METHOD FOR MANUFACTURING FINE-PITCH BUMPS AND STRUCTURE THEREOF
A method for manufacturing fine-pitch bumps comprises the steps of providing a silicon substrate; forming a titanium-containing metal layer on the silicon substrate, wherein the titanium-containing metal layer comprises a plurality of first zones and a plurality of second zones; forming a photoresist layer on the titanium-containing metal layer; patterning the photoresist layer to form a plurality of opening slots; forming a plurality of copper bumps at the opening slots, wherein each of the copper bumps comprises a first top surface and a ring surface; heating the photoresist layer to form a plurality of body portions and a plurality of removable portions; etching the photoresist layer; and removing the second zones to enable each of the first zones to form an under bump metallurgy layer having a bearing portion and an extending portion.
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The present invention is generally related to a method for manufacturing fine-pitch bumps, which particularly relates to the method for manufacturing fine-pitch bumps that prevents copper ions from dissociation.
BACKGROUND OF THE INVENTIONIn structure of fine-pitch bumps, a short phenomenon is easily occurred from a relatively short gap between two adjacent copper bumps owing to the copper ion dissociated by the copper bump.
SUMMARYThe primary object of the present invention is to provide a method for manufacturing fine-pitch bumps comprising the following steps of providing a silicon substrate having a surface, a plurality of bond pads disposed at the surface and a protective layer disposed at the surface, wherein the protective layer comprises a plurality of openings, and the bond pads are revealed by the openings; forming a titanium-containing metal layer on the silicon substrate, the titanium-containing metal layer comprises a plurality of first zones and a plurality of second zones located outside the first zones, the protective layer and the bond pads are covered with the titanium-containing metal layer; forming a photoresist layer on the titanium-containing metal layer; patterning the photoresist layer to form a plurality of opening slots corresponded to the first zones of the titanium-containing metal layer; forming a plurality of copper bumps at the opening slots, each of the copper bumps comprises a first top surface and a ring surface; heating the photoresist layer to ream the opening slots of the photoresist layer, and the heat process enables the photoresist layer to form a plurality of body portions and a plurality of removable portions; etching the photoresist layer to remove the removable portions and expose the titanium-containing metal layer; forming a plurality of bump protection layers on the titanium-containing metal layer, the first top surface and the ring surface of each of the copper bumps, wherein each of the bump protection layers comprises a metallic coverage portion and a bump coverage portion having a second top surface, the first top surface and the ring surface of each of the copper bumps are covered with the bump coverage portion; forming a plurality of wettable layers on the second top surfaces; removing the body portions of the photoresist layer; eventually, removing the second zones of the titanium-containing metal layer to enable each of the first zones of the titanium-containing metal layer to form an under bump metallurgy layer located under each of the copper bumps, each of the under bump metallurgy layers comprises a bearing portion located under each of the copper bumps and an extending portion protruded to the ring surface of each of the copper bumps, and the extending portion of each of the under bump metallurgy layers is covered with the metallic coverage portion of each of the bump protection layers. The protection of the bump protection layers may lower dissociation of copper ions released from the copper bumps, which improves reliability of the fine-pitch bump structure effectively. Besides, the protection also prevents the copper bumps from collapsing when removing the second zones of the titanium-containing metal layer.
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While this invention has been particularly illustrated and described in detail with respect to the preferred embodiments thereof, it will be clearly understood by those skilled in the art that it is not limited to the specific features and describes and various modifications and changes in form and details may be made without departing from the spirit and scope of this invention.
Claims
1. A fine-pitch bump structure at least comprising:
- a silicon substrate having a surface, a plurality of bond pads disposed at the surface and a protective layer disposed at the surface, wherein the protective layer comprised a plurality of openings, and the bond pads are revealed by the openings;
- a plurality of under bump metallurgy layers formed on the bond pads, each of the under bump metallurgy layers comprises a bearing portion and an extending portion;
- a plurality of copper bumps formed on the under bump metallurgy layers, each of the copper bumps comprises a first top surface and a ring surface, the bearing portion of each of the under bump metallurgy layers is located under each of the copper bumps, and the extending portion of each of the under bump metallurgy layers is protruded to the ring surface of each of the copper bumps;
- a plurality of bump protection layers formed on the extending portions of the under bump metallurgy layers, the first top surface and the ring surface of each of the copper bumps, each of the bump protection layers comprises a metallic coverage portion and a bump coverage portion having a second top surface, wherein the first top surface and the ring surface of each of the copper bumps are covered with each of the bump coverage portions, and each of the extending portions is covered with each of the metallic coverage portions; and
- a plurality of wettable layers formed on the second top surfaces of the bump coverage portions.
2. The fine-pitch bump structure in accordance with claim 1, wherein each of the bump coverage portions comprises a first outer lateral surface, each of the metallic coverage portions comprises a second outer lateral surface and is protruded to the first outer lateral surface of the bump coverage portion.
3. The fine-pitch bump structure in accordance with claim 2, wherein the extending portion of each of the under bump metallurgy layers comprises a third outer lateral surface coplanar with the second outer lateral surface.
4. The fine-pitch bump structure in accordance with claim 1, wherein the material of the bump protection layers can be chosen from one of nickel, palladium or gold.
5. The fine-pitch bump structure in accordance with claim 1, wherein the under bump metallurgy layers are made of a material selected from one of titanium/tungsten/gold, titanium/copper and titanium/tungsten/copper.
Type: Application
Filed: May 14, 2013
Publication Date: Sep 26, 2013
Applicant: CHIPBOND TECHNOLOGY CORPORATION (Hsinchu)
Inventors: Cheng-Hung Shih (Changhua County), Yung-Wei Hsieh (Hsinchu City), Shu-Chen Lin (Pingtung County), Cheng-Fan Lin (Hsinchu County), Hua-An Dai (Kaohsiung City)
Application Number: 13/893,623