Silicon Oxide Bonding Layer for Low-Distortion Piezoelectric Bonding
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Solution Overview
Problem
High frequency distortion occurs in bonded bodies of piezoelectric material substrates and silicon substrates due to fixed charges at the interface, which is influenced by the quality of the silicon oxide film, and existing methods do not effectively control or suppress this distortion.
Innovation Solution
A bonded body is created using a silicon oxide bonding layer with a refractive index between 1.468 and 1.474, formed through reactive ion sputtering with a specific inert gas to oxygen gas flow rate ratio of 1.5 to 2.0, which reduces high frequency distortion by controlling the oxygen content in the film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a silicon oxide film is formed on the piezoelectric material substrate to enable bonding with silicon substrate, then bonding can be performed at relatively low temperature (400°C) through plasma activation method, but high frequency distortion appears due to fixed charge generated at the SiO2 film and Si wafer interface
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive index of the silicon oxide film (1.468-1.474) and the oxygen ratio during film formation (1.5-2.0). These parameter adjustments optimize the film quality to reduce fixed charge at the interface, thereby suppressing high frequency distortion while maintaining low temperature bonding capability
Solution Approach 2:
The patent applies local quality by creating a silicon oxide film with specific local properties (refractive index between 1.468-1.474) at the bonding interface. This localized optimization of film quality directly addresses the interface region where fixed charge generates distortion, without affecting other parts of the device
2Quantity of substance
If the oxygen ratio of the SiO2 film is lowered to change film quality, then the amount of fixed charge is increased, but this approach does not effectively suppress high frequency distortion
Solution Approach 1:
The patent applies parameter changes by inverting the conventional approach: instead of lowering the oxygen ratio, it optimizes the oxygen ratio to achieve a refractive index of 1.468-1.474. This optimized parameter range reduces fixed charge at the interface and effectively suppresses high frequency distortion
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 method effectively suppresses high frequency distortion in bonded bodies by adjusting the refractive index of the silicon oxide film, improving the bonding quality and reducing fixed charges at the interface.
Implementation Method 1
growing a bonding layer comprising silicon oxide on a surface of a supporting substrate comprising silicon by reactive ion sputtering method
Implementation Method 2
reactive ion sputtering method which is performed with at least an inert gas and oxygen gas
Data Source
AI summary
A bonded body has a supporting substrate composed of silicon, a piezoelectric material substrate, and a bonding layer provided on a surface of the supporting substrate and composed of silicon oxide. The bonding layer has a refractive index of 1.468 or higher and 1.474 or lower.