Radiation-Induced Structural Changes in Semiconductor Metrology
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Solution Overview
Problem
Conventional metrology techniques struggle to accurately determine the properties of structures when the inspection radiation causes changes in the structure during measurement, leading to inaccuracies in reconstruction and other measurement methods.
Innovation Solution
A method and apparatus that simulate the interaction of radiation with a structure, accounting for changes caused by the inspection radiation during the exposure period by defining variable parameters, including time-related parameters, to determine the parameter of interest accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inspection radiation is used to measure structure properties, then measurement speed and throughput are improved, but the structure changes during exposure causing measurement inaccuracy
Solution Approach 1:
The patent applies preliminary action by calculating and applying a correction factor before final measurement interpretation. The system pre-characterizes the radiation-induced changes in the resist material and uses this information to correct the measured spectra, thereby compensating for structural changes that occur during exposure and maintaining measurement accuracy despite continuous irradiation
Solution Approach 2:
The patent implements feedback by using the measured spectra to iteratively refine the determination of structure properties. The system continuously compares measured spectra with simulated spectra, adjusts parameters, and recalculates until convergence is achieved, allowing accurate measurement even as the structure evolves during exposure
2Measurement precision
If shorter wavelength radiation (UV, DUV, x-ray) is used for inspection, then measurement precision is improved, but radiation-induced structural changes are enhanced
Solution Approach 1:
The patent converts the harmful effect of radiation-induced structural changes into a beneficial measurement tool. By characterizing how the resist material changes under radiation and incorporating this into the simulation models, the system uses the very changes that degrade measurement accuracy as additional information to refine the determination of initial structure properties
Solution Approach 2:
The patent applies parameter changes by adjusting the simulation models to account for radiation-induced modifications in the resist material's optical and physical properties. The system varies parameters such as refractive index, absorption coefficient, and layer thickness in the simulation to match the radiated state, enabling accurate interpretation of spectra despite structural evolution
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 enhances the accuracy of structure property determination by accounting for radiation-induced changes, ensuring that measurements reflect the structure's initial state, improving the precision of metrology results.
Implementation Method 1
measure one or more properties of the scattered radiation as it is reflected and/or transmitted by the target
Implementation Method 2
measure one or more properties of the scattered radiation as it is reflected and/or transmitted by the target
Implementation Method 3
Scattering of electromagnetic waves can be simulated by use of Maxwell's equations at such short wavelengths in the same way as at longer wavelengths
Data Source
AI summary
A structure of interest (T) is irradiated with radiation for example in the x-ray or EUV waveband, and scattered radiation is detected by a detector (19, 274, 908, 1012). A processor (PU) calculates a property such as linewidth (CD) or overlay (OV), for example by simulating (S16) interaction of radiation with a structure and comparing (S17) the simulated interaction with the detected radiation. The method is modified (S14a, S15a, S19a) to take account of changes in the structure which are caused by the inspection radiation. These changes may be for example shrinkage of the material, or changes in its optical characteristics. The changes may be caused by inspection radiation in the current observation or in a previous observation.