Phosphorous Diffusion in N₂⁺-Implanted Germanium during Flash Lamp Annealing: Influence of Nitrogen on Ge Substrate Damage and Capping Layer Engineering

Abstract

In this work we present a systematic study on post-implantation phosphorous diffusion control in Ge by co-implanted nitrogen in combination with various surface capping layers (Al2O3, SiO2 and Si3N4). Phosphorous has been implanted at low energy (11 keV) and high dose (1015 cm−2) in p-Ge (100) already implanted or not with low energy (10 keV−5 × 1014 cm−2) N2+. Flash Lamp Annealing (FLA) at 800–850°C for 20 ms in inert ambient has been used as post-implantation annealing scheme. In the absence of nitrogen, significant substrate damage and capping layer deterioration prevents a reliable comparison among the three capping materials. The presence of nitrogen in the Ge substrate, effectively suppresses the damage observed after the FLA. In this case, P diffusion is additionally retarded in the presence of Al2O3 as compared to SiO2 and Si3N4. The experimental results constitute a direct evidence of the action of the three capping layers as sinks for Ge vacancies with different interface recombination velocities. On the contrary, the nitrogen diffusion data suggest that interface recombination velocities of Ge interstitials are almost independent of the capping layer choice.

(Invited) Issues with n-type Dopants in Germanium

“…At 800 o C, and in the case of Al 2 O 3 CL, shallow circular craters (of not completely identified origin) have been revealed (20). Si 3 N 4 has been proved extremely unstable, since it has been exfoliated at 800-850 o C even in the presence of N in the substrate (20).…”

“…Based mainly on Si experience and the demonstration of Ref. (16), a series of experiments dedicated to P diffusion suppression by nitrogen co-implantation have been performed during the last years (17,18,20). Representative results as a function of the post-implantation annealing scheme are shown in Figure 3.…”

“…3(a)]. Nitrogen has been also extremely beneficial in suppressing the formation of substrate defects observed in single P-implanted Ge after (17,18,20). (20).…”

“…Nitrogen has been also extremely beneficial in suppressing the formation of substrate defects observed in single P-implanted Ge after (17,18,20). (20). At 800 o C, and in the case of Al 2 O 3 CL, shallow circular craters (of not completely identified origin) have been revealed (20).…”