Ferroelectric Gate Stack for Band-to-Band Tunneling Control
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Solution Overview
Problem
Small band gap semiconductor material transistor devices face high leakage current issues due to band-to-band tunneling, which reduces gate control and makes it difficult to bias the device to an off-state, and existing high-k dielectric solutions increase carrier mobility but struggle with off-state leakage.
Innovation Solution
Incorporating a ferroelectric oxide layer in the gate stack that can switch between two ferroelectric states, reducing off-state leakage and increasing on-state charge by altering its effective thickness and dielectric constant in response to voltage, allowing for improved control over the channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If small band gap semiconductor material is used, then carrier mobility is improved, but off-state leakage current increases due to band-to-band tunneling
Solution Approach 1:
A ferroelectric layer is introduced as an intermediary between the gate electrode and the channel. This ferroelectric layer modulates the electric field in the channel through its switchable polarization states, enabling control of carrier transport while suppressing band-to-band tunneling in the off-state. The ferroelectric material acts as a mediator that decouples the direct relationship between gate voltage and channel field, allowing high mobility when needed while blocking leakage paths when off.
Solution Approach 2:
The invention changes the electrical parameters of the gate stack by incorporating a ferroelectric material with switchable polarization. By switching between positive and negative polarization states, the effective gate voltage and electric field in the channel are dynamically adjusted. This parameter change enables the system to achieve high carrier mobility in the on-state while creating a strong field barrier to suppress band-to-band tunneling in the off-state.
2Speed
If high-k dielectric is used to increase carrier mobility, then speed is improved, but off-state leakage control remains difficult
Solution Approach 1:
The gate stack is designed as a composite structure combining a high-k dielectric layer with a ferroelectric layer. The high-k dielectric provides the necessary capacitance and field enhancement for high carrier mobility, while the ferroelectric layer adds switchable polarization control. This composite material approach allows the system to benefit from both the high-k material's mobility enhancement and the ferroelectric material's leakage suppression capability.
Solution Approach 2:
The ferroelectric layer serves as an intermediary between the high-k dielectric and the channel. It modulates the electric field generated by the high-k dielectric, enabling the system to achieve high carrier mobility when the ferroelectric polarization aligns with the gate field, while suppressing band-to-band tunneling when the polarization opposes the gate field, thus controlling off-state leakage.
3Device complexity
If standard gate dielectric is used, then device structure is simple, but gate control over the channel is reduced
Solution Approach 1:
The gate stack is constructed as a composite structure with multiple functional layers: a gate dielectric layer for electrical isolation, a ferroelectric layer for field modulation and non-volatile state storage, and potentially a metal gate electrode. This composite structure provides superior gate control through the combined effects of dielectric isolation and ferroelectric field enhancement, enabling precise control of channel conductivity while maintaining a manufacturable multi-layer architecture.
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 ferroelectric gate stack significantly reduces off-state leakage and enhances on-state charge, leading to faster operating speeds and improved bias control in semiconductor transistor devices.
Implementation Method 1
Incorporating a ferroelectric oxide layer in the gate stack that can switch between two ferroelectric states, reducing off-state leakage and increasing on-state charge by altering its effective thickness and dielectric constant in response to voltage
Data Source
AI summary
Techniques are disclosed for an integrated circuit including a ferroelectric gate stack including a ferroelectric layer, an interfacial oxide layer, and a gate electrode. The ferroelectric layer can be voltage activated to switch between two ferroelectric states. Employing such a ferroelectric layer provides a reduction in leakage current in an off-state and provides an increase in charge in an on-state. The interfacial oxide layer can be formed between the ferroelectric layer and the gate electrode. Alternatively, the ferroelectric layer can be formed between the interfacial oxide layer and the gate electrode.