CMOSFET characteristics induced by moisture diffusion from inter-layer dielectric in 0.23 um DRAM technology with shallow trench isolation

In this paper, we intensively investigate CMOSFET characteristics induced by moisture diffusion from the ILD layer in 0.23 um DRAM with STI and COB (Capacitor Over Bit-line) structure. The representative phenomena are the anomalous short channel hump effect of the nMOSFET and the degradation of the short channel margin for CMOSFET. From our extensive experimental results, we obviously found that the origin of the short channel humps was due to the boron segregation at the Si/SiO ₂ interface of the STI edge region by oxygen components in the moisture diffused from the ILD film combined with the capping SiN film, and short channel margin degradation due to the oxidation enhanced diffusion of boron. In order to explain the anomalous hump phenomena we propose a new quantitative hump model, and suggest the hump suppression method using the barrier SiN film before ILD. Additionally, we perform the evaluation of hot carrier lifetime for each sample