lon Implantation Beam of energetic dopant ions is fired into surface of wafer Energies are 5-200 keV This leads to implantation(burial) of the ions into the substrate What happens at the substrate Tons can: bounce off absorb sputter atoms(10ev -10 kev) implant into surface(5 kev -200 kev) and do tremendous damage 3.155J/6.152J.2003
Ion Implantation Beam of energetic dopant ions is fired into surface of wafer. Energies are 5 - 200 keV. This leads to implantation (burial) of the ions into the substrate. What happens at the substrate? Ions can: bounce off absorb sputter atoms (10 eV - 10 keV) implant into surface (5 keV - 200 keV)… and do tremendous damage 3.155J/6.152J, 2003
lon Implantaton Eq山mnt Ions generated in a source(from feed gas, e.g. BF3, ASH3, PH3.or heated solid source, then ionized in arc chamber by electrons from hot filament select desired species by g/m, using a magnet, accelerated by an e-field and focused using electrostatic lenses and impact substrate a bend removes neutrals )in raster pattern Resolving Aperature Focus Analyzing Magnet 0-200ke Neutral Trap X &Y scan Plates Wafer Neutral Beam 0-30keV Ion S Faraday Cup 3.155J/6.152J,2003
Ion Implantation Equipment Ions generated in a source (from feed gas, e.g. BF3, AsH3, PH3 ... or heated solid source, then ionized in arc chamber by electrons from hot filament) select desired species by q/m, using a magnet, accelerated by an E-field and focused using electrostatic lenses and impact substrate (a bend removes neutrals) in raster pattern. 3.155J/6.152J, 2003 7
What happens to lons Inside the matera? lons lose energy, dE/dx, interacting elastically with nuclei and inelastically with electrons E)+SE d x S(E)is Stopping power(eVcm lon range in target de r= dx= N S,(E)+SE) What can we say about nuclear and electronIc stoppIng 3.155J/6.152J.2003
What happens to ions inside the material? Ions lose energy, dE/dx, interacting elastically with nuclei and inelastically with electrons dE = -N S [ n (E ) + S (E)] dx e S (E) is Stopping power (eVcm2) i R 0 dE Ion range in target: R = Ú dx = 1 E Ú N 0 0 S n e (E) + S (E ) What can we say about nuclear and electronic stopping… 3.155J/6.152J, 2003 8
Nuclear stopping power: Coulomb scattering(assumed elastic Incident ion interacts with nucleus of stationary ion b= impact parameter 1.0 0.8 dE/E 04 2 0.0 2468 Energy lost by incoming ion(microscopic) Mo/M △E=E1{1- cos esin+ cos p sin e The angles depend on masses and on b 4M,M, △E=E Max energy loss is when b=0, 0=0 (M,+M 3.155J/6.152J.2003
Nuclear stopping power: Coulomb scattering (assumed elastic) Incident ion interacts with b q f b E1, M1 M2 Energy lost by incoming ion (microscopic) DE = E1 1 - sin2 f cosq sinf + cosf sinq Ï Ì Ó ¸ ˝ ˛ 0 2 4 6 8 10 M2/M1 1.0 0.8 dE/E 0.4 0.2 0.0 nucleus of stationary ion = impact parameter The angles depend on masses and on b. Max. energy loss is when b = 0, f = 0: 4 M1M2 DE = E1 (M1 + M2 )2 3.155J/6.152J, 2003 9
Nuclear stopping power: Coulomb scattering(assumed elastic At 100 kev an ion of 15 amu has velocit ≈106m/s! E. M This is 1000 times faster than speed of sound in solids So ion is far past nucleus before nucleus can displace in response to Coulomb force So nuclear scattering is not strong at high ion velocity There are also only significant inelastic collisions when ion slows down that transfer energy 3.155J/6.152J.2003
q f b E1, M1 M2 q f b E1, M1 M2 F µ Q1Q2 r 2 Nuclear stopping power: Coulomb scattering (assumed elastic) q f b E1, M1 M2 So nuclear scattering At 100 keV an ion of 15 amu has velocity , vion ≈ 106 m/s! This is 1000 times faster than speed of sound in solids… So ion is far past nucleus before nucleus can displace in response to Coulomb force is not strong at high ion velocity; There are also only significant inelastic collisions when ion slows down. that transfer energy… 3.155J/6.152J, 2003 10