SOI Handle Wafer High Resistivity Region via Oxygen Diffusion
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Solution Overview
Problem
The challenge lies in reliably manufacturing silicon on insulator (SOI) structures with high resistivity handle wafers for RF applications, as existing methods face issues with dopant impurity variations, oxygen concentration, and surface inversion, leading to inconsistent performance and increased costs.
Innovation Solution
A method is developed to create a silicon-on-insulator structure with a handle wafer having a surface layer with a high resistivity region by selectively doping and manipulating the oxygen distribution within the handle wafer, forming a non-uniform oxygen distribution and thermal donor profile through diffusion processes, followed by annealing to achieve a resistivity peak in the surface layer, which is then bonded with a dielectric layer to form the SOI structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Czochralski method is used to produce high resistivity handle wafers, then RF power loss is reduced, but dopant impurity variations cause resistivity to shift from target value
Solution Approach 1:
The patent applies local quality by creating a high resistivity region specifically in the surface layer of the handle wafer through selective oxygen diffusion, rather than requiring uniform high resistivity throughout the entire wafer. This localized approach achieves the necessary RF performance while being less sensitive to bulk dopant variations.
Solution Approach 2:
The patent changes the approach from controlling dopant concentration to controlling oxygen concentration. By diffusing oxygen into the surface layer and forming thermal donors through annealing, the method achieves high resistivity (exceeding bulk resistivity) through a different physical parameter (oxygen content rather than dopant content), thereby avoiding dopant impurity issues.
2Reliability
If high resistivity handle wafers are used, then isolation properties are improved, but surface inversion layer forms near the dielectric layer
Solution Approach 1:
The patent creates a localized high resistivity region in the surface layer through oxygen diffusion, which provides the necessary isolation properties for RF applications. This localized treatment addresses the surface inversion issue by modifying only the critical region near the dielectric interface rather than requiring uniform high resistivity throughout the bulk.
Solution Approach 2:
The patent converts the harmful effect of oxygen (which can form thermal donors and affect resistivity) into a beneficial effect by deliberately introducing oxygen through diffusion and controlling its distribution. The oxygen, when properly distributed, creates the desired high resistivity profile without causing surface inversion.
3Device complexity
If thermal annealing process is used to form high resistivity substrates, then manufacturing complexity is reduced, but reliability and yield are insufficient
Solution Approach 1:
The patent performs preliminary oxygen diffusion into the handle wafer surface layer before the final device fabrication steps. This preliminary action ensures that the high resistivity region is already in place, which improves subsequent processing reliability and device yield without adding significant complexity to the overall manufacturing flow.
Solution Approach 2:
The patent modifies the thermal annealing process parameters to simultaneously achieve oxygen diffusion and thermal donor formation. By optimizing temperature and time parameters, the method creates the desired high resistivity profile in a single integrated process step rather than requiring multiple separate 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 approach enhances the reliability and yield of SOI structures for RF applications by achieving a consistent high resistivity profile, reducing harmonic distortion, and preventing surface inversion, thereby improving device performance and manufacturing efficiency.
Implementation Method 1
a high resistivity region is formed in the surface layer of the handle wafer in which the resistivity exceeds the resistivity of the handle wafer in the wafer bulk by diffusing oxygen either into or out of the handle wafer to form a non-uniform distribution of oxygen in the handle wafer
Implementation Method 2
annealing the wafer having a non-uniform distribution of oxygen to form a non-uniform distribution of thermal donors
Data Source
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AI summary
Silicon on insulator structures having a high resistivity region in the handle wafer of the silicon on insulator structure are disclosed. Methods for producing such silicon on insulator structures are also provided. Exemplary methods involve creating a non-uniform thermal donor profile and/or modifying the dopant profile of the handle wafer to create a new resistivity profile in the handle wafer. Methods may involve one or more SOI manufacturing steps or electronic device (e.g., RF device) manufacturing steps.