Multi-Cavity MEMS Packaging with Variable Sealing Pressures

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional wafer-level packaging methods cannot vary the sealing pressure for different MEMS devices on a single chip or wafer, posing a challenge in integrating multiple MEMS devices with varying operational pressure requirements.

Innovation Solution

A method involving a silicon wafer with cavities as an encapsulation layer, where different MEMS devices are encapsulated within cavities at specific air pressures using eutectic bonding, glass-fit seal, or fusion bonding, with a channel allowing for different pressures to be maintained for each device, and sealing via chemical vapor deposition or plasma vapor deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional wafer-level packaging methods are used, then manufacturing process is simple, but all MEMS devices on a wafer must be sealed at the same pressure, preventing integration of devices with different operational pressure requirements

Engineering Contradiction:

Improveability to integrate multiple MEMS devices with different pressure requirementsVSAvoidpackaging structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The encapsulation wafer is divided into multiple separate cavities, each capable of being sealed at different pressures. This segmentation allows each MEMS device to be packaged in its own pressure-controlled environment while maintaining a unified wafer-level packaging structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the encapsulation wafer are designed with different cavity depths, creating local variations in sealing pressure. Devices requiring higher pressure are sealed in deeper cavities, while devices requiring lower pressure are sealed in shallower cavities, allowing each device to operate at its optimal pressure.

Inventive Principle:

Principle #3Local quality

2Productivity

If multiple MEMS devices with different pressure requirements are integrated on a single chip, then die size and manufacturing costs are reduced, but packaging complexity increases

Engineering Contradiction:

Improvemanufacturing efficiency and cost reductionVSAvoidpackaging process complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Cavities of different depths are pre-formed in the encapsulation wafer before the sealing process. This preliminary structuring allows subsequent sealing operations to automatically achieve different pressures for different devices without requiring complex real-time pressure control during sealing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex active pressure control mechanisms with a passive mechanical approach using cavities of varying depths. The depth difference itself creates the pressure differential during sealing, eliminating the need for multiple active pressure regulation systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If uniform sealing pressure is applied to all devices, then packaging process is simple, but device performance deteriorates when different devices require different operational pressures

Engineering Contradiction:

Improvedevice performance and reliabilityVSAvoidpackaging process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The encapsulation wafer incorporates cavities with locally varied depths tailored to the specific pressure requirements of each MEMS device. This local differentiation ensures each device is sealed at its optimal pressure for maximum performance while maintaining a relatively simple overall manufacturing process.

Inventive Principle:

Principle #3Local quality

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

Enables the integration of multiple MEMS devices on a single chip with varying operational pressures, reducing die size and manufacturing costs while maintaining device performance and reliability, and increasing device yields.

Implementation Method 1

wherein the second cavity includes at least one channel. The first MEMS device is encapsulated within the first cavity and the second MEMS device is encapsulated within the second cavity

Methodology Applied

Scientific EffectEutectic bonding:

Implementation Method 2

using eutectic bonding, glass-fit seal, or fusion bonding

Methodology Applied

Scientific EffectGlass-fit seal:

Implementation Method 3

using eutectic bonding, glass-fit seal, or fusion bonding

Methodology Applied

Scientific EffectFusion bonding:

Implementation Method 4

sealing via chemical vapor deposition or plasma vapor deposition

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Implementation Method 5

sealing via chemical vapor deposition or plasma vapor deposition

Methodology Applied

Scientific EffectPlasma vapor deposition: Plasma Enhanced Chemical Vapour Deposition

Data Source

PatentUS10183860B2Method to package multiple mems sensors and actuators at different gases and cavity pressures

Publication Date: 2019.01.22 MCUBE INC

AI summary

A method for fabricating a multiple MEMS device includes providing a semiconductor substrate having a first and second MEMS device, and an encapsulation wafer with a first cavity and a second cavity, which includes at least one channel. The first MEMS is encapsulated within the first cavity and the second MEMS device is encapsulated within the second cavity. These devices is encapsulated within a first encapsulation environment at a first air pressure, and encapsulating the first MEMS device within the first cavity at the first air pressure. The second MEMS device within the second cavity is then subjected to a second encapsulating environment at a second air pressure via the channel of the second cavity.