A scheme in which a packaging process (post-process) and a wafer process (pre-process) are integrated to each other to complete a packaging step in a wafer state, i.e., a technique so-called a wafer level CSP, has the following advantage. That is, since a packaging process is performed by applying a wafer process, the number of steps can be made considerably smaller than that of a conventional method in which a packaging process (post-process) is performed to each chip cut from a wafer. The wafer level CSP is also called a wafer process package (WPP).
In the wafer level CSP, a wiring layer in the CSP called an interposer for converting the pitch of bonding pads into the pitch of solder bumps can be replaced with rerouting layers formed on a wafer. For this reason, the wafer level CSP is expected to achieve the reduction in number of steps and the reduction in manufacturing cost of a CSP.
The wafer level CSP is described in, e.g., “Electronic Packaging Technology 2000 Special Number” issued by Gijyutsu-chyosa-kai Corporation (issued on 28th May, 2000) pp. 81 to 113, International Patent Publication No. WO99/23696, Japanese Patent Laid-Open Publication No. 2000-91339, Japanese Patent Laid-Open Publication No. 2000-138245, Japanese Patent Laid-Open Publication No. 2000-216253, and the like.