High Density Magnetically Confined Dry Etching of Metallization and Dielectrics in Gaas Device Technology

1994 ◽  
Vol 337 ◽  
Author(s):  
S. J. Pearton ◽  
C. R. Abernathy ◽  
F. Ren ◽  
J. R. Lothian ◽  
R. F. Kopf ◽  
...  
Keyword(s):  
Low Temperature ◽  
Dry Etching ◽  
Ex Situ ◽  
Chemical Cleaning ◽  
Magnetically Confined ◽  
Wet Chemical ◽  
Etch Rates ◽  
Materials Used ◽  
Device Technology

ABSTRACTDry etching of common masking materials used in GaAs device technology was examined down to temperatures of −30°C. The etch rates of SiNx, SiO2 and W in SF6/Ar are reduced below 0°C, but the anisotropy of the etching is improved at low temperature. Microwave enhancement of the SF6/Ar discharges produces increases in etch rates of several times at 25°C, but much lower increases at −30°C substrate temperature. The underlying GaAs surface shows increased S and F coverage after low temperature etching, but these species are readily removed either by an ex-situ wet chemical cleaning step or an in-situ H2 plasma exposure. Photoresist etching is less sensitive to temperature and anisotropic profiles are produced between −30 and + 60°C in pure 02 discharges.

In-situ AFM study of the crystallization and pH-dependent stability of ZnO(0001)-Zn surfaces

2007 ◽  
Vol 1035 ◽  
Author(s):  
Markus Valtiner ◽  
Guido Grundmeier
Keyword(s):  
Electrolyte Solutions ◽  
Ex Situ ◽  
Chemical Cleaning ◽  
Single Crystalline ◽  
Afm Imaging ◽  
Wide Range ◽  
Wet Chemical ◽  
Ph Dependent ◽  
Crystalline Surfaces

AbstractPolar ZnO(0001)-Zn surfaces can be prepared as very well defined and single crystalline surfaces by hydroxide stabilization simply by introducing hydroxides via a wet chemical cleaning step. Within this proceeding we present an in-situ AFM imaging of the crystallization process. The pH dependent stability of the resulting hydroxide-stabilized surfaces was further investigated by means of an ex-situ LEED approach. These investigations show, that it is possible to obtain high quality single crystalline ZnO(0001)-Zn surfaces in a simple way. Moreover, these surfaces turned out to be very stable within a wide range of pH values between 11 and 3 of NaClO4 based 1mM electrolyte solutions.

Cleaning of Silicon Surfaces for Nanotechnology

2008 ◽  
Vol 573-574 ◽  
pp. 77-117 ◽  
Author(s):  
Oliver Senftleben ◽  
Hermann Baumgärtner ◽  
Ignaz Eisele
Keyword(s):  
Surface Roughness ◽  
High Mobility ◽  
Crystal Defects ◽  
Silicon Surfaces ◽  
Ex Situ ◽  
Chemical Cleaning ◽  
Gas Atmosphere ◽  
Wet Chemical ◽  
Device Properties

An overview of various cleaning procedures for silicon surfaces is presented. Because in-situ cleaning becomes more and more important for nanotechnology the paper concentrates on physical and dry chemical techniques. As standard ex-situ wet chemical cleaning has a significant impact on surface quality und thus device properties, its influence on further processes is also considered. Oxygen and carbon are unavoidable contaminations after wet chemical treatment and therefore we discuss their in-situ removal as one of the main goals of modern silicon substrate cleaning. As surface roughness strongly influences the electrical quality of interfaces for epitaxy and dielectric growth, we concentrate on techniques, which meet this requirement. It will be shown that multi-step thermal sequences in combination with simultaneous passivation of the clean surface are necessary in order to avoid recontamination. This can be achieved not only for ultra hich vacuum but also for inert gas atmosphere. In this case the process gases have to be extremely purified and the residual partial pressure of contaminats such as oxygen and carbon has to be negligible. It will be demonstrated that 800°C is an upper limit for thermal treatment of silicon surfaces in the presence of carbon because at this temperature SiC formation in combination with a high mobility of silicon monomers leads to surface roughness. In addition mechanical stress causes dislocations and crystal defects.

scholarly journals Start-up Strategies for Anaerobic Ammonia Oxidation (Anammox) in In-Situ Nitrogen Removal from Polluted Groundwater in Rare Earth Mining Areas

2021 ◽  
Vol 13 (8) ◽  
pp. 4591
Author(s):  
Shuanglei Huang ◽  
Daishe Wu
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Removal Efficiency ◽  
Nitrogen Removal ◽  
Ex Situ ◽  
High Concentration ◽  
Low Concentration ◽  
Start Up ◽  
Anammox Activity

The tremendous input of ammonium and rare earth element (REE) ions released by the enormous consumption of (NH4)2SO4 in in situ leaching for ion-adsorption RE mining caused serious ground and surface water contamination. Anaerobic ammonium oxidation (anammox) was a sustainable in situ technology that can reduce this nitrogen pollution. In this research, in situ, semi in situ, and ex situ method of inoculation that included low-concentration (0.02 mg·L−1) and high-concentration (0.10 mg·L−1) lanthanum (La)(III) were adopted to explore effective start-up strategies for starting up anammox reactors seeded with activated sludge and anammox sludge. The reactors were refrigerated for 30 days at 4 °C to investigate the effects of La(III) during a period of low-temperature. The results showed that the in situ and semi in situ enrichment strategies with the addition of La(III) at a low-concentration La(III) addition (0.02 mg·L−1) reduced the length of time required to reactivate the sludge until it reached a state of stable anammox activity and high nitrogen removal efficiency by 60–71 days. The addition of La(III) promoted the formation of sludge floc with a compact structure that enabled it to resist the adverse effects of low temperature and so to maintain a high abundance of AnAOB and microbacterial community diversity of sludge during refrigeration period. The addition of La(III) at a high concentration caused the cellular percentage of AnAOB to decrease from 54.60 ± 6.19% to 17.35 ± 6.69% during the enrichment and reduced nitrogen removal efficiency to an unrecoverable level to post-refrigeration.

scholarly journals Optimization of In Situ Backwashing Frequency for Stable Operation of Anaerobic Ceramic Membrane Bioreactor

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 545 ◽  
Author(s):  
Rathmalgodage Thejani Nilusha ◽  
Tuo Wang ◽  
Hongyan Wang ◽  
Dawei Yu ◽  
Junya Zhang ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Membrane Bioreactor ◽  
Ceramic Membrane ◽  
Pure Water ◽  
Ex Situ ◽  
Stable Operation ◽  
Chemical Cleaning ◽  
Cake Layer

The cost-effective and stable operation of an anaerobic ceramic membrane bioreactor (AnCMBR) depends on operational strategies to minimize membrane fouling. A novel strategy for backwashing, filtration and relaxation was optimized for stable operation of a side stream tubular AnCMBR treating domestic wastewater at the ambient temperature. Two in situ backwashing schemes (once a day at 60 s/day, and twice a day at 60 s × 2/day) maintaining 55 min filtration and 5 min relaxation as a constant were compared. A flux level over 70% of the initial membrane flux was stabilized by in situ permeate backwashing irrespective of its frequency. The in situ backwashing by permeate once a day was better for energy saving, stable membrane filtration and less permeate consumption. Ex situ chemical cleaning after 60 days’ operation was carried out using pure water, sodium hypochlorite (NaOCl), and citric acid as the order. The dominant cake layer was effectively reduced by in situ backwashing, and the major organic foulants were fulvic acid-like substances and humic acid-like substances. Proteobacteria, Firmucutes, Epsilonbacteria and Bacteroides were the major microbes attached to the ceramic membrane fouling layer which were effectively removed by NaOCl.

Electrical Evaluation of the Epi/Substrate Interface Quality after Different In-Situ and Ex-Situ Low-Temperature Pre-Epi Cleaning Methods

1998 ◽  
Vol 65-66 ◽  
pp. 237-240 ◽  
Author(s):  
Matty Caymax ◽  
S. Decoutere ◽  
Erika Röhr ◽  
W. Vandervorst ◽  
Marc M. Heyns ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ex Situ ◽  
Interface Quality ◽  
Substrate Interface ◽  
Cleaning Methods

Improvement of Gaas Crystal Quality on Si Grown by Mocvd Through Two-Dimensional-Like Nucleation with Low Temperature in Situ Hydrogen/Arsine Plasma Cleaning

1990 ◽  
Vol 202 ◽  
Author(s):  
Euijoon Yoon ◽  
Rafael Reif
Keyword(s):  
Low Temperature ◽  
Buffer Layer ◽  
Crystal Quality ◽  
Ex Situ ◽  
Plasma Cleaning ◽  
Two Dimensional ◽  
Gaas Crystal ◽  
Hydrogen Atoms ◽  
Slow Kinetics

ABSTRACTWe report the significant improvement of GaAs crystal quality on Si grown by metal-organic chemical vapor deposition (MOCVD) with an in situ low temperature hydrogen/arsine plasma cleaning of the Si substrate at 450°C and a consequent controlled two-dimensional-like morphology of the low temperature buffer layer at its early stage. The most critical step that determines the interfacial cleanliness and the early stages of the nucleation and thin film formation of heteroepitaxial GaAs on Si in a non-ultrahigh vacuum MOCVD system is the substitution of hydrogen atoms passivating the Si surface after ex situ HF-dip with pas-sivating As atoms. Reduction of in situ cleaning temperature ensures the very slow kinetics of thermal desorption of the hydrogen atoms and re-oxidation of exposed Si surface from the reactor environment, and provides a fully As-passivated Si surface, leading to a 2D-like buffer layer.

Dry Surface Cleaning of Plasma-Etched Hemts

1992 ◽  
Vol 282 ◽  
Author(s):  
S. J. Pearton ◽  
F. Ren ◽  
A. Katz ◽  
U. K. Chakrabarti ◽  
E. Lane ◽  
...  
Keyword(s):  
Electron Cyclotron Resonance ◽  
High Electron Mobility Transistors ◽  
Surface Cleaning ◽  
High Electron ◽  
Chemical Cleaning ◽  
Electron Mobility Transistors ◽  
Short Period ◽  
Wet Chemical ◽  
Dry Etch

ABSTRACTFabrication of sub-micron high electron mobility transistors (HEMTs) involves dry etch removal of GaAs from an underlying AlGaAs or InGaAs stop layer. The etch selectivity is achieved by formation of AlF3 on AlGaAs, or InCl3 and InF3 on InGaAs, which must be removed before processing can proceed. Wet chemical cleaning has difficulty in such a situation because of surface tension effects. We have investigated use of Electron Cyclotron Resonance (ECR) H2 or Ar discharges, or hexafluoroacetylacetone (HFAC) vapor, for in-situ dry etch cleaning of HEMTs exposed to low bias BCl3/SF6 discharges. The HFAC vapor can remove most of the remnant fluorine, but is effective only when the sample is heated above ∼250°C. This relatively high temperature is not compatible with in-situ cleaning of the etched device. Low-bias(−75V) sputter cleaning with an Ar discharge removes all remnant Cl and ∼40% of the F, but dc biases above -125V are required for complete cleaning, and this ion bombardment can lead to damage in the HEMT. ECR H2 discharge exposure is effective in removing all Cl- and F-related residues in a short period (∼5 mins) with low dc biases (−25 V) on the sample.

In Situ Low Temperature Cleaning and Passivation of Silicon by Remote Hydrogen Plasma for Silicon-Based Epitaxy

1992 ◽  
Vol 259 ◽  
Author(s):  
S. Banerjee ◽  
A. Tasch ◽  
T. Hsu ◽  
R. Qian ◽  
D. Kinosky ◽  
...  
Keyword(s):  
Low Temperature ◽  
Hydrogen Plasma ◽  
High Vacuum ◽  
Substantial Reduction ◽  
Surface Cleaning ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Remote Plasma ◽  
Air Exposure

ABSTRACTRemote Plasma-enhanced Chemical Vapor Deposition (RPCVD), which involves nonthermal, remote plasma excitation of precursors, has been demonstrated to be a novel and attractive technique for low temperature (150-450C) Si and Sil-xGex epitaxy for applications in Si ULSI and novel Si heterostructure devices which require compact doping profiles and/or heterointerfaces. An in situ low temperature remote hydrogen plasma clean in the Ultra-High Vacuum (UHV) deposition chamber in order to achieve a chemically passive, hydrogenated Si surface with minimal O, C and N contamination, is a critical component of the process. The ex situ wet chemical cleaning consists of ultrasonic degreasing and a modified RCA clean, followed by a final dilute HF dip. The in situ clean is achieved by remote plasma excited H, where H introduced through the plasma column is r-f excited such that the plasma glow does not engulf the wafer. In situ AES analysis shows that the remote H plasma clean results in very substantial reduction of the C, O and N contamination on the Si surface. We believe that the H plasma produces atomic H which, in turn, produces a reducing environment and has a slight etching effect on Si and SiO2 by converting them to volatile byproducts. TEM analysis of the wafers subjected to this clean indicate that defect-free surfaces with dislocation loop densities below TEM detection limits of 105 /cm2 are achievable. Corroborating evidence of achieving an atomically clean, smooth Si surface by remote H plasma clean as obtained from in situ RHEED analysis will also be presented. After in situ H cleaning at low pressures (45 mTorr), typically for 30 min. at a substrate temperature of 310 C, we observe both stronger integral order streaks compared to the as-loaded sample and the appearance of less intense half-order lines indicative of a (2 × 1) reconstruction pattern, indicating a monohydride termination. A (3 × 1) reconstruction pattern is observed upon H plasma clean at lower temperatures (250 C), which can be attributed to an alternating monohydride and dihydride termination. Results of air exposure of hydrogenated Si surfaces by AES analysis indicate that the (3 × l) termination is chemically more inert towards readsorption of C and 0. Successful Si homoepitaxy and Si/Sil-xGex heteroepitaxy under a variety of surface cleaning conditions prove that by a combination of these cleaning techniques, and by exploiting the inertness of the H-passivated Si surface, very low defect density films with 0 and C levels as low as 1X1018 cm−3 and 5×1017 cm−3, respectively, can be achieved.

scholarly journals Process Steps for High Quality Si-Based Epitaxial Growth at Low Temperature via RPCVD

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3733
Author(s):  
Jongwan Jung ◽  
Baegmo Son ◽  
Byungmin Kam ◽  
Yong Sang Joh ◽  
Woonyoung Jeong ◽  
...  
Keyword(s):  
Low Temperature ◽  
Epitaxial Growth ◽  
Chemical Vapor ◽  
Epitaxial Films ◽  
Ex Situ ◽  
High Quality ◽  
Reduced Pressure ◽  
Dry Cleaning ◽  
Gaseous Environment

The key process steps for growing high-quality Si-based epitaxial films via reduced pressure chemical vapor deposition (RPCVD) are investigated herein. The quality of the epitaxial films is largely affected by the following steps in the epitaxy process: ex-situ cleaning, in-situ bake, and loading conditions such as the temperature and gaseous environment. With respect to ex-situ cleaning, dry cleaning is found to be more effective than wet cleaning in 1:200 dilute hydrofluoric acid (DHF), while wet cleaning in 1:30 DHF is the least effective. However, the best results of all are obtained via a combination of wet and dry cleaning. With respect to in-situ hydrogen bake in the presence of H2 gas, the level of impurities is gradually decreased as the temperature increases from 700 °C to a maximum of 850 °C, at which no peaks of O and F are observed. Further, the addition of a hydrogen chloride (HCl) bake step after the H2 bake results in effective in-situ bake even at temperatures as low as 700 °C. In addition, the effects of temperature and environment (vacuum or gas) at the time of loading the wafers into the process chamber are compared. Better quality epitaxial films are obtained when the samples are loaded into the process chamber at low temperature in a gaseous environment. These results indicate that the epitaxial conditions must be carefully tuned and controlled in order to achieve high-quality epitaxial growth.

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