Image Sensor Light Transmitter Mitigates Plasma Damage
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Solution Overview
Problem
Existing image sensor manufacturing processes using plasma dry etching result in plasma damage, increasing dark current and deteriorating sensor characteristics due to light reflection and dispersion by interlayer and inter-metal insulating films.
Innovation Solution
A method involving forming a photoelectric converter on a semiconductor substrate, covering it with an interlayer insulating film, creating openings above the converter by removing parts of the insulating films, curing the surface with light to mitigate plasma damage, and filling these openings with a light transmitter to enhance light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plasma dry etching is used to remove interlayer insulating film and etch stop film, then openings can be formed above photoelectric converter, but plasma damage occurs causing increased dark current and deteriorated sensor characteristics
Solution Approach 1:
A light transmitter material is introduced as an intermediary substance to fill the openings after etching. This material serves multiple functions: it protects the photoelectric converter from plasma damage during subsequent processing, reduces dark current by passivating surface states, and maintains the structural integrity of the opening region. The light transmitter acts as a mediator between the etching process and the sensitive photoelectric converter.
Solution Approach 2:
The patent converts the harmful plasma damage into a beneficial process by using controlled plasma etching to form openings, then immediately filling them with light transmitter material. The previously harmful plasma-exposed surfaces are transformed into beneficial interfaces where the light transmitter material passivates surface states, actually reducing dark current. The harm of plasma exposure is converted into a controlled surface preparation step.
2Reliability
If interlayer insulating film and inter-metal insulating film are layered above photoelectric converter, then structural integrity and electrical isolation are maintained, but light reflection and dispersion occur reducing light reception quantity
Solution Approach 1:
The insulating film structure is segmented into distinct functional zones: interlayer insulating film in regions requiring electrical isolation, and light transmitter material in regions requiring light transmission. This segmentation allows each material to perform its optimal function without compromising the other, enabling simultaneous maintenance of structural integrity and maximization of light reception.
Solution Approach 2:
Different materials with different optical properties are applied to different locations above the photoelectric converter. Light transmitter material with high optical transparency is placed specifically above the photoelectric converter where light reception is critical, while insulating films are maintained in regions where electrical isolation is the primary concern. This local differentiation of material properties optimizes both light reception and structural functionality.
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 reduces dark current and improves image sensor characteristics by minimizing plasma damage and optimizing light transmission, thereby enhancing sensitivity and overall performance.
Implementation Method 1
a unit pixel may photoelectrically convert incident light and may accumulate electric charge corresponding to the quantity of the light in a photoelectric converter
Implementation Method 2
curing the surface above the photoelectric converter by irradiating light to the openings
Data Source
AI summary
Example embodiments may provide methods of manufacturing an image sensor. Example methods of manufacturing an image sensor may include forming a photoelectric converter in a semiconductor substrate, forming an interlayer insulating film covering a surface of the semiconductor substrate, forming metal wires and an inter-metal insulating film filling between the metal wires on the interlayer insulating film, forming openings above the photoelectric converter by removing a part of the inter-metal insulating film and the interlayer insulating film, curing the surface above the photoelectric converter by irradiating light into the openings, and/or forming a light transmitter filling the openings.