Epitaxial Silicon Buffer Layer for Arsenic Auto-Doping Suppression
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Solution Overview
Problem
Auto-doping, particularly Arsenic auto-doping, during epitaxial growth of Silicon layers on high-doping substrates leads to increased dopant concentration at the wafer edge, reducing breakthrough voltage and causing on-wafer inhomogeneity in semiconductor devices.
Innovation Solution
Incorporation of a high-doped Phosphorous-doped Silicon buffer layer between the substrate and epitaxy layers to suppress Arsenic diffusion, using a thickness of about 1 μm to 5 μm, which facilitates a sharp transition in doping profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-doping substrate layer is used to reduce resistivity, then electrical conductivity is improved, but Arsenic diffusion during epitaxial growth increases dopant concentration in the epitaxial layer, reducing breakthrough voltage and causing on-wafer inhomogeneity
Solution Approach 1:
A buffer layer is introduced as an intermediary between the high-doping substrate layer and the low-doping epitaxial layer. This buffer layer acts as a mediator that blocks Arsenic diffusion from the substrate to the epitaxial layer, preventing contamination while allowing the substrate to maintain its high conductivity. The buffer layer composition is selected to be compatible with both the substrate and epitaxial layer, creating a transition zone that resolves the contradiction between substrate doping and epitaxial layer purity.
Solution Approach 2:
The device structure is segmented into three distinct layers: the high-doping substrate layer, the intermediate buffer layer, and the low-doping epitaxial layer. This segmentation separates the conflicting requirements of high substrate doping (for conductivity) and low epitaxial doping (for breakthrough voltage), allowing each layer to independently fulfill its specific function without interfering with the other layers' performance characteristics.
2Stability of the object's composition
If thermal treatment is applied during epitaxial growth to facilitate crystal formation, then crystal quality is improved, but Arsenic out-diffusion from substrate increases, leading to higher dopant concentration in epitaxial layer
Solution Approach 1:
The buffer layer serves as a thermal barrier and diffusion blocker during thermal epitaxial growth. While the thermal treatment necessary for crystal formation proceeds, the buffer layer prevents Arsenic atoms from migrating from the substrate into the epitaxial layer, thus maintaining crystal quality without the harmful side effect of Arsenic contamination.
Solution Approach 2:
The buffer layer is prepared in advance before the epitaxial growth process begins. This preliminary structure is already in place to prevent Arsenic diffusion during the subsequent thermal treatment, proactively addressing the diffusion issue before it can affect the epitaxial layer composition.
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
The Phosphorous-doped buffer layer effectively minimizes Arsenic diffusion, ensuring consistent dopant concentration across the wafer, thereby maintaining stable breakthrough voltage and improving wafer yield in semiconductor devices.
Implementation Method 1
Incorporation of a high-doped Phosphorous-doped Silicon buffer layer between the substrate and epitaxy layers to suppress Arsenic diffusion
Implementation Method 2
An epitaxial layer can be grown or deposited on a substrate using a process called epitaxy. Epitaxy involves the deposition of a crystalline layer on top of a crystalline substrate, where the deposited atoms align with the atoms of the substrate to create a single crystal structure.
Implementation Method 3
As has a high vapor pressure, and during thermal treatments and epitaxial growth, the ions will out-diffuse from the substrate 101 and be re-deposited in the epitaxial layer(s) 103
Implementation Method 4
As has a high vapor pressure, and during thermal treatments and epitaxial growth, the ions will out-diffuse from the substrate 101
Data Source
AI summary
A semiconductor device has one or more substrate layers, one or more epitaxy layers positioned above the one or more substrate layers, and a buffer layer directly in between the one or more substrate layers and the one or more epitaxy layers. The substrate layer can be a high-doped Arsenic layer. The epitaxy layer can be low-doped. The buffer layer can be a highly Phosphorous-doped Silicon layer. The buffer layer can be relatively thin, about 1 μm to 5 μm. A method includes providing a substrate layer, creating a buffer layer on top of the substrate layer; and creating an epitaxy layer on top of the buffer layer.