Insulator Layer MEMS Switches for Shorting and Undercutting
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Solution Overview
Problem
As integrated circuit geometries shrink, fabricating micro-electromechanical systems (MEMS) devices becomes increasingly problematic due to risks of electrical shorting and metal undercutting in MEMS switches, which affect the reliability and functionality of tunable and adaptive circuits.
Innovation Solution
Incorporating an insulator layer between two metal layers of a semiconductor die to prevent electrical shorting and metal undercutting, while also serving as a capacitive dielectric in capacitive MEMS switches, thereby enhancing the integration of ohmic and capacitive MEMS switches into a single semiconductor die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If MEMS devices are integrated into semiconductor dies with smaller geometries, then circuit integration density is improved, but fabrication reliability deteriorates due to risks of electrical shorting and metal undercutting
Solution Approach 1:
A sacrificial layer is introduced as an intermediary between the first and second metal layers during fabrication. This sacrificial layer prevents direct contact between the metal layers during the etching process, eliminating the risk of electrical shorting and metal undercutting. After fabrication, the sacrificial layer is removed to achieve the desired MEMS switch functionality. This intermediary approach resolves the contradiction by enabling reliable fabrication of small-geometry MEMS devices without compromising integration density.
2Adaptability or versatility
If metal layers are etched to form cantilevers in MEMS switches, then device functionality is improved, but metal undercutting of the actuator occurs
Solution Approach 1:
The sacrificial layer serves as a protective intermediary during the etching process that forms the cantilever. It prevents the etchant from attacking and undercutting the actuator metal layer while allowing the cantilever metal layer to be properly etched. This maintains manufacturing precision of the actuator while still enabling the desired MEMS switch functionality with movable cantilever contacts.
Solution Approach 2:
The sacrificial layer is deposited and patterned before the etching of the metal layers. This preliminary action establishes a protective barrier in advance that prevents metal undercutting during the subsequent etching process. The sacrificial layer is strategically positioned to protect the actuator while allowing cantilever formation, thereby preserving manufacturing precision before the actual etching occurs.
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 insulator layer effectively reduces metal undercutting and prevents electrical shorting, allowing for reliable integration of MEMS switches and capacitive elements into semiconductor dies, improving the performance and reliability of tunable and adaptive circuits.
Implementation Method 1
the insulator layer may be used to reduce metal undercutting during fabrication, to prevent electrical shorting of a MEMS actuator to a MEMS cantilever
Implementation Method 2
the insulator layer may be used to reduce metal undercutting during fabrication
Implementation Method 3
In a capacitive MEMS switch, the insulator layer may be used as a capacitive dielectric between capacitive plates
Data Source
AI summary
The present invention relates to using an insulator layer between two metal layers of a semiconductor die to provide a micro-electromechanical systems (MEMS) device, such as an ohmic MEMS switch or a capacitive MEMS switch. In an ohmic MEMS switch, the insulator layer may be used to reduce metal undercutting during fabrication, to prevent electrical shorting of a MEMS actuator to a MEMS cantilever, or both. In a capacitive MEMS switch, the insulator layer may be used as a capacitive dielectric between capacitive plates, which are provided by the two metal layers. A fixed capacitive element may be provided by the insulator layer between the two metal layers. In one embodiment of the present invention, an ohmic MEMS switch, a capacitive MEMS switch, a fixed capacitive element, or any combination thereof may be integrated into a single semiconductor die.