MEMS Device Multi-Pressure Sealed Cavities
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Solution Overview
Problem
The integration of MEMS devices into integrated circuit manufacturing processes poses challenges, particularly in electrically interconnecting them, as existing methods struggle to efficiently manage the unique requirements of miniaturized MEMS devices within a single chip.
Innovation Solution
The described method involves forming MEMS devices in sealed cavities with different pressures using a substrate bonding process, where a cap wafer with an out-gas layer is bonded to a substrate, and the out-gas layer is annealed to increase the pressure in one cavity, allowing for the simultaneous integration of MEMS devices like gyroscopes and accelerometers on a single chip with varying pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MEMS devices are integrated into integrated circuit manufacturing processes, then productivity and miniaturization are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent divides the integrated circuit chip into multiple sealed cavities, each containing specific MEMS devices. This segmentation allows different MEMS devices to operate under different pressure conditions while maintaining a unified manufacturing process, thereby improving integration efficiency without significantly increasing manufacturing complexity.
Solution Approach 2:
The patent creates localized environments within sealed cavities by bonding cap wafers to the substrate, forming isolated chambers with controlled pressure conditions. This local quality approach allows different regions of the chip to have different pressure environments suitable for different MEMS device types, resolving the conflict between integration efficiency and manufacturing complexity.
2Adaptability or versatility
If multiple MEMS devices with different pressure conditions are integrated on a single chip, then adaptability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary actions by forming the sealed cavities and placing MEMS devices within them before final bonding. The cap wafer is prepared with appropriate thickness and material properties in advance, and MEMS devices are positioned in their respective cavities before the bonding process seals the pressure environments. This preliminary action approach allows for better control of manufacturing precision while achieving diverse pressure conditions.
Solution Approach 2:
The patent controls pressure conditions by adjusting parameters such as cap wafer thickness, bonding temperature, and cavity volume. By changing these parameters, different pressure environments are created within sealed cavities without requiring fundamentally different manufacturing processes, thus improving adaptability while managing manufacturing precision requirements.
3Reliability
If cap wafer bonding is used to form sealed cavities, then reliability is improved, but additional process steps increase device complexity
Solution Approach 1:
The patent merges the cavity sealing function with the existing cap wafer structure by bonding the cap wafer directly to the substrate. This combines multiple functions (sealing, structural support, and pressure control) into a single component and process step, improving reliability without significantly increasing overall device complexity.
Solution Approach 2:
The cap wafer serves multiple functions: it provides the sealing structure for sealed cavities, supports the out-gas layer for pressure control, and acts as part of the mechanical structure. This multi-functionality reduces the need for additional separate components and process steps, thereby improving reliability while limiting increases in device complexity.
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 enables the smooth integration of MEMS devices with different pressure conditions within the same manufacturing process, enhancing the sensitivity and reliability of MEMS chips by maintaining minimal additional costs and complexity.
Implementation Method 1
The out gas layer is annealed to release gas from the out gas layer into the second sealed cavity and increase a pressure of the second sealed cavity
Data Source
AI summary
Micro-electromechanical (MEMS) devices and methods of forming are provided. The MEMS device includes a first substrate including a first conductive feature, a first movable element positioned over the first conductive feature, a second conductive feature, and a second movable element positioned over the second conductive feature. The MEMS device also includes a cap bonded to the first substrate, where the cap and the first substrate define a first sealed cavity and a second sealed cavity. The first conductive feature and the first movable element are disposed in the first sealed cavity and the second conductive feature and the second movable element are disposed in the second sealed cavity. A pressure of the second cavity is higher than a pressure of the first sealed cavity, and an out gas layer is disposed in a recess of the cap that partially defines the second sealed cavity.