Towards reliable pitch assembly using Cu/Ni/SnAg based interconnects

In this paper, the interconnect for 10μm are evaluated. Two processes for obtaining interconnects for 10μm pitch are compared in terms of reliability. One process yields the interconnects with Ni₃Sn₄ intermetallic (IMC) joint (interconnect A) while other yields the interconnects with solder joint (interconnect B). To select the best process for the assembly at 10μm pitch, high temperature storage tests are performed at 150°C, 175°C and 200°C for 500hrs. The evolution of the metallurgy for both the interconnects is evaluated. The failure mechanism is determined by measuring the change in resistance. On the basis of mechanism, failure statistic is made. Finally, the obtained results are discussed.

Introduction

The 3D integration is sustaining the Moore's law by satisfying the growing demand of higher density input/output connection. The law says that the number of transistors per unit area on integrated circuits will double itself every year. One of the main element of 3D Integration is the formation of vertical interconnects with the help of solder. The major challenge in this field is to keep up with the on growing demand of higher density interconnects. Some applications in electronic/optical requires high density packaging, such as microdisplays and IR detectors, for them the interconnection pitch (i.e. the distance between two adjacent interconnect) has gone down to 10um already.