Semiconductor Doping Measurement via Constant Surface Potential Corona Charging
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Solution Overview
Problem
Current methods for measuring semiconductor doping concentrations are invasive, require permanent or temporary metal-semiconductor diodes, and often use hazardous materials like mercury, limiting their efficiency and environmental safety.
Innovation Solution
A non-contact method involving constant surface potential corona charging, where the semiconductor sample is biased to a target potential, and incremental corona charge is deposited, allowing for precise measurement of surface potential and capacitance changes without invasive contacts or hazardous materials, enabling accurate doping density determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive methods with metal-semiconductor diodes are used to measure doping concentration, then measurement precision can be achieved, but device complexity and use of hazardous materials increase
Solution Approach 1:
The patent extracts and eliminates the need for metal-semiconductor diodes and hazardous materials like mercury from the measurement system. By using non-contact corona charging to deposit charges on the semiconductor surface and measuring the resulting surface potential changes, the method achieves doping concentration measurement without invasive contacts or dangerous substances, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent replaces the mechanical/invasive contact-based measurement system (metal-semiconductor diodes) with a non-contact electrical field-based system (corona charging and surface potential measurement). This substitution eliminates the need for physical diode structures and hazardous materials while achieving the same measurement objective, thus reducing device complexity and improving safety
2Measurement precision
If incremental corona charge deposition is used, then electrostatic repulsion effects are reduced and measurement accuracy improves, but measurement time increases
Solution Approach 1:
The patent segments the charge deposition process into multiple incremental steps rather than applying a single large charge. By depositing small amounts of charge sequentially and measuring surface potential after each step, the method reduces electrostatic repulsion effects that would occur with large single-step charging. This segmentation improves measurement accuracy by maintaining better control over the electric field conditions at each measurement point
Solution Approach 2:
The patent employs periodic action by repeatedly cycling through the process of depositing a small amount of corona charge, waiting for charge stabilization, measuring the surface potential, and then proceeding to the next incremental charge deposition. This periodic measurement approach allows accurate capture of the capacitance-voltage relationship at multiple points, improving overall measurement precision while managing the time requirement through systematic repetition
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 method allows for fast, non-invasive, and accurate measurement of semiconductor doping concentrations without the need for metal-semiconductor diodes or mercury, reducing electrostatic repulsion effects and enabling quick processing of semiconductor wafers while providing precise doping depth profiles.
Implementation Method 1
depositing a monitored amount of corona charge (ΔQ 1 ) on the region of the surface
Implementation Method 2
determining the first capacitance value C 1 = ΔQ 1 /ΔV 1
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An example method of characterizing a semiconductor sample includes measuring an initial value, V in , of a surface potential at a region of a surface of the semiconductor sample, biasing the semiconductor sample to have a target surface potential value (V 0) of 2V or less, and depositing a monitored amount of corona charge (ΔQ 1) on the region of the surface after adjusting the surface potential to the target value. The method also includes measuring a first value, V 1, of the surface potential at the region after depositing the corona charge, determining the first change of surface potential (ΔV 1=V 1-V 0), and determining the first capacitance value C 1 =ΔQ 1/ ΔV 1, and characterizing the semiconductor sample based on V 0, V 1, ΔV 1, ΔQ 1 and C1.