Package Substrate Embedded Noise Shielding Walls
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Solution Overview
Problem
As semiconductor package technology advances, compact signal lines experience significant cross-talk noise due to the lack of noise shielding mechanisms in conventional chip packages.
Innovation Solution
The integration of noise shielding walls, where at least one signal line is sandwiched between two shielding walls, which are electrically coupled to ground, is implemented using a process involving etching and metal filling in dielectric layers to form trenches and subsequently filling them with metal to create the shielding walls and signal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If signal lines are made compact to increase integration density, then productivity and area utilization are improved, but cross-talk noise increases due to lack of shielding
Solution Approach 1:
Grounded shielding walls are introduced as intermediary structures between adjacent signal lines. These shielding walls act as mediators that intercept and redirect electromagnetic fields to ground, preventing direct coupling between signal lines and thereby reducing cross-talk noise while allowing compact signal line spacing
Solution Approach 2:
The shielding structure extends vertically into the substrate, utilizing the third dimension (depth) to provide noise isolation. By etching trenches to a specific depth and filling them with conductive material, the shielding effect is achieved without increasing the lateral footprint, thus maintaining high integration density while adding noise protection
2Reliability
If shielding walls are added to reduce cross-talk noise, then reliability is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The formation of shielding walls is merged with existing signal line fabrication steps. Both signal lines and shielding walls are created using the same etching and metal filling processes, allowing simultaneous formation of multiple conductive structures in a single fabrication sequence, thereby reducing overall process complexity
Solution Approach 2:
The shielding structure is segmented into discrete walls positioned at specific locations between signal lines, rather than implementing a continuous ground plane. This segmentation allows selective shielding where cross-talk is most problematic, reducing the total amount of conductive material and structural complexity while maintaining signal integrity
3Reliability
If shielding walls are added to reduce cross-talk noise, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The positions of shielding walls are predetermined during the pattern design phase, with trenches etched at specific locations between signal lines. This preliminary positioning allows the use of standard photolithography and etching processes with conventional precision requirements, as the shielding wall locations are established before metal filling and grounding connections are made
Data Source
AI summary
A package substrate with embedded noise shielding walls is disclosed. One of the embodiment comprises a signal line S sandwiched by a left shielding wall W1 and a right shielding wall W2. The signal line S, left shielding wall W1, and the right shielding wall W2 are embedded in a dielectric layer.