Deep Trench Top Collar Oxide Etching for DRAM Manufacturing

In the fabrication of deep trenches (DT) used as the storage capacitors in DRAMs, precise formation of the lateral oxide isolation inside the trench $the "collar" - is one of the key process modules. The collar formation involves DT top oxide etching following furnace oxide growth. Careful optimization of the most critical oxide etch step is necessary. In this paper, the etch process parameters impacting the net collar oxide removal rate are discussed, followed by etch chamber conditioning optimization. Etch process endpoint challenges and solutions are also investigated