Every crystal grown by chemical vapor deposition is the product of heat doing two jobs at once. The first is chemistry: cracking the precursor molecules apart so their atoms are free to react. The second is kinetics: giving those atoms enough surface mobility to find and settle into their proper lattice sites. Conventional MOCVD does both with temperature alone, which is why it needs roughly 750 °C — and why, for decades, you could not grow a fresh crystal on top of a finished chip. Anything above about 400 °C destroys the transistors and copper interconnect already on the wafer.
Let plasma do the chemistry
Our recipe takes the first job away from heat entirely. An inductively-coupled plasma cracks the precursors electronically rather than thermally, collapsing the reaction's activation barrier so growth proceeds at temperatures a finished CMOS wafer can survive. That single substitution is what makes monolithic 3D thinkable: the growth step no longer competes with the silicon underneath it.
Let photons fix the lattice
But moving the chemistry off heat exposes the second job. Atoms deposited cold do not always land where the lattice wants them, and historically low-temperature growth has meant defective, leaky film. This is where the photons earn their place in the name. In-situ ultraviolet irradiation during growth couples selectively into defect sites, handing misplaced atoms exactly the energy they need to re-bond correctly — while the film is still forming. Defect repair stops being a separate high-temperature anneal afterward and becomes a continuous part of growth itself.
Plasma for the chemistry, photons for the lattice, heat kept below the ceiling that would damage the chip beneath: that division of labor is the entire idea. The combination produced the result we brought to IEDM this December — continuous MoS₂ monolayers across full 200 mm wafers, grown cold enough to sit directly on finished silicon.