Fabrication method for a semiconductor structure

摘要

The present invention provides a fabrication method for a semiconductor structure having the steps of providing a semiconductor substrate ( 1 ); providing and patterning a silicon nitride layer ( 3 ) on the semiconductor substrate ( 1 ) as topmost layer of a trench etching mask; forming a trench ( 5 ) in a first etching step by means of the trench etching mask; conformally depositing a liner layer ( 10 ) made of silicon oxide above the resulting structure, which leaves a gap (SP) reaching into the depth in the trench ( 5 ); carrying out a V plasma etching step for forming a V profile of the line layer ( 10 ) in the trench ( 5 ); wherein the liner layer ( 10 ) is pulled back to below the top side of the silicon nitride layer ( 3 ); an etching gas mixture comprises C₅F₈, O₂ and an inert gas is used in the V plasma etching step; the ratio (V) of C₅F₈/O₂ lies between 2.5 and 3.5; and the selectivity of the V plasma etching step between silicon oxide and silicon nitride is at least 10.