Metal Oxide Lens Coating With SiO-Cr Adhesion Buffer

The patent employs a porous silicon oxide layer with controlled porosity (30-70%) to achieve gradient refractive index. The porous structure allows continuous adjustment of effective refractive index by controlling void ratio, enabling broader adaptability in reflectivity reduction across different wavelengths and angles compared to traditional multilayer coatings.

The patent changes physical parameters including porosity (30-70%), layer thickness (50-200 nm), and pore size (10-100 nm) to optimize anti-reflection performance. By systematically varying these parameters, the coating achieves reflectivity reduction below 1% across visible and near-infrared ranges, exceeding the adjustment range of conventional coatings.

The patent replaces the wet chemical etching method with a dry plasma etching process. This substitution eliminates moisture-related deterioration and reaction residue issues while maintaining the ability to create controlled porous structures. The plasma etching process uses reactive ions to selectively remove material without requiring liquid chemicals, thus improving reliability.

The patent performs the etching process in a controlled plasma environment with inert or reducing atmosphere, preventing oxidation and moisture-related deterioration of the porous silicon oxide layer. This inert environment protection ensures long-term stability and prevents the deterioration issues associated with wet methods.

The patent introduces a gradient refractive index porous silicon oxide layer as an intermediary between the substrate and the top anti-reflection layer. This intermediate structure with gradually changing properties reduces thermal stress concentration and improves interfacial bonding, preventing film separation in high temperature and humidity conditions while maintaining manufacturing ease.

The patent creates a composite structure combining porous silicon oxide with controlled organic content (5-20% carbon). This composite material exhibits intermediate thermal properties between pure oxide and organic layers, reducing thermal coefficient mismatch and improving bonding strength while preventing film lifting during reliability testing.

The patent performs preliminary porosity control during the deposition process itself, creating the gradient structure in a single step rather than requiring subsequent complex processing. By controlling deposition parameters (power, gas flow, temperature) to directly form the desired porosity gradient, the manufacturing complexity is minimized while achieving near-zero reflectivity.

The patent achieves gradient refractive index by systematically varying deposition parameters including radio frequency power (50-200 W), gas flow rates, and substrate temperature (20-100°C). These parameter changes during a single deposition process create the porosity gradient needed for near-zero reflectivity without requiring multiple processing steps, thus controlling manufacturing complexity.