Low Loss Coupling Capacitor With Segmented Doped Wells
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Solution Overview
Problem
Existing coupling capacitor designs suffer from high losses and inefficiencies, particularly in compact devices, due to significant parasitic capacitance and resistance, which hinder their performance in radio frequency (RF) applications and require a reduction in size and power consumption.
Innovation Solution
The design incorporates a metal-oxide-semiconductor (MOS) structure with p-doped and n-doped semiconductor wells, insulating layers, and a metal pattern with interleaved layers and vias to reduce parasitic capacitance and enhance wanted capacitance, allowing for low loss coupling capacitors in both n-type varactor (NVAR) and p-type varactor (PVAR) configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional coupling capacitor designs are used, then the capacitor can block DC and pass AC signals, but the parasitic capacitance and resistance are significant causing high losses
Solution Approach 1:
The capacitor structure is segmented into multiple doped regions (first doped region, second doped region, third doped region, fourth doped region) separated by undoped or lightly-doped regions. This segmentation creates multiple depletion regions that work together to reduce parasitic effects while maintaining the coupling function.
Solution Approach 2:
Different regions of the capacitor structure have different doping concentrations optimized for specific functions: heavily doped regions (104, 108, 112, 116) provide low resistance contacts, while lightly-doped or undoped regions (102, 110, 114) create depletion regions that reduce parasitic capacitance. This local optimization of doping quality reduces overall losses.
2Volume of moving object
If the capacitor size is reduced for compact devices, then power consumption is reduced, but parasitic effects become more significant
Solution Approach 1:
The capacitor structure embeds multiple functional regions within a compact footprint. The nested doped regions (first, second, third, fourth doped regions) are arranged in a nested configuration where each region contributes to the overall capacitance while minimizing the total device area. This allows high capacitance per unit area with reduced parasitic effects.
Solution Approach 2:
The invention transitions from a planar capacitor design to a three-dimensional structure with doped regions extending in multiple dimensions. The vertical stacking of doped regions and the use of depletion regions in the vertical direction enable high capacitance density without increasing the lateral footprint, thus reducing parasitic effects associated with smaller planar dimensions.
3Quantity of substance
If the capacitance per area is increased for compact integration, then the coupling efficiency improves, but the parasitic capacitance increases
Solution Approach 1:
The invention changes the doping concentration parameter across different regions to optimize the ratio of useful capacitance to parasitic capacitance. Heavily doped regions provide low resistance while lightly-doped regions create depletion zones that reduce parasitic capacitance. By carefully controlling doping parameters (concentration, depth, distribution), the design achieves high capacitance per area with minimized parasitic effects.
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 approach results in reduced resistance and parasitic capacitance, enabling high capacitance per area integration in compact dimensions, suitable for RF applications, with improved coupling efficiency and reduced losses, facilitating the use of differential signal paths in isolated wells.
Implementation Method 1
an insulating layer over the P well between the source and drain
Implementation Method 2
a deep n-doped semiconductor well (DNW) in the Psub, a p-doped semiconductor well (P well) in the DNW
Implementation Method 3
The design incorporates a metal-oxide-semiconductor (MOS) structure with p-doped and n-doped semiconductor wells
Data Source
AI summary
Embodiments are provided herein for low loss coupling capacitor structures. The embodiments include a n-type varactor (NVAR) configuration and p-type varactor (PVAR) configuration. The structure in the NVAR configuration comprises a p-doped semiconductor substrate (Psub), a deep n-doped semiconductor well (DNW) in the Psub, and a p-doped semiconductor well (P well) in the DNW. The circuit structure further comprises a source terminal of a p-doped semiconductor material within P well, and a drain terminal of the p-doped semiconductor material within the P well. Additionally, the circuit structure comprises an insulated gate on the surface of the P well, a metal pattern comprising a plurality of layers of metal lines, and a plurality of vias through the metal lines. The vias are contacts connecting the metal lines to the gate, the source terminal, and the drain terminal.