Fast chargers for electric cars often switch power with chips made from silicon carbide. Before those chips exist, factories must polish each crystal wafer almost perfectly flat. That step crawls along slowly, because the crystal rates 9.5 on the Mohs hardness scale. Now, a team in China reports a much faster route for silicon carbide wafer polishing. Their copper catalyst hides inside a porous crystal and works in a neutral, water-like slurry. As a result, it removed material about 15 times faster than plain slurry. Chun Cao led the study at the School of Mechanical Engineering, Hangzhou Dianzi University. Partners at Zhejiang Laboratory and Tsinghua University in Beijing also took part. They published the work in Nature Communications on October 28, 2026. Its DOI is 10.1038/s41467-026-79001-x. In addition, the polished test wafers came out extremely smooth and nearly scratch-free.
The Science Explained: How Silicon Carbide Wafer Polishing Works
Chip makers flatten wafers with a step called chemical mechanical polishing, or CMP. A machine presses the wafer against a spinning pad soaked in slurry. That slurry carries tiny glass-like silica beads, which scrub the surface. At the same time, chemicals in the slurry soften the top layer of atoms. A silicon carbide review explains why this tough crystal suits modern power chips. Unfortunately, the same toughness that helps finished devices also resists polishing tools. For this reason, normal CMP removes under 10 nanometers of silicon carbide per minute. One nanometer is roughly one hundred-thousandth the width of a single human hair. Slow removal stretches processing time and raises costs, the authors note. On top of that, harsh scrubbing can leave scratches and hidden damage below the surface. Chemistry therefore must soften the surface, so beads only wipe away soft material.
Fenton Chemistry and the Copper Crystal Sponge
Fig. 1: How the Copper Catalyst Polishes SiC
Here the team used Fenton chemistry, a reaction known for more than a century. In it, a metal catalyst splits hydrogen peroxide into hydroxyl radicals. These radicals rank among the strongest oxidizers in water. They turn the hard surface into a softer oxide skin that beads can wipe away. Next, the team placed copper inside ZIF-8, a metal-organic framework with tiny pores. Think of it as a crystal sponge with an enormous inner surface. Each copper atom sits alone, bonded to both nitrogen and oxygen atoms. This lopsided, or asymmetric, bonding reshapes how the copper atom shares electrons. Because of this change, copper flips more easily between two charge states. Each flip helps split another peroxide molecule. In fact, the surface oxygen atoms grab peroxide much like sea anemone tentacles catch food. As a result, radicals form quickly while the copper stays locked in place.
Challenges and Motivation in Silicon Carbide Wafer Polishing
Semiconductors like silicon carbide drive power electronics, so wafer finishing became a bottleneck. Iron-based Fenton catalysts work best at pH 3 to 4, which is quite acidic. On the other hand, silicon carbide has usually polished best in alkaline slurries. That clash forced engineers to pick a poor compromise. Under alkaline conditions, the radical supply collapses, so the oxidizing boost disappears. In acidic slurries, by contrast, iron ions leak out and can contaminate wafers. Acid can also corrode polishing equipment. Either way, factories must pour in large amounts of pH adjusters. Those extra chemicals raise costs and make waste treatment harder. Not only do loose iron catalysts cycle slowly, but they also need heavy doses. The team wanted one catalyst that works at neutral pH and holds its metal tightly. Such a catalyst could make silicon carbide polishing faster, cleaner and simpler.
Building the Catalyst Step by Step
The recipe stayed fairly simple. First, the team soaked 1 gram of ZIF-8 in copper nitrate dissolved in ethanol. They then heated the mixture for 72 hours. Meanwhile, copper swapped into the framework, and partial reaction with water added oxygen bonds. Afterward, X-ray absorption tests showed no copper-to-copper bonds, so each atom stayed isolated. Even so, inner surface area fell only from 1,715 to 1,485 square meters per gram. Copper made up about 7.9 percent of the catalyst by weight. Computer models then tracked how the new bonds changed the copper’s electrons. The energy needed to split peroxide’s oxygen bond fell from 1.16 to 0.47 electronvolts. In other words, the copper sites split peroxide much more easily. A spin-trap test also counted radicals directly. Cu/ZIF-8 made 17.9 times more radicals than iron oxide nanoparticles. It also beat peroxide alone 131-fold.
Key Findings From the Polishing Tests
Fig. 2: Key Takeaways From the SiC Study
The study then moved silicon carbide wafer polishing onto a lab machine. Each slurry held 10 percent silica beads, 1 percent hydrogen peroxide and a thickener. Cu/ZIF-8 made up just 0.02 percent by weight, and no pH adjusters went in. Square 4H-SiC wafer samples, 1 by 1 centimeter, spun at 120 revolutions per minute. Three samples ran at once, and each test repeated three times. With the catalyst, the material removal rate reached 62.4 nanometers per minute. Without it, the same slurry removed only 4.2 nanometers per minute. That gap equals a 14.9-fold increase. Plain ZIF-8 without copper gave just 4.6 nanometers per minute. Therefore, the copper sites, not the porous particles, produced the speedup. The authors also report that this rate beats many earlier Fenton and field-assisted polishing methods. Even so, these results come from small wafer samples, not full production wafers.
Silicon Carbide Wafer Polishing at Neutral pH
Smoothness improved as well. Before polishing, the wafer samples showed an area roughness of about 6.6 nanometers. After catalyst-free polishing, that value fell to 0.90 nanometers. With Cu/ZIF-8, however, it dropped to 0.55 nanometers. Atomic force microscope scans then measured an average roughness of just 0.36 nanometers. In addition, visible scratches almost vanished. Raman light tests showed the process removed older damage below the surface. However, those tests also found a small density of new stacking faults. These are tiny slips in the crystal’s layer order. Electrical tests also revealed a thicker oxide skin on treated samples. X-ray tests showed about 83 percent of surface silicon-carbon species had oxidized. Finally, used slurry at neutral pH held only 0.045 milligrams of free copper per liter. The authors compare this with the World Health Organization drinking-water limit. That guideline allows 2.0 milligrams per liter.
Limits and the Titanium Alloy Test
The team also tried Ti-6Al-4V, a titanium alloy used in aircraft parts and implants. That test, however, used an acidic slurry at pH 5.5, not a neutral one. Even so, the catalyst thickened the alloy’s oxide skin and improved its polishing. At pH 3, free copper in the waste rose slightly to 0.082 milligrams per liter. Even with these gains, several open questions remain, according to the authors. First, catalysts can lose activity over time, and that deactivation needs study. Second, making large batches of Cu/ZIF-8 at low cost will require careful engineering. Third, the method still needs tests on gallium nitride and diamond. Workers must also use the slurry right after mixing, because the catalyst consumes peroxide quickly. Overall, these results show strong promise in the lab. Factory adoption, by contrast, will depend on scale-up, catalyst lifetime and full-size wafer trials.
Implications: Business, Careers and SiC Wafer Polishing Skills
For industry, faster polishing could trim one of the slowest steps in making power chips. Slurry suppliers could test copper-framework additives in their neutral formulas. If such additives scale up, fabs might use less time and fewer chemicals. Cutting pH adjusters, in turn, would simplify waste treatment. The authors also suggest swapping in iron, manganese or cobalt sites. They name other frameworks, such as UiO-66, HKUST-1 and MIL-101, as future candidates. Tuning the balance of oxygen and nitrogen bonds could further adjust activity. As a result, the work offers a design rule rather than a single recipe. Because of this, startups that design catalysts for semiconductor processing could build on that rule. To see where polishing fits, see how factories make semiconductor chips step by step. Polishing, after all, sits between crystal growth and the many patterning steps that follow.
Careers in Silicon Carbide Wafer Polishing
This study mixes chemistry, computing and machine work, so it maps onto several careers. For instance, a CMP process engineer tunes slurries, pads and pressures on factory tools. A catalysis chemist, by contrast, designs materials such as Cu/ZIF-8. Computational scientists, like the Zhejiang Laboratory coauthor, model electrons with density functional theory. Wafer fabrication technicians run polishing and inspection equipment every day. Precision manufacturing engineers, meanwhile, design machines that hold samples flat and steady. Students who enjoy chemistry can study inorganic chemistry and catalysis. Those drawn to machines can choose mechanical engineering with a focus on precision manufacturing. Materials science and engineering connects both sides. Courses in crystal structure, surface science and microscopy apply directly. Electronics or semiconductor engineering also helps, because device yield depends on clean, flat wafers. Hands-on lab skills, such as atomic force microscopy, give graduates a strong head start.
Conclusion: A Cleaner Path to Smooth Silicon Carbide
This work tackles a stubborn mismatch in chip manufacturing. Not only does the copper sponge work at neutral pH, but it also traps copper. As a result, the slurry needs no acid or base adjusters. In lab tests, it polished silicon carbide 14.9 times faster than a catalyst-free slurry. Surfaces reached about 0.36 nanometers of average roughness, close to atomic smoothness. Still, the tests used 1-centimeter samples, and polishing added a few stacking faults. Next, researchers must check catalyst lifetime, large-batch production and full-size wafers. Meanwhile, other hard materials, such as gallium nitride and diamond, also await testing. For students, the Nature Communications paper shows how electron-level design can solve a factory problem. Chemistry, physics and engineering meet in a single slurry bottle. In time, faster silicon carbide wafer polishing could cut costs for power electronics. Cars, chargers and power grids would all benefit.
References
Cao, C., Zhang, A., Li, X., Wang, X., Shi, C., Meng, F., Feng, J., & Ci, J. (2026). Orbital engineering of asymmetric Cu sites in MOFs for fenton reaction towards atomic surface manufacturing. Nature Communications. Advance online publication. https://doi.org/10.1038/s41467-026-79001-x
Kamiński, M., Król, K., Kwietniewski, N., Myśliwiec, M., Sochacki, M., Stonio, B., Kisiel, R., Martychowiec, A., Racka-Szmidt, K., Werbowy, A., Żelazko, J., Niedzielski, P., Szmidt, J., & Strójwąs, A. (2025). The overview of silicon carbide technology: Status, challenges, key drivers, and product roadmap. Materials, 18(1), 12. https://doi.org/10.3390/ma18010012
The paper backs its claims with matched controls: plain ZIF-8 gave 4.6 nm per minute, close to the 4.2 nm per minute catalyst-free slurry, and a separate test ruled out the particles acting as extra abrasive. The brief reports the removal rate, roughness and copper-leaching numbers accurately and lists the authors' own limitations. Two points needed tightening. The headline said "chips", but the work polished 1 x 1 cm wafer samples, not finished chips. The brief also left out that Raman checks found a small density of stacking faults introduced by polishing, and that the titanium-alloy gain was in an acidic slurry. Fix applied: "chips" changed to "wafers", and both caveats added to the brief.
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