No assignee for this patent application, patent application serial number 749554, has been made.
Reporters obtained the following quote from the background information supplied by the inventors: "Chemical mechanical polishing (CMP) is one of many processes used in the fabrication of high density integrated circuits. Chemical mechanical polishing is generally performed by moving a substrate against a polishing material in the presence of a polishing fluid. In many polishing applications, the polishing fluid contains an abrasive slurry to assist in the planarization of the feature side of the substrate that is pressed against the polishing material during processing.
"The substrate is generally retained during polishing operations by a polishing head. Conventional polishing heads include a retaining ring bounding a substrate retaining pocket. The substrate may be held in the substrate retaining pocket by stiction to a flexible membrane. The retaining ring prevents the substrate from slipping out from under the polishing head during polishing.
"During polishing, the retaining ring is typically pressed against the polishing pad. A pressurizable chamber in the carrier head can control the vertical position of the retaining ring. The retaining ring is typically formed of a wearable material, and as polishing progresses, the bottom surface of the retaining ring is worn away. Consequently, the thickness of the retaining ring can change over the course of processing multiple substrates.
"Most CMP systems employ a vertically actuatable transfer mechanism, commonly known as a load cup, to transfer substrates between the polishing head and a blade of a robot. The retaining ring and the load cup can include alignment features so that, as the load cup is raised toward the carrier head, the load cup engages the retaining ring and the substrate is aligned with the pocket in the carrier head."
In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "The thickness of the retaining ring can impact the removal profile of the substrate being polished. Without being limited to any particular theory, when the retaining ring is pressed against the polishing pad, assuming a consistent pressure is applied by the chamber in the carrier head, the amount of compression of the polishing pad depends on the retaining ring thickness. Since the retaining ring wears over time, different substrates will undergo different removal profiles, leading to wafer-to-wafer non-uniformity (WTWNU). By monitoring the thickness of the retaining ring, the pressure applied by the carrier head can be adjusted to compensate and improve the WTWNU. The vertical actuation of the load cup can be used to measure the thickness of the retaining ring.
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