Conductive Blocking Structure for Stacked Image Sensor Radiation Shielding
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Solution Overview
Problem
Stacked image sensors in CMOS substrates generate radiation during operation, which can induce unwanted current in image sensing elements, degrading their performance due to hot electron-induced electron-hole pair recombination and light emission.
Innovation Solution
A conductive blocking structure is integrated within the hybrid bonding interface region between the semiconductor devices and image sensing elements, electrically coupling the dies while laterally extending to block radiation, thereby preventing it from reaching the image sensing elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stacked image sensors are integrated in CMOS substrates, then device functionality and data processing capability are improved, but radiation-induced unwanted current in image sensing elements increases
Solution Approach 1:
A conductive blocking structure is introduced as an intermediary element between the CMOS substrate and the image sensing elements. This structure serves as a mediator that blocks radiation (hot electrons and light) from reaching the image sensing elements while allowing the stacked configuration to maintain its data processing functionality. The conductive blocking structure is electrically coupled to ground potential, enabling it to intercept and divert radiation-induced charges away from the sensitive photodetectors.
Solution Approach 2:
The harmful radiation path is extracted and blocked by removing the direct line of sight between the radiation source (CMOS substrate) and the image sensing elements. The conductive blocking structure is positioned to laterally extend and intercept radiation before it can reach the photodetectors, effectively taking out the harmful interaction from the system.
2Reliability
If a conductive blocking structure is added to block radiation, then image sensing element performance is improved, but device complexity increases
Solution Approach 1:
The conductive blocking structure serves multiple functions simultaneously: it blocks radiation (hot electrons and light) from reaching the image sensing elements, provides an electrical ground reference, and can be integrated into existing CMOS fabrication processes. By combining radiation blocking and electrical grounding functions in a single structure, the design avoids adding separate components for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The radiation blocking function and electrical grounding function are merged into a single conductive blocking structure. This structure is electrically coupled to ground potential and positioned to laterally extend between the CMOS substrate and image sensing elements, combining what could have been separate components into one integrated element.
3Object-affected harmful factors
If radiation is blocked laterally between dies, then unwanted current generation is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The conductive blocking structure is formed during the CMOS substrate fabrication process before the image sensing elements are assembled onto the substrate. By preparing the blocking structure in advance as part of the substrate processing, the alignment and positioning are established during a controlled fabrication step rather than during the later assembly process, reducing the precision requirements for the final bonding operation.
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 conductive blocking structure effectively prevents unwanted current generation in image sensing elements, enhancing the performance of stacked image sensors by isolating radiation-induced noise.
Implementation Method 1
A conductive blocking structure is integrated within the hybrid bonding interface region between the semiconductor devices and image sensing elements, electrically coupling the dies while laterally extending to block radiation, thereby preventing it from reaching the image sensing elements.
Implementation Method 2
Both types of devices work according to the photoelectric effect, in which incident radiation is converted to an electrical signal.
Data Source
AI summary
In some embodiments, the present disclosure relates to a method of forming an integrated chip (IC) structure. The method may be performed by forming a first integrated chip die having one or more semiconductor devices within a first substrate, and forming a passivation layer over the first integrated chip die. The passivation layer is selectively etched to form interior sidewalls defining a first opening, and a conductive material is deposited over the passivation layer and within the first opening. The conductive material is patterned to define a conductive blocking structure that laterally extends past the one or more semiconductor devices in opposing directions. The first integrated chip die is bonded to a second integrated chip die having an array of image sensing elements within a second substrate.