Oxygen-Doped Si Diffusion Barrier for Vertical Power Devices
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Solution Overview
Problem
As trench-based transistors shrink, the highly-doped source/body contact's lateral diffusion affects the threshold voltage and on-state resistance, leading to increased drain-induced barrier lowering, necessitating better control over the lateral out-diffusion of doping to maintain device performance.
Innovation Solution
A diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si is introduced between the highly doped body contact and the channel region, limiting lateral out-diffusion and improving control over the source/body contact doping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source/body contact is highly doped to reduce contact resistance, then the contact resistance decreases, but the lateral out-diffusion of doping increases causing higher threshold voltage and on-state resistance
Solution Approach 1:
An intermediate diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si is introduced between the highly doped source/body contact and the channel region. This intermediary layer prevents direct interaction between the high doping concentration and the channel, blocking lateral out-diffusion while allowing the contact to remain highly doped for low contact resistance
Solution Approach 2:
The diffusion barrier structure uses a composite material system with alternating layers of pure Si and oxygen-doped Si. The oxygen-doped Si layers provide enhanced diffusion barrier properties compared to pure Si, creating a multi-functional composite structure that simultaneously provides mechanical support and doping diffusion prevention
2Manufacturing precision
If the distance between the source/body contact and the channel region is increased to reduce lateral out-diffusion, then the doping control improves, but depletion of the body at high drain voltages increases causing higher DIBL
Solution Approach 1:
The diffusion barrier structure acts as an intermediary that enables close spacing between the source/body contact and channel region while preventing harmful lateral out-diffusion. This allows the contact to be positioned close to the channel for reduced body depletion and lower DIBL, while the barrier prevents doping contamination that would otherwise require larger spacing
3Reliability
If the process window variation for trench width and contact width is reduced to avoid adverse effects, then the device performance stability improves, but the manufacturing complexity increases
Solution Approach 1:
The diffusion barrier structure serves as a process buffer that decouples the critical dimensions of the contact and trench from the final doping distribution. By introducing this intermediate layer, the patent reduces sensitivity to process variations in trench width and contact width, allowing larger process windows while maintaining stable device performance
Solution Approach 2:
The diffusion barrier structure provides beforehand cushioning against process variations by pre-establishing a controlled interface between the highly doped contact and the channel region. This pre-engineered barrier compensates for potential variations in subsequent processing steps, cushioning the device performance against dimensional variations
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 solution reduces the threshold voltage and on-state resistance distributions, enhances charge carrier mobility, and decreases gate leakage, while improving gate reliability compared to conventional silicon epitaxial layers.
Implementation Method 1
a diffusion barrier structure extending along at least part of the channel region and disposed between the channel region and the highly doped body contact region, the diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si
Implementation Method 2
forming the diffusion barrier structure comprises: after etching the gate trench into the Si substrate and before forming the gate electrode and the gate dielectric in the gate trench, epitaxially growing the alternating layers of Si and oxygen-doped Si on a preliminary gate trench sidewall of the gate trench
Data Source
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AI summary
A semiconductor device includes a gate trench extending into a Si substrate, the gate trench including a gate electrode and a gate dielectric separating the gate electrode from the Si substrate. The semiconductor device further includes a body region in the Si substrate adjacent the gate trench, a channel region which extends along a sidewall of the gate trench, a source region in the Si substrate above the body region, a contact trench extending into the Si substrate and filled with an electrically conductive material which contacts the source region and a highly doped body contact region at a bottom of the contact trench, and a diffusion barrier structure extending along part of the channel region and disposed along a sidewall of the gate trench and between the channel region and the highly doped body contact region. The channel region, the gate electrode and the gate dielectric extend deeper into the Si substrate deeper than the diffusion barrier structure. The diffusion barrier structure includes alternating layers of Si and oxygen-doped Si.