Sustainable Chamber Cleaning Solutions:
The Back End of the Front End
Sustainable and production-proven chamber cleaning solutions allow device manufacturers to deliver increased productivity and reduce environmental impact while “taking out the trash.”
In most manufacturing processes, tool cleaning is often an afterthought in the process design and execution. Its impact is generally thought of as little more than housekeeping, akin to sweeping the shop floor at the end of the day. However, in microdevice fabrication, cleaning plays a critical role in the manufacturing process. The choice of technique affects not only device yield, but also fab productivity and environmental impact.
Because cleanliness is such a concern for device manufacturers, production equipment is housed in ultraclean environments, while the substrates themselves are transported in sealed carriers and transferred robotically into vacuum chambers and coater tracks. And no wonder. Microscopic detritus can ruin high-end processors retailing at $1000 a piece, extinguish pixels on the flashiest of flat screens, and darken conversion efficiencies of solar panels to gray skies-only returns.
Despite all of this best practice, deposition processes, such as chemical vapor deposition (CVD), coat parts of the chambers as well as the substrates with their gas-to-solid chemistries. While wafers and glasses move on to further device-building steps, chamber walls and mechanicals accumulate ever thicker and non-homogenous layers of unwanted waste. As a result, timely and efficient cleaning of production chambers to remove device-threatening particles and maintain process stability is required to protect hard-won yields.
Most cleaning processes employ reactive gas-surface chemistries to volatilize the dross. The typical active cleaning agent is free fluorine. However, the traditional gases used to deliver this fluorine tend to be hard-to-abate, perfluorocarbon (PFC) gases, which contribute substantially to global warming.1