Improving Reliability, Yield and Throughput of Chemical-Mechanical-Planarization Through Process Automation and Control

摘要

Two major sources of lost productivity in Chemical-Mechanical Planarization (CMP) Tools are process drift and operator error. Process drift, especially from pad wear, causes drifts away from target dielectric thickness and uniformity, which lead to lost wafers (scrap) and equipment downtime for consumable replacement. Operator error and equipment unavailability results in lost wafers and unnecessary equipment idle time. These factors greatly impact the reliability, yield and throughput of the CMP process. This paper reports on a successful automated run-to-run process control solution for CMP. The system consists of thee major components, namely a tool (a Strasbaugh 6DS-SP or 6ED "Symphony" polisher), a metrology unit (a Nova Measuring Instruments thickness sensor) and a controller (a MiTeX Solutions multi-variate run-to-run controller). The controller automatically uploads metrology information from the metrology unit, utilizes model based control techniques to derive recipe improvements, and automatically downloads these recipe advices to the CMP tool. The controller also contains an alarms monitoring module that detects and reports (to the tool) control and specifications limits violations. One novel aspect of this run-to-run control solution is that it supports fully automated CMP process operation. That is, an operator is not required to monitor or operate the tool. The fully automated run-to-run control solution has been tested on-site at Strasbaugh, while the run-to-run control capability has been applied and tested in production at a US customer site. In both cases, simultaneous control of both process remaining thickness and uniformity were achieved. Reduced process variability, reduced requirement for test wafers, reduced scrap and increased yield were demonstrated.