Patterning three dimensional structures

Abstract

The invention is directed to a method of forming a three dimensional circuit including introducing a three dimensional circuit over a substrate. In one embodiment, the three dimensional circuit includes a circuit structure in a stacked configuration between a first signal line and a second signal line, where the two signal lines comprise similar materials. The method includes selectively patterning the second signal line material and the circuit without patterning the first signal line. One way the second signal line is patterned without patterning the first signal line is by modifying the etch chemistry. A second way the second signal line is patterned without patterning the first signal line is by including an etch stop between the first signal line and the second signal line. The invention is also directed at targeting a desired edge angle of a stacked circuit structure. In terms of patterning techniques, a desired edge angle is targeted by modifying, for example, the etch chemistry from one that is generally anisotropic to one that has a horizontal component to achieve an edge angle that is slightly re-entrant (i.e., having negative slope).