IMEC’s ‘virtual fab’ models climate impact of chipmaking processes

Technology News | February 28, 2023

By Peter Clarke

Research institute IMEC has developed a ‘virtual fab’ as part of its net-zero modelling platform to help chipmakers assess manufacturing choices for their environmental impact and direct R&D.

This work complements, and is calibrated against, work done in IMEC’s physical fab, where it has explored the reduction of the use of fluorinated etch gases, maximizing extreme ultraviolet (EUV) scanner throughput, and reducing hydrogen and water consumption.

CO2 emissions associated with IC manufacturing are expected to quadruple over the next decade because as manufacturing processes go to finer geometries the environmental impact increases and because the number of wafers processed is increasing.

The modelling platform has quantified the environmental impact of patterning-related process steps for various logic technology nodes. It is notable that the introduction of EUV actually reduced CO2 equivalent emissions at the 7nm node by reducing the complexity of manufacturing through the reduction of patterning steps.

IMEC’s sustainable semiconductor technologies and system (SSTS) program is intended to help chip makers become carbon-neutral at some point in time between 2030 and 2050.

“By applying this ‘virtual fab’ tool, we demonstrated that lithography and etch together are responsible for 45 percent of the Scope 1 and Scope 2 emissions (emissions from owned or operated assets, and from purchased energy, respectively) associated with fabricating 3nm logic wafers,” said Emily Gallagher, a principal member of the technical staff at IMEC, in a statement.

She added: “The comparison of an advanced technology node – N7 in our sample chart – with and without EUV patterning also clearly demonstrated the value of EUV as a solution to limit the CO2 equivalent emissions associated with complex multi-patterning techniques – the 10nm-7nm-5nm transition.”

“In addition, the modelling tool can quantify the gains associated with real fab experiments. For example, lowering the EUV dose by ten percent saves about 0.4 kg CO2eq per wafer. This would result in saving about 40 tons of CO2eq per month in a large fab, equivalent to emissions associated with 100 round trip flights from San Francisco, California to Portland, Oregon.”

One of the steps that IMEC has taken in its own EUV cleanroom is to install a hydrogen recovery system from Edwards. This has enabled IMEC to recover and reuse 70 percent of hydrogen, Gallagher said.

“Additionally, we are increasing focus on low-dose solutions for both 0.33NA and 0.55NA – high NA – EUV lithography, an effort that is also known to reduce costs in lithography. We also identified etch directions for improved sustainability, currently focusing on overall reduction of conventional gas consumption. In a next step, we will, together with our partners, quantify the impact of these proposed solutions in full semiconductor process flows.”

Steven Scheer, senior vice president of advanced patterning, process and materials at IMEC said that the models developed within imec.netzero are benchmarked and validated through partnerships with equipment and material suppliers.

“We are however mindful that not all environmental impact is captured in the carbon equivalent emission metric,” said Scheer. “For example, gas emissions can be hazardous air pollutants (HAPS), and both photoresists and antireflection coatings (ARCs) can contain PFAS (per- and polyfluoroalkyl substances). The carbon-fluorine bond strength of PFAS has contributed to the superior performance characteristics of chemically amplified resists (CARs) for both mature optical and evolving EUV photoresists. However, the bioaccumulation potential has led to a strong societal interest to eliminate their use. Projects like PFAS elimination must be considered in addition to those that lower carbon emissions directly.”