Imaging Sensor Insulating Film Layout for Stable Spectral Sensitivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state imaging devices face variations in sensitivity across a wide wavelength region from ultraviolet to near infrared due to the thickness changes of insulating films on uneven semiconductor substrates, requiring additional measures to stabilize sensitivity.
Innovation Solution
A solid-state imaging device with a semiconductor substrate featuring a main surface with multiple photosensitive regions and an insulating film of 0.5 μm or more thickness, where the insulating film's opposite surface is flat and has bottom surfaces of varying depths, causing interferences that cancel out spectral sensitivity variations across different wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulating film is made thick (about 1 μm) to fully exhibit protective function against ultraviolet light, then protection against ultraviolet deterioration is improved, but interference of incident light occurs between the upper surface of the insulating film and the main surface of the semiconductor substrate, causing spectral sensitivity to vary periodically with wavelength
Solution Approach 1:
The invention applies local quality by creating multiple types of bottom surfaces with different depths in the photosensitive regions. This causes light to travel different optical path lengths through the insulating film, generating multiple interference patterns with different periods that cancel each other out, thereby stabilizing spectral sensitivity across the wavelength range while maintaining the thick insulating film for UV protection.
Solution Approach 2:
The invention changes the physical parameter of the insulating film thickness to be 0.5 μm or more, which is sufficient for UV protection. By combining this with the creation of bottom surfaces at different depths, the patent achieves both adequate protective function and reduced spectral sensitivity variation without requiring the full 1 μm thickness that would cause severe interference effects.
2Manufacturing precision
If the main surface is formed in a corrugated shape with recessed and projection shapes to reduce spectral sensitivity variation, then spectral sensitivity stability is improved, but the film thickness of the insulating film changes according to the uneven shape, requiring additional measures for wide wavelength region stability
Solution Approach 1:
Instead of making the insulating film surface uneven to control interference, the invention inverts the approach by keeping the upper surface flat and creating the depth variations at the bottom surfaces. This inversion allows the insulating film thickness to be controlled from the bottom up, achieving interference cancellation while maintaining a flat top surface that simplifies subsequent processing.
3Manufacturing precision
If multiple types of bottom surfaces with different depths are provided to cancel interference periods, then sensitivity variation in wide wavelength region is reduced, but the complexity of substrate structure increases
Solution Approach 1:
The invention segments the bottom surfaces into multiple types with different depths, where each segment creates a specific interference pattern. By arranging these segmented bottom surfaces in the photosensitive regions, the patent achieves cancellation of interference periods across the wide wavelength range, reducing sensitivity variation while managing structural complexity through systematic segmentation.
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 reduces sensitivity variations across the wide wavelength region by ensuring the insulating film's flatness and sufficient thickness, effectively stabilizing the device's performance.
Implementation Method 1
when incident light is incident on the photosensitive regions, a plurality of interferences having different optical path lengths occur between the surface of the insulating film on the side opposite to the main surface and each of the bottom surfaces on the main surface of the semiconductor substrate
Data Source
AI summary
A solid-state imaging device according to the disclosure includes a semiconductor substrate which has a main surface having a plurality of photosensitive regions, and an insulating film which is provided on the main surface of the semiconductor substrate. When the main surface of the semiconductor substrate is taken as a reference surface, a thickness of the insulating film from the reference surface is 0.5 μm or more, a surface (a main surface) of the insulating film on the side opposite to the main surface is a surface having flatness, and a plurality of types of bottom surfaces of which depths from the reference surface are different from each other are provided on the main surface of the semiconductor substrate in the photosensitive regions.