JP3220937B2 - Wafer polishing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing apparatus, and more particularly, to a chemical mechanical polishing method (CMP).
ical Polishing).

[0002]

2. Description of the Related Art Conventionally, this type of wafer polishing apparatus holds a wafer with a carrier and presses the wafer against a polishing cloth, and also rotates a carrier and the polishing cloth while rotating a polishing liquid (slurry) between the carrier and the polishing cloth. Is supplied to polish the wafer. Since the slurry is difficult to supply directly between the carrier and the polishing cloth, the slurry is supplied on the polishing cloth, and indirectly supplied between the carrier and the polishing cloth by rotation of the polishing cloth. I have to.

[0003] Further, in a conventional wafer polishing apparatus, an annular member is arranged around the wafer, and a groove for guiding a polishing liquid toward the wafer is formed on a surface of the annular member that contacts the polishing cloth. Proposed. According to this wafer polishing apparatus, the polishing liquid supplied to the polishing cloth can be efficiently supplied to the wafer by the grooves.

[0004]

In a wafer polishing apparatus using CMP, it is important to sufficiently infiltrate the slurry into the polishing cloth in order to improve the polishing accuracy of the wafer. However, in the conventional wafer polishing apparatus in which the annular member is arranged, although the slurry can be efficiently supplied to the wafer by the groove, the polishing accuracy cannot be improved because the slurry cannot be soaked into the polishing cloth. There are drawbacks.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wafer polishing apparatus capable of improving the polishing accuracy of a wafer by sufficiently impregnating a slurry into a polishing cloth. I do.

[0006]

According to the present invention, in order to achieve the above object, a polishing liquid is supplied between a wafer and a polishing cloth, and the wafer is moved relative to the polishing cloth while being pressed against the wafer. In a wafer polishing apparatus for polishing, an annular member that surrounds the periphery of the wafer and is pressed against the polishing cloth together with the wafer is provided, and the polishing liquid is applied to the surface of the annular member that contacts the polishing cloth from outside the annular member. A groove for guiding inward is formed, and a flat surface is formed at the inner end position of the groove to allow the polishing liquid guided by the groove to penetrate into the polishing pad.

According to the present invention, the polishing liquid is guided toward the wafer by the groove of the annular member, and the polishing liquid guided by the groove is pressed against the polishing cloth by the flat surface of the annular member to form the polishing cloth. Soak in Therefore, according to the present invention, the wafer can be polished with the polishing cloth sufficiently permeated with the polishing liquid, so that the polishing accuracy can be improved.

[0008]

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 is an overall configuration diagram of a wafer polishing apparatus according to an embodiment of the present invention. Wafer polishing apparatus 10 shown in FIG.
Is mainly composed of a polishing table 12 and a wafer holding head 14. The polishing platen 12 is formed in a disk shape, and a polishing cloth 16 is provided on an upper surface thereof. In addition, a spindle 18 is connected to a lower portion of the polishing table 12, and the spindle 18 is connected to an output shaft (not shown) of a motor 20. The polishing platen 12 is rotated in the direction of arrow A by driving a motor 20, and a slurry 23 is supplied from a nozzle 21 onto the polishing cloth 16 of the rotating polishing platen 12.

The wafer holding head 14 is moved up and down by a lifting device (not shown), and is moved up when a wafer to be polished is set on the wafer holding head 14. Further, the wafer holding head 14 is moved downward when polishing the wafer, and presses the wafer against the polishing pad 16. FIG. 2 is a vertical sectional view of the wafer holding head 14. The wafer holding head 14 shown in FIG. 1 includes a head body 22, a carrier 24, a guide ring 26, a polishing surface adjustment ring 28, a rubber sheet 30, and the like. The head body 22 is formed in a disk shape,
The motor 2 is rotated in the direction of arrow B by a motor (not shown) connected to the motor 2. The air supply path 3 is provided in the head body 22.
4 and 36 are formed. The air supply passage 34 extends outside the wafer holding head 14 as shown by a two-dot chain line in FIG. 2 and has a regulator (R) 38A.
And an air pump (AP: air pnmp) 40. The air supply path 36 is connected to a pump 40 via a regulator 38B.

The carrier 24 is formed in a substantially cylindrical shape, and is disposed coaxially with the head main body 22 below the head main body 22. Further, a concave portion 25 is provided on the lower surface of the carrier 24.
Are formed, and the porous plate 4 having air permeability is formed in the concave portion 25.
2 are stored. The air chamber 2 is located above the porous plate 42.
The air chamber 27 is communicated with an air suction path 44 formed in the carrier 24. The air suction path 44 extends outside the wafer holding head 14 as shown by a two-dot chain line in FIG.
suction pump) 46. Therefore, when the suction pump 46 is driven, the wafer 50 is sucked by the porous plate 42 and held by suction on the lower surface of the porous plate 42. The porous plate 42 has a number of air passages therein, and for example, a porous plate made of a sintered body of a ceramic material is used.

The carrier 24 has a number of air supply paths 48, 48,.
(Only two locations are shown in FIG. 2). The air supply paths 48 extend outside the wafer holding head 14 as shown by a two-dot chain line in FIG. 2 and are connected to the pump 40 via a regulator 38C. Therefore, the compressed air from the pump 40 is supplied to the air supply path 48,
48 are blown out into the air chamber 51 between the porous plate 42 and the wafer 50. As a result, a pressure air layer is formed in the air chamber 51, 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 pressure air layer.

The carrier 24 has a large number of air / water supply passages 5 each having an ejection port formed on the lower surface of the carrier 24.
2, 52... (Only two locations are shown in FIG. 2).
The air / water supply paths 52 extend outside the wafer holding head 14 as shown by a two-dot chain line in FIG. An air pump 40 is connected to one branch via a regulator 38D, and a water pump (WP: water pnmp) 56 is connected to the other branch. Therefore, the valve 54 opens the path on the air pump 40 side,
When the path on the water pump 56 side is closed, compressed air from the air pump 40 is supplied to the air / water supply paths 52, 52.
Are supplied to the air chamber 51 via the. When the valve 54 is switched to close the path on the air pump 40 side and open the path on the water pump 56 side, the water from the water pump 56 is supplied to the air / water supply paths 52, 52.
Are supplied to the air chamber 51 via the.

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
4, the outer peripheral portion 30B presses the polishing surface adjustment ring 28.

A rubber sheet 3 is provided below the head body 22.
A space 60 which is hermetically sealed by the central portion 30 </ b> A and the stopper 58 is formed. The air supply path 36 communicates with the space 60. 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 of the wafer 50 can be controlled.

The guide ring 26 is formed in a cylindrical shape, and is disposed coaxially with the head main body 22 below the head main body 22. In addition, the guide ring 26 is attached to the rubber sheet 3.
0 is fixed to the head main body 22. A polishing surface adjusting ring (annular member) 28 is arranged between the guide ring 26 and the carrier 24. A retainer ring (annular member) 62 for preventing the wafer 50 from jumping out is attached to the lower inner peripheral portion of the polishing surface adjusting ring 28. The polishing surface adjusting ring 28 and the retainer ring 62
Will be described later.

An annular space 64 is formed in the lower outer peripheral portion of the head main body 22 and is closed by the outer peripheral portion 30B of the head main body 22 and the rubber sheet 30 and the like. This space 6
4 communicates with the air supply path 34. 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 polishing surface adjustment ring 28. As a result, the annular lower surface of the polishing surface adjusting ring 28 (polishing cloth 1)
6 and the annular lower surface of the retainer ring 62 (the contact surface with the polishing pad 16) are pressed against the polishing pad 16.
The pressing force of the polishing surface adjustment ring 28 and the retainer ring 62 can be controlled by adjusting the air pressure with the regulator 38A.

FIG. 3 is a perspective view of the polishing surface adjusting ring 28 and the retainer ring 62. As shown in the figure, a plurality of grooves 29 are formed on a contact surface 28A of the polishing surface adjusting ring 28 with the polishing cloth. As shown in FIG. 4, the grooves 29 are formed at equal intervals and inclined with respect to the centripetal direction, and guide the slurry toward the wafer by rotating the polishing surface adjusting ring 28 indicated by the arrow in the figure. It is formed in the direction. As a result, the slurry supplied onto the polishing pad is guided toward the wafer by the grooves 29. The contact surface 62A of the retainer ring 62 with the polishing cloth is formed flat. This allows
The slurry guided to the groove 29 is pressed against the polishing cloth by the flat contact surface 62A of the retainer ring 62 and permeates the polishing cloth. In this embodiment, the groove 29 is formed in the polishing surface adjusting ring 28 and the flat surface is formed in the retainer ring 62. However, the present invention is not limited to this, and the groove and the flat surface are formed in an integrally formed annular member. You may.

On the other hand, in FIG. 2, the wafer holding head 14 is provided with a detecting device for detecting the polishing amount of the wafer 50. This detection device includes a sensor 70 including a core 66 and a bobbin 68 and non-contact sensors 72 and 7.
2, 72, and these sensors 70,
A CPU (not shown) for performing arithmetic processing on the detection values detected at 72, 72, 72 is provided outside the wafer holding head 14.

The bobbin 68 of the sensor 70 is attached to the tip of an arm 76 extending from the inner surface of the polishing surface adjusting ring 28 in the direction of the rotation axis of the wafer holding head 14. The core 66 of the sensor 70 is located on the upper surface of the carrier 24 and the center axis of the core 66 is aligned with the wafer holding head 14.
Is provided at a position that is coaxial with the rotation axis. The sensor 70 detects the amount of vertical movement of the carrier 24 with respect to the lower surface of the polishing surface adjustment ring 28, that is, with respect to the polishing surface of the wafer 50. The carrier 24 has a groove 78 into which the arm 76 is inserted.

Although the polishing amount of the wafer 50 can be generally detected by the sensor 70, in this embodiment, the detection value detected by the sensor 70 is used as the sensor 72, 72,
The amount of polishing of the wafer 50 is accurately obtained by correcting with the detection value detected at 72. The sensor 72 is a non-contact sensor such as a capacitance sensor, and its detection surface 72 a is arranged flush with the lower surface of the porous plate 42, and detects the distance from the upper surface of the wafer 50 to form a pressure air layer ( The amount of change in the layer thickness of the air chamber 51) is detected.

Then, the CPU obtains the sensors 72, 72,
The polishing amount of the wafer 50 is calculated by adding the fluctuation amount of the thickness of the pressure air layer detected at 72. That is, C
The PU calculates the polishing amount of the wafer 50 from the fluctuation amount with respect to the reference value stored in advance. For example, the sensor 70
Is the fluctuation amount detected at T1, and the sensors 72, 72, 72
Assuming that the average value of the fluctuation amounts detected in the step is T2, the polishing amount of the wafer 50 at that time is calculated by T1 + T2. Also,
The variation from the sensor 70 is T1, and the sensors 72, 72,
If the average value of the variation from 72 is O, the polishing amount of the wafer 50 at that time is calculated by T1-0. Further, if the fluctuation amount from the sensor 70 is T1 and the average value of the fluctuation amounts from the sensors 72, 72, 72 is -T2, the polishing amount of the wafer 50 at that time is calculated as T1-T2. in this way,
In the present embodiment, the sensors 70 and 72 are provided to calculate the polishing amount from the two fluctuation amounts.
The polishing amount of 0 can be accurately measured.

Next, the operation of the wafer polishing apparatus 10 configured as described above will be described. First, after raising the wafer holding head 14, the suction pump 46 is driven to suck and hold the wafer 50 to be polished on the porous plate 42. Next, the wafer holding head 14 is lowered, and the lowering movement is stopped at a position where the contact surface 28A of the polishing surface adjustment ring 28 of the wafer holding head 14 is in contact with the polishing pad 16. Then, the suction pump 46 is stopped to release the suction of the wafer 50, and the wafer 50 is placed on the polishing pad 16.

Next, the pump 40 is driven to supply compressed air to the air chamber 51 via the air supply path 48, and a pressure fluid layer is formed in the air chamber 51. Then, the compressed air from the pump 40 is supplied to the space 60 via 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 pressure air layer is formed. The wafer 50 is pressed against the polishing pad 16 via the polishing pad. Then, the air pressure is adjusted by the regulator 38B to control the internal air pressure to a desired pressure, and the pressing force of the wafer 50 against the polishing pad 16 is kept constant.

Next, compressed air from the pump 40 is supplied to the space 64 via the air supply path 34, and the outer peripheral portion 30B of the rubber sheet 30 is elastically deformed by internal air pressure to press the polishing surface adjusting ring 28. Then, the contact surface 28A of the polishing surface adjusting ring 28 and the flat contact surface 62A of the retainer ring 62 are pressed against the polishing pad 16. And the regulator 38
The air pressure is adjusted by A to control the internal air pressure to a desired pressure, and the pressing force of the polishing surface adjusting ring 28 and the retainer ring 62 against the polishing pad 16 is kept constant. The pressing force at this time is set to a force that allows the slurry to soak into the polishing pad 16. Thereafter, the polishing table 12 and the wafer holding head 14 are rotated, and the slurry 23 is supplied from the nozzle 21 to start polishing the wafer 50.

During the polishing of the wafer 50, the slurry 23 is supplied with the grooves 29 of the rotating polishing surface adjusting ring 28,
The slurry 23 guided toward the wafer 50 by 29... And guided into the groove 29 is pressed against the flat contact surface 62 </ b> A of the retainer ring 62 and soaks into the polishing pad 16. Therefore, since the wafer 50 is polished by the polishing pad 16 impregnated with the slurry 23, the polishing accuracy of the wafer 50 is improved, and the polishing rate is also improved.

On the other hand, the polishing amount of the wafer 50 during polishing is calculated by the CPU. When the calculated polishing amount of the wafer 50 reaches a preset polishing target value, a polishing end signal is output. Then, the wafer polishing apparatus 10 is stopped. Thus, polishing of one wafer 50 is completed. When the second and subsequent wafers 50 are polished, the above-described steps may be repeated.

[0027]

As described above, according to the wafer polishing apparatus of the present invention, the annular member surrounding the periphery of the wafer is provided, and the polishing liquid is directed to the surface of the annular member which contacts the polishing cloth. Groove and inner end of this groove
Since a flat surface is formed at the position where the polishing liquid guided by the groove is soaked into the polishing cloth, the wafer can be polished with the polishing cloth sufficiently permeated with the polishing liquid. Therefore,
The present invention can improve polishing accuracy.

[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 wafer holding head applied to the wafer polishing apparatus of FIG.

FIG. 3 is a perspective view of a polishing surface adjustment ring and a retainer ring.

FIG. 4 is an enlarged view of a portion A of the polishing surface adjustment ring and the retainer ring shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Wafer polishing apparatus 12 ... Polishing surface plate 14 ... Wafer holding head 16 ... Polishing cloth 23 ... Slurry 28 ... Polishing surface adjustment ring 29 ... Groove 50 ... Wafer 62 ... Retainer ring

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B24B 37/00-37/04 H01L 21/304 622

Claims (1)

(57) [Claims] 1. A wafer polishing apparatus for polishing a wafer by supplying a polishing liquid between a wafer and a polishing cloth and relatively moving the wafer and the polishing cloth while pressing the wafer and the polishing cloth. the annular member is pressed against the polishing cloth with the wafer disposed on the surface in contact with the polishing cloth of the annular member, the polishing liquid and groove inwardly from outer ring guide, inside end position of the groove A wafer polishing apparatus having a flat surface for allowing a polishing liquid guided by the groove to permeate the polishing cloth.