrasive plate with regular angular separations, and
a plurality of the work pieces may be adhered on the lower face of each carrier plate with regular angular separations. With this structure, working efficiency can be improved.
In the abrasive machines, a couple of the elastic ring members may be coaxially provided,
wherein the outer elastic ring member corresponds to outermost parts of the work pieces and the inner elastic ring member corresponds to innermost parts of the work pieces. With this structure, the whole surfaces of the work pieces can be uniformly pressed and the abrading accuracy can be improved.
Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which:
Fig. 1 is a sectional view of the abrasive machine of an embodiment of the present invention;
Fig. 2A is a partial sectional view of the abrasive machine, in which no fluid is supplied into ring chambers;
Fig. 2B is a partial sectional view of the abrasive machine, in which a fluid is supplied into the ring chambers;
Fig. 3 is a sectional view of the abrasive machine of another embodiment; and
Fig. 4 is a sectional view of the conventional abrasive machine.
Fig. 1 is a sectional view of the abrasive machine of an embodiment of the present invention; Figs. 2A and 2B are partial sectional views showing actions of the abrasive machine. The abrasive machine shown in Fig. 1 is a polishing machine, which is capable of simultaneously polishing a plurality of silicon wafers, which will be substrates of semiconductor devices.
An upper face of a polishing plate (abrasive plate) 10 is a polishing face (abrasive face) 12, which polishes wafers 20. In the present embodiment, a polishing cloth is adhered on the upper face of the polishing plate 10 so as to form the polishing face 12.
The wafers 20 are adhered on a lower face 26 of a carrier plate 24. Lower faces 22 of the wafers 20 are pressed onto the polishing face 12 of the polishing plate 10. In the present embodiment, the wafers 20 are adhered on the lower face 26 of the carrier plate 24 by adhesive. Note that, the carrier plate 24 must have high flatness and hardness, so it is made of glass or ceramic.
A top ring 30 is mounted on the carrier plate 24 so as to apply weight load thereto. By applying the weight load to the carrier plate 24, the wafers 20, which have been adhered on the lower face 26 of the carrier plate 24, can be pressed onto the polishing face 12 of the polishing plate 10.
A plurality of weights 40 are piled on the top ring 30 so as to apply the weight load to the carrier plate 24 via the top ring 30.
A driving mechanism 80 relatively moves the polishing plate 10 with respect to the top ring 30, so that the lower faces 26 of the wafers 20 are polished by the polishing face 12 of the polishing plate 10.
In the present embodiment, the driving mechanism 80 includes: a rotary unit for rotating the polishing plate 10;
and a holding unit for rotatably holding the top ring 30. The relative movement is not limited to the rotation, it may be swing motion, reciprocative motion, orbital motion, etc..
A plurality of ring grooves 32 and 34 are coaxially formed in a lower face 31 of the top ring 30, which will contact an upper face 25 of the carrier plate 24. In the present embodiment, the inner ring groove 32 and the outer ring groove 34 are formed, but number of the ring grooves is not limited to two. Three or more ring grooves may be formed.
Even if the number of the ring groove is one, the ring grooves has effects.
A plurality of elastic ring members 52 and 54 are made of an elastic material. The elastic ring members 52 and 54 are fixed on the lower face 31 of the top ring 30. The elastic ring members 52 and 54 respectively cover and seal the ring grooves 32 and 34. The elastic ring members 52 and 54 are capable of contacting the upper face 25 of the carrier plate 24. In the present embodiment, the inner elastic ring member 52 covers and seals the inner ring groove 32; the outer elastic ring member 54 covers and seals the outer ring groove 34. The elastic ring members 52 and 54 are capable of expanding toward the upper face 25 of the carrier plate 24. Contact sections 55 of the elastic ring members 52 and 54 contact the upper face 25 of the carrier plate 24.
In the present embodiment, the elastic ring members 52 and 54 are made of synthetic rubber. Further, other elastic materials and metallic bellows, which are capable of expanding toward the carrier plate 24, can be employed.
The elastic ring members 52 and 54 are fixed on the lower face 31 of the top ring 30 by fixing means 82, e.g., screws. By employing the fixing means 82, the elastic ring members 52 and 54 can securely seal the ring grooves 32 and 34 without being formed into specific forms.
Note that, shapes and structures of the elastic ring members 52 and 54 are not limited to the present embodiment. They are required to air-tightly or liquid-tightly seal the ring grooves 32 and 34 and be capable of expanding toward the carrier plate 24. Of course they must be fixed so as not to detach from the top ring 30.
In another embodiment shown in Fig. 3, the elastic ring members 52 and 54 respectively have first fitting sections 56 and 57. The first fitting sections 56 and 57 are extended from an inner edge and an outer edge of each elastic ring member. The first fitting sections 56 and 57 of each elastic ring member are capable of fitting into second fitting sections 36 and 37, which are formed in the lower face 31 of the top ring 30. By fitting the first fitting sections 56 and 57 to the second fitting sections 36 and 37, the elastic ring members 52 and 54 can be fixed to the lower face 31 of the top ring 30. Note that, in the present embodiment, sectional shapes of the first fitting sections 56 and 57 are formed into dove tails; sectional shapes of the second fitting sections 36 and 37 are formed into dove tail grooves. With this structure, the first fitting sections 56 and 57 can be easily fitted into the second fitting sections 36 and 37 without detaching therefrom. Manufacturing efficiency and maintenance efficiency can be improved.
The elastic ring members 52 and 54 are formed into thin plates. Tubular elastic rings, whose outer faces can contact the upper face 25 of the carrier plate 24, may be employed as the elastic ring members. In this case, inner spaces of the tubular elastic rings act as air bags.
In Figs. 2A and 2B, a plurality of communicating paths 66 and 68 are respectively communicated to ring chambers 62 and 64. The ring chamber 62 is formed between the ring groove 32 and the elastic ring member 52; the ring chamber 64 is formed between the ring groove 34 and the elastic ring member 54.
A plurality of fluid supplying units 72 and 74 are respectively communicated to the communicating paths 66 and 68 so as to respectively control fluid pressure in the ring chambers 62 and 64.
A distributor 70 is connected to mid parts of the communicating paths 62 and 64. By employing the distributor 70, fluid can be continuously supplied to the ring chambers 62 and 64 even if the top ring 30 is rotated.
The fluid supplying units 72 and 74 respectively include means for adjusting the fluid pressure. The adjusting means may be provided to compressors of the fluid supplying units 72 and 74. Further, regulators may be respectively provided to the communicating paths 66 and 68 as the adjusting means.
In the present embodiment, air is used as the fluid, but liquid, e.g., water, oil, may be used as the fluid.
Note that, in the present embodiment, a plurality of the carrier plates 24 are provided on the polishing plate 10 with regular angular separations, and a plurality of the wafers 20 are adhered on the lower face 26 of each carrier plate 24 with regular angular separations. Namely, the abrasive machine is a so-called batch-type polishing machine.
A couple of the elastic ring members 52 and 54 are coaxially provided. The outer elastic ring member 54 is provided to correspond to outermost parts of the wafers 20, which have been circularly provided on the carrier plate 24; the inner elastic ring member 52 is provided to correspond to innermost parts of said wafers 20. Namely, diameters of the elastic ring members 52 and 54 are defined on the basis of positions of the outermost parts and the innermost parts of the circularly arranged wafers 20. With this structure, the whole surfaces of the wafers 20 can be uniformly pressed, and accuracy of abrading wafers 20 can be increased.
The polishing machine further has: an elevator unit (not shown), which is capable of vertically moving the top ring 30 so as to feed and discharge the carrier plates 24, which hold the wafers 20 on the lower faces 26; the weights 40 for pressing the wafers 20 onto the polishing plate 10; and a slurry supplying unit (not shown). They are known units and parts, so explanation will be omitted.
Note that, in the present embodiment, the load is applied to the wafers 20 via the top ring 30 and the carrier plates 24, but the means for applying load is not limited to the weights 40. For example, a hydraulic unit may be employed to press the top ring 30 toward the carrier plates 24.
The polishing machine of the present embodiment is the batch-type machine. But the present invention can be applied to abrasive machine for abrading one work piece.
Successively, the action of the polishing machine will be explained with reference to Figs. 2A and 2B.
In Fig. 2A, the carrier plate 24 is moved to the position shown so as to locate the wafers 20 at prescribed positions on the polishing face 12. The top ring 30, on which the weights 40 are piled, is mounted on the carrier plate 24.
In Fig. 2B, the pressurized fluid (the compressed air) is supplied to the ring chambers 62 and 64 by the fluid supplying units 72 and 74. The fluid pressure is controlled on the basis of the weight of the top ring 30 and the weights 40. The fluid pressure slightly expands the elastic ring members 52 and 54 toward the carrier plate 24, and the top ring 30 presses the carrier plate 24 via the elastic ring members 52 and 54. In this state, the lower face 31 of the top ring 30 is slightly moved away from the polishing face 12 of the polishing plate 10. Namely, the fluid pressure in the ring chambers 62 and 64 are controlled to slightly move the top ring 30 upward.
Since the fluid (compressed air) is supplied to the ring chambers 62 and 64, the weight load is uniformly transmitted to every point of the elastic ring members 52 and 54 due to the Pascal's law. Thus, the elastic ring members 52 and 54 can wholly uniformly press the carrier plates 24.
The elastic ring members 52 and 54 are usually made of synthetic rubber, so their frictional coefficient are great and the top ring 30 is rotated together with the carrier plates 24. On the other hand, friction between the lower faces 22 of the wafers 20 and the polishing face 12 of the polishing plate 10 are small, so that they are relatively slipped and the lower faces 22 of the wafers 20 can be polished.
In this state, the top ring 30 is not suspended. The top ring 30 is merely mounted on the carrier plates 24. Therefore, the top ring 30 can be moved onto the polishing face 12 of the polishing plate 10 together with the carrier plates 24.
The top ring 30 is capable of wholly uniformly pressing the carrier plates 24 with the fluid and the elastic ring members 52 and 54, so that the lower faces 22 of the wafers 20 can be uniformly pressed onto the polishing face 12 of the polishing plate 10. Therefore, in spite of the simple structure, the wafers 20 can be uniformly polished with high polishing accuracy.
Unlike the conventional abrasive machine in which the O-ring is press-fitted in the ring groove, the elastic ring members 52 and 54 are provided to cover over the ring grooves 32 and 34, so they can be easily attached without ununiformly expanding.
Unlike an air bag type machine in which the whole lower face of the top ring is covered with an elastic member and presses the whole surfaces of the carrier plates, the elastic ring members 52 and 54 are fixed on the lower face 31 of the top ring 30 by fixing the inner edges and the outer edges. With this structure, shift of the elastic ring members 52 and 54 can be prevented, so that the surfaces 22 of the wafers 20 can be stably polished.
Capacity of the ring chambers 62 and 64 can be small, so desired fluid pressure can be easily gained by supplying small amount of fluid to the ring chamber 62 and 64. Therefore, a quick responsible machine can be realized. Variation of the fluid pressure can be absorbed, so that the carrier plates 24 can be uniformly pressed.
In the present embodiment, a couple of the ring chambers 62 and 64, which are formed between the ring grooves 32 and 34 and the elastic ring members 52 and 54, are formed, but number of the ring chambers is not limited to two. Even if the number of the ring chamber is one, the effects of the ring chamber can be gained and the polishing accuracy can be improved.
The communicating paths 66 and 68 are respectively connected to the ring chambers 62 and 64, and the fluid supplying units 72 and 74 are respectively communicated to the communicating paths 66 and 68, so that the fluid pressure in the ring chambers 62 and 64 can be respectively controlled. In the present embodiment, two ring chambers 62 and 64 are coaxially formed, so the fluid pressure in the inner ring chamber 62 and the fluid pressure in the outer ring chamber 64 can be independently controlled. Therefore, the weight load applying to the wafers 20 can be partially varied, and abrading conditions can be precisely controlled. Since the fluid pressure in the inner ring chamber 62 and the outer ring chamber 64 can be mutually differed, uneven polishing can be prevented. The fluid pressure in the ring chambers 62 and 64 are controlled on the basis of various polishing conditions, e.g., temperature, so as to polish the wafers 20 with high flatness, high polishing accuracy, etc..
In the present embodiment, the wafers 20 are adhered onto the carrier plates 24 by an adhesive, e.g., wax, but they may be fixed onto the carrier plates 24 by water, vacuum means, etc..
The wafers 20 are polished as the work pieces, but the abrasive machine of the present invention may abrade other wafer-formed work pieces, e.g., glass wafers, crystal wafers.

Claims

An abrasive machine,
comprising:

an abrasive plate having an upper face, which is an abrasive face for abrading a work piece;

a top ring being mounted on a carrier plate, in which the work piece is adhered on a lower face, so as to press the work piece onto the abrasive face of said abrasive plate;

a driving mechanism relatively moving said abrasive plate with respect to said top ring so as to abrade the surface of the work piece by the abrasive face of said abrasive plates, and

at least one ring groove being formed in a lower face of said top ring,

characterised by:

for the or each ring groove, an elastic ring member being made of an elastic material, said elastic ring member being fixed on the lower face of said top ring and covering over said ring groove, said elastic ring member being capable of contacting an upper face of the carrier plate;

for the or each ring groove, a communicating path being formed in said top ring, said communicating path being communicated to a ring chamber, which is formed between said ring groove and said elastic ring member; and

fluid supplying means being communicated to the or each communicating path, said fluid supplying means supplying a fluid to the or each ring chamber and adjusting fluid pressure therein.
The abrasive machine according to claim 1,
wherein the or each elastic ring member is fixed by screws.
The abrasive machine according to claim 1 or claim 2,
wherein the or each elastic ring member has first fitting sections, which are formed along an inner edge and an outer edge, and
the or each elastic ring member is fixed by fitting the first fitting sections to second fitting sections, which are formed in the lower face of said top ring.
The abrasive machine according to any one of claims 1 to 3,
wherein a plurality of carrier plates are provided on said abrasive plate with regular angular separations, and
a plurality of the work pieces are adhered on the lower face of each carrier plate with regular angular separations.
The abrasive machine according to any one of claims 1 to 4
wherein there are two coaxial elastic ring members,

the outer elastic ring member corresponding to outermost parts of the or each work piece, and

the inner elastic ring member corresponding to innermost parts of the or each work piece.
An abrasive machine as claimed in any one of claims 1 to 5 wherein there are a plurality of ring grooves, elastic ring members and communicating paths, there being a plurality of fluid supplying units respectively communicated to said communicating paths, said fluid supplying units supplying fluid to the associated ring chambers and respectively adjusting fluid pressure therein.