what is pvd vs cvd vs ald

Three deposition families, one sentence each — say this and you've shown the core. 1) PVD (physical) — atoms knocked off a solid TARGET (sputtering) or evaporated land on the wafer; good for thin, low-temperature metal films. 2) CVD (chemical) — gases REACT on the heated wafer surface to form the film; better step coverage, can fill features. 3) ALD (atomic layer) — precursor A, purge, precursor B, purge, one atomic layer at a time; atomic precision and perfect conformality on deep, high-aspect-ratio features — but slow. The decision: PVD for thin/low-temp metals, CVD for conformal/fill, ALD when you need atomic control on deep features. The one-line frame: 'PVD for speed and simple films, CVD for conformality, ALD for atomic precision on the hard-to-reach geometry.' Learn the WHY of each — a GPS engineer must know when to switch and each one's failure signature.