Integrated circuit and method
A via etch to contact a capacitor with ferroelectric between electrodes together with dielectric on an insulating diffusion barrier includes two-step etch with F-based dielectric etch and Cl- and F-based barrier etch.
1. A method of forming a capacitor, comprising:
(a) forming a stack of layers over a substrate with exposed capacitor connections, said stack including a top electrode layer on a ferroelectric layer on a bottom electrode layer;
(b) forming an etch mask over said stack, said mask defining location of a capacitor;
(c) etching said stack using said mask, said etching including introducing said substrate with said stack into a plasma etcher;
(d) exciting a first plasma from a first gas;
(e) etching through said top electrode layer using ions from said first plasma;
(f) after step (e) exciting a second plasma from a second gas;
(g) etching through said ferroelectric layer using ions from said second plasma;
(h) after step (g) exciting a third plasma from a third gas; and
(i) etching through said bottom electrode layer using ions from said third plasma.
2. The method of claim 1 , wherein:
(a) said top electrode is made of a metal;
(b) said first gas includes chlorine and oxygen species, but no fluorine species;
(c) said ferroelectric is a zirconate titanate;
(d) said second gas includes chlorine, oxygen, and fluorine species;
(e) said bottom electrode is made of said metal; and
(f) said third gas is the same as said first gas.
3. The method of claim 1 , wherein:
(a) said metal is iridium; and
(b) said ferroelectric includes lead zirconate titanate (PZT).
4. The method of claim 1 , further comprising:
(a) forming a bottom diffusion barrier layer prior to forming said stack, wherein said stack is formed on said bottom diffusion barrier layer;
(b) after said step (i) of claim 1 , exciting a fourth plasma from a fourth gas; and
(c) etching through said bottom diffusion barrier layer using ions from said fourth plasma.
5. The method of claim 1 , further comprising:
(a) forming a top diffusion barrier layer on said stack;
(b) prior to said step (d) of claim 1 , exciting a fifth plasma from a fifth gas; and
(c) etching through said top diffusion barrier layer using ions from said fifth plasma.