6.152J3.155J Oxygen impurities in Si: Observed to follow Arrhenius Cm=2×102cxp[-1.03eV/n7 Want about 10-30 ppm(7 x 1017/cm) which occurs at T 1250C Anneal - denuded zone deeper than deepest feature Oxygen E. Vacancy Interstitial Activation energies(ev): 1.03 1.12 2.6 4.5 Dopants, impurities(substitutional, interstitial) 6.12J/3.155J Microelectronic processing At rt number of intrinsic carriers n=(nnh)12=eXp(-E/2kB7)=>n=2X1010cm3 5x1022 (5x102/cm3) ,A 5x1016/ Very small doping concentration =>large increase in carrier concentration What do dopants do? nI E6.152J/3.155J 6 11 Nov.26 , 2003 6.12J / 3.155J Microelectronic processing Oxygen impurities in Si: Observed to follow Arrhenius Coxy = 2 ¥1022 exp -1.03eV /k [ ] BT Want about 10 - 30 ppm (7 x 1017/cm3)… which occurs at T § 12500C Activation energies (eV): 1.03 1.12 2.6 4.5 Oxygen Eg Vacancy Interstitial 40 Coxy (ppm) 20 0 Agglomeration => warpage, stress, dislocations No agglomeration (many isolated O2- ions) Optimal 1414 T (0C) 1200 High Coxy 3 hr anneal => 15 ppm Anneal => denuded zone deeper than deepest feature Agglomeration Oxygen § 25 microns 12 Nov.26 , 2003 6.12J / 3.155J Microelectronic processing Dopants, impurities (substitutional, interstitial) At RT number of intrinsic carriers: ni = (nenh)1/2 = n0exp(-Eg/2kBT) => ni = 2 x 1010/cm3 5 x 1022 J =sE = ne < v > m = v E = s ne = et m * s = ne2 t m * What do dopants do? Very small doping concentration => large increase in carrier concentration So doping at 1 ppm => 10-6 = nD,A/(5 x 1022/cm3 ) nD,A = 5 x 1016/cm3