Backside Illuminated CMOS Image Sensor Stacked Substrate Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current solid-state imaging devices face challenges in separately obtaining visible light and infrared light due to the lack of circuits between substrates and the thinness of the silicon layer in backside illumination type CMOS image sensors, which impedes effective infrared light reception.
Innovation Solution
A solid-state imaging device is designed with a silicon substrate for visible light conversion and a lower substrate, formed of a compound semiconductor, to photoelectrically convert infrared light from the back surface side, featuring an infrared electrode and reading circuits that overlap to facilitate simultaneous and separate capture of visible and infrared light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a substrate for infrared light reception is affixed to a back surface of a solid-state imaging element, then infrared light can be obtained, but it is difficult to separately obtain visible light and infrared light since there is no circuit between two substrates
Solution Approach 1:
The device is divided into two separate substrates: a first substrate for visible light photoelectric conversion and a second substrate for infrared light photoelectric conversion. Each substrate has its own independent photoelectric conversion units and reading circuits, allowing separate detection of visible and infrared light while maintaining functional independence.
Solution Approach 2:
The patent transitions from a single-substrate planar structure to a multi-substrate three-dimensional stacked structure. The first and second substrates are positioned at different spatial levels, with the second substrate arranged on the light-receiving surface side of the first substrate, enabling spectral separation through spatial dimensionality.
2Measurement precision
If the Si layer is made thin in backside illumination type CIS, then visible light can be obtained, but it is difficult to obtain infrared light
Solution Approach 1:
The photoelectric conversion function is segmented across two substrates: the first substrate (with thin Si layer) is optimized for visible light detection, while the second substrate (with different material or thickness) is optimized for infrared light detection. This segmentation allows each substrate to be independently optimized for its specific wavelength range.
Solution Approach 2:
Different regions of the imaging device are assigned different properties: the first substrate has a thin Si layer structure suitable for visible light, while the second substrate has structural characteristics (material composition, layer thickness) specifically tailored for infrared light transmission and detection.
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 configuration enables the effective and separate capture of visible and infrared light, enhancing the imaging device's capability to handle both spectrums without the limitations of existing technologies.
Implementation Method 1
a photoelectric conversion unit that photoelectrically converts visible light incident from a back surface side
Implementation Method 2
a lower substrate provided under the Si substrate and configured to photoelectrically convert infrared light incident from the back surface side
Data Source
AI summary
A solid-state imaging device includes an Si substrate in which a photoelectric conversion unit that photoelectrically converts visible light incident from a back surface side is formed, and a lower substrate provided under the Si substrate and configured to photoelectrically convert infrared light incident from the back surface side.