Image Sensor Pixel Structure With Direct Band Gap Infrared Absorption
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Solution Overview
Problem
The challenge in image sensor devices is to enhance light absorption efficiency, particularly for infrared radiation, as pixel sizes continue to miniaturize.
Innovation Solution
The solution involves forming radiation sensing members from semiconductor materials with direct band gaps and low optical band gap energies, such as germanium on a silicon substrate, and applying a biaxial tensile stress through an annealing process to transform the indirect band gap of germanium into a direct band gap, thereby improving infrared radiation absorption.
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 changes the optical band gap parameter of the semiconductor material by applying biaxial tensile stress through annealing, transforming germanium from indirect band gap to direct band gap. This parameter change enables efficient infrared radiation absorption even in miniaturized pixels, resolving the contradiction between small pixel size and light absorption efficiency.
Solution Approach 2:
The patent uses a composite structure combining silicon substrate with germanium radiation sensing members. The germanium layer is specifically engineered with direct band gap properties through stress-induced transformation, creating a material composite that maintains high infrared absorption efficiency in reduced pixel dimensions.
2Ease of manufacture
If germanium indirect band gap is used, then material availability is improved, but infrared radiation absorption efficiency deteriorates
Solution Approach 1:
The patent transforms the fundamental optical parameter of germanium by applying biaxial tensile stress during annealing, converting it from indirect band gap to direct band gap. This enables the widely available germanium material to efficiently absorb infrared radiation, resolving the contradiction between material availability and absorption efficiency.
Solution Approach 2:
The patent utilizes thermal annealing process that induces biaxial tensile stress in the germanium layer, causing lattice expansion and transformation from indirect to direct band gap. This thermal processing method maintains material availability while dramatically improving infrared absorption efficiency.
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 infrared radiation absorption efficiency of image sensor devices, even with reduced pixel sizes, by converting the indirect band gap of germanium to a direct band gap under biaxial tensile stress.
Implementation Method 1
applying a biaxial tensile stress through an annealing process to transform the indirect band gap of germanium into a direct band gap
Implementation Method 2
applying a biaxial tensile stress through an annealing process to transform the indirect band gap of germanium into a direct band gap
Implementation Method 3
radiation sensing members formed from a semiconductor material with a direct band gap... converting the indirect band gap of germanium to a direct band gap
Data Source
AI summary
An image sensor device includes a semiconductor substrate, a radiation sensing member, a shallow trench isolation, and a color filter layer. The radiation sensing member is in the semiconductor substrate. An interface between the radiation sensing member and the semiconductor substrate includes a direct band gap material. The shallow trench isolation is in the semiconductor substrate and surrounds the radiation sensing member. The color filter layer covers the radiation sensing member.