Multi-Trace Spiral Inductor for High Q Value RF Circuits
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Solution Overview
Problem
Conventional on-chip inductors in semiconductor integrated circuits have a reduced quality factor (Q value) due to thinner inductor traces, which affects their performance in RF circuits, necessitating the development of an on-chip inductor with an increased Q value without increasing process complexity or manufacturing yield.
Innovation Solution
A spiral inductor with a multi-trace structure is designed, featuring a spiral conductive trace with multiple turns and additional single-turn traces connected in parallel to the outermost or innermost turns, which are grounded, reducing parasitic capacitance and increasing inductive coupling, thereby enhancing the Q value without increasing trace thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the inductor trace thickness is reduced to accommodate digital/baseband circuit processes, then more functions can be integrated on a single chip, but the quality factor (Q value) of the inductor decreases
Solution Approach 1:
The inductor structure is segmented into multiple parallel traces instead of a single thick trace. This segmentation allows the use of thinner traces compatible with digital circuit processes while maintaining the overall inductance and improving the Q value through reduced parasitic effects
Solution Approach 2:
Multiple thin traces are combined in parallel to form the complete inductor structure. This merging of multiple thin traces achieves the equivalent electrical performance of a single thick trace while being compatible with the manufacturing process constraints
2Device complexity
If a conventional single-trace spiral inductor is used, then the structure is simple, but parasitic capacitance is high and Q value is reduced
Solution Approach 1:
The single trace is segmented into multiple parallel traces with different ground connections. This segmentation reduces the parasitic capacitance between the signal trace and ground, thereby increasing the Q value
Solution Approach 2:
Different portions of the inductor structure have different ground connections (inner turns grounded differently from outer turns). This local differentiation of ground connections optimizes the parasitic capacitance distribution and improves overall performance
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 multi-trace structure increases the Q value of the inductor, improving its efficiency and maintaining the operational frequency range while minimizing parasitic capacitance and conductor loss.
Implementation Method 1
increasing inductive coupling, thereby enhancing the Q value
Implementation Method 2
minimizing parasitic capacitance and conductor loss
Data Source
AI summary
A spiral inductor with a multi-trace structure having an insulating layer disposed on a substrate. A first spiral conductive trace with multiple turns is disposed on the insulating layer, wherein the outermost turn and the innermost turn of the first spiral conductive trace have a first end and a second end, respectively, and one of the first and second ends is connected to ground. A second spiral conductive trace with a single turn is disposed on the insulating layer and adjacent to the first spiral conductive trace, wherein the second spiral conductive trace is electrically connected to the turn that is connected to the ground and belongs to the first spiral conductive trace. The first spiral conductive trace has a relative outside and a relative inside, wherein the end of the first spiral conductive trace connected to ground and the second spiral conductive trace are located at different sides respectively.