Direct Monitoring\nof Nanoscale Deformations across\nAll Layers in Three-Dimensional Stacked Structures

Due\nto its high bandwidth, low latency, low power consumption,\nand compact size, three-dimensional (3D) integration of semiconductor\nchips holds the promise of boosting the performance of integrated\ncircuit systems. However, the applications of 3D stacked structures\nare constrained by the surface deformation of each thin layer induced\nby thermal effects, vibration, gravity, and other environmental stresses.\nTherefore, ensuring the performance and reliability of 3D stacked\nstructures necessitates the precise measurement of nanoscale deformation\nin each layer. Furthermore, the spacing between layers in 3D stacked\nstructures using modern microelectronics and packaging technologies\nis exceedingly small, making it impossible to measure the deformation\nof all layers. Here, we present a novel optical endoscope that fuses\na miniaturized interferometry array, a laser-fabricated microprobe,\nand a highly efficient profile reconstruction algorithm for the precise\nmeasurements of surface deformation across all layers in 3D stacked\nstructures. Our method offers a potentially effective and noninvasive\nway to address the challenges associated with in-line deformation\nmeasurement across all layers in real 3D stacked wafers and chips.