Ultra-shallow Junction Formation Using Plasma Doping and Excimer Laser Annealing for Nano-technology CMOS Applications

摘要

A plasma-doping (PLAD) process utilizing a PH3 plasma is presented to fabricate a n±/p ultra-shallow junction at room temperature. When PLAD is completed, an excimer laser annealing (ELA)process is performed using an ArF (193 nm) excimer laser with pre-annealing. In our case, the pre-annealing is conducted for 5 min at 500 °C in a thermal furnace. The energy density of the excimerlaser used for the ELA process ranged from 400 to 500 mJ/cm2. Transmission electron microscope(TEM) and double-crystal X-ray diffraction (DXRD) measurements were employed to investigatedefects on the plasma-doped samples. Some point defects were found in the DXRD analysis whileTEM images reveal no crystalline defects. The result of a secondary ion mass spectrometry (SIMS)analysis on the formed shallow n±/p junction revealed that the junction depth was thinner than 40nm. We found that the drive-in process of phosphorous occurred only when the energy density ofthe laser was larger than 460 mJ/cm2, and an increased laser energy density resulted in a decreasedsheet resistance. With an energy density of 460 mJ/cm2, a junction depth of 30 nm and a sheetresistance of 151.6 Q/q were obtained. The leakage current for the fabricated n+/p junction wasindirectly investigated by measuring the I-V characteristics of the diode fabricated using PLAD,followed by the ELA processes.