Reactive Ion Etching of GaAs,GaSb,InP and InAs in Cl_2/Ar Plasma

Reactive ion etching characteristics of GaAs,GaSb,InP and InAs using Cl2/Ar plasma have been investigated,it is that,etching rates and etching profiles as functions of etching time,gas flow ratio and RF power.Etch rates of above 0.45 μm/min and 1.2 μm/min have been obtained in etching of GaAs and GaSb respectively, while very slow etch rates （<40 nm/min） were observed in etching of In-containing materials,which were linearly increased with the applied RF power.Etched surfaces have remained smooth over a wide range of plasma conditions in the etching of GaAs,InP and InAs,however,were partly blackened in etching of GaSb due to a rough appearance.

Trap states induced by reactive ion etching in AlGaN/GaN high-electron-mobility transistors

Frequency-dependent conductance measurements were carried out to investigate the trap states induced by reactive ion etching in A1GaN/GaN high-electron-mobility transistors （HEMTs） quantitatively. For the non-recessed HEMT, the trap state density decreases from 2.48 × 1013 cm-2.eV-1 at an energy of 0.29 eV to 2.79 × 1012 cm-2.eV-1 at ET = 0.33 eV. In contrast, the trap state density of 2.38 × 1013-1.10× 1014 cm-2.eV-1 is located at ET in a range of 0.30-0.33 eV for the recessed HEMT. Thus, lots of trap states with shallow energy levels are induced by the gate recess etching. The induced shallow trap states can be changed into deep trap states by 350 ℃ annealing process. As a result, there are two different types of trap sates, fast and slow, in the annealed HEMT. The parameters of the annealed HEMT are ET = 0.29-0.31 eV and DT = 8.16× 1012-5.58 × 1013 cm-2.eV-1 for the fast trap states, and ET = 0.37-0.45 eV and DT = 1.84×1013- 8.50 × 1013 cm-2.eV-1 for the slow trap states. The gate leakage currents are changed by the etching and following annealing process, and this change can be explained by the analysis of the trap states.

Transfer of Machined Patterns on an Aluminum Plate to Pyrex Glass Using Reactive Ion Etching SF_(6) Plasma without Masks

A method for etching the surface of a Pyrex glass substrate using the Reactive Ion Etching process without the use of masks is reported. Variations in the machined surface on an auxiliary plate, manufactured in aluminum and placed below a Pyrex glass slide, were transferred to the upper surface of the substrate. SF6 as etching gas and low pressure chamber to promote the increase of mean free path of ions were used. Two etching ratios were found, general, that affects the entire surface of the substrate, and differential, which generates the relief on the surface of the glass. Differential etching depth showed a linear behavior with respect to time;the mean differential etching rate obtained was 43 nm/min. The same phase between the auxiliary plate machining and the etched pattern on the substrate is preserved. With this technique it was possible to manufacture convex and concave surfaces;some examples are given. The arithmetic mean roughness achieved with the proposed method was found to be N1 class, ideal for the development of optical corrector plates.

Formation mechanism of multi-functional black silicon based on optimized deep reactive ion etching technique with SF_6/C_4F_8

This paper reports a controllable multi-functional black silicon surface with nanocone-forest structures fabricated by an optimized deep reactive ion etching(DRIE)technique using SF6/C4F8 in cyclic etching-passivation process,which is maskless,effective and controllable.The process conditions are investigated by systematically comparative experiments and core parameters have been figured out,including etching process parameters,pre-treatment,patterned silicon etching and inclined surface etching.Based on the experimental data,the formation mechanism of nanocone shape is developed,which provides a novel view for in-depth understanding of abnormal phenomena observed in the experiments under different process situations.After the optimization of the process parameters,the black silicon surfaces exhibit superhydrophobicity with tunable reflectance.Additionally,the quantitative relationship between nanocones aspect ratio and surface reflectance and static contact angle is obtained,which demonstrates that black silicon surfaces with unique functional properties(i.e.,cross-combination of reflectance and wettability)can be achieved by controlling the morphology of nanostructures.

A sliding-mode triboelectric nanogenerator with chemical group grated structure by shadow mask reactive ion etching

With the support by the National Natural Science Foundation of China,a collaboration by the research groups led by Prof.Cheng Gang(程纲)from Henan University and Prof.Wang Zhonglin(王中林)from Beijing Institute of Nanoenergy and Nanosystems,Chinese Academy of Sciences,invents'a sliding-mode triboelectric nanogenerator with chemical group grated structure by shadow mask reactive ion etching',which was published in ACS Nano(2017,11(9):8796-8803).

A photoluminescence study of plasma reactive ion etching-induced damage in GaN

GaN films with reactive ion etching （RIE） induced damage were analyzed using photoluminescence （PL）. We observed band-edge as well as donor-acceptor peaks with associated phonon replicas, all in agreement with previous studies. While both the control and damaged samples have their band-edge peak location change with temperature following the Varshni formula, its intensity however decreases with damage while the D-A peak increases considerably. Nitrogen post-etch plasma was shown to improve the band edge peak and decrease the D-A peak. This suggests that the N2 plasma has helped reduce the number of trapped carriers that were participating in the D-A transition and made the D°X transition more active, which reaffirms the N2 post-etch plasma treatment as a good technique to heal the GaN surface, most likely by filling the nitrogen vacancies previously created by etch damage.

Reactive ion etching of Si_2Sb_2Te_5 in CF_4/Ar plasma for a nonvolatile phase-change memory device

Phase change random access memory （PCRAM） is one of the best candidates for next generation non- volatile memory, and phase change SiESbETe5 material is expected to be a promising material for PCRAM. In the fabrication of phase change random access memories, the etching process is a critical step. In this paper, the etching characteristics of Si2Sb2Te5 films were studied with a CF4/Ar gas mixture using a reactive ion etching system. We observed a monotonic decrease in etch rate with decreasing CF4 concentration, meanwhile, Ar concentration went up and smoother etched surfaces were obtained. It proves that CF4 determines the etch rate while Ar plays an im- portant role in defining the smoothness of the etched surface and sidewall edge acuity. Compared with GeESbETe5, it is found that Si2Sb2Te5 has a greater etch rate. Etching characteristics of Si2SbETe5 as a function of power and pressure were also studied. The smoothest surfaces and most vertical sidewalls were achieved using a CF4/Ar gas mixture ratio of 10/40, a background pressure of 40 mTorr, and power of 200 W.

Reactive Ion Etching of ITO Transparent Electrode of TFT-AMLCD in Ar/CF_4 Plasma

The pattern of ITO transparent electrode of pixel cells in TFT-AMLCD is a critical step in the manufacturing process of flat panel display devices,the development of suitable plasma reactive ion etching is necessary to achieve high resolution display.In this work we investigated the Ar/CF 4 plasma etching of ITO as function of different parameters.We demonstrated the ability of this plasma to etch ITO and achieved an etching rate of about 3.73 nm/min,which is expected to increase for long pumping down period,and also through addition of hydrogen in the plasma.Furthermore we described the ITO etching mechanism in Ar/CF 4 plasma.The investigation of selectivity showed to be very low over silicon nitride and silicon dioxide but very high over aluminum.

Reactive ion etching of Ti-diffused LiNbO_3 slab waveguides

Reactive ion etching（RIE） of LiNbO_3（LN） in SF_6 plasma atmosphere was studied for optimizing the preparation conditions for LN ridge waveguides.The samples to be etched are Ti-diffused LN slab waveguides overlaid with a chromium film mask that has a Mach-Zehnder interferometer（MZI） array pattern.The experimental results indicate that the LN-etching rate（R_（LN）） and the Cr-etching rate（R_（Cr）） as well as the rate ratio R_（LN）/R_（Cr） increase with either increasing the radio-frequency（RF） power at a given SF_6 flow rate or increasing the SF_6 flow rate at a fixed RF power.The maximum values of R_（LN） = 43.2 nm/min and R_（LN）/R_（Cr） = 3.27 were achieved with 300 W RF power and 40 sccm SF_6 flow.When the SF_6 flow rate exceeds 40 sccm,an increase in the flow rate causes the etching rates and the rate ratio to decrease.The scanning electron microscope images of the LN ridge prepared after～20 min etching show that the ridge height is 680 nm and the sidewall slope angle is about 60°.

Optimization of Plasma Etching Parameters and Mask for Silica Optical Waveguides

Optical waveguides in silica-on-silicon are one of the key elements in optical communications.The processes of deep etching silica waveguides using resist and metal masks in RIE plasma are investigated.The etching responses,including etching rate and selectivity as functions of variation of parameters,are modeled with a 3D neural network.A novel resist/metal combined mask that can overcome the single-layer masks’ limitations is developed for enhancing the waveguides deep etching and low-loss optical waveguides are fabricated at last.

Fabrication of Diamond Microstructures by Using Dry and Wet Etching Methods

Diamond films have great potential for micro-electro-mechanical system（MEMS） application.For device realization,precise patterning of diamond films at micrometer scale is indispensable.In this paper,simple and facile methods will be demonstrated for smart patterning of diamond films,in which two etching techniques,i.e.,plasma dry etching and chemical wet etching（including isotropic-etching and anisotropic-etching） have been developed for obtaining diamond microstructures with different morphology demands.Free-standing diamond micro-gears and micro-combs were achieved as examples by using the experimental procedures.It is confirmed that as-designed diamond structures with a straight side wall and a distinct boundary can be fabricated effectively and efficiently by using such methods.

Fabrication of Ultra Deep Electrical Isolation Trenches with High Aspect Ratio Using DRIE and Dielectric Refill

A novel technique to fabricate ultra deep high aspect ratio electrical isolation trenches with DRIE and dielectric refill is presented.The relationship between trench profile and DRIE parameters is discussed.By optimizing DRIE parameters and RIE etching the trenches’ opening,the ideal trench profile is obtained to ensure that the trenches are fully refilled without voids.The electrical isolation trenches are 5μm wide and 92μm deep with 0.5μm thick oxide layers on the sidewall as isolation material.The measured I-V result shows that the trench structure has good electrical isolation performance:the average resistance in the range of 0～100V is more than 10 11Ω and no breakdown appears under 100V.This isolation trench structure has been used in fabrication of the bulk integrated micromachined gyroscope,which shows high performance.

Fabrication of High-Density Out-of-Plane Microneedle Arrays with Various Heights and Diverse Cross-Sectional Shapes

Out-of-plane microneedle structures are widely used in various applications such as transcutaneous drug delivery and neural signal recording for brain machine interface.This work presents a novel but simple method to fabricate high-density silicon(Si)microneedle arrays with various heights and diverse cross-sectional shapes depending on photomask pattern designs.The proposed fabrication method is composed of a single photolithography and two subsequent deep reactive ion etching(DRIE)steps.First,a photoresist layer was patterned on a Si substrate to define areas to be etched,which will eventually determine the final location and shape of each individual microneedle.Then,the 1st DRIE step created deep trenches with a highly anisotropic etching of the Si substrate.Subsequently,the photoresist was removed for more isotropic etching;the 2nd DRIE isolated and sharpened microneedles from the predefined trench structures.Depending on diverse photomask designs,the 2nd DRIE formed arrays of microneedles that have various height distributions,as well as diverse cross-sectional shapes across the substrate.With these simple steps,high-aspect ratio microneedles were created in the high density of up to 625 microneedles mm^(-2)on a Si wafer.Insertion tests showed a small force as low as~172μN/microneedle is required for microneedle arrays to penetrate the dura mater of a mouse brain.To demonstrate a feasibility of drug delivery application,we also implemented silk microneedle arrays using molding processes.The fabrication method of the present study is expected to be broadly applicable to create microneedle structures for drug delivery,neuroprosthetic devices,and so on.

Subtle Variations in Surface Properties of Black Silicon Surfaces Influence the Degree of Bactericidal Efficiency

One of the major challenges faced by the biomedical industry is the development of robust synthetic surfaces that can resist bacterial colonization. Much inspiration has been drawn recently from naturally occurring mechano-bactericidal surfaces such as the wings of cicada(Psaltoda claripennis) and dragonfly(Diplacodes bipunctata) species in fabricating their synthetic analogs. However,the bactericidal activity of nanostructured surfaces is observed in a particular range of parameters reflecting the geometry of nanostructures and surface wettability. Here,several of the nanometer-scale characteristics of black silicon(bSi) surfaces including the density and height of the nanopillars that have the potential to influence the bactericidal efficiency of these nanostructured surfaces have been investigated. The results provide important evidence that minor variations in the nanoarchitecture of substrata can substantially alter their performance as bactericidal surfaces.

Fabrication of low-loss SiO2/Si channel waveguides by roughness reduction

An experimental study of the dependence of SiO2 waveguide side wall roughness on the etch condi- tions and etch masks in CHF3/O2 based reactive ion etching plasma was reported. When working under standard low-pressure （20mtorr） etching conditions, a novel etch roughening phenomenon has been observed in the plasma, that is, the roughness of the etched front surface increases with the amount of material etched, independent of etch rate, RF power, and gas composition. Besides, the etched underlying side wall will be tapered as the upper SU-8 resist pattern degradation transfers downward. A process using double-layered mask, consisting of SU-8 resist and thin Chromium film, was developed for improving the side wall smoothness. Based on the studies, SiO2/Si channel waveguides with the propagation loss less than 0. 07dB/cm were fabricated at last.

A MICROFABRICATED METAL GRATING OSCILLATOR FOR ELECTRIC FIELD DETECTION

This letter proposes a novel design of a Micro Electro Mechanical System （MEMS） device featuring a metal grating vibratory mierostructure driven by electrostatic force to sense the spatial electric field. Due to the advantages in slide-film damping and large vibration amplitude, such a device makes atmospheric packaging a low-cost option for practical manufacture. In this letter, we present the operating principles and specifications, the design structure, as well as the finite element simulation. Computational analysis shows that our design obtains good results in device parameters setting, while its simplicity and low-cost features make it an attractive solution for applications.

Self-powered flexible fingerprint-recognition display based on a triboelectric nanogenerator

In the time of Internet of Things(IoT),alternating current electroluminescence(ACEL)has unique advantages in the fields of smart display and human–computer interaction.However,their reliance on external high-voltage AC power supplies poses challenges in terms of wearability and limits their practical application.This paper proposed an innovative scheme for preparing a feather triboelectric nanogenerator(F-TENG)using recyclable and environmentally friendly material.The highest open-circuit voltage,short-circuit current,and transferred charge of SF6-treated F-TENGs can reach 449 V,63μA,and 152 nC,which enables easy lighting of BaTiO_(3)^(-)doped ACEL devices.Using a human electrical potential,a single-electrode F-TENG is combined with ACEL device for self-powered fingerprint recognition display.These works achieve self-powered flexible wearable ACEL devices,which are not only efficient and portable but also have good application prospects in the human–computer interaction,functional displays,and wearable electronic devices.

Experimental Study on the Footing Effect for SOG Structures Using DRIE

This paper experimentally studies the effects of the conductivity of a silicon wafer and the gap height between silicon structures and glass substrate on the footing effect for silicon on glass （SOG） structures in the deep reactive ion etching （DRIE） process. Experiments with gap heights of 5,20, and 50μm were carried out for performance comparison of the footing effect. Also,two kinds of silicon wafers with resistivity of 2-4 and 0.01-0. 0312Ω· cm were used for the exploration. The results show that structures with resistivity of 0.01 - 0. 0312Ω· cm have better topography than those with resistivity of 2-4Ω· cm; and structures with 50μm-high gaps between silicon structures and glass substrate suffer some- what less of a footing effect than those with 20μm-high gaps,and much less than those with Stem-high gaps. Our theoretical analysis indicates that either the higher conductivity of the silicon wafer or a larger gap height between silicon structures and glass substrate can suppress footing effects. The results can contribute to the choice of silicon type and optimum design for many microsensors.

Fast patterning and dry-etch of SiN_x for high resolution nanoimprint templates

We developed a simplified nanofabrication process for imprint templates by fast speed electron beam lithography（EBL） and a dry etch technique on a SiNx substrate,intended for large area manufacturing.To this end,the highly sensitive chemically amplified resist（CAR）,NEB-22,with negative tone was used.The EBL process first defines the template pattern in NEB-22,which is then directly used as an etching mask in the subsequent reactive ion etching（RIE） on the SiNx to form the desired templates.The properties of both e-beam lithography and dry etch of NEB-22 were carefully studied,indicating significant advantages of this process with some drawbacks compared to when Cr was used as an etching mask.Nevertheless,our results open up a good opportunity to fabricate high resolution imprint templates with the prospect of wafer scale manufacturing.

Effect of CHF3/Ar Gas Flow Ratio on Self-masking Subwavelength Structures Prepared on Fused Silica Surface

Based on an advanced technology, randomly-aligned subwavelength structures（SWSs） were obtained by a metal-nanodot-induced one-step self-masking reactive-ion-etching process on a fused silica surface. Metal-fluoride（mainly ferrous-fluoride） nanodots induce and gather stable fluorocarbon polymer etching inhibitors in the reactive-ion-etching polymers as masks. Metal fluoride（mainly ferrous fluoride） is produced by the sputtering of argon plasma and the ion-enhanced chemical reaction of metal atoms. With an increase in CHF_3/Ar gas flow ratio, the average height of the SWSs increases, the number of SWSs per specific area increases and then decreases, and the optical transmittance of visible light increases and then decreases. The optimum CHF_3/Ar gas flow ratio for preparing SWSs is 1：5.