Optical Characteristics Measuring Device Using Microwave-Induced Photoconductivity
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Solution Overview
Problem
Existing optical characteristics measuring devices face challenges in accurately measuring materials with varying film thickness and shape, particularly in miniaturized semiconductor devices, as they require electrodes for measurement, limiting sample size and shape flexibility.
Innovation Solution
An optical characteristics measuring device that uses a combination of a light source and a microwave source to calculate a parameter related to electrical conductivity without electrodes, allowing for non-contact measurement across different film thicknesses and shapes by controlling light intensity and wavelength to achieve a predetermined parameter value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spectroscopic ellipsometer is used to measure optical characteristics by reflected light, then the measurement method is non-contact, but the measurement accuracy sharply decreases when the film thickness decreases in miniaturized semiconductor devices
Solution Approach 1:
The invention changes the measurement parameters by using microwave frequency electromagnetic waves instead of visible light, and by measuring absorption characteristics rather than reflected light characteristics. This parameter change enables accurate measurement of thin films that are too thin for conventional reflected light methods to detect accurately.
2Measurement precision
If the constant photocurrent method (CPM) is used to measure optical characteristics regardless of film thickness, then the measurement accuracy is maintained, but the sample size increases and the sample shape is limited due to the requirement of providing a plurality of electrodes on the material film
Solution Approach 1:
The invention extracts and eliminates the electrodes from the measurement system. By using microwave absorption measurement, the method no longer requires electrodes to be placed on the sample, thereby removing the constraints on sample size and shape while maintaining measurement accuracy.
Solution Approach 2:
The invention replaces the mechanical electrode contact system with a non-contact microwave measurement system. This substitution eliminates the need for physical contact with the sample, allowing measurement of samples with various sizes and shapes without modification.
3Measurement precision
If the constant photocurrent method (CPM) is used to measure the current flowing in the material film, then the optical characteristics can be measured regardless of film thickness, but an additional step of forming electrodes on the sample is required
Solution Approach 1:
The invention extracts and removes the electrode formation step from the measurement process. By using microwave absorption measurement, the complex process of forming and connecting electrodes is completely eliminated, simplifying the measurement process while maintaining accuracy.
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, non-contact measurement of optical characteristics regardless of sample size and shape, effectively addressing the limitations of existing technologies by indirectly assessing electrical conductivity changes through the parameter ΔP/P, facilitating the analysis of thin films on semiconductor substrates.
Implementation Method 1
A second light source is capable of irradiating the sample with microwaves. A measuring device measures microwave power of reflected waves of the microwaves reflected by the sample
Implementation Method 2
A first light source is capable of irradiating a sample with light... A calculation unit calculates a parameter relating to electrical conductivity of the sample by using the microwave power of the reflected waves
Data Source
AI summary
An optical characteristics measuring device includes a first light source capable of irradiating a sample with light and a second light source capable of irradiating the sample with microwaves. A measuring device measures microwave power of the reflection of the microwaves from the sample. A calculation unit calculates a parameter relating to the electrical conductivity of the sample using the microwave power of the reflected waves measured by the measuring device. A control unit controls the intensity of the light of the first light source so that the parameter becomes approximately a predetermined value. The calculation unit specifies first to n-th intensities of the light at which the parameter becomes approximately the predetermined value for each of the first to n-th wavelengths of the light and obtains relationships between the first to n-th wavelengths and the first to n-th intensities corresponding to the respective first to n-th wavelengths.