In the 1990s, the semiconductor industry got a big boost in safety, thanks to zeolites. This class of highly porous materials enabled manufacturers to safely store and deliver the highly toxic gases necessary for fabricating silicon chips. Zeolites are but one group of absorbent materials that have long played a role in the purification, abatement, and delivery of ultra-high purity gases and chemicals for electronics manufacturing.
Zeolites were quickly followed by activated carbons, but then the industry appeared to stagnate on offering new material solutions for the most pressing fab needs. Now, a new class of materials, metal organic frameworks (MOFs), are bringing much needed material innovation back into the fab – enabling the semiconductor industry to take the next leap forward.
At NuMat, we have tailor-engineered MOFs out of the millions of possibilities, to develop the next-generation of total-gas solutions in the fab. MOFs are providing a stable platform for storing, stabilizing, and delivering toxic and inherently unstable gases and chemicals. Within the semiconductor industry, such gases are critical to fabricating more advanced computer chips and integrated circuits that are powering society, from our smartphones up to the Internet of Things.
NuMat’s ION-X is the first fully commercialized product line to integrate MOFs, taking something once only produced milligrams at a time and scaling it up by orders of magnitude to engineer materials for key industrial processes. The ION-X product line provides safe, customized, high-capacity solutions for arsine, phosphine, and boron trifluoride, but it’s just the start. The technological innovations and capabilities that have enabled ION-X will continue to open new pathways for the electronics industry in its push for total-fab solutions, as well as other industries that rely on safe, performance-driven solutions.
Defining the Challenge
The semiconductor industry uses a variety of ultra-high purity, hazardous gases in different processes, including doping for ion implantation on silicon chips. Before zeolites and activated carbons, the highly toxic gases were stored in 1% mixtures under high pressure, with 99% of the volume being inert gases. By using adsorbents, industry transitioned to storing 100% neat gases at negative, or subatmospheric pressure, providing significant productivity and safety benefits. The vast majority of fabs now use only adsorbent-based gas systems for the delivery of hydrides such as arsine and phosphine in ion implantation.
But since these advances in safety and storage, innovation in materials for gas solutions has stagnated. The current platforms rely, as they have for the past 25 years, on zeolites and carbon, which have limited structural diversity and tunability. These materials, such as those used in the Entegris SDS products, have uneven pore size, chemical reactivity, and limited flow rates, restricting their applications to only a small subset of gases.
In contrast, MOFs have vast structural diversity with near-infinite numbers of variations that are each highly tunable. First discovered in the late 1990s, MOFs are 3-D nano-crystalline structures comprised of metal-containing nodes connected by organic links. They emerged from academia to become a commercially-viable class of materials with potential applications in energy, specialty chemicals, military, medical, pharmaceutical, and electronics industries. Until now, however, they had yet to be successfully scaled up to commercial applications. ION-X is the first time they have been applied at semiconductor fabs.
Breaking the Capacity Ceiling
In the gas storage and transport market, maximizing gas capacity maximizes value. Every time a cylinder turns over, the process has to be requalified. Minimizing the number of cylinder changeouts reduces the time and monetary investment.
Compared to zeolites and activated carbon adsorbents, MOFs have significantly larger surface areas. NuMat holds the world record for maximum surface area achieved by a MOF at 7,000 square meters per gram. Our ION-X cylinders not only have high-capacity but also adsorb to the gas molecules less strongly than in its non-MOF competitors – yielding more gas in a more constant stream as the cylinder empties and reaches lower pressures.
Customizing to Fit
MOFs offer a large palette to engineer highly tuned, high-performance materials. With millions of different possible structures – which we at NuMat can computationally simulate before ever creating a material in a lab – MOFs offer unique selectivity and specificity for gases that were never previously possible. MOFs have a wide range of pore sizes, allowing them to adsorb more gases. At the same time, unlike activated carbons in which pore size can vary widely within a structure, MOFs act as a uniform scaffold for fitting specific molecules with a narrow distribution. Think of the difference between orderly cubbies versus a crumpled piece of paper: That’s the difference between MOFs and activated carbons.
When we first developed ION-X, we quickly recognized the power of computational simulations in combination with experimental data. We were able to computationally refine the pore volume, surface area, and pore size of our MOFs to achieve maximum gas capacities. We realized that by slightly modifying the pore size, 2 Å, on a first-generation MOF material in development, we were able to create a second-generation material with greater than 25% improvement in gas capacity. It took 14 days to achieve this performance boost, from initial computational modeling to material synthesis and experimental validation.
Offering Novel Solutions
With ION-X, we have shown that MOFs are engineerable, scalable, and capable of creating a shift in the industry comparable to the advent of zeolites in the 1990s. It took just over a year for our team to design and manufacture ION-X, end-to-end.
Our process is global and cross-disciplinary, involving computer science, engineering, materials science, and chemistry. We design, engineer, scale, and pack our MOFs in the United States and then ship the cylinders to a state-of-the-art facility in South Korea to fill with gas. Our current partner is Versum, a top global supplier of electronic materials to semiconductor industry.
The cylinders then go out to fabs worldwide in South Korea, Taiwan, Japan, China, Singapore, Europe, and the United States. Every step of the way includes robust safety and quality controls.
This process has enabled MOFs, for the first time, to be engineered into commercial products in the global marketplace. The process is scalable and replicable with other MOFs and for other industries. Within electronics alone, ION-X opens the door for new applications that continue to evolve the sector.
Many new and varied gases are now available to the electronics industry as it works to advance its next node technology. These gases are often unstable, decomposing over time and during transport. Applications such as lithography and atomic layer deposition in vertical dimensions – to get smaller chips with more power – require dilution for use of these gases. MOFs offer a better solution: They can provide a perfect protective scaffold to reduce this decomposition without dilution, thus improving purity of the gases at their end-use.
For the electronics industry to grow, it must expand into next-generation nanomaterials. A MOF-enabled application platform will support cost-advantaged production, improved yield, and increased safety throughout the fab.
As we continue to identify, create, test, and manufacture new MOFs, we are confident we can engineer solutions to some of the toughest problems in the electronics industry and beyond.
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