Ion Implantation Most modern devices using ion implanters  Implant dopants by accelerating individual atoms (ions) Ionize gas sources (single +, 2+ or 3+ ionization)  Use analyzer to selection charge/mass ratio (ie ionization)  Accelerate dopant ions to very high voltages (10-600 KeV)  beam to remove neutral ions  Raster scan target: implant all areas at specific doping thus slow  – Just integrate charge to get dopant level for wafer  Ion Implanter Implanter end station Ion Implantation Advantages Precise control of doping levels in both position and depth  Measure dopants dose in atom/cm2  Much less dopant spreading (sideways & down)  Regular diffusion spreading is several microns implant needed for small structures devices <2  – μm Disadvantages Implanters expensive $1 $10 million  To get depth may need high voltage/high current  double or triple ionized (which gives lower rates) Heavy radiation damage to crystal  Dopant need to be activated to go interstitially)  Implant creates high temperature in resist & loads it with dopant  resist very hard to strip  Single wafer and raster scan thus long time to implant – Diffusion does many wafers at once, implant one at a time
Ion Implantation  Most modern devices using ion implanters Implant dopants by accelerating individual atoms (ions)  Ionize gas sources (single +, 2+ or 3+ ionization)  Use analyzer to selection charge/mass ratio (ie ionization)  Accelerate dopant ions to very high voltages (10-600 KeV)  beam to remove neutral ions  Raster scan target: implant all areas at specific doping – thus slow  Just integrate charge to get dopant level for wafer Ion Implanter Implanter end station Ion Implantation Advantages  Precise control of doping levels in both position and depth  Measure dopants dose in atom/cm2  Much less dopant spreading (sideways & down) Regular diffusion spreading is several microns  implant needed for small structures – devices <2 μm Disadvantages  Implanters expensive $1 $10 million  To get depth may need high voltage/high current double or triple ionized (which gives lower rates)  Heavy radiation damage to crystal  Dopant need to be activated to go interstitially)  Implant creates high temperature in resist & loads it with dopant  resist very hard to strip Single wafer and raster scan – thus long time to implant Diffusion does many wafers at once, implant one at a time
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