College of Engineering
Mechanical Engineering Department
BS in Mechanical Engineering
The chemical mechanical planarization (CMP) of wafers for integrated circuits is an essential – yet expensive – step in their manufacture. CMP machine down-time due to the replacement of process consumables, such as wafer retaining rings, is a significant contributor to the process cost. To reduce the operational cost of their CMP machines, Revasum is interested in exploring new designs and materials for wafer retaining rings to increase their operational lifetime. Background research showed that there is currently no suitable method for testing new retaining ring designs and materials for wear characteristics specific to the CMP process. Available wear testing technologies do not include process-specific elements like slurry or the complex carrier motion, and therefore would not provide useful results. The Cal Poly senior project team is responsible for the design and manufacture of a device to characterize wear of new retaining ring materials under CMP conditions. The characterization of material wear will allow for the comparison of currently available ring materials and aid in the design and implementation of rings which have longer operational life. The team has defined the scope of the project as developing a device to interface with an existing machine (Strasbaugh 6DF optical grinding machine), in order to test material samples with CMP process parameters. Through a process of ideation – which included brainstorming, Pugh matrices, a morphology chart, a weighted decision matrix, and conceptual prototyping – a design was conceived which utilizes a carrier to hold material samples against a polishing pad. Through this carrier, a down-force was applied by the existing pneumatic cylinder on the Strasbaugh 6DF. An adjustable arm holding a pad conditioner has been added to the machine in order to closely model the CMP process and allow for consistency and repeatability across multiple samples. To help the team keep track of tasks and deliverables, a Gantt chart was created. This has been continually updated and serves as a reference to keep the design team on track. To date, the 6DF has been installed on the Cal Poly campus and two iterations of the sample carrier and pad conditioner arm have been manufactured and tested. The team has conducted testing and confirmed that the design has met all functional requirements and specifications.