BPSG, SA-CVD liner/P-HDP gap fill

Various issues arise in attempting to satisfy the ever increasing demands for miniaturization, particularly in fabricating non-volatile semiconductor devices, such as flash memory devices, e.g., electrically erasable programmable read only memory (EEPROM) devices. The demands for continuing miniaturization have led to the fabrication of flash memory devices comprising transistors having a gate width of about 0.18 micron and under and very closely spaced apart gate structures. In accordance with conventional practices, an oxide sidewall spacer is formed on side surfaces of the gate stack and a conformal silicon nitride layer, serving as an etch stop layer, is deposited over the gate structures including the sidewall spacers, thereby further reducing the gap between gate structures to about 0.125 micron or less. In accordance with conventional practices, a first interlayer dielectric (ILD ) is deposited over the gate structures and fills the gaps therebetween. Rapid thermal annealing is then conducted, as at a temperature of about 820° C. for about 120 seconds. Device leakage due to spacer undercutting is remedied by depositing a BPSG, SA-CVD oxide liner and flowing it into the undercut regions, followed by gap filling with a P-doped HDP oxide layer. Embodiments include depositing a BPSG, SA-CVD oxide liner containing 4 to 6 wt.% boron, at a thickness of 1,000 to 1,800 , over closely spaced apart non-volatile transistors and heating during or subsequent to deposition to flow the BPSG, SA-CVD oxide liner into the undercut regions of the sidewall spacers of the gate stacks. Gap filling is then completed by depositing the layer of P-doped HDP at a thickness of 6,000 to 10,000 .