Gradient-Descent-Based Control of Moving Deposition for Large-Aperture Multilayer Films

To address the challenge of achieving uniform coating on large-aperture substrates with significant sagittal height differences, this study employs a conventional-sized movable sputtering target combined with substrate rotation to realize high-uniformity control. The research establishes a geometric deposition model for the spatial thickness distribution of thin films on large-aperture, high-sagittal-height substrates and develops a precise control method for the deposition distribution on the substrate surface. Using the gradient descent algorithm, an optimal velocity modulation curve is calculated, and the spatial thickness distribution under this curve is determined. Compared with traditional least-squares optimization, this method effectively overcomes the issues of slow computation speed and poor convergence in large-scale numerical calculations, enabling rapid and uniform spatial control of large-aperture substrates. Calculation results demonstrate that the proposed method reduces the film non-uniformity from over 60% to a final value of 2.66%, with a corresponding PV value of 2.61%, across the 6550 mm aperture, showcasing its high precision.