Near‐Surface Defect Control by Vacancy Injecting/Out‐Diffusing Rapid Thermal Annealing

Abstract

Rapid thermal annealing (RTA) can be applied to dissolve small defects such as voids or small-sized oxygen precipitates and to manipulate vacancies in a specific depth from the surface. This can be achieved at elevated temperatures around 1300 C and via NH 3 dissociation at the surface at temperatures >1150 C. In an earlier study (Araki et al., 2013), it had been demonstrated already that even under oxidizing ambient, enhanced bulk micro defects formation around 1300-1350 C can occur. The near-surface region is monitored via its homogeneity of precipitation and in-depth vacancy profiling by Pt-diffusion. Simulations of defect dissolution during RTA processes are performed up to 1290 C under different ambient. The size-dependent defect dissolution behavior is predicted and verified by measurement of the gate oxide integrity.

Simulation of Nitrogen Indiffusion and Its Impact on Silicon Wafer Strength

“…The process consists of three steps to simulate the effect on nitrogen indiffusion via prenitridation (step 1), active nitridation (step 2), and vacancy outdiffusion to create a near‐surface‐defect‐free zone. [ 12 ] In step 1, the nitridation was conducted in the beginning at low temperatures and then the temperature was raised to a level >1200 °C to let nitrogen atoms, stored in the oxynitride film, effectively diffuse into the wafer. In step 2, the temperature was deceased below 1200 °C to actively nitride the surface furthermore in a mixed atmosphere of argon/NH 3 at optimized conditions.…”

“…In step 2, the temperature was deceased below 1200 °C to actively nitride the surface furthermore in a mixed atmosphere of argon/NH 3 at optimized conditions. [ 12 ] To establish a near‐surface defect zone a third step was carried out at even lower temperatures to let excess vacancies diffuse out. This omits the formation of undesired oxide precipitates near the device region.…”

“…This omits the formation of undesired oxide precipitates near the device region. [13] Table 1 compares the measured and simulated values for the nitrogen concentration and Figure 2 shows a comparison between measured and simulated nitrogen concentrations. The optimized prefactor amounts to 4.209 Â 10 17 cm À3 , which is higher than in Equation ( 6) as found in Maeda et al [11]…”