Sustainability improvements in the real world and simulations

28 February 2024
Hank Hogan
A slide from Elizabeth Elroy's (Micron Technology) talk on sustainability improvements in chip making at SPIE Advanced Lithography + Patterning 2024.
A slide from Emily Gallagher's (imec) talk on sustainability improvements in chip making at SPIE Advanced Lithography + Patterning 2024.

The environmental impacts of chip making and chip use were hot topics at the 2024 SPIE Advanced Lithography + Patterning conference, with presentations showcasing what companies are doing to meet environmental pledges. There also were talks about the rollout of tools to help achieve those goals.

An example of the former can be seen in a presentation on the first day of the conference by Elizabeth Elroy, vice president of global EHS and sustainability at Micron Technology, which makes memory chips and associated products.

Elroy noted that memory demand is exploding, with the total available market surging from $151 billion in 2024 to an estimated $199 billion in 2025. This comes on top of strong growth over the previous 10 years, with bit shipments growing 12x for DRAM and 48x for NAND memory during that time.

Behind this past and expected future growth is an explosion of data. Every connected device — smartphones, tablets, laptops, trackers, and so on — generates data, doing so with every connection. In its own chip manufacturing, Micron produces terabytes of data every day, the output of half a million sensors and a consequence of taking more than 20 million images a day.

“With all this data, you have to have memory,” Elroy said.

The future promises to greatly expand the amount of data generated. Every connected self-driving car, for instance, will produce as much as 20 terabytes of data per day.

Faced with this onslaught of demand, device makers have figured out ways to do more for less. From 2011 to 2022, for example, system bandwidth increased sixfold, and performance went up tenfold while energy consumption dropped by a factor of 10, according to Elroy.

Those improvements need to continue. Beyond that, chip makers must be smarter in how they grow and expand, Elroy noted. “If we do nothing, it [growth] is going to exponentially impact greenhouse gas emissions.”

She outlined Micron’s plans in this area, noting that the company goal is to be at net zero when it comes to emissions by 2050. Getting there involves finding substitutes for high-global warming potential raw materials, such as gases that contain fluorine. Another part of the solution is finding ways to reduce consumption overall while a third avenue to address the problem is by abating emissions. Renewable energy also plays a key role in Micron’s plans.

She noted that new wafer fabs will be built to meet surging demand, and older fabs will need equipment replaced. Both events represent an opportunity to improve sustainability. But that will only happen if the effort to be greener is incorporated into the process from the very beginning.

“We have to think about sustainability as we design,” Elroy said.

However, designing a greener solution can be complicated. Therefore, tools are being developed to help with the task, noted Emily Gallagher, a principal member of the technical staff at the research organization imec. In consumer electronics, the greenhouse gas emissions coming from making the chip overshadow the emissions arising from product use. So, cutting the emissions originating in fabrication is critical to meeting environmental pledges.

Figuring out how best to reduce emissions can be complicated because the semiconductor manufacturing process involves a large number of steps and process-technology choices. In her talk, Gallagher discussed a virtual fab, a model of an actual manufacturing site that can be used to investigate the environmental impact of various options.

“It’s important to use the virtual fab so we can see problems more clearly,” she said.

For instance, Gallagher noted in her talk that lithography patterning is driven by wavelength and numerical aperture (NA), with a shorter wavelength and higher NA the two knobs process designers can turn to make it possible to pattern finer and finer features. Today, EUV scanners have a NA of 0.33, with plans calling for 0.55 NA scanners and with 0.7 NA scanners the next step.

However, what about the impact of the move up in NA on greenhouse gas emissions? In general, Gallagher reported, simulations show the transition will cut those emissions by eliminating process steps. Patterning very fine features with low NA EUV will require two passes through a scanner, whereas high NA EUV machines will be able to achieve the same result in one pass. The result is about a 30 percent reduction in greenhouse gas emissions.

“The future of the industry is bright, and we can make it greener as well,” Gallager said in summarizing the situation.

Hank Hogan is a science writer based in Reno, Nevada.

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