Inventor: Harvey Pinder

RELATED APPLICATIONS This patent application is claiming the benefit of the U.S. Provisional Application having an application number of 60/578,987, filed June 11, 2004, in the name of Harvey Pinder, and entitled "SINGLE COMPONENT PAD BACKER FOR POLISHING HEAD OF AN ORBITAL CHEMICAL MECHANICAL POLISHING MACHINE".

BACKGROUND OF THE INVENTION 1. Field of the Invention: The present invention relates to an orbital chemical mechanical polishing machine, and more particularly, to a new single component flexible pad backer for the polishing head of an orbital chemical mechanical polishing machine.

2. Description of the Prior Art: Chemical mechanical polishing is utilized in the fabrication of a semiconductor wafer in order to planarize both dielectric and metallization layers within the semiconductor wafer. The uniformity or planarization of each layer is critical for several reasons. A planar layer reduces the s'tep height to facilitate the subsequent photolithography process. Additionally, a planar layer reduces the likelihood of accidental coupling of active conductive devices between different metallization layers. For these reasons, chemical mechanical polishing (CMP) has become the industry standard by which to achieve the most uniform or planar surface of each layer in the semiconductor fabrication process. Chemical mechanical polishing (CMP) typically involves mounting a wafer on a holder (carrier), facing down, and rotating or, orbiting the wafer against a polishing pad mounted on a rotating platen or orbiting pad backer. Slurry containing chemical and abrasive components is applied to the polishing pad between the pad surface and the face of the wafer. The slurry interacts with the surface layer of the wafer and thereby physically removes a portion of the surface layer in order to obtain a planar surface. In the design of an orbital CMP system, the pad backer is mounted above an inflatable air bladder which is used to control the amount of pressure applied during the polishing of the wafer. Therefore, the flexibility of the pad backer becomes critical in the ability of achieving the desired planer surface of the semiconductor wafer. As shown in Fig. 1, the conventional multi-component pad backer (100) comprises of a flexible urethane type material (101) physically mounted or attached to a metal plate (102) by gluing and riveting (105) the urethane to the metal plate. Additionally, the urethane portion of the pad backer has grooves (103) scribed into the top surface to allow for expansion and contraction of the pad backer during the polishing process. Holes (104) are drilled .through the entire assembly to allow the polishing liquid to pass through the pad backer to the top surface of the polishing pad. The backside of the pad backer's metal plate is smooth and therefor requires a screen or mesh material to be placed between the air bladder and the pad backer to accommodate the flow of liquid from the bottom to the top of the pad backer and polishing pad. In Fig. 2, the backside of the conventional multi-component pad backer (200) comprises of a metal plate (201 ) and rivets (202) utilized to hold the metal plate to the urethane portion of the pad backer. Also shown, are the holes (203) required for liquid transfer to the topside of the pad backer. The conventional multi-component pad backer design reduces the flexibility of the pad backer through the use of the metal plate that the urethane is portion of the pad backer is mounted to. By reducing the flexibility of the pad backer, the planarization efficiency or uniformity of the polished surface layer of the wafer is affected. A single component, flexible packer design greatly increases the flexibility of the pad "backer and thereby improves the resulting uniformity of the polished surface layer of the wafer to a more desirable level. Additionally, by comprising the pad backer of a single material other issues normally related to the usability of the pad backer can be improved. In the conventional multi-component pad backer, the usable life of the pad backer is reduced due to the metal plate bending or deforming to the point that a planar or uniform surface on the wafer cannot be achieved. Furthermore, users of the conventional multi-component pad backer have noted that the glue layer between the urethane and metal portions of the pad backer breaks down during use and results in delaminating of the pad backer. Either of these situations has a negative impact of the planarization of the wafer surface and renders the pad backer unusable. For the previously mentioned reasons, a new single component flexible urethane or similar material pad backer is invented. By the use of single component the issues of deforming or delaminating are eliminated and thereby extending the usable life of the pad backer. Additionally, by utilizing only the urethane or similar material for the pad backer, the flexibility of the pad backer is greatly increased and results in a more planar or uniform polished surface layer of the wafer. Furthermore, incorporating channels or grooves for liquid transport into the backside of the pad backer eliminates the need for a screen or mesh material to be placed between the air bladder and pad backer.

SUMMARY OF THE INVENTION In accordance with one embodiment of the present invention, it is an object of the present invention to provide a new single component flexible pad backer. It is another object of the present invention to provide a new single component flexible pad backer that overcomes the problems associated with conventional multi-component pad backer. It is still another object of the present invention to provide a single component flexible packer design that increases the flexibility of the pad backer and thereby improves the resulting uniformity of the polished surface layer of a wafer to a more desirable level. It is yet another object of the present invention to provide a single component flexible packer design that increases the useable life of the packer since in the conventional multi-component pad backers, the usable life of the pad backer is reduced due to the metal plate bending or deforming to the point that a planar or uniform surface on the wafer cannot be achieved. It is still another object of the present invention to provide a single component flexible packer design that increases the useable life of the packer since in the conventional multi-component pad backers, since users of the conventional multi-component pad backer have noted that the glue layer between the urethane and metal portions of the pad backer breaks down during use and results in delaminating of the pad backer. It is another object of the present invention to provide a single component flexible packer design that xncorporates channels or grooves for liquid transport into the backside of the pad backer thereby eliminating the need for a screen or mesh material to be placed between the air bladder and pad backer.

BRIEF DESCRIPTION OP THE EMBODIMENTS In accordance with one embodiment of the present invention a pad backer for a polishing head of an orbital chemical mechanical polishing (CMP) machine is disclosed. The pad backer comprises a flexible pad member. A plurality of holes are formed through the flexible pad member. The holes are used to accommodate a flow of a polishing liquid from the underside of the flexible pad member. A plurality of grooves are formed on a backside of the flexible pad. The grooves are used for transferring the polishing liquid to the plurality of holes. In accordance with another embodiment of the present invention a pad backer for a polishing head of an orbital chemical mechanical polishing (CMP) machine is disclosed. The pad backer has a flexible plate member. The flexible plate member improves upon achieving a uniform surface layer of a semiconductor wafer being polished. A plurality of holes formed through the flexible plate member to accommodate flow of a polishing liquid from the underside of the flexible plate member to a top surface of the flexible plate member. A plurality of grooves are formed on a backside of the flexible pad for transferring the polishing liquid to the plurality of holes. The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features believed characteristic of the invention are set forth m the appended claims. The invention itself, as well as a preferred mode of use, and advantages thereof, will best be understood by reference to the following detailed description of illustrated embodiments when read in conjunction with the accompanying drawings. Fig. 1 is a top view of a conventional multi-component pad backer for an orbital chemical mechanical polishing machine. Fig. 2 is a bottom view of a conventional multi-component pad backer for an orbital chemical mechanical polishing machine. Fig. 3 is a top view of a single component flexible pad backer for an orbital chemical mechanical polishing machine of the present invention. Fig.4 is a bottom view of a single component flexible pad backer for an orbital chemical mechanical polishing machine of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 1, a conventional multi-component pad backer (100) is shown. The multi-component pad backer (100) is comprised of a flexible type material (101) physically mounted and attached to a metal plate (102) . The flexible type material (101) is generally mounted and attached to the metal plate (102) by gluing and riveting (105) the flexible type material (101) to the metal plate (102) . The flexible type of material (101) of the multi-component pad backer (100) has grooves (103) scribed into the top surface of the flexible type of material (101) . The grooves are used to allow for expansion and contraction of the multi-component pad backer (100) during the polishing process. Holes (104) are drilled through the multi-component pad backer (100) . The holes are used to allow the polishing liquid to pass through the multi-component pad backer (100) to the top surface of the polishing pad. The backside of the pad backer's metal plate (102) is smooth and therefor requires a screen or mesh material to be placed between the air bladder and the pad backer (100) to accommodate the flow of liquid from the bottom to the top of the pad backer (100) and polishing pad. In Fig. 2, the backside of the conventional multi-component pad backer (100) is shown. As may be seen, the pad backer 100 comprises the metal plate (102) and rivets (105) utilized to hold the metal plate to the urethane portion of the pad backer. Also shown, are the holes (104) required for liquid transfer to the topside of the pad backer. The conventional multi-component pad backer disclosed above reduces the flexibility of the pad backer since the metal plate is mounted to the flexible urethane portion. By reducing the flexibility of the pad backer, the planarization efficiency or uniformity of the polished surface layer of the wafer is affected. Referring to Fig. 3 and 4, a single component flexible pad backer (300) for an orbital chemical mechanical polishing (CMP) machine is shown. Fig. 3 is a top view of the single component flexible pad backer (300) and Fig. 4 is a bottom view of the single component flexible pad backer (300) for an orbital chemical mechanical polishing (CMP) machine according to a preferred embodiment of the present invention. As shown in Fig. 3, a top view of a single component flexible pad backer (300) is provided. The single component flexible pad backer (300) comprises a molded urethane or similar type flexible material. The single component flexible pad backer (300) has a smooth surface. Holes (301) are formed through the pad backer (300) to accommodate tile flow of the polishing liquid from the underside of the pad backer (300) to the top surface of the polishing pad that will be mounted to the top surface of the described pad backer (300) . The holes (301) are spaced around the pad backer (300) to allow for a fairly uniform flow of polishing liquid from the underside of the pad backer (300) to the top surface of the pad backer (300) . As seen in Fig. 3, the holes (301) are formed in a plurality of rows and columns on the top surface of the pad backer (300) . However, this should not be seen as to limit the scope of the present invention. The holes may be formed in any pattern as long as the holes (301) are spaced around the pad backer (300) to allow for a fairly uniform flow of polishing liquid from the underside of the pad backer (300) to the top surface of the pad backer (300) . As shown in Fig. 4, a bottom view of a single component flexible pad backer (300) is shown. The molded urethane or similar type flexible material has grooves or channels (302) formed into the backside of the described pad backer (300) . The grooves or channels (302) are used to accommodate the flow of the polishing liquid from the underside of the pad backer (300) through the holes (301) without the use of a separate screen or mesh material that is normally placed between the air bladder and the pad backer (300) . The flexibility of the described single component flexible pad backer is much greater than that of any prior art or conventional multi-component pad backers presently used in the orbital chemical mechanical polishing (CMP) machines. This increased flexibility greatly improves upon achieving the desired level of a planar or uniform surface layer of the semiconductor wafer being polished since the pad backer is mounted above an inflatable air bladder which is used to control the amount of pressure applied during the polishing of the wafer. The flexible pad backer allows for a more uniform pressure to be applied to the entire surface of pad backer. Therefore, the flexibility of the pad backer becomes critical in the ability of achieving the desired planer surface of the semiconductor wafer. Additionally, the single component design has fewer parts prone to failure and thereby will provide a longer usable life of the described pad backer. While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.