By Phil LoPiccolo, Editor-in-Chief
Efficiencies and cost benefits have been the driving force behind the shift from 200mm to 300mm wafers for semiconductor manufacturing. But in a detailed study presented earlier this month at the third annual International SEMATECH Manufacturing Initiative (ISMI) Symposium on Manufacturing Effectiveness in Austin, TX, Intel found its ramp of 300mm manufacturing has also led to significant environmental benefits — with lessons that could result in further gains if and when the industry moves to 450mm production.
John Harland, principal environmental engineer with Intel’s Environmental Health and Safety business unit, reported that the company was able to essentially meet the environmental goals set out in SEMATECH’s International 300mm Initiative (I300I), which called for tool emissions and utility consumption from 300mm wafers being the same or less than emissions or utilities levels for 200mm wafers — approximately 56% reduction when normalized per cm2 of silicon.
Intel’s study, comparing the environmental performance of a 300mm (90nm) fab with a 200mm (130nm) fab, showed an across-the-board reduction of normalized hazardous air pollutants: (HAPs) by 68%, perfluorocarbons (PFCs) by 50%, and volatile organic compounds (VOCs) by 48% [see image below]. At the same time, Intel was able to reduce its use of ultrapure water (UPW) by 48% and CMP solids by 40%. “When you think that over a two year period, or one generation, we had about a 50% reduction in our emissions — a doubling in our environmental performance,” Harland said. “These are clearly impressive results.”
To conduct the emissions study, Intel drew on data it has been gathering for about five years during ramp-ups to new technologies, which have occurred in roughly two-year intervals. By collecting 200mm and 300mm fab data at the same time into the production ramp of fully ramped fabs, and at the same point on each technology’s learning curve, Harland explained, “we were able to get an accurate comparison of the amount of emissions being produced by the two technologies.”
Intel’s environmental improvements were brought about by a wide range of process changes, according to Harland. For example, HAPs — low-molecular-weight organic materials largely used by Intel in backend process modules — were reduced primarily through abatement improvements, although a chemical substitution approach is planned for the longer term, he said. PFC reductions were driven mainly by conversion to NF3 for thin-film chamber cleans, and by replacing SF6 with new etch chemistries. Lower VOC emissions were largely the result of reductions in the use of volatile solvents — e.g., replacing PGMEA with ethyl lactate, collecting volatile liquid waste from tool tracks to cut down on emissions from evaporation, and improving planned maintenance procedures such as opting to use pre-saturated wipes and a centralized system for collecting used wipes. Meanwhile, UPW use was reduced by wet bench tool design improvements, optimized low-flow technologies, better plumbing in wet benches for recycling, and optimization of plating and planar rinses. Finally, using fewer oxide planar layers and optimizing chemical slurries, particularly for copper CMP processes, reduced the use of CMP solids.
Among the key lessons learned from Intel’s environmental efforts — which would be critical in achieving similar environment improvements if the industry moves to 450mm wafer production — are to get early buy-in from all stakeholders, and to take a holistic approach to integrating processes, tools, materials, and facilities, Harland noted. For example, incorporating more recycling of water and chemicals into fabs will require coordination between process engineers, tool suppliers, material suppliers, and fab designers. Another focus should be to include chemical and energy efficiency as part of the industry’s goals and mission. Much larger 450mm fabs will require rethinking how chemicals are delivered, stored, and transported to the fabs, and how wastes are collected. Standardized environmental and utility metrics will also be essential, he noted, adding that the ability to obtain quality data from tool suppliers was key to helping Intel design more environmentally focused factories. — P.L.