Corona-Kelvin Metrology for Interface Trap Density
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Solution Overview
Problem
Existing methods for determining interface trap charge and density at semiconductor-dielectric or semiconductor-oxide interfaces, particularly for wide bandgap semiconductors like SiC, face challenges due to slow recovery times after illumination, making it difficult to modulate contact potential difference voltage and determine surface barrier potential accurately.
Innovation Solution
A non-contact method using the Corona-Kelvin metrology that determines the surface barrier voltage and interface trap density by analyzing voltage-charge characteristics in the dark, independent of light modulation, and calculates the flatband voltage and interface trap density spectrum using corona charge injection and Kelvin probe measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light modulation is used to determine surface barrier potential and interface trap density, then measurement capability is improved, but recovery time becomes too slow for wide bandgap semiconductors like SiC
Solution Approach 1:
The patent extracts the illumination step from the measurement process entirely. Instead of using light modulation to determine surface barrier potential and interface trap density, the method performs all measurements in the dark by injecting corona charge and monitoring voltage-charge characteristics. This eliminates the recovery time bottleneck while maintaining measurement capability.
Solution Approach 2:
The patent replaces the optical measurement system (light modulation and detection) with an electrical charge injection system. Corona charge is injected onto the dielectric surface, and the resulting voltage-charge characteristics are measured electrically in the dark, substituting optical effects with electrical effects to achieve the same measurement goals without the recovery time penalty.
2Ease of operation
If corona charge is injected to determine interface trap charge, then non-contact measurement is achieved, but accurate determination of flatband voltage becomes difficult without light modulation
Solution Approach 1:
The patent introduces corona charge as an intermediary to establish the flatband condition. By injecting positive corona charge onto the dielectric surface and monitoring the voltage-charge characteristics in the dark, the method creates an electrical intermediary pathway to determine flatband voltage without requiring optical modulation, thus maintaining non-contact measurement while achieving accurate flatband determination.
3Measurement precision
If traditional Corona-Kelvin metrology with light modulation is used, then surface barrier potential can be determined, but the method fails for wide bandgap semiconductors due to slow recovery
Solution Approach 1:
The patent changes the fundamental measurement parameters by eliminating illumination entirely and performing all measurements in the dark. By injecting corona charge and monitoring voltage-charge characteristics without light, the method adapts the Corona-Kelvin metrology to work with wide bandgap semiconductors like SiC, GaN, and GaAs, which have inherently slow recovery times after illumination. This parameter change extends the versatility of the measurement technique to materials previously unsuitable for this approach.
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
Enables accurate determination of interface trap charge and density without rapid light modulation, suitable for wide bandgap semiconductors like SiC, allowing for improved characterization and monitoring of semiconductor-dielectric interfaces.
Implementation Method 1
Corona ions may be generated from air by the application of high voltage to fine wires and sharp electrode tips
Implementation Method 2
monitoring the surface voltage change with a vibrating Kelvin probe
Data Source
AI summary
Embodiments of the subject method and apparatus relate to a sequence of noncontact Corona-Kelvin Metrology that allows the determination and monitoring of interface properties in dielectric/wide band gap semiconductor structures. The technique involves the incremental application of precise and measured quantities of corona charge, QC, onto the dielectric surface followed by determination of the contact potential difference, VCPD, as the material structure response. The V-Q characteristics obtained are used to extract the surface barrier, VSB, response related to the applied corona charge. An intersection of the VCPD-QC characteristic obtained in the dark with the VOX-QC characteristic representing the dielectric response is determined. The specific VSB-QC dependence surrounding the reference VFB value is obtained and the dielectric interface trap density and its spectrum is determined. A method and apparatus to quantify and separate trapped charge components is provided.