Substrate Openings for Eutectic Bonding Electrical Isolation

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Solution Overview

Problem

In the fabrication of micro electro mechanical system (MEMS) devices, eutectic bonding between substrates can lead to electrical shorts due to laterally-stretching metallic material contacting neighboring bonding material during thermal treatment and pressure application, which compromises the integrity of the package system.

Innovation Solution

The use of strategically formed openings in the substrates to accommodate and guide the softened metallic bonding material, along with guard rings, prevents electrical shorts by ensuring the metallic material fills these openings and avoids contact with neighboring material, thereby maintaining the electrical isolation between substrates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If eutectic bonding is performed with thermal treatment and pressure application, then bonding strength is improved, but electrical shorts occur due to lateral stretching of metallic material contacting neighboring bonding material

Engineering Contradiction:

Improvebonding strengthVSAvoidelectrical isolation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The substrate is segmented by forming openings (trenches) that divide and isolate the metallic bonding material into separate regions. These openings create physical barriers that prevent lateral stretching of the metallic material from contacting neighboring bonding material, thus maintaining electrical isolation while allowing strong bonding to occur within each segmented region.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The openings filled with dielectric material or air gaps act as intermediary elements between adjacent metallic bonding regions. These intermediaries provide electrical isolation and prevent direct contact between laterally-stretching metallic material from different bonding sites, resolving the electrical short issue while preserving bonding integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If metallic bonding material is softened and melted during eutectic bonding, then bonding effectiveness is improved, but lateral stretching causes contact with neighboring material

Engineering Contradiction:

Improvebonding effectivenessVSAvoidlateral stretching

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The openings are formed in the substrate before the eutectic bonding process. This preliminary action creates pre-defined containment structures that will receive and constrain the softened metallic bonding material during subsequent thermal treatment, preventing lateral stretching and contact with neighboring regions before the harmful effect can occur.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The metallic bonding material is placed in the openings before thermal treatment softens and melts it. This preliminary positioning ensures that when the material softens and expands during bonding, it remains confined within the opening boundaries, converting the potentially harmful lateral stretching into a beneficial filling action that enhances bonding effectiveness.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If openings are formed in substrates to accommodate bonding material, then electrical isolation is improved, but device complexity increases

Engineering Contradiction:

Improveelectrical isolationVSAvoidsubstrate structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The openings in the substrate serve multiple functions simultaneously: they provide electrical isolation between adjacent bonding regions, contain and guide the metallic bonding material during eutectic bonding, and define the bonding site geometry. This multi-functionality achieves improved electrical isolation without proportionally increasing device complexity, as a single structural feature accomplishes multiple objectives.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances the reliability and hermeticity of the package system by preventing electrical shorts and ensuring effective bonding while maintaining the electrical isolation between substrates, thus improving the overall performance and durability of MEMS devices.

Implementation Method 1

the Al pad is subjected to a thermal treatment and a pressure, such that the Al pad is softened and melted

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

The use of strategically formed openings in the substrates to accommodate and guide the softened metallic bonding material

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Implementation Method 3

a pressure of the eutectic bonding presses the material of the Al pad stretching laterally

Methodology Applied

Scientific EffectPressure application: Pressure Increase

Data Source

PatentUS9000578B2Package systems having an opening in a substrate thereof and manufacturing methods thereof

Publication Date: 2015.04.07 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A package system includes a first substrate and a second substrate. The second substrate is electrically coupled with the first substrate. The second substrate includes at least one first opening. At least one electrical bonding material is disposed between the first substrate and the second substrate. A first portion of the at least one electrical bonding material is at least partially filled in the at least one first opening.