Deposition method comparison
How CVD, PVD, ALD, and epitaxy differ, conceptually. Read it as a map of trade-offs — each is the right tool for different layers, and there is no universal ranking.
| Dimension | CVD | PVD | ALD | Epitaxy |
|---|---|---|---|---|
| Mechanism | Precursor gases react at the wafer surface | Atoms physically transported from a solid source in vacuum | Alternating self-limiting surface reactions, one layer per cycle | Crystalline growth aligned to the substrate lattice |
| Conformality | Generally good | Limited (largely line-of-sight) | Excellent | Follows the surface/crystal |
| Thickness control | Good | Moderate | Atomic, set by cycle count | Good, crystal-limited |
| Typical use cases | Many dielectric, semiconductor, and metal films | Metal layers, seed and adhesion layers | Ultrathin dielectrics, liners, and barriers | Device-quality single-crystal layers |
| Limitations | Needs suitable precursors; byproducts and temperature | Poor conformality on high-aspect-ratio features | Slow throughput | Demanding conditions; constrained by the underlying lattice |
No universal ranking
No method is universally best. Each layer is matched to the method whose blend of conformality, thickness control, throughput, temperature, and material fit suits the job — fabs use all of them, often on the same chip.