Copper diffusivity in boron-doped silicon wafer measured by dynamic secondary ion mass spectrometry

The effective copper diffusivity (D_eff) in boron-doped silicon wafer was measured using a Dynamic Secondary Ion Mass Spectrometry (D-SIMS) that was incorporated with an out-drift technique. By this technique, positive interstitial copper ions (Cu_I⁺) migrated to the surface region when a continuous charge of electrons showered on the oxidized silicon wafer, which was also bombarded by primary O₂⁺ ions. The Cu_I⁺ ions at the surface region diffused back to the bulk when the electron showering stopped. The D-SIMS recorded the real-time distribution of Cu_I⁺ ions, generating depth profiles for in-diffusion of copper for silicon-wafer samples with different boron concentrations. These were curve-fitted using the standard diffusion expressions to obtain different D_eff values, and compared with other measurement techniques.