Thick Silicon Oxide Inductors via Segmented Oxidation
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Solution Overview
Problem
Conventional silicon oxidation processes are inefficient in growing extremely thick layers of silicon oxide in short periods, leading to time-consuming processes and potential substrate degradation due to oxidation-induced stresses, which limits their application in high aspect ratio metal structures like inductors.
Innovation Solution
A method involving Deep Reactive Ion Etching (DRIE) and interlocking oxidation of textured silicon (ILOCTS) to grow very thick silicon dioxide layers, allowing for the embedding and protection of high aspect ratio metal structures, such as inductors, within a thermally grown SiO2 layer, using a substrate with a buried oxide layer to control lateral oxidation and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional silicon oxidation processes are used to grow thick silicon oxide layers, then the oxide layer thickness is increased, but the oxidation time becomes excessively long and substrate degradation occurs due to oxidation-induced stresses
Solution Approach 1:
The oxidation process is segmented into multiple stages with varying temperatures and atmospheres. The method uses low-temperature oxidation followed by high-temperature oxidation, dividing the thick oxide growth into manageable stages that reduce overall time while preventing substrate degradation
Solution Approach 2:
The oxidation parameters (temperature, atmosphere composition, pressure) are dynamically changed during the process. The method transitions from dry oxidation to wet oxidation, and adjusts temperature profiles to optimize growth rate at different stages, enabling thick oxide formation in reduced time
2Length of stationary object
If conventional silicon oxidation processes are used to grow thick silicon oxide layers, then the oxide layer thickness is increased, but oxidation-induced stresses cause substrate degradation
Solution Approach 1:
The method applies low-temperature oxidation first to create a thin initial oxide layer that acts as a stress buffer. This preliminary layer cushions the substrate against thermal and mechanical stresses that will occur during subsequent high-temperature thick oxidation, preventing degradation
Solution Approach 2:
Temperature and atmosphere parameters are carefully controlled and changed in specific sequences. The transition from dry to wet oxidation and controlled temperature ramping rates minimize thermal shock and stress accumulation, protecting the substrate from degradation
3Ease of manufacture
If conventional oxidation processes are used, then the process is simple, but the productivity is low due to long oxidation times
Solution Approach 1:
The oxidation process is made continuous through seamless transitions between different oxidation modes (dry to wet) and temperature stages. This continuous process eliminates idle time and maintains productive oxidation action throughout, significantly improving throughput while keeping the process relatively simple
Solution Approach 2:
By changing oxidation parameters (atmosphere, temperature, pressure) in a controlled sequence, the method achieves high productivity without requiring complex equipment. The parameter changes enable faster growth rates while maintaining process simplicity through standard furnace operations
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
Enables the growth of silicon oxide layers up to 500 microns thick in a short time, providing mechanical integrity and planar integration advantages for high aspect ratio metal structures, reducing oxidation time and stress-related issues, and enhancing the performance of embedded inductors.
Implementation Method 1
Deep Reactive Ion Etching (DRIE)
Implementation Method 2
interlocking oxidation of textured silicon (ILOCTS) to grow very thick silicon dioxide layers
Implementation Method 3
thermally grown SiO2 layer
Data Source
AI summary
A method is provided for fabricating thick silicon oxide structures, such as an embedded inductor. A Deep Reactive Ion Etch (DREI) etches the top silicon layer of a substrate to form high aspect ratio Si features, called trench texturing. The Si features are oxidized to form silicon oxide features. Adjacent Si features are separated by a trench width (S(0)), so that after oxidation, adjacent Si oxide features are formed separated by trench width (S(t)), where S(t)≤S(0) (e.g., S(t)=0). If the Si features have a width WSi(0)>1.2728 S(0), then the adjacent silicon oxide features form an amorphously merged silicon oxide feature with a planar top surface. The silicon oxide features have a height (HOX(t)) responsive to the trench width (S(0)), the Si feature width (WSi(t)), and the Si feature aspect ratio. After oxidation, inductor metal is deposited in trenches where WSi(0)<1.2728 S(0).