Ion Implantation and Synthesis of Materials - Studium

74 6 Ion Range and Range Distributionthat cause defections in the arsenic’s flight path. Figure 6.8 shows the ion distributionobtained from the statistics of 20 × 10 3 ion histories. Note that the MonteCarlo calculation gives a projected range of 398 Å and a longitudinal range stragglingof 139 Å in good agreement with the analytical results presented inFig. 6.5. Note that the y-axis is in units of atoms cm −3 ions −1 cm −2 , which is atomicdensity normalized by dose. For example, the number of As ions in the peak of thedistribution is roughly 28 × 10 4 atoms cm −3 ions −1 cm −2 which, for a dose of1 × 10 14 As ions cm −2 , converts to(28 × 10 4 ) × (1 × 10 14 ) = 2.8 × 10 19 As cm −3 .Using (6.8) and N Si = 5 × 10 22 atoms cm −3 , the peak concentration of As in Si for adose of 1 × 10 14 As ions cm −2 is 0.06 atomic%.50 keV As in Si2824Ion RangeStraggle= 398 A= 139 A3 2(Atoms/cm ) ⁄ (Ions/cm )52016128400100 200 300 400 500 600 700 800Target Depth (Angstroms)Fig. 6.8. The ion implantation distribution for 50 keV As implanted into Si calculated withthe SRIM Monte Carlo simulation. Units of the y-axis are As atomic density normalized byAs ion doseReferencesBiersack, J.P.: Calculation of projected ranges in analytical solutions and a simple generalalgorithm. Nucl. Instrum. Meth. 182/183, 199 (1981)Eckstein, W.: Computer Simulation of Ion–Solid Interactions. Springer, Berlin HeidelbergNew York (1991)