Backside Interconnect Light Shielding for Solid State Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The backside electrode structure of solid state imaging devices experiences light incidence issues due to the gap between the imaging device and circuit substrates, affecting yield and cost, despite previous attempts to mitigate this with light shielding layers and antireflective films.
Innovation Solution
A solid state imaging device with a backside interconnect electrode and a light shielding layer provided coplanar with or on the circuit substrate side of the interconnect electrode, which effectively shields light from the backside, maintaining electrical connectivity and preventing capacitive coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a backside electrode structure is used to downsize the solid state imaging device, then the device size is reduced, but light enters through the gap between substrates and causes backside light incidence
Solution Approach 1:
The patent applies local quality by providing light shielding layers at specific locations where light incidence occurs (around the imaging device section and in the gap region) rather than covering the entire backside. This targeted approach blocks harmful light while maintaining the downsized form factor and electrical connectivity functions.
Solution Approach 2:
The patent introduces light shielding layers as intermediary elements between the imaging device section and the incoming light from the gap. These shielding layers act as mediators that block light paths without interfering with the electrical connection through solder balls, thus resolving the contradiction between miniaturization and light shielding.
2Object-affected harmful factors
If a light shielding layer is provided entirely on the backside to prevent backside light incidence, then light shielding is improved, but the device size cannot be further reduced
Solution Approach 1:
Instead of providing light shielding layers across the entire backside surface, the patent applies them locally only in regions where light incidence is problematic (peripheral regions and gap areas). This localized shielding approach prevents backside light incidence while preserving device miniaturization.
Solution Approach 2:
The light shielding function is segmented into multiple discrete light shielding layers positioned at different locations (around the imaging device section and in the gap region) rather than using a single continuous layer. This segmentation allows effective light blocking while maintaining compact device dimensions.
3Object-affected harmful factors
If the gap between imaging device and circuit substrates is reduced to prevent light entry, then light shielding is improved, but manufacturing precision requirements increase due to solder ball height variation
Solution Approach 1:
The patent introduces light shielding layers as intermediary elements that fill and shield the gap region between substrates. These shielding layers compensate for solder ball height variations and ensure consistent light blocking performance without requiring tight control of substrate contact precision.
Solution Approach 2:
The light shielding layers are provided in advance to cushion against the harmful effect of light entry through gaps of varying sizes. By pre-positioning these shielding layers, the patent eliminates the need for precise gap control, thereby reducing manufacturing precision requirements.
4Reliability
If wire bonding is used to connect electrodes between substrates, then electrical connectivity is achieved, but the bonding region area is large preventing downsizing
Solution Approach 1:
The patent inverts the traditional connection approach by using flip chip mounting with solder balls on the backside electrode structure, rather than wire bonding from the frontside. This inversion enables compact interconnection and supports device downsizing while maintaining reliable electrical connectivity.
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
The solution significantly reduces backside light incidence, ensuring uniform display and low-cost production by effectively blocking wavelengths that cause issues, while maintaining electrical connectivity and avoiding image defects.
Implementation Method 1
a light shielding layer provided coplanar with the backside interconnect electrode or on the circuit substrate side of the backside interconnect electrode
Data Source
AI summary
A solid state imaging device includes: an imaging device substrate with an imaging device section formed on a first major surface side thereof; a backside interconnect electrode provided on a second major surface side of the imaging device substrate and electrically connected to the imaging device section, the second major surface being on the opposite side of the first major surface; a circuit substrate provided with a circuit substrate electrode opposed to the second major surface; a connecting portion electrically connecting the backside interconnect electrode to the circuit substrate electrode; and a light shielding layer provided coplanar with the backside interconnect electrode or on the circuit substrate side of the backside interconnect electrode.