Quantitative Projections of the Cost Benefits of 3D Integration

Abstract

The traditional drivers for the adoption of 3D integration technology are footprint, power, performance, and/or bandwidth gains at the expense of increased cost due to additional wafer processing, dies stacking and 3D test. However, for larger dies in cutting edge technology, total system cost can be reduced by leveraging heterogeneous 3D stacking, if it is done correctly. This paper presents a model which allows comparing the cost of moving a traditionally designed chip at given advanced node (in 2D) to an implementation in the next generation technology node using heterogeneous face-to-face 3D stacking. With this model we show that 3D integration scheme can be driven by cost savings. This is possible in a world where CMOS cost per transistor continues to improve because other components that are required in large SoCs, notably analog and I/O functionality, do not. The proposed model is used to evaluate the cost impact of iterating a 14nm SoC into a 10nm SoC (traditional scaling) compared to a 3D implementation that pulls the analog and I/O circuitry into a cheap 28nm top die. The cost impact of such a transition is evaluated for different starting SoC sizes (from 100 to 400mm2), differing area percentages of analog I/O (15–40% of the total 2D area), different increases in complexity (measured in implicit number of transistors). In the most realistic and representative cases studied, 28–10nm heterogeneous 3D stack reduced large-die package cost from 5% to 10%. Sensitivity analysis to various model parameters show that these savings are fairly robust, persisting through various scenarios unfavorable to this integration technique.