Integrated Inductor with Varying Metal Trace Widths
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Solution Overview
Problem
Existing integrated inductor structures face challenges in increasing inductance without increasing area, which leads to higher parasitic series resistance, capacitance, and decreased quality factor Q due to manufacturing restrictions and the skin effect, especially in high-frequency operations.
Innovation Solution
The proposed integrated inductor structure reduces the overall area by varying the widths of metal traces and connecting traces, with narrower sections outside connecting areas and wider sections within, to minimize parasitic capacitance and sheet resistance, thereby enhancing the quality factor Q and self-resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of turns of the coil is increased to increase inductance, then the inductance increases, but the area of the inductor increases and parasitic series resistance and capacitance increase causing quality factor Q to decrease
Solution Approach 1:
The patent applies local quality by varying the width of metal traces along their length. Connecting traces have different widths in different sections (wider at connection points, narrower in intermediate sections), and spiral traces have width variations. This local optimization reduces parasitic capacitance in critical areas while maintaining current flow capacity, thereby improving quality factor Q without requiring increased area or turns.
2Reliability
If the number of turns of the coil is increased to increase inductance, then the inductance increases, but parasitic series resistance increases causing quality factor Q to decrease
Solution Approach 1:
The patent optimizes local trace widths to minimize resistance. Connecting traces are made wider at connection points to current points and at intermediate sections where current density is highest, reducing parasitic series resistance. This local reinforcement of conductive paths reduces energy loss without requiring additional turns or area.
3Reliability
If the area of the coil is increased, then the inductance increases, but displacement current increases causing substrate loss to increase
Solution Approach 1:
The patent reduces substrate loss by optimizing the local geometry of metal traces. By making connecting traces narrower in intermediate sections and wider only where necessary for current collection and connection, the effective area interacting with the substrate is minimized. This reduces displacement current and associated substrate losses while maintaining the required inductance through efficient trace routing and width optimization.
4Reliability
If the width of metal traces is reduced to decrease parasitic capacitance, then parasitic capacitance decreases, but sheet resistance increases causing quality factor Q to decrease
Solution Approach 1:
The patent resolves this contradiction by applying local quality - trace widths are optimized differently in different locations. Connecting traces are made wider at connection points to current points and at intermediate sections to reduce resistance, while being narrower in sections where reducing parasitic capacitance is more critical. This spatially varying width optimization balances the trade-off between resistance and capacitance, improving overall quality factor Q.
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 design achieves a 30% reduction in area, leading to improved quality factor Q and self-resonant frequency, allowing for more stable inductance and increased operating frequency range compared to prior-art inductors.
Implementation Method 1
The first metal trace includes a coil of 3 turns. When there is a need to increase the inductance of the planner spiral inductor 100, the number of turns of the coil of the first metal trace 110 must be increased. The increase in the number of turns not only causes an increase in the area of the planner spiral inductor 100, but also causes an increase in the parasitic series resistance and the parasitic capacitance
Implementation Method 2
When the inductor operates in high frequencies, greater magnetic fields are induced at inner turns of the metal coil than at outer turns. Intense magnetic fields induce eddy currents at inner turns of the metal coil. The eddy currents causes uneven distribution of currents, most currents being pushed to the surface of the metal coil, which is known as a skin effect
Implementation Method 3
The other reason is that a time-varying electromagnetic field of the inductor penetrates a dielectric layer, which causes a magnetically induced eddy current on the substrate. Energy losses occur due to the opposite directions of the induced current and the current of the inductor
Data Source
AI summary
This invention discloses an integrated inductor structure, including a first metal trace, a second metal trace, and a connecting metal trace. Tow terminals of the connecting metal trace are respectively connected to the first metal trace and the second metal trace through at least a connecting structure. The connected first metal trace, the connecting metal trace and the second metal trace together form an inductor structure. The connecting structure is connected to a connecting area of the first metal trace. The connecting area of the first metal trace has a first width. A smallest width of the first metal trace is a second width. The second width is smaller than the first width.