Chemical Mechanical Planarization (CMP) In-Situ pad groove monitor through Fault Detection and Classification (FDC) system

Abstract:
A major problem in Chemical Mechanical Polishing (CMP) is to keep a process stable by maximizing consumable lifetime for effective cost of ownership [1-4]. In a high volume production environment non-destructive in-situ measurement of pad properties during process is desirable for early detection of pad key parameters drift and to validate process changes that could impact consumables lifetime. A solution is described, by using a laser profilometry system mounted on a Applied Material Reflexion(TM) polisher and interfaced to a Fault Detection and Classification (FDC) system for real time control of key parameters. The three installed pads are scanned at one time by the laser system during cross rotation, pad surface profiles are acquired and statistically treated locally to determine groove properties (depth, width, density), then values are transferred to the FDC database, together with pad and diamond disk usage information. This is used for: i) Pad Cut Rate (PCR) monitor to find optimal pad conditioning; ii) consumables post-maintenance check: pad groove characteristics and surface reflectivity can be used for pad recognition and validation after tool maintenance; iii) cost of ownership optimization: to shift maintenance approach from preventive, based on usage counter meters, to predictive, based on remaining groove depth, for maximum pad usage. Keywords: chemical mechanical polish, CMP consumables, cost of ownership, polishing pad, laser profilometry, fault detection and classification, predictive maintenance, zero excursion, consumable lifetime, pad groove