Bumping process to increase bump height and to create a more robust bump structure

A method for the creation of a solder bump, comprising the steps of:

• providing a semiconductor substrate, at least one contact pad having been provided on the surface of said substrate, a layer of passivation having been deposited over the surface of said substrate, said layer of passivation having been patterned and etched creating at least one opening through said layer of passivation that aligns with said at least one contact pad created on the surface of said substrate, exposing the surface of said at least one contact pad;
• depositing a layer of seed material over the surface of said layer of passivation, including the exposed surface of said at least on contact pad;
• creating a layer of Under Bump Metal (UBM) over the surface of said layer of seed material;
• creating a photoresist mask over the surface of said layer of UBM, said photoresist mask having at least one opening that aligns with said at least one contact pad, exposing the surface of said layer of UBM;
• electroplating the exposed surface of said layer of UBM in accordance with said photoresist mask using solder as a source, filling said at least one opening created in said photoresist mask with solder to a solder height, said solder having a top surface;
• removing said photoresist mask from the surface of said layer of UBM, exposing the surface of said layer of UBM;
• etching the exposed surface of said layer of UBM, using said electroplated solder as a mask, exposing the surface of said layer of seed material;
• etching the exposed surface of said layer of seed material, using said electroplated solder as a mask, exposing the surface of said layer of passivation;
• coating a layer of polyimide over the exposed surface of passivation to a polyimide thickness, said polyimide thickness being less than said solder height by a measurable amount, thereby assuring that said solder protrudes from the surface of said layer of polyimide by said measurable amount, said protrusion forming a protruding layer of solder;
• reflowing said protruding layer of solder, thereby creating a solder ball.

A method for forming a bump on a semiconductor substrate, at least one contact pad having been provided on the surface of said semiconductor substrate, comprising the steps of:

• depositing a layer of passivation over said semiconductor substrate, including the surface of said at least one contact pad;
• patterning and etching said layer of passivation, creating at least one opening in said layer of passivation, exposing the surface of said at least one contact pad;
• performing an in-situ sputter clean of the exposed surface of said at least one contact pad;
• depositing a layer of seed material over the surface of said layer of passivation, including said exposed surface of said at least one contact pad;
• plating a layer of Under Bump Metallurgy (UBM) over the surface of said layer of seed material;
• creating a photoresist mask over the surface of said layer of UBM, a pattern of at least one opening of said photoresist mask being aligned with said at least one contact pad provided on the surface of said substrate, exposing the surface of said layer of UBM;
• electroplating the exposed surface of said layer of UBM using solder as a source, forming a pattern of at least on layer of solder aligned with said at least one contact pad provided on the surface of said substrate, said at least one layer of solder having a top surface, said at least one layer of solder having a solder height;
• removing said photoresist mask from the surface of said layer of UBM;
• etching said layer of UBM and said layer of seed material, using said pattern of said at least one layer of solder as a mask, exposing the surface of said layer of passivation;
• coating a layer of polyimide over the exposed surface of said layer of passivation to a thickness such that the top surface of said at least one layer of solder is in a plane above the surface of said coated layer of polyimide;
• applying a solder flux or paste to the top surface of said at least one layer of solder;
• and
• reflowing the surface of said at least one layer of solder, forming at least one solder bump aligned with said at least one contact pad.

At least one solder bump having been created over the surface of a semiconductor substrate, comprising:

• at least one contact pad having been provided on the surface of said substrate;
• a layer of passivation having been deposited over the surface of said substrate, said layer of passivation having been patterned and etched creating at least one opening through said layer of passivation that aligns with said at least one contact pad created on the surface of said substrate, exposing the surface of said at least one contact pad, said layer of passivation having an exposed surface;
• at least one patterned and etched layer of seed material deposited over the surface of said layer of passivation, including the exposed surface of said at least on contact pad, said at least one layer of seed material being aligned with said at least one contact pad;
• at least one patterned and etched layer of Under Bump Metal (UBM) created over the surface of said layer of seed material, said least one layer of UBM being aligned with said at least one layer of seed material;
• at least on layer of solder material having a solder height provided over the surface of said at least one layer of UBM, said least one layer of solder being aligned with said at least one layer of UBM;
• a layer of polyimide coated over the exposed surface of the layer of passivation to a polyimide thickness, said polyimide thickness being less than said solder height by a measurable amount, said solder protruding from the surface of said layer of polyimide by said measurable amount, said protrusion forming a protruding layer of solder;
• said protruding layer of solder having been reflown, thereby having created a solder ball.