Carbon Content Detection in Silicon via Polyatomic Complexes
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Solution Overview
Problem
Conventional methods for determining carbon content in silicon samples, such as SIMS and FTIR, have limited sensitivity due to interference from carbon and silicon signals and inability to detect interstitial carbon atoms, making it difficult to achieve accurate doping profiles, especially in large-diameter silicon wafers.
Innovation Solution
Generating electrically active polyatomic complexes within the silicon sample, including carbon atoms, which are then detected using FTIR spectroscopy, allowing for indirect determination of carbon content and overcoming signal interference, thereby improving sensitivity by nearly an order of magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional FTIR method is used to detect carbon content, then substitutional carbon atoms can be detected, but the sensitivity is impaired by signal interference from carbon and silicon resonant frequencies
Solution Approach 1:
The patent introduces polyatomic complexes as intermediary structures that contain carbon atoms. These complexes create new vibrational modes at frequencies distinct from both carbon and silicon monatomic signals. By detecting the vibrational modes of these intermediary polyatomic complexes rather than direct carbon or silicon signals, the method resolves the spectral interference problem and achieves accurate carbon content measurement.
2Measurement precision
If conventional FTIR method is used, then substitutional carbon atoms can be detected, but interstitial carbon atoms remain undetected
Solution Approach 1:
The patent changes the detection parameter from direct carbon atom detection to detection of polyatomic complex vibrational modes. This parameter change enables the method to detect carbon atoms in various positions (substitutional and interstitial) because the polyatomic complexes formed during the measurement process involve carbon atoms regardless of their initial lattice position, thereby achieving comprehensive carbon content measurement.
3Measurement precision
If SIMS method is used to determine carbon content, then detection is possible, but the detection limit is too high for accurate doping profile control
Solution Approach 1:
The patent replaces the mass spectrometry-based SIMS method with a vibrational spectroscopy approach. Instead of detecting carbon atoms through mass-to-charge ratio analysis, the method detects polyatomic complexes through their vibrational modes in the infrared spectrum. This substitution enables significantly lower detection limits by exploiting the enhanced vibrational signal intensity of polyatomic complexes compared to individual atom signals.
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 method enables accurate detection of carbon content down to 5·10^14 cm^-3, enhancing the control of proton-induced doping profiles and addressing the limitations of conventional techniques.
Implementation Method 1
The sensitivity of FTIR is strongly impaired by the interference of the carbon (CS) and silicon (SiS) signals having nearly the same resonant frequencies
Implementation Method 2
Fourier Transform Infrared Spectroscopy) The sensitivity of FTIR is strongly impaired by the interference of the carbon (CS) and silicon (SiS) signals having nearly the same resonant frequencies
Data Source
AI summary
A method of determining the carbon content in a silicon sample may include: generating electrically active polyatomic complexes within the silicon sample. Each polyatomic complex may include at least one carbon atom. The method may further include: determining a quantity indicative of the content of the generated polyatomic complexes in the silicon sample, and determining the carbon content in the silicon sample from the determined quantity.