Bond Rings with Spacers for Hermetic MEMS Sealing

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Solution Overview

Problem

The semiconductor industry faces challenges in achieving hermetic sealing and reliable bonding of micro-electromechanical systems (MEMS) devices due to issues like gas leaking, Kirkendall voids, and dispersion of eutectic compounds, which affect the integration density and reliability of semiconductor device packages.

Innovation Solution

The use of spacers formed along the sidewalls of bond rings and bond pads during the eutectic bonding process improves gap controllability, reduces outgassing, and enhances hermetic sealing by preventing the undesired dispersion of eutectic compounds, thereby alleviating manufacturing defects and improving the reliability of semiconductor device packages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If eutectic bonding is performed without spacers, then bonding process is simpler, but hermetic sealing is compromised due to gas leaking and Kirkendall voids

Engineering Contradiction:

Improvehermetic sealingVSAvoidbonding process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A spacer layer is introduced as an intermediary element between the bond pads during eutectic bonding. This spacer layer serves as a mediator that prevents direct contact between bonding surfaces until the eutectic reaction is complete, thereby preventing gas leaking and Kirkendall void formation while maintaining process simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The spacer layer is formed on the bond pads before the eutectic bonding process begins. This preliminary action prepares the bonding surfaces in advance to prevent harmful effects during bonding, ensuring hermetic sealing without requiring complex process modifications

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If bond rings are bonded without spacers, then manufacturing process is faster, but manufacturing defects increase due to dispersion of eutectic compounds

Engineering Contradiction:

Improvebonding precisionVSAvoidbonding speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The spacer layer acts as a temporary intermediary that confines the eutectic compounds during the bonding process. This prevents the dispersion of eutectic compounds beyond the bond ring edges, improving bonding precision without significantly impacting the overall bonding speed

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The spacer layer functions as a thin film structure that flexibly accommodates the eutectic bonding process while maintaining precise boundaries. The thin film nature allows for rapid processing while the structured configuration prevents compound dispersion, balancing precision and productivity

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If no spacers are used on bond pads, then process steps are reduced, but outgassing increases affecting sealing quality

Engineering Contradiction:

Improvesealing qualityVSAvoidmanufacturing ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The spacer layer serves as a protective intermediary that manages gas evolution during eutectic bonding. It provides a controlled pathway for outgassing while maintaining the integrity of the bond ring structure, thereby improving sealing quality without requiring complex manufacturing procedures

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The spacer layer extracts or removes the harmful effect of outgassing by providing a dedicated structure for gas release. This separates the gas evolution function from the bonding function, allowing both to occur simultaneously without compromising sealing quality or manufacturing simplicity

Inventive Principle:

Principle #2Taking out (Extraction)

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

The implementation of spacers on bond rings and bond pads enhances the hermetic sealing of MEMS devices, reducing manufacturing defects and improving the reliability of semiconductor device packages by controlling the gap and minimizing Kirkendall voids and outgassing, leading to more reliable and efficient bonding processes.

Implementation Method 1

bonded to other bond rings/bond pads using a eutectic bonding process

Methodology Applied

Scientific EffectEutectic bonding:

Implementation Method 2

reduce outgassing (e.g., gas leaking from the cavity due to differences between pressure levels of the sealed cavity and ambient)

Methodology Applied

Scientific EffectOutgassing reduction:

Data Source

PatentUS10351418B2Bond rings in semiconductor devices and methods of forming same

Publication Date: 2019.07.16 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An embodiment method includes forming a first plurality of bond pads on a device substrate, depositing a spacer layer over and extending along sidewalls of the first plurality of bond pads, and etching the spacer layer to remove lateral portions of the spacer layer and form spacers on sidewalls of the first plurality of bond pads. The method further includes bonding a cap substrate including a second plurality of bond pads to the device substrate by bonding the first plurality of bond pads to the second plurality of bond pads.