Design and Fabrication of Computer-Generated Holograms for Fresnel Domain Lithography

1. Design and Fabrication of Computer-Generated Holograms for Fresnel Domain Lithography Hologram Domain Photoresist Domain Binary Constraint 1. MSE 2. L1 3. NCC 4. Diffraction Efficiency 5. Uniformity • E-beam field size = 200µmx200µm Photoresist After Development Reconstruction Field Amplitude Off-axis and TIR Geometries Error Metrics Substrate Yes P Initial Guess No Estimated Intensity Binarize? X José A. Domínguez-Caballero,1 Satoshi Takahashi,1 Sung Jin Lee,2 George Barbastathis1,3 1Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 2Samsung Electronics Co. Ltd., Suwon 442-600, South Korea 3Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore 117543 Forward Fresnel Propagation Remove Undesirable Orders 1. Diffracted field 2. Simulated optically recorded hologram 3. Random 4. Continuous phase 5. Simulated optical diffuser Max Iter? Yes Stop No P-1 Fabrication Process Abstract Optimization Results Inverse Fresnel Propagation Zero Absorption Constraint Amplitude Constraint X CGH • CGHs written on electron-beam sensitive resist: Hydrogen Silsesquioxane (HSQ) An optimization algorithm for the design of Fresnel domain computer-generated holograms for lithographic applications is presented. The holograms are fabricated experimentally and their performance characterized. A sensitivity analysis is performed to estimate potential fabrication errors. • Example of in-line CGH: λ = 532nm, d = 250μm, δ = 200nm, • Initial guess: 1. Diffracted field, 2. Simulated optical diffuser z Probing wave Desired intensity 1 Motivation • Need of the semiconductor industry to fabricate ever smaller, faster and lower power consumption devices • Explore novel lithographic techniques • Computer Generated Holography (CGH) is a competitive alternative • Main advantages: • - High-resolution (large effective NA) • - Parallel, non-contact method for mass production • - Optimize diffraction efficiency and uniformity • - Simplified system • - Robust to manufacture errors (encode redundant • information) CGH Characterization Optimized In-line Binary CGH (Phase Map) 2 Error Metrics: 1. Diffracted field Error Metrics: 2. Simulated Optical Diffuser Error Metrics Error Metrics CGH Design • Lithographic implementation in the Fresnel domain Sensitivity Analysis • Simulate potential manufacture errors: CGHs fabricated using electron-beam lithography • Studied errors: 1. Over dose, 2. Under dose, 3. Proximity effect, 4. Stitching error, 5. Phase error Experimental Results Example of Dilation Analysis to Simulate E-Beam Over Dose • CGH phase map optimized using the Modified Error-Reduction (MER) algorithm • Three geometries are studied: in-line, off-axis, and TIR Example of Stitching Error Analysis