JP2002018700A - Wafer polisher - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer polisher capable of uniformly polishing the whole surface of a wafer by preventing excessive polishing for the outer peripheral edge of the wafer. SOLUTION: In this polisher, a retainer ring 28 is supported on a head main body to be freely rotated around an axis P2 eccentric from an axis P1 of rotation of a carrier 24. The retainer ring 28 is also rotatably supported on the head main body 22 so that the axis P2 thereof is positioned on the downstream side in the rotating direction of a polishing pad 16 to the axis P1 of rotation of the carrier 24. Thus, the inner peripheral edge 28A of the retainer ring 28 positioned on the downstream side in the rotating direction of the polishing pad 16 is kept apart from the outer peripheral edge 50A of the wafer 50, and a raised part 16C caused on the downstream side in the rotating direction of the polishing pad 16 is caused between the inner peripheral edge 28 of the separated retainer ring 28 and the outer peripheral part 50A of the wafer 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for polishing a wafer by chemical mechanical polishing (CMP).

[0002]

2. Description of the Related Art As shown in FIG. 5, a wafer polishing apparatus disclosed in Japanese Patent Application Laid-Open No. 8-229808 includes a holding head 3 having a carrier 1 and a retainer ring 2 and a platen 5 on which a polishing pad 4 is attached. The main configuration is, carrier 1
The wafer 6 is pressed against the rotating polishing pad 4 and polished, and the carrier 1 is
The retainer ring 2 arranged coaxially with the polishing pad 4
To surround the periphery of the wafer 6.

As the polishing pad 4, a hard or soft polishing pad is selected and used depending on the material (eg, SiO ₂ ) of a polishing layer (insulating film) of a wafer. When the polishing pad 4 is used, a so-called waving phenomenon occurs in which the polishing pad 4 locally rises along the periphery of the portion in contact with the retainer ring 2. When such a phenomenon occurs in the polishing pad 4, the polishing pad 4
The raised portion 4C causes the outer peripheral portion 6A of the wafer 6 to be excessively polished, thereby causing a problem that polishing uniformity of the wafer 6 is hindered.

[0004] The bulging portion caused by the waving phenomenon has portions 4A and 4B corresponding to the outer peripheral edge 2A and the inner peripheral edge 2B of the retainer ring 2 located on the upstream side in the rotation direction of the polishing pad 4.
Occurs in a portion 4C corresponding to the inner peripheral edge 2C of the retainer ring 2 located on the downstream side in the rotation direction of the polishing pad 4.
Here, the raised portions 4A, 4B generated in the former are generated at a position away from the outer peripheral portion 6A of the wafer 6, so that there is no problem in processing, but the raised portions 4C generated in the latter are included in the outer peripheral portion of the wafer 6. Since 6A contacts, the outer peripheral edge 6A of the wafer 6 is excessively polished here.

Therefore, the wafer polishing apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 8-229808 prevents the occurrence of the waving phenomenon by setting the contact force of the retainer ring 2 to the polishing pad 4 to a weak appropriate value, and prevents the wafer outer peripheral edge 6A. Overpolishing is prevented.

[0006]

However, even if the contact force of the retainer ring 2 with respect to the polishing pad 4 is set to a weak appropriate value as in the conventional wafer polishing apparatus,
The ripple effect could not be completely eliminated, and the expected effect could not be obtained.

Incidentally, the polishing pad is pressed against the retainer ring and elastically deformed, so that the flatness of the polishing pad surrounded by the retainer ring is ensured. That is, the contact force of the retainer ring is set to a force that overcomes the restoring force of the polishing pad. In such a force balance relationship, if the contact force of the retainer ring is weakened, the restoring force of the polishing pad will prevail, so the polishing pad will rise along the outer peripheral edge of the wafer, and the outer peripheral edge of the wafer will be excessively polished. New problem has arisen.

The present invention has been made in view of such circumstances, and has as its object to provide a wafer polishing apparatus capable of uniformly polishing the entire surface of a wafer by preventing excessive polishing of the outer peripheral edge of the wafer. I do.

[0009]

In order to achieve the above object, the present invention provides a wafer polishing apparatus for holding a wafer on a holding head and pressing the wafer against a rotating polishing pad to polish the surface of the wafer. A head body that is rotated and disposed opposite to the polishing pad, a carrier provided on the head body, for holding a wafer and pressing the surface of the wafer against the polishing pad, and disposed on an outer periphery of the carrier. A retainer ring which is in contact with the polishing pad and is rotatably supported by the head body about an axis eccentric to the rotation axis of the carrier.

According to another aspect of the present invention, there is provided a wafer polishing apparatus for polishing a wafer surface by holding a wafer on a holding head and pressing the wafer against a rotating polishing pad to achieve the above object. A head body disposed opposite to the polishing pad, a carrier provided on the head body, for holding the wafer, a first pressing unit for pressing the carrier toward the polishing pad, A pressure air layer forming means for forming a pressure air layer between the wafer and the pressing force from the first pressing means to the wafer via the pressure air layer; and A retainer abutted on the pad and rotatably supported by the head body about an axis eccentric to the rotation axis of the carrier; And grayed, characterized in that the retainer ring provided with a second pressing means for pressing the polishing pad.

The first aspect of the present invention is directed to a wafer polishing apparatus for polishing a wafer by pressing the wafer against a polishing pad with a carrier. The invention according to claim 2 is
A wafer polishing apparatus for forming a pressurized air layer between a carrier and a wafer by a pressurized air layer forming means, transmitting a pressing force to the wafer through the pressurized air layer, and pressing the wafer against a polishing pad for polishing. It is targeted. The present invention supports the retainer ring of such a wafer polishing apparatus rotatably on the head main body around an axis eccentric with respect to the rotation axis of the carrier, and the axis of the retainer ring corresponds to the rotation axis of the carrier. The head was rotatably supported by the head body so as to be located on the downstream side in the rotation direction of the polishing pad.

Thus, the inner peripheral edge of the retainer ring located on the downstream side in the rotational direction of the polishing pad is separated from the outer peripheral edge of the wafer, and the raised portion generated on the downstream side in the rotational direction of the polishing pad is separated from the retainer ring. Occurs between the inner peripheral edge of the wafer and the outer peripheral portion of the wafer. Therefore, since the outer peripheral edge of the wafer does not contact the raised portion,
Excessive polishing of the outer peripheral edge of the wafer can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wafer polishing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a wafer polishing apparatus 1 according to an embodiment.
0 is an overall configuration diagram of the wafer polishing apparatus 10.
It mainly comprises a platen 12 and a holding head 14. The platen 12 is formed in a disk shape, and a polishing pad 16 is attached to an upper surface thereof. The polishing pad 16 includes a suede type, a nonwoven fabric, a urethane foam type, and the like. The polishing pad 16 is appropriately selected according to the material of the polishing layer of the wafer and is attached to the platen 12.

A spindle 18 is provided below the platen 12.
And the spindle 18 is connected to an output shaft (not shown) of the motor 20. By driving the motor 20, the platen 12 is rotated in the direction of arrow A, and a mechanochemical abrasive (slurry) is supplied from a nozzle (not shown) onto the polishing pad 16 of the rotating platen 12. As the mechanochemical polishing agent, for example, when the polishing layer is silicon, a suspension of BaCO ₃ fine powder in a KOH aqueous solution is used.

The holding head 14 is provided to be vertically movable by an elevating device (not shown), and is moved up when a wafer to be polished is set on the holding head 14. When polishing the wafer, the holding head 14 is moved down and pressed against the polishing pad 16 together with the wafer. In FIG. 1, only one holding head 14 is shown, but the number of holding heads 14 is not limited to one. For example, a plurality of holding heads 14 are installed on a circumference around a spindle 18 at equal intervals. Is preferable in terms of processing efficiency.

FIG. 2 is a longitudinal sectional view of the holding head 14. The holding head 14 includes a head body 22, a carrier 24, a guide ring 26, a retainer ring 28, a rubber sheet 30, and the like. The head main body 22 is formed in a disk shape, and is rotated in a direction indicated by an arrow B in FIG. 2 by a motor (not shown) connected to the rotation shaft 32. Further, air supply paths 34 and 36 are formed in the head main body 22. The air supply passage 34 extends outside the holding head 14 as shown by a two-dot chain line in FIG.
gulator) 38A through an air pump (AP)
p) Connected to 40. The air supply path 36 is connected to an air pump 40 via a regulator 38B.

The carrier 24 is formed in a substantially columnar shape, and is disposed coaxially with the head main body 22 below the head main body 22. Accordingly, the carrier 24 is rotated about the axis P1 of the rotating shaft 32 in the direction of the arrow B in FIG.

The carrier 24 is formed in a substantially columnar shape, and is disposed coaxially with the head main body 22 below the head main body 22. Further, the carrier 24 has a number of air supply passages 48 each having an ejection port formed on the outer periphery of the lower surface of the carrier 24,
48 (only two locations are shown in FIG. 2) and a large number of air supply passages 52 having ejection holes formed in the inner peripheral portion of the lower surface of the carrier 24;
52 (only two locations are shown in FIG. 2). Are extended outside the holding head 14 as shown by a two-dot chain line in FIG. 2, and one of them is provided with a suction pump (SP: suctio) via a switching valve 52.
n pump) 56, and the other is connected to the air pump 40 via the regulator 38C. Therefore, when the air pump 40 side is closed by the switching valve 54 and the suction pump side 56 is opened, the wafer 50 is suction-held on the lower surface of the carrier 24 by the suction force of the suction pump 56. Further, the air pump 4 is controlled by the switching valve 54.
When the zero side is opened and the suction pump side 56 is closed, the compressed air from the air pump 40 is supplied to the air supply path 4.
8, 52,... Are blown into the air chamber 51 between the carrier 24 and the wafer 50. Thereby, the air chamber 51
Is formed, and the pressing force of the carrier 24 is transmitted to the wafer 50 via the pressure air layer.

The wafer 50 is pressed against the polishing pad 16 by the pressing force transmitted through the pressurized air layer, and is prevented from jumping out of the carrier 24 by the ridges 24A formed on the outer peripheral edge of the lower surface of the carrier 24. ing. In addition, the outer periphery of the wafer 50 being polished is brought into contact with the inner peripheral surface of the ridge 24A on the downstream side in the rotation direction by the rotation of the polishing pad 16. Due to this contact, the rotational force of the carrier 24 is transmitted to rotate the wafer 50 at a predetermined rotational speed. The protruding ridge 24A with which the outer peripheral edge of the wafer 50 abuts is a soft material that does not damage the wafer 50 even when the wafer 50 abuts, for example, rubber,
It is made of resin.

The holding head 14 configured as above is
By controlling the pressing force applied to the carrier 24 and moving the carrier 24 up and down, the polishing pressure of the wafer 50 (the force pressing the wafer 50 against the polishing pad 16) is controlled. Therefore, the pressure of the pressure air layer is controlled. Wafer 5
It is easier to control the polishing pressure than to control the polishing pressure of 0. That is, in the holding head 14, the polishing pressure of the wafer 50 can be controlled only by controlling the vertical position of the carrier 24. The air blown out from the air supply passages 48 is exhausted to the outside through an exhaust hole (not shown) formed in the ridge 24A and the retainer ring 28.

On the other hand, one rubber sheet 30 is disposed between the carrier 24 and the head main body 22. This rubber sheet 30 is formed in a disk shape with a uniform thickness. The rubber sheet 30 is fixed to the lower surface of the head body 22 by an annular stopper 58, and the rubber sheet 30 is divided into a center part 30 </ b> A and an outer peripheral part 30 </ b> B with the stopper 58 as a boundary. The center 30A of the rubber sheet 30 is the carrier 2
The outer peripheral portion 30B functions as an airbag that presses the retainer ring 28.

Below the head body 22, a rubber sheet 3
A space 60 which is hermetically sealed by the central portion 30 </ b> A and the stopper 58 is formed. In this space 60, the air supply path 36
Is communicated. Therefore, when compressed air is supplied from the air supply path 36 to the space 60, the central portion 30A of the rubber sheet 30 is elastically deformed by air pressure and presses the upper surface of the carrier 24. Thereby, a pressing force of the wafer 50 against the polishing pad 16 can be obtained. Further, if the air pressure is adjusted by the regulator 38B, the pressing force (polishing pressure) of the wafer 50 can be controlled.

The guide ring 26 is formed in a cylindrical shape and is arranged below the head body 22. Further, the guide ring 26 is fixed to the head main body 22 via a rubber sheet 30. A retainer ring 28 is disposed between the guide ring 26 and the carrier 24.

The retainer ring 28 is arranged on the outer periphery of the carrier 24 and abuts on the polishing pad 16.
The carrier 24 is rotatably supported by a head body 22 or a guide ring 26 via a bearing (not shown) about an axis P2 eccentric to the rotation axis P1 of the carrier 24. Further, as shown in FIG. 3, the retainer ring 28 has an axis P2 of the retainer ring 28.
Is rotatably supported by the head main body 22 so that is positioned on the downstream side in the rotation direction of the polishing pad 16 with respect to the rotation axis P1 of the carrier 24. This retainer ring 28
Rotational force transmitted from polishing pad 16 and polishing pad 1
Due to the rotational force caused by the peripheral speed difference 6 (the peripheral speed difference in the radial direction), the rotation is driven by the arrow C in FIG.

Thus, the inner peripheral edge 28A of the retainer ring 28 located on the downstream side in the rotation direction of the polishing pad 16 is
As shown in FIG. 4, the raised portion 16 </ b> C that is separated from the outer peripheral edge 50 </ b> A of the wafer 50 and generated on the downstream side in the rotation direction of the polishing pad 16 is between the inner peripheral edge 28 </ b> C of the separated retainer ring 28 and the outer peripheral portion 50 </ b> A of the wafer 50. Therefore, excessive polishing of the outer peripheral edge 50A of the wafer 50 due to the raised portion 16C can be prevented. In addition, the raised portion due to the waving phenomenon also occurs in portions 16A and 16B corresponding to the outer peripheral edge 28A and the inner peripheral edge 28B of the retainer ring 28 located on the upstream side in the rotation direction of the polishing pad 16, but the raised portions 16A and 16B Is the wafer 50
Occurs at a position distant from the outer peripheral portion 50A of the wafer 50, so that the uniform polishing of the wafer 50 is not adversely affected.

An annular space 64 is formed at the lower outer peripheral portion of the head main body 22 shown in FIG. 2 and is closed by the outer peripheral portion 30 B of the head main body 22 and the rubber sheet 30. The air supply path 34 communicates with the space 64. Therefore, when compressed air is supplied from the air supply path 34 to the space 64, the outer peripheral portion 30B of the rubber sheet 30 is elastically deformed by air pressure and presses the annular upper surface of the retainer ring 28. Thereby, the annular lower surface 29 of the retainer ring 28 is pressed against the polishing pad 16. The retainer ring 28
Can be controlled by adjusting the air pressure with the regulator 38A.

On the other hand, the holding head 14
Is provided with a detection device (not shown) for detecting the amount of polishing. The detection value detected by the detection device is output to a CPU (not shown) that controls the entire wafer polishing apparatus 10. The CPU controls the wafer polishing apparatus 10 so that the polishing of the wafer 50 is stopped when the detection value output from the detection apparatus matches the polishing amount stored in the RAM or the like in advance.

Next, the operation of the wafer polishing apparatus 10 configured as described above will be described.

First, after raising the holding head 14, the suction pump 56 is driven to drive the wafer 50 to be polished.
Is sucked and held on the lower surface of the carrier 24.

Next, the holding head 14 is lowered, and the lowering movement is stopped at a position where the lower surface 29 of the retainer ring 28 of the holding head 14 contacts the polishing pad 16. And
The suction valve 56 is closed by the switching valve 54 to release the suction of the wafer 50, and the wafer 50 is placed on the polishing pad 16.

Next, the air pump 40 is driven to supply compressed air to the air chamber 51 through the air supply path 48, and a pressure air layer is formed in the air chamber 51.

Then, the compressed air from the air pump 40 is supplied to the space 60 through the air supply path 36, and the center portion 30A of the rubber sheet 30 is elastically deformed by the internal air pressure to press the carrier 24, and the compressed air is pressed. The wafer 50 is pressed against the polishing pad 16 through the layer. Then, the regulator 38B adjusts the air pressure to control the internal air pressure to a desired pressure, and keeps the pressing force (polishing pressure) of the wafer 50 against the polishing pad 16 constant.

Next, compressed air from the air pump 40 is supplied to the space 64 via the air supply path 34,
The outer peripheral portion 30 </ b> B is elastically deformed by the internal air pressure to press the retainer ring 28 and press the lower surface 29 of the retainer ring 28 against the polishing pad 16.

After adjusting the air pressure with the regulator 38A and adjusting the sinking position of the retainer ring 28, the regulator 38A keeps the air pressure constant.

Then, the polishing pressure is set by adjusting the air pressure by the regulator 38B, and thereafter, the platen 12 and the holding head 14 are rotated to start polishing the wafer 50.

Then, the polishing amount of the wafer 50 is calculated by a polishing amount detection device (not shown), and when the calculated polishing amount of the wafer 50 reaches a preset polishing target value, the CPU sends a polishing end signal. Output to stop polishing of the wafer 50. Thus, polishing of one wafer 50 is completed. When the second and subsequent wafers 50 are polished, the above-described steps may be repeated.

During polishing of the wafer 50, the holding head 14 of the embodiment uses the axis P 2 of the retainer ring 28.
The retainer ring 28 is positioned such that the position of the
Is rotatably supported by the head main body 22, so that the bulging portion 1 generated on the downstream side in the rotation direction of the polishing pad 16 is formed.
6C is generated between the inner peripheral edge 28C of the separated retainer ring 28 and the outer peripheral portion 50A of the wafer 50. Therefore, by applying the retainer ring 28, the wafer polishing apparatus 10 of the present embodiment can prevent excessive polishing of the outer peripheral edge 50A of the wafer without suppressing the occurrence of the waving phenomenon, and thus uniformly polish the entire surface of the wafer. be able to.

Although the embodiment has been described with reference to the wafer polishing apparatus 10 for polishing the wafer 50 through the pressurized air layer, the present invention is not limited to this. The retainer ring 28 can also be applied to a wafer polishing apparatus that polishes by pressing against a polishing pad.

[0040]

As described above, according to the wafer polishing apparatus of the present invention, the retainer ring is rotatably supported by the head main body about an axis eccentric to the rotation axis of the carrier, and the retainer ring is supported. The head is rotatably supported by the head body so that the axis of the polishing pad is positioned downstream of the rotation axis of the carrier with respect to the rotation axis of the carrier. Can be polished.

[Brief description of the drawings]

FIG. 1 is an overall structural diagram of a wafer polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a holding head applied to the wafer polishing apparatus of FIG.

FIG. 3 is an explanatory diagram showing an arrangement relationship between a carrier and a retainer ring in the holding head of FIG. 2;

FIG. 4 is a schematic view for explaining a profile of a polishing pad during wafer polishing.

FIG. 5 is a schematic diagram for explaining a profile of a polishing pad during conventional wafer polishing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Wafer grinding | polishing apparatus, 12 ... Platen, 14 ... Holding head, 16 ... Polishing pad, 24 ... Carrier, 28 ... Retainer ring, P1 ... Carrier axis, P2 ... Retainer ring axis

Claims (3)

[Claims] 1. A wafer polishing apparatus for polishing a surface of a wafer by holding a wafer on a holding head and pressing the wafer against a rotating polishing pad, wherein the holding head is rotated and is arranged to face the polishing pad. And a carrier provided on the head body, for holding the wafer and pressing the surface of the wafer against the polishing pad, and disposed on the outer periphery of the carrier and abutting on the polishing pad, and with respect to the rotation axis of the carrier. And a retainer ring rotatably supported by the head body about an eccentric shaft. 2. A wafer polishing apparatus for polishing a surface of a wafer by holding a wafer on a holding head and pressing the wafer against a rotating polishing pad, wherein the holding head is rotated and arranged to face the polishing pad. And a carrier provided on the head body and holding the wafer; first pressing means for pressing the carrier toward the polishing pad; and forming a pressure air layer between the carrier and the wafer; A pressure air layer forming means for transmitting the pressing force from the first pressing means to the wafer via the pressure air layer; and a rotating shaft of the carrier which is arranged on the outer periphery of the carrier and abuts on the polishing pad. A retainer ring rotatably supported by the head body about an axis eccentric with respect to, and polishing the retainer ring Wafer polishing apparatus characterized by comprising a second pressing means for pressing the head, the. 3. The retainer ring is rotatably supported by the head body such that the axis of the retainer ring is located downstream of the rotation axis of the carrier in the rotation direction of the polishing pad. 3. The wafer polishing apparatus according to claim 1, wherein: