SOI Peripheral Oxide Encapsulation via Creep Thermal Treatment
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Solution Overview
Problem
Semiconductor-on-insulator (SOI) structures experience de-wetting and etching phenomena during thermal treatments, leading to defective regions and making them unfit for electronic component fabrication due to exposure of the buried oxide layer, especially at the periphery where the thin layer is thin and morphologically unstable.
Innovation Solution
A process involving a main thermal treatment in a neutral or controlled reducing atmosphere, with a step to cover the exposed peripheral oxide layer using a creep thermal treatment to ensure the semiconductor layer encapsulates the oxide, preventing de-wetting and etching by maintaining a sufficient thickness of the semiconductor layer to avoid exposure of the oxide layer during thermal dissolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal treatment is applied to dissolve the oxide layer, then the oxide layer thickness is reduced, but de-wetting and etching phenomena occur at the periphery where the thin layer is exposed
Solution Approach 1:
A creep thermal treatment is applied before the main dissolution thermal treatment to cause the semiconductor layer to creep and cover the exposed peripheral oxide layer. This preliminary action prevents the oxide from being exposed during subsequent dissolution, eliminating de-wetting and etching phenomena while allowing effective oxide thinning in the main treatment step.
2Manufacturing precision
If the thin layer thickness is reduced to enable oxide dissolution, then oxide layer can be dissolved more effectively, but the thin layer becomes morphologically unstable and exposes the buried oxide
Solution Approach 1:
The creep thermal treatment is performed in advance to increase the thin layer thickness at the periphery before the main dissolution treatment. This ensures the layer remains morphologically stable during oxide dissolution, preventing exposure of the buried oxide while still allowing effective oxide thinning through the thicker central regions.
Solution Approach 2:
The creep treatment creates a non-uniform thickness distribution in the semiconductor layer, with increased thickness at the periphery and maintained or reduced thickness in the center. This local quality variation allows the periphery to remain stable during dissolution while the center undergoes effective oxide thinning.
3Length of moving object
If the thin layer thickness is less than 100 nm, then the structure achieves desired thinness, but de-wetting phenomenon increases significantly during thermal treatment
Solution Approach 1:
The creep thermal treatment is applied beforehand to increase the thin layer thickness at the periphery where de-wetting is most problematic. This preliminary thickening provides sufficient mechanical stability to prevent de-wetting during the main dissolution treatment, while the overall structure maintains its desired thinness.
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 process effectively prevents de-wetting and etching phenomena, ensuring the SOI structure remains defect-free, particularly at the periphery, by maintaining the oxide layer's stability through controlled oxygen diffusion and encapsulation, thereby preserving the integrity of the substrate for electronic component fabrication.
Implementation Method 1
A creep thermal treatment is applied to a structure of semiconductor-on-insulator type successively comprising a carrier substrate, an oxide layer and a thin layer of semiconductor material
Implementation Method 2
apply thermal treatment to cause diffusion of at least part of the oxygen from the buried oxide layer through the thin semiconductor layer
Implementation Method 3
The application of this dissolution thermal treatment or of any other type of thermal treatment, such as surface smoothing or an epitaxy step, may cause a phenomenon of de-wetting
Data Source
AI summary
A process for avoiding formation of an Si—SiO2—H2 environment during a dissolution treatment of a semiconductor-on-insulator structure that includes a carrier substrate, an oxide layer, a thin layer of a semiconductor material and a peripheral ring in which the oxide layer is exposed. This process includes encapsulating at least the exposed oxide layer of the peripheral ring with semiconductor material by performing a creep thermal treatment; and performing an oxide dissolution treatment to reduce part of the thickness of the oxide layer. In this process, the semiconductor material that encapsulates the oxide layer has a thickness before the oxide dissolution that is at least twice that of the oxide that is to be dissolved, thus avoiding formation of an Si—SiO2—H2 environment on the peripheral ring where the oxide layer would otherwise be exposed.