Understanding the Stacked Dies Interface Temperature and its Influence During The 3D IC Thermocompression Stacking Process

Abstract

ABSTRACT Scaling limits in IC manufacturing has made 3D IC integration an important approach. With this comes major fundamental challenges and one of these challenges is successfully stacking N>2 dice with an effective bond both mechanically and electrically. Thermocompression stacking is a process in the 3D IC integration flow where dies are bonded directly over each other using pressure and heat. Understanding the effects of pressure and heat during the stacking process provides key learning's in achieving a successful bond. In this paper, we measure the actual temperature in between the interface of two stacked dice during the stacking process. Comparing the materials involved and the changes occurring if set temperatures are modified. We also analyze the influence of these temperature values to the materials involved in the stacking process as a whole. The experiment set involves die to die (D2D) and die to wafer (D2W) stacking. Experiments are done considering units with and without underfill using no-flow and film types. We discuss key understanding on the correlation of the interface temperature between the dies during stacking and the programmed set temperature on the tool of the top and bottom chuck. It also touches on the effects on the bond and underfill reactions with these resulting temperatures. In summary this paper covers tool parameters and material behavior during the thermocompression stacking process. The goal of the paper is to facilitate repeatable successful stacks by understanding one of the major influencing factors in thermocompression stacking, which is temperature.