Comparative study of PE-BPSG and HDP-PSG as PMD for 0.25 μm memory device

A pre-metal dielectric (PMD) process of phosphosilicate glass (PSG) was developed by using high-density plasma (HDP) CVD. The HDP-PSG process was successfully integrated to a self-aligned contact (SAC) structure, with AR of 8:1 and a bottom contact size of 0.25 /spl mu/m, in the diffusion contact level. No post-deposition reflow was required to complete gap fill. SRAM device characteristics showed that breakdown voltage and transistor threshold voltage of devices with HDP-PSG are comparable with those with PE-BPSG. The yield results showed that HDP-PSG yielded 5 to 10% better than PE-BPSG.