Silicon Island Fabrication via Selective Oxidation
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Solution Overview
Problem
Conventional silicon island fabrication methods, such as the silicon-on-insulator (SOI) technique and polysilicon deposition, are associated with high process complexity, cost, and long manufacturing cycles due to accuracy limitations and the need for multiple chemical mechanical polishing (CMP) processes, which can lead to non-uniformity and adverse impacts on the performance of formed silicon islands.
Innovation Solution
A method involving the formation of first trenches in a silicon substrate, partial filling with an insulating material to create second trenches, deposition of a protective layer, oxidation of exposed silicon substrate portions, and filling the second trenches with an isolating material to form complete silicon islands, reducing the need for complex processes like ion implantation and substrate bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silicon island fabrication methods (SOI technique or polysilicon deposition with CMP) are used, then complete isolation between silicon islands is achieved, but process complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent extracts and eliminates the complex CMP processes and substrate flipping steps from the conventional fabrication method. By using a single-sided oxidation approach where oxide layers are grown directly on the silicon substrate surface and then removed only in trench regions, the method achieves complete isolation without requiring the complex multi-step CMP processes and substrate handling of conventional SOI or polysilicon deposition methods.
Solution Approach 2:
The patent replaces the mechanical CMP (chemical mechanical polishing) process with a chemical oxidation approach. Instead of mechanically removing material to achieve isolation, the method uses controlled chemical oxidation to grow oxide layers that define the isolation regions, followed by selective oxide removal. This substitution eliminates the accuracy limitations and uniformity controllability issues associated with CMP processes.
2Reliability
If multiple CMP processes are used to form silicon islands, then isolation is achieved, but manufacturing cycle time increases
Solution Approach 1:
The patent performs preliminary oxidation actions by growing oxide layers on the silicon substrate surface before defining the final isolation structures. The oxide layers are grown in advance and then selectively removed in trench regions, allowing the isolation structures to be formed in fewer subsequent steps. This preliminary oxidation action eliminates the need for multiple CMP processes and reduces the overall manufacturing cycle time.
Solution Approach 2:
The patent extracts and eliminates the time-consuming substrate flipping and second CMP process steps from the conventional fabrication method. By using a single-sided oxidation approach where all oxidation and isolation formation is completed on one side of the substrate, the method achieves complete isolation without requiring substrate flipping and additional CMP processes, thereby significantly reducing manufacturing cycle time.
3Reliability
If conventional polysilicon deposition and CMP methods are used, then silicon islands are formed, but uniformity controllability decreases due to CMP accuracy limitations
Solution Approach 1:
The patent replaces the mechanical CMP process with a chemical oxidation approach. Instead of relying on CMP accuracy to achieve uniform isolation, the method uses controlled chemical oxidation to grow oxide layers with precise thickness and uniformity. The oxidation process is inherently more controllable and reproducible than mechanical polishing, eliminating the accuracy limitations and uniformity controllability issues associated with CMP processes.
Solution Approach 2:
The oxidation process is self-regulating and self-limiting, where the oxide layer growth automatically stops when the desired thickness is achieved, providing inherent uniformity control. The oxide layers form uniformly across the substrate surface through controlled oxidation conditions, and the subsequent selective removal in trench regions automatically defines the isolation structures with high precision without requiring additional mechanical polishing steps.
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 allows for the formation of completely isolated silicon islands with reduced process complexity and cost, achieving properties similar to those formed by SOI techniques without additional complex processes, thereby simplifying and cost-effectively producing silicon island structures.
Implementation Method 1
depositing an insulating material, the insulating material at least filling bottom portions of some of the first trenches
Implementation Method 2
performing an oxidation process at portions of the silicon substrate exposed at sidewalls of the some of the first trenches until the portions of the silicon substrate between portions of the sidewalls of the first trenches that are not covered by the protective layer are completely oxidized, thereby forming an oxide layer
Data Source
AI summary
A silicon island structure and a method of fabricating same are disclosed. The method includes: forming multiple first trenches in a silicon substrate; forming second trenches by partially filling some of the first trenches with an insulating material; depositing a protective layer over the silicon substrate and over the second trenches; removing the protective layer over bottoms of the second trenches and the insulating material under the second trenches, thereby exposing sidewalls of some first trenches; oxidizing portions of the silicon substrate between the exposed sidewalls of the first trenches to form an oxide layer; removing the protective layer covering sidewalls of the second trenches; and filling the second trenches with an isolating material to form isolations, wherein portions of the silicon substrate between the isolations define silicon islands. This method enables the formation of silicon islands at desired locations with reduced process complexity and cost.