News Column

Patent Application Titled "Polishing Pad and Multi-Head Polishing System" Published Online

February 13, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors Tu, Wen-Chiang (Mountain View, CA); Zhang, Jimin (San Jose, CA), filed on July 19, 2012, was made available online on January 30, 2014.

No assignee for this patent application has been made.

Reporters obtained the following quote from the background information supplied by the inventors: "An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. One fabrication step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. For certain applications, the filler layer is planarized until the top surface of a patterned layer is exposed. A conductive filler layer, for example, can be deposited on a patterned insulative layer to fill the trenches or holes in the insulative layer. After planarization, the portions of the metallic layer remaining between the raised pattern of the insulative layer form vias, plugs, and lines that provide conductive paths between thin film circuits on the substrate. For other applications, such as oxide polishing, the filler layer is planarized until a predetermined thickness is left over the non-planar surface. In addition, planarization of the substrate surface is usually required for photolithography.

"Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. An abrasive polishing slurry is typically supplied to the surface of the polishing pad.

"The polishing pad typically includes two layers, including a cover layer and a softer backing layer. The cover layer can be a polyurethane with pores, e.g., IC-1000, and the backing layer can be a more compressible material, e.g., SUBA-4. However, a variety of other pad structures are possible, e.g., single-layer polishing pads. The polishing pad is typically grooved in to distribute the polishing slurry evenly below the substrate. Typical grooving patterns include concentric circular grooves and orthogonal linear grooves that form a rectangular cross-hatched pattern."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "In some CMP systems, multiple substrates are polished simultaneously on a single polishing pad. Although the substrates are oscillated laterally across the polishing pad during the polishing operation, there can be a region near the center of the polishing pad that is not contacted by the substrate and not used for polishing. However, by-products of the polishing operation such as debris or slurry can collect in the grooves in the center of the pad. When the polishing pad is rinsed, these by-products can be released back to the portion of the pad used for polishing, causing scratching or other defects in a subsequent polishing operation. However, by having a different grooving pattern in the center region of the pad, release of the by-products can be reduced.

"In one aspect, a chemical mechanical polishing system includes a polishing pad, a platen to support the polishing pad, the platen rotatable about a center axis, a rotatable first carrier head configured to hold a first substrate against the polishing pad, the first carrier head including a first retaining ring, a rotatable second carrier head configured to hold a second substrate against the same polishing pad at the same time that the first carrier head holds the first substrate against the polishing pad, the second carrier head including a second retaining ring, a first actuator to sweep the first carrier head laterally across the polishing pad while the first substrate contacts the polishing pad, a second actuator to sweep the second carrier head laterally across the polishing pad while the second substrate contacts the polishing pad, and a controller configured to cause the first actuator to sweep the first carrier head between a first position closer to the center axis and a second position farther from the center axis and to cause the second actuator to sweep the carrier head between a third position closer to the center axis and a fourth position farther from the center axis. A polishing surface of the polishing pad includes a center region and an annular region surrounding the center region, the center region having a first grooving pattern and the annular region having a second grooving pattern different than the first grooving pattern, and wherein a radius of the center region is equal to or less than a distance from the center axis to a closest outer edge of the first retaining ring when the first carrier head is in the first position and the second retaining ring when the second carrier head is in the third position.

"Implementations can include one or more of the following features. The first grooving pattern may be configured to provide a lower resistance to outward slurry flow than the second grooving pattern. The polishing surface in the center region may have no grooves. The polishing surface in the center region may have at least one groove, and the first grooving pattern may differ from the second grooving pattern. The at least one groove may include a spiral groove. The spiral grove may spiral in a first direction from outside inwardly, and the controller may be configured to cause the motor to rotate in the first direction while the first substrate and the second substrate are being polished. The polishing surface in the center region may have a first plurality of grooves having a first pitch and the polishing surface in the annular region may have a second plurality of grooves having a second pitch that is less than the first pitch. The annular region may have a plurality of concentric circular grooves. The annular region may have a first plurality of linear grooves and a second plurality of linear grooves orthogonal to the first plurality of linear grooves. The radius of the center region may be equal to the distance from the center axis to the closest outer edge. The radius of the center region may be less than the distance from the center axis to the closest outer edge. The first position and the third position may be equidistant from the center axis. The polishing system may include a track, a first carriage supported by the track, and a second carriage supported by the track. The first carrier head may be suspended from the first carriage and the second carrier head may be suspended from the second carriage. The track may form an arcuate path over the polishing pad.

"Implementations can include one or more of the following potential advantages. Release of by-products from a center region of the polishing pad can be reduced. Defects on the substrate can be reduced, and yield can be increased.

"The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other aspects, features and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

"FIG. 1 illustrates a plan view of an example of a polishing apparatus.

"FIG. 2 illustrates a schematic cross-sectional view of an example of a polishing apparatus.

"FIG. 3 illustrates a plan view of a polishing pad illustrating possible positions for the substrates.

"FIGS. 4A-4D are a plan views of a polishing pad illustrating example grooving patterns.

"Like reference symbols in the various drawings indicate like elements."

For more information, see this patent application: Tu, Wen-Chiang; Zhang, Jimin. Polishing Pad and Multi-Head Polishing System. Filed July 19, 2012 and posted January 30, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=1980&p=40&f=G&l=50&d=PG01&S1=20140123.PD.&OS=PD/20140123&RS=PD/20140123

Keywords for this news article include: Patents.

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Source: Politics & Government Week


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