SiC Wafer Bonding and Deep Reactive Ion Etching Towards High-Aspect Ratio SiC MEMS Fabrication

Luna, Lunet E.; Hobart, Karl D.; Tadjer, Marko J.; Myers-Ward, Rachael L.; Anderson, Travis J.; Kub, Francis J.

doi:10.1149/08605.0105ecst

Cited by 12 publications

(8 citation statements)

References 8 publications

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“…Unlike laser machining, dry etching using high-density plasma holds the promise of nanoscale precision micromachining of monocrystalline SiCOI wafers with vertical and smooth sidewall profiles. The main challenge in SiCOI DRIE stems from the chemical inertness of SiC which mandates elevated DC self-bias voltages to generate reasonable etch rates on the order of 300 to 700 nm/min 22,23 . Electroplated Ni is preferred as a hard mask for its 30 to 100:1 selectivity over SiC and for its smooth and vertical sidewall profiles via LIGA patterning which are prerequisites for SiC DRIE with nanoscale precision.…”

Section: Resultsmentioning

confidence: 99%

Monocrystalline Silicon Carbide Disk Resonators on Phononic Crystals with Ultra-Low Dissipation Bulk Acoustic Wave Modes

Hamelin

Yang

Daruwalla

et al. 2019

Sci Rep

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Micromechanical resonators with ultra-low energy dissipation are essential for a wide range of applications, such as navigation in GPS-denied environments. Routinely implemented in silicon (Si), their energy dissipation often reaches the quantum limits of Si, which can be surpassed by using materials with lower intrinsic loss. This paper explores dissipation limits in 4H monocrystalline silicon carbide-on-insulator (4H-SiCOI) mechanical resonators fabricated at wafer-level, and reports on ultra-high quality-factors (Q) in gyroscopic-mode disk resonators. The SiC disk resonators are anchored upon an acoustically-engineered Si substrate containing a phononic crystal which suppresses anchor loss and promises QANCHOR near 1 Billion by design. Operating deep in the adiabatic regime, the bulk acoustic wave (BAW) modes of solid SiC disks are mostly free of bulk thermoelastic damping. Capacitively-transduced SiC BAW disk resonators consistently display gyroscopic m = 3 modes with Q-factors above 2 Million (M) at 6.29 MHz, limited by surface TED due to microscale roughness along the disk sidewalls. The surface TED limit is revealed by optical measurements on a SiC disk, with nanoscale smooth sidewalls, exhibiting Q = 18 M at 5.3 MHz, corresponding to f · Q = 9 · 1013 Hz, a 5-fold improvement over the Akhiezer limit of Si. Our results pave the path for integrated SiC resonators and resonant gyroscopes with Q-factors beyond the reach of Si.

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Section: Resultsmentioning

confidence: 99%

Monocrystalline Silicon Carbide Disk Resonators on Phononic Crystals with Ultra-Low Dissipation Bulk Acoustic Wave Modes

Hamelin

Yang

Daruwalla

et al. 2019

Sci Rep

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“…Silicon Carbide mesas [11], beams [7], disks [8] and high-aspect ratio gaps [12] have been demonstrated in 4H-SiC on Insulator (SiCOI) using oxide-oxide wafer bonding and DRIE etching using SF6/O2 and SF6/Ar chemistries. Doped SiCOI technology is ideal for defining and isolating resonators and electrostatic actuators.…”

Section: Device Fabricationmentioning

confidence: 99%

SiC Cantilevers for Generating Uniaxial Stress

Jiang

Opondo

Wolfowicz

et al. 2019

2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems &Amp; Eurosensors XXXIII (TRANSDUCERS &Am

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This paper demonstrates the first beam resonators fabricated from bulk high purity semi-insulating 4H Silicon Carbide wafers (HPSI 4H-SiC). Our innovations include:(1) Multi-level front-side, back-side inductively coupled plasma-deep reactive ion etching (ICP-DRIE) technology to fabricate thin, low-mass, bending-mode resonators framed by the SiC substrate (2) Laser Doppler Vibrometer (LDV) measurements of mechanical quality factors (Q) > 10,000 with frequencies ranging from 300 kHz to 8MHz and (3) Calculated uniaxial in-plane surface stress 20 MPa at top surface of resonator base when operating at resonance in vacuum.

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“…(a) SEM and (b) optical pictures of an ultra-high Q Gen. 2 SiC Lamé resonator fabricated using the high SF 6 recipe. The S 21 frequency responses of Lamé resonators with (c) 1-and (d) 2-unit cells phononic crystals reveal Q = 20 M, the highest ever reported in micro-mechanical Lamé mode resonators, breaking through the barrier of ƒ•Q = 1 × 10 14 Hz 8,20.…”

mentioning

confidence: 94%

“…However, the restricted deployment base of high-density dry etchers dedicated to SiC wafer-level processing continues to obstruct basic research. To wit, there are few papers focused on deep reactive ion etching (DRIE) of SiC 7 and even fewer on DRIE of SiCOI substrates 8 for ultra-high Q MEMS applications. 9 This paper focuses on the challenges in developing dry etching of crystalline SiC substrates with high fidelity and low roughness using STS AOE Pro.…”

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confidence: 99%

Precision Deep Reactive Ion Etching of Monocrystalline 4H-SiCOI for Bulk Acoustic Wave Resonators with Ultra-Low Dissipation

Hamelin

Yang

Ayazi

2021

J. Electrochem. Soc.

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Integrated mechanical resonators with high quality factors (Q) made in high acoustic velocity materials are essential for a wide range of applications, including chemical sensors, timing resonators, and high-performance inertial sensors for navigation in GPS-occluded environments. While silicon is the most popular substrate for the implementation of microelectromechanical systems (MEMS) resonators, SiC exhibits an exceptionally small intrinsic phononic dissipation due to its low Akhiezer damping limit. This paper reports on the latest developments of precision deep reactive ion etching (DRIE) of monocrystalline 4H SiC-on-Insulator (SiCOI) substrates with the aim to fully take advantage of the exquisite mechanical properties of crystalline SiC. To wit, capacitive Lamé mode micromechanical resonators exhibit ƒ·Q products beyond 1 × 1014 Hz independent of crystalline orientation. The contribution of surface roughness to dissipation and practical considerations to etch mirror-polished trenches in SiCOI substrates are discussed, paving the way towards micromechanical monocrystalline SiC resonators with Qs beyond 100 Million.

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SiC Wafer Bonding and Deep Reactive Ion Etching Towards High-Aspect Ratio SiC MEMS Fabrication

Cited by 12 publications

References 8 publications

Monocrystalline Silicon Carbide Disk Resonators on Phononic Crystals with Ultra-Low Dissipation Bulk Acoustic Wave Modes

Monocrystalline Silicon Carbide Disk Resonators on Phononic Crystals with Ultra-Low Dissipation Bulk Acoustic Wave Modes

SiC Cantilevers for Generating Uniaxial Stress

Precision Deep Reactive Ion Etching of Monocrystalline 4H-SiCOI for Bulk Acoustic Wave Resonators with Ultra-Low Dissipation

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