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Cu post and solder bump structure for semiconductor package

IP.com Disclosure Number: IPCOM000184426D
Original Publication Date: 2009-Jun-24
Included in the Prior Art Database: 2009-Jun-24
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Abstract

Disclosed is a bump on a wafer for flip chip assembly in a fine pitch. By using Cu bump whose both top and side surface is covered with solder, both (1) enough clearance between the chip and the substrate for capillary underfill and (2) enough solder volume for high reliability can be achieved.

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Cu post and solder bump structure for semiconductor package

Disclosed is a bump on a wafer for flip chip assembly in a fine pitch. By using Cu bump whose both top and side surface is covered with solder, both (1) enough clearance between the chip and the substrate for capillary underfill and (2) enough solder volume for high reliability can be achieved.

Background:


In the conventional process of forming solder bumps on chips, the solder balls are placed on the UBM (Under Bump Metal). Using this conventional procedure, it may be difficult to fill the space with under-fill (encapsulation resin) for fine pitch solder bumps such as 50um pitches, because the clearance between the chip and the substrate becomes too small after flip-chip mounting.

To solve this problem, we have been working to develop the C2 (Chip Connection) process as described in Reference (1). The Cu posts are formed high in the C2 process, which is important for assuring clearance between the chip and the substrate after mounting. The larger volume of solder bump is also important for assuring solder connection reliability after mounting.

With the C2 process, Cu posts and solder bumps are formed on the chips. Both the Cu posts and solder bumps are formed by plating. The plating method is as follows:
(1) Form a thin conductive layer over a wafer.
(2) Form a plating resist over the whole surface of the wafer.
(3) Form the opening parts that correspond to the UBMs on chips by exposure and developing.
(4) Form the Cu posts by plating.
(5) Form the solder bumps by plating.
(6) Remove the plating resist by chemical dissolution.
(7) Remove the conductive layer by chemical dissolution.

Using the above process, the height of the Cu posts and solder b...