Process for forming metal-insulator-metal structures

A method, comprising:

• receiving a substrate including a lower contact feature;
• depositing a silicon nitride layer over a substrate, including over the lower contact feature;
• depositing a first silicon oxide layer over the silicon nitride layer;
• forming a conductor plate layer over the first silicon oxide layer;
• depositing a second silicon oxide layer over the conductor plate layer;
• performing a first etch process to form an opening through the second silicon oxide layer to expose the conductor plate layer;
• performing a second etch process to extend the opening through the conductor plate layer to expose the first silicon oxide layer;
• and
• performing a third etch process to further extend the opening through the first silicon oxide layer and the silicon nitride layer to expose the lower contact feature,
• wherein the first etch process comprises a first etchant, the second etch process comprises a second etchant, and the third etch process comprises a third etchant,
• wherein the first etchant and the third etchant comprise fluorine,
• wherein the second etchant consists essentially of chlorine.

A semiconductor device, comprising:

• a lower contact feature;
• a first dielectric layer over the lower contact feature;
• a metal-insulator-metal (MIM) structure over the first dielectric layer;
• a second dielectric layer over the MIM structure;
• and
• a contact via extending through the first dielectric layer, the MIM structure, and the second dielectric layer to be in direct contact with the lower contact feature, the contact via comprising a first portion through a thickness of the first dielectric layer, a second portion through a thickness of the MIM structure, and a third portion through a thickness of the second dielectric layer,
• wherein the first portion tapers substantially linearly at a first angle,
• wherein the second portion tapers substantially linearly at a second angle greater than the first angle,
• wherein the third portion tapers substantially linearly at a third angle smaller than the second angle.