Process for a nail shaped landing pad plug

摘要

The invention has two embodiments for forming a contact plug having large nail shaped landing pad. The large pad areas increase the overlay tolerances. The first embodiment comprises forming first 20 and second 24 insulating layers over a semiconductor structure. A first photoresist layer 28 with a first opening is formed over the second insulating layer 24. The second insulating layer 24 is isotropically etched using an etchant with a high selectivity thereby forming a disk shaped opening 26A. The disk shaped opening is used to define the large nail shaped landing pad. The first insulating layer 20 is etched using a dry etch thereby forming a nail shaped contact opening 26. The opening is filled with polysilicon to form the nail shaped conductive plug 36. The second embodiment begins by forming a first insulating layer 40 over a semiconductor structure. A first photoresist layer 44 with a first opening is formed over the first insulating layer 24. The first insulating layer is isotropically etched to form a half spherical hole. The first insulating layer 40 is then anisotropically etched; and forming a rounded nail shaped contact hole 50. The hole 50 is filled thereby forming the rounded nail shaped conductive plug 58.