ECTC 2022
Conference paper

A Laser Dicing Method for Plus-Shaped Dies for Heterogenous Integration Applications

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With the increasing demand for efficient and high-performance computing for Artificial Intelligence (AI) applications, heterogeneous integration (HI) of multicore accelerator chips on a single chip-carrier is regaining popularity. To enable high-bandwidth communication with reduced latency and power consumption in such complex packages, it is critical to have close spacing and interconnection between these chips. Additionally, it is also important to improve the design to reduce the overall package stresses to prevent mechanical failures during operation while implementing complex packaging required for HI technologies. To achieve these objectives, a novel plus-shaped die is presented in this study.A plus-shaped die has larger perimeter compared to a square shaped die of the same area, increasing the area for edge I/O features for better connectivity. In this paper, a finite-element-based mechanical model is developed to estimate the mechanical stresses in an electronic package with plus-shaped die. The results show considerably lower stresses and improved structural integrity in a package with plus-shaped die compared to those with a square-shaped die.A novel methodology developed to dice a plus-shaped die using laser dicing process is also presented. Three different dicing recipes are developed for dicing, using: single beam (SB), single beam plus dry plasma (SB + DryPlasm), and a multi-beam laser process (VI process) combined with single beam process [1]-[3]. The recipes are optimized to improve the dicing quality by reducing the dicing kerf width and the overcut at the inner corners of the plus shape. The recipes are first used to dice 100 μm thick wafers into plus-shaped dies, with each die consisting of five square-shaped dies arranged in a plus shape. The square-shaped die is 19.2 mm by 19.2 mm in size. The dicing quality is evaluated using an optical microscope. To evaluate the effect on the die strength, rectangular-shaped dies of same thickness are diced using the same recipes; the top and bottom side die strengths are measured using a three-point bend fixture and the results are presented.