scholarly journals Characterization of SOI MEMS Sidewall Roughness

2011 ◽  
Author(s):  
Leslie M. Phinney ◽  
Bonnie B. McKenzie ◽  
James A. Ohlhausen ◽  
Thomas E. Buchheit ◽  
Randy J. Shul
Keyword(s):  
Aspect Ratio ◽  
Microelectromechanical Systems ◽  
Device Layer ◽  
Sensors And Actuators ◽  
Sidewall Roughness ◽  
Deep Reactive Ion Etching ◽  
Aspect Ratios ◽  
Atomic Force ◽  
Silicon Structures ◽  
Trench Width

Deep reactive ion etching (DRIE) of silicon enables high aspect ratio, deep silicon features that can be incorporated into the fabrication of microelectromechanical systems (MEMS) sensors and actuators. The DRIE process creates silicon structures and consists of three steps: conformal polymer deposition, ion sputtering, and chemical etching. The sequential three step process results in sidewalls with roughness that varies with processing conditions. This paper reports the sidewall roughness for DRIE etched MEMS as a function of trench width from 5 μm to 500 μm for a 125 μm thick device layer corresponding to aspect ratios from 25 to 0.25. Using a scanning electron microscope (SEM), the surfaces were imaged detecting an upper region exhibiting a scalloping morphology and a rougher lower region exhibiting a curtaining morphology. The height of rougher curtaining region increases linearly with aspect ratio when the etch cleared the entire device layer. The surface roughness for two trench widths: 15 μm and 100 μm were further characterized using an atomic force microscope (AFM), and RMS roughness values are reported as a function of height along the surface. The sidewall roughness varies with height and depends on the trench width.

The Benefits of Process Parameter Ramping During The Plasma Etching of High Aspect Ratio Silicon Structures

1998 ◽  
Vol 546 ◽  
Author(s):  
J. Hopkins ◽  
H. Ashraf ◽  
J. K. Bhardwaj ◽  
A. M. Hynes ◽  
I. Johnston ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Plasma Etching ◽  
Etch Rate ◽  
Critical Dimension ◽  
Optical Devices ◽  
Aspect Ratios ◽  
Dimension Control ◽  
Silicon Structures ◽  
High Etch Rate ◽  
Product Specifications

AbstractIn the ongoing enhancement of MEMS applications, the STS Advanced Silicon Etch, (ASETM). process satisfies the demanding requirements of the industry. Typically, highly anisotropic. high aspect ratios profiles with fine CD (critical dimension) control are required. Selectivities to photoresist of 150:1 with Si etch rates of up to 10μm/min are demonstrated. Applications range from shallow etched optical devices to through wafer membrane etches. This paper details some of the fundamental trends of the ASETM process and goes on to discuss how the process has been enhanced to meet product specifications. Parameter ramping is a powerful technique used to achieve the often-conflicting requirements of high etch rate with good profile/CD control. The results are presented in this paper.

scholarly journals Deep Reactive Ion Etching (DRIE) of High Aspect Ratio SiC Microstructures Using a Time-Multiplexed Etch-Passivate Process

2006 ◽  
Vol 527-529 ◽  
pp. 1115-1118 ◽  
Author(s):  
Laura J. Evans ◽  
Glenn M. Beheim
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Turbine Blades ◽  
Reactive Ion Etching ◽  
Sidewall Roughness ◽  
Ion Etching ◽  
Micro Electro Mechanical Systems ◽  
Deep Reactive Ion Etching ◽  
Micro Turbine ◽  
Definition Of

High aspect ratio silicon carbide (SiC) microstructures are needed for microengines and other harsh environment micro-electro-mechanical systems (MEMS). Previously, deep reactive ion etching (DRIE) of low aspect ratio (AR ≤1) deep (>100 *m) trenches in SiC has been reported. However, existing DRIE processes for SiC are not well-suited for definition of high aspect ratio features because such simple etch-only processes provide insufficient control over sidewall roughness and slope. Therefore, we have investigated the use of a time-multiplexed etch-passivate (TMEP) process, which alternates etching with polymer passivation of the etch sidewalls. An optimized TMEP process was used to etch high aspect ratio (AR up to 13) deep (>100 *m) trenches in 6H-SiC. Power MEMS structures (micro turbine blades) in 6H-SiC were also fabricated.

scholarly journals Towards the Fabrication of High-Aspect-Ratio Silicon Gratings by Deep Reactive Ion Etching

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 864 ◽  
Author(s):  
Zhitian Shi ◽  
Konstantins Jefimovs ◽  
Lucia Romano ◽  
Marco Stampanoni
Keyword(s):  
Aspect Ratio ◽  
Etching Rate ◽  
Critical Role ◽  
Reactive Ion Etching ◽  
Chamber Pressure ◽  
Ion Etching ◽  
Deep Reactive Ion Etching ◽  
X Ray ◽  
Aspect Ratios ◽  
Profile Control

The key optical components of X-ray grating interferometry are gratings, whose profile requirements play the most critical role in acquiring high quality images. The difficulty of etching grating lines with high aspect ratios when the pitch is in the range of a few micrometers has greatly limited imaging applications based on X-ray grating interferometry. A high etching rate with low aspect ratio dependence is crucial for higher X-ray energy applications and good profile control by deep reactive ion etching of grating patterns. To achieve this goal, a modified Coburn–Winters model was applied in order to study the influence of key etching parameters, such as chamber pressure and etching power. The recipe for deep reactive ion etching was carefully fine-tuned based on the experimental results. Silicon gratings with an area of 70 × 70 mm2, pitch size of 1.2 and 2 μm were fabricated using the optimized process with aspect ratio α of ~67 and 77, respectively.

scholarly journals Effect of microbeam geometry on the nano-mass sensor performance

2019 ◽  
Vol 20 (3) ◽  
pp. 304
Author(s):  
Jahanbakhsh Reisi Ardali ◽  
Reza Ghaderi ◽  
Farhad Raeiszadeh
Keyword(s):  
Microelectromechanical Systems ◽  
Dynamic Mode ◽  
Mass Sensor ◽  
Sensors And Actuators ◽  
Mass Sensors ◽  
Sensor Performance ◽  
Aspect Ratios ◽  
Wide Range ◽  
Important Challenge ◽  
Frequency Variations

Microbeams have a wide range of applications as sensors and actuators in nanotechnology, biotechnology, microelectromechanical systems, and optics. Given their micrometer dimensions, these beams make precision mass sensors of sub-nanogram accuracy. An important challenge regarding mass sensors is to enhance their sensitivity and accuracy. Considering the fact that, this type of sensor operates based on the resonance frequency variations caused by nanoparticle absorption in the dynamic mode, the geometry of the microbeam is considered an important parameter affecting their sensitivity. This paper studies the rectangular microbeam, which is one of the most commonly used types of mass sensors. Three main models were selected by applying inner and outer cuts on the microbeam, and vibrating simulation was carried out using ABAQUS software for a total of 36 mass sensor configurations with different aspect ratios. Simulation results in two selected rectangular microbeam models with outer cuts show the sensitivity of the microsensor increases with increased microbeam rigidity. The triangular hollow microbeam was found to be the best design among the four models selected to be used as mass sensors.

scholarly journals Effects of Steel Fiber Percentage and Aspect Ratios on Fresh and Harden Properties of Ultra-High Performance Fiber

2021 ◽  
Vol 2 (3) ◽  
pp. 501-515
Author(s):  
Rajib Kumar Biswas ◽  
Farabi Bin Ahmed ◽  
Md. Ehsanul Haque ◽  
Afra Anam Provasha ◽  
Zahid Hasan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
High Performance ◽  
Steel Fiber ◽  
Setting Time ◽  
Fiber Reinforced Concrete ◽  
Future Research ◽  
Manufacturing Cost ◽  
Aspect Ratios ◽  
High Performance Fiber

Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of steel fiber percentages and aspect ratios on the setting time, workability, and mechanical properties of UHPFRC. It was evident that (1) an increase in steel fiber dosage and aspect ratio negatively impacted workability, owing to the interlocking between fibers; (2) compressive strength was positively influenced by the steel fiber dosage and aspect ratio; and (3) a faster loading rate significantly improved the mechanical properties. There were also some shortcomings in the measurement method for setting time. Lastly, this research highlights current issues for future research. The findings of the study are useful for practicing engineers to understand the distinctive characteristics of UHPFRC.

scholarly journals Surface Texturing of Si with Periodically Arrayed Oblique Nanopillars to Achieve Antireflection

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 380
Author(s):  
Jun-Hyun Kim ◽  
Sanghyun You ◽  
Chang-Koo Kim
Keyword(s):  
Aspect Ratio ◽  
Plasma Etching ◽  
Surface Texturing ◽  
Light Reflection ◽  
Si Substrate ◽  
Weighted Mean ◽  
Optical Reflectance ◽  
Si Substrates ◽  
Aspect Ratios ◽  
Shadowing Effect

Si surfaces were texturized with periodically arrayed oblique nanopillars using slanted plasma etching, and their optical reflectance was measured. The weighted mean reflectance (Rw) of the nanopillar-arrayed Si substrate decreased monotonically with increasing angles of the nanopillars. This may have resulted from the increase in the aspect ratio of the trenches between the nanopillars at oblique angles due to the shadowing effect. When the aspect ratios of the trenches between the nanopillars at 0° (vertical) and 40° (oblique) were equal, the Rw of the Si substrates arrayed with nanopillars at 40° was lower than that at 0°. This study suggests that surface texturing of Si with oblique nanopillars reduces light reflection compared to using a conventional array of vertical nanopillars.

scholarly journals Strength Analysis of Alternative Airframe Layouts of Regional Aircraft on the Basis of Automated Parametrical Models

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 80
Author(s):  
Dmitry V. Vedernikov ◽  
Alexander N. Shanygin ◽  
Yury S. Mirgorodsky ◽  
Mikhail D. Levchenkov
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Performance ◽  
Strength Analysis ◽  
Labor Input ◽  
Aerodynamic Loading ◽  
Aspect Ratios ◽  
Wide Range ◽  
Parametrical Design

This publication presents the results of complex parametrical strength investigations of typical wings for regional aircrafts obtained by means of the new version of the four-level algorithm (FLA) with the modified module responsible for the analysis of aerodynamic loading. This version of FLA, as well as a base one, is focused on significant decreasing time and labor input of a complex strength analysis of airframes by using simultaneously different principles of decomposition. The base version includes four-level decomposition of airframe and decomposition of strength tasks. The new one realizes additional decomposition of alternative variants of load cases during the process of determination of critical load cases. Such an algorithm is very suitable for strength analysis and designing airframes of regional aircrafts having a wide range of aerodynamic concepts. Results of validation of the new version of FLA for a high-aspect-ratio wing obtained in this work confirmed high performance of the algorithm in decreasing time and labor input of strength analysis of airframes at the preliminary stages of designing. During parametrical design investigation, some interesting results for strut-braced wings having high aspect ratios were obtained.

Influence of nozzle exit geometrical parameters on supersonic jet decay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar ◽  
R. K. Mishra
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Ambient Air ◽  
Schlieren Image ◽  
Geometrical Parameters ◽  
Image Study ◽  
Aspect Ratios ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

scholarly journals Aspect Ratio Driven Relationship between Nozzle Internal Flow and Supersonic Jet Mixing

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 78
Author(s):  
Kalyani Bhide ◽  
Kiran Siddappaji ◽  
Shaaban Abdallah
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
Nozzle Exit ◽  
Supersonic Jet ◽  
Internal Flow ◽  
Shear Stresses ◽  
Loss Mechanism ◽  
Potential Core ◽  
Jet Mixing ◽  
Aspect Ratios

This work attempts to connect internal flow to the exit flow and supersonic jet mixing in rectangular nozzles with low to high aspect ratios (AR). A series of low and high aspect ratio rectangular nozzles (design Mach number = 1.5) with sharp throats are numerically investigated using steady state Reynolds-averaged Navier−Stokes (RANS) computational fluid dynamics (CFD) with k-omega shear stress transport (SST) turbulence model. The numerical shadowgraph reveals stronger shocks at low ARs which become weaker with increasing AR due to less flow turning at the throat. Stronger shocks cause more aggressive gradients in the boundary layer resulting in higher wall shear stresses at the throat for low ARs. The boundary layer becomes thick at low ARs creating more aerodynamic blockage. The boundary layer exiting the nozzle transforms into a shear layer and grows thicker in the high AR nozzle with a smaller potential core length. The variation in the boundary layer growth on the minor and major axis is explained and its growth downstream the throat has a significant role in nozzle exit flow characteristics. The loss mechanism throughout the flow is shown as the entropy generated due to viscous dissipation and accounts for supersonic jet mixing. Axis switching phenomenon is also addressed by analyzing the streamwise vorticity fields at various locations downstream from the nozzle exit.

Manufacture of High Aspect Ratio Bulk Titanium Micro-Parts by Inductively Coupled Plasma Etching

2008 ◽  
Author(s):  
Gang Zhao ◽  
Qiong Shu ◽  
Yue Li ◽  
Jing Chen
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Inductively Coupled Plasma ◽  
Etching Rate ◽  
Sidewall Roughness ◽  
Inductively Coupled ◽  
Icp Etching ◽  
Novel Technology ◽  
Micro Parts ◽  
Etching Mask

A novel technology is developed to fabricate high aspect ratio bulk titanium micro-parts by inductively coupled plasma (ICP) etching. An optimized etching rate of 0.9 μm/min has been achieved with an aspect ratio higher than 10:1. For the first time, SU-8 is used as titanium etching mask instead of the traditional hard mask such as TiO2 or SiO2. With an effective selectivity of 3 and a spun-on thickness beyond 100 μm, vertical etching sidewall and low sidewall roughness are obtained. Ultra-deep titanium etching up to 200 μm has been realized, which is among the best of the present reports. Titanium micro-springs and planks are successfully fabricated with this approach.

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