Application of HSQ (hydrogen silsesquioxane) based SOG to pre-metal dielectric planarization in STC (stacked capacitor) DRAM

We investigated a new planarization process by employing a flowable HSQ (hydrogen silsesquioxane) based inorganic SOG (spin-on-glass) for pre-metal dielectric material, in order to develop a simple planarization process with low thermal budget and good planarity in STC (stacked capacitor) DRAM devices. We implemented this process in 256 Mb DRAM devices, and achieved lower TaO leakage current and better Al-reflow characteristics as well as better planarization performance than those of conventional BPSG process. Degradation of device characteristics such as Vth change or hot-carrier hardness were not observed.