Polishing pad assembly, apparatus for polishing a wafer including the polishing pad assembly and method for polishing a wafer using the polishing pad assembly

Abstract

An apparatus for polishing a wafer is provided. The apparatus comprises a polishing pad for polishing the wafer. The polishing pad is divided into multiple portions that are rotated in a substantially same direction. At least one of the portions of the polishing pad is adapted to rotate at a speed different than the other portions. A driving unit is also provided for moving the polishing pad. A polishing head is employed for maintaining the side of the wafer to be polished engaged with the polishing pad, for contacting the polished surface of the wafer with the polishing pad, and for rotating the wafer.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC § 119 to Korean Patent Application No. 2004-40609 filed on Jun. 4, 2004, the contents of which are herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing pad assembly, an apparatus for polishing a wafer including the polishing pad assembly, and a method for polishing a wafer using the polishing pad assembly. More particularly, the present invention relates to a polishing pad assembly for polishing a wafer to planarize a surface of the wafer, an apparatus for polishing a wafer that includes the polishing pad assembly, and a method for polishing a wafer using the polishing pad assembly.

2. Description of the Related Arts

In order to meet various requirements of customers, technologies for manufacturing a semiconductor device have developed relating to improving an integration, reliability, response time and so on. Generally, to manufacture a semiconductor device, a layer is formed on a silicon wafer used for a semiconductor substrate. The layer is then etched to form a pattern in the wafer having certain electrical characteristics.

The pattern may be formed by a deposition process, a photolithography process, an ion implantation process, a polishing process, a cleaning process, a drying process, etc. The polishing process among the above-mentioned processes is recognized as a significant technology for improving the integration degree and the structural and electrical reliability of the semiconductor device. A chemical mechanical polishing (CMP) process has been used for conducting the polishing process. According to the CMP process, a wafer is planarized by a chemical reaction between a chemical slurry and a layer on the wafer and by mechanical frictional force between a polishing pad and the layer.

An apparatus for performing the CMP process includes a polishing pad attached onto a rotatable table, the polishing pad being designed for gripping a semiconductor substrate and for rotating the semiconductor substrate, a slurry line for providing a chemical slurry to a space between the polishing pad and the semiconductor substrate, and a pad conditioner for conditioning a surface of the polishing pad.

As a semiconductor device has become highly integrated, attempts for improving the design rule have been made in the CMP process. A profile of a wafer that is polished by a CMP process is closely related to structural characteristics of the polishing pad, chemical characteristics of the slurry, operational conditions of the polishing pad, characteristics of the layer on the wafer, etc.

For example, when an oxide layer on a wafer is polished using a typical silica slurry, and the wafer is fixed using a fixed retainer ring, an edge portion of the wafer is polished more than a central portion of the wafer so that the surface of the wafer is not uniformly planarized. To the contrary, when the oxide layer is polished using a poly slurry having a high polishing selectivity or ceria slurry, the central portion of the wafer is polished more than the edge portion of the wafer so that the wafer does not have an even surface.

Meanwhile, when the wafer is polished using a single polishing pad, polishing speed and polishing uniformity vary in accordance with the polishing speed, the revolution per minute (RPM) of the polishing pad, the oscillation of the polishing pad, the down force of the polishing pad, the force of the retainer ring, the back pressure of a carrier, etc.

Generally, a modeling with respect to mechanisms of the CMP is represented by following Preston's equation:
R=Kp×P×V

In the above Preston's equation, R is the polishing ratio, Kp is the Preston constant, P is the pressure and V is the relative speed. It shall be noted that the polishing ratio is controlled by locally varying the relative speed of the wafer according to the Preston's equation.

However, since the wafers have become large and the slurry has a high polishing selectivity in the CMP process, the polishing speed and the polishing uniformity cannot be readily controlled.

The phenomenon that the polished wafer has an uneven surface is not overcome by controlling operation conditions of the CMP apparatus. Thus, methods of improving the structure of a carrier in the polishing head or the structure of the polishing pad, and locally conditioning the polishing pad, are currently proposed.

To improve the above-mentioned phenomenon by altering a structure of the polishing pad, an apparatus for planarizing wafer that includes a multi-polishing pad moving in different directions, and a method of performing the apparatus are disclosed in Japanese Patent Laid Open Publication No. 2001-110763.

FIG. 1 is a perspective view illustrating a rotary type apparatus disclosed in the Japanese Patent Publication.

Referring to FIG. 1, the apparatus 100 includes a circular polishing pad 120 divided into an inner portion, a middle portion and an outer portion. The middle portion of the polishing pad 120 is rotated in a direction different from a rotational direction of the inner and outer portions. A chuck 110 supports and rotates the polishing pad 120. A polishing head 130 grasps a polished surface of a wafer 105 facing the polishing pad 120. The polishing head 130 compresses and rotates the polished surface of the wafer 105 on the polished pad 120. A slurry line 140 provides slurry to a space between the polishing head 130 and the polishing pad 120.

FIG. 2 is a perspective view illustrating a conventional belt type apparatus.

Referring to FIG. 2, the apparatus includes a belt-shaped polishing pad divided into a middle portion and two side portions. The middle portion is rotated in a direction different from a rotational direction of the side portions. Two rollers 210 support and rotate the polishing pad 220. A polishing head 230 grasps a polished surface of a wafer 205 facing the polishing pad 220. The polishing head 230 compresses and rotates the polished surface of the wafer 205 on the polished pad 220. A slurry line 240 provides slurry on the polishing pad 220.

In FIGS. 1 and 2, the middle portions of the polishing pads 120 and 220 are moved in a direction different from those of the inner and outer portions and the side portions. When central portions of the wafers 105 and 205 are positioned at the middle portions of the polishing pads 120 and 220, rotating edge portions of the wafers 105 and 205 alternately make contact with the middle portion and the outer portion or the side portions of the polishing pads 120 and 220, respectively. Since the middle portions of the polishing pads 120 and 220 are moved in the direction opposite to that of the inner and outer portions of the polishing pad 120 and the side portions of the polishing pad 220, speeds vary at interfaces between the middle portions and the inner and outer portions or the side portions. Thus, the edge portions of the wafers 105 and 205 become damaged.

Also, the central portions of the wafers 105 and 205 make contact with the middle portions of the polishing pads 120 and 220 and the edge portions of the wafers 105 and 205 make contact with the outer portion and the side portions of the polishing pads 120 and 220. Thus, a profile of the polished central portions of the wafers 105 and 205 is different from that of the polished edge portions of the wafers 105 and 205 due to the speed differences of the polishing pads 120 and 220 by the portions. Therefore, the polished wafers 105 and 205 do not have even surfaces. As a result, according to the conventional polishing method and apparatus, polishing uniformity is deteriorated.

SUMMARY OF THE INVENTION

The present invention provides a polishing pad assembly that is capable of improving a polishing speed and a polishing uniformity.

The present invention also provides an apparatus for polishing a wafer that includes the above-mentioned polishing pad assembly.

The present invention still also provided a method of polishing a wafer that is capable of improving a polishing uniformity using the above-mentioned polishing pad assembly. An apparatus for polishing a wafer is provided. The apparatus comprises a polishing pad for polishing the wafer. The polishing pad is divided into multiple portions, e.g., at least three portions that are rotated in a substantially same direction. At least one of the portions of the polishing pad is adapted to rotate at a speed different than the other portions. A driving unit is also provided for moving the polishing pad. A polishing head is employed for maintaining the side of the wafer to be polished engaged with the polishing pad, for contacting the polished surface of the wafer with the polishing pad, and for rotating the wafer. Preferably, the polishing head is reciprocally moved to move the polishing pad and the polishing head relative thereto. The polishing pad can also be reciprocally moved to move the polishing pad and the polishing head relative thereto.

The apparatus can further comprise a slurry line for providing a polishing slurry to the polishing pad. The slurry line is preferably positioned adjacent to the polishing head to provide the polishing slurry to a location on the polishing pad adjacent to the polishing head. The slurry line can provide the polishing slurry to each of the portions of the polishing pad.

A polishing pad assembly can also be provided. The assembly can comprise a polishing pad for polishing a wafer. The polishing pad can be divided into, for example, at least three portions that are rotated in a substantially same direction. At least one of the portions of the polishing pad can be rotated at a speed different than the other portions. A driving unit can be employed for moving the polishing pad. The polishing pad is preferably reciprocally moved to polish the wafer, and the wafer is reciprocally moved between the portions of the polishing pad. Moreover, the polishing pad can be reciprocally moved so that the center of the wafer is located between an innermost interface of adjacent portions of the polishing pad and an outermost interface of adjacent portions of the polishing pad. Preferably, the driving unit comprises, for example, at least three annular portions having diameters different from each other, and the portions of the polishing pad corresponding to the annular portions of the driving unit are attached to the annular portions of the driving unit, respectively. The driving unit also can comprise, for example, at least three rollers having substantially the same diameter, and the portions of the polishing pad comprise belts which are wound about the rollers. The polishing pad is preferably divided into an odd number of portions. The respective portions of the polishing pad can have concentrically annular shapes having different diameters. They can also have a belt shape. In one form of the invention, the polishing pad is divided into an odd number of portions.

A method of polishing a wafer can be provided. The method comprises providing the wafer to be polished and a polishing head engaged with a polishing pad. The polishing pad is divided into, for example, at least three portions. The polishing pad is moved to polish the wafer, at least one of the portions of the polishing pad has a speed different from that the remaining portions of the polishing pad, and the portions of the polishing pad are moved in substantially the same direction. The method can also provide a first portion of the wafer having a relatively lower polishing selectivity makes contact with the portion of the polishing pad having a relatively rate of speed, and a second portion of the wafer having a relatively higher polishing selectivity makes contact with the portion of the polishing pad having a relatively lower speed. Preferably, the wafer is rotated engaging the polishing pad. Another preferred method further comprises moving the polishing head and the polishing pad to reciprocally move the wafer between the portions of the polishing pad.

A method of polishing a wafer can further comprise providing the wafer to be polished, a polishing head engaged with a polishing pad, and a polishing pad divided into, for example, at least three portions. The wafer is polished to form a first region polished by a first portion of the polishing pad, a second region polished by a second portion of the polishing pad, and a third region polished by the first and second portions of the polishing pad. The method can also include polishing the wafer by rotating the polishing head and moving the polishing pad and the polishing head relatively to the wafer so as to reciprocally move the wafer between the first and second portions of the polishing pad. The polishing head and the polishing pad can be moved relatively to the wafer so as to form the third region. Preferably, the first region corresponds to a central region of the wafer, the second region corresponds to an edge region of the wafer, and the third region corresponds to a region between the central region and the edge region. In another preferred for of this invention, the first portion of the polishing pad has a speed different from that of the second portion of the polishing pad.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the more particular description of preferred aspects of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings, the thicknesses of layers are exaggerated for clarity.

FIG. 1 is a perspective view illustrating a conventional rotary type apparatus for polishing a wafer;

FIG. 2 is a perspective view illustrating a conventional belt type apparatus for polishing a wafer;

FIG. 3 is a perspective view illustrating a polishing pad assembly in accordance with a first embodiment of the present invention;

FIG. 4 is a perspective view illustrating a polishing pad assembly in accordance with a second embodiment of the present invention;

FIG. 5 is a perspective view illustrating an apparatus for polishing a wafer in accordance with a third embodiment of the present invention;

FIGS. 6 and 7 are plan views illustrating operations of the apparatus in FIG. 5;

FIG. 8 is a perspective view illustrating an apparatus for polishing a wafer in accordance with a fourth embodiment of the present invention;

FIGS. 9 and 10 are plan views illustrating operations of the apparatus in FIG. 8;

FIGS. 11 and 12 are plan views illustrating polished regions of a wafer in accordance with a relative movement between the wafer and a polishing pad;

FIG. 13 is a flow chart illustrating a method of polishing a wafer in accordance with a fifth embodiment of the present invention; and

FIG. 14 is a flow chart illustrating a method of polishing a wafer in accordance with a sixth embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. It will be understood that when an element such as a layer, a region or a substrate is referred to as being “on” or “onto” another element, it can be directly on the other element or intervening elements may also be present.

Embodiment 1

FIG. 3 is a perspective view illustrating a polishing pad assembly in accordance with a first embodiment of the present invention.

Referring to FIG. 3, a rotary type polishing pad assembly 300 includes a chuck 310 and a polishing pad 320.

The chuck 310 has a circular plate typically formed of a metallic material. The chuck 310 is divided into, for example, three annular portions. The annular portions of the chuck 310 have diameters different from each other. The annular portions of the chuck 310 are rotated in substantially the same direction. Any one of the three portions can be rotated at a different speed to uniformly polish a wafer 305. For example, a middle portion having an intermediate diameter that is interposed between the respective inner and outer portions can be rotated at a speed different than that of the inner and outer portions. Also, the portions of the chuck 310 are spaced apart from each other to prevent frictions of the portions in the rotation of the chuck 310.

The polishing pad 320 makes contact with the wafer 305 to polish the wafer 305. The polishing pad 320 is arrayed over the chuck 310. Examples of materials for use as the polishing pad 320 are hardened polyurethane, polyurethane-sintered or polyurethane-coated non-woven polyester felt, etc. The slurry smoothly flows onto the polishing pad 320. Also, the polishing pad 320 has foamed cell walls that function for removing reactants from a surface of the wafer 305.

The polishing pad 320 may be divided into, for example, three concentric annular portions corresponding to those of the chuck 310. Thus, each of the concentric annular portions of the polishing pad 320 is attached to the respective corresponding concentric annular portion of the chuck 310. In particular, the polishing pad 320 includes a first pad 322 having a first diameter, a second pad 324 having a second diameter shorter than the first diameter, and a third pad 326 having a third diameter shorter than the second diameter.

The first, second and third pads 322, 324 and 326 of the polishing pad 320 are rotated in a substantially same direction. However, the first, second and third pads 322, 324 and 326 are rotated at speeds different from each other. Thus, polished area of the wafer 305 that is polished by the polishing pad 320 have different thicknesses from each other in accordance with contact position between the wafer 305 and the polishing pad 320.

When the wafer 305 is rotated and polished, a central portion of the wafer 305 is polished more than an edge portion of the wafer 305 due to a difference between translational velocities of the wafer 305. Here, the second pad 324 making contact with the central portion of the wafer 305 is rotated at a speed faster than that of the first pad 322 or the third pad 326 making contact with the edge portion of the wafer 305 so that the overall surface of the wafer 305 is uniformly polished.

In the present embodiment, the chuck 310 and the polishing pad 320 may be divided into, for example, the three portions. Alternatively, to more uniformly polish the wafer 305, the chuck 310 and the polishing pad 320 may be divided into four or more portions. Preferably, the chuck 310 and the polishing pad 320 may be divided into an odd number of portions.

To uniformly polish the wafer 305, the chuck 310 and the polishing pad 320 are reciprocally moved in a radial direction of the polishing pad 320. Thus, the wafer 305 is reciprocally moved between the first, second and third pads 322, 324 and 326 of the polishing pad 320.

When the chuck 310 and the polishing pad 320 are reciprocally moved, the reciprocation width of the chuck 310 and the polishing pad 320 may vary in accordance with the polished thickness of the wafer 305. The center of the wafer 305 is reciprocally moved between the interface between the first pad 322 and the second pad 324, and the interface between second pad 324 and the third pad 326. Here, the reciprocation speed of the chuck 310 and the polishing pad 320 are controlled so that the wafer 305 is more uniformly polished.

On the other hand, a driving unit (not shown) reciprocally moves the chuck 310 and the polishing pad 320.

Embodiment 2

FIG. 4 is a perspective view illustrating a polishing pad assembly in accordance with a second embodiment of the present invention.

Referring to FIG. 4, a belt type polishing pad assembly 400 includes two rollers 410 and a polishing pad 420.

The rollers 410 have a cylindrical shape. The rollers 410 may be divided into three cylindrical portions. The cylindrical portions of the rollers 410 have diameters substantially identical to each other. The cylindrical portions of the rollers 410 are rotated in a substantially same direction with respect to a substantially same central axis. Any one of the three cylindrical portions may be adapted to rotate at a speed different from that of remaining portions to uniformly polish a wafer. The cylindrical portions of the rollers 410 are spaced apart from each other to prevent frictions of the cylindrical portions in the rotation of the rollers 410.

The polishing pad 420 makes contact with the wafer to polish the wafer. The polishing pad 420 winds about the rollers 410. Thus, the polishing pad 420 is rotated by the rotation of the rollers 410. The polishing pad 420 is divided, for example, into three belt portions corresponding to those of the rollers 410. Thus, each of the belt portions of the polishing pad 420 is attached to one of the rollers 410, respectively.

In particular, the polishing pad 420 includes a first pad 422, a second pad 424 and a third pad 426, which have substantially same widths. The second pad 424 is located between the first and third pads 422 and 426.

The first, second and third pads 422, 424 and 426 of the polishing pad 420 are rotated in a substantially same direction. However, the first, second and third pads 422, 424 and 426 are rotated at speeds different from each other. Thus, the polished areas of the wafer that are polished by the polishing pad 420 are locally different from each other in accordance with contact position between the wafer and the polishing pad 420.

When the wafer is rotated and polished, a central portion of the wafer is polished more than an edge portion of the wafer due to a difference between translational velocities of the wafer. Here, the second pad 424 making contact with the central portion of the wafer is rotated at a speed faster than that of the first pad 422 or the third pad 426 making contact with the edge portion of the wafer so that the wafer is uniformly polished.

In the present embodiment, the rollers 410 and the polishing pad 420 are divided into, for example, the three portions. Alternatively, to more uniformly polish the wafer, the rollers 410 and the polishing pad 420 may be divided into four or more portions. Preferably, the rollers 410 and the polishing pad 420 may be divided into an odd number of portions.

To uniformly polish the wafer, the wafer is reciprocally moved in a direction substantially perpendicular to a moving direction of the polishing pad 420. Thus, the wafer is reciprocally moved between the first, second and third pads 422, 424 and 426 of the polishing pad 420.

When the rollers 410 and the polishing pad 420 are reciprocally moved, the reciprocation width of the rollers 410 and the polishing pad 420 may vary in accordance with the polished thickness of the wafer. The center of the wafer is reciprocally moved from an interface between the first pad 422 and the second pad 424 to an interface between second pad 424 and the third pad 426. Here, the reciprocation speed of the rollers 410 and the polishing pad 420 are controlled so that the wafer is more uniformly polished.

Meanwhile, a driving unit (not shown) reciprocally moves the rollers 410 and the polishing pad 420.

Embodiment 3

FIG. 5 is a perspective view illustrating an apparatus for polishing a wafer in accordance with a third embodiment of the present invention.

Referring to FIG. 5, a rotary type apparatus 500 for polishing a wafer includes a chuck 510, a polishing pad 520, a polishing head 530, a slurry line 540 and a pad conditioner 550.

The chuck 510 and the polishing pad 520 include elements substantially identical to those of the chuck 310 and the polishing pad 320 in FIG. 3. Thus, no further illustrations with respect to the chuck 510 and the polishing pad 520 are provided.

The polishing head 530 holds the wafer 505 so that the front side of the wafer 505, which is polished, faces the polishing pad 520. The polishing head 530 compresses the front side of the wafer 505 on the polishing pad 520. In particular, the polishing head 530 holds a backside of the wafer 505, which is opposite to the front side, using vacuum, and is reciprocally moved upwardly and downwardly. Also, to uniformly polish the wafer 505, the polishing head 530 contacts the wafer 505 with the polishing pad 520 and simultaneously rotates same.

The slurry line 540 is positioned over the polishing pad 520 to provide slurry 542 to the polishing pad 520. The slurry 542 is uniformly supplied from the slurry line 540 to the front side of the wafer 505. The slurry 542 is chemically reacted with the front side of the wafer 505 and is simultaneously moved to contact positions between the polishing pad 520 and the wafer 505 in accordance with the rotation of the chuck 510.

As describe above with reference to FIG. 3, the polishing pad 520 is divided into the first, second and third pads 522, 524 and 526 spaced apart from each other. When the slurry 542 is provided to any one of the first, second and third pads 522, 524 and 526, the slurry may not flow to other pads. Thus, the slurry line 540 provides the slurry 542 to each of the first, second and third pads 522, 524 and 526, respectively.

The slurry 542 supplied from the slurry line 540 outwardly flows by a centrifugal force generated in rotating the polishing pad 520. Here, the slurry 542 may not be sufficiently provided to the polished surface of the wafer 505. To prevent the above-mentioned problem, the slurry line 540 provides the slurry 542 to a position of the polishing pad 520 that is adjacent to the polishing head 530 holding the wafer 505. Therefore, the slurry 542 may be sufficiently provided to the front side of the wafer 505 before outwardly flowing by the centrifugal force. Meanwhile, the slurry 542 may be earmarked as a slurry for the insulation layer and a slurry for the metal layer.

The pad conditioner 550 removes byproducts generated in polishing the wafer 505 to constantly maintain a polishing efficiency and a polishing uniformity of the polishing pad 520. The pad conditioner 550 is located over the polishing pad 520. The pad conditioner 550 is moved upwardly and downwardly by a pneumatic cylinder (not shown). Thus, the pad conditioner 550 includes a cylindrical body connected to the pneumatic cylinder and a diamond disk fixed to the body. The diamond disk makes contact with the polishing pad 520 to remove the byproducts from the polishing pad 520.

To more uniformly polish the wafer 505, the wafer 505 is reciprocally moved in the radial direction of the polishing pad 520. The reciprocal movement of the wafer 505 may be executed by reciprocally moving the chuck 510 and the polishing pad 520 in the radial direction of the polishing pad 520. Alternatively, the reciprocal movement of the wafer 505 may be executed by reciprocally moving the polishing head 530 so that it grasps the wafer 505 in the radial direction of the polishing pad 520. Also, the reciprocal movement of the wafer 505 may be executed by reciprocally and simultaneously moving the chuck 510, the polishing pad 520 and the polishing head 530.

Since the first, second and third pads 522, 524 and 526 are rotated at speeds different from each other, polished areas of the wafer 505 are locally different from each other in accordance with contact position between the wafer 505 and the polishing pad 520. When the wafer 505 is reciprocally moved, a reciprocation width of the wafer 505 may vary in accordance with the speeds of the first, second and third pad 522, 524 and 526. Also, the reciprocating speed of the wafer 505 may be controlled.

Referring to FIG. 6, when the wafer 505 is mainly mechanically polished, the rotating wafer 505 engaged by the polishing head 530 may have a translational velocity at the edge portion of the wafer 505 faster than that at the central portion of the wafer 505. Thus, the edge portion of the wafer 505 is polished more than the central portion of the wafer 505. When the center of the wafer 505 is located on the second pad 524, the second pad 524 making contact with the central portion of the wafer 505 has a speed faster than that of the first pad 522 and the third pad 526 making contact with the edge portion of the wafer 505 to uniformly polish the wafer 505.

In the above-mentioned conditions, to more uniformly polish the wafer 505, the polishing pad 520 and the polishing head 530 are reciprocally moved with respect to each other to reciprocally move the wafer 505 in the radial direction of the polishing pad 520. The reciprocal movement of the wafer 505 may be executed by reciprocally moving the polishing pad 520 or the polishing head 530. Alternatively, the reciprocal movement of the wafer 505 may be executed by reciprocally and simultaneously moving the chuck 510, the polishing pad 520 and the polishing head 530.

Preferably, the polishing head 530 and the polishing pad 520 are reciprocally moved by reciprocally moving the polishing head 530. Thus, in the present embodiment, the polishing head 530 is reciprocally moved in the radial direction of the polishing pad 520. Here, the width of the reciprocal movement may vary in accordance with the polished thickness of the wafer 505. However, the center of the wafer 505 is reciprocally moved from the interface between the first and second pads 522 and 524 to the interface between the second and the third pads 524 and 526.

Alternatively, when the polishing pad 520 is divided into four or more portions, the center of the wafer 505 may be reciprocally moved between an outermost interface and an innermost interface among the interfaces.

Referring to FIG. 7, the rotating wafer 505 engaged by the polishing head 530 may have a pressure at the edge portion of the wafer 505 higher than that at the central portion of the wafer 505 so that the slurry 542 is stationary on the central portion of the wafer 505. Thus, when the wafer 505 is mainly chemically polished, the central portion of the wafer 505 makes major contact with the slurry 542 as compared to the edge portion of the wafer 505. As a result, the central portion of the wafer 505 is polished more than the edge portion of the wafer 505. When the center of the wafer 505 is located on the second pad 524, the second pad 524 making contact with the central portion of the wafer 505 has a speed slower than that of the first pad 522 and the third pad 526 making contact with the edge portion of the wafer 505 to uniformly polish the wafer 505.

In the above-mentioned conditions, to more uniformly polish the wafer 505, the wafer 505 is reciprocally moved in the radial direction of the polishing pad 520. Here, the width of the reciprocal movement may vary in accordance with the polished thickness of the wafer 505. However, the center of the wafer 505 is reciprocally moved from the interface between the first and second pads 522 and 524 to the interface between the second and the third pads 524 and 526.

Alternatively, when the polishing pad 520 is divided into four or more portions, the center of the wafer 505 may be reciprocally moved between an outermost interface and an innermost interface among the interfaces.

Referring now to FIGS. 6 and 7, since the first, second and third pads 522, 524 and 526 are moved in the substantially same direction, although having the speeds different from each other, speed variances at the interfaces between the pads 522, 524 and 526 may not be extensive. Thus, the edge portion of the wafer 505 may not be damaged in rotating the wafer 505. Also, since the wafer 505 is reciprocally moved, a difference between a profile at the polished central portion of the wafer 505 and a profile at the polished edge portion of the wafer 505, which is caused by the speed variances between second pad 524 and the first pad 522 or the third pad 526, may be remarkably reduced so that the wafer 505 is uniformly polished.

Embodiment 4

Referring to FIG. 8, a belt type apparatus 600 for polishing a wafer includes rollers 610, a polishing pad 620, a polishing head 630, a slurry line 640 and a pad conditioner 650.

The rollers 610 and the polishing pad 620 include elements substantially identical those of the rollers 410 and the polishing pad 420 in FIG. 4. Thus, there will be no further discussion with respect to the rollers 610 and the polishing pad 620.

The polishing head 630, the slurry line 640 and the pad conditioner 650 include elements substantially identical to those of the polishing head 530, the slurry line 540 and the pad conditioner 550 in FIG. 5. Thus, there will be no further discussion with respect to the polishing head 640, the slurry line 640 and the pad conditioner 650.

In the apparatus of Embodiment 3, the wafer 505 is reciprocally moved in the radial direction of the polishing pad 520. On the contrary, in the apparatus 600 of the present embodiment, the wafer 605 is moved in a direction substantially perpendicular to the moving direction of the polishing pad 620.

Referring to FIG. 9, this mainly mechanical polishing process is substantially identical to that of Embodiment 3 except for the configuration of the polishing pad 620. Thus, there is no further discussion with respect to the mechanical polishing process.

Referring to FIG. 10, this mainly chemical polishing process is substantially identical to that in Embodiment 3 except for the configuration of the polishing pad 620. Thus, there is no discussion with respect to the chemical polishing process.

Therefore, as in the above-mentioned Embodiment 3, the edge portion of the wafer 605 may not be damaged in rotating the wafer 605. Also, the difference between the profile at the polished central portion of the wafer 605 and the profile at the polished edge portion of the wafer 605 can be remarkably reduced so that the wafer 605 is uniformly polished.

FIG. 11 illustrates the polished regions of the wafers 505 and 605 polished by the polishing pads 520 and 620, when the wafers 505 and 605 are not reciprocally moved. The wafers 505 and 605 are divided into a central region I and an edge region II. The central region I makes contact with the second pads 524 and 624. The edge region II makes contact with the first pads 522 and 622 or the third pads 526 and 626. Since the second pads 524 and 624 are rotated at a speed different from that of the first pads 522 and 622 or the third pads 526 and 626, the interface between the central region I and the edge region II may not be uniformly polished.

FIG. 12 illustrates the polished regions of the wafers 505 and 605 polished by the polishing pads 520 and 620, when the wafers 505 and 605 are reciprocally moved. The wafers 505 and 605 are divided into a central region III, a middle region IV and an edge region V. The central region III makes contact with the second pads 524 and 624. The edge region V makes contact with the first pads 522 and 622 or the third pads 526 and 626. The middle region IV selectively makes contact with the second pads 524 and 624 and the first pads 522 and 622 or the third pads 526 and 626. A width of the middle region IV may vary in accordance with the reciprocating speed of the wafers 505 and 605. Thus, the interface between the central region III and the edge region V may be uniformly polished so that the polishing uniformity of the wafers 505 and 605 may be improved.

Embodiment 5

FIG. 13 is a flow chart illustrating a method of polishing a wafer in accordance with a fifth embodiment of the present invention.

Referring to FIG. 13, in step S110, the polishing heads 530 and 630 engage the wafers 505 and 605. The polishing heads 530 and 630 are downwardly moved to make contact the wafers 505 and 605 with the polishing pads 520 and 620, respectively. Here, the centers of the wafers 505 and 605 make contact with the second pads 524 and 624 of the polishing pads 520 and 620.

In step S120, the slurries 542 and 642 are provided from the slurry lines 540 and 640 to the polishing pads 520 and 620, respectively. Since the slurries 542 and 642 may not flow between the first, second and third pads of the polishing pads 520 and 620, the slurries 542 and 642 are provided to the first, second and third pads, respectively. Since the polishing pad 520 of the rotary type apparatus 500 is rotated, the slurry 542 is provided to a position of the polishing pad 520 that is adjacent to the polishing head 530 for smoothly providing the slurry 542 to the front side of the wafer 505.

In step S130, the second pads 524 and 624 are rotated at a speed faster than that of the first pads 522 and 622 or the third pads 526 and 626. Here, the first, second and third pads of the polishing pads 520 and 620 are rotated in a substantially same direction. The polishing pads 520 and 620 are reciprocally moved to polish the wafers 505 and 605.

In step S140, when the polishing pads 520 and 620 are moved, the polishing heads 530 and 630 are rotated to rotate the wafers 505 and 605, thereby uniformly polishing the wafers 505 and 605, respectively.

When the polishing pads 520 and 620 are moved, and the wafers 505 and 605 are moved and rotated, the wafers 505 and 605 are reciprocally moved between the first, second and third pads of the polishing pads 520 and 620 to more uniformly polish the wafers 505 and 605. The reciprocal movements of the wafers 505 and 605 may be executed by reciprocally moving the polishing pads 520 and 620 or the polishing heads 530 and 630. Alternatively, the reciprocal movements of the wafers 505 and 605 may be executed by reciprocally and simultaneously moving the polishing pads 520 and 620 and the polishing heads 530 and 630.

Also, the centers of the wafers 505 and 605 are reciprocally moved from the interface between the first pads 522 and 622 and the second pads 524 and 624 to the interface between the second pads 524 and 624 and the third pads 526 and 626. The reciprocal movements of the wafers 505 and 605 may be in the form of uniform motion and/or accelerated motion. Also, the reciprocal speeds of the wafers 505 and 605 may be controlled.

In step S150, when the wafers 505 and 605 are polished, a portion of the wafers 505 and 605 having a relatively low polishing selectivity makes contact with a portion of the polishing pads 520 and 620, which is relatively rapidly rotated. On the contrary, other portions of the wafers 505 and 605 having a relatively high polishing selectivity make contact with other portions of the polishing pads 520 and 620, which are relatively slowly rotated by controlling positions of the wafers 505 and 605.

Additionally, when the wafers 505 and 605 are polished, the pad conditioners 550 and 650 remove the byproducts to maintain states of the polishing pads 520 and 620.

Embodiment 6

Referring to FIG. 14, in step S210, the polishing heads 530 and 630 hold the wafers 505 and 605. The polishing heads 530 and 630 downwardly move to make contact the wafers 505 and 605 with the polishing pads 520 and 620. Here, the centers of the wafers 505 and 605 make contact with the second pads 524 and 624 of the polishing pads 520 and 620.

In step S220, the slurries 542 and 642 are provided from the slurry lines 540 and 640 to the polishing pads 520 and 620. Since the slurries 542 and 642 may not flow between the first, second and third pads of the polishing pads 520 and 620, the slurries 542 and 642 are provided to the first, second and third pads, respectively. Since the polishing pad 520 of the rotary type apparatus 500 is rotated, the slurry 542 is provided to a position of the polishing pad 520 that is adjacent to the polishing head 530 for smoothly providing the slurry 542 to the front side of the wafer 505.

When the slurries 542 and 642 are provided, the polishing pads 520 and 620 are moved to polish the wafers 505 and 605. The polishing heads 530 and 630 are then rotated to uniformly polish the wafers 505 and 605. Also, the wafers 505 and 605 are reciprocally moved between the first, second and third pads of the polishing pads 520 and 620. Further, the centers of the wafers 505 and 605 are reciprocally moved from the interface between the first pads 522 and 622 and the second pads 524 and 624 to the interface between the second pads 524 and 624 and the third pads 526 and 626.

In step S230, the wafers 505 and 605 are divided into a central region III making contact with the second pads 524 and 624, a middle region IV selectively making contact with the second pads 524 and 624 and the first pads 522 and 622 or the third pads 526 and 626, and an edge region V making contact with the first pads 522 and 622 or the third pads 526 and 626. A width of the middle region IV may vary in accordance with the reciprocating speed of the wafers 505 and 605. Thus, the interface between the central region III and the edge region V may be uniformly polished so that the polishing uniformity of the wafers 505 and 605 may be improved.

Additionally, when the wafers 505 and 605 are polished, the pad conditioners 550 and 650 remove the byproducts to maintain states of the polishing pads 520 and 620.

According to one aspect of the present invention, the polishing pad is divided into, for example, at least three portions that are rotated in a substantially same direction. Also, the any one of the three portions may be adapted to rotate at a speed different from that of the rest portions. Thus, the portions of the polishing pads may have controllable speeds so that the wafer may be uniformly polished.

Further, the width and the speed of the wafer are controlled to improve the polishing uniformity of the wafer.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A polishing pad assembly comprising:

a polishing pad for polishing a wafer, the polishing pad divided into multiple portions that are adapted to rotate in a substantially same direction, at least one of the portions of the polishing pad adapted to rotate at a speed different than the other portions; and

a driving unit for moving the polishing pad.

2. The polishing pad assembly of claim 1, wherein the polishing pad is adapted to reciprocally move to polish the wafer, and the wafer is adapted to reciprocally move between the portions of the polishing pad.

3. The polishing pad assembly of claim 2, wherein the polishing pad is adapted to reciprocally move so that the center of the wafer is located between an innermost interface of adjacent portions of the polishing pad and an outermost interface of adjacent portions of the polishing pad.

4. The polishing pad assembly of claim 1, wherein the driving unit comprises at least three annular portions having diameters different from each other, and the portions of the polishing pad corresponding to the annular portions of the driving unit are attached to the annular portions of the driving unit, respectively.

5. The polishing pad assembly of claim 1, wherein the driving unit comprises at least three rollers having substantially the same diameter, and the portions of the polishing pad comprise belts which are wound about the rollers.

6. The polishing pad assembly of claim 1, wherein the polishing pad is divided into an odd number of portions.

7. An apparatus for polishing a wafer comprising:

a polishing pad for polishing the wafer, the polishing pad being divided into multiple portions that are adapted to rotate in a substantially same direction, at least one of the portions of the polishing pad adapted to rotate at a speed different than the other portions;

a driving unit for moving the polishing pad; and

a polishing head for maintaining the side of the wafer to be polished engaged with the polishing pad, for contacting the polished surface of the wafer with the polishing pad, and for rotating the wafer.

8. The apparatus of claim 7, wherein the polishing pad is reciprocally moved to polish the wafer, and the wafer is reciprocally moved between the portions of the polishing pad.

9. The apparatus of claim 8, wherein the polishing pad is reciprocally moved so that the center of the wafer is located between an innermost interface of adjacent portions of the polishing pad and an outermost interface of adjacent portions of the polishing pad.

10. The apparatus of claim 8, wherein the polishing head is reciprocally moved to move the polishing pad and the polishing head relative thereto.

11. The apparatus of claim 8, wherein the polishing pad is reciprocally moved to move the polishing pad and the polishing head relative thereto.

12. The apparatus of claim 7, wherein the driving unit comprises at least three annular portions having diameters different from each other, and the portions of the polishing pad corresponding to the annular portions of the driving unit are attached to the annular portions of the driving unit, respectively.

13. The apparatus of claim 7, wherein the driving unit comprises at least three rollers having substantially the same diameter, and the portions of the polishing pad comprise belts which are wound about the rollers.

14. The apparatus of claim 7, further comprising a slurry line for providing a polishing slurry to the polishing pad.

15. The apparatus of claim 14, wherein the slurry line is positioned adjacent to the polishing head to provide the polishing slurry to a location on the polishing pad adjacent to the polishing head.

16. The apparatus of claim 14, wherein the slurry line provides the polishing slurry to each of the portions of the polishing pad.

17. The apparatus of claim 7, wherein the polishing pad is divided into an odd number of portions.

18. A method of polishing a wafer comprising:

providing the wafer to be polished, a polishing head engaged with a polishing pad, the polishing pad being divided into multiple portions; and

moving the polishing pad to polish the wafer, at least one of the portions of the polishing pad having a speed different from that the remaining portions of the polishing pad, the portions of the polishing pad being moved in a substantially same direction.

19. The method of claim 18, wherein a first portion of the wafer having a relatively lower polishing selectivity makes contact with the portion of the polishing pad having a relatively rate of speed, and a second portion of the wafer having a relatively higher polishing selectivity makes contact with the portion of the polishing pad having a relatively lower speed.

20. The method of claim 18, further comprising rotating the wafer engaging the polishing pad.

21. The method of claim 18, further comprising moving the polishing head and the polishing pad to reciprocally move the wafer between the portions of the polishing pad.

22. The method of claim 21, wherein the polishing pad is reciprocally moved so that the center of the wafer is located between an innermost interface of adjacent portions of the polishing pad and between an outermost interface of adjacent portions of the polishing pad.

23. The method of claim 21, wherein the polishing head is reciprocally moved to move the polishing pad and the polishing head relative thereto.

24. The method of claim 21, wherein the polishing pad is reciprocally moved to move the polishing pad and the polishing head relative thereto.

25. The method of claim 18, wherein the respective portions of the polishing pad have concentrically annular shapes having different diameters.

26. The method of claim 18, wherein the respective portions of the polishing pad have a belt shape.

27. The method of claim 18, further comprising providing slurry to the polishing pad.

28. The method of claim 27, wherein the slurry is provided to a location on the polishing pad adjacent to the polishing head.

29. The method of claim 27, wherein the slurry is provided to each of the respective portions of the polishing pad.

30. The method of claim 18, wherein the polishing pad is divided into an odd number of portions.

31. A method of polishing a wafer comprising:

providing the wafer to be polished, a polishing head engaged with a polishing pad, the polishing pad being divided into at least three portions; and

polishing the wafer to form a first region polished by a first portion of the polishing pad, a second region polished by a second portion of the polishing pad, and a third region polished by the first and second portions of the polishing pad.

32. The method of claim 31, wherein polishing the wafer comprises:

rotating the polishing head; and

moving the polishing pad and the polishing head relatively to the wafer so as to reciprocally move the wafer between the first and second portions of the polishing pad.

33. The method of claim 32, wherein the polishing pad is reciprocally moved so that the center of the wafer is located between an innermost interface of adjacent portions of the polishing pad and an outermost interface of adjacent portions of the polishing pad.

34. The method of claim 32, wherein the polishing head and the polishing pad are moved relatively to the wafer so as to form the third region.

35. The method of claim 31, wherein the first region corresponds to a central region of the wafer, the second region corresponds to an edge region of the wafer, and the third region corresponds to a region between the central region and the edge region.

36. The method of claim 31, wherein the first portion of the polishing pad has a speed different from that of the second portion of the polishing pad.

37. The method of claim 31, further comprising providing a polishing slurry to the polishing pad.

38. The method of claim 31, wherein the polishing pad is divided into an odd number of portions.