Buffer cap layer to improve MIM structure performance

A method of forming a MIM (metal-insulator-metal) structure, comprising:

• forming a lower conductive layer over a semiconductor substrate;
• depositing an un-patterned upper conductive layer at a position separated from the lower conductive layer by a dielectric layer;
• patterning the un-patterned upper conductive layer according to a masking layer to form an upper conductive layer;
• performing a post patterning treatment to form an oxide interface layer on sidewalls of the upper conductive layer;
• forming a buffer cap layer comprising an un-doped silicate glass (USG) in-situ with the post patterning treatment;
• and
• forming a stress-inducing protective layer onto the buffer cap layer, wherein the stress-inducing protective layer has a sidewall that is laterally aligned with a sidewall of the dielectric layer, and wherein the buffer cap layer is configured to reduce a compressive stress induced laterally onto the upper conductive layer by the stress-inducing protective layer.

A MIM (metal-insulator-metal) structure, comprising:

• a bottom conductive layer disposed over a semiconductor substrate;
• a dielectric layer disposed over the bottom conductive layer;
• an upper conductive layer disposed over the dielectric layer;
• a buffer cap layer disposed over the upper conductive layer;
• and
• a stress-inducing protective layer vertically arranged between the buffer cap layer and a dielectric material laterally surrounding a metal via layer that vertically extends through the stress-inducing protective layer, wherein the buffer cap layer is configured to reduce a compressive stress laterally induced onto the upper conductive layer by the stress-inducing protective layer.