Grayscale lithography process study applied to zero-gap microlenses for sub-2μm CMOS image sensors

Abstract

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3D SEM metrology of microstructures for high volume manufacturing

“…It is important to take into consideration that the region of the photodiode is sensitive to light, but not all the pixel surface, which means not all the pixel surface can collect photons. A layer of microlenses is used to focus the incident light onto these photodiodes [2][3][4] To increase the efficiency of the CMOS sensor, every microlens should have a high coverage of the pixel, be light-transparent, and must have a target shape. Consequently, the shape of the microlens should be optimized and controlled.…”

Formation of Curved Micrometer-Sized Single Crystals

“…Fashioning single crystals with curved shapes from functional materials such as noble metals would have high research and technological potential, for example in photonics (microlenses and micromirrors). 12,13 With such functional materials as the starting point, however, obtaining the curved morphologies achieved in biogenic crystals requires additional fabrication steps, such as sculpturing, drilling, and polishing the single crystals, or using standard nanoand microfabrication techniques. 12,14,15 To the best of our knowledge, these procedures have not been applied on micrometer-sized single crystals.…”

“…12,13 With such functional materials as the starting point, however, obtaining the curved morphologies achieved in biogenic crystals requires additional fabrication steps, such as sculpturing, drilling, and polishing the single crystals, or using standard nanoand microfabrication techniques. 12,14,15 To the best of our knowledge, these procedures have not been applied on micrometer-sized single crystals. Polishing and microfabrication have been carried out on curved crystals obtained with gold, but the curvature was on a scale of millimeters and not micrometers.…”

“…Thus, for example, single crystals of calcite were grown through the amorphous calcium carbonate precursor phase on micropatterned templates induced by a self-assembled monolayer on the template surface, or, as another example, using a sponge-like polymer membrane as a template, single crystals of calcium carbonate, lead(II)sulfate, strontium sulfate, and others were grown while being constrained into intricate shapes replicating sea urchin skeletal plates. − These processes were carried out using ceramic materials found in biogenic material such as CaCO 3 , but no such attempts have been made to date with widely used functional technological materials such as metals. Fashioning single crystals with curved shapes from functional materials such as noble metals would have high research and technological potential, for example in photonics (microlenses and micromirrors). , …”