Shielded RDL Conductive Traces for Lower Crosstalk
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Solution Overview
Problem
Conventional semiconductor packaging technologies face challenges in reducing crosstalk and enhancing signal integrity due to the lack of effective electromagnetic shielding in redistribution layers (RDLs), particularly in wafer level packaging where conductive lines of varying thicknesses are not adequately utilized to shield thinner signal lines.
Innovation Solution
The formation of post-passivation interconnect (PPI) structures with conductive lines of varying thicknesses, where thicker power/ground lines surround thinner signal lines within the same dielectric layer, providing an electromagnetic shielding effect to reduce crosstalk and improve signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RDL structures with uniform thickness conductive lines are used, then manufacturing process is simple, but crosstalk between signal lines increases and signal integrity deteriorates
Solution Approach 1:
The patent applies local quality by creating conductive lines with varying thicknesses within the same RDL layer. Thicker conductive lines are formed for power and ground connections to provide electromagnetic shielding, while thinner lines are used for signal transmission. This local variation in thickness provides targeted shielding where needed without unnecessarily increasing complexity throughout the entire structure, thereby improving signal integrity while maintaining reasonable manufacturing complexity.
Solution Approach 2:
The patent implements the nesting principle by positioning thinner signal-carrying conductive lines within the electromagnetic field shield created by thicker power and ground lines in the same layer. The thicker lines effectively surround or nest the thinner lines, creating a layered shielding configuration that reduces crosstalk while maintaining a compact single-layer structure rather than requiring multiple stacked layers.
2Object-affected harmful factors
If thicker conductive lines are added to provide electromagnetic shielding, then crosstalk is reduced, but manufacturing process complexity increases
Solution Approach 1:
The patent merges multiple functions into a single RDL layer by combining both signal transmission and electromagnetic shielding functions. Thicker conductive lines perform dual roles as both signal/power carriers and electromagnetic shields, while thinner lines handle signal transmission. This consolidation into one layer avoids the need for separate shielding layers, maintaining ease of manufacture through a simplified single-layer process while still achieving crosstalk reduction.
Solution Approach 2:
The patent applies parameter changes by varying the thickness parameter of conductive lines within the same layer based on their functional requirements. Lines requiring shielding are formed with greater thickness, while signal lines use optimal thinner dimensions. This parameter variation is achieved through a single manufacturing process that can control line thickness, thereby reducing crosstalk without significantly complicating the manufacturing process.
3Reliability
If multiple RDL layers are used to provide shielding, then signal integrity improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses the nesting principle to achieve electromagnetic shielding within a single RDL layer by having thicker power and ground lines surround thinner signal lines in the same layer. This nested configuration provides the shielding effect of multiple layers without actually stacking multiple RDL layers, thereby maintaining signal integrity while avoiding the increased complexity and manufacturing difficulty associated with multi-layer structures.
Solution Approach 2:
The patent transitions from a vertical stacking approach (multiple layers) to a horizontal arrangement approach (single layer with varying line thicknesses). By utilizing the planar dimension more effectively with thicker shielding lines positioned adjacent to and surrounding thinner signal lines, the patent achieves three-dimensional shielding effects in a two-dimensional single-layer configuration, reducing both device complexity and manufacturing difficulty.
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 effectively reduces near-end and far-end crosstalk by 3.2 dB and 7.7 dB respectively, enhancing signal integrity through the use of thicker conductive lines as shields for thinner lines within the same device layer.
Implementation Method 1
thicker power/ground lines surround thinner signal lines within the same dielectric layer, providing an electromagnetic shielding effect to reduce crosstalk and improve signal integrity
Data Source
AI summary
A method includes forming a dielectric layer over a contact pad of a device, forming a first polymer layer over the dielectric layer, forming a first conductive line and a first portion of a second conductive line over the first polymer layer, patterning a photoresist to form an opening over the first portion of the second conductive feature, wherein after patterning the photoresist the first conductive line remains covered by photoresist, forming a second portion of the second conductive line in the opening, wherein the second portion of the second conductive line physically contacts the first portion of the second conductive line, and forming a second polymer layer extending completely over the first conductive line and the second portion of the second conductive line.