K. Haberland, C. Camus, LayTec AG, Berlin, Germany
Large-area advanced packaging and integrated photonics place increasingly stringent requirements on thin-film deposition processes, including tight control of thickness uniformity, surface roughness, and mechanical stress across wafers and large substrates. Deviations in film stress and substrate bow can directly impact yield, alignment accuracy, and long-term reliability, making early detection of process instabilities a critical challenge in high-volume manufacturing environments. Optical in-situ metrology provides a non-destructive and real-time solution to address these requirements by monitoring key film and substrate parameters directly during deposition.
In this presentation, we introduce optical in-situ measurement techniques such as pyrometry, reflectometry, and deflectometry and focus on their application to sputter processes relevant for large-area advanced packaging and integrated photonics. In collaboration with industrial partners, these techniques have been implemented in various sputter deposition environments to evaluate the benefits of continuous process feedback. Particular emphasis is placed on the in-line analysis of large-area transparent conductive oxide (TCO) layers deposited on glass substrates. Here, optical reflectometry enables continuous monitoring of layer thickness and surface roughness, while also highlighting challenges arising from rough surfaces and unknown or varying underlying layers that directly affect thickness accuracy and optical performance.
In addition, curvature and wafer-bow measurements during magnetron sputtering of various thin films on silicon wafers are presented. The results demonstrate how film stress and resulting wafer deformation can be deliberately tuned between compressive and tensile regimes through targeted process parameter adjustments. At the same time, unintended process deviations are shown to produce characteristic curvature signatures, making in-situ bow monitoring a highly sensitive indicator for stress-related reliability risks.
Given the critical importance of thickness uniformity, stress control, and wafer bow for large-area advanced packaging and photonic integration, these results provide valuable insights for both process optimization and high-volume manufacturing.