Solid-State Image Sensor Light Waveguide Refractive Index Barrier

A low-refractive-index third insulating film is introduced as an intermediary layer between the high-refractive-index light waveguide and the surrounding environment. This intermediary layer prevents light from leaking into adjacent pixels by creating a refractive index barrier, while still allowing the light waveguide to effectively collect and guide light to the photoelectric conversion element.

The patent applies different refractive index properties to different spatial regions: the light waveguide maintains high refractive index for effective light guidance, while the third insulating film provides low refractive index specifically at the boundaries between adjacent pixels to prevent light leakage. This localized differentiation of optical properties resolves the contradiction between light collection and light isolation.

The patent addresses the sensitivity loss from reduced pixel size by extending the light collection function into the vertical dimension through the light waveguide structure. Instead of relying solely on the horizontal light-receiving area, the waveguide captures oblique light from above and guides it vertically to the photoelectric conversion element, effectively compensating for the reduced surface area.

The light waveguide performs preliminary light collection and concentration before light reaches the photoelectric conversion element. By pre-concentrating oblique light rays through total internal reflection within the waveguide, the system ensures that maximum light energy is delivered to the reduced-size photoelectric conversion element, maintaining sensitivity despite smaller pixel dimensions.