Etching Of Films Research Articles

Etch Characteristics of Copper Thin Films in Inductively Coupled Plasma of Piperidine/Ethanol/Ar Gas Mixture

High density plasma reactive ion etching of copper thin films patterned with SiO2 masks was performed via piperidine/ethanol/Ar gas mixture. The etch characteristics of the copper thin films were examined as functions of the gas concentrations in piperidine/Ar and piperidine/ethanol/Ar mixtures. As the piperidine concentration increased, the etch rates of the copper films decreased whereas the etch selectivities of the copper films to SiO2 mask increased and the etch profiles improved. Optical emission spectroscopy studies showed that the major active species in the plasmas of piperidine/Ar and piperidine/ethanol/Ar were CH and CN, which were responsible for the good etch profiles. Further, X-ray photoelectron spectroscopy revealed the formation of CuCN, copper compounds, and polymer layers. Finally, dry etching of copper thin films was successfully accomplished with the optimized piperidine/ethanol/Ar gas mixture, thereby obtaining good etch profiles with high degrees of anisotropy.

Reactive ion etching process of SiO2 film using on-site synthesized C2F4 from CF4

C2F4 is a potential etching gas for high aspect ratio etching of SiO2 films owing to its high etch rate. However, it is difficult to fill C2F4 to a gas cylinder with high pressure for mass production due to its high reactivity. To overcome this problem, we developed an etching system, where the on-site synthesized C2F4 from CF4 using a VHF plasma was supplied directly into the etching reactor. It was demonstrated that SiO2 etching using synthesized-C2F4/O2/Ar gas mixture plasma was carried out successfully and the etch rate became 2.7 times higher than that of CF4/O2/Ar gas mixture plasma.

High-Frequency Acoustic Imaging Using Adhesive-Free Polymer Transducer.

The piezoelectric polymer PVDF and its copolymers have a long history as transducer materials for medical and biological applications. An efficient use of these polymers can potentially both lower the production cost and offer an environment-friendly alternative for medical transducers which today is dominated by piezoelectric ceramics containing lead. The main goal of the current work has been to compare the image quality of a low-cost in-house transducers made from the copolymer P(VDF-TrFE) to a commercial PVDF transducer. Several test objects were explored with the transducers used in a scanning acoustic microscope, including a human articular cartilage sample, a coin surface, and an etched metal film with fine line structures. To evaluate the image quality, C- and B-scan images were obtained from the recorded time series, and compared in terms of resolution, SNR, point-spread function, and depth imaging capability. The investigation is believed to provide useful information about both the strengths and limitations of low-cost polymer transducers.

Surface Etching of Polymeric Semiconductor Films Improves Environmental Stability of Transistors

Solution-processed polymeric semiconductor films are attracting wide interest for applications in flexible electronics, wherein environmental stability is still a big obstacle. In many polymeric th...

Effect of Hexafluoroisopropanol Addition on Dry Etching of Cu Thin Films Using Organic Material

Effect of Hexafluoroisopropanol Addition on Dry Etching of Cu Thin Films Using Organic Material

Effect of Hydrogen Ion Energy in the Process of Reactive Ion Etching of Sn Thin Films by Hydrogen Plasmas

Effect of Hydrogen Ion Energy in the Process of Reactive Ion Etching of Sn Thin Films by Hydrogen Plasmas

Foundations of capacitive and inductive radio-frequency discharges

This paper is the first from a set of two companion papers on radio-frequency (RF) discharges. These two papers are in turn part of a larger series on the foundations of plasma and discharge physics. In this part we cover the basics of non-magnetized capacitive and inductive RF discharges, introduce the main concepts related to them and provide reference literature for further reading. In the second part we concentrate on RF discharges in the presence of external magnetic field. These types of RF discharges find a wide range of applications in various industries. Among the most prominent examples are the microelectronics industry for etching and deposition of thin films, the medical and food industry for the application of various coatings and changing the wettability of surfaces, the space industry to power ion-gridded thrusters for satellites, the fusion and elementary particle research for the production of beams of energetic ions or atoms. The paper introduces the basic concepts of RF power deposition and describes in more detail the operating conditions of the plasma reactors. The most important physical phenomena encountered in these discharges are outlined through the use of simplified models. The paper is intended as an entry point for newcomers to the field and provides ample of references (including textbooks) for further reading on the more specific and/or subtle aspects of the operation of these types of RF discharges.

Roughness and Uniformity Control during Wet Etching of Molybdenum

In this work the wet etching of molybdenum thin films was investigated for applications requiring controlled recess without roughening or pattern loading. First, continuous etching of Mo in alkaline and oxidative peroxide solutions was studied. Then, additives like glycine and diethylenetriamine were used and their effect on etch rate and roughness was assessed. Finally, we evaluated if the requirements for a stepwise etching approach for Mo recess using peroxide or ozonated water as the oxidizing step and ammonia as the oxide dissolution agent were met.

Athermal high-Q tantalum-pentoxide-based microresonators on silicon substrates

Integrated microresonators with low thermal drift of resonant wavelength are imperative photonic devices to provide stable multiplexing/filtering functions on silicon substrates with large thermo-optic coefficient. To realize athermal microresonators with high quality factor and small footprint, we present an undercut Ta2O5-based microdisk resonator on the Si substrate using a facile lift-off process on the sputtered film and chemical etching. Dependences of surface morphology, crystalline property, refractive index and extinction coefficient of Ta2O5 film on the annealing temperature are studied to reveal favorable parameters for the microresonator production. The produced 40 μm-diameter Ta2O5 microdisk resonator exhibits low thermal drift (7.40 pm/°C), high quality factor (1.65 × 104) and wide free spectral range (11.5 nm). The measured thermo-optic coefficient at the wavelength 1550 nm is 3.0 × 10−6/°C. The thermal stability is further enhanced by using the TiO2 film with the negative thermo-optic coefficient. The study of Ta2O5/TiO2 composite microdisk resonators achieves high thermal stability as best as 0.26 pm/°C.

Reactive ion etching of PbSe thin films in CH4/H2/Ar plasma atmosphere

In this work, we reported a reactive ion etching of PbSe thin films on silicon in CH4/H2/Ar plasma atmosphere. Various etching parameters that affect dc self-bias, the etching rate and the etching smoothness of the surface and sidewalls, including rf power, gas ratio, and process pressure, have been systematically investigated. It is found that the dc self-bias has an approximate linear relationship with rf power, but it decreases as the process pressure increases. The etching rate increases with increasing rf power and decreasing process pressure. Additionally, the etching rate increases to the maximum as CH4 percentage increases to 40%, beyond which it decreases with further increasing CH4 percentage due to formation of polymer. Furthermore, SEM results show that for all investigated samples except one etched in atmosphere with 60% CH4, the etched surfaces are smooth, and the sidewalls are vertical. The etched profile of sample etched in atmosphere with 60% CH4 is very rough, which should be attributed to formation of polymer as well.

Плазмохимическое травление тонких пленок серебра для приложений плазмоники индуктивно-связанной аргоновой плазмой

The study focuses on the processes of plasma-chemical etching of silver films for the manufacture of photonic elements --- nanoscale light sources, and examines the theoretical foundations of etching processes and the process of plasma formation in plasma-chemical etching facilities. We assessed the introduced technology when forming topological elements in thin films of silver metal, and identified key problems, such as redeposition and non-volatility of the material. The paper presents the results of simulating the etching process for several critical submicron sizes, and, based on the simulation results, shows the dependences of the etching rates on the power of the plasma sources. The focus is on the formation of holes to create a nanoscale light source. Both positive and negative properties of the plasma-chemical etching method using a source of inductive-coupled plasma are considered, and the features of technological facilities used for these processes are outlined. The process of formation of nanoelements in a silver film and the effect of redeposition of material particles as a result of ion sputtering are considered. We propose a two-stage etching process, which makes it possible to form a vertical profile of the walls of the manufactured elements and to avoid the effect of redeposition. We also give recommendations for the processes of etching through an electron-beam resist in facilities with an inductive-coupled plasma source. By optimizing the thicknesses of the resistive mask and plasma sources, we obtained the results of etching nanoscale elements with preservation of geometric shapes

The Role of Oxygen on Anisotropy in Chromium Oxide Hard Mask Etching for Sub-Micron Fabrication

Chromium and its oxides have been playing a vital role in the fabrication of micro- and nano-scale structures in numerous applications for several decades. Controllable, robust and anisotropically dry-etched hard masks and their optimal etch recipes are required in state-of-the-art device fabrication techniques. In terms of manufacturability and repeatability, a mechanistic understanding of the plasma-etching process of chromium oxide (Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) is necessary for its adoption as a hard mask. We present a systematic investigation of plasma etching of chromium oxide films via an inductively coupled plasma-reactive ion etching (ICP-RIE) system in nanoscale. The effects of plasma composition, ICP source power and HF platen power on the etch rate, sidewall profile, surface morphology, and dc-bias have been methodically investigated. We paid particular attention to studying how oxygen content can be used to control the etch profile of nano trenches using chlorine/oxygen gas mixtures, including extremes of very low and very high oxygen content. It was found that chromium oxide etch mechanisms are dependent strongly on the oxygen level. We achieved desirable vertical sidewalls with reasonable etch rates when the oxygen content is in the range 10-40% in the plasma. Oxygen content below 10% resulted in positively tapered etch profiles with low etch rates. On the other hand, bowl-like etch profiles with undercut formation was observed at high oxygen content above 40%, caused by re-emission of the reactive species at this regime. As a hard mask material, patterning Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> films compared to Cr metal is advantageous in terms of etch uniformity and reproducibility. Contrary to Cr, Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> is not as sensitive to chamber wall conditions.

Surface topology engineering of ferroelectric polymer film by high-pressure plasma etching

Oxygen plasma processis usually implemented for selective etching of organic films. The oxygen plasma etches the organic materials non-uniformly, the deep etching generatesthe rough surface morphology. However, high-pressure plasma environment can maintain the initial surface status independent of etching depth. Here, a high-pressureplasma etching method that can reduce the surface roughness of ferroelectric polymer film is presented. After an amorphous polymer having the same etching rate is formed, the surface of the amorphous polymer film is treated with a plasma, which makes it possible to have a smoother surface than the original film. This process is expected to be useful for the surface treatment of all crystalline polymers, including ferroelectric polymers.

Defect depth-profiling in kesterite absorber by means of chemical etching and surface analysis

A method to probe the depth morphology, defect profile and possible secondary phases in a thin film semiconductor is presented, taking a standard Kesterite film as an example. Using a top-down approach based on a previously reported controlled Methanol-Br2 chemical etching, well-defined slabs of a state of the art Kesterite absorber are fabricated. The analysis of their morphology both by Scanning Electron Microscopy and 3D optical Profilometry reveals the extent of a previously reported poor film morphology toward the back interface, and we are able to determine that more than 50% of a standard absorber is disconnected from the substrate. More importantly, these etched films are subsequently analyzed by surface sensitive techniques such as X-ray Photoelectron Spectroscopy and UV-Raman analysis. An accurate composition profile is established, and for the first time, a direct observation of the defects’ nature and their depth profiling in Kesterite is made possible. While VCu are found with a constant amount throughout the absorber, indicating a homogenous carrier concentration, a prevalence of the ZnSn defect is observed with a steep gradient toward the back interface, associated with an increase in the SnSe2 secondary phase. With bulk defects being often pointed out as the intrinsic limitation of this material, this result highlights what possibly is the main impediment of Kesterite solar cells, and a critical point to address in the design of future devices. Beyond the case of Kesterite absorbers, the method presented here offers a combination of simplicity, tunability and versatility making a straightforward transfer to other emerging thin film absorbers feasible, and it could possibly be an important tool in their future performance assessment and comparison.

Effect of etching time onto structural, morphological, and optical characteristics of quaternary AlInGaN films on Si substrate

Ultraviolet-assisted photoelectrochemical (PEC) etching of quaternary AlInGaN films on Si in an alkaline solution has transformed the nano-islands film to nano-dendritic like and spikes as the etching duration was varied from 5 to 20 min. Al3+ cations that possessed better solubility than In3+ and Ga3+ were preferably etched off from the films at a shorter duration (5 and 10 min). Lattice expansion took place and an improvement in photoluminescence (PL) intensity in blue-green wavelength regions was obtained. Further increase of the etching time beyond 10 min facilitated the removal of In3+ along with Al3+, yielding a decrease in the PL intensity and shifting the wavelength to blue-red region. A decrease in the E2(high) InGaN and E2(high) AlGaN was observed as the etching time was increased. Discussion about the defect density as well as the etching mechanism that eventually led to the formation of dendrites and spikes was also presented.

Fluctuation Effects of Magnetohydrodynamic Micro-Vortices on Odd Chirality in Magnetoelectrolysis

The magnetic field dependence of chiral surface formation was investigated in magnetoelectrodeposition (MED) and magnetoelectrochemical etching (MEE) of copper films. The MED and MEE was conducted in magnetic fields of up to 5 T, which were parallel or antiparallel to the ionic currents. The MED films prepared in high magnetic fields of 5 and 3 T exhibited odd chirality for magnetic field polarity, as expected on the basis of the magnetohydrodynamic (MHD) vortex model. However, the films prepared in the lower fields of 2.5 and 2 T exhibited breaking of odd chirality. Similar magnetic field dependence was observed in the surface chirality of MEE films. These results imply that the fluctuation in the self-organized state of micro-MHD vortices is responsible for the breaking of odd chirality.

Effects of UV-ozone treatment on the electronic structures of F8BT and PFO polymeric thin films

The property changes of polymeric films upon degradation are important to develop strategies to prolong the device lifetimes. In this regard, we investigated the effects of ultraviolet-ozone (UVO) treatment on the electronic structures of poly (9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) and poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) films. We found that as the UVO treatment time increased, the intensities of the UV–vis and photoluminescence spectra of both F8BT and PFO films exponentially decayed owing to the destruction of the conjugated system of the films. As per the X-ray photoelectron spectra, both the F8BT and PFO films showed significant oxidation and p-doping effects upon UVO treatment. In addition, UVO treatment caused the etching of the polymeric films, and their thickness gradually decreased; the etching rate with UVO treatment was faster for PFO than for F8BT. These results indicate that the functionalization of polymers with UVO treatment requires the careful consideration of the resulting changes in their electronic structure.

Skyrmion Brownian circuit implemented in continuous ferromagnetic thin film

The fabrication of a circuit capable of stabilizing skyrmions is important for the realization of micro- to nano-sized skyrmion devices. Ultralow power Brownian computers have been theoretically proposed and are a promising example of a skyrmion-based device. However, such devices have not been realized as it would require skyrmions to be stabilized and easily movable within a circuit. Skyrmion circuits fabricated by the etching of ferromagnetic films often decrease the dipolar magnetic field stabilizing the skyrmions, thus preventing their formation. In this study, a skyrmion Brownian circuit has been implemented in a continuous ferromagnetic film with patterned SiO2 capping to stabilize the skyrmion formation. The patterned SiO2 capping controls the saturation field of the ferromagnetic layer and forms a wire-shaped skyrmion potential well, which stabilizes skyrmion formation in the circuit. Moreover, using this patterned SiO2 capping, we have implemented a Y-junction hub circuit exhibiting no pinning site at the junction, contrary to conventional etched hubs. Thus, this technique enables the efficient control of skyrmion-based memory and logic devices to move closer toward the realization of Brownian computers.

Silver film etching using halogen gas plasma

Silver (Ag) film etching was studied with a focus on suppressing the surface roughness induced by Cl2 and CF4 plasmas. After Cl2 plasma etching, roughening of the Ag surface was observed. From in situ x-ray photoelectron spectroscopy and atomic force microscopy analyses using a plasma beam system, the Ag surface was roughened with AgCl formation after Cl2 plasma treatment before exposure to air. In capacitively coupled Cl2 plasma, it seemed that many voids were formed on the Ag surface at a high bias power and cathode temperature. This was considered to be characteristic of agglomeration. In contrast, severe surface roughness was not observed after CF4 plasma etching, even at a high bias power and cathode temperature. Secondary ion mass spectrometry analysis showed high chlorine accumulation near the Ag film surface after Cl2 plasma etching. Possible agglomeration of the Ag film during Cl2 plasma etching was volume expansion caused by chlorine accumulation assumed to enhance the compressive stress of the Ag film, and this resulted in increased boundary grooving and, finally, agglomeration. In contrast, fluorine accumulation was unlikely during CF4 plasma etching, resulting in less Ag film stress, which suppressed grain boundary grooving and agglomeration.

Investigation of organic precursors and plasma mixtures allowing control of carbon passivation when etching HgCdTe in hydrocarbon-based inductively coupled plasmas

Our interest in introducing oxygen and/or nitrogen atoms in CH4/H2/Ar plasma mixtures by means of organic precursors in the place of CH4 or by partly substituting O2 or N2O for H2 and thereby controlling carbon deposition and surface passivation when etching HgCdTe under low substrate bias conditions is investigated in this study. Using in situ ellipsometry, in situ x-ray photoelectron spectroscopy, atomic force microscopy, and secondary electron microscopy (SEM), we show that nitromethane as a precursor and N2O substitution are attractive alternatives for the following: the absence of deposition although no bias is applied, equivalent postetch surface composition, and comparable performances in terms of etch rate and surface roughness for the latter. Such an approach could provide the soft dry etching conditions needed to reduce the pixel pitch of HgCdTe infrared photovoltaic detectors. The mechanisms that allow suppressing carbon deposition upon O2 or N2O substitution in CH4/H2/Ar plasmas are studied by combining plasma diagnostics (optical emission spectroscopy, actinometry, and ion flux measurements) and surface characterizations. First, using Si as a reference substrate, it is shown that deposition is suppressed whenever the O2 and N2O flow rate is half and twice that of CH4, respectively. Moreover, the study reveals that oxygen is the true etch reactant controlling the competition between film growth and etching in both substituted processes, whereas incorporation of nitrogen in the film upon N2O substitution favors its etching kinetics simultaneously. Second, on HgCdTe, deposition of a hydrocarbonitride film is observed at a low N2O/CH4 ratio (∼0.6). SEM and SEM-energy dispersive x-ray spectroscopy imaging suggest that the film nucleates and grows preferentially on regions where the Cd removal mechanisms happen to be less efficient. At a high N2O/CH4 ratio (∼4), oxidation of the HgCdTe surface is observed.