Hybrid TSV and method for forming the same

A method, comprising:

• forming a hardmask layer above a contact structure layer formed above a device layer of a substrate;
• forming an opening that extends through said hardmask layer, said contact structure layer and said device layer, and into said substrate;
• forming a first conductive material layer having a first coefficient of thermal expansion above said hardmask layer, wherein forming said first conductive material layer comprises partially filling said opening to form a lower portion of a through-silicon via, wherein, after partially filling said opening, an upper surface of a bottom portion of said first conductive material layer that is formed above a bottom surface of said opening is at a first height below said device layer and sidewall portions of said first conductive material layer formed adjacent to upper sidewalls of said opening extend above said upper surface of said bottom portion, a thickness of said bottom portion of said first conductive material layer being greater than a thickness of said sidewall portions of said first conductive material layer;
• forming a second conductive material layer having a second coefficient of thermal expansion that is less than said first coefficient of thermal expansion above said first conductive material layer, wherein forming said second conductive material layer comprises filling an unfilled upper portion of said opening that is defined above said bottom portion of said first conductive material layer and between said sidewall portions of said first conductive material layer to a second height above said contact structure layer to form an upper portion of said through-silicon via;
• and
• performing a chemical mechanical polishing process to remove excess portions of said first and second conductive material layers formed above said hardmask layer and expose an upper surface of said upper portion of said through-silicon via.

A method of forming a conductive via element extending from a front surface of a substrate to a back surface of said substrate, the method comprising:

• forming a via opening in said substrate, said via opening extending through an interlayer dielectric layer formed above said front surface of said substrate and a device layer formed below said interlayer dielectric layer, wherein a bottom surface of said via opening is positioned proximate said back surface of said substrate;
• performing a non-conformal electrochemical deposition process to deposit a first layer of a first conductive material in said via opening, wherein said first layer comprises a bottom portion having a first thickness formed above said bottom surface of said via opening and sidewall portions having a second thickness formed adjacent to upper sidewalls of said via opening, said first thickness being greater than said second thickness;
• depositing a second layer of a second conductive material that is different than said first conductive material in an unfilled portion of said via opening that is defined above said bottom portion of said first layer and between said sidewall portions of said first layer, said second conductive material having a different coefficient of thermal expansion than said first conductive material;
• and
• performing a back-side thinning operation to expose said bottom portion of said first layer.