Overlay Control: Error Budget and Metrology

Level: Introductory Length: 3.5 hours Format: In-Person Lecture Intended Audience: Scientists, engineers, technicians, or managers who wish to learn more about how overlay affects product yield. Fab engineers and researchers want to understand the basic physical enablers and limiters of target and device overlay methods including IBO, DBO, eOVL and IDO. Control and data scientists want to understand how to link all metrology sources and quantify the on-product overlay performance. Description: This course focuses on overlay (OVL) control for product devices detailing the distinct factors affecting on-product overlay (OPO) performance. We delve into key characteristics relevant to OPO, including OVL residuals and non-zero offset (NZO). By exploring the complex, critical inter-relationships among scanner alignment schemes, after-development inspection measurements, and in-die overlay metrology, we build a foundation for better understanding and controlling OPO. Our goal is to enlighten and educate you to better optimize the OPO process for a single and multiple lithographic layers and products in your fab. The course clarifies the fundamental aspects of each metrology technique. This course will benefit those keen on comprehending the factors that shape the landscape of image-based or scatterometry-based overlay, the ongoing challenges of recipe optimization and self-referencing, the measurement and utilization of device overlay, and, most importantly, how all these elements interact and converge. Learning Outcomes: This course will enable you to: - describe the fundamental physical principles and limitations of after-development inspection (ADI) for on-target overlay metrology. You will also be able to rigorously analyze errors leading to misregistration due to optical resolution limitations in single-layer processes. - explain the fundamental physics behind the measurement of on-device overlay or targets similar to devices. - quantify the impact of target-to-device bias which contributes to a non-zero offset. Understand the concept of non-zero offset stability for various alignment and control schemes. - identify the parameters in optical metrology that can be optimized to achieve non-zero offset stability. - explain the basic modeling steps used for calculating overlay, leveling and alignment residuals. The concept of non-zero offset stability will also be introduced for different alignment and control schemes. - discuss the importance and mechanisms of outlier detection. You will learn about distinct outlier detection strategies and when to use them. - identify suitable sampling strategies for modeling and wafer qualification. You will also learn about sampling optimization and uncertainty modeling. - explore error budgeting and its relevance to wafer-to-wafer and lot-to-lot variations. You will be introduced to general concepts related to context variation for process optimization. Additionally, you will explore the use of simulations to validate alternate process settings. Instructor(s): Clemens S. Utzny has been working in the semiconductor industry for the last 20 years. His expertise comprises spatial statistics, modeling of production processes and machine learning. He has published several papers on spatial analysis, process control, process prediction and machine learning within the context of semiconductor manufacturing. Clemens is currently the project line manager for overlay, alignment and leveling for the OVALiS software within the MACH division of KLA Corp. Nadav Gutman has been working on overlay metrology systems for the last 12 years. His expertise includes optical imaging, scatterometry and electron systems. He has published over 38 papers in the fields of optics, metrology and semiconductor fabrication. Additionally, he holds over 27 patents in these areas. Currently, Nadav manages the advanced applications at the overlay metrology division in KLA Corp. He has been a member of SPIE since 2017. Event: SPIE Advanced Lithography + Patterning 2025 Course Held: 23 February 2025