Image Sensor Pinning Layer Superlattice for Higher Carrier Mobility
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Solution Overview
Problem
Current semiconductor devices face limitations in achieving enhanced performance due to constraints in charge carrier mobility and material properties, despite advancements in strained materials and superlattice structures.
Innovation Solution
The development of a semiconductor superlattice structure with energy band-modifying layers, comprising stacked base semiconductor monolayers and non-semiconductor monolayers, which reduces the effective mass of charge carriers and enhances mobility, while also providing piezoelectric, pyroelectric, and ferroelectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional semiconductor materials and structures are used, then manufacturing simplicity is maintained, but charge carrier mobility remains limited
Solution Approach 1:
The semiconductor layer is segmented into multiple alternating monolayers of different materials (e.g., Si/SiGe, Si/SiC) to form a superlattice structure. This segmentation creates distinct regions with different band structures that collectively enhance charge carrier mobility through reduced effective mass and scattering effects, while maintaining a manageable manufacturing complexity through systematic repetition of the layered pattern.
Solution Approach 2:
The patent employs composite material structures where alternating layers of different semiconductor materials (Si, SiGe, SiC) are combined to form a superlattice. This composite approach leverages the complementary properties of each material to achieve enhanced charge carrier mobility that cannot be obtained with single-material systems, while the regular periodic structure keeps manufacturing complexity controllable.
2Speed
If strained material layers are introduced to enhance mobility, then charge carrier mobility improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent systematically varies critical parameters including layer thickness (controlling strain magnitude), composition ratios (e.g., Ge concentration in SiGe), and layer sequence to optimize charge carrier mobility. By carefully adjusting these parameters within specific ranges, the patent achieves enhanced mobility while maintaining manufacturability through well-defined process windows rather than requiring extreme precision.
Solution Approach 2:
The superlattice structure introduces local variations in material composition and strain distribution at the monolayer scale, creating localized regions with optimized properties for charge carrier transport. Each alternating layer pair provides localized strain and band structure modification, while the overall device maintains uniform electrical characteristics through periodic repetition of these locally optimized units.
3Reliability
If superlattice structures are implemented, then charge carrier mobility and conductivity improve, but dopant diffusion control becomes more challenging
Solution Approach 1:
The alternating superlattice layers act as intermediary barriers that modulate dopant diffusion. The periodic structure of different materials creates a series of potential barriers and channels that can be engineered to control dopant transport, allowing enhanced mobility for charge carriers while providing controlled pathways or barriers for dopant atoms, thus stabilizing dopant distribution.
Solution Approach 2:
The patent adjusts material composition parameters (e.g., Ge content in SiGe layers) and layer thickness parameters to create energy barriers that selectively influence dopant diffusion. By optimizing these parameters, the superlattice structure provides sufficient resistance to unwanted dopant diffusion while maintaining high charge carrier mobility through the same structural features.
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 superlattice structure improves charge carrier mobility and reduces scattering effects, leading to enhanced performance in semiconductor devices, including improved conductivity and reduced dopant diffusion, suitable for advanced imaging and opto-electronic applications.
Implementation Method 1
The superlattice structure with energy band-modifying layers reduces the effective mass of charge carriers and enhances mobility
Implementation Method 2
The superlattice structure provides piezoelectric, pyroelectric, and ferroelectric properties
Implementation Method 3
The superlattice structure provides piezoelectric, pyroelectric, and ferroelectric properties
Implementation Method 4
The superlattice structure provides piezoelectric, pyroelectric, and ferroelectric properties
Implementation Method 5
This superlattice structure improves charge carrier mobility and reduces scattering effects
Data Source
AI summary
A method for making an image sensor device may include forming a pixel region within a semiconductor substrate comprising a first dopant having a first conductivity type, forming a first pinning layer on a surface of the substrate and including a second dopant having a second conductivity type different the first conductivity type, and forming a second pinning layer in the semiconductor substrate adjacent at least one side of the pixel region and including a superlattice and the second dopant. The superlattice may include a plurality of stacked groups of layers, with each group of layers comprising a plurality of stacked base semiconductor monolayers defining a base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions.