Cavity SOI Substrate Warpage Reduction via Oxide Thickness
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Solution Overview
Problem
Cavity silicon-on-insulator (SOI) substrates experience warpage due to differences in thermal expansion coefficients between silicon and silicon oxide films, which existing techniques fail to adequately address.
Innovation Solution
A silicon substrate with a cavity is designed such that the thicknesses of silicon oxide films on its surfaces and the cavity bottom satisfy specific relations (d1≤d3 and d1<d2, or d3<d1 and d2<d1), reducing warpage by managing stress between the silicon and silicon oxide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cavity SOI substrate is constructed with silicon substrates and silicon oxide films, then the substrate can be used for MEMS devices, but warpage occurs due to differences in thermal expansion coefficients between silicon and silicon oxide films
Solution Approach 1:
The patent applies local quality by creating different silicon oxide film thicknesses at different locations on the silicon substrate. Specifically, a first silicon oxide film is formed on the first surface with thickness d1, a second silicon oxide film is formed on the cavity bottom with thickness d2, and a third silicon oxide film is formed on the second surface with thickness d3. The thickness relationships (d1≤d3 and d1<d2) are designed to locally compensate for thermal expansion differences, reducing warpage while maintaining substrate stability for MEMS applications.
2Shape
If existing techniques for reducing warpage are applied to cavity SOI substrates, then some warpage reduction may be achieved, but the techniques are not effective for cavity substrates
Solution Approach 1:
The patent applies parameter changes by modifying the thickness parameters of silicon oxide films at different locations. The specific thickness relationships (d1≤d3 and d1<d2) are designed to change the stress distribution parameters within the substrate. This approach effectively reduces warpage in cavity SOI substrates by adjusting the physical parameters of the oxide films to compensate for the cavity structure's impact on thermal expansion.
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 specified thickness relations of silicon oxide films on the silicon substrate with a cavity effectively reduce warpage, enhancing the stability and flatness of the substrate during thermal oxidation and bonding processes.
Implementation Method 1
warpage occurs in the silicon substrate having a cavity... due to differences in thermal expansion coefficients between silicon and silicon oxide films
Data Source
AI summary
A silicon substrate having a first silicon substrate having a first surface with a cavity and a second surface opposite the first surface; a first silicon oxide film having a thickness d1 on the first surface; a second silicon oxide film having a thickness d2 on a bottom of the cavity; and a third silicon oxide film having a thickness d3 on the second surface, where d1≤d3 and d1<d2, or d3<d1 and d2<d1.