IN Brief:
- Thermal limits are tightening for GaN RF, and data-centre accelerator packaging.
- Rice reports wafer-scale, selective diamond growth using seeded microwave plasma CVD.
- The process aims to integrate patterned diamond heat spreaders without aggressive post-etch steps.
A Rice University team has reported a selective-area diamond growth technique intended to bring patterned diamond thermal management closer to device-relevant manufacturing flows. In work published in Applied Physics Letters, the researchers describe a “bottom-up” approach that grows diamond only where needed, and they say the technique can reduce electronics operating temperatures by 23°C.
“In the world of electronics, heat is the enemy,” said Xiang Zhang, assistant research professor of materials science and nanoengineering at Rice, and a first author on the study. “A reduction of 23 C is significant — it can extend the lifespan of a device and allow it to run faster without overheating.”
Power density is climbing in RF front ends, and in the compute, networking, and power stages that sit behind AI infrastructure. Gallium nitride transistors, in particular, can deliver high switching speeds, and power handling, but thermal extraction remains a limiting factor once systems push into higher duty cycles, and smaller footprints. Diamond’s thermal conductivity makes it an obvious candidate, but its material hardness and chemical resistance complicate shaping, and integration.
Zhang described the team’s work as an alternative to conventional “top-down” patterning where diamond is deposited as a blanket layer and then etched. That approach is possible, but it is slow, and tends to drag in aggressive chemistries and process steps that can damage interfaces, or leave roughness and stress where the thermal path matters most.
Instead, the Rice researchers used microwave plasma chemical vapour deposition, combined with nucleation control, to define diamond growth areas during deposition. The method relies on seeding the target regions with nanodiamonds, which act as nucleation sites as carbon-rich gases are dissociated in the plasma and carbon atoms assemble into diamond on the prepared surface.
For finer patterns, the team used photolithography to create a stencil, then applied a nanodiamond-containing liquid so seeds remained only where growth was desired. For larger formats, they used a laminated film, laser-cut to the required geometry, followed by a peel-and-seed step that avoids harsh chemical patterning. “This approach allowed us to scale up to a full 2-inch wafer,” Zhang said.
Beyond geometry control, the researchers say seed density provides a lever over microstructure within a given pattern, influencing crystal size and structure. As a proof of concept, the study evaluated silicon and gallium nitride substrates, a pairing that points directly at mixed-material packaging, and power device stacks.
Yuji Zhao, professor of electrical and computer engineering at Rice, and a co-corresponding author on the paper, said: “This work demonstrates wafer-scale, selective diamond growth compatible with heterogeneous integration, enabling high-performance thermal management at device-relevant temperatures and layouts.”
The team has flagged interface engineering as the next technical step, with an eye on high-electron-mobility transistors and other high-power devices where thermal boundary resistance can erase much of diamond’s bulk advantage if bonding and stress are not handled cleanly.
