C-V Measurement Stabilization via Static Neutralization
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Solution Overview
Problem
The resistivity of single crystal silicon wafers measured using a mercury electrode tends to change over time, particularly when n-type wafers with low resistivity are oxidized with ozone gas, leading to unstable C-V characteristics.
Innovation Solution
A method that involves forming a thin oxide film on the wafer using ozone gas and then removing static electricity using a device that generates positive and negative ions to neutralize the surface charge, thereby stabilizing the depletion layer and reducing resistivity changes during repeated measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin oxide film is formed on the wafer using ozone gas, then measurement precision is improved, but static electricity accumulates on the wafer surface causing resistivity to change over time
Solution Approach 1:
The invention applies preliminary action by introducing a static electricity removal step immediately after oxide film formation and before C-V measurement. This preliminary removal of static charge prevents the subsequent drift in resistivity measurements, allowing stable measurements to be obtained while maintaining the benefits of oxide film formation.
Solution Approach 2:
The invention extracts the harmful static electricity component from the system by using a dedicated static electricity removal device. This separation allows the beneficial oxide film to remain on the wafer surface while removing only the detrimental static charge that causes measurement instability.
2Productivity
If repeated measurements are performed with a mercury electrode, then productivity is improved, but resistivity values drift and decrease over time
Solution Approach 1:
The invention implements self-service by enabling the measurement system to automatically remove static electricity between measurements without requiring external intervention or wafer reprocessing. This self-maintenance capability allows repeated measurements to be performed with consistent reliability, eliminating the progressive drift that previously occurred.
Solution Approach 2:
The invention maintains continuity of useful action by keeping the static electricity removal function active and available throughout the measurement sequence. This continuous capability ensures that each measurement in the repeated measurement series starts from a stable baseline, maintaining reliability across all measurements while preserving measurement efficiency.
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 allows for stable and consistent C-V characteristic measurements by minimizing the impact of static electricity on resistivity, maintaining measurement accuracy over time with a variation coefficient of 1% or less even at low resistivity levels.
Implementation Method 1
forming a thin oxide film on the wafer using ozone gas
Implementation Method 2
generates positive and negative ions to neutralize the surface charge
Implementation Method 3
removing static electricity using a device that generates positive and negative ions to neutralize the surface charge
Implementation Method 4
a Schottky barrier junction is formed on a surface of a single crystal silicon wafer to be measured
Implementation Method 5
a reverse bias voltage is applied thereto while the voltage is continuously varied to expand a depletion layer in the single crystal silicon wafer
Data Source
Figure 1~2
Figure 3(a)~5(b)
Figure 6(a)~7
AI summary
Proposed are a C-V characteristic measurement system and a method of measuring C-V characteristics that allow for less change in resistivity with time in repeated measurement of a single crystal silicon wafer using a mercury electrode, as compared to those in the related arts. Measurement is conducted with use of a C-V characteristic measurement system including: a mercury probe 30 for putting mercury as an electrode to contact with a single crystal silicon wafer; an LCR meter 40 for forming a depletion layer by supplying a high-frequency wave to the single crystal silicon wafer via the mercury probe 30 to apply a reverse bias voltage to the single crystal silicon wafer while measuring a capacitance of the depletion layer; analysis software for calculating C-V characteristics based on the reverse bias voltage and the capacitance of the depletion layer; and a static electricity removing device 20 for removing static electricity of the single crystal silicon wafer.