Integrated Inductor Guard Ring Structure for Parasitic Capacitance Reduction
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Solution Overview
Problem
The manufacturing of integrated inductors at 28 nm and 20 nm dimensions leads to high capacitance and quality factor issues due to thin oxide layers and thick redistribution layers, affecting the performance of inductors.
Innovation Solution
An integrated inductor structure is designed with a guard ring, patterned ground shield, and interlaced structure, where the guard ring includes inner and outer rings with openings, and the patterned ground shield is coupled to the rings to improve the quality factor and block steam from affecting other structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the oxide layer is made thin to achieve smaller dimensions (28 nm and 20 nm), then the manufacturing precision is improved, but the capacitance increases
Solution Approach 1:
The patent extracts and removes the oxide layer from between the guard ring and the inductor, eliminating the source of unwanted capacitance. By taking out the dielectric material that was causing the parasitic capacitance effect, the invention resolves the contradiction between achieving small dimensions and maintaining low capacitance.
2Manufacturing precision
If the redistribution layers (RDL) are made thick to support smaller dimensions, then the manufacturing precision is improved, but the capacitance among RDLs increases
Solution Approach 1:
The patent removes the RDL structure from the area beneath the inductor by using the guard ring to define a boundary. This extraction of the thick RDL layer eliminates the parasitic capacitance that would otherwise exist between thick RDL layers, while still allowing thick RDLs to be used elsewhere for maintaining manufacturing precision at small dimensions.
3Device complexity
If a conventional guard ring structure is used, then the device complexity is low, but the quality factor decreases
Solution Approach 1:
The patent extracts the oxide layer from the region between the guard ring and the inductor, creating an oxide-free zone. This modification to the guard ring structure eliminates parasitic capacitance effects that degrade the quality factor, while adding only minimal structural complexity compared to a conventional guard ring.
Data Source
AI summary
An integrated inductor structure includes a guard ring, a patterned ground shield, and an inductor. The guard ring includes an inner ring, an outer ring, and an interlaced structure. The inner ring is disposed in a first metal layer, and includes at least two inner ring openings. The outer ring is disposed in a second metal layer, and includes at least one outer ring opening. The interlaced structure is coupled to one of the at least two inner ring openings and the outer ring opening in an interlaced manner, such that the outer ring opening is enclosed. The patterned ground shield is disposed at an inner side of the inner ring, and coupled to the inner ring and the outer ring. The inductor is formed above the guard ring and the patterned ground shield.