Deep Trench Isolation Structure for Pixel Optical Noise Reduction
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Solution Overview
Problem
Existing semiconductor processing methods fail to adequately separate optically adjacent pixels, leading to unwanted noise and reduced signal-to-noise ratio (SNR) due to wavelength interference, especially with increasing aspect ratios.
Innovation Solution
Formation of deep trench isolation (DTI) structures with a high aspect ratio, involving etching, surface repair, epitaxial layer growth, dopant engineering, and filling with optically reflective material, minimizing optical interfaces and using selective refractive and reflective layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixels are placed in close proximity to increase density, then productivity increases, but optical interference between adjacent pixels increases causing noise and reduced signal-to-noise ratio
Solution Approach 1:
The patent divides the substrate into isolated pixel regions by etching deep trenches between adjacent pixels. These trenches are filled with reflective material and lined with dielectric layers to create optical barriers that segment the pixel array, preventing light from one pixel from interfering with adjacent pixels while maintaining high pixel density.
Solution Approach 2:
The patent introduces intermediary structures between adjacent pixels, specifically deep trenches filled with optically reflective material and lined with dielectric layers. These intermediary structures act as optical barriers that block light propagation between pixels, eliminating cross-pixel interference while allowing pixels to remain in close proximity.
2Reliability
If deep trenches with high aspect ratio are etched to improve optical isolation, then signal-to-noise ratio increases, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent creates deep trenches that serve multiple functions simultaneously: they provide mechanical separation between pixels, act as optical barriers through reflective material filling, and create cavities for additional optical management layers. This multi-functionality reduces the need for separate structures and simplifies the overall device architecture despite the high aspect ratio.
Solution Approach 2:
The patent employs composite structures within the deep trenches, combining optically reflective material with dielectric liner layers and additional optical management layers. This composite approach optimizes both optical isolation and structural integrity, managing stress and enabling the high aspect ratio trenches to be manufactured with standard processes.
3Reliability
If deep trenches with high aspect ratio are etched to improve optical isolation, then signal-to-noise ratio increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary actions to prepare for the high aspect ratio trench etching by forming stress management layers and liner structures before the etching process. These preliminary structures provide mechanical support and stress distribution that enable the etching process to achieve the required precision and depth without compromising substrate integrity.
Solution Approach 2:
The patent utilizes parameter changes in the form of stress management through thermally expanded dielectric materials. By controlling the thermal and mechanical parameters of the liner layers and filling materials, the patent enables the formation of high aspect ratio trenches with precise dimensions while managing the mechanical stresses that would otherwise prevent such deep structures from being manufactured.
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
Enhances pixel performance by increasing SNR, allowing higher densities and dynamic range capabilities through reduced optical penalties and simplified structure complexity.
Implementation Method 1
growing an epitaxial layer on surfaces of the trench to form a homogeneous passivation region as part of the substrate material
Implementation Method 2
performing a charge diffusion process to embed the additional dopant into the substrate material
Implementation Method 3
filling the trench with an optically reflective material
Data Source
AI summary
Methods for forming a deep trench isolation (DTI) structure with only two interfaces. In some embodiments, a method of forming a deep trench isolation structure may include etching a trench with a high aspect ratio into a substrate material, repairing the surfaces of the trench from damage caused by etching of the trench, growing an epitaxial layer on the surfaces of the trench to form a homogeneous passivation region as part of the substrate material, doping the epitaxial layer with a dopant to form a passivation charge region, performing a charge diffusion process to embed the dopant into the substrate material, forming a conformal liner layer on the homogeneous passivation region in the trench, and filling the trench with an optically reflective material.