IWLPC (Wafer-Level Packaging) Conference Proceedings

Sub-µM 3D For RDL Structures In FO-WLP and Advanced Packaging Using Mult-Sensor Interferometry

Authors: Moritz Jurgschat, Matthias Weber and Ramon Tuason
Company: Sentronics Metrology GmbH and Quantum Analytics
Date Published: 10/18/2016   Conference: IWLPC (Wafer-Level Packaging)

Abstract: FO-WLP has many different process flows, all of which require at least one redistribution layer (RDL) [1]. The manufacturing of this layer involves a full lithography and plating process that needs to be monitored accordingly in a non-destructive metrology loop.

This paper presents a versatile state-of-the-art metrology tool that is capable of measuring the complete process flow with its multi-sensor approach. A high-resolution white-light interferometer (WLI) is used to measure the step heights and CDs of UBM structures with sub-µm vertical and horizontal resolution. The patented Spectral Coherence Interferometry (SCI) technology is used to measure the coating thickness before the exposure step. This is done with a rate of up to 4 kHz enabling full wafer maps to optimize typical areas of low yield such as the center and edge of the wafer.

Key Words: 

Under Bump Metallization (UBM), Redistribution Layer (RDL), Fan-Out Packaging, Mold Wafer, White Light Interferometry, Spectral Coherence Interferometry, Critical Dimension (CD)

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