Capacitor Array Layout Using Edge Parasitics for Capacitance Matching
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Solution Overview
Problem
Conventional semiconductor capacitor arrays face issues such as wasted circuit area due to the need for broad gaps to avoid parasitic capacitance and differences in capacitance between effective and dummy capacitor units, leading to accuracy degradation in applications like capacitive digital-to-analog converters.
Innovation Solution
The semiconductor capacitor array layout incorporates a first and second conductive structure with longitudinal and lateral strips in different IC layers, forming well-shaped structures to generate parasitic capacitance, allowing for efficient voltage transmission and reducing capacitance differences between capacitor units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gap between the first capacitor row and the second capacitor row is broadened to avoid parasitic capacitance, then the accuracy of capacitance measurement is improved, but the circuit area is wasted
Solution Approach 1:
The patent converts the harmful parasitic capacitance into a beneficial feature by intentionally designing dummy capacitor units that generate controlled parasitic capacitance. This parasitic capacitance is used to compensate for edge effects and improve the accuracy of effective capacitor units, thereby eliminating the need for large gaps between capacitor rows while maintaining measurement precision.
Solution Approach 2:
The patent applies different functional qualities to different regions of the capacitor array. Dummy capacitor units are placed at specific locations (edge regions) to generate parasitic capacitance, while effective capacitor units are placed in interior regions for accurate measurement. This local differentiation allows the system to maintain high measurement accuracy without requiring increased spacing between all capacitor units.
2Ease of manufacture
If the ratio (W/L) of the U-shaped structure is enlarged to conform to advanced process specifications, then the manufacturing compliance is improved, but the circuit area consumption increases
Solution Approach 1:
The patent segments the capacitor array into multiple rows and columns of capacitor units, allowing the W/L ratio requirement to be met locally in each unit while the overall array maintains compact dimensions. The segmentation into individual capacitor units with specific W/L ratios enables compliance with advanced process specifications without requiring the entire array to expand in size.
Solution Approach 2:
The patent arranges capacitor units in a two-dimensional array layout rather than using a single large capacitor structure. This dimensional arrangement allows each unit to meet the W/L ratio requirement while the overall array consumes minimal circuit area through efficient spatial utilization across multiple rows and columns.
3Object-generated harmful factors
If dummy capacitor units are added to the periphery of the layout, then the parasitic capacitance generation is improved, but the capacitance uniformity between effective and dummy units creates measurement errors
Solution Approach 1:
The patent converts the harmful parasitic capacitance effect into a beneficial compensation mechanism. Dummy capacitor units are specifically designed to generate parasitic capacitance that compensates for edge effects on effective capacitor units. By carefully controlling the number and placement of dummy units, the system achieves improved measurement accuracy while maintaining capacitance uniformity across all effective units.
Solution Approach 2:
The patent implements a feedback mechanism where the parasitic capacitance generated by dummy capacitor units is used to compensate for measurement errors in effective capacitor units. The dummy units create a controlled parasitic effect that counterbalances the unwanted edge effects, thereby improving the overall measurement precision and capacitance uniformity of the array.
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 layout mitigates circuit area waste, conforms to advanced processes like FinFET, and ensures uniform capacitance across all effective capacitor units, enhancing the linearity of capacitive digital-to-analog converters.
Implementation Method 1
the first conductive strips and the second conductive strips alternatively disposed in the first IC layer form a plurality of well-shaped structures... the inner second conductors and the outer wells jointly generate the parasitic capacitance
Data Source
AI summary
A semiconductor capacitor array layout generates parasitic capacitance toward an edge of the layout to reduce a capacitance difference between an outer capacitor unit and an inner capacitor unit. The semiconductor capacitor array layout includes a primary capacitor structure and an outer capacitor structure. Each of the primary capacitor structure and the outer capacitor structure includes a first crisscross structure and a second crisscross structure that are staggered. Each of the first crisscross structure and the second crisscross structure includes longitudinal conductive strips and lateral conductive strips, wherein the longitudinal conductive strips are disposed in a first integrated circuit (IC) layer and the lateral conductive strips are disposed in a second IC layer. The second crisscross structure of the primary capacitor structure and the first crisscross structure of the outer capacitor structure jointly generate the parasitic capacitance.