PELOX integrated PBL

Abstract

Polysilicon buffered LOCOS (PBL) has been widely utilized for advanced isolation applications as moderately low lateral oxide encroachment may be achieved without defect formation. Unfortunately, PBL does not exhibit sufficient field oxide recess to support aggressive device scaling without introduction of processes which are difficult to control. Recently, polysilicon encapsulated local oxidation (PELOX) has been proposed as an easily scaled isolation technique that exhibits LOCOS equivalent recess. The integration of PELOX into an existing PBL 1 Mb DRAM baseline process is described. PE-LOX integrated PBL (PIPBL) is demonstrated to enhance final field oxide recess without increasing encroachment. The improved final field oxide recess is shown to provide increased process margin as evidenced by superior probe yield.

Study of shallow trench isolation technology with a poly-Si sidewall buffer layer

“…This would lead to dislocation formation, degrading the integrity of junction and thin gate oxide. On the other hand, in the LOCOS technology, for reducing the bird's beak length without inducing the extra stress, poly-Si buffer LOCOS technology has been employed to meet the requirement [7][8][9][10][11]. During the field oxidation, the rigidity of nitride inhibits the lateral oxygen diffusion.…”

“…And, resultantly the volume expansion of grown field oxide near the bird's beak edge would pull apart the silicon lattice, creating defects in the Si substrates unless a stress-relief layer is sandwiched between nitride and pad oxide. The poly-Si, due to its soft property, is squeezable and capable of relaxing the stress [7][8][9][10][11]. As a result, poly-Si is generally used to absorb the stress.…”