Backside Illumination Sensor B-Doped Epi-SiGe Layer
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Solution Overview
Problem
The processing sequence for backside illuminated (BSI) CMOS image sensors is lengthy and costly, aiming to improve quantum efficiency while avoiding dark mode image stripe patterns caused by laser annealing.
Innovation Solution
A B-doped Epi-Si(Ge) layer is formed on the thinned substrate's backside, using silicon and germanium to repair surface damage and enhance quantum efficiency, and in-situ doping generates a controllable P-type layer for improved electron leakage and white pixel performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser annealing process is performed to activate implanted P+ ions, then quantum efficiency is improved, but dark mode image stripe patterns are caused due to laser scanning boundary effects
Solution Approach 1:
The patent extracts and removes the laser annealing step from the processing sequence. Instead of using laser annealing to activate P+ ions, the invention uses in-situ doped P-type layer formed during the epitaxial growth process, thereby eliminating the source of dark mode image stripe patterns while maintaining quantum efficiency improvement
Solution Approach 2:
The patent replaces the expensive and problematic laser annealing process with a simpler, more cost-effective in-situ doping approach during epitaxial growth. This substitution eliminates the need for complex laser equipment and processing while achieving the same electrical activation goal without harmful side effects
2Reliability
If multiple processing steps are performed on the backside of the substrate to improve quantum efficiency, then light sensitivity is enhanced, but processing complexity and cost increase
Solution Approach 1:
The patent combines multiple separate processing steps into a single integrated epitaxial growth process. The P-type layer formation, surface damage repair, and quantum efficiency enhancement are all achieved simultaneously through in-situ doping during epitaxial growth, rather than through sequential ion implantation, laser annealing, and oxide growth steps
Solution Approach 2:
The epitaxial growth process with in-situ doping serves multiple functions simultaneously: it forms the P-type layer for electrical activation, repairs surface damage from thinning, and enhances quantum efficiency. This multi-functional approach replaces several specialized processing steps with a single versatile process
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 approach reduces processing complexity and cost while enhancing light sensitivity and image quality by improving quantum efficiency and electron leakage in BSI CMOS image sensors.
Implementation Method 1
a B doped Epi-Si(Ge) layer may be formed on the backside surface of the substrate
Implementation Method 2
In-situ B doped Epi-Si(Ge) layer may generate controllable P-type layer as being p-n junction at BSI Si surface
Data Source
AI summary
Methods and apparatus for a backside illuminated (BSI) image sensor device are disclosed. A BSI sensor device is formed on a substrate comprising a photosensitive diode. The substrate may be thinned at the backside, then a B doped Epi-Si(Ge) layer may be formed on the backside surface of the substrate. Additional layers may be formed on the B doped Epi-Si(Ge) layer, such as a metal shield layer, a dielectric layer, a micro-lens, and a color filter.