Nano-Scale Depth Profiles of Electrical Properties of Phosphorus Doped Silicon for Ultra-Shallow Junction Evaluation

Electrical properties and microstructure of phosphorus (P) implanted p-type Si substrates were evaluated by four-point probe (4PP), Differential Hall Effect Metrology (DHEM), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) techniques, after RTA 750-950°C and CO2 laser 120-140W annealing. When RTA temperature was increased, defect concentration at a-Si/c-Si interface gradually disappeared. For CO2 laser annealing, defects were found to aggregate at the end of range (EOR) region. Sheet resistance (Rs) values decreased significantly with increasing RTA temperature due to defects disappearing at EOR. Rs did not change appreciably for the CO2 laser annealing case. The dopant activation ratio was less than 50% below RTA temperature of 850 °C, and it increased to 70% at 950 °C. For CO2 laser annealing, the activation ratio could reach to over 80% regardless of the laser power. The highest active concentration and the lowest resistivity or mobility were found to be within the top 20 nm region of the surface. Although RTA annealing conditions influenced dopant diffusion and the resulting electrical property depth profiles significantly, depth profiles did not change much with changes in CO2 laser power level. It was demonstrated that DHEM data in conjunction with SIMS and TEM data can be successfully employed to evaluate, in detail, the electrical properties of ultra-shallow junctions for metal oxide semiconductor field effect transistor (MOSFET) applications.