Silicon Oxide Bonding Layer Microcavity Prevention
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Solution Overview
Problem
The formation of microcavities in deposited oxide layers during high-temperature treatments leads to delamination and deformation of thin films in composite structures, particularly when using sapphire substrates, which is a critical issue for epitaxial growth applications due to the temperature instability of deposited oxide layers compared to thermal oxides.
Innovation Solution
The use of a bonding layer of silicon oxide formed by low pressure chemical vapor deposition (LPCVD) with a thickness greater than or equal to the thin film, combined with a densification heat treatment, to prevent microcavity formation and ensure stability at high temperatures, thereby reducing thermal stress and plastic deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If deposited oxide layer is used for bonding, then bonding can be achieved on sapphire substrates, but microcavities form during high-temperature treatments causing delamination
Solution Approach 1:
The patent changes the physical and chemical parameters of the oxide layer by using thermal oxidation instead of deposition, and by controlling the thickness to be greater than or equal to the thin film thickness. This transformation from deposited to thermally grown oxide resolves the temperature stability issue while maintaining bonding capability.
Solution Approach 2:
The patent replaces the mechanical deposition process (CVD/PECVD) with a thermal-chemical process (thermal oxidation). This substitution creates a more stable oxide layer that resists microcavity formation during high-temperature treatments, eliminating the delamination problem.
2Reliability
If oxide layer thickness is increased to prevent microcavities, then temperature stability improves, but stress in bonding layer increases
Solution Approach 1:
The patent optimizes the thickness parameter of the oxide layer to be greater than or equal to the thin film thickness but not excessively thick. This controlled parameter change provides sufficient temperature stability while limiting stress accumulation in the bonding layer.
3Reliability
If thermal oxidation is used instead of deposition, then temperature stability improves, but compatibility with sapphire substrates decreases
Solution Approach 1:
The patent replaces deposition with thermal oxidation, which is compatible with sapphire substrates. The thermal oxidation process can directly oxidize sapphire surfaces to form stable oxide layers, maintaining substrate compatibility while achieving temperature stability.
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 prevents microcavity formation and delamination, allowing for the successful fabrication of composite structures that can withstand high temperatures, enabling stable epitaxial growth of semiconductor materials like GaN and other III/N materials without surface distortion or detachment.
Implementation Method 1
la couche de liaison en oxide de silicium est formée par dépôt en phase vapeur sous basse pression (LPCVD) d'une couche d'oxide sur la face de liaison du support et/ou sur la face de liaison du film mince
Implementation Method 2
un traitement de densification est porté sur la structure composite formée
Implementation Method 3
traitement de densification est porté sur la structure composite formée afin de densifier la couche d'oxide déposée
Data Source
AI summary
A method of preventing microcavity formation in a bonding layer of a composite structure resulting from creep and thermal expansion due to high temperature exposure of the composite structure. The method includes the steps of providing a thin film with a thickness of 5 micrometers or less; providing a bonding layer of oxide with a thickness that is equal to or greater than the thickness of the thin film with the bonding layer formed by low pressure chemical vapor deposition. The thin film or support substrate have a mean thermal expansion coefficient of 7×10−6 K−1 or more. The thin film, bonding layer and support substrate combine to reduce stress in and plastic deformation of the bonding layer during exposure to high temperatures of more than approximately 900° C. to thus prevent microcavities from appearing in the bonding layer.