3D CMOS Image Sensor Infrared Absorption via Reflective Films
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Solution Overview
Problem
Conventional CMOS image sensors face challenges in manufacturing 3D infrared-ray sensing elements due to defects like dangling bonds at the interface between the substrate and epitaxial film, leading to deteriorated electrical characteristics, and require complex processes that increase production costs and reduce mass production efficiency.
Innovation Solution
A CMOS image sensor design featuring a substrate with a light receiving surface and strategically positioned light reflecting films to redirect infrared rays, along with electrodes responsive to periodic signals, which allows for efficient collection of charge carriers and simplifies the manufacturing process by using a conventional CMOS process with a thin epitaxial film thickness of 3 to 4 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick epitaxial film is used to improve infrared ray absorption, then sensitivity is improved, but manufacturing defects like dangling bonds increase and electrical characteristics deteriorate
Solution Approach 1:
The patent changes the thickness parameter of the epitaxial film from conventional thick structures to a thin film structure with a thickness of 3 to 4 μm. This parameter change reduces manufacturing defects such as dangling bonds at the interface between the substrate and epitaxial film, thereby improving electrical characteristics while maintaining sufficient infrared ray absorption through the light reflecting film structure.
2Reliability
If complex manufacturing processes are used to improve sensing element performance, then device performance is improved, but production cost increases and mass production efficiency decreases
Solution Approach 1:
The patent applies conventional CMOS manufacturing processes to fabricate the 3D infrared-ray sensing element, making the process universal and compatible with standard industrial production lines. This eliminates the need for specialized complex processes, thereby improving mass production efficiency and reducing production costs while maintaining sensing element performance through the optimized thin epitaxial film and light reflecting film structure.
3Productivity
If conventional CMOS process with thin epitaxial film is used to improve manufacturing efficiency, then productivity is improved, but infrared ray absorption may be insufficient
Solution Approach 1:
The patent transitions from a conventional single-layer thick epitaxial film structure to a multi-dimensional structure comprising a thin epitaxial film (3 to 4 μm) combined with light reflecting films positioned at specific depths. This dimensional restructuring enables sufficient infrared ray absorption through multiple reflections within the thin film, maintaining productivity benefits while achieving adequate sensing performance.
Solution Approach 2:
The light reflecting film acts as an intermediary element that enhances infrared ray absorption in the thin epitaxial film. By positioning the light reflecting film at a specific depth within the substrate, it redirects infrared rays multiple times through the thin epitaxial film, effectively increasing absorption path length and improving sensing capability without requiring a thick epitaxial film structure.
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 design enhances the electrical characteristics of the 3D CMOS image sensor by reducing defects and enabling mass production using standard processes, while effectively collecting infrared data for 3D image generation.
Implementation Method 1
a first light reflecting film extending within the substrate. The first light reflecting film is configured to redirect light incident thereon towards the light receiving surface. A second light reflecting film is also provided on the light receiving surface. The second light reflecting film is configured to redirect reflected light received from the first light reflecting film towards the first light reflecting film
Implementation Method 2
The semiconductor-type thermal infrared-ray sensing element includes a material having a low band gap, and thus, when thermal infrared-rays are incident thereto, electrons and holes are excited by the thermal infrared-rays
Data Source
AI summary
A three-dimensional (3D) CMOS image sensor (CIS) that sufficiently absorbs incident infrared-rays (IRs) and includes an infrared-ray (IR) receiving unit formed in a thin epitaxial film, thereby being easily manufactured using a conventional CIS process, a sensor system including the 3D CIS, and a method of manufacturing the 3D CIS, the 3D CIS including an IR receiving part absorbing IRs incident thereto by repetitive reflection to produce electron-hole pairs (EHPs); and an electrode part formed on the IR receiving part and collecting electrons produced by applying a predetermined voltage thereto.