Image Sensor Deep Trench Isolation for Crosstalk Reduction
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Solution Overview
Problem
Existing image sensing devices face challenges in reducing optical crosstalk between adjacent pixels, which affects image quality and signal-to-noise ratio.
Innovation Solution
The implementation of a deep trench isolation (DTI) layer, including a backside DTI structure, a light blocking layer, and a bias voltage system to suppress dark current and minimize optical crosstalk between active and optical black pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a deep trench isolation (DTI) layer is implemented to reduce optical crosstalk, then optical crosstalk between adjacent pixels is reduced, but device complexity increases
Solution Approach 1:
The substrate is divided into isolated regions by deep trenches filled with insulating material, creating physically separated pixel units. This segmentation prevents optical photons from traveling between adjacent pixels through the substrate, effectively reducing optical crosstalk while maintaining functional pixel operation
Solution Approach 2:
The DTI structure is selectively implemented at specific locations where optical crosstalk occurs between adjacent pixels, rather than uniformly across the entire device. This localized approach reduces crosstalk in critical areas while minimizing the overall increase in device complexity
2Reliability
If a bias voltage is applied to suppress dark current, then dark current is suppressed, but power consumption increases
Solution Approach 1:
A bias voltage is pre-applied to the DTI electrode before image capture to establish an electric field that repels charge carriers. This preliminary action creates a potential barrier that prevents dark current generation at the pixel-substrate interface, suppressing dark current before it can affect image quality
Solution Approach 2:
The bias voltage level is optimized to achieve sufficient dark current suppression while minimizing power consumption. By carefully controlling the voltage parameter, the system achieves the necessary electrical field strength to block dark current without excessive energy expenditure
3Reliability
If the light blocking layer is made electrically conductive to transmit bias voltage, then bias voltage transmission is improved, but optical blocking performance may be compromised
Solution Approach 1:
The light blocking layer is designed to simultaneously perform two functions: optically blocking light from reaching the substrate and electrically conducting bias voltage to the DTI electrode. This multi-functional design eliminates the need for separate optical and electrical components, reducing overall device complexity
4Reliability
If vertically extended portions of electrodes are added between adjacent pixels, then dark current suppression is improved, but device complexity increases
Solution Approach 1:
The vertically extended electrode portions are integrated within the existing DTI trench structure, nesting the electrical field extension function within the optical isolation framework. This allows the electrode to extend vertically into the trench to enhance dark current suppression without requiring additional external structures
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 configuration effectively reduces optical crosstalk, enhancing image quality and signal-to-noise ratio by minimizing noise contributions from adjacent pixels.
Implementation Method 1
a plurality of photoelectric conversion elements formed in the substrate and operable to convert incident light into photocharge
Implementation Method 2
a light blocking layer formed over the substrate surface of the substrate to block light from transmitting therethrough
Data Source
AI summary
This patent document discloses embodiments of image sensing devices including, an image sensing device which includes a substrate including a substrate surface and a trench extending from the substrate surface, a plurality of photoelectric conversion elements formed in the substrate and operable to convert incident light into photocharge, an electrode formed in the trench and configured to receive a bias voltage for suppressing a dark current, and a light blocking layer formed over the substrate surface of the substrate to block light from transmitting therethrough, and configured to be electrically conductive to receive the bias voltage and transmit the received bias voltage to the electrode.