Ways of Addressing Interconnect-Level ESH Issues

With advanced VLSI devices come more metal levels, a variety of low-k dielectrics and greater use of chemicals, slurries and ultrapure water in an increasingly "wet" back-end-of-line that used to rely more heavily on dry processing. All of the new material changes, along with accelerated roadmaps, put a strain on engineers and managers who must address environment, safety and health (ESH) issues in the fab. The key lies in assessing and addressing all aspects of material use — from initial supply to waste stream management — before a new material is brought into production use.

Today's ESH issues pertain to the increasing use of wet chemical processes in electrochemical deposition (ECD), use of solvents in spin-on dielectric solutions, high volumes of slurry and cleaning chemistries in CMP, and the need to replenish, reuse or even recycle solvents, acids and ultrapure water. As new materials are rapidly brought into pilot and production lines, IC and chemical companies must quickly prepare so that ESH issues do not hinder a company's ability to ramp up new processes. According to the latest International Technology Roadmap for Semiconductors (ITRS), the industry needs to develop environmentally friendly plating baths and solvents, devise methods of reusing or recycling ECD solutions and CMP slurries, and tighten process control and processes to approach zero waste in wet and dry processes.

Engineers need to consider not only the chemicals used in the process, for instance, but also the waste created by mixing process streams, interactions with equipment components and other chemicals, etc. With increasing levels of metal and the addition of new materials, efforts to optimize the treatment, process control and quantity of wet chemical processes used become important. In the area of dry processes, the industry continues to battle with the issue of PFC (perfluorocarbon) emissions from chamber cleaning and some deposition processes. If a PFC cannot be eliminated from a process, the alternative is to develop a zero-emission process that fully utilizes the gas.

Careful screening during the early stages of development is essential. Reaction product emissions, health and safety properties, materials compatibility with equipment and other chemical components, flammability and reactivity must be predetermined to ameliorate ESH impact. For more information, see the 2001 ITRS section on ESH. Also see "Advanced Gates Present New ESH Issues".