TSV Shunt Capacitance Reduction via Segmented Polysilicon and Dielectric Layers
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Solution Overview
Problem
Microelectromechanical system (MEMS) devices face performance degradation due to significant shunt capacitance in dielectric trenches, particularly in capacitive sensing and RF applications, which affects their operational efficiency.
Innovation Solution
The implementation of through silicon via (TSV) structures with multiple high-resistivity poly filled layers interleaved with dielectric layers, coupled in series to reduce capacitive shunting effects, along with the use of low-K dielectric materials and partial trench filling under vacuum to lower shunt capacitance, and optimizing operating frequencies to minimize impedance ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dielectric trenches are used to form electrodes for sensing characteristics, then the MEMS device can sense characteristics within the MEMS chip, but the trenches have significant shunt capacitance that degrades performance
Solution Approach 1:
The trench is divided into multiple sections with different fill materials. Specifically, the trench is segmented into a first portion filled with polysilicon and a second portion filled with vacuum or low-k dielectric material. This segmentation allows different regions to serve different functions: the polysilicon portion provides mechanical support and controlled electrical properties, while the vacuum/low-k portion minimizes shunt capacitance, thereby resolving the contradiction between sensing capability and shunt capacitance reduction.
Solution Approach 2:
Different portions of the trench are assigned different local properties through selective filling. The first portion contains polysilicon with specific dielectric and mechanical properties, while the second portion contains vacuum or low-k dielectric material with minimal shunt capacitance characteristics. This local differentiation optimizes both sensing performance and shunt capacitance reduction in their respective regions, resolving the technical contradiction.
2Ease of manufacture
If traditional trench structures are used, then manufacturing is simplified, but shunt capacitance significantly degrades MEMS device performance
Solution Approach 1:
The trench fabrication process is segmented into selective filling operations. The trench is first filled with polysilicon in the first portion, then vacuum or low-k dielectric material is introduced in the second portion. This segmented approach maintains manufacturing feasibility while achieving the dual goals of structural integrity and reduced shunt capacitance, thus resolving the contradiction between ease of manufacture and device performance reliability.
Solution Approach 2:
The trench employs a composite structure with multiple fill materials: polysilicon in the first portion and vacuum or low-k dielectric material in the second portion. This composite material approach combines the advantages of each material - polysilicon provides mechanical strength and controlled electrical properties, while vacuum/low-k material minimizes shunt capacitance. The composite structure achieves both manufacturability and enhanced device performance, resolving the technical contradiction.
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 significantly reduces shunt capacitance, enhancing the signal-to-noise ratio and reducing power consumption, thereby improving the performance and energy efficiency of MEMS devices, especially in mobile systems with limited energy sources.
Implementation Method 1
each trench of the pair of trenches includes first and second vertical layers including a dielectric, the first and second vertical layers separated by a third vertical layer including polysilicon
Implementation Method 2
the use of low-K dielectric materials and partial trench filling under vacuum to lower shunt capacitance
Implementation Method 3
partial trench filling under vacuum to lower shunt capacitance
Data Source
AI summary
This document refers to apparatus and methods for a device layer of a microelectromechanical system (MEMS) sensor having vias with reduced shunt capacitance. In an example, a device layer can include a substrate having a pair of trenches separated in a horizontal direction by a portion of the substrate, wherein each trench of the pair of trenches includes first and second vertical layers including dielectric, the first and second vertical layers separated by a third vertical layer including polysilicon.