Additives for grain fragmentation in Pb-free Sn-based solder

A method of forming a semiconductor structure comprising:

• applying a solder ball on a metallic pad, wherein said solder ball comprises Sn at an atomic concentration of at least 95% and inert nano-sized particles having dimensions from 1 nm to 1,000 nm in all directions and containing a metal oxide selected from a Lanthanide oxide, an Actinide oxide, and a compound thereof;
• and
• reflowing said solder ball at an elevated temperature, wherein said at least one elemental metal or said inert nano-sized particles induce formation of Sn-containing grains as nucleation centers within said solder ball.

A method of forming a semiconductor structure comprising:

• applying a solder ball on a metallic pad, wherein said solder ball comprises Sn at an atomic concentration of at least 95% and inert nano-sized particles having dimensions from 1 nm to 1,000 nm in all directions, wherein said inert nano-sized particles comprise coated metallic particles including a core of an elemental metal or an intermetallic alloy and a surface coating comprising a metal oxynitride, a metal nitride, a metal carbide, a semiconductor carbide, or a metal boride that does not form a chemical compound at a temperature lower than 260° C.;
• and
• reflowing said solder ball at an elevated temperature, wherein said at least one elemental metal or said inert nano-sized particles induce formation of Sn-containing grains as nucleation centers within said solder ball.