Image Sensor Optical Stack for Ambient Light Rejection
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Solution Overview
Problem
Conventional image sensor structures suffer from increased susceptibility to ambient light interference due to the large distance and angle of incidence of light onto the optical filter, leading to reduced Signal-to-Noise Ratio (SNR) and suboptimal illumination of the photo-sensitive region.
Innovation Solution
A device for an image sensor featuring an optical stack with a filter region and prism regions that selectively transmit incident light within a target wavelength range, minimizing interference and ensuring optimal illumination by guiding light efficiently to the photo-sensitive region with a minimal distance and controlled angle of incidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an optical filter is integrated in a package with the optical sensor, then the filter can selectively transmit light in a target wavelength range, but the distance between the filter and the optical sensor increases, allowing more ambient light to reach the sensor
Solution Approach 1:
The optical filter and optical sensor are merged into a single integrated device structure, where the filter is positioned directly above the photo-sensitive region. This eliminates the need for a separate package and minimizes the distance between the filter and sensor, reducing ambient light interference while maintaining wavelength selectivity.
Solution Approach 2:
The patent transitions from a planar package layout to a vertical stacked architecture, where the optical filter, prism regions, and photo-sensitive region are arranged in layers along the vertical dimension. This dimensional reorganization allows the filter to be positioned immediately above the sensor, minimizing horizontal distance and improving optical coupling.
2Object-affected harmful factors
If the optical filter is positioned at a large distance from the optical sensor, then the filter structure can be simpler, but light hits the filter at large angles, increasing ambient light transmission
Solution Approach 1:
The optical filter is segmented into multiple functional regions including a first optical region with a first prism, a second optical region with a second prism, and a third optical region without prisms. Each region is positioned at a different distance from the photo-sensitive region, allowing selective optimization of light guidance for different angular ranges while managing overall device complexity.
Solution Approach 2:
Different regions of the optical filter are assigned different structural properties: the first and second optical regions contain prisms for specific angle correction, while the third optical region has a simpler structure. This local differentiation allows the filter to handle various incident light angles appropriately without requiring complex structures throughout the entire device.
3Object-affected harmful factors
If the optical filter is positioned close to the optical sensor, then ambient light interference is reduced, but the illumination of the photo-sensitive region may become suboptimal
Solution Approach 1:
Prism regions are introduced as intermediary optical elements between the optical filter and the photo-sensitive region. These prisms mediate the light path by correcting incident angles and guiding light effectively, ensuring that even with the filter positioned close to the sensor, optimal illumination is achieved while maintaining reduced ambient light interference.
4Reliability
If multiple optical regions with different structures are used, then light guidance is improved, but the device complexity increases
Solution Approach 1:
The optical filter is divided into multiple segments or regions, each with a specific function. The first optical region has a first prism for correcting specific angle ranges, the second optical region has a second prism for other angle ranges, and the third optical region has a simpler structure. This segmentation allows optimized light guidance for different incident angles while keeping each individual region relatively simple.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the SNR and improves illumination of the photo-sensitive region by effectively filtering out unwanted light and directing target wavelength light to the sensor, reducing ambient light interference and enhancing image sensor performance.
Implementation Method 1
an optical stack formed on a surface of the semiconductor device for guiding the incident light towards the photo-sensitive region
Implementation Method 2
The plurality of regions comprise a filter region configured to selectively transmit the incident light
Implementation Method 3
a filter region configured to selectively transmit the incident light only in a target wavelength range
Implementation Method 4
configured to selectively transmit the incident light only in a target wavelength range
Implementation Method 5
The photo-sensitive region is configured to generate an electric signal based on incident light
Data Source
AI summary
A device for an image sensor is provided. The device includes a semiconductor device having a photo-sensitive region and a metallization stack for electrically contacting the photo-sensitive region. The photo-sensitive region is configured to generate an electric signal based on incident light. Further, the device includes an optical stack formed on a surface of the semiconductor device and configured to guide the incident light towards the photo-sensitive region. The optical stack includes a plurality of regions stacked on top of each other. The plurality of regions includes a filter region configured to selectively transmit the incident light only in a target wavelength range.