CMOS Die Nesting in MEMS Microphone Back Chamber

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Solution Overview

Problem

Existing MEMS microphone packages with a CMOS die placed underneath the MEMS die either increase the package height or reduce the back volume, negatively impacting microphone sensitivity and signal-to-noise ratio.

Innovation Solution

The CMOS die is positioned underneath the MEMS die within the back chamber of the MEMS die, increasing the MEMS die dimensions to maintain or improve back volume, thereby reducing the package footprint while maintaining acoustic performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the CMOS die is placed underneath the MEMS die to reduce package footprint, then the package footprint is reduced, but the back volume is decreased, negatively impacting microphone sensitivity and signal-to-noise ratio

Engineering Contradiction:

Improvepackage footprintVSAvoidback volume

Core Design Contradiction:

Area of stationary objectVSVolume of stationary object

Solution Approach 1:

The CMOS die is nested within the back chamber volume of the MEMS die, effectively placing one component inside the acoustic cavity space rather than occupying horizontal package area. This nesting approach allows the CMOS die to be positioned underneath the MEMS die while maintaining sufficient back volume by utilizing the vertical space within the back chamber, thereby resolving the contradiction between reducing package footprint and maintaining back volume for acoustic performance

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The solution transitions from a planar side-by-side arrangement to a three-dimensional stacked configuration, moving components into the vertical dimension. By positioning the CMOS die underneath the MEMS die and utilizing the back chamber volume vertically, the package footprint is reduced while the back volume is preserved through proper vertical space management within the back chamber

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Area of stationary object

If the MEMS die is thinned to accommodate the CMOS die underneath, then the package footprint is reduced, but the back volume is decreased, negatively impacting microphone sensitivity and signal-to-noise ratio

Engineering Contradiction:

Improvepackage footprintVSAvoidmicrophone sensitivity and signal-to-noise ratio

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The CMOS die is nested within the back chamber volume, utilizing the vertical space inside the acoustic cavity. This nesting allows the MEMS die to maintain its original thickness without thinning, as the CMOS die occupies space within the back chamber rather than requiring reduction of the MEMS die thickness, thereby preserving both package footprint reduction and microphone sensitivity

Inventive Principle:

Principle #7Nested doll (Nesting)

3Area of stationary object

If the CMOS die is positioned underneath the MEMS die, then the package footprint is reduced, but the package height is increased

Engineering Contradiction:

Improvepackage footprintVSAvoidpackage height

Core Design Contradiction:

Area of stationary objectVSLength of stationary object

Solution Approach 1:

The CMOS die is nested within the back chamber volume, utilizing the existing vertical space inside the package rather than adding height externally. This nesting approach allows the CMOS die to be accommodated within the back chamber boundaries, reducing package footprint while minimizing or eliminating the need to increase overall package height

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS8791531B2Package with a CMOS die positioned underneath a MEMS die

Publication Date: 2014.07.29 KNOWLES ELECTRONICS LLC

AI summary

A package is provided. The package has a substrate and a cover. A MEMS die is provided having a diaphragm. A CMOS die is provided wherein at least a portion of the CMOS die is positioned between the diaphragm and the substrate.