VV Defect Evaluation in Silicon Substrates
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Solution Overview
Problem
The evaluation of VV defects formed by particle beam irradiation in silicon single crystal substrates is challenging due to their difficulty in quantitative assessment compared to carbon-related defects, which affects the control of carrier lifetime in semiconductor devices.
Innovation Solution
A method involving measuring the resistivity of the silicon single crystal substrate before and after particle beam irradiation, calculating the rate of change in carrier concentration, and using this change to evaluate the concentration of VV defects, which are comprised of silicon atom vacancies, formed by the irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If particle beam irradiation is performed to form VV defects in silicon single crystal substrate, then carrier lifetime can be controlled, but the concentration of VV defects is difficult to evaluate quantitatively
Solution Approach 1:
The patent uses photoluminescence intensity as an intermediary parameter to indirectly measure VV defect concentration. Instead of directly counting defects, the method measures the light emission intensity which is influenced by both VV defects and oxygen concentration, then uses this intermediary measurement to evaluate the defect concentration through established relationships.
Solution Approach 2:
The patent changes the measurement parameter from direct structural analysis to optical property measurement. By measuring photoluminescence intensity (an optical parameter) instead of directly analyzing defect structure, the method enables quantitative evaluation of VV defect concentration that was previously difficult to achieve.
2Measurement precision
If conventional evaluation methods like CL are used for carbon-related defects, then quantitative evaluation is possible, but these methods cannot effectively evaluate VV defects
Solution Approach 1:
The patent makes the photoluminescence measurement method universal by showing it can evaluate multiple types of defects (both carbon-related defects and VV defects) using the same measurement approach. The method adapts to different defect types by analyzing the photoluminescence characteristics under various conditions, expanding the evaluation range beyond what conventional methods can achieve.
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 a simple and effective evaluation of VV defect concentration, enabling the determination of required irradiation quantities and crystal quality to control the lifetime of silicon single crystal substrates to a desired value.
Implementation Method 1
irradiation with an electron beam or various particle beams such as a proton beam and a helium ion beam can be performed in order to control their carrier lifetime
Implementation Method 2
the defects due to interstitial carbons such as CiOi and CiCs can be detected by photoluminescence (PL)
Implementation Method 3
There is an example to evaluate this defect by electron spin resonance (ESR) analysis
Data Source
AI summary
A method for evaluating concentration of defect in silicon single crystal substrate, defect being formed by particle beam irradiation in silicon single crystal substrate, including the steps of: measuring a resistivity of silicon single crystal substrate, followed by irradiating silicon single crystal substrate with particle beam, re-measuring resistivity of silicon single crystal substrate after irradiation; determining each carrier concentration in silicon single crystal substrate before and after irradiation on basis of measured results of resistivity before and after particle beam irradiation to calculate rate of change of carrier concentration; and evaluating concentration of VV defect on basis of rate of change of carrier concentration, VV defect being made of a silicon atom vacancy and being formed by particle beam irradiation in silicon single crystal substrate. The method can simply evaluate concentration of VV defect formed in silicon single crystal substrate by particle beam irradiation.