Method for forming aligned vias under trenches in a dual damascene process

摘要

Disclosed is a method for forming an aligned via under a trench to prevent voiding in a dual damascene process. The trench is formed in an oxide layer that is formed over a first metal layer and the first metal layer is formed over a semiconductor substrate. The method includes forming an etch stop layer over the oxide layer and forming a set of adjacent trenches in the oxide layer through a portion of the etch stop layer. The method also includes forming a resist layer at least partially over the etch stop layer. The resist layer is formed in a via pattern to expose the set of adjacent trenches through the via pattern. The method further includes etching the oxide layer under the set of adjacent trenches until the oxide layer is etched through to expose at least a portion of the first metal layer so as to form a via under each of the adjacent trenches. In this process, the etch stop layer inhibits the oxide layer underneath from being etched substantially such that each of the vias formed under the each of the adjacent trenches is substantially of a same width as and in alignment with the associated trench above.