Suspended MEMS Sensor in CMOS Substrate for Stress Decoupling

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Solution Overview

Problem

Existing semiconductor-based MEMS devices face challenges in integrating microelectromechanical systems (MEMS) with CMOS processes without increasing complexity, particularly in sub 130 nm technologies, and in minimizing stress on sensor components due to housing interactions, which affects their performance and cost.

Innovation Solution

The integration of a semiconductor device with a sensor portion suspended in a cavity via a monolithic suspension portion, where the sensor and suspension are formed as one piece, and optionally coated with a stress layer to apply biasing stress, allowing for out-of-plane deflection and decoupling from external mechanical influences, using techniques like Silicon-On-Nothing (SON) or Empty-Space-in-Silicon (ESS) processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If MEMS are integrated with CMOS processes using conventional methods, then sensor functionality is achieved, but device complexity increases and manufacturing precision deteriorates

Engineering Contradiction:

Improvesensor functionalityVSAvoidCMOS process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the MEMS sensor structure directly into the CMOS substrate by forming the sensor portion and suspension portion from the semiconductor substrate itself. This integration eliminates the need for separate MEMS fabrication processes and reduces the number of process steps, thereby achieving sensor functionality without increasing CMOS process complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sensor portion is segmented from the bulk substrate through selective release of sacrificial material in cavity regions, creating a suspended structure. This segmentation allows the sensor to function independently while maintaining compatibility with standard CMOS manufacturing processes

Inventive Principle:

Principle #1Segmentation

2Strength

If housing structures are used to protect sensor components, then mechanical stability is improved, but stress on sensor components increases

Engineering Contradiction:

Improvemechanical stabilityVSAvoidstress on sensor components

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The patent extracts the sensor portion from the rigid substrate by creating a cavity and suspending the sensor portion on flexible suspension portions. This extraction removes the sensor from the stress-prone housing structure while maintaining mechanical stability through the flexible suspension mechanism

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The suspension portions act as flexible connections between the sensor portion and the substrate, allowing mechanical movement while maintaining structural integrity. These flexible structures reduce stress transmission to the sensor components during operation

Inventive Principle:

Principle #30Flexible shells and thin films

3Manufacturing precision

If sensor portion is rigidly mounted to substrate, then manufacturing precision is improved, but sensor independence from external mechanical influences deteriorates

Engineering Contradiction:

Improvesensor positioningVSAvoidsensor independence

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent transitions from a static rigid mounting to a dynamic suspended structure where the sensor portion can move relative to the substrate. The suspension portions provide controlled flexibility that maintains manufacturing precision during fabrication while enabling sensor independence during operation through out-of-plane deflection

Inventive Principle:

Principle #15Dynamics

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 creation of low-thickness frontend-of-line structures, reduces stress on sensor components, and allows for cost-effective housing options while maintaining sensor independence from external mechanical influences, enhancing the performance and integration of MEMS devices like accelerometers and microphones.

Implementation Method 1

The stress layer may comprise a material with a different lattice constant and/or a different coefficient of thermal expansion than that of the substrate's semiconductor material

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

configured to apply an offset tensile or compressive stress or strain to the sensor portion of the semiconductor substrate

Methodology Applied

Scientific EffectStress:

Implementation Method 3

the sensor portion is deflectably suspended in the cavity at one side of the cavity via a suspension portion of the semiconductor substrate interconnecting the semiconductor substrate and the sensor portion

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS10544037B2Integrated semiconductor device and manufacturing method

Publication Date: 2020.01.28 INFINEON TECH DRESDEN GMBH & CO KG

AI summary

The present disclosure relates to an integrated semiconductor device, comprising a semiconductor substrate; a cavity formed into the semiconductor substrate; a sensor portion of the semiconductor substrate deflectably suspended in the cavity at one side of the cavity via a suspension portion of the semiconductor substrate interconnecting the semiconductor substrate and the sensor portion thereof, wherein an extension of the suspension portion along the side of the cavity is smaller than an extension of said side of the cavity.