A Process Level Comparative Analysis Between D2W Local and Collective 3D Bonding

Abstract

ABSTRACT 3D integration allows to overcome approaching scaling limits for integrated circuits. With this comes numerous versions of processes for 3D bonding and one of this is Die to Wafer (D2W). This method is considered to be a viable method in mass producing 3D stacks. D2W bonding is a stacking scheme in the 3D IC integration flow where diced top dies are bonded individually, using TCB, directly over a whole bottom wafer. There are two general types of D2W bonding. One is to bond each unit applying a complete TCB profile per unit bonded, which is identified as Local bonding. Another is to preplace units on a wafer and collectively apply temperature and pressure for all the units, aptly termed as “collective bonding”. This is with the aid of a compliant material to compensate for thickness and bump height variations. In this paper, we compare the applicability of each process to actual production. We place side by side advantages and disadvantages for both methods with actual bond results. We also take a look on major parameters involved and innovative solutions used to address challenges. Coverage of this paper involves die to wafer stacking. Experiments are done on units with and without underfill using no-flow underfill. The study covers learning’s on the comparison between D2W local and collective bonding. It also touches on major parameters during the stacking process. The paper will cover parameters, equipment and materials involved during the D2W bonding process. The goal of the paper is to show a comparative analysis on what are the advantage and disadvantages with each D2W approach on a process level point of view.