Stress Monitoring of Post-processed MEMS Silicon Microbridge Structures Using Raman Spectroscopy

Starman, LaVern A.; Coutu, Ronald A.

doi:10.1007/s11340-011-9586-9

Cited by 14 publications

(11 citation statements)

References 43 publications

(63 reference statements)

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“…It is also worth noting that laser heating at the sample must be eliminated or significantly reduced to minimise thermal effects on the Raman spectrum when utilising micro-Raman spectroscopy to measure stress profiles. According to the experimental results of Starman and Coutu [11], the temperature rise of a polysilicon microbridge because of a 2.4 mW laser power is ∼0.49°C which results in a Raman shift of only −0.00125 cm −1 . Based on (15) and (16), this laser heating induced Raman shift equates to an increase in stress of about 0.31 MPa, which means that the temperature effects can be neglected when setting a laser power level lower than 2.4 mW.…”

Section: Stress Measurements Using Micro-raman Spectroscopy Methodmentioning

confidence: 99%

“…There are several techniques for measuring and characterising residual stress in microscale structures, such as wafer curvature measurement [7], the X-ray microdiffraction technique [8] and the micro-Raman spectroscopy method [9][10][11][12]. The spatial resolution of the wafer curvature method is very low with tens of microns and not suitable for our fabricated tiny MEMS resonators.…”

Section: Introductionmentioning

confidence: 99%

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Suspended gate field effect transistor type microelectromechanical systems resonators modelling with micro‐Raman spectroscopy measured residual stress

Zhao

Guo

et al. 2013

Micro & Nano Letters

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Presented is an improved model of doubly-clamped microelectromechanical systems (MEMS) resonators implemented in very high-speed integrated circuit hardware description language for analogue and mixed-signal (VHDL-AMS). The model includes the effect of residual stress, which may severely shift the resonant frequency of the MEMS resonator from the analytical pre-designed value if the magnitude of intrinsic residual stress is imprecisely predicted. As the stress is not only determined by the fabrication process but also related to the structural dimensions of the resonators, in this work micro-Raman spectroscopy was utilised to measure and characterise the residual stress of a series of fabricated doubly-clamped polysilicon suspended gate field effect transistor type resonators with varying sizes. Combined with the experimentally determined residual stress, the proposed VHDL-AMS analytical model provides an error of < 3.5% resonant frequency shift with respect to the experimental result.1. Introduction: Microelectromechanical systems (MEMS) resonators are becoming increasingly attractive in timing and frequency control applications [1] because of their significant advantages of an intrinsic very high quality factor and high resonant frequency [2]. MEMS resonators also show exceptional possibilities for creating miniature-scale precision oscillators and filters because of their tiny geometric size and CMOS compatibility [3]. In addition, as the resonant frequencies are dependent on the operating conditions such as temperature and pressure, MEMS resonators show great potential as sensors such as the high sensitivity mass detector [4].Owing to the small size of the MEMS devices, microscale characterisation of residual stress is essential when considering the functionality and reliability of MEMS resonators. The residual stress can cause bending or buckling of the suspended structures of the MEMS resonators, which not only severely shifts the resonant frequency of the MEMS resonator from the analytical pre-designed value towards a desired application but also becomes the potential source leading to the failure of the MEMS resonators. If the residual stress can be accurately characterised, and eventually controlled, the design of the MEMS resonators will not be limited by residual stress. The designer may even take advantage of the intrinsic stress to increase the resonant frequency and quality factor of MEMS resonators.Residual stress is usually estimated by using the finite-element analysis (FEA) approach [5]. However, since the residual stress of a MEMS resonator is not only determined by the fabrication process but also related to the structural dimensions, there is a large margin of error in predicting stress using simulation, unless the experimental measurements are validated [6].There are several techniques for measuring and characterising residual stress in microscale structures, such as wafer curvature measurement [7], the X-ray microdiffraction technique [8] and the micro-Raman spectroscopy method [9][10][11][...

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Section: Stress Measurements Using Micro-raman Spectroscopy Methodmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Suspended gate field effect transistor type microelectromechanical systems resonators modelling with micro‐Raman spectroscopy measured residual stress

Zhao

Guo

et al. 2013

Micro & Nano Letters

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“…The linear correlation between shifts in the Raman spectra and amount of stress in crystalline materials is well defined for Si, with examples of direct stress measurements on Si microcapsules and Si bridges . Raman can also be used to measure stress in III–V semiconductors such as AlN and GaN, and other zinc blend type semiconductors including Ge, GaAs, GaSb, InAs, and ZnS .…”

Section: Introductionmentioning

confidence: 99%

Structural Anisotropy in Stretchable Silicon

Curtis

Tompkins

Nichols

et al. 2019

Adv Elect Materials

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Patterned planar silicon (Si) semiconductor structures able to conform around 3D surfaces are promising candidates for wearable devices from solar cells to displays. Despite the known anisotropic material properties of crystalline semiconductors, prior evaluations have assumed isotropic stretchable mechanical behavior. The effect of structural anisotropy on the mechanical stretching behavior of {100} single crystalline Si planes is demonstrated through models and experiments. 3D finite element analysis results show serpentines fabricated and strained loaded on the dense {111} family of planes will have maximum von Mises peak stresses that are 20% higher than those fabricated in the <100> direction on the {100} family of planes. A fabrication process is presented to release in‐plane Si serpentine test structures from (100) silicon‐on‐insulator wafers aligned parallel to the <110> and <100> crystallographic orientations. The released test structures can accommodate strains to 84%. Raman spectroscopy is used to characterize anisotropic effects on the internal stresses of Si serpentines. Raman measurements confirm two different maximum stress locations on <110> and <100> Si serpentines, resulting in two different break locations. All results show anisotropy plays a critical role in the mechanical behavior of stretchable Si serpentines and must be considered during design of stretchable semiconductor structures.

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“…During laser irradiation of the structure, the spectral frequency of the scattered light varies with stress. By comparing the spectroscopy with that of the unstressed structure, the internal stress at each point of the structure can be determined [ 12 , 13 ]. The third method utilizes piezoresistivity.…”

Section: Introductionmentioning

confidence: 99%

Measurement and Isolation of Thermal Stress in Silicon-On-Glass MEMS Structures

Chen

Guo

Zhang

et al. 2018

Sensors

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The mechanical stress in silicon-on-glass MEMS structures and a stress isolation scheme were studied by analysis and experimentation. Double-ended tuning forks (DETFs) were used to measure the stress based on the stress-frequency conversion effect. Considering the coefficients of thermal expansion (CTEs) of silicon and glass and the temperature coefficient of the Young’s modulus of silicon, the sensitivity of the natural frequency to temperature change was analyzed. A stress isolation mechanism composed of annular isolators and a rigid frame is proposed to prevent the structure inside the frame from being subjected to thermal stresses. DETFs without and with one- or two-stage isolation frames with the orientations <110> and <100> were designed, the stress and natural frequency variations with temperature were simulated and measured. The experimental results show that in the temperature range of −50 °C to 85 °C, the stress varied from −18 MPa to 10 MPa in the orientation <110> and −11 MPa to 5 MPa in the orientation <100>. For the 1-stage isolated DETF of <110> orientation, the measured stress variation was only 0.082 MPa. The thermal stress can be mostly rejected by a stress isolation structure, which is applicable in the design of stress-sensitive MEMS sensors and actuators.

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Stress Monitoring of Post-processed MEMS Silicon Microbridge Structures Using Raman Spectroscopy

Cited by 14 publications

References 43 publications

Suspended gate field effect transistor type microelectromechanical systems resonators modelling with micro‐Raman spectroscopy measured residual stress

Suspended gate field effect transistor type microelectromechanical systems resonators modelling with micro‐Raman spectroscopy measured residual stress

Structural Anisotropy in Stretchable Silicon

Measurement and Isolation of Thermal Stress in Silicon-On-Glass MEMS Structures

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