Browse Prior Art Database

Ball Limiting Annulus Structure for C4 Bump Formation

IP.com Disclosure Number: IPCOM000106316D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 70K

Publishing Venue

IBM

Related People

Kouno, Y: AUTHOR [+3]

Abstract

Disclosed is a C4 (Controlled Collapse Chip Connection) bump structure called BLA (Ball Limiting Annulus) which can avoid diffusion of solder into BLM (Ball Limiting Metallurgy) that causes poor solder bonding. The following is process steps for fabricating the BLA structure:

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Ball Limiting Annulus Structure for C4 Bump Formation

      Disclosed is a C4 (Controlled Collapse Chip Connection) bump
structure called BLA (Ball Limiting Annulus) which can avoid
diffusion of solder into BLM (Ball Limiting Metallurgy) that causes
poor solder bonding.  The following is process steps for fabricating
the BLA structure:

1.    As shown in Fig. 1, terminal via (1) is formed in insulating
    layer (2) to expose a portion of underlying wiringlayer (3).

2.    Metal mask layer (4) such as molybdenum is formed which exposes
    the region where the BLM is to be formed, as shown in Fig. 2.

3.    BLM structure (5) comprising, for example, Cr, Cu, Ni, Au, and
    Cr is formed as by evaporation, as shown in Fig. 3.

4.    After removal of the mask (4), second mask (6) is deposited and
    patterned to expose a central circular region of the BLA
    structure which is slightly smaller in diameter than the BLA
    structure, as shown in Fig. 4.

5.    The surface Cr layer is etched as by RF sputtering or ion
    milling.  Thus, annular Cr layer (7) is left on the top surface
    of the BLA structure (Fig. 4).

6.    Solder (8) such as 3Sn/97Pb or 63Sn/37Pb is deposited as by
    evaporation on the BLA structure (Fig. 5).

7.    After removal of the mask (6), the solder (8) is reflowed (Fig.
    6).

      By using this BLA structure, the problem of BLM lifting shown
in Fig. 7 by "A" which is apt to occur, especial...