Endpoint Detection in Low Open Area TSV Fabrication Using Optical Emission Spectroscopy

Through-silicon via (TSV) technology is a key enabler for 3-D and 2.5-D integration, which provides low-power and high-bandwidth chip-to-chip communication. During TSV fabrication, over-etching may cause notching at the base of the TSVs, resulting in TSV diameter variations. Endpoint detection (EPD) techniques are critical for controlling TSV diameter, and detecting the endpoint for low open areas presents a serious challenge to process engineers. In this paper, a hybrid partial least squares-support vector machine model for optical emission spectroscopy data are successfully demonstrated for an EPD of low open area TSVs. Accurate EPD results are shown for 120, 80, and 25 \(\mu\) m diameter TSVs.