DEGRADATION OF METAL-OXIDE SEMICONDUCTOR CHARACTERISTICS DUE TO BOROPHOSPHOSILICATE-GLASS REFLOW IN O2-CONTAINING AMBIENT

This brief reports the effects of post-gate processing in an O2-contai ning ambient (less-than-or-equal-to 40% in N2), such as the source/dra in annealing, and the borophosphosilicate-glass (BPSG) densification a nd reflow, on the metal-oxide-semiconductor (MOS) device characteristi cs. Compared to devices processed in a pure N2. ambient during the BPS G reflow (and with a low O2 concentration for the source/drain anneal and the BPSG densification), it is found that devices processed in the O2-containing ambient (approximately 40% O2 in N2 during reflow) show a significantly degraded low-field breakdown characteristics (e.g., 1 0(2)-10(4) x higher gate leakage current) when electron injection take s place at the polycrystalline silicon (poly-Si)/SiO2 interface. Resul ts suggest that the BPSG reflow in an O2-containing ambient might indu ce some positive charges near the poly-Si/SiO2 interface and results i n a lowered tunneling barrier and/or an enhanced injecting electric fi eld. However, no significant difference was observed in device reliabi lity under F-N injection for devices processed in ambients with or wit hout O2.