MEMS Substrate Joint Structure for Stray Capacitance Isolation
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Solution Overview
Problem
MEMS devices face issues with stray capacitance and increased power consumption due to unintended electrical coupling between substrates through conductive spacer structures, leading to deteriorated electric characteristics and higher power consumption.
Innovation Solution
A MEMS device configuration featuring a eutectic layer with a plurality of metal types between substrates, a conductive contact layer that does not melt during a metal eutectic reaction, and an insulating layer to prevent electrical coupling, ensuring controlled substrate spacing and reduced stray capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conductive spacer structure is used to control the interval between substrates, then variations in interval are reduced, but stray capacitance increases and power consumption increases
Solution Approach 1:
The spacer structure is divided into two distinct functional parts: a conductive lower spacer portion that provides mechanical support and interval control, and an insulating upper spacer portion that prevents electrical coupling. This segmentation allows each part to fulfill its specific function without causing harmful effects.
Solution Approach 2:
Different portions of the spacer structure have different electrical properties: the lower portion is conductive to provide structural integrity and precise interval control, while the upper portion is insulating to prevent stray capacitance. This local differentiation of material properties resolves the contradiction between precision control and electrical isolation.
2Strength
If a conductive spacer structure is used to join substrates, then mechanical strength is improved, but electrical coupling occurs causing power consumption increase
Solution Approach 1:
The spacer is segmented into a conductive lower portion for mechanical bonding and strength, and an insulating upper portion for electrical isolation. This allows the joint to achieve both mechanical strength and electrical isolation, preventing energy loss through unwanted current paths.
Solution Approach 2:
The insulating upper spacer portion acts as an intermediary barrier between the conductive lower spacer and the upper substrate, preventing direct electrical coupling while maintaining the mechanical connection established by the conductive portion.
3Measurement precision
If a conductive spacer structure is used for substrate joining, then positioning accuracy is improved, but unwanted wiring is formed deteriorating electric characteristics
Solution Approach 1:
The spacer structure is segmented such that the lower conductive portion provides precise positioning and mechanical support, while the upper insulating portion prevents the formation of unwanted electrical wiring paths, thereby maintaining reliable electric characteristics.
Solution Approach 2:
The spacer exhibits local quality differentiation where the lower portion is conductive for precise positioning and the upper portion is insulating to prevent unwanted electrical coupling, thus maintaining both positioning accuracy and electrical reliability.
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
The solution effectively prevents stray capacitance and power consumption increases by maintaining electrical insulation between substrates, enhancing the electric characteristics and efficiency of MEMS devices.
Implementation Method 1
The first and second substrates are joined with the conductive posts interposed therebetween through a metal eutectic reaction between each conductive post and the coating material
Implementation Method 2
a first insulating layer on the contact layer and electrically insulated
Data Source
AI summary
A MEMS device includes a first substrate with a MEMS structure, a second substrate facing the first substrate with an interval therebetween, a first joint portion that includes a eutectic layer including a eutectic alloy of different metals between the first and second substrates and that surrounds the MEMS structure and is joined to the first and second substrates, a conductive contact layer between the first and second substrates and that is in contact with the first and second substrates and does not melt at a temperature at which the plural types of metal undergo a metal eutectic reaction, and an insulating layer located on the contact layer and electrically insulated.