Light-Absorbing DTI Layer for P-Type Diffusion in Image Sensors
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Solution Overview
Problem
The high temperatures involved in the dopant activation process for CMOS image sensors can induce imperfections such as dislocations and surface peeling, reducing the full well capacity and performance, while lowering the temperature to avoid these issues results in insufficient dopant diffusion, affecting the number of white pixels and dark current.
Innovation Solution
A light absorbing layer is introduced between the sidewalls of the deep trench isolation structure, which absorbs light during the dopant activation process, preventing imperfections and providing tensile stress to promote sufficient dopant diffusion into the substrate, thus enhancing the full well capacity and performance without impairing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high temperature is used for dopant activation process, then dopant diffusion is sufficient, but imperfections such as dislocations and surface peeling occur
Solution Approach 1:
The patent introduces a light absorbing layer at specific locations (between DTI sidewalls) to create localized heating. This allows the dopant activation process to occur at high temperature only in the regions where dopant diffusion is needed, while other regions remain at lower temperatures to avoid thermal damage such as dislocations and surface peeling.
Solution Approach 2:
The light absorbing layer acts as an intermediary that converts optical energy to thermal energy selectively. By absorbing light during the annealing process, it generates localized heat that promotes dopant diffusion without requiring the entire substrate to be heated to high temperatures, thus preventing thermal damage while ensuring sufficient dopant activation.
2Reliability
If low temperature is used for dopant activation process, then device imperfections are avoided, but dopant diffusion is insufficient
Solution Approach 1:
The patent utilizes the phase transition of light energy to thermal energy through the light absorbing layer. During the annealing process, the light absorbing layer absorbs optical energy and converts it to heat, creating a localized high-temperature zone that enables sufficient dopant diffusion even when the overall substrate temperature is kept low to prevent thermal damage.
3Manufacturing precision
If light absorbing layer is added to enhance dopant diffusion, then full well capacity is improved, but device complexity increases
Solution Approach 1:
The light absorbing layer is segmented and positioned only in specific critical regions (between DTI sidewalls) rather than being applied uniformly across the entire substrate. This targeted approach enhances dopant diffusion where needed while minimizing the overall addition of structural complexity to the device.
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 light absorbing layer effectively prevents imperfections at high annealing temperatures and ensures adequate dopant diffusion, maintaining or improving the full well capacity, number of white pixels, and dark current performance of CMOS image sensors.
Implementation Method 1
A light absorbing layer is introduced between the sidewalls of the deep trench isolation structure, which absorbs light during the dopant activation process
Implementation Method 2
absorbs light during the dopant activation process, preventing imperfections and providing tensile stress to promote sufficient dopant diffusion
Implementation Method 3
providing tensile stress to promote sufficient dopant diffusion into the substrate
Data Source
AI summary
In some embodiments, the present disclosure relates to a method for forming an integrated chip (IC), including forming a plurality of image sensing elements including a first doping type within a substrate, performing a first removal process to form deep trenches within the substrate, the deep trenches separating the plurality of image sensing elements from one another, performing an epitaxial growth process to form an isolation epitaxial precursor including a first material within the deep trenches and to form a light absorbing layer including a second material different than the first material within the deep trenches and between sidewalls of the isolation epitaxial precursor, performing a dopant activation process on the light absorbing layer and the isolation epitaxial precursor to form a doped isolation layer including a second doping type opposite the first doping type, and filling remaining portions of the deep trenches with an isolation filler structure.