Achieving the 6 key performance metrics from the SubFab to the Cleanroom
How do vacuum and abatement systems impact Fab metrics?
Vacuum pumps and abatement systems are a critical part of the semiconductor manufacturing process. Regardless of the device type or process node, there are hundreds, even thousands of vacuum pumps and abatement systems in the SubFab.
Up until recently, they have also been largely ignored as a possible source of process and yield variability. However, as other, larger and more direct Fab-based detractors are being eliminated or controlled, the search is on for the “hidden variables”. The SubFab equipment is on the list of suspects to increase performance and drive competitive advantage.
Semiconductor manufacturing is already a highly digitalised and automated environment, where Smart Manufacturing tools and Industrie 4.0 principles are coming into play. The complexity of the manufacturing process, the dynamic nature of day-to-day operations and the continual need to advance and improve emphasises the need for a data driven approach.
What are the common metrics used by semiconductor Fabs?
Safety, Quality, Delivery, Cost, People and Environment (SQDCPE) are metrics widely used to measure and track performance.
Safety
The vacuum and abatement system funnels all hazardous materials used in semiconductor processing to render them harmless for disposal. Many of these gases and by-products are toxic, flammable, pyrophoric, or environmentally damaging and pose significant threats to the health and safety of Fab personnel and the surrounding community, if not handled with great care. It is important to review key performance indicators (KPIs) for safety and how they impact both the Fab and the SubFab. Common indicators of safety are time lost due to injuries (lost workday case rate or LWCR) and the total number of recordable safety incidents (total recordable case rate or TRCR).
Quality
As the number of processing steps required by leading edge processes has grown, so has the impact of vacuum and abatement on line and even die yield. Equipment selection and maintenance decisions are critical at each process step. Making reactive choices can create inefficiency, process tool downtime and critical safety hazards. What may seem like minor improvements to yield can have a huge impact on KPIs.
Delivery
Thousands of hours of process tool time is still being lost each year, due to unplanned maintenance. If an unexpected event in the SubFab causes a tool or chamber to be down, wafers can be lost or delayed when waiting for the tool and the cycle time for those wafers will increase.
Cost
The impact on wafer cost can be direct or indirect. The indirect costs, including the opportunity cost of lost production on process tools far outweighs direct costs, especially if the down tool is a bottleneck tool.
People
Creating integrated circuits requires many people with a wide range of skills and both theoretical and hands-on knowledge. These skills range across physics and chemistry, materials science, electrical engineering and electronics, mechanical engineering, control systems and more.
Environment
Many measures are needed to achieve sustainability objectives – energy efficiency programs, strategic renewable energy initiatives, reduction of greenhouse gas emissions and established climate change countermeasures.
