PHYSICAL VAPOR DEPOSITION (PVD PVD II: Evaporation ◆ We saw oⅴD Gas phase reactants: po l mTorr to l atm Good step coverage, T> 350 K ◆ We saw sputtering Noble (+ reactive gas)p 10 mTorr; ionized particles Industrial process high rate reasonable step coverage Extensively used in electrical, optical, magnetic devices Now see evaporation: Source material heated, Peg, vap. 10- Torr, Pg 10- Torr Generally no chemical reaction(except in "reactive depos'n n=10s of meters. Knudsen number n >>1 Poor step coverage, alloy fractionation: 4 pvapor Historical(optical, electrical Campbell, Ch 12 is more extensive than Plummer on evaporation 6.152J3.155J6.152J/3.155J 1 PHYSICAL VAPOR DEPOSITION (PVD) PVD II: Evaporation We saw CVD Gas phase reactants: pg ≈ 1 mTorr to 1 atm. Good step coverage, T > 350 K ‹ We saw sputtering Noble (+ reactive gas) p ≈ 10 mTorr; ionized particles Industrial process, high rate, reasonable step coverage Extensively used in electrical, optical, magnetic devices. ‹ Now see evaporation: Source material heated, peq.vap. =~ 10-3 Torr, pg < 10-6 Torr Generally no chemical reaction (except in “reactive depos’n), λ = 10’s of meters, Knudsen number NK >> 1 Poor step coverage, alloy fractionation: ∆ pvapor Historical (optical, electrical) ‹ Campbell, Ch. 12 is more extensive than Plummer on evaporation