On-Chip RF Shield with Backside Redistribution Lines
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Solution Overview
Problem
The integration of multiple components on a single semiconductor chip leads to interference from electromagnetic radiation emitted by RF circuitry, which worsens with increasing operating frequencies, posing a challenge to eliminate such interference without significant increases in production costs.
Innovation Solution
The implementation of a conductive shield with backside redistribution lines formed on the chip to enclose RF components, minimizing electromagnetic radiation interference by integrating the RF shield on-chip rather than using separate shielding layers, and optimizing the design of these lines to maximize shielding effectiveness while sharing manufacturing steps with existing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple components are integrated on a single chip, then device functionality and density are improved, but electromagnetic interference between components increases
Solution Approach 1:
The chip is divided into distinct RF and non-RF regions separated by conductive shields. The shields segment the electromagnetic environment, confining RF emissions to specific zones and preventing interference with other components. This segmentation allows multiple functional blocks to coexist on the same chip without mutual interference.
Solution Approach 2:
Conductive shields serve as intermediary structures between RF and non-RF components. These shields act as electromagnetic barriers that mediate the interaction between different functional blocks, blocking harmful electromagnetic fields while allowing the system to maintain high integration. The shields are strategically positioned at interfaces between different functional regions.
2Object-affected harmful factors
If separate shielding layers are used to eliminate interference, then electromagnetic interference is reduced, but production costs increase significantly
Solution Approach 1:
The shielding function is merged with the existing interconnect structure by using the same conductive material layers and fabrication processes that are already part of the CMOS manufacturing flow. The shields are formed using standard metal deposition and patterning steps that are integrated into the existing process, eliminating the need for separate shielding fabrication lines and reducing additional production costs.
Solution Approach 2:
The conductive shields serve multiple functions: they provide electromagnetic shielding, act as ground references for RF circuits, and can be used for signal routing. By making the shields multi-functional, the design eliminates the need for dedicated shielding structures that would add complexity and cost to the manufacturing process.
3Speed
If operating frequencies are increased, then device performance is improved, but electromagnetic radiation interference worsens
Solution Approach 1:
The shielding design uses local quality variations by adjusting the conductivity, thickness, and geometry of shield structures in different regions of the chip. RF regions with higher operating frequencies are provided with enhanced shielding compared to lower frequency regions. The shields are locally optimized to match the specific frequency and power characteristics of each RF block, providing effective suppression without over-engineering the entire chip.
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 electromagnetic interference between RF and other components on the chip without increasing production costs, allowing for efficient coexistence of analog, RF, digital, and memory blocks on the same chip while maintaining immunity to noise.
Implementation Method 1
forming a conductive shield with backside redistribution lines that encloses RF components, minimizing electromagnetic radiation interference
Data Source
AI summary
Structures of a system on chip and methods of forming a system on chip are disclosed. In one embodiment, a method of fabricating the system on chip includes forming a through substrate opening from a back surface of a substrate, the through substrate opening disposed between a first and a second region, the first region comprising devices for RF circuitry and the second region comprising devices for other circuitry. The method further includes forming patterns for redistribution lines on a photo resist layer, the photo resist layer disposed under the back surface, and filling the through substrate opening and the patterns for redistribution lines with a conductive material.