Copper wire bonding has huge cost advantages over gold wire bonding. As a result, low pin count, heavy wire applications have already been converted to copper wire and many companies are in high volume production. Recently, with the price of gold skyrocketing, conversion of high pin count (>250 I/O), high performance applications to Cu has dramatically accelerated. These high performance devices are increasingly relying on low-k materials under the bond pads. Unfortunately, the 33% greater hardness of Cu compared to gold places even greater stress on these inherently fragile materials. This can result in difficulties with pad damage and cratering of the underlying structures. Advancements have been made to copper wire bonders, tools, and wire that have resolved many of these issues and made fine pitch copper wire bonding feasible. Ni-based bond pads have emerged to solve the pad damage problem. Nickel is about 50% harder than copper and four times harder than aluminum so that it provides greater protection against the higher stress resulting from Cu ball bonding, as well as damage during probe. This is especially beneficial for devices with low-k active circuitry under the bond pad. NiPd, NiPdAu, and/or NiAu have demonstrated their great robustness to receive the Cu wire bonding with a huge wire bonding window without any splash and with excellent reliability.

The need for lower effective dielectric constants for both inter-and intra-layer dielectrics is clearly stated in the International Technology Roadmap for Semiconductors (I).Recently some progress has been reported with regards to integration and reliability assessment of these new, relatively weak porous ultra low-k materials (2-4). Due to their mechanical weakness, these materials also present 'unique challenges to the packaging process. If no appropriate precautions are taken, the pans cannot be packaged at all. In this paper first results are presented for packaging of a porous ultra low-k material with different integration schemes, employing three assembly iechniques: flip chip, gold ball bonding, and aluminum wedge bonding. All of these assembly techniques achieved good assembly yields when proper integration schemes were used.

No abstract

No abstract

No abstract