Back-illuminated Image Sensor Wiring Coverage for Light Interference
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Solution Overview
Problem
Conventional back-illuminated solid-state image pickup apparatuses face issues with light interference from the front surface and side surfaces due to the multilayered wiring layer, leading to reduced focusing properties and increased noise in image capture, particularly when mounted on thin flexible substrates in devices like mobile phones.
Innovation Solution
A solid-state image pickup apparatus with a multilayered wiring layer where the wiring coverage reaches 100% at least in the image pickup pixel unit, and the distance between adjacent wirings is less than the shortest wavelength of ultraviolet light, combined with a light-shielding film to prevent oblique light from entering the photoelectric conversion element, effectively shielding unnecessary light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a back-illuminated type solid-state image pickup apparatus is used with a thinned silicon substrate to improve light receiving efficiency, then light receiving efficiency is improved, but light from the front surface and side surfaces enters the photoelectric conversion element causing noise and reduced focusing properties
Solution Approach 1:
A light-shielding film is introduced as an intermediary layer between the front surface and the photoelectric conversion element. This film selectively blocks harmful light from the front and side surfaces while allowing necessary light to reach the photoelectric conversion element, thus resolving the contradiction between maintaining light receiving efficiency and preventing light interference.
Solution Approach 2:
The light-shielding film is applied selectively to specific regions where light interference occurs (front surface and side surfaces) rather than uniformly across the entire device. This localized approach prevents harmful light while maintaining optimal light receiving properties in the active photoelectric conversion regions.
2Ease of manufacture
If a multilayered wiring layer is formed on the front surface of the silicon substrate, then electrical functionality is achieved, but the wiring layer causes light reflection and interference that degrades image quality
Solution Approach 1:
The light-shielding film serves as a mediator placed between the incoming light and the multilayered wiring layer. It prevents light from reflecting off the wiring layer structures, thereby eliminating the degradation of image quality while preserving the necessary electrical functionality of the wiring layer.
3Use of energy by moving object
If the silicon substrate is thinned to 5-10 micrometers to improve light transmission, then light transmission is improved, but light is not attenuated sufficiently and causes pickup of unwanted light
Solution Approach 1:
The light-shielding film acts as a mediator that compensates for the insufficient light attenuation caused by the thinned substrate. It provides the additional blocking function needed to prevent unwanted light pickup while maintaining the high light transmission properties enabled by the thinned substrate design.
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 significantly reduces light interference and noise, enhancing the focusing properties and image quality by ensuring that all necessary light is captured from the intended source while preventing unwanted light from entering the photoelectric conversion element.
Implementation Method 1
a wiring in each of the wiring layers constituting the multilayered wiring layer is disposed so that a coverage of the wiring located at least in the image pickup pixel unit of the semiconductor substrate reaches 100%, viewed from a second surface side
Data Source
AI summary
A solid-state image pickup apparatus includes an image pickup pixel unit in which a plurality of pixels each including a photoelectric conversion element and a field-effect transistor are arranged on a semiconductor substrate so that a light-receiving surface is disposed at a first surface side of the semiconductor substrate; a peripheral circuit unit provided at a periphery of the image pickup pixel unit of the semiconductor substrate; and a multilayered wiring layer in which a plurality of wiring layers for driving the field-effect transistor of the image pickup pixel unit are laminated at a second surface side of the semiconductor substrate, wherein a wiring in each of the wiring layers constituting the multilayered wiring layer is disposed so that a coverage of the wiring located at least in the image pickup pixel unit of the semiconductor substrate reaches 100%, viewed from the second surface side.