Physics and Applications of Plasma-Based Ion Implantation Jason Olejarz May 4, 2009

Basics of Conventional Ion Implantation Process for altering material surface properties Process for altering material surface properties Beam-line technique Beam-line technique Applications Applications [1]

Physics of Plasma-Based Ion Implantation Material is immersed in a plasma Material is immersed in a plasma Material is biased with a high negative voltage Material is biased with a high negative voltage Ions accelerate toward the material and are implanted Ions accelerate toward the material and are implanted [1]

Parameters Incident ion energy (~ keV) Incident ion energy (~ keV) Duration of pulse (~ 10 us) Duration of pulse (~ 10 us) Frequency of pulses (~ 10 Hz-1 kHz) Frequency of pulses (~ 10 Hz-1 kHz) Ion implantation depth (~ 10 nm-1 um) Ion implantation depth (~ 10 nm-1 um)

Sheath Dynamics 3 timescales 3 timescales Electrons accelerate away from the substrate Electrons accelerate away from the substrate ~ 100 ps ~ 100 ps Ions accelerate toward the substrate Ions accelerate toward the substrate ~ 100 ns ~ 100 ns Steady state is reached Steady state is reached Tens of inverse ion plasma frequencies Tens of inverse ion plasma frequencies

Sheath Dynamics [2]

Sheath Thickness Child-Langmuir law Child-Langmuir law

Sheath Thickness [1]

Plasma Properties Influence of density on sheath formation Influence of density on sheath formation Influence of pressure on ion energy distribution Influence of pressure on ion energy distribution

Ion-Surface Interaction Complicated process Complicated process Physical and chemical effects Physical and chemical effects Described to a good approximation by studying a single incident ion Described to a good approximation by studying a single incident ion Electronic stopping Electronic stopping Nuclear stopping Nuclear stopping

Ion-Surface Interaction [1]

Collisional Defects and Surface Erosion Frenkel defects Frenkel defects Sputtering Sputtering

Applications in Metallurgy and Tribology Uses Uses Strengthening metals Strengthening metals Reducing friction and wear Reducing friction and wear Advantages Advantages Uniform implantation of irregular shapes Uniform implantation of irregular shapes Quick implantation over large areas Quick implantation over large areas Disadvantages Disadvantages Lack of controllability of incident ion parameters Lack of controllability of incident ion parameters

Applications in Semiconductor Technology Uses Uses Plasma doping Plasma doping Doping of devices of decreasing size Doping of devices of decreasing size Advantages Advantages Low incident ion energy Low incident ion energy Disadvantages Disadvantages Lack of controllability of incident ion parameters Lack of controllability of incident ion parameters

Current Research Manufacturing of biomaterials Manufacturing of biomaterials Modification of polymer surfaces Modification of polymer surfaces Cost Cost Radiation Radiation Secondary electron emission Secondary electron emission

References 1. Plasma-Based Ion Implantation; Wolfhard Moller and Subroto Mukherjee; Current Science, Vol. 83, No. 3, 10 August Plasma-Based Ion Implantation and Deposition: A Review of Physics, Technology, and Applications; Jacques Pelletier and Andre Anders; IEEE Transactions on Plasma Science, Vol. 33, No. 6, December Plasma-Based Ion Implantation and Electron-Bombardment for Large-Scale Surface Modification of Materials; J. N. Matossian, R. Wei, J. D. Williams; Surface and Coatings Technology 96 (1997) Ultra-Shallow Junctions Produced by Plasma Doping and Flash Lamp Annealing; Wolfgang Skorupa, Rossen A. Yankov, Wolfgang Anwand, Matthias Voelskow, Thoralf Gebel, Daniel F. Downey, Edwin A. Arevalo; Materials Science and Engineering B (2004)