Image Sensor Pixel Structure With Strained Germanium for IR Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The miniaturization of electronic components in image sensor devices has reduced pixel size, making it challenging to improve light absorption efficiency, particularly for infrared radiation.
Innovation Solution
The use of semiconductor materials with direct band gaps, such as germanium, is enhanced by applying biaxial tensile stress through an annealing process, transforming the indirect band gap of germanium in a silicon substrate to a direct band gap, thereby improving infrared radiation absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If pixel size is reduced for miniaturization, then device integration is improved, but light absorption efficiency deteriorates
Solution Approach 1:
The patent applies parameter changes by transforming the band gap structure of germanium from indirect to direct through biaxial tensile stress induced by annealing. This fundamental change in the material's optical properties enables efficient light absorption in miniaturized pixels, resolving the contradiction between reduced pixel size and maintained absorption efficiency.
Solution Approach 2:
The patent employs composite materials by forming strained silicon-germanium heteroepitaxial layers that combine silicon substrate with germanium layers under tensile stress. This composite structure achieves both miniaturization and enhanced light absorption by leveraging the complementary properties of the two materials.
2Use of energy by moving object
If germanium is used to absorb infrared radiation, then infrared absorption is improved, but threading dislocations increase
Solution Approach 1:
The patent changes the stress state parameter of germanium from unstressed to biaxially tensile stressed through controlled annealing. This parameter change transforms the band gap type while simultaneously reducing threading dislocations, achieving both improved infrared absorption and enhanced reliability.
Solution Approach 2:
The patent utilizes thermal expansion effects during the annealing process to induce biaxial tensile stress in the germanium layers. By controlling the thermal history, the process transforms the indirect band gap to direct band gap and reduces dislocation density, resolving the contradiction between absorption efficiency and reliability.
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 significantly enhances the absorption of infrared radiation, improving the overall light absorption efficiency of image sensor devices by forming strained silicon-germanium heteroepitaxial layers, which reduces threading dislocations and increases the absorption of low-energy photons.
Implementation Method 1
applying biaxial tensile stress through an annealing process, transforming the indirect band gap of germanium in a silicon substrate to a direct band gap
Implementation Method 2
applying biaxial tensile stress through an annealing process
Implementation Method 3
transforming the indirect band gap of germanium in a silicon substrate to a direct band gap, thereby improving infrared radiation absorption efficiency
Implementation Method 4
forming strained silicon-germanium heteroepitaxial layers
Data Source
AI summary
An image sensor device includes a semiconductor substrate, a radiation sensing member, a device layer, and a color filter layer. The semiconductor substrate has a photosensitive region and an isolation region surrounding the photosensitive region. The radiation sensing member is embedded in the photosensitive region of the semiconductor substrate. The radiation sensing member has a material different from a material of the semiconductor substrate, and an interface between the radiation sensing member and the isolation region of the semiconductor substrate includes a direct band gap material. The device layer is under the semiconductor substrate and the radiation sensing member. The color filter layer is over the radiation sensing member and the semiconductor substrate.