Michael V. Aquilino

Integrated metrology's role in Gas Cluster Ion Beam etch

Shrinking process windows for advanced processing of complex devices, sub-14nm, require advanced topography control. Within-wafer topography variations impact the uniformity of subsequent layers and can affect yield. Process tools can generally control global uniformity across wafer, but are not well equipped to fine-tune the local (reticle-to-reticle) topography. Advanced new process tools such as the Gas Cluster Ion Beam (GCIB) offer a promising path for improving topography within wafer and from wafer-to-wafer [1, 2]. GCIB uses a highly localized focus beam controlled by location specific processing (LSP) algorithms to achieve the needed planarization corrections. In order to be effective, the LSP algorithms require wafer-specific knowledge on the incoming topography distribution. The beam dwells in different locations on the wafer for different amounts of time in order to vary the amount of material removed. Therefore, the performance of local planarization tools depends on the availability and quality of the metrology data. Integrated scatterometry-based metrology (IM) is the workhorse metrology enabler for inline APC (Advanced Process Control) and monitoring solutions for the Chemical Mechanical Planarization (CMP) and Reactive Ion Etching (RIE) processes. While maintaining equivalent performance to their standalone (SA) scatterometry siblings, IMs are typically mounted on the GCIB tool and dedicated to provide pre and post-process measurements for wafers processed on the tool. They enable real-time per-wafer adjustments to within-lot process knobs due to their proximity to the process.