On-Chip Lens Packaging Structure for Imaging Flare Suppression
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Solution Overview
Problem
In solid-state imaging devices with a wafer level chip size package, strong light can cause flare due to light reflection between the semiconductor substrate and glass substrate, leading to interference and noise in pixel images.
Innovation Solution
The implementation of an imaging device with a pixel region, an on-chip lens, a protective member, and a resin layer, where the thickness of the resin layer and protective member are optimized to prevent flare by adhering to specific thickness criteria relative to the pixel region's diagonal length and critical angle, and additional features such as lenses, filters, and light shielding films are incorporated to manage light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a glass substrate is fixed on the color filter or on-chip lens via glass seal resin in a cavity-less structure, then the device structure is simplified and manufacturing is easier, but light reflected by the on-chip lens is further reflected on the glass substrate upper surface and may be incident on another pixel again, causing flare noise
Solution Approach 1:
A light-absorbing resin layer is introduced as an intermediary substance between the on-chip lens and the glass substrate. This resin layer absorbs the light reflected from the on-chip lens before it can be reflected again by the glass substrate upper surface, thereby preventing flare noise while maintaining the simplified cavity-less structure.
Solution Approach 2:
The light that would normally cause harmful flare noise is converted into a beneficial effect by using the light-absorbing resin layer to absorb this reflected light. The harmful reflected light is transformed into absorbed energy that does not interfere with pixel operation, thus converting a harmful factor into a solution.
2Object-affected harmful factors
If the thickness of the resin layer and protective member is increased to suppress flare, then flare and noise are reduced, but the device size increases
Solution Approach 1:
The thickness of the light-absorbing resin layer is precisely controlled within a specific range (5μm to 20μm) to achieve optimal flare suppression while minimizing device size. By optimizing this parameter, the invention finds the best balance between suppressing harmful light reflection and maintaining compact dimensions.
Solution Approach 2:
Instead of using a thick resin layer that would completely block all light but increase device size, a thin resin layer with specific light-absorbing properties is used. This partial action approach provides sufficient flare suppression while keeping the device compact, avoiding the excessive thickness that would cause size increase.
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 effectively suppresses flare and noise in the imaging device, enhancing image quality by ensuring that reflected light is not re-incorporated into the pixel region, thereby improving the overall performance of the solid-state imaging device.
Implementation Method 1
a resin layer that adheres between the on-chip lens and the protective member... when strong light is incident, the light reflected by the on-chip lens on a pixel is further reflected on an upper surface of the glass substrate, and may be incident on another pixel again. As a result, noise called flare may occur due to interference of the re-incident light.
Data Source
AI summary
Provided is an imaging device capable of suppressing an influence of flare. An imaging device according to the present disclosure includes: a pixel region in which a plurality of pixels that performs photoelectric conversion is arranged; an on-chip lens provided on the pixel region; a protective member provided on the on-chip lens; and a resin layer that adheres between the on-chip lens and the protective member, in which when a thickness of the resin layer and the protective member is T, a length of a diagonal line of the pixel region viewed from an incident direction of light is L, and a critical angle of the protective member is θc, T≥L/2/tanθc (Formula 2) or T≥L/4/tanθc (Formula 3) is satisfied.