Etching Angle Research Articles

DEEP REACTIVE ION ETCHING FOR PILLAR TYPE NANOPHOTONIC CRYSTAL

Experimental results and techniques developed for time multiplexed deep reactive ion etching of nano-photonic crystals are presented. Specifically, the high aspect ratio pillar type two-dimensional photonic crystal (PhC) structure on silicon is fabricated and studied for its high potential in application to lightwave circuits and also for discussion of the many unique challenges involved in its fabrication process as opposed to standard larger scale devices. In the experiments, patterns of nano-dots were first obtained using deep UV lithography and transferred to a silicon oxide hardmask prior to DRIE processing. The iteration of DRIE experiments with varying process parameters then allowed for a characterization of the varying impact of each etching parameter such as coil/ platen/ etch power, multiplexing cycling gas flows and timing patterns etc. After much optimization of sidewall etch angle and also reduction of the scalloping effect, the latest result obtained for such nano-pillar type PhC designed for application in communication is derived to have a high AR of 33.

Investigation of Basal Plane Dislocations in the 4H-SiC Epilayers Grown on {0001} Substrates

In this paper, we investigated the density of basal plane dislocations (BPDs) in 4H-SiC epilayers grown on (0001) and (000-1). Re-polishing of the substrate surface, in-situ H2 etching and off-cut angle were found to influence the propagation of BPDs into the epilayers. The epitaxial growth on (000-1) substrates yields a relatively low density of BPDs compared to growth on (0001). The electrical characteristics of pn diodes were also investigated, and the suppressed forward degradation and high-voltage blocking performance were obtained in the use of the (000-1) epilayers.

Fabrication of patterned magnetic nanodots by laser interference lithography

A method of fabrication of patterned magnetic nanodots by means of laser interference lithography is presented. This method includes the use of a diluted positive photoresist, and modifications in the etching angle and acceleration voltage of the ion beam etching process. Vertical standing waves were suppressed by using a high exposure dose (supra-exposure) instead of an antireflective coating. Field dependent magnetic force microscopy was used to measure the switching field distribution, which was found to range from 80 to 192 kA/m.

High resolution and aspect ratio two-dimensional photonic band-gap crystal

This paper reports the challenges resolved to realize high aspect ratio pillar-type two-dimensional photonic band-gap crystal (PhC), designed for application at the optical communication wavelengths. Specifically, the issue of a drastically reduced process window of deep UV lithography and deep reactive ion etching, for a super dense array of submicron size pillars with a diameter of 230nm and a spacing of 340nm is treated. A rigorous design of experiments yielded high-resolution PhCs with precise lattice dimensions even near regions of “defect structures” designed for device operations. At the same time, in the etching process, the stringent requirement of an etch angle needed for successful realization of such a super dense array of submicron size PhC lattice was also satisfied to yield sidewalls of high verticality, aspect ratios greater than 50, and scallop-depths of 12nm.

Si(100)기판위에 성장된 3C-SiC 박막의 반응성 이온식각 특성

This paper describes on RIE(Reactive Ion Etching) characteristics of 3C-SiC(Silicon Carbide) grown on Si(100) wafers. In this work, CHF<TEX>$_3$</TEX> gas was used to form the polymer as a function of a side-wall for excellent anisotropy etching during the RIE process. The ranges of the etch rate were obtained from 60 <TEX>$\AA$</TEX>/min to 980 <TEX>$\AA$</TEX>/min according to the conditions such as working gas pressure, RF power, distance between electrodes and the <TEX>$O_2$</TEX> addition ratio in working gas pressure. Under the condition such as 100 mTorr of working gas pressure, 200 W of RF power and 30 mm of the distance between electrodes, mesa structures with about 40 of the etch angle were formed, and the vertical structures could be improved with 50 % of <TEX>$O_2$</TEX> addition ratio in reactive gas during the RIE process. As a result of the investigation, we know that it is possible to apply the RIE process of 3C-SiC using CHF<TEX>$_3$</TEX> for the development of electronic parts and MEMS applications in harsh environments.

Selective etching process of SrBi2Ta2O9 and CeO2 for self-aligned ferroelectric gate structure

We have investigated an etch-stop process and fabricated the ferroelectric gate transistor without damage of source and drain regions using etching selectivity between etch rates of SrBi2Ta2O9 (SBT) and CeO2. The SBT and CeO2 were etched with inductively coupled plasma (ICP) reactive ion etching at various Ar/Cl2 gas mixing ratios, ICP powers, and rf bias powers. The etching selectivity of SBT/CeO2 was 6.8 and the vertical etching angle of SBT was 82° at the condition of 50% Cl2 concentration with the ICP power of 900 W and the rf bias power of 100 W. The characteristics of devices fabricated with an etch-stop process showed that there was no degradation of the ferroelectric characteristics and on/off ratio of programmable operation was 104.

측면 식각된 LED의 광추출 효율에 관한 연구

AIGaInP/GaP 계열 고휘도 LED의 광추출효율을 높이기 위하여 평행직육면체 다이스 측면을 식각할 경우에, 식각 깊이와 각도가 광추출효율에 미치는 영향을 재료의 흡수계수와 전극의 반사 및 흡수율에 따라 해석하고 공정의 용이성을 고려한 광추출효율의 개선이 기대되는 측면 식각깊이와 식각각도를 고찰하였다. 그 결과 결함 등에 의한 재료의 흡수계수가 0~1 <TEX>$cm^{-1}$</TEX> / 이 되도록 발광다이오드 재료의 결정을 성장시켰을 경우, 전극을 고려하지 않은 LED의 기하구조의 변화를 통한 광추출효율개선 효과를 얻기 위해서 측면의 식각각도는 22<TEX>$^{\circ}$</TEX>~45<TEX>$^{\circ}$</TEX>로 하고 식각깊이는 다이스 높이의 8%~17%로 할 때 전극을 고려하지 않은 TIP 구조 LED의 80%에 해당하는 광추출효율을 얻을 수 있고, 식각깊이를 다이스 높이의 16%~39%로 하면 전극을 고려하지 않은 TIP 구조 LED의 90%에 해당하는 광추출효율을 얻을 수 있다. 전극의 영향을 고려할 경우 LED의 기하구조의 변화를 통한 광추출효율 개선 효과를 얻기 위해서 측면의 식각각도는 25<TEX>$^{\circ}$</TEX>~45<TEX>$^{\circ}$</TEX>로 하고 식각깊이는 다이스 높이의 30%~36% 로 할 때 전극을 고려한 TIP 구조 LED의 90%에 해당하는 광추출효율을 얻을 수 있고, 식각깊이를 다이스 높이의 57%~71%로 하면 전극을 고려한 TIP구조 LED의 90%에 해당하는 광추출효율을 얻을 수 있음을 밝혔다. In the case of a AIGalnP/GaP system rectangular parallelepiped high brightness LED which has side walls etched to be slanted off the vertical direction, we have studied the effects of lossy electrodes and material absorption and etching depth and angle of side walls on its light extraction efficiency. If LEDs have no electrodes, in order to obtain an 80％ light extraction efficiency of a TIP (truncated inverted pyramid) LED, the side-etched LEDs should have an etching angle of 22<TEX>$^{\circ}$</TEX>~45<TEX>$^{\circ}$</TEX> and an etching depth of 8~17% of a dice height and an absorption coefficient less than 1 <TEX>$cm^{-1}$</TEX> / In case of etching depth of 16~39% of a dice height, we can obtain a 90% light extraction efficiency of a TIP LED. But when LEDs have two electrodes and no absorption loss, in order to obtain an 80％ light extraction efficiency of a TIP LEBs, the side-etched LEDs should have an etching angle of 25<TEX>$^{\circ}$</TEX>-45<TEX>$^{\circ}$</TEX> and an etching depth of 30～36% of a dice height. In case of etching depth of 57~71％ of a dice height, we can obtain a 90％ light extraction efficiency of a TIP LED.

Studies of CR-39 etch rates

A series of chemical etching experiments have been carried out on CR-39 detectors irradiated with fission fragments of 252Cf to study the bulk and track etching characteristics. Experimental data has been analyzed to find out important track etch parameters. Both bulk and track etch rates are found to follow the Arrhenius equation which gives the variation of etch rate with temperature for a specific set of etching conditions. Activation energies for bulk and track etching have been determined by fitting Arrhenius equation to the experimental data. Other track etch parameters, e.g. critical angle of etching and track registration efficiency have also been determined using experimental data. Track etch parameters depend on properties of incident ion and etching conditions. Results describing the dependence of track etch parameters on etching conditions have been presented. These results are useful in the interpretation of track data.

Dating of a quaternary limestone cave by combining the SSNTD technique with paleodose measurements: application to the stalagmite and stalactite growth

Uranium ( 238 U ) and thorium ( 232 Th ) contents were evaluated in different stalagmite and stalactite samples belonging to a quaternary limestone cave by using a method based on determining mean critical angles of etching of the CR-39 and LR-115 II solid-state nuclear track detectors (SSNTDs). Annual absorbed α-, β- and γ-dose rates were determined in the stalagmite and stalactite materials. The stalagmite and stalactite samples were dated by exploiting data obtained for the total annual absorbed dose rates and measuring the corresponding paleodoses. Results obtained were compared with those obtained by classic thermoluminescence and U/Th disequilibrium methods. The studied speleothem began from about 121 kyr and continued to about 69 kyr , coinciding almost with the last interglaciation corresponding to the fourth and fifth isotope stages. The formation rates of the stalagmite and stalactite samples were found equal to 0.88 and 0.94 cm kyr −1 , respectively.

Use of three new SSNTD methods for evaluating thorium contents in different building materials and measuring thoron and its progeny concentrations inside dwellings

Three new methods based on using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) were used for measuring thorium concentrations (in 10 −6 g/g (ppm)) inside different building materials and evaluating the resulting concentrations of thoron and its progenies in dwellings built by the studied materials. The first technique consists of determining the probabilities for α-particles emitted by the uranium and thorium series inside the building materials or by the radon and thoron groups inside the dwelling atmosphere to reach and be registered as tracks on the SSNTD utilized and exploiting the resulting track density rates. The second method consists of evaluating the mean critical angles of etching of the CR-39 and LR-115 II SSNTD and measuring the resulting track densities registered on the detectors utilized. The third technique is based on calculating the detection efficiencies of the CR-39 and LR-115 II SSNTD for α-particles emitted by the uranium and thorium series in the building materials or by the radon and thoron groups in air and measuring track density rates registered on these detectors. The influence of the building material's nature and ventilation rate on the thoron and its decay products inside the dwelling rooms studied has been investigated.

Microstructures of GaN Films Laterally Overgrown on Si(111) by Hydride Vapour Phase Epitaxy

We have investigated the microstructures of GaN films laterally epitaxiallyovergrown (LEO) on Si(111) substrates using hydride vapour phase epitaxy.The threading dislocation density in the LEO GaN isreduced by about two orders. Different etching angles of the twosidewalls of SiO2 masks (66o and 90o) lead tothe asymmetry of the LEO and cause the particular microstructures of LEOGaN. In micro-Raman spectra, the intensities vary weakly periodicallyabout 5 µm perpendicular to the mask stripes.The indistinct selective growth in the top surface is discussed.

Determination of equivalent dose rates and committed effective doses in the respiratory system from the inhalation of radon decay products by using SSNTD and a dosimetric compartmental model.

Alpha activities per unit volume, due to radon (222Rn), thoron (220Rn) and their progenies, were evaluated inside different dwelling rooms by using CR-39 and LR-115 II solid state nuclear track detectors (SSNTD) and calculating their mean critical angles of etching. The influence of the ventilation rate and nature of the building material has been investigated. Equivalent dose rates and annual committed effective doses due to the inhalation of radon decay products have been determined in the respiratory system by using a dosimetric compartmental model. The influence of the deposition fraction, residual time and activity absorbed fraction of the respiratory system compartments for the radon daughters has been studied.

Tailoring etch directionality in a deep reactive ion etching tool

Silicon deep reactive ion etching is a process that produces projected two-dimensional shapes due to the inability to control the direction of the energetic ions arriving at the surface of a wafer. The resulting etched profiles present sidewalls which are nominally 90° to the wafer surface. However, we have developed and demonstrated a new technique that allows us to control the angle that trenches make with respect to the wafer surface. This scheme exploits the charging of buried dielectric layers to achieve ion steering and thus control the direction of the etch. The measured angle variation was controlled between −32° and +32° with respect to a line orthogonal to the wafer surface. We report and describe this new technique to control etch angle.

The Influence of the Calcination and Water Washing Treatments on the Uranium Content in Sedimentary Phosphate Samples Using Solid State Nuclear Track Detectors and Gamma-Ray Spectrometry

The uranium and thorium contents were evaluated in the 100–400 µm granulometric fraction of different sedimentary phosphate samples by using a method based on determining the mean critical angles of etching of the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) for detecting α-particles emitted by the nuclei of the uranium-238 and thorium-232 series. Data obtained were compared with the results of γ-ray spectrometry measurements performed on the same samples. The influence of the calcination and water washing treatments as well as the lithology and stratigraphy on the uranium concentration of the phosphate samples was investigated.

On the use of Makrofol KG to study fission fragment angular distributions

Makrofol KG nuclear track detector processing and analysis is carefully regulated and assessed to reveal fission fragments’ tracks and their angular distributions. For this purpose, foils of this detector are irradiated by a thin 252 Cf source and are subjected to chemical etching followed by a two-step sparking process. The detector efficiency as a function of fission fragment incidence angle and different etching parameters is carried out with a good reproducibility.

Influence of electron irradiation of the NOVER-1 vacuum resist on its resistance to ionbeam etching

The influence of electron irradiation on the resistance of the NOVER-1 resist to ion-beam etching is studied. Etching is carried out by argon ions with energies between 300 and 2500 eV. It is found that, depending on the energy and angle of incidence of the ions on the surface of the resist, electron irradiation may either speed up or slow down the NOVER-1 etching. A clear correlation is observed between the penetration depth of the ions in the resist and the influence of the electron irradiation on the resistance of the resist to etching. At ion energies higher than 500 eV (ion penetration depth ≳3.5 nm) the resistance decreases, passes through a minimum at low electron irradiation doses, and returns to the etching rate of the initial resist at high doses. For glancing etching angles (∼ 70° to the surface normal) and low ion energies (300 eV), i.e., small ion penetration depths (≲2.5 nm), an electron-irradiated resist is etched more slowly than the initial resist at all the electron irradiation doses studied. This effect may be used to enhance the resistance of resist structures whose height exceeds their width, which in this case is determined mostly by the rate of etching of the inclined facets.

Reactive ion etching of benzocyclobutene polymer films

Reactive ion etching is a widely-used technique for fabricating via holes in polymer-metal multilayer interconnect structures. Reactive ion etching of thin film polymers was studied using Benzocyclobutene polymer and photoresist etch mask, in O/sub 2/ and SF/sub 6/ plasma. A design of experiments (DOE) was carried out with rf power, pressure, and SF/sub 6/ concentration as the design variables, with a constant total gas flow rate. The responses measured in this study were dc bias, etch rate, via angle, uniformity, selectivity, lateral etch rate, and etch cleanliness. The DOE revealed some complex relationships between variables. DC bias was a very important parameter for explaining the observed effects on etch rate, via angle, selectivity, and lateral etching. A simple model was formulated to explain the dependence of via angle on design variables. The etching characteristics of the photoresist mask affected not only the selectivity, but also the via angle and lateral etch rate. Due to conflicting requirements posed by the responses, optimization of the reactive ion etch (RIE) process involves many trade-offs which depend on the particular application.

Depth profiling by means of the combination of glancing incidence X-ray fluorescence spectrometry with low energy ion beam etching technique

Experiments using a combination of laterally resolved glancing incidence X-ray fluorescence spectrometry in the vicinity of the critical angle of total reflection and ion beam ramp etching were performed to work out a new technique for depth profiling in solid-state thin films with nanometre resolution. The lateral point-to-point resolution of the total-reflection X-ray fluorescence (TXRF) spectrometer used was determined as 200 ± 10 μm by means of standard samples (Cr bars on Si). At an inclination angle in the range of 10 −4 degrees for the ramp, which has been produced by ion beam etching, the geometrically covered depth is in the range of 1 nm. In order to demonstrate the potential of the new technique, preliminary results on Cu/Cr multilayers on Si substrate are presented.

Electron Spectroscopy for Chemical Analysis Study on Influence of Polymerization on Anisotropic Etching of Thick Silicon Oxide Using C 2F 6 Based ECR-RIBE

Anisotropic etching mechanism is investigated increasing the CF2 precursor in C2F6 plasma. The increasing of CF2 precursor is known from the ESCA (electron spectroscopy for chemical analysis) measurement of C/F elemental ratio of the deposited layer. It is found that the C/F ratio is increased from 0.28 to close to 1, when the microwave power of plasma is increased from 150 W to 350 W, respectively. The side wall angle of the deep SiO2 etching under the power of 350 W, is found to be close to 90°. The SiO2 etching selectivity with respect to the chromium (Cr) metal mask is also found to be enhanced considerably with the increasing of microwave power.

Characterisation of semi-insulating polysilicon oxygen doped silicon thin films

The optical properties of low pressure chemical vapour deposited semi-insulating polysilicon oxygen doped silicon (SIPOS) thin .films are characterised, using both in situ single wavelength (633 nm) ellipsometry with plasma etching and variable angle spectroscopic ellipsometry, as afunction of deposition and annealing conditions. Precise optical models for thin.film SIPOS are developed. Microstructural and chemical analysis is presented using cross-sectional transmission electron microscopy and secondary ion mass spectrometry.MST/3252