Zhiming YU, Dept. of MSE3.2.1.Evaporation SputteringIon platingPHYSICAL VAPOR DEPOSITIONDate1Zhiming YU, Dept. of MSEPHYSICAL VAPOR DEPOSITION lSolid and molten sourceslPhysical mechanism by which source atoms enter the gas phaselLower pressure environment through which the gaseous species are transportedlGeneral absence of chemical reaction in gas phase and at the substrate surfaceThe objective of physical vapor deposition (PVD) processes is to controllably transfer atoms from a source to substrate where film formation and growth proceed atomisitcally. Some factors that distinguish PVD from CVD are: Date2Zhiming YU, Dept. of MSEEVAPORATION v Types of evaporationv Fundament of evaporationv Alloy evaporationv Compound evaporationv Evaporation geometryDate3Zhiming YU, Dept. of MSEE EVAPORATIONVAPORATIONSchematic outline of an evaporation systemSubstrate holderSubstrateVaporEvaporation sourceVacuum chamberSubstrate heatingPumpRotatable shutterVacuumeter +Gas inletDate4Zhiming YU, Dept. of MSETwo source evaporationABABA + BSUBSTRATE HOLDERE EVAPORATIONVAPORATIONDate5Zhiming YU, Dept. of MSEReactive evaporationSubstrateVaporPUMPReactive gas inletE EVAPORATIONVAPORATIONDate6Zhiming YU, Dept. of MSEReactive gas inletPUMPVaporSubstrateElectrode +BiasPLASMAReactive evaporationE EVAPORATIONVAPORATIONDate7Zhiming YU, Dept. of MSEReactive gas inletAnodeVACUUM PUMPCathodeMagnetic coilsReactive evaporationPLASMAE EVAPORATIONVAPORATIONSubstrateDate8Zhiming YU, Dept. of MSEHertz-Knudsen equation. Evaporation Rate (Fe)Coefficient of evaporation (01)Equilibrium pressureHydrostatic pressureGas general constantTemperature Atomic weight(molecules/cm2s)Hertz, 1882, observed the evaporation rates of mercury were: E EVAPORATIONVAPORATIONDate9Zhiming YU, Dept. of MSEwhen a = 1, Ph = 0, an expression for the maximum value of Fe is (1)M. Ohring, The Materials Science of Thin Films, (Academic Press, Inc., Boston, 2002).Fm (g/cm2s)(2)1.9771018E EVAPORATIONVAPORATIONFe (molecules/cm2s)= (M/NA)Fe(molecules/cm2s) = 3.5131022 Pe(torr)/(MT)= 5.8310-2 Pe(torr)(M/T)Dimension analysis3.282105Date10Zhiming YU, Dept. of MSEVapor pressure of the elementsPV = nRT(3)lgP(Pa) = 15993/T + 14.533 0.999lgT 3.52x10-6TFor real liquid Al, DH is function of temperature, it therefore is found:Clapeyron EquationE EVAPORATIONVAPORATIONDate11Zhiming YU, Dept. of MSEFig. 1 Vapor pressure of elementsl The temperature at Pe = 1 Pa is defined as evaporation temperature (Te)l Evaporation (Te Tm) l Sublimation (Te CaO CdOs8248769351002108211561276Cd, OCoO20781368147615701683182419722138Co, OFeO16931413152116441774191420702239Fe, OGeOs887(GeO)n, n = 1, 2, 3MgO30981600171418411968212823302535Mg, O MgOMnO21481384150216221758190120562223Mn, OMoO21368145515501654176218792004MoO3, MoO2, (MoO3)3 MoO310737627998388789199641038(MoO3)n NiO23631300140015101629175818982046Ni, O NiO PbO1159773822878942101811061217(PbO)n, n = 1, 2, 3, 4 PuO226631722184519912133225824472622PuO2 PuOTable 1, Pe, Tm, and vapor component of oxides Date17Zhiming YU, Dept. of MSECompoundM.P. (K)Temperature (K) for various P (torr)Vapor contents106 105104103102101100 Sb2O3929570603640682730785850Sb4O6 SeO2s311328348371397428462SeO2 SiO19751201129314011529SiO SiO2199512731473149516532103SiO, O SiO2 SnO1353d7788579551077(SnO2)n, n = 2, 1, 4, 3 SrO27331600168717901879200021232247Sr, O SrOTeO2668d71675980786292510041103TeO2, TeO, Te2O2, Te2O4ThO236431800191920532203237725822825Th2O, OTiO22931618172818451968211823012489TiOTiO221331800191920532203237725822825TiO2, TiO, O2UO231031754188420202165233325352786UO, UO2, UO3VO20631663179219282075223924102594VO2, VO, V WO21641173818451954207521932317WO, WO2 WO317451138126213521409144914891531(SnO3)n, n = 3, 4, 5Table 1, Pe, Tm, and vapor component of oxides (continued) Date18Zhiming YU, Dept. of MSE Evaporation of Alloys When the interaction energy between A and B atoms of a binary AB alloy melt are the same as A-A and B-B atom pairs, no preference is shown for atomic partners. PeB = XBPeB(0)APeAPeA(0)XA(4)elementsconcentrationvapor pressure of pure elementBXB PeB(0) PeB vapor pressure of element in alloysolutionideal solutionthe vapor pressure of component B, PB, in solution is reduced relative to the vapor pressure of pure B, PB(0), in proportional to its mole fraction XB.拉乌尔定律Date19Zhiming YU, Dept. of MSE In real solutionsWhere aB is the effective thermodynamic concentration of B known as the activity. The activity is related to XB through an activity coefficient gB, i.e.,PeB = aBPeB(0) aB = gBXB For a binary alloy of AB, the ratio of the evaporation rates of these elements is give by(7)(5)(6)Date20Zhiming YU, Dept. of MSEFor Example: Solution: 13.6 wt%CuEstimate approximate Al-Cu melt composition required to evaporate films containing 2 wt%Cu from a single crucible heated to 1350 K. (assuming gCu = gAl, it is known that at 1350 K PeAl(0) = 1x10-3 torr, and PeCu(0) = 2x10-4 torr)D