Polysilicon Schottky Diode Barrier Height Optimization
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Solution Overview
Problem
High voltage silicon carbide (SiC) Schottky diodes face challenges in achieving a balance between low forward voltage drop and low reverse leakage current, with commonly used metals providing barrier heights of 0.8 eV or higher, which is inadequate for detecting low-level RF signals, particularly in RF limiter applications where a barrier height of 0.5 eV or less is required.
Innovation Solution
A hybrid semiconductor device is developed, incorporating a PIN diode portion and a Schottky diode portion on a semiconductor substrate, with a polysilicon layer acting as a Schottky contact, allowing for a barrier height of less than 0.8 eV, specifically between 0.2 eV to 0.5 eV, and including a SiC drift layer and P-type SiC layer with trenches to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low barrier height metal is used for the Schottky contact, then the forward voltage drop is reduced, but the reverse leakage current increases
Solution Approach 1:
The patent changes the material parameter of the Schottky contact from conventional metals (Cr, Ti) with barrier heights of 0.8 eV or higher to polysilicon with barrier heights of 0.5 eV or less. This parameter change in barrier height enables detection of low-level RF signals while maintaining acceptable reverse leakage characteristics through the specific polysilicon formulation and fabrication process.
2Object-generated harmful factors
If a high barrier height metal is used for the Schottky contact, then the reverse leakage current is reduced, but the forward voltage drop increases
Solution Approach 1:
The patent achieves a barrier height parameter of 0.5 eV or less by using polysilicon instead of conventional metals, which enables detection of low-level RF signals. This parameter change simultaneously improves both forward voltage drop and reverse leakage characteristics compared to traditional metal contacts.
3Reliability
If trench type Schottky diode structure is used, then the forward and reverse operational characteristics are improved, but the fabrication cost increases
Solution Approach 1:
The patent simplifies the device structure by eliminating the complex trench configuration while achieving the desired barrier height parameter of 0.5 eV or less through polysilicon material. This approach maintains improved operational characteristics while significantly reducing fabrication complexity and cost compared to trench type structures.
4Reliability
If trench type Schottky diode structure is used, then the forward and reverse characteristics are optimized, but the feature size limitations constrain performance
Solution Approach 1:
The patent changes the material parameter to polysilicon with barrier height of 0.5 eV or less, which eliminates the need for trench structures and high/low barrier metal lines. This simplifies the device geometry, removes feature size constraints, and maintains optimized forward and reverse characteristics.
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 hybrid semiconductor device achieves robust device performance with improved avalanche capability and high temperature stability, enabling the detection of smaller RF signals with a barrier height of 0.5 eV or less, surpassing the limitations of conventional SiC Schottky diodes.
Implementation Method 1
A Schottky barrier diode produces rectification as a result of nonlinear unipolar current transport across a metal semiconductor contact
Implementation Method 2
SiC PIN diodes are very attractive for RF limiter applications
Data Source
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AI summary
Hybrid semiconductor devices including a PIN diode portion and a Schottky diode portion are provided. The PIN diode portion is provided on a semiconductor substrate and has an anode contact on a first surface of the semiconductor substrate. The Schottky diode portion is also provided on the semiconductor substrate and includes a polysilicon layer on the semiconductor substrate and a ohmic contact on the polysilicon layer. Related Schottky diodes are also provided herein.