U-Shaped Ferroelectric Layer for Semiconductor Rdson-Vbr Tradeoff
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Solution Overview
Problem
Medium-voltage to high-voltage semiconductor devices face a challenge in achieving high breakdown voltage (Vbr) while maintaining low on-resistance (Rdson), as reducing parasitic resistance in the n-type drift region leads to performance degradation due to increased external resistance.
Innovation Solution
A U-shaped ferroelectric material layer is formed below a field plate, using materials like hafnium silicon oxide, hafnium zirconium oxide, or barium titanate, and filled with metal to enhance the surface electric field modulation and resistance, thereby reducing Rdson and increasing Vbr.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping in the n-type drift region is lowered to reduce the electric field for achieving higher breakdown voltage, then the breakdown voltage increases, but the parasitic external resistance increases causing performance degradation
Solution Approach 1:
A ferroelectric material layer is formed in advance below the field plate structure, positioned to overlap with the n-type drift region. This preliminary placement of the ferroelectric layer enables it to modulate the surface electric field before the device operates, thereby reducing the parasitic external resistance without compromising the breakdown voltage achieved through light doping.
Solution Approach 2:
The ferroelectric material layer acts as an intermediary between the light-doped n-type drift region and the metal field plate. By introducing this intermediate layer with high dielectric constant, the electric field distribution is modified, allowing the lightly doped region to maintain low parasitic resistance while still achieving high breakdown voltage.
2Reliability
If a field plate structure is added to reduce surface electric field, then the breakdown voltage increases, but the device complexity and manufacturing steps increase
Solution Approach 1:
The ferroelectric material layer is merged with the existing field plate structure, forming an integrated capacitor-like configuration below the field plate. This combination allows the ferroelectric layer to provide electric field modulation while sharing the same structural footprint as the field plate, thereby increasing breakdown voltage without proportionally increasing device complexity.
Solution Approach 2:
The introduction of the ferroelectric material layer changes the dielectric parameter in the field plate region. By utilizing the high dielectric constant of the ferroelectric material, the electric field is effectively modulated without requiring additional structural elements, thus improving breakdown voltage while maintaining relatively simple device architecture.
3Reliability
If additional processing steps are introduced to form the ferroelectric layer, then the Rdson-Vbr performance improves, but the manufacturing cost and process complexity increase
Solution Approach 1:
The ferroelectric material layer is formed as a preliminary step in the device fabrication process, utilizing atomic layer deposition (ALD) technology. By performing this step early in the manufacturing sequence, the ferroelectric layer is integrated into the device structure before subsequent processing steps, allowing for optimized process flow and reduced overall manufacturing complexity despite the addition of the ferroelectric deposition step.
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 significantly amplifies voltage by up to 25% to reduce the surface electric field in the off-state and decreases Rdson in the on-state, achieving improved Rdson-Vbr performance with minimal additional processing costs.
Implementation Method 1
forming a U-shaped ferroelectric material layer below a field plate... significantly amplifies voltage by up to 25% to reduce the surface electric field in the off-state and decreases Rdson in the on-state
Data Source
AI summary
Methods of forming a ferroelectric material layer below a field plate for achieving increased Vbr with reduced Rdson and resulting devices are provided. Embodiments include forming a N-Drift in a portion of the Si layer formed in a portion of a p-sub; forming an oxide layer over portions of the Si layer and the N-Drift; forming a gate over a portion of the oxide layer; forming a S/D extension region in the Si layer; forming first and second spacers on opposite sides of the gate and the oxide layer; forming a S/D region in the Si layer adjacent to the S/D extension region and a S/D region in the N-Drift remote from the Si layer; forming a U-shaped ferroelectric material layer over the oxide layer and the N-Drift, proximate or adjacent to the gate; and filling the U-shaped ferroelectric material layer with a metal, a field gate formed.