Millisecond flash annealing: Applications for USJ formation and optimization of device electrical characteristics

To form ultra shallow junctions (USJs) several fast annealing techniques are available with very high temperatures to activate dopants yet minimize diffusion. Flash annealing utilizes Xe-arc lamps which provide a short (2 ms) burst of intense optical energy achieving wafer surface temperatures in excess of 1300 °C. It is shown that this annealing technique facilitates boron activation to its solid solubility level. Reviews are given of the flash annealing parameters to show how they affect leakage currents, junction depths and dopant activation but to address poly depletion effects, flash annealing must be complemented with an RTA anneal. Several dopants for sub 90 nm devices have been characterized under various annealing conditions resulting in leakage currents comparable to spike anneal and transistors with higher current gain. High boron activation concentrations are obtained through adjustment of process conditions including modifying the processing sequence by utilizing multiple flash anneals. Certain device geometrical factors and film structures also have to be adjusted to optimally utilize the flash technology with the most important factor being minimization of defect generation with the high energy imparted onto the wafer surface. To control this energy, additional optimization of the flash technology is achievable through varying the energy pulse width and initiation of the Xe-arc lamp ignition. Data showing comparative results is presented, including how such results compare to the use of spike annealing.