cluster tool

A cluster tool is an integrated equipment platform with a central vacuum transfer chamber and multiple process modules arranged radially, enabling sequential processing without atmospheric exposure. Architecture: (1) Load locks—transition wafers between atmospheric FOUP and vacuum environment; (2) Transfer chamber—central vacuum hub with robotic handler; (3) Process modules—individual chambers for specific process steps; (4) Factory interface—atmospheric front end for FOUP loading. Key advantages: eliminates queue time between process steps (critical for gate stack, barrier/seed), prevents native oxide regrowth between deposition steps, reduces particle contamination from atmospheric exposure, improves process reproducibility. Configuration examples: PVD cluster (degas → preclean → barrier Ta/TaN → seed Cu), etch cluster (main etch → over-etch → ash), CVD cluster (clean → multiple film depositions). Wafer routing: scheduler software optimizes wafer flow through chambers to maximize throughput while meeting process constraints (sequence requirements, queue time limits). Throughput: determined by slowest chamber (bottleneck), typically 20-60 WPH depending on process times. Maintenance: individual chamber PM can be performed while other chambers continue production (partial availability). Transfer chamber: typically 10⁻⁷ to 10⁻⁸ Torr base pressure with turbomolecular pump. Dominant equipment architecture in modern fabs for critical process integration.