Controlled Substrate Spalling via Surface Step Region

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Solution Overview

Problem

Existing methods for controlled spalling of thin-film substrates struggle to control the depth and ease of crack initiation during the process, particularly when dealing with substrates containing materials of different fracture toughness.

Innovation Solution

A method is introduced where a surface step region is created within the substrate prior to forming a stressor layer, allowing for controlled crack initiation by forming substrates with varying fracture toughness materials and strategically placing a surface step region at the edges and front side, which dictates the crack propagation path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a controlled spalling process is used to remove material layers from substrates, then fabrication costs are reduced and substrate reuse is enabled, but the depth and ease of crack initiation cannot be controlled

Engineering Contradiction:

Improvefabrication cost reductionVSAvoidcrack initiation depth control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

A surface step region is formed within the substrate prior to formation of a stressor layer. This preliminary structural modification creates a predetermined location for crack initiation, enabling control over where and how cracks form during the spalling process, while maintaining the cost benefits of controlled spalling.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If materials with different fracture toughness are used in the substrate, then crack propagation can be controlled to occur only in specific materials, but the substrate structure becomes more complex

Engineering Contradiction:

Improvecrack propagation controlVSAvoidsubstrate structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The substrate is designed with different materials having different fracture toughness values at different locations. The surface step region is formed within a first material, and crack propagation is controlled to occur only in that first material rather than propagating into the second material with different fracture toughness properties.

Inventive Principle:

Principle #3Local quality

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 precise control over crack initiation and propagation, ensuring that cracks form only in the material with lower fracture toughness, facilitating efficient removal of the material layer while minimizing damage to the substrate, thereby reducing fabrication costs and enhancing the reuse of substrates.

Implementation Method 1

The presence of the surface step region within the surface portion of the substrate controls the depth and ease at which crack initiation occurs within the substrate

Methodology Applied

Scientific EffectStress concentration:

Implementation Method 2

A stressor layer is formed atop the front side of the substrate. A material layer is then removed from the substrate by spalling

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS9040432B2Method for facilitating crack initiation during controlled substrate spalling

Publication Date: 2015.05.26 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A method is provided in which a substrate including various materials of different fracture toughness (KIc) can be spalled in a controlled manner. In particular, a surface step region is formed within a surface portion of the substrate prior to formation of a stressor layer. The presence of the surface step region within the surface portion of the substrate controls the depth and ease at which crack initiation occurs within the substrate.