Tantalum-based electrode stack

An electronic device comprising:

• a substrate having a high-aspect ratio trench having sidewalls extending from an upper surface of the substrate surface to a trench bottom in the substrate;
• a dielectric insulator liner on the sidewalls in the trench;
• an adhesion layer along the dielectric insulator liner along the sidewalls, the adhesion layer and including a Ta-based material configured to bond to the dielectric insulator liner;
• a platinum group metal (PGM) -based layer on the adhesion layer along the sidewalls;
• an insulator layer on the PGM-based layer along the sidewalls;
• and a second capacitor electrode on the insulator layer and forming, with the PGM-based layer and the insulator layer, metal, insulator and metal portions of a metal-insulator-metal (MIM) capacitor in the trench;
• the sidewalls of the three dimensional structure extend from an exposed region near a surface of the substrate to a buried region within the substrate and have an aspect ratio of at least about 3.5:1 relative to a spacing between the sidewalls near the buried region, and
• the spacing between the sidewalls at the buried region effects deposition step coverage of the Ta-based layer that is less than about 20% of a deposited thickness of the Ta-based layer on a portion of the substrate surface adjacent the exposed region.

A method of forming an electronic device, the method comprising:

• in a substrate, forming a high-aspect ratio trench having sidewalls extending from an upper surface of the substrate surface to a trench bottom in the substrate;
• forming a dielectric insulator liner on the sidewalls in the trench;
• forming an adhesion layer along the dielectric insulator liner along the sidewalls, the adhesion layer including a Ta-based material, and using the Ta-based material to bond to the dielectric insulator liner;
• forming a platinum group metal (PGM) -based layer on the adhesion layer along the sidewalls;
• forming an insulator layer on the PGM-based layer along the sidewalls;
• and forming a second capacitor electrode on the insulator layer to form, with the PGM-based layer and the insulator layer, metal, insulator and metal portions of a metal-insulator-metal (MIM) capacitor in the trench;
• wherein
• forming a high-aspect ratio trench includes forming a trench having an aspect ratio, of height along the sidewalls to width at the trench bottom, of at least 3.5:1, and
• forming an adhesion layer includes forming an adhesion layer along the sidewalls of the trench and on the upper surface of the substrate, the thickness of the adhesion layer near the trench bottom being less than about 20% of the thickness of the adhesion layer on the upper surface of the substrate, as set by the aspect ratio of the trench and the step coverage of the adhesion layer.