Asymmetric Spiral Inductor with Multi-Layer Segmentation
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Solution Overview
Problem
Conventional asymmetric spiral inductors face challenges in improving inductance and quality factor Q without increasing the overall area, as higher turns lead to increased parasitic series resistance and capacitance, which decrease self-resonant frequency and quality factor Q, and are affected by metal and substrate losses.
Innovation Solution
The design of an asymmetric spiral inductor with a polygonal spiral coil and metal segments in multiple layers, where the metal segments in the upper layer extend along the edges of the polygon, forming a polyline shape, and connected via structures, allowing for improved mutual inductance and quality factor Q without exceeding one turn in length, particularly effective at frequencies above 5GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of turns of the spiral inductor is increased to improve inductance, then the inductance increases, but the parasitic series resistance and parasitic capacitance increase, causing the quality factor Q to decrease
Solution Approach 1:
The patent transitions from a planar single-layer spiral structure to a three-dimensional multi-layer structure with vertical stacking. The inductor comprises spiral coils in multiple metal layers (first metal layer, second metal layer, and third metal layer) connected by via structures, effectively utilizing the vertical dimension to increase inductance without proportionally increasing parasitic effects in the planar direction.
Solution Approach 2:
The patent divides the single continuous spiral coil into multiple segmented spiral coils distributed across different metal layers. Each layer contains separate spiral coil segments that are vertically connected, allowing the total inductance to be the sum of individual segment inductances while distributing the parasitic effects across multiple separated structures.
2Area of stationary object
If the area of the inductor is increased to improve inductance, then the inductance increases, but the displacement current and eddy current losses increase, causing the quality factor Q to decrease
Solution Approach 1:
By stacking spiral coils vertically across multiple metal layers separated by dielectric layers, the patent achieves increased inductance without proportionally increasing the planar area footprint. The vertical arrangement reduces the effective area interacting with the substrate, thereby minimizing displacement current and eddy current losses while maintaining high inductance.
3Speed
If the frequency of operation is increased to improve performance, then the signal processing capability improves, but the skin effect causes uneven current distribution and increases resistance, decreasing the quality factor Q
Solution Approach 1:
The patent segments the current path across multiple vertically stacked metal layers, which distributes the high-frequency current flow through separate conductive paths. This segmentation reduces the skin effect impact on any single layer by providing multiple parallel current channels, thereby maintaining lower effective resistance at high frequencies.
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 enhances inductance and quality factor Q while maintaining a compact size, and the asymmetric quality factors help suppress signal reflections and interference.
Implementation Method 1
The metal segments in different metal layers are connected by through structures, such as a via structure or a via array in a semiconductor process
Implementation Method 2
when the inductor is in operation, a time-varying electric displacement between the metal coil of the inductor and the substrate is generated; this electric displacement results in a displacement current between the metal coil and the substrate
Implementation Method 3
the time-varying electromagnetic field of the inductor penetrates through the dielectric and generates a magnetically induced eddy current on the substrate. The magnetically induced eddy current and the inductor current are opposite in directions, resulting in energy loss
Implementation Method 4
When the inductor is operated at high frequencies, the metal coil closer to the inner turns generates stronger magnetic field; a strong magnetic field induces eddy currents in the inner turns of the metal coil. The eddy currents cause uneven distribution of currents—most of the currents are pushed to the surface of the metal coil; this phenomenon is known as the skin effect
Data Source
AI summary
An asymmetric spiral inductor fabricated in a semiconductor structure includes a spiral coil, a metal segment, and a connection structure. The spiral coil is substantially disposed in a first metal layer and includes a first terminal and a second terminal. The first terminal is disposed at an outermost turn of the spiral coil, and the second terminal is disposed at an innermost turn of the spiral coil. The metal segment is disposed in a second metal layer different from the first metal layer and has a third terminal and a fourth terminal. The connection structure connects the second terminal and the third terminal. The first terminal and the fourth terminal form the two terminals of the asymmetric spiral inductor. The spiral coil is a polygon with N sides (N>4). A portion of the metal segment has a shape substantially identical to a portion of the contour of the polygon.