CMOS Image Sensor UV Pass Filter for Uniform Curing
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Solution Overview
Problem
CMOS image sensors experience noise characteristic degradation due to asymmetry between main pixels and optical block pixels, caused by differing UV curing effects, which can lead to plasma damage and dark current discrepancies.
Innovation Solution
Incorporating a UV pass filter with insulation and metal layers in the optical block area to block visible light and allow UV light transmission, ensuring uniform UV curing effects for both main and optical block pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical block area blocks visible light to determine offset values, then the black level correction function is improved, but the UV curing effect becomes asymmetric between main pixels and optical block pixels, causing dark current characteristic degradation
Solution Approach 1:
The patent applies a UV pass filter specifically to the optical block area pixels, creating a local quality difference between optical block pixels and main pixels. This allows UV light to selectively reach optical block pixels during curing while blocking visible light, enabling uniform UV curing effect for offset calibration without compromising the black level correction function.
Solution Approach 2:
The UV pass filter acts as an intermediary component that mediates between the conflicting requirements of visible light blocking (for offset determination) and UV light transmission (for uniform curing). The filter allows UV wavelengths to pass through while blocking visible wavelengths, resolving the asymmetry problem in UV curing effects.
2Ease of manufacture
If the optical block area is used for offset calibration by blocking light, then the pixel output offset value determination is improved, but plasma damage occurs and UV curing becomes ineffective for optical block pixels
Solution Approach 1:
The patent introduces a UV pass filter with specific wavelength selectivity applied locally to the optical block area. This filter has high transmission for UV wavelengths (enabling effective curing) and high blocking for visible wavelengths (maintaining offset calibration function), thus resolving the contradiction between ease of manufacture and resistance to harmful factors.
Solution Approach 2:
The UV pass filter changes the wavelength parameter of transmitted light, allowing UV wavelengths to pass while blocking visible wavelengths. This parameter-based differentiation enables the optical block pixels to receive UV curing effectively while maintaining their offset calibration function, preventing plasma damage effects.
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
This solution prevents plasma damage and ensures uniform dark current characteristics between main and optical block pixels, thereby improving image noise quality by allowing UV light to be applied uniformly during the curing process.
Implementation Method 1
an optical block structure suitable for blocking a visible light and passing a UV light
Implementation Method 2
UV erase, that is, UV anneal may be performed
Implementation Method 3
The photodiode serves to convert light incident from outside into an electric charge
Data Source
AI summary
A CMOS image sensor includes an active pixel structure suitable for sensing light incident from outside and converting a sensed light into an electrical signal, and an optical block structure suitable for blocking a visible light and passing a UV light to check and evaluate an electrical characteristic of the active pixel area. The UV pass filter includes first and second insulation layers comprising an insulator, and a metal layer formed between the first and second insulation layers.