Dry Etching of High Aspect Ratio 4H-SiC Microstructures

Luna, Lunet E.; Tadjer, Marko J.; Anderson, Travis J.; Imhoff, Eugene A.; Hobart, Karl D.; Kub, Fritz J.

doi:10.1149/2.0031705jss

Cited by 20 publications

(18 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The wafer was seeded by Cr/Au (100 Å/1000 Å) deposited using electron-beam evaporation, patterned using contact photolithography, and selectively electroplated with a Ni etch mask (1.7 μm thick).Dry etching was carried out following the processes developed in Ref. 44 . Following etching, the metal mask was removed in aqua regia for 1 hour, followed by 60 seconds in chrome etchant and a DI rinse.…”

Section: Device Fabricationmentioning

confidence: 99%

Vibrational Coupling to Epsilon-Near-Zero Waveguide Modes

Folland

Bruncz

et al. 2020

ACS Photonics

View full text Add to dashboard Cite

Epsilon near zero modes offer extreme field enhancement that can be utilized for developing enhanced sensing schemes. However, demonstrations of enhanced spectroscopies have largely exploited surface polaritons, mostly due to the challenges of coupling a vibrational transition to volume-confined epsilon near zero modes. Here we fabricate high aspect ratio gratings (up to 24.8 µm height with greater than 5 μm pitch) of 4H-SiC, with resonant modes that couple to transverse magnetic and transverse electric incident fields. These correspond to metal-insulatormetal waveguide modes propagating downwards into the substrate. The cavity formed by the finite The electromagnetic field confinement offered by surface polaritons 1-2 and epsilon-near-zero (ENZ) 3-7 modes have long been discussed for applications in surface-enhanced sensing [8][9][10][11][12][13] , and vibrational coupling [14][15] . Whilst surface plasmon polaritons (SPPs) have been extensively explored, demonstrating enhanced spectroscopies using ENZ modes has remained challenging. This is largely because at optical frequencies ENZ modes are often realized by coupling light into a material where epsilon is close to zero 16-18 , or via waveguides that are not hollow and therefore incompatible with confining the analyte of interest within the region of highly confined electromagnetic fields [3][4] . In this letter we investigate high-aspect-ratio grating (HAG) structures designed to support surface phonon polaritons (SPhPs) 1 at the interface between the polar crystal grating surfaces and the surrounding environment 19 . We show that the modes supported by this structure behave like metal-insulator-metal (MIM) waveguide modes in a short cavity [20][21][22] .Furthermore, due to this architecture, these structures support an ENZ mode in the gap between the grating teeth. This enables the first colocation of strongly confined ENZ fields with an analyte of interest, including liquids, with large surface area. As proof of this, we demonstrate that the ENZ fields can coherently couple to vibrational transitions in a liquid. Thus, this constitutes a platform for studying ENZ and SPhP strong coupling at infrared (IR) frequencies, with potential applications in surface enhanced spectroscopies [8][9][10][11][12][13]23 as well as light-controlled chemistry [14][15] .This study exploits high aspect ratio gratings, which have a height (h) that is much larger than their period (Λ) (see Fig 1). In HAGs and nanopillars, surface polariton modes are supported between the teeth, propagating as MIM waveguide modes downwards into the grating [20][21][22][24][25] .The frequency of the modes can be controlled by changing the effective index of refraction (neff) of the polariton wave using the size of the air gap (g) between the teeth, or the height of the grating (h, see Fig. 1 a-c). Furthermore, polaritonic modes in these structures have been demonstrated to

show abstract

Section: Device Fabricationmentioning

confidence: 99%

Vibrational Coupling to Epsilon-Near-Zero Waveguide Modes

Folland

Bruncz

et al. 2020

ACS Photonics

View full text Add to dashboard Cite

show abstract

“…Artificial roughness was created on 220 µm thick 4H-SiC wafers via deep reactive ion etching (DRIE). Instead of optimizing the fabrication procedure to minimize roughness and sidewall angle in SiC substrates [56][57][58], gas composition, time of exposure, pressure and temperature of the chamber were tuned to increase the root-mean-square (RMS) roughness. Specifically, the selected parameters were: No Helium in the chamber, 80 sccm of SF 6 and 10 sccm of O 2 , 15 mTorr of pressure, temperature of 30°C and a time of exposure of 12 min (See Methods).…”

Section: Resultsmentioning

confidence: 99%

Addressing the impact of surface roughness on epsilon-near-zero substrates

Navajas¹,

Pérez-Escudero²,

Liberal³

2023

Preprint

View full text Add to dashboard Cite

Epsilon-near-zero (ENZ) media have been very actively investigated due to their unconventional wave phenomena and strengthened nonlinear response. However, the technological impact of ENZ media will be determined by the quality of realistic ENZ materials, including material loss and surface roughness. Here, we provide a comprehensive experimental study of the impact of surface roughness on ENZ substrates. Using silicon carbide (SiC) substrates with artificially induced roughness, we analyze samples whose roughness ranges from a few to hundreds of nanometer size-scales. It is concluded that ENZ substrates with roughness in the few nanometer scale are negatively affected by coupling to longitudinal phonons and strong ENZ fields normal to the surface. On the other hand, when the roughness is in the hundreds of nanometer scale, the ENZ band is found to be more robust than dielectric and surface phonon polariton (SPhP) bands.

show abstract

“…This indicates that the selectivity can be increased further by optimizing the process pressure. Senesky et al [27] reported an SF6 etch selectivity (at a low RF bias) of 16:1 (SiC:AlN) using AlN deposited with reactive sputtering; the higher bulk SiC etch selectivities obtained with MOCVD-grown AlN (at a low RF bias) indicate that AlN grown by MOCVD could replace Ni as a hard mask in fabricating high-aspectratio SiC microstructures and devices [28,29].…”

Section: Sf6 Etch Chemistry Characteristicsmentioning

confidence: 99%

“…Hospitals, for example, reduced the rates of hospital-acquired drugresistant infections by 25% using ultraviolet disinfection (via mercury lamps (254 nm)), as reported by various clinical trials [19,20]. Furthermore, the AlN or AlGaN epi-transfer 2 and heterogeneous integration technology can be employed to enhance the performance of photodiodes (PDs) [21], high electron mobility transistors (HEMTs) [22,23], bulk acoustic resonators (BARs) [24][25][26], and high-aspect-ratio SiC microstructures and devices [27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Fabrication technology for high light-extraction ultraviolet thin-film flip-chip (UV TFFC) LEDs grown on SiC

SaifAddin¹,

Almogbel

Zollner³

et al. 2019

Semicond. Sci. Technol.

View full text Add to dashboard Cite

The light output of deep ultraviolet (UV-C) AlGaN light-emitting diodes (LEDs) is limited due to their poor light extraction efficiency (LEE). To improve the LEE of AlGaN LEDs, we developed a fabrication technology to process AlGaN LEDs grown on SiC into thinfilm flip-chip LEDs (TFFC LEDs) with high LEE. This process transfers the AlGaN LED epi onto a new substrate by wafer-to-wafer bonding, and by removing the absorbing SiC substrate with a highly selective SF6 plasma etch that stops at the AlN buffer layer. We optimized the inductively coupled plasma (ICP) SF6 etch parameters to develop a substrateremoval process with high reliability and precise epitaxial control, without creating micromasking defects or degrading the health of the plasma etching system. The SiC etch rate by SF6 plasma was ~46 µm/hr at a high RF bias (400 W), and ~7 µm/hr at a low RF bias (49 W) with very high etch selectivity between SiC and AlN. The high SF6 etch selectivity between SiC and AlN was essential for removing the SiC substrate and exposing a pristine, smooth AlN surface. We demonstrated the epi-transfer process by fabricating high light extraction TFFC LEDs from AlGaN LEDs grown on SiC. To further enhance the light extraction, the exposed N-face AlN was anisotropically etched in dilute KOH. The LEE of the AlGaN LED improved by ~3X after KOH roughening at room temperature. This AlGaN TFFC LED process establishes a viable path to high external quantum efficiency (EQE) and power conversion efficiency (PCE) UV-C LEDs.

show abstract

Dry Etching of High Aspect Ratio 4H-SiC Microstructures

Cited by 20 publications

References 38 publications

Vibrational Coupling to Epsilon-Near-Zero Waveguide Modes

Vibrational Coupling to Epsilon-Near-Zero Waveguide Modes

Addressing the impact of surface roughness on epsilon-near-zero substrates

Fabrication technology for high light-extraction ultraviolet thin-film flip-chip (UV TFFC) LEDs grown on SiC

Contact Info

Product

Resources

About