Early Stage Of Etching Research Articles

Experimental and simulation studies on temporal evolution of chemically etched Si surface: Tunable light trapping and cold cathode electron emission properties

Anisotropic alkaline etching of single crystalline p-Si(100) substrates is carried out for different times (in the range of 30–2400 s). This leads to the formation of randomly distributed pyramidal structures on Si surfaces, as observed from atomic force microscopy (AFM) and scanning electron microscopy images. During early stages of etching, rough surfaces evolve, but for longer etching times, pyramidally textured surfaces (having dimensions in the range of 0.2–2 μm) are formed. The formation of pyramidal structures is explained in light of simulation studies based on the continuum theory of stress-induced morphological instability. The power spectral density plots extracted from the experimental AFM images and the simulated images show that while the correlation length increases for lower etching times, it gets saturated for higher etching times. These facts corroborate well with our experimental results that reveal increasing pyramidal size with etching time. In addition, we study the temporal evolution of antireflection and field emission properties of such pyramidally textured-silicon substrates in line with their potential use in solar cells and moderate level cold cathode electron emission, respectively. For instance, it is interesting to note that surface reflectance of these pyramidally textured surfaces (formed at higher etching times) can be brought down to as low as 0.4% over a broad spectral range, viz., 300–3000 nm. Likewise, the field emission data show that turn-on potential decreases with increasing etching time (e.g., 2.62 V μm−1 for an etching time of 1200 s).

Fabrication and optical characterization of Si nanowires formed by catalytic chemical etching in Ag2O/HF solution

An etchant system, Ag2O–HF–H2O, was used to fabricate vertically aligned Si nanowire (SiNW) arrays on Si wafers. The synthesis was based on catalytic etching and produced large-area brushlike SiNWs on Si wafers. The Ag2O concentration was varied from 0.001 to 0.1mol/L and various synthesis conditions were optimized. The synthesized SiNWs were investigated by Fourier-transform infrared spectroscopy analysis, optical absorption, and contact-angle measurements. Spectroscopic ellipsometry was also used to assess the surface roughness produced in the early stage of etching. The optical measurements revealed that the SiNWs have high optical absorbance from the far infrared to ultraviolet regions. Passive HF etching of the SiNWs changed their wettability from superhydrophilic (∼0°) to highly hydrophobic (∼135°). The effect of sulfuric peroxide mixture (SPM) cleaning on the SiNW formation properties was also examined.

Evolution of Etch Profile of Magnetic Tunnel Junction Stacks Etched in a CH3OH/Ar Plasma

Etch characteristics of magnetic tunnel junction (MTJ) stacks masked with W/TiN films were investigated using an inductively coupled plasma reactive ion etching in a CH3OH/Ar gas. The effect of CH3OH concentration on the etch rate, etch selectivity and etch profile of MTJ stacks was examined. The high degree of anisotropy of etched MTJ stacks at high CH3OH concentrations resulted from the high etch selectivity of MTJ stacks to hard mask which was closely related with the high ratio of [H]/[Ar] peaks obtained by optical emission spectroscopy. The evolution of etch profile of MTJ stacks was examined to elucidate the etch mechanism in a CH3OH/Ar gas. Transmission electron microscopy of the etched MTJ stacks revealed the redeposition on the sidewall of MTJ stacks occurred during the early stage of etching and the gradual sputtering-off of the redeposited materials during further etching, resulting in a high degree of anisotropy. In addition, the redeposited materials turn out to be mainly Pt and Mn with low levels of Co and Fe by using energy dispersive X-ray spectroscopy

Extending ion-track lithography to the low-energy ion regime

Ion tracking and ion-track lithography have been performed almost exclusively using ions with energies near or above the maximum in electronic stopping, which occurs at ∼1MeV∕amu. In this paper, ion-track lithography using ions with energies well below this maximum is discussed. The results of etching ion tracks created in polycarbonate films by ions with energies just above the anticipated threshold for creating etchable latent tracks with cylindrical geometry have been examined. Low-energy neon and argon ions with 18–60keV∕amu and fluences of ∼108cm−2 were used to examine the limits for producing useful, etchable tracks in polycarbonate films. By concentrating on the early stages of etching (i.e., ∼20nm<scanning electron microscopy hole diameter <∼100nm), the energy deposition calculated for the incident ion was correlated with the creation of etchable tracks. The experimental results are discussed with regard to the energy losses of the ions in the polycarbonate films and to the formation of continuous latent tracks through the entire thickness of the films. The probability distributions for large-angle scattering events were calculated to assess their importance as a function of ion energy. All these results have significant implications with respect to the threshold for formation of etchable tracks and to the use of low-energy ions for lithographic applications of ion tracking.

Understanding the Role of Oxidative Etching in the Polyol Synthesis of Pd Nanoparticles with Uniform Shape and Size

Uniform cubooctahedral nanoparticles of Pd were synthesized using a modified polyol process. Like the silver system, the Pd nanoparticles underwent dissolution due to oxidative etching by Cl-/O2. In the early stage of etching, the twinned particles in a sample were selectively removed to leave behind uniform, single-crystal cubooctahedra. If the etching was allowed to continue, the single-crystal cubooctahedra were also attacked and partially dissolved. Understanding the role of oxidative etching is critical to the achievement of both uniform shape and size.

Surface modification and characterization of photodefinable epoxy/copper systems

The effects of the wet-chemical and plasma treatments on the adhesion of electroless and sputter-deposited copper to the photodefinable epoxy have been investigated. The wet-chemical treatment increased the amounts of oxygen-containing functionalities on the epoxy surface mainly during the early stage of etching. With the longer etching the pronounced surface roughness was revealed in the form of microcavities. The plasma treatment increased significantly the polar component of surface free energy of the epoxy and produced low surface roughness. The physicochemical changes of the epoxy combined with the experimental adhesion results indicated that in the case of the electroless deposition the mechanical interlocking was the main adhesion mechanism. Sputter-deposited copper exhibited the highest pull strengths on the epoxy when the plasma pretreatment with oxygen was employed. The enhancement of the surface polarity of the epoxy and the enlarged surface contact area due to the increased roughness were the most important factors in the adhesion.

Reactive ion etching of glasses: Composition dependence

Magnetically enhanced reactive ion etching (MERIE) of silicate and phosphate glasses was examined in CF 4/CHF 3 and Ar plasmas. The etch depths were measured by profilometery to obtain etching rates as a function of plasma power, plasma composition and glass composition. It was found that in fluorocarbon plasmas, the etch rate of glasses decreases as the concentration of less-volatile oxides in the glass increases. These etching rates were interpreted in terms of ion-enhanced chemical reaction and physical sputtering. The compositions of the etched surfaces were determined with X-ray photoelectron spectroscopy (XPS). A high chemical reaction rate between the reactive (ion) species in the plasma and the glass surface was observed during the early stages of etching which lead to depletion of highly volatile species (SiF 4 and BF 3) and accumulation of less volatile species (AlF 3, BaF 2, NaF, etc.). At longer times, the glass surface reached a steady state composition (of the less volatile species) and subsequent etching was dominated by physical sputtering.

RIMAPS detection of incipient damage on metallic surfaces

A new imaging technique, rotated image with maximum average power spectrum (RIMAPS), that combines digitized image rotation and Fourier transformation is used not only to obtain the main directions of pattern alignment and the characteristics of surface topography, but also for the detection of incipient damage on metallic surfaces. Different grains of aluminum are studied to show the robustness of this technique that is able to detect different surfaces at the early stages of etching by different reagents. The results are compared with those obtained following standard metallographic procedures that require preparation of properly polished surfaces to obtain good-quality images as the basis for an adequate characterization. RIMAPS turns out to be a quick, simple, and useful tool both to detect incipient damage on metallic surfaces and to identify different surfaces.

Deposition behavior of Si on insulating and conducting substrates in the CVD process: approach by charged cluster model

Deposition behaviors of silicon on dielectric and conducting substrates were studied focussing on the deposition mechanism in the Si–Cl–H system. On the dielectric substrate, silicon particles were deposited after some incubation time and then etched away at a later stage under the same processing conditions. On the conducting substrate, silicon particles were deposited without an incubation time with no observed etching during the experimental time period. In the early stages of etching on the dielectric substrate, the number of silicon particles decreased but the remaining unetched particles became larger, indicating that growth and etching took place simultaneously. This paradoxical phenomenon can be explained on a sound thermodynamic basis if we assume that charged clusters are formed in the gas phase and these clusters are the growth unit. The selective deposition on the conducting material as opposed to the dielectric material can also be explained by the electrostatic interaction between the charged cluster and the conducting or dielectric material.

定電位法による電解コンデンサ用アルミニウム箔のエッチング特性

Pit morphology under potentiostatic conditions was investigated for aluminum with (100) crystal orientation in 1.0mol dm-3 hydrochloric acid solution at 363K.The potential is considered to be an important factor in determining pit morphology. Increases in anodic potential led to an increase in the number of pits and in tunnel length, and to a decrease in pit diameter within 20C·cm-2. The transition of pit sites indicated that many pits were formed at an early stage of etching, and then deepened until a limiting length was reached. New pits did not form but the walls of ordinary pits were dissolved as a second step at a higher anodic charge, corresponding to the point of inflection of current density with time.The phenomenon in which tunnel growth stops abruptly at a limiting length seems to be associated with the increase of Al3+in the tunnel. It is considered that tunnel growth stops because the aluminum chloride at the tunnel tips saturates, causing the pitting potential to become more noble.

定電位電解におけるCu結晶(111)面の転位位置の溶解速度

The (111) surface of copper crystal was etched anodically at constant potentials, 0, 20 and 40 mV vs SHE, in the solution containing 5 kmol·m−3 NaCl, 0.25 kmol·m−3 NaBr and 10−4 kmol·m−3 CuCl, and the dissolution rate at dislocation sites was determined through a measurement of three-dimensional size of the corresponding etch pits from optical and interference microphotographs taken at sucessive times. The width h and the depth d of the etch pits increased rapidly at an early stage of etching and then increased linearly with an increase of etching time t. It was to be added also that the etch pits grew larger when the applied potential was higher. However the side slope d/h of the etch pits decreased with an increase of t and tended to approach asymptotically a constant value. For a given potential, the anodic current density i increased slowly during the stage where the etch pit size, h and d, increased at a constant rate, and finally reached to a constant value. It was shown from the analysis of the above measurements that the i-t relation could be explained on the basis of dissolution processes during dislocation etch pitting.

Energy dependence of etch pit diameter in a CR-39 detector for .ALPHA.-particles with the energy from 1.29 to 5.48 MeV.

The characteristics for alpha-particle recording of CR-39 plastics was studied for practical use. Sample detectors were irradiated with alpha-particles at normal incident angle. The energy was varied from 1.29 to 5.48 MeV. Tracks of alpha-particles could sufficiently be recognized through the etch pit observation with 1 hour etching in 30% solution of NaOH at a temperature of 70 degrees C. The etch pit diameter decreased almost linearly with the energy of alpha-particles at the early stage of etching, which suggested the possibility of the estimation of alpha-particle energy. The energy resolution was evaluated from the FWHM of the measured distribution of etch pit diameters and found to be about 1.8 MeV for 1, 2 and 3 hour etching.

Mechanism of etching and development of etch figures on octahedral faces of diamond

Abstract The etch pattern on natural and cleavage octahedral faces of diamond are studied optically. The etch patterns on the cleavage faces in the early stages of etching have revealed the existence of point defects and linear defects which on furtheretching develop into etch pits of triangular and trapezium shape respectively. It is observed that the linear defects are of different sizes and all of them are crystallographically oriented. A new mechanism of etching is proposed and its implications are fully discussed With the help of this new mechanism the formation of etch figures of various shapes and orientation on octahedral faces have been beautifully illustrated by drawing schematic diagrams. The new mechanism of etching also explains (1) how trigons are converted into hexagons and (2) the displacement of cleavages lines, without visible formation of etch pits during etching.