SOLID-STATE IMAGE SENSOR INCLUDING PHASE DIFFERENCE DETECTION PIXEL

Smart overview of the Invention

A solid-state image sensor is designed to enhance phase difference detection, crucial for autofocus performance. It comprises a substrate with two opposing surfaces, image pixels each containing a photodiode (PD), and phase difference detection pixels with additional PDs. An anti-reflection layer, made of alternating high and low refractive index layers, is applied to these phase difference detection pixels. This layer includes a light separation slit, composed of a material with a different refractive index, situated closest to the PDs in a direction perpendicular to the substrate.

Background

Solid-state image sensors, like CMOS sensors, are widely used in devices such as digital cameras and smartphones. Traditional sensors have separate phase difference detection pixels to determine image phase differences. However, as pixel arrays become finer, issues arise with separation ratios, affecting autofocus performance. These problems are compounded by increased color mixing and decreased sensitivity due to light scattering from pixel separation patterns.

Challenges and Solutions

To address these challenges, the new design introduces a boundary separation pattern around the photodiodes, improving the separation ratio of incident light. This is particularly beneficial for pixel sizes below 1 μm, where traditional methods struggle. The advanced anti-reflection layer, with its unique refractive index configuration, further enhances light separation and reduces unwanted interactions between light and the sensor surface.

Technical Details

The anti-reflection layer is constructed by stacking high refractive index layers with low refractive index layers. A light separation slit, part of the high refractive index layer, enhances light management by using a material with a distinct refractive index. This configuration ensures the first refractive index layer is optimally positioned relative to the photodiodes, maximizing light separation and sensor performance.

Illustrations

The accompanying diagrams provide visual insights into the sensor's architecture and functionality. They depict the sensor layout, light intensity distributions, and light refraction states under various conditions. These illustrations aid in understanding the improved light management and phase difference detection capabilities of the sensor, highlighting its advancements over traditional designs.