A highly manufacturable deep trench based DRAM cell layout with a planar array device in a 70nm technology

For the first time, a new DRAM cell layout as the key enabler for future DRAM shrink generations based on deep trench (DT) technologies with a planar array device is presented. The work describes the full integration scheme in 70nm technology and the major technology features of the 'checkerboard (CKB)' layout. The new layout is beneficial for lithography and high aspect ratio etch processes. In addition, the high degree of symmetry enables easily the integration of a self aligned trench bottling process on a [100] rotated substrate with an outstanding utilization of area for the capacitor. Further capacitance enhancement up to 50% is achieved for the first time in a trench process by introduction of hemispherical silicon grains (HSG) with high k dielectric material (Al₂O₃). Additionally, a new self aligned trench-cell connection (single sided buried strap) technique with a novel isolation trench (IT) pre fill process will be presented in the paper.