Bump manufacturing method

A method of forming bumps on a silicon wafer having an active surface with a passivation layer and a plurality of bonding pads thereon such that the passivation layer exposes the bonding pads, the method comprising the steps of:

• forming an adhesion layer over the active surface of the wafer, covering both the bonding pads and the passivation layer;
• forming a barrier layer over the adhesion layer;
• forming a wettable layer over the barrier layer;
• conducting a first photolithographic process to from a plurality of photoresist blocks on the wettable layer;
• conducting a first etching operation to remove the wettable layer and the barrier layer outside the photoresist blocks so that only the residual wettable layer and barrier layer underneath the photoresist blocks remain;
• removing the photoresist blocks;
• conducting a second photolithographic process to form a photoresist layer over the adhesion layer, wherein the photoresist layer has a plurality of openings that expose the wettable layer and the adhesion layer around the barrier layer;
• conducting a metal-filling operation to form solder blocks inside the openings of the photoresist layer, wherein the solder blocks cover the wettable layer and the adhesion layer around the barrier layer;
• conducting a first reflux operation to transform the solder blocks into a blob of material having a hemispherical profile such that the solder blocks also retract onto the upper surface of the wettable layer without extending into the adhesion layer;
• removing the photoresist layer;
• conducting a second etching operation to remove the exposed adhesion layer so that only residual adhesion layer underneath the barrier layer is retained and the passivation layer on the wafer is exposed;
• and
• conducting a second reflux operation.

A method of forming bumps over a silicon wafer having an active surface thereon, the method comprising the steps of:

• forming a first under-ball metallic layer over the active surface of the wafer;
• forming a second under-ball metallic layer over the first under-ball metallic layer;
• conducting a first photolithographic process to form a plurality of photoresist blocks over the second under-ball metallic layer;
• conducting a first etching operation to remove the second under-ball metallic layer outside the photoresist blocks so that only the second under-ball metallic layer underneath the photoresist blocks remains;
• removing the photoresist blocks;
• conducting a second photolithographic process to form a photoresist layer over the second under-ball layer, wherein the photoresist layer has a plurality of openings that expose the second under-ball metallic layer;
• conducting a metal-filling operation by depositing metallic material into the openings in the photoresist layer to form solder blocks that cover the second under-ball metallic layer;
• removing the photoresist layer;
• conducting a reflux operation to transform the solder blocks into a blob of material having a hemispherical profile;
• and
• conducting a second etching operation to remove the exposed first under-ball metallic layer so that only the first under-ball metallic layer underneath the second under-ball metallic layer remains.

A method of forming bumps over a silicon wafer having an active surface thereon, the method comprising the steps of:

• forming a first under-ball metallic layer over the active surface of the wafer;
• forming a second under-ball metallic layer over the first under-ball metallic layer;
• conducting a first photolithographic process to form a plurality of photoresist blocks over the second under-ball metallic layer;
• conducting a first etching operation to remove the second under-ball metallic layer outside the photoresist blocks so that only the second under-ball metallic layer underneath the photoresist blocks remains;
• removing the photoresist blocks;
• conducting a second photolithographic process to form a photoresist layer over the second under-ball layer, wherein the photoresist layer has a plurality of openings that expose the second under-ball metallic layer;
• conducting a metal-filling operation by depositing metallic material into the openings in the photoresist layer to form solder blocks that cover the second under-ball metallic layer;
• conducting a reflux operation to transform the solder blocks into a blob of material having a hemispherical profile;
• removing the photoresist layer;
• and conducting a second etching operation to remove the exposed first under-ball metallic layer so that only the first under-ball metallic layer underneath the second under-ball metallic layer remains.

A method of forming bumps over a silicon wafer having an active surface thereon, the method comprising the steps of:

• forming a first under-ball metallic layer over the active surface of the wafer;
• forming a second under-ball metallic layer over the first under-ball metallic layer;
• conducting a first photolithographic process to form a plurality of photoresist blocks over the second under-ball metallic layer;
• conducting a first etching operation to remove the second under-ball metallic layer outside the photoresist blocks so that only the second under-ball metallic layer underneath the photoresist blocks remains;
• removing the photoresist blocks;
• conducting a second photolithographic process to form a photoresist layer over the second under-ball layer, wherein the photoresist layer has a plurality of openings that exposes the second under-ball metallic layer;
• conducting a metal-filling operation by depositing metallic material into the openings in the photoresist layer to form solder blocks that cover the second under-ball metallic layer;
• removing the photoresist layer;
• conducting a reflux operation to transform the solder blocks into a blob of
• material having a hemispherical profile;
• and conducting a second etching operation to remove the exposed first under-ball metallic layer so that only the first under-ball metallic layer underneath the second under-ball metallic layer remains.

A method of forming bumps over the active surface of a silicon wafer, the method comprising the steps of:

• forming a first under-ball metallic layer over the active surface of the wafer;
• forming a second under-ball metallic layer over the first under-ball metallic layer;
• removing a portion of the second under-ball metallic layer to expose the first under-ball metallic layer;
• implanting at least one solder block over the second under-ball metallic layer;
• conducting a reflux operation;
• and removing the exposed first under-ball metallic layer so that the first under-ball metallic layer underneath the second under-ball metallic layer remains.