Backside Illumination Metal Shield with Concave Arc Shape

The metal shield structure employs a concave arc shape instead of a flat configuration. This curvature allows the shield to reflect and redirect incident light toward the active image sensors while maintaining a compact form factor. The concave geometry optimizes light collection by directing stray light that would otherwise be lost toward the photosensitive elements, thereby improving quantum efficiency without significantly complicating the manufacturing process.

The metal shield structure is designed with spatially varying properties: the concave arc shape is specifically positioned and dimensioned to provide optimal light shielding and redirection for different regions of the chip. The shield's geometry is tailored to block light from reaching black reference sensors and logic devices while simultaneously directing light toward active image sensors. This localized optimization allows the structure to perform multiple functions with a single integrated design, improving reliability without proportionally increasing overall complexity.

The metal shield structure utilizes specific geometric parameters (concave arc radius, trapezoid angles, shield thickness) that are optimized to achieve high light collection efficiency. By carefully selecting these parameters, the design achieves effective light redirection and shielding while remaining compatible with standard semiconductor manufacturing capabilities. The parameters are chosen to balance performance requirements with manufacturability, ensuring that the enhanced light collection efficiency does not come at the cost of excessive manufacturing precision requirements.