3D Measurement of TSVs Using Low Numerical Aperture White-Light Scanning Interferometry

Abstract

We have proposed and demonstrated a low numerical aperture technique to measure the depth of through silicon vias (TSVs) using white-light scanning interferometry. The high aspect ratio hole like TSV's was considered to be impossible to measure using conventional optical methods due to low visibility at the bottom of the hole. We assumed that the limitation of the measurement was caused by reflection attenuation in TSVs. A novel interference theory which takes the structural reflection attenuation into consideration was proposed and simulated. As a result, we figured out that the low visibility in the interference signal was caused by the unbalanced light intensity between the object and the reference mirror. Unbalanced light can be balanced using an aperture at the illumination optics. As a result of simulation and experiment, we figured out that the interference signal can be enhanced using the proposed technique. With the proposed optics, the depth of TSVs having an aspect ratio of 11.2 was measured in 5 seconds. The proposed method is expected to be an alternative method for 3-D inspection of TSVs.

Methods to Measure the Critical Dimension of the Bottoms of Through-Silicon Vias Using White-Light Scanning Interferometry

“…The low numerical aperture white-light scanning interferometry described by Jo et al [10] is used for the experiment. A TSV hole with high aspect ratio makes it difficult for light to reach the bottom.…”

“…The measurement of depths and diameters of TSVs is very important for the monitoring process during fabrication. Some researchers have tried to measure the depths and diameters of TSVs using scanning electron microscopes [1], infrared (IR) microscopes [2][3][4], diffraction phenomena [5], laser interferometry [6,7], reflectometry [8,9] and white-light interferometry [10,11]. There has been, however, very little research on the critical dimension of the bottom part of the TSV, that is, the bottom CD.…”

Defect Inspection in Display Panel Using Concentrated Auto Encoder

“…Interferometry is used for repeated measurements of PS and inspection. A 3D height image and 2D tomographic image can be obtained from interferometry measurements [8][9][10]. e height of the PS can be measured based on the 3D height image, and the axial CD measurement and the defect of the shape itself can be inspected using the 2D tomographic image.…”

Depth enhancement of 3D microscopic living‐cell image using incoherent fluorescent digital holography

“…The holographic method (Garcia-Sucerquia et al, 2006;Jo et al, 2013;Li et al, 2014;Lim et al, 2012) can overcome the drawbacks of confocal laser scanning fluorescence microscopy by using a recording hologram and can reconstruct a 3D living cell with one hologram. Recording a hologram which is interference pattern requires two coherent light waves, an object beam and a reference beam (Langecheneberg et al, 2008;Lim et al, 2012).…”