Reflow of PSG Layers by Halogen Lamp Short Duration Heating Technique

Abstract

Reflow of 7 mol% P₂O₅ phosphosilicate glass (PSG) deposited on steep polysilicon steps was studied by halogen lamp short duration heating at temperatures ranging from 1050 to 1150°C. Reflow occurs after 60 s with 1050°C heating. Heating times required for reflow decrease rapidly with increased temperature and reach 40 and 15 s at 1100 and 1150°C, respectively. When heating is performed over a certain period, for instance, 80 s at 1100°C, reflow becomes excessive, leading to a breakdown voltage deterioration between Si gate electrodes and Al interconnections as well as a deeper source/drain junction depth. Optimum lamp heating times for adequately tapered contours were 40–80 s at 1100°C and 15–40 s at 1150°C.