IC Bonding Shield Layout for Conductive Pad Crosstalk
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Solution Overview
Problem
Digital image sensors face challenges in increasing resolution and image quality due to mutual inductance and capacitance between conductive pads, which lead to crosstalk and reduced image quality as they are scaled down.
Innovation Solution
The implementation of a metal-to-metal (M-M) and dielectric-to-dielectric (D-D) bonding layer with shield structures, including shield lines and dummy pads, to separate conductive pads and reduce electromagnetic interference, thereby minimizing mutual inductance and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conductive pads are scaled down to increase resolution, then pixel density and resolution are improved, but mutual inductance and capacitance between pads increase causing crosstalk
Solution Approach 1:
A shield structure is introduced as an intermediary element between adjacent conductive pads. The shield comprises a first shield region connected to a first conductive pad and a second shield region connected to a second conductive pad, with a dielectric layer between the shield regions. This intermediary shield structure reduces mutual inductance and capacitance between the pads, thereby minimizing crosstalk while allowing the pads to be closely spaced for high resolution.
Solution Approach 2:
The shield structure is segmented into distinct regions: a first shield region, a second shield region, and an intermediate dielectric region. This segmentation allows the shield to be electrically connected to different pads while maintaining electrical isolation between adjacent pads through the dielectric layer, effectively reducing electromagnetic interference without requiring large pad spacing.
2Reliability
If shield structures are added to reduce crosstalk, then image quality is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The shield structure is merged with the existing bonding layer architecture. The shield is formed within the bonding layer between the first and second IC chips, utilizing the same bonding process flow. The first and second shield regions are integrated into the bonding layer along with the dielectric layer, allowing the shield function to be achieved without adding separate manufacturing steps outside the standard bonding process.
Solution Approach 2:
The bonding layer serves multiple functions: it provides mechanical bonding between chips, electrical connection through conductive pads, and electromagnetic shielding through the integrated shield structure. The dielectric layer within the bonding layer simultaneously provides electrical isolation for the shield and structural support for the bonding interface, reducing the need for additional dedicated shielding components.
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 solution enhances image quality by reducing crosstalk and interference between conductive pads, allowing for higher resolution and improved image acquisition without compromising pixel size.
Implementation Method 1
mutual inductance and capacitance between conductive pads, which lead to crosstalk and reduced image quality
Implementation Method 2
mutual inductance and capacitance between conductive pads
Data Source
AI summary
Some embodiments relate to an IC device, including a first chip; and a second chip bonded to the first chip at a bonding interface; where the first and second chips respectively comprise a first dielectric layer and a second dielectric layer directly contacting; the first chip further comprises a plurality of conductive pads recessed into the first dielectric layer and in a plurality of rows and columns; where the plurality of conductive pads are arranged with a zig-zag layout along the plurality of columns and along the plurality of rows and comprise a first conductive pad and a second conductive pad; the first chip further comprises a first shield line in the first dielectric layer and laterally between the first and second conductive pads, and the second chip further comprises a contact recessed into the second dielectric layer and directly contacting the first conductive pad at the bonding interface.