Rethinking the approach to higher 450mm process gas flows: A case study

The impending increase in silicon wafer diameter from 300mm (the current industry norm) to 450mm will increase the surface area of each wafer by 2.25 times. A worst-case scenario suggests that flammable process gas flow rates required to maintain wafer throughput at acceptable levels would increase by the same scaling factor driving up to 3 times the abatement requirement. The main reason to go to a 450mm wafer size is to lower manufacturing costs, so we need to explore how to best minimize the downstream impact of higher gas flow rates on capital and operating expenditure of tool-support equipment such as vacuum pumps and gas abatement systems, as well as increased subfab space requirements. This paper will consider the likely impact and trade-offs of such gas flow increases on process vacuum systems, which under a “business as usual” model would scale up purge and equipment sizes based on safety multipliers. A case study alternative considers an integrated vacuum and abatement system with a common supervisory control system and monitored joints, allowing purge nitrogen flows and equipment sizes to be reduced, and operational safety to be maintained. Both the technical and cost implications are thoroughly considered. There is an opportunity to enable 450mm capabilities by leveraging novel integration of known technologies to mitigate increased process gas flows.