JP4119170B2 - Chuck table - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a chuck table that sucks and holds a plate-like object such as a semiconductor wafer.
[0002]
[Prior art]
An integrated circuit such as an IC or LSI is formed on the surface of a semiconductor wafer made of silicon or the like through a number of processes.
[0003]
The semiconductor wafer before the integrated circuit is formed is cut out from the ingot, and then the initial shape is formed by lapping or polishing on both sides of the cut semiconductor wafer, followed by flattening by grinding using a grinding apparatus, and then polishing. By performing the mirror finish, the integrated circuit can be formed.
[0004]
Grinding by the grinding apparatus is performed in a state where the semiconductor wafer is held on the chuck table 50 shown in FIG. The chuck table 50 includes a base 51 and a porous plate 52 fitted to the base 51, and is used while being fixed on a vacuum base 53 shown in FIG.
[0005]
As shown in FIG. 7, the vacuum base 53 is formed with a vacuum hole 54 and a vacuum groove 55 communicating with the vacuum source. Further, as shown in FIG. 6, the base 51 is formed with a suction hole 56 communicating with the vacuum hole 54 and a suction groove 57 communicating with the vacuum groove 55. As shown in FIG. The semiconductor wafer W placed on the porous plate 52 is sucked and held by the suction force supplied to the porous plate 52 from above. Then, the grinding wheel is lowered while rotating and comes into contact with the semiconductor wafer W to perform grinding.
[0006]
[Problems to be solved by the invention]
However, when the semiconductor wafer W is ground as described above, it has been empirically recognized that a slight ring-shaped convex portion 58 is formed on the semiconductor wafer W as shown in FIGS. Yes.
[0007]
The inventors of the present invention have studied that this is because the suction groove 57 is located immediately below the semiconductor wafer W in the conventional chuck table 50 shown in FIGS. In 52a, a slight dent is formed in the portion directly above the suction groove 57, and as shown in an enlarged view in FIG. 8, the semiconductor wafer W is formed with a slight recess 59 in a portion located immediately above the suction groove 57. It has been found that the cause is that it is sucked and held in the applied state.
[0008]
That is, when grinding is performed in this state and the suction of the semiconductor wafer W is released after the grinding is finished, the portion located immediately above the suction groove 57 slightly protrudes to form a ring-shaped convex portion 58, and the flat surface. The accuracy could not be improved. And since this convex part 58 needs to be removed in the polishing performed next, there existed a problem that the polishing process took time.
[0009]
Therefore, when performing planarization by grinding, there is a problem in further improving the planar accuracy by preventing convex portions from being generated.
[0010]
[Means for Solving the Problems]
As a specific means for solving the above problems, the present invention provides a chuck table for sucking and holding a plate-like object, a porous plate having a holding surface that is formed of a porous member and sucks and holds the plate-like object; It is composed of a base having a suction region that supports the plate and transmits a suction force to the porous plate, and the porous plate is a portion of the porous plate other than the region where the plate-like object is placed , In addition, a seal portion that seals a portion other than the back surface, which is the surface opposite to the holding surface of the porous substrate, is formed, and the suction region sucks the back surface of the region where the plate-like object is not placed on the porous plate. A formed chuck table is provided.
[0011]
In addition, the chuck table includes a suction groove formed in a ring shape and a suction hole communicating with the suction groove, a seal portion is made of resin, and a porous plate and a base are made of resin. Is an additional requirement.
[0012]
In the chuck table configured in this way, it has been found that a convex portion in the shape of the suction groove is formed on the plate-like object due to the suction groove formed on the base supporting the porous plate, By forming the suction groove in the region where the plate-like object is not placed, the concave portion is not formed when the plate-like object is sucked and held, so that the plane accuracy can be improved by grinding.
[0013]
In addition, since the area other than the area where the plate-like object is placed and the back surface of the holding surface are sealed with resin to prevent air leakage, it can be manufactured at low cost.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
As an example of an embodiment of the present invention, a chuck table 10 shown in FIG. 1 will be described. The chuck table 10 includes a base 11 and a porous plate 12.
[0015]
A suction groove 13 is formed on the surface of the base 11 along the outer periphery, and a suction hole 14 is formed to penetrate downward from the bottom surface of the suction groove 13. The suction groove 13 and the suction hole 14 form a suction region 15 that transmits a suction force to the porous plate 12.
[0016]
On the other hand, the porous plate 12 is a porous member such as porous ceramics, and the surface constitutes a holding surface 12a for sucking and holding a plate-like object. The porous plate 12 has an outer diameter larger than the outer periphery of the suction groove 13, and is configured to cover the entire suction region 15 and is supported by the base 11 when placed on the base 11. .
[0017]
As shown in FIG. 2, the porous plate 12 is configured so that the region other than the region where the semiconductor wafer is placed and the back surface of the holding surface 12 a are sealed by the seal portion 16 so that there is no air leakage. ing. As the seal portion 16, for example, a resin can be used. The porous plate 12 and the base 11 can be fixed by resin, and in this case, air leakage can be effectively prevented and the manufacturing can be performed at low cost. Other materials may be used as long as they can completely seal a large number of holes formed in the porous plate 12.
[0018]
The chuck table 10 configured as described above is fixed to the vacuum base 17 by screws. The vacuum base 17 is formed with a vacuum hole 18 and a vacuum groove 19 communicating with the suction source. When the chuck table 10 is fixed to the vacuum base 17, as shown in FIG. 3, the vacuum hole 18 and the vacuum groove 19 communicates with the suction hole 14, and the porous plate 12 can be sucked and held by the suction groove 13.
[0019]
When the semiconductor wafer W is placed on the holding surface 12 a of the porous plate 12, the semiconductor wafer W is sucked and held by the suction force transmitted from the suction groove 13 to the porous plate 12. As shown in FIG. 3, in a state where the semiconductor wafer W is sucked and held, the suction region 15 is positioned below the outer peripheral side of the semiconductor wafer W. That is, the suction region 15 is formed in a portion facing the back surface of the region where the semiconductor wafer W is not placed, and is configured to suck the back surface of the region.
[0020]
The chuck table 10 shown in FIGS. 1, 2, and 3 is disposed in the grinding device 20 shown in FIG. 4, for example. The grinding device 20 is a device for grinding the surface of a plate-like object such as a semiconductor wafer, and includes cassettes 21 and 22 for storing the plate-like object, and carrying out of the plate-like object from the cassette 21 or plate to the cassette 22. Loading / unloading means 23 for carrying in objects, a centering table 24 for aligning plate-like objects, first conveying means 25 and second conveying means 26 for conveying plate-like objects, and plate-like objects Three chuck tables 10 that are sucked and held, a turn table 27 that can rotate while supporting the chuck table 10 so as to rotate and revolve, and a first grinding means 28 that grinds a plate-like object held on each chuck table 10. And a second grinding means 29 and a cleaning means 30 for cleaning the plate-like object.
[0021]
The semiconductor wafers W before being ground are stored in a plurality of stages in the cassette 21, and are picked up one by one by the loading / unloading means 23 and placed on the centering table 24. Then, after the alignment of the semiconductor wafer W is performed here, the semiconductor wafer W is attracted to the first transfer means 25 and the first transfer means 25 is pivoted to move the semiconductor wafer to the closest chuck table 10. W is placed.
[0022]
Next, the turntable 27 is rotated by a required angle (120 degrees in this embodiment), and the chuck table 10 on which the semiconductor wafer W is placed is positioned directly below the first grinding means 28. At this time, the chuck table 10 located immediately below the second grinding means 29 is automatically positioned at the position where the chuck table 10 was positioned before the turntable 27 was rotated.
[0023]
The first grinding means 28 and the second grinding means 29 can move up and down with respect to the standing wall portion 31. A pair of rails 32 and 33 are provided in the vertical direction on the inner surface of the wall 31, and ball screws 34 and 35 are disposed. The ball screws 34 and 35 are connected to pulse motors 36 and 37, respectively. It can be rotated by being driven by pulse motors 36 and 37.
[0024]
Nuts (not shown) provided on the first support plate 38 and the second support plate 39 are screwed onto the ball screws 34 and 35, respectively. The support plate 38 and the second support plate 39 are guided by the rails 32 and 33, respectively, and move up and down. A first grinding means 28 is fixed to the first support plate 38, and a second grinding means 29 is fixed to the second support plate 39, and the first grinding is performed by rotating the ball screw 34. The means 28 moves up and down, and the second grinding means 29 moves up and down as the ball screw 35 rotates.
[0025]
In the first grinding means 28, a grinding wheel 42 is mounted on the tip of a spindle 40 having a vertical axis center via a mounter 41, and a grinding wheel 43 for rough grinding is disposed below the grinding wheel 42. It is fixed.
[0026]
On the other hand, in the second grinding means 29, a grinding wheel 46 is attached to the tip of a spindle 44 having a vertical axis center via a mounter 45, and a grinding wheel for finish grinding is provided below the grinding wheel 46. 47 is fixed.
[0027]
When the semiconductor wafer W is positioned directly below the first grinding means 28, the first grinding means 28 descends while the grinding wheel 42 rotates, and the rotating grinding wheel 43 contacts the semiconductor wafer W for rough grinding. Is done.
[0028]
After the rough grinding is finished, the turntable 27 is rotated by a required angle so that the semiconductor wafer W after the rough grinding is positioned directly below the second grinding means 29, and the second grinding means is rotated while the grinding wheel 46 is rotated. 29 is lowered, and the grinding wheel 47 that rotates is brought into contact with the semiconductor wafer W, whereby finish grinding is performed, and the surface of the semiconductor wafer W is flattened with high accuracy.
[0029]
The semiconductor wafer W ground by finish grinding is positioned in the vicinity of the second transport means 26 by the rotation of the turntable 27, and is transported to the cleaning region 30 and cleaned by the second transport means 26, and then carried in and out. The means 23 accommodates the cassette 22. Grinding is performed sequentially as described above, and finally the ground semiconductor wafer W is all stored in the cassette 22.
[0030]
At the time of grinding by the first grinding means 28 and the second grinding means 29, the chuck table 10 rotates and grinding is performed by applying a pressing force while the grinding wheel 43 and the grinding wheel 47 rotate. Unlike the conventional chuck tables shown in FIGS. 6, 7, and 8, in the chuck table 10 shown in FIGS. 1, 2, and 3, the suction region 15 is provided on the outer peripheral side from the region where the semiconductor wafer W is placed. As a result, there is no suction groove immediately below the holding surface 12a, and the semiconductor wafer W is sucked by a uniform suction force. Therefore, when the semiconductor wafer W is sucked and held, the surface becomes flat. Accordingly, since the surface can be ground with a flat surface, ring-shaped convex portions along the suction grooves 13 are not formed even after the suction is released, and the plane accuracy can be improved.
[0031]
In the present embodiment, resin is used to seal a region other than the region on which the semiconductor wafer is placed and the back surface of the holding surface 12a. For example, as shown in FIG. The ring frame 48 may be used to close the frame.
[0032]
Further, it can be applied not only to grinding in wafer making but also to back surface grinding performed after a circuit is formed on the surface. Furthermore, what is sucked and held by the chuck table is not limited to a semiconductor wafer, and may be another plate-like object.
[0033]
【The invention's effect】
As described above, in the present invention, the suction groove formed on the base supporting the porous plate causes a convex portion in the shape of the suction groove to be formed on the plate-like object after grinding. Since the suction groove is formed in the region where the plate-shaped object is not placed, the concave portion is not formed when the plate-shaped object is sucked and held, so that the planar accuracy can be improved by grinding. Therefore, the burden of the subsequent polishing process can be reduced, and the productivity such as wafer making can be improved.
[0034]
In addition, since the area other than the area where the plate-like object is placed and the back surface of the holding surface are sealed with resin to prevent air leakage, it can be manufactured at low cost and is economical.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a chuck table according to the present invention.
FIG. 2 is an exploded perspective view showing the chuck table and a vacuum base.
FIG. 3 is a sectional view showing the chuck table and a vacuum base.
FIG. 4 is a perspective view showing an example of a grinding apparatus on which the chuck table is mounted.
FIG. 5 is a sectional view showing a second example of the chuck table.
FIG. 6 is an exploded perspective view showing a conventional chuck table.
FIG. 7 is an exploded perspective view showing the conventional chuck table and vacuum base.
FIG. 8 is a cross-sectional view showing the conventional chuck table and vacuum base.
FIG. 9 is a plan view showing a semiconductor wafer that has been suction-held and ground by the conventional chuck table;
10 is a cross-sectional view taken along line AA in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Chuck table 11 ... Base 12 ... Porous board 12a ... Holding surface 13 ... Suction groove 14 ... Suction hole 15 ... Suction area 16 ... Seal part 17 ... Vacuum base 18 ... Vacuum hole 19 ... Vacuum groove 20 ... Grinding device 21, DESCRIPTION OF SYMBOLS 22 ... Cassette 23 ... Carrying in / out means 24 ... Centering table 25 ... 1st conveyance means 26 ... 2nd conveyance means 27 ... Turntable 28 ... 1st grinding means 29 ... 2nd grinding means 30 ... Cleaning means 31 ... Walls 32, 33 ... Rails 34, 35 ... Ball screw 36, 37 ... Pulse motor 38 ... First support plate 39 ... Second support plate 40 ... Spindle 41 ... Mounter 42 ... Grinding wheel 43 ... Grinding wheel 44 ... Spindle 45 ... mounter 46 ... grinding wheel 47 ... grinding wheel 48 ... ring frame 50 ... chuck table 51 ... base 52 ... po Alaser plate 53 ... Vacuum base 54 ... Vacuum hole 55 ... Vacuum groove 56 ... Suction hole 57 ... Suction groove 58 ... Convex part 59 ... Concave part

Claims (4)

A chuck table for sucking and holding a plate-like object,
A porous plate formed of a porous member and having a holding surface for sucking and holding a plate-like object;
A base having a suction area for supporting the porous plate and transmitting a suction force to the porous plate;
The porous plate seals a portion of the porous plate other than the region where the plate-like object is placed and other than the back surface, which is the surface opposite to the holding surface of the porous substrate. A sealing part is formed,
The suction table is a chuck table formed so as to suck a back surface of a region of the porous plate where the plate-like object is not placed.   The chuck table according to claim 1, wherein the suction region includes a suction groove formed in a ring shape and a suction hole communicating with the suction groove.   The chuck table according to claim 1, wherein the seal portion is made of resin.   The chuck table according to claim 3, wherein the porous plate and the base are fixed with resin.

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