JP4169432B2 - Workpiece holder, polishing apparatus, and polishing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a workpiece holder that holds a workpiece when polishing the workpiece, a polishing apparatus that polishes the workpiece, and a polishing method that polishes the workpiece, and in particular, a semiconductor device manufacturing process The present invention relates to a wafer holder that holds a wafer when polishing the wafer, a polishing apparatus that polishes the wafer, and a polishing method that polishes the wafer.
[0002]
[Prior art]
Polishing of a wafer in a semiconductor device manufacturing process is usually performed by bringing a rotating polishing pad into contact with the wafer surface. The wafer to be polished is held by the wafer holder of the polishing apparatus, but the wafer must be securely held by the wafer holder so as to be able to resist a large impact caused by the rotational movement of the polishing pad. Further, the surface to be polished of the wafer must be finished with high accuracy, and particularly good flatness is required.
[0003]
In order to securely hold the wafer on the surface of the wafer holder and to polish the wafer uniformly within the wafer surface, it is necessary to fit the wafer so as to be surrounded by a ring-shaped retainer provided on the wafer holder. It has been broken.
[0004]
[Problems to be solved by the invention]
As shown in FIG. 5, according to the wafer holder 42 attached to the polishing apparatus as described above, the wafer 43 placed on the suction plate 49 is surrounded by the ring-shaped retainer 50 of the wafer holder 42. It is fitted inside. At this time, there is an annular groove 54 having a width of several millimeters between the retainer 50 and the wafer 43, and when the polishing process is performed by applying a load to the polishing pad 44 and pressing it against the wafer 43, the polishing pad 44 may be drooped 44 </ b> A. is there. In this case, a large stress is applied to the outer peripheral portion 43B of the wafer 43 as compared with other portions, the polishing rate of the outer peripheral portion 43B of the wafer 43 is increased, and the polishing uniformity of the processed surface of the wafer 43 is deteriorated. In FIG. 5, the bending of the slant 44 </ b> A on the lower surface of the polishing pad 44 is drawn larger than the actual one for the sake of easy understanding (the same applies to FIGS. 2 and 3).
[0005]
Therefore, the present invention provides a workpiece holder that can improve the uniformity of polishing of a processed surface of a workpiece such as a wafer, a polishing apparatus equipped with the workpiece holder, and a processed surface of the workpiece. An object of the present invention is to provide a workpiece polishing method capable of improving flatness.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a workpiece holder according to the present invention is a workpiece holder provided with a workpiece holding portion in a portion surrounded by a retainer through a groove, the holding tool. The central part of the holding part provided with a plurality of holes communicating with the vacuum line connected to the vacuum exhaust device as the inner region of the central part of the part is provided at the center and the periphery of the center, and protrudes vertically upward from the shoulder surface of the holding part The holding part outer peripheral part as an annular region of the peripheral part of the holding part is made of a material having a lower elastic coefficient than the holding part central part, and is attached on the holding part central part and the holding part outer peripheral part , A plurality of suction grooves are formed immediately above the central portion of the holding portion, and a suction plate provided with holes corresponding to the holes in the central portion of the holding portion is provided at the bottom of the suction groove .
[0007]
Since the rigidity of the annular region in the peripheral part of the work holding part is smaller than the rigidity of the inner region of the central part, the groove between the retainer and the work piece is used for the polishing pad. Even when the surface sagging occurs and the pressure applied to the outer periphery of the work piece is high, this region deforms when a compression force is applied due to its low rigidity (high elasticity), so this increase in pressure is absorbed. It is possible to suppress the outer peripheral portion of the workpiece from being excessively polished.
[0008]
The magnitude of the rigidity here is determined from the overall rigidity (elasticity) of the workpiece holding part when it is formed of a plurality of layers.
[0010]
Since the annular region of the peripheral part of the workpiece holding part is formed to be inclined to the outside, the groove between the retainer and the workpiece causes a surface sag in the polishing pad. When the pressure applied to the outer peripheral portion increases, the workpiece can bend in accordance with the inclination of this region, and the increase in the pressure is absorbed to prevent the outer peripheral portion of the workpiece from being excessively polished. be able to.
[0011]
The polishing apparatus of the present invention is relatively a retainer of the workpiece described above, a polishing pad for polishing a workpiece held by the holding member, wherein the retainer of the workpiece and the polishing pad A rotation drive unit that rotates, a pressing drive unit that presses the polishing pad relative to the workpiece held by the holding unit, a workpiece held by the holding unit, and the polishing pad; it shall be the characterized and a polishing slurry supply unit for supplying a polishing slurry between.
[0012]
Since the workpiece holder of the present invention is provided, excessive polishing of the outer peripheral portion of the workpiece can be prevented, and the workpiece can be uniformly polished. When the workpiece holder and the polishing pad are relatively rotated, this means that either or both of the workpiece holder and the polishing pad on which the workpiece is placed are rotated. is doing.
[0013]
The polishing method of the present invention, the retainer of the workpiece described above, the polished surface to be polished is holding a workpiece so as to face the polishing pad, between the workpiece and the polishing pad A polishing slurry is supplied, and the surface to be polished is polished with the polishing pad by rotating relatively while pressing the polishing pad against the workpiece.
[0014]
Since the workpiece holder of the present invention is provided, excessive polishing of the outer peripheral portion of the workpiece can be prevented, and the workpiece can be uniformly polished.
[0016]
Since the workpiece is bent in a direction in which the peripheral portion of the surface to be polished is separated from the polishing pad while the central portion of the surface to be polished is held substantially flat, polishing is performed due to the groove between the retainer and the workpiece. Even when the pad is bent and the pressure applied to the outer periphery of the workpiece increases, this bending absorbs the increase in pressure and suppresses excessive polishing of the outer periphery of the workpiece. be able to.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the mutually same or equivalent member, and the overlapping description is abbreviate | omitted. Although the case where the workpiece is an 8-inch wafer will be described here as an example, if the wafer size is different, such as 6 inches or 12 inches, the size of the holder may be changed accordingly.
[0018]
FIG. 1 is a schematic diagram showing a first embodiment of a wafer holder as a workpiece holder according to the present invention. FIG. 1A is a schematic cross-sectional view of the wafer holder 2 showing a state where the wafer 3 is placed, and FIG. 1B shows a wafer holder 2 where the wafer 3 is not placed. FIG. FIG. 1A is a cross-sectional view taken along the line II in FIG.
[0019]
The wafer holder 2 is made of ceramics such as alumina or metal such as stainless steel, and has a substantially cylindrical shape with a circle diameter of 240 mm to 260 mm.
A holding part 5 having a diameter of 200 mm is formed on the upper surface of the wafer holder 2 so as to have the same center as the outer peripheral circle forming the upper surface, and protrudes upward in the vertical direction by about 5 mm from the holding part shoulder surface 5A. Since the holding portion outer peripheral portion 6 as an annular region around the holding portion 5 is made of a material having a lower elastic coefficient than the holding portion central portion 7 as an inner region of the holding portion central portion, the rigidity is low. As this material, silicon rubber, polyurethane rubber, or the like whose hardness can be freely changed in the range of 40 to 90 degrees (hardness in accordance with JIS-K6301) may be used. The holding portion central portion 7 is formed from the material of the wafer holder 2 described above. The width of the outer peripheral portion of the annular holding portion is desirably 10 mm or less. The holding surface of the wafer holder means a surface that comes into contact with the wafer of the holding portion of the wafer holder. However, when the suction plate is attached as will be described later, it refers to the surface of the suction plate that contacts the wafer.
[0020]
A ring-shaped retainer 10 made of a material such as Al 2 O 3 (alumina), SiO 2 (quartz), or SiC is provided so as to surround the holding portion via a groove 14 having a width of 0.5 mm to 3 mm. The retainer 10 is lapped or ground on the upper and lower surfaces in the vertical direction, and is mounted on the holding portion shoulder surface 5A of the wafer holder 2 by a method such as vacuum suction, screw fixing, stopper fixing or the like.
[0021]
On the holding part central part 7 and the holding part outer peripheral part 6, an adsorption made of a resin such as acrylic in which a number of suction grooves 8 are formed concentrically or radially in a portion corresponding to the part directly above the holding part central part 7. A plate 9 is attached with an adhesive. The suction groove 8 is formed in a spiral shape. However, the outermost peripheral portion of the suction groove 8 has an annular shape, and the space forming the groove is closed in the horizontal direction. The suction groove 8 is provided in a portion corresponding to the inner side of the orientation flat of the wafer 3, that is, a portion corresponding to a position directly above the central portion of the holding portion as described above. As a result, when the wafer 3 is placed on the suction plate 9, the entire suction groove 8 is covered with the wafer 3 from above, and when the vacuum suction is performed, the vacuum does not leak and the wafer 3 is stabilized. Retained.
[0022]
In addition, a plurality of holes 11 (five in total in FIG. 1B) are provided at the center of the suction plate 9 and the bottom of the suction groove 8 around the center, and these holes 11 are vacuums provided in the wafer holder 2. It communicates with the line 12. The vacuum line 12 is connected to a vacuum exhaust device (not shown).
[0023]
When the wafer 3 is placed on the wafer holder 2 configured as described above and evacuated from the vacuum line 12, the wafer 3 is vacuum-sucked to the suction plate 9. The polishing pad 4 is pressed against the wafer 3 while supplying the polishing slurry between the polishing pad 4 and the wafer 3 and rotating the polishing pad 4 and the workpiece holder 2 with each other. Then, the polishing pad 4 polishes the wafer 3 while the polishing pad 4 is in contact with the wafer 3 and the retainer 10.
[0024]
FIG. 2 is a schematic diagram showing the holding portion outer peripheral portion 6 of the wafer holder 2 when the polishing pad 4 is pressed in the present embodiment.
[0025]
The polishing pad 4 pressed against the upper surface of the retainer 10 and the upper surface of the wafer 3 placed on the holding unit 5 causes dripping at this portion due to the groove 14 between the retainer 10 and the holding unit 5, and the vertical direction. Although the outer peripheral portion 3B and the holding portion outer peripheral portion 6 of the wafer are made of a material having a lower elastic coefficient than that of the holding portion central portion 7, the outer peripheral portion 3B of the wafer and the holding portion outer peripheral portion 6 are to be bent downward in the direction. Can be easily bent according to the pressure of the polishing pad 4, absorbs the above-mentioned sludge, and prevents the lower surface 4B of the polishing pad from adhering to the wafer 3 and excessive polishing of the outer peripheral portion 3B.
[0026]
Note that the rigidity of the holding portion outer peripheral portion 6 is desirably determined such that when the polishing pad 4 is pressed, the surface of the suction plate causes a deflection of several μm to several tens of μm at the outermost peripheral portion.
Further, in the first embodiment described above, the suction groove may be directly processed in the holding unit 5 without attaching the suction plate 9 in which the suction groove is processed to the upper surface of the holding unit 5.
[0027]
FIG. 3 is a partial cross-sectional view of a wafer holder showing a second embodiment of a wafer holder as a workpiece holder according to the present invention. The holding portion central portion 7 is an area where the suction groove (not shown) is formed with a horizontal and flat surface, and the holding portion outer peripheral portion 6 is uniformly formed with an inclination toward the outside. The wafer holding part 2 which is an area not formed will be described. In the present embodiment, the suction plate is not attached on the holding unit 5, but it is also possible to attach the suction plate. In this case, the holding portion outer peripheral portion 6 may be inclined at a portion corresponding to the suction plate directly above the holding portion outer peripheral portion 6, and when the suction plate has a predetermined elasticity, the holding portion outer peripheral portion Only 6 may be provided with an inclination.
[0028]
The shape of the inclination is determined so that the polishing pad lower surface 4B is in close contact with the wafer 3 and the pressing pressure by the polishing pad is constant. Therefore, even if the groove 14 between the retainer 10 and the outer peripheral edge 3 </ b> A of the wafer 3 sags on the polishing pad lower surface 4 </ b> B, the polishing pad lower surface 4 </ b> B is absorbed by the inclination of the holding portion outer peripheral portion 6. It is possible to make the polishing rate constant by sticking to. It is desirable that the horizontal width of the inclination is several mm and that the outermost peripheral portion of the holding portion outer peripheral portion 6 sinks several μm to several tens of μm.
The wafer holder 2 of the second embodiment is the same as the wafer holder of the first embodiment except for the above.
[0029]
A polishing apparatus provided with the wafer holder of the embodiment of the present invention described above and a polishing method using the same will be described. FIG. 4 is a schematic diagram illustrating a polishing apparatus 1 including the wafer holder 2 according to the first embodiment.
[0030]
A disk-shaped polishing surface plate 20 on which the polishing pad 4 is applied has a rotating shaft 23 provided perpendicularly to the disk with the surface to be applied facing downward in the vertical direction and vertically above the disk at the center of the disk. It is configured to be driven and rotated around by a first rotation drive unit 26A as a rotation drive unit. The surface to which the polishing pad 4 of the polishing surface plate 20 is attached is an annular plane centering on the rotation axis of the rotation shaft 23, and an annular elastic body 24 is mounted in close contact with the surface. A polishing pad 4, which is a polishing cloth, is sandwiched between the elastic bodies 24.
[0031]
A polishing table 25 is provided below the polishing platen 20 so as to face the polishing surface of the polishing pad 4. The polishing table 25 is a disk having substantially the same diameter as the polishing surface plate 20, and is configured to be driven to rotate around the rotation shaft 22 by a second rotation driving unit 26B as a rotation driving unit.
The polishing table 25 has a plurality of disc-shaped wafer holders 2 (five in this embodiment) so as to face the polishing surface of the polishing pad 4, and a pitch circle centered on the rotation axis of the rotation shaft 22. It is provided so that the center is located in a shape.
[0032]
The wafer holder 2 is driven by the second rotation drive unit 26B and is configured to be able to rotate on the polishing table 25 with each rotation shaft 21 as the rotation center. When the outer diameter is slightly smaller than the wafer holder 2 and the inner diameter is slightly larger than the outer diameter of the wafer 3 to be placed on the upper surface of the wafer holder 2, that is, the polishing pad 4 side. The ring-shaped retainer 10 that is substantially in the same plane as the upper surface of the wafer 3 (typically the same or slightly above the upper surface of the wafer) has its center coincident with the center of the rotating shaft 21. The wafer 3 that is the object to be polished is placed and held in the inner diameter of the annular ring of the retainer 10. The rotation axes of the rotation shafts 21, 22, and 23 are parallel to each other. The polishing surface plate 20 is connected to a pressing drive unit 30 and drives the polishing surface plate 20 so that the polishing pad 4 is pressed against the wafer 3 during polishing.
[0033]
In such a configuration, the polishing table 3 is rotated around the rotation axis 22 by the second rotation drive unit 26B, and the wafer holder 2 and thus the wafer 3 is rotated around the rotation axis 21. The wafer holder 2 rotates (revolves) around the rotating shaft 21 of the wafer holder 2 while rotating (revolving) around the rotating shaft 22. Further, the polishing surface plate 20 is rotated around the rotation shaft 23. Therefore, if one or both of the polishing table 3 having the rotating shaft 22 and the polishing surface plate 20 having the rotating shaft 23 are rotated, the polishing pad attached to the wafer 3 and the polishing surface plate 20 on the polishing table 3. 4 will revolve relatively.
[0034]
The rotation axis of the rotation shaft 22 and the rotation axis of the rotation shaft 23 may be on the same straight line, but are typically set to be shifted in parallel to some extent. As a result, the polishing can be performed using the widest possible range of the polishing surface of the polishing pad 4 and with the polishing surface so as to be as different as possible against the wafer 3, thereby enabling uniform polishing.
[0035]
A polishing slurry supply hole 27 is formed through the center of the rotary shaft 23, and the polishing slurry is supplied from the polishing slurry supply unit 28 through the polishing slurry supply pipe 29 connected to the polishing slurry supply hole 27. Polishing is performed by rotating the polishing surface of the polishing pad 4 and the surface to be polished of the wafer 3 in contact with each other. In this apparatus, five wafers 3 can be polished simultaneously.
[0036]
The polishing apparatus 1 according to the present embodiment includes the wafer holder 2 according to the first embodiment and holds the wafer 3, so that the polishing rate of the wafer 3 by the polishing pad 4 is made uniform and the surface of the surface to be polished of the wafer 3 is polished. Flatness is improved. The wafer holder 2 may be that of the second embodiment.
[0037]
The polishing method of the present invention is suitable for a semiconductor device manufacturing method such as planarization of an interlayer insulating film or a metal film polishing process. When polishing the wafer 3, the central portion of the wafer 3 is maintained flat, and the outer peripheral portion of the wafer 3 can be easily bent away from the polishing surface of the polishing pad. The polishing rate of the wafer 3 can be made uniform according to who and the like. By doing so, since the surface of the wafer 3 follows the surface of the polishing pad on the wafer 3, it is possible to form a highly accurate pattern including the outer peripheral portion, and the surface of the wafer 3 can be spread over a wide range. Can be used.
[0038]
【The invention's effect】
As described above, according to the present invention, the holding portion that holds the workpiece of the workpiece holder is formed so that the rigidity of the annular region of the peripheral portion is smaller than the rigidity of the inner region of the central portion of the holding portion. Therefore, for example, when a relatively rotating polishing pad is pressed against the workpiece, the holding portion of the workpiece holder compresses and deforms in the annular region of the peripheral portion, and the workpiece is processed accordingly. The outer peripheral portion of the object is bent corresponding to the deformation of the holding portion, the lower surface of the polishing pad is brought into close contact with the processing surface of the workpiece, the pressing pressure of the polishing pad is made uniform, and the polishing rate is made uniform.
[0039]
In addition, if the region of the center of the surface of the workpiece holder that holds the workpiece is formed as a flat surface, and the annular region of the peripheral portion of the surface that holds the workpiece is inclined outwardly, For example, when a relatively rotating polishing pad is relatively pressed against the workpiece, the outer peripheral portion of the workpiece bends corresponding to the inclination of the annular region around the holding portion, and the lower surface of the polishing pad Adheres to the processed surface of the workpiece, the pressing pressure of the polishing pad becomes uniform, and the polishing rate becomes uniform.
[0040]
Therefore, a polishing apparatus including these workpiece holders and a polishing method using the same enable a semiconductor device manufacturing process that forms a high-precision pattern including a wafer outer peripheral portion with a high yield.
[Brief description of the drawings]
FIG. 1A is a schematic front sectional view of a wafer holder according to a first embodiment of the present invention, showing both a wafer and a polishing pad. FIG. 1B is a schematic plan view of the wafer holder.
FIG. 2 is a schematic cross-sectional view showing a state of bending of the holding portion outer peripheral portion, the suction plate, the wafer outer peripheral portion, and the polishing pad of the wafer holder according to the first embodiment.
FIG. 3 is a schematic enlarged partial sectional view of a wafer holder according to a second embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing a configuration of a polishing apparatus according to a third embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view showing a case in which a polishing pad sagging occurs in a conventional wafer holder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Wafer holder 3 Wafer 3A Outer peripheral edge part 3B Outer peripheral part 3C Orientation flat 4 Polishing pad 4A Polishing pad droop 4B Polishing pad lower surface 5 Holding part 5A Holding part shoulder surface 6 Holding part outer peripheral part 7 Holding part central part 8 Suction Groove 9 Suction plate 10 Retainer 11 Hole 12 Vacuum line 14 Groove 20 Polishing surface plates 21, 22, 23 Rotating shaft 24 Elastic body 25 Polishing table 26A First rotational driving unit 26B Second rotational driving unit 27 Polishing slurry supply hole 28 Polishing slurry supply section 29 Polishing slurry supply pipe 30 Pushing drive section

Claims (3)

A workpiece holder comprising a workpiece holding portion in a portion surrounded by a retainer through a groove,
As the inner region of the central part of the holding part, the central part of the holding part provided with a plurality of holes communicating with the vacuum line connected to the vacuum exhaust device at the center and around the center protrudes upward in the vertical direction from the shoulder surface of the holding part. The holding portion outer peripheral portion as an annular region of the peripheral portion of the holding portion is made of a material having a lower elastic coefficient than the holding portion central portion,
A plurality of suction grooves are formed on the holding portion central portion and the holding portion outer peripheral portion, and a plurality of suction grooves are formed immediately above the holding portion central portion, and holes corresponding to the holes in the holding portion central portion are formed at the bottom of the suction groove. A workpiece holder, comprising a suction plate provided. A workpiece holder according to claim 1;
A polishing pad for polishing a workpiece held by the holder;
A rotation drive unit for relatively rotating the workpiece holder and the polishing pad;
A pressing drive unit that presses the polishing pad relative to the workpiece held by the holding unit;
A polishing apparatus comprising: a polishing slurry supply unit configured to supply a polishing slurry between the workpiece held by the holding unit and the polishing pad. The workpiece holder according to claim 1, wherein the workpiece is held so that the surface to be polished faces the polishing pad,
Supplying a polishing slurry between the polishing pad and the workpiece;
A method for polishing a workpiece, wherein the polishing pad is rotated relatively while pressing the polishing pad against the workpiece, and the polishing surface is polished by the polishing pad.

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