New paradigm in Cu wire bonding — Design-for-manufacturing

The adoption of Copper (Cu) Wire bonding technology in semiconductor industry is getting popular in achieving not only cost effective solution, but also better product performances and reliability. Intensive research and development efforts were invested in developing softer and higher purity Cu wires, oxidation free zone Cu Kit design, higher bonder capability and accuracy and even the bonding processes. These are not uncommon practices in many backend semiconductor manufacturers in enabling the launching or even smoothening the ramp of Cu wire bonded products. However, the pad damage (or cratering) is remain the major concern that hinder the wide adoption of Cu wire bonded products, especially in automotive application. What is the possible paradigm shift that could achieve the goals more effectively? This paper presents the Multi-Stack bond pad design, a design-for-manufacturing concept that could not only relax the stringent backend manufacturing requirement, but also enable smooth ramp of Cu wire products, especially in addressing the pad damage concerns. In this paper, the combination of different bond pad designs and Cu wire bonding methods are reported. TSLP leadless package is the vehicle for this investigation. 2 types of bond pad designs were investigated with different bonding methods in this study, namely 1) the common Single-Stack AlCu design, and 2) the new Multi-Stacks AlCu with barrier layers in between each stack. As interesting outcome, the new Multi-Stacks AlCu design with robust bonding method has demonstrated superior manufacturability performance over the common Single-Stack design, which could be further explained by Hall-Petch Relationship. Finally, the outcome was proven robust and repeatable which is indeed a new Cu Wire Bonding paradigm for design-for-manufacturing.