SOI Substrate Formation from Bulk Silicon with Buried Oxide Cavities
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional SOI substrate fabrication processes are costly and inconvenient for adjusting substrate parameters, limiting the practical application of SOI devices.
Innovation Solution
A method is developed to form SOI devices from bulk silicon substrates by creating a stack of heteroepitaxial and silicon epitaxial layers, forming trenches with isolation dielectrics, removing the heteroepitaxial layer to create cavities, and filling these with a buried oxide layer, thereby reducing fabrication costs and allowing flexible parameter adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional SOI substrate fabrication processes are used (bonding two bulk silicon substrates or uniform oxygen ion implantation), then SOI devices can be manufactured, but the fabrication cost becomes very high and substrate parameter adjustment becomes inconvenient
Solution Approach 1:
The patent divides the SOI substrate fabrication into segmented steps: forming a stack of bulk silicon substrate, heteroepitaxial layer, and silicon epitaxial layer; creating isolation trenches; selectively removing the heteroepitaxial layer to form cavities; and filling cavities with buried oxide layer. This segmentation allows independent control and adjustment of each layer's parameters, enabling flexible substrate parameter adjustment while using conventional bulk silicon substrates to reduce fabrication cost
Solution Approach 2:
The patent performs preliminary actions by first forming the complete stack structure with heteroepitaxial and silicon epitaxial layers on the bulk silicon substrate before creating the isolation trenches and removing the heteroepitaxial layer. This preliminary formation of the layered structure enables subsequent flexible parameter adjustments and reduces overall fabrication cost by using standard bulk silicon substrates
2Reliability
If conventional SOI substrate fabrication processes are used, then SOI devices can be manufactured, but the overall fabrication cost becomes very high
Solution Approach 1:
The patent uses a bulk silicon substrate as a disposable starting material that is readily available and inexpensive compared to pre-fabricated SOI substrates. The bulk silicon substrate serves its purpose as a foundation for building the SOI structure and can be processed using conventional, cost-effective manufacturing techniques, thereby reducing fabrication cost while maintaining SOI device performance
Solution Approach 2:
The patent enables parameter changes by allowing independent control of each layer's thickness and composition during the epitaxial growth process. The heteroepitaxial layer and silicon epitaxial layer can be grown with specific thicknesses and doping profiles, and the buried oxide layer can be formed with controlled thickness, enabling optimization of SOI device performance parameters while using low-cost bulk silicon substrates
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 method lowers the cost of SOI device fabrication and enables flexible adjustment of structural parameters, enhancing device performance.
Implementation Method 1
forming a stack of a heteroepitaxial layer and a silicon epitaxial layer above a surface of a bulk silicon substrate
Implementation Method 2
performing a first photolithography process on the stack to form a first trench exposing the bulk silicon substrate
Data Source
AI summary
A method of making a silicon-on-insulator (SOI) device from a bulk silicon substrate and an SOI device are disclosed. In the method, a stack of a heteroepitaxial layer and a silicon epitaxial layer are formed on a bulk silicon substrate, and a first photolithography process is performed on the stack to form a first trench exposing the bulk silicon substrate. The first trench is filled with a first isolation dielectric, and a second photolithography process is performed on the stack to form a second trench. The first isolation dielectric and the second trench isolate the stack. Subsequently, the heteroepitaxial layer is removed from the stack, forming at least one cavity. Moreover, the at least one cavity is filled with a buried oxide layer. The buried oxide layer and the silicon epitaxial layer overlying the buried oxide layer form SOI substrate structures. SOI devices are formed on the SOI substrate structures.