Thermal Oxidation Thinning for SOI BOX Layer Precision
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Solution Overview
Problem
The manufacture of Silicon-On-Insulator (SOI) semiconductor devices with multiple layers of different thicknesses is challenging due to high defect density at mask edge regions, misalignment issues, and the need for multiple implantation processes, which complicates the formation of patterned BOX structures and affects device performance.
Innovation Solution
A method involving thermal oxidation and annealing of SOI stacks to thin both silicon and oxide layers in selected regions, allowing for the formation of multilayer semiconductor structures with varying thicknesses, enabling the creation of SOI stacks with multiple regions of different silicon and oxide layer thicknesses, which can be fine-tuned for specific electronic devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation with patterned masks is used to form patterned BOX structures, then patterned BOX structures can be obtained, but defects form at high density at mask edge regions and misalignment occurs between different BOX layers
Solution Approach 1:
The patent removes the mask layer entirely from the process, replacing ion implantation with thermal oxidation. This extraction of the masking step eliminates the source of mask edge defects and misalignment, allowing direct thermal oxidation of silicon to form BOX layers without any physical mask boundaries that could cause defects.
Solution Approach 2:
The patent replaces the mechanical ion implantation process with a thermal field-based oxidation process. Instead of mechanically implanting ions through masks, the invention uses thermal energy to oxidize silicon in specific regions, substituting a mechanical system with a thermal field system that avoids mask-related defects.
2Adaptability or versatility
If multiple implantation processes with complementary masks are used to obtain BOX structures with two or more BOX thicknesses, then multiple thicknesses can be achieved, but the number of processing steps significantly increases
Solution Approach 1:
The patent applies local quality by creating different BOX thicknesses in different regions through selective thermal oxidation. By controlling which regions are exposed to oxidation conditions, the process achieves variable BOX thicknesses across the wafer in a single processing step, rather than requiring multiple global implantation steps.
Solution Approach 2:
The patent uses preliminary patterning of the silicon layer surface to define regions that will undergo thermal oxidation. This preliminary structural preparation allows subsequent thermal processing to directly create the desired multi-thickness BOX structure without requiring multiple sequential implantation and masking steps.
3Ease of manufacture
If conventional ion implantation is used to form BOX layers, then BOX structures can be created, but the process lacks flexibility for tuning layer thicknesses reliably
Solution Approach 1:
The patent changes the fundamental parameter from ion dose control to thermal oxidation time and temperature control. Thermal oxidation parameters (time, temperature, oxygen partial pressure) provide continuous and predictable control over oxide thickness, enabling reliable tuning of BOX layer thicknesses without the discrete steps inherent in ion implantation dosing.
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 approach allows for the reliable formation of SOI structures with varying layer thicknesses, providing more flexibility for device design, reducing processing steps, and improving device performance by enabling the formation of multiple device areas with different thicknesses on the same chip, thus enhancing the headroom for device integration.
Implementation Method 1
providing at least one first region of the SOI stack wherein the silicon layer is thinned by thermally oxidizing part of the silicon layer
Implementation Method 2
providing at least one second region of the SOI stack wherein the first oxide layer (BOX layer) is thinned by annealing
Data Source
AI summary
The present invention relates to a method for providing a Silicon-On-Insulator (SOI) stack that includes a substrate layer, a first oxide layer on the substrate layer and a silicon layer on the first oxide layer (BOX layer). The method includes providing at least one first region of the SOI stack wherein the silicon layer is thinned by thermally oxidizing a part of the silicon layer and providing at least one second region of the SOI stack wherein the first oxide layer (BOX layer) is thinned by annealing.