Abstract: In an exemplary method, a first dielectric layer is formed on a substrate. A second dielectric layer is formed on the first dielectric layer. The second dielectric layer is a carbon rich film and different from the first dielectric layer. A trench is formed through the first and second dielectric layers. A conductive line is formed in the trench. A third dielectric layer is formed on the second dielectric layer and conductive line. The material of the third dielectric layer is different from the second dielectric layer. A via opening is formed through the third dielectric layer and stops at the second dielectric layer with a portion of the conductive line exposed to the via opening. At the bottom of the via opening, a recess is formed in the second dielectric layer adjacent to the conductive line. The via opening and recess are filled with a conductive material contacting the conductive line.

Abstract: In an exemplary method, a first dielectric layer is formed on a substrate. A second dielectric layer is formed on the first dielectric layer. The second dielectric layer is a carbon rich film and different from the first dielectric layer. A trench is formed through the first and second dielectric layers. A conductive line is formed in the trench. A third dielectric layer is formed on the second dielectric layer and conductive line. The material of the third dielectric layer is different from the second dielectric layer. A via opening is formed through the third dielectric layer and stops at the second dielectric layer with a portion of the conductive line exposed to the via opening. At the bottom of the via opening, a recess is formed in the second dielectric layer adjacent to the conductive line. The via opening and recess are filled with a conductive material contacting the conductive line.