Process of Ultra Thick Trench Etch with Multi-Slope Profile

A method of forming an ultra-thick metal layer, comprising:

• depositing an inter-level dielectric layer above a substrate;
• forming a masking layer above the inter-level dielectric layer, wherein the masking layer has an opening that exposes the inter-level dielectric layer;
• selectively etching the inter-level dielectric layer according to the masking layer to form a cavity having a depth less than a height of the inter-level dielectric layer;
• trimming the masking layer to increase a size of the opening, thereby exposing an additional area of the inter-level dielectric layer;
• selectively etching the inter-level dielectric layer according to the trimmed masking layer to increases a depth of the cavity and to form a sidewall of the cavity that comprises a plurality of sections, wherein respective sections have different slopes that cause the cavity to have a rounded shape;
• and
• depositing a metal material into the cavity to form the ultra-thick metal layer.