Interconnect features with sharp corners and method forming same

A method comprising:

• forming a dielectric layer;
• etching the dielectric layer to form openings;
• and
• forming a plurality of conductive features, with at least upper portions of the conductive features filling the openings in the dielectric layer, wherein the plurality of conductive features have lengthwise directions aligned to a same straight line, wherein the plurality of conductive features comprise a first end feature, a second end feature, and at least one middle conductive feature between, and physically separated from, the first end feature and the second end feature, and the first end feature comprising:
• a first end facing away from the second end feature, wherein the first end have first corners;
• and
• a second end facing toward the second end feature, wherein the second end have second corners sharper than the first corners.

A method comprising:

• depositing a dielectric layer;
• depositing a plurality of mandrel strips over the dielectric layer;
• forming a plurality of spacers on sidewalls of the plurality of mandrel strips to form a plurality of mask groups, wherein each of the plurality of mandrel strips and two of the plurality of spacers form a mask group in the plurality of mask groups;
• forming a mask strip connecting two neighboring mask groups in the plurality of mask groups, wherein the forming the mask strip comprises:
• depositing a template layer over the plurality of mask groups, wherein the template layer has a top surface higher than top surfaces of the plurality of mask groups;
• forming an opening in the template layer, wherein at least two of the plurality of mask groups are revealed through the opening;
• filling the opening to form the mask strip;
• and
• removing the template layer;
• using the plurality of mask groups and the mask strip collectively as an etching mask to etch the dielectric layer, and to form trenches in the dielectric layer;
• and
• filling a conductive material into the trenches to form a plurality of conductive features.