AFM Assisted Hybrid Bonding Interface Optimization

Abstract

Hybrid bonding is becoming a crucial technique in advanced semiconductor packaging technology; facilitating the integration of high-density interconnects between elements of advanced 3D semiconductor assemblies. Hybrid bonding involves the direct bonding of two semiconductor surfaces consisting of dielectric and metal regions, without the need for adhesive layers. Prior to bonding, the individual semiconductor build’s wafers must be fabricated with precise surface preparation, alignment, and interface management to minimize topography that could degrade the quality of the final bonding. The local and macroscopic topography must be closely monitored at the hybrid bonding interface as both local and macroscopic topography can dramatically affect the quality of the hybrid bonding process and the final bonded assembly. To assist in the optimization of the quality pre-bond joining interface’s surfaces and the resultant quality of the final hybrid bond; Atomic Force Microscopy (AFM) and Atomic Force Profilometry (AFP) have emerged as powerful tools. AFM provides high-resolution three-dimensional topographical maps of the semiconductor surfaces, allowing for the detection and quantification of surface roughness, contamination, and other nanoscale features that influence bonding quality. At the local level, Atomic Force Microscopy (AFM) provides data regarding copper joining pad recess off of the dielectric top surface as well as the top surface’s roughness with sub-nm precision. For macroscopic topography, the use of Atomic Force Profilometry (AFP) and Large Area Scans can be leveraged to observe critical metrology from the nanometer to hundreds of millimeter scales. This can be of particular interest at the bevel edge region’.. This paper describes how of AFM and AFP metrology can be leveraged to yield detailed insights into the surface characteristics at multiple scales and how this data can be leveraged into altering critical surface process conditioning techniques to optimize pre-bond surface quality and enhance the final hybrid bonded part.