Shallow Trench Isolation Textures for Thin-Silicon IR Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional silicon-based photodetecting imagers have limited light absorption properties, particularly for infrared light, as silicon is an indirect bandgap semiconductor with low absorption of electromagnetic radiation with wavelengths greater than 1100 nm, requiring thick silicon layers for detection, which increases the thickness and complexity of the imager.
Innovation Solution
The use of optoelectronic devices with a semiconductor layer coupled to a support substrate and an array of shallow trench isolation surface features, which increase the effective optical path length for longer wavelengths by redirecting and absorbing light through textured surface features, allowing for thinner silicon layers and improved absorption of infrared radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick silicon layers are used to improve infrared light absorption, then absorption efficiency is improved, but device thickness and complexity increase
Solution Approach 1:
The patent applies surface texturing with curved features (pyramids, domes, or random curvature) on the silicon surface to increase the optical path length of incident light. This curvature causes multiple internal reflections, allowing photons to traverse the silicon layer multiple times and increase absorption probability without increasing the physical thickness of the silicon layer.
Solution Approach 2:
The patent introduces surface texturing that adds a dimensional aspect to light interaction. By creating three-dimensional surface features, the effective optical path length is extended in the vertical dimension while maintaining the same physical layer thickness, effectively decoupling absorption efficiency from physical thickness.
2Reliability
If traditional planar silicon surfaces are used, then manufacturing is simpler, but light absorption particularly for infrared is limited
Solution Approach 1:
The patent segments the planar silicon surface into multiple discrete textured features (pyramids, domes, or isolated curvature regions). This segmentation approach allows the texturing to be achieved through standard photolithography and etching processes that create patterned features, making the complex surface structure manufacturable using existing semiconductor fabrication techniques.
Solution Approach 2:
The patent replaces complex mechanical surface manipulation with chemical etching processes. By using anisotropic etching with appropriate crystallographic orientations, the desired three-dimensional surface features self-form through chemical reactions, eliminating the need for complex mechanical or lithographic patterning while achieving the required surface texture.
3Device complexity
If silicon layer thickness is reduced to simplify device structure, then device complexity decreases, but absorption depth increases and infrared detection capability is lost
Solution Approach 1:
The patent uses curved surface features to extend the optical path length within the thinned silicon layer. The curvature causes incident light to undergo multiple internal reflections, effectively increasing the distance photons travel through the silicon without increasing the physical layer thickness, thereby maintaining infrared detection capability in thin layers.
Solution Approach 2:
The patent introduces surface texturing as an intermediary mechanism between incident light and the thin silicon layer. This texturing layer acts as a mediator that enhances light-silicon interaction by creating multiple reflection paths, enabling efficient absorption in thinned structures without requiring the light to directly penetrate through thick material.
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 devices achieve enhanced light absorption across a broader spectrum, including infrared, with reduced absorption depth and increased response speed, enabling detection of longer wavelengths in thinner silicon layers, and improved sensitivity and noise reduction in both front-side and back-side illuminated configurations.
Implementation Method 1
an array of shallow trench isolation surface features positioned between the semiconductor layer and the support substrate, the surface features positioned to interact with electromagnetic radiation that passes through the semiconductor layer
Data Source
AI summary
Photosensitive devices and associated methods are provided. In one aspect, for example, a photosensitive imager device can include a semiconductor layer having multiple doped regions forming a least one junction, a textured region coupled to the semiconductor layer and positioned to interact with electromagnetic radiation. The textured region can be formed from a series of shallow trench isolation features.