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.