Heterojunction Substrate Bonding via Organic Adhesive Layer

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Solution Overview

Problem

The challenge in joining substrates of different materials for digital appliances is the delamination, bending, and cracking caused by thermal expansion coefficient differences, leading to high error rates and low yield in electronic device fabrication.

Innovation Solution

A heterojunction structure is created by joining substrates with an adhesive layer, where one substrate has a thermal expansion coefficient different from the other, and at least one of the adhesive or insulation layers is made of an organic material to alleviate thermal stresses and ensure stable bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If substrates of different materials are joined, then functionality and miniaturization are improved, but delamination, bending, and cracking occur due to thermal expansion differences

Engineering Contradiction:

ImprovefunctionalityVSAvoidbonding stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

An adhesive layer is introduced as an intermediary between the first substrate and second substrate to join them. This adhesive layer acts as a mediator that can accommodate the thermal expansion differences between the two substrates, preventing direct stress transmission that would cause delamination and cracking.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The thermal expansion coefficient parameter is managed by selecting an adhesive layer with appropriate thermal expansion properties that bridge the gap between two substrates with different thermal expansion coefficients. This parameter matching reduces thermal stress during temperature changes.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If substrates of different materials are joined, then miniaturization is achieved, but manufacturing error rate increases due to thermal stresses

Engineering Contradiction:

Improvedevice sizeVSAvoidfabrication error rate

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The adhesive layer serves as a stress-absorbing intermediary that prevents thermal expansion mismatches from causing manufacturing defects. By decoupling the two substrates through this compliant layer, the structure tolerates dimensional changes without creating cracks or delamination during fabrication.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The adhesive layer is pre-applied between substrates before final assembly, providing a cushioning effect that anticipates and absorbs future thermal stresses. This preventive measure ensures that even when temperature fluctuations occur during manufacturing, the bonded structure remains intact without developing defects.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Strength

If rigid bonding is used between substrates, then structural strength is improved, but thermal stress causes cracking and delamination

Engineering Contradiction:

Improvebond strengthVSAvoidthermal stress damage

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The adhesive layer is implemented as a thin film that provides flexible bonding between substrates. This thin film structure maintains sufficient bond strength for structural integrity while its flexible nature allows it to deform with thermal expansion, preventing stress concentration that would lead to cracking.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The junction structure forms a composite material system combining the first substrate, adhesive layer, and second substrate. This composite structure leverages the complementary properties of each material: the substrates provide structural strength while the adhesive layer provides stress compliance, achieving both strength and thermal stress resistance simultaneously.

Inventive Principle:

Principle #40Composite materials

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 reduces delamination, warpage, and cracking, enhancing mechanical durability and electrical connectivity between substrates, thereby improving the fabrication yield and electric characteristics of devices.

Implementation Method 1

at least one of the adhesive layer or the insulation layer comprises an organic material

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

One of the first and second substrates has a thermal expansion coefficient different than a thermal expansion coefficient of the other of the first and second substrates

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8890325B2Heterojunction structures of different substrates joined and methods of fabricating the same

Publication Date: 2014.11.18 SAMSUNG ELECTRONICS CO LTD

AI summary

In one embodiment, a heterojunction structure includes a first substrate; a second substrate comprising an electrode pad, the second substrate joined to the first substrate by an adhesive layer interposed between the first and second substrates, the first substrate and the adhesive layer having a via hole penetrating therethrough to expose a region of the electrode pad; a connection electrode disposed in the via hole and contacting the electrode pad; and an insulation layer electrically insulating the connection electrode from the first substrate. One of the first and second substrates has a thermal expansion coefficient different than a thermal expansion coefficient of the other of the first and second substrates, and at least one of the adhesive layer or the insulation layer comprises an organic material.