Extending the capabilities of DRAM high aspect ratio trench etching

Abstract

High aspect ratio silicon trench etch is a key process to manufacture trench capacitor DRAMs. The capacitance is directly proportional to the surface of the capacitor. Shrinking to the next technology required a similar capacitance while the corresponding CDs are reduced. To ensure sufficient capacitance the aspect ratio has to be increased. The existing trench etch reactor was not capable to reach the required aspect ratio due to its limited selectivity to the oxide hard mask. Thus, new plasma reactor hardware had to be developed and evaluated. This work summarizes and compares the process performance of the new with the previously used hardware.