MEMS Electrostatic Bonding with Biasing Layer
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Solution Overview
Problem
Electrostatic bonding techniques for microelectro-mechanical system (MEMS) devices require high temperatures or high DC voltages, which can damage internal movable components.
Innovation Solution
An electrostatic bonding method involving a semiconductor substrate with a movable component and a glass substrate, where an electrostatic biasing layer completely overlapping the movable component is used, allowing for DC voltage application between the substrates to facilitate bonding without damaging the movable parts by ensuring equal potential and minimizing electric field effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electrostatic bonding is performed at high DC voltages to achieve good package airtightness, then bonding strength is improved, but movable components may be damaged
Solution Approach 1:
The patent divides the bonding interface into two separate layers: a first bonding layer formed on the substrate and a second bonding layer formed on the encapsulating layer. This segmentation allows the bonding process to occur in stages, with the movable component protected during the second bonding operation, thereby achieving strong bonding without damaging the movable components through excessive voltage exposure.
Solution Approach 2:
The first bonding layer is formed in advance on the substrate before the encapsulating layer is bonded to the substrate. This preliminary bonding action establishes a stable foundation that reduces the voltage required for the final bonding step, thereby protecting the movable component from high voltage damage while ensuring adequate bonding strength.
2Reliability
If high temperatures are used for bonding to ensure package airtightness, then sealing quality is improved, but movable components may be damaged
Solution Approach 1:
The patent changes the bonding parameters by using a multi-layer bonding structure with different bonding conditions for each layer. The first bonding layer can be formed at optimized temperature and voltage conditions, while the second bonding layer (encapsulating layer) is formed under conditions that protect the movable component. This parameter optimization ensures package airtightness without exposing the movable component to damaging high temperatures.
3Device complexity
If a single bonding layer is used for electrostatic bonding, then device complexity is reduced, but bonding strength and airtightness are insufficient
Solution Approach 1:
The bonding structure is segmented into a first bonding layer on the substrate and a second bonding layer on the encapsulating layer. This segmentation enables each layer to contribute to different aspects of bonding performance: the first layer provides foundational adhesion while the second layer ensures airtight sealing. The segmented approach achieves superior bonding strength and airtightness without excessive complexity, as each layer can be optimized independently.
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 method enables effective bonding of MEMS devices at lower risk of damaging movable components, maintaining device integrity and package airtightness while reducing the need for high temperatures or voltages.
Implementation Method 1
An electrostatic biasing layer is disposed between the movable component and the glass substrate. The electrostatic biasing layer completely overlaps with the movable component. The electrostatic biasing layer and the substrate are equal potential.
Implementation Method 2
A direct-current (DC) voltage is provided between the substrate and the glass substrate to electrostatic bonding the substrate and the glass substrate.
Data Source
AI summary
A microelectro-mechanical system (MEMS) device includes a substrate of a semiconductor material having thereon a movable component, a glass substrate bonded to the substrate, an electrostatic biasing layer disposed between the movable component and the glass substrate. A cavity is defined between the movable component and a top surface of the glass substrate. The electrostatic biasing layer completely overlaps with the movable component.