Raman Shift Separation for Silicon Microbeam Stress and Temperature
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Solution Overview
Problem
Current methods for measuring thermal and mechanical properties of microscale silicon structures simultaneously are limited by their inability to separate stress-induced and temperature-induced Raman shifts, which affects the accurate determination of thermal conductivity and mechanical stress, particularly at high temperatures and strains.
Innovation Solution
The use of Raman spectroscopy to separate stress-induced and temperature-induced Raman shifts in silicon microbeams under uniaxial compressive load, allowing for the simultaneous measurement of thermal conductivity and mechanical stress, employing an electromagnetic actuator for nanomechanical stress amplification and precise temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Raman spectroscopy is used to measure both thermal and mechanical properties, then measurement capability is improved, but the ability to separate stress-induced and temperature-induced Raman shifts deteriorates
Solution Approach 1:
The patent segments the Raman shift measurement into two distinct components: stress-induced Raman shift and temperature-induced Raman shift. By performing separate measurements under controlled conditions (one with stress applied at constant temperature, another with temperature varied at constant stress), the methodology isolates and quantifies each effect independently, resolving the contradiction between comprehensive measurement capability and separation accuracy
Solution Approach 2:
The patent introduces an intermediary approach by using the known relationship between Raman shift and temperature (calibrated separately) as a mediator to subtract the temperature effect from the combined measurement. This intermediary temperature calibration curve enables the extraction of pure stress-induced Raman shift from the composite signal, achieving precise separation while maintaining versatile measurement capability
2Productivity
If simultaneous measurement of thermal and mechanical properties is performed, then measurement efficiency is improved, but measurement accuracy deteriorates due to interference between stress and temperature effects
Solution Approach 1:
The patent applies preliminary action by performing separate calibration measurements before the simultaneous measurement. First, the temperature-induced Raman shift is calibrated at constant stress. Then, the stress-induced Raman shift is measured at constant temperature. These preliminary separate measurements enable accurate decomposition during simultaneous measurement, resolving the contradiction between efficiency and accuracy
Solution Approach 2:
The methodology implements feedback by using the temperature measurement result to correct the stress measurement. The measured temperature is fed back into the temperature-induced Raman shift model, and this calculated shift is subtracted from the total Raman shift to obtain the accurate stress-induced component. This feedback mechanism maintains high accuracy while enabling simultaneous measurement
Data Source
AI summary
Embodiments of the present disclosure include separating a measured Raman shift signal into mechanical and thermal components when a uniaxial compressive load is applied in situ. In some embodiments, in situ uniaxial compressive loads are applied on examined specimens from room temperature to 150° C. In alternate embodiments, Raman shift measurements are performed as a function of strain at constant temperature and/or as a function of temperature at constant strain levels. It was realized that the Raman shift measured at a given temperature under a given level of applied stress can be expressed as a summation of stress-induced Raman shift signal and temperature-induced Raman shift signal measured separately. Such a separation of Raman shift signal is utilized by various embodiments to measure localized change in thermal conductivity and/or mechanical stress of structures (e.g., semiconductor structures) under applied stress.