CEA-LETI，Intel开发自由组装模具到磁力技术
法国研究实验室CEA-Leti和英特尔的优化zed a hybrid direct-bonding, self-assembly process that could boost the use of die-to-wafer (D2W) bonding.
该技术可以通过使用水滴对目标晶圆对齐模具来提高对齐精度，并增加每小时数千个模具的制造吞吐量。
D2W hybrid bonding process is seen as essential for combining memory, HPC and photonic chiplets on a wafer substrate, but it is much more complex than wafer-to-wafer bonding, with lower alignment accuracy and lower die-assembly throughput.
CEA-Leti has been developing a self-assembly method for several years, with the goal of substantially increasing throughput and placement accuracy.
“Commercial scale throughput with D2W self-assembly presents two main challenges related to die handling,” said Emilie Bourjot, CEA-Leti’s 3D integration project manager. “If the self-assembly process is combined with a pick-and-place tool, the throughput can be increased by reducing the time of alignment, since the fine alignment is performed by the droplet. When self-assembly is combined with a collective die-handing solution, the throughput is increased by the fact that all dies are bonded together at the same time without any high precision placement at any time along the process flow.”
过程优化也是这项工作的重要组成部分，以提高过程成熟度和目标工业需求。Bourjot说：“通过这样的对齐和吞吐性能，这绝对是一个有前途的步骤，使物理学的魔力和简单的水。”
A paper at the 2022 Electronic Components and Technology Conference (ECTC) this week describes the technique that uses capillary forces that arise from the principle of surface minimization and are exerted through surface tension in the case of a liquid.
From a macroscopic point of view, the liquid tends to minimize its liquid/air interface to reach an equilibrium state with minimized energy. This mechanism allows the self-alignment of the die on its bonding site. The liquid chosen as the realignment vector must present a high surface tension and has to be compatible with direct bonding. Most of the liquids have a surface tension between 20 and 50 mN/m, except water that exhibits a surface tension of 72.1 mN/m, which makes it an excellent candidate for self-assembly process using hydrophilic bonding in which water is already a key mechanism parameter.
CEA-Leti developed a D2W system inhouse that showed a mean misalignment under 150 nm for a wide range of die dimensions (8×8 mm², 2.7×2.7 mm2, 1.3×11.8 mm2 and 2.2×11.8 mm2). This compares to 1µm alignment for a pick-and-place tool post bonding, and the best case of 700nm, while a self-alignment process offers an alignment below 500nm and even less than 200nm, post bonding.
“As no industrial tools for the self-assembly approach exist, the team fabricated its own lab bench enabling a collective self-assembly. The low-reproducibility, manual process control none-the-less achieved alignment of 500nm and below, which strongly suggests that an industrial tool dedicated to this process would deliver higher reproducibility, robustness and precision,” said CEA-Leti.
本文的目的是鼓励组装设备制造商采用该技术。研究人员说：“仍然需要探索自组装的许多方面，并且只有在工具供应商会开发（AN）适应性工具以自动化此过程的情况下，才能进行巨大改进。”
www.leti-cea.com;www.intel.com
