Etched Roughness Research Articles

The effect of isopropyl alcohol on etching rate and roughness of (1 0 0) Si surface etched in KOH and TMAH solutions

The etching process of (1 0 0) silicon wafers in KOH and TMAH solutions with isopropyl alcohol (IPA) has been studied. The etching rates of different crystallographic planes in the wide range of solutions concentration have been estimated. The mutual relations of the etching rates of these planes have been analysed. Special emphasis was put on the roughness of silicon surface obtained in effect of etching. It was proved that IPA added to the solution improves the morphology of resulted surface. Detailed indications about the solution composition, ensuring satisfactory surface quality have been given. On the basis of experimental results and theoretical considerations, some attempts were made to explain the etching behaviour of silicon in KOH and TMAH solutions with IPA addition. It was suggested that TMA + ions play similar role in the solution to IPA particles and participate in smoothening of the etched surface.

Roughning and smoothing dynamics during KOH silicon etching

We studied the influence of surface preparation prior to KOH etching and of surfactants added to the etchant over the etching rates and roughness of the Si (111) and Si (100) surfaces. The investigated etchants were 25% KOH at 70°C, and 25% KOH with small amounts of anionic, cationic and non-ionic surfactants. The surface preparation refers to the use of the following solutions for the native oxide removal: HF:H 2O 1:10 (followed by DI water rinsing and drying), HF:C 2H 5OH 1:10 (dried without any further rinsing), and 10% HCl in HF:H 2O 1:1 (also dried without rinsing). The evaluations were made by mechanical profilometry and AFM. No difference between the samples dipped in HF–water and HF–alcohol could be observed. The etching rate of the samples dipped in HCl-containing solutions were greater, while their roughness was diminished. We analyzed the influence of surfactants on the roughness and the anisotropy. The etch rates increased when using cationic and anionic surfactants and decreased with non-ionic ones. The anisotropy is modified by surfactants. Tentative explanations for the roughning mechanisms are proposed.

Mathematical Modelling of Roughness-Temperature Evolution

AbstractOrientation -dependent etching of silicon in alkaline solutions is close to get a satisfactory model by considering the random Si-Si bond breaking algorithms (BBA). Here we report our progress regarding the simulation of the atomic-scale roughness of the etched surface, by considering the influence of the processing temperature. We chose the model parameters to fit the experimental data for the etching rate angular dependence for 80°C. We supposed an Arrhenius type dependence on temperature for the basic bond-breaking probabilities and obtained the etching rate and roughness dependence on temperature. The temperature dependence of the etching rates showed the main features of the experimental data: an increase of the etching rate with temperature, a slight change of anisotropy and an increase of the roughness. Further investigations showed we could be close to a roughening transition, which manifests mainly along the directions of the etching rate maxima.

Directly coupled DC-SQUIDs of YBCO step-edge junctions fabricated by a chemical etching process operating at 77 K

High T/sub c/ directly coupled DC-SQUIDs have been successfully fabricated on chemically etched MgO substrate steps. The chemical etching was performed in a mixed acid solution of H/sub 3/PO/sub 4/ and H/sub 2/SO/sub 4/ for the best control of etched surface and roughness. YBCO thin films were deposited epitaxially on the step-edged MgO substrate by a KrF laser ablation method. Characteristics of the directly coupled DC-SQUID have been studied following the patterning and fabrication of the device. The chemically etched steps show sharper edges at the bottom of the step as well as the top unlike those made by ion milling. AFM and Raman Spectroscopy studies on the YBCO thin film deposited and patterned on chemically etched show no sign of appreciable degradation. The result is a good quality junction even at a relatively low step angle. Directly coupled DC-SQUIDs that are fabricated with this process show sweeping voltages of 160 /spl mu/V at 4.2 K, and 6 /spl mu/V at 77 K, respectively.

Reactive ion etching of silica structures for integrated optics applications

Reactive ion etching of silica in a hollow cathode reactor using a CHF3/Ar gas mixture has been studied as a function of masking material, rf power, sample temperature, and O2 and CF4 additions. Etch rates in excess of 0.5 μm/min are typically obtained with a selectivity over amorphous silicon and photoresist of more than 10. The sidewall roughness for etching with an amorphous silicon mask is of the order of 0.05 μm, whereas for a photoresist mask, under similar etching conditions, the sidewall roughness is up to 0.1 μm. For the a-Si mask a further improvement in the sidewall roughness down to 0.02 μm can be obtained by adding O2 to the discharge or elevating the sample temperature, however both parameters cause lateral etching of the a-Si mask and therefore linewidth loss. Nonetheless, when using sample temperature as a control parameter, a process window was found which allows smooth sidewalls to be obtained without dimension loss. In the case of O2 additions such a process window was not found. Possible mechanisms accounting for this difference are discussed. Etching in a CHF3/Ar discharge occurs in competition with simultaneous polymer deposition. The polymer deposition rate was measured in areas shielded from ion bombardment. A phenomenological model describing the effects of polymer deposition on etch rates, sidewall slope, and roughness is proposed. This model assumes that a polymer film with different steady-state thickness can form on different etched structure surfaces, as a result of a balance between polymer etching and deposition. The model is used to explain the tendencies in etch rates, profile slope, and sidewall roughness obtained in this study.

Planarization of diamond thin film surfaces by ion beam etching at grazing incidence angle

Ion beam etching at grazing incidence angle has been used to reduce the surface roughness of polycrystalline diamond thin films, 1 ± 0.2 μm thick, deposited by microwave plasma chemical vapor deposition (MWPCVD). Different reactive etching conditions have been tested for a beam energy of 1 keV with various ion beam and gas atmosphere compositions: pure Ar +, mixture of Ar + + N 2 + and Ar + under a controlled oxygen partial pressure. Their influence on the etching kinetics, roughness and morphology evolutions of the film, crystalline quality have been studied using SEM, AFM and Raman spectroscopy. The optical transmittance has also been measured. The ion beam processes studied result in a drastic reduction of the film surface roughness with a slightly better efficiency for the Ar + + oxygen gas mixture. The roughness decrease leads to an increase in the optical transmittance without any change in the crystalline quality of the film. This planarizing method should be particularly well-adapted for thicker films taking into account the balance between the initial values of thickness and roughness on the one hand, and the material loss on the other. Furthermore, it could be usefully applied to produce large-area membranes.

High-Rate and Smooth Surface Etching of Al 2O 3-TiC Employing Inductively Coupled Plasma (ICP)

High-rate and smooth surface etching of Al2O3-TiC, which is widely used as a slider material for magnetic recording heads, has been developed employing inductively coupled plasma (ICP). The etching rate of 200 nm/min was obtained with Cl2/BCl3 mixture. However the etched morphology exhibited roughness around 40 nm Ra (arithmetic average deviation from center line) because of different etching rates for Al2O3 and TiC grains in the substrate. The addition of Ar to the Cl2/BCl3 improved both the etching rate and roughness of the etched surface considerably. As a result the high etching rate of more than 350 nm/min, which is more than ten times that of conventional Ar+ ion etching, and relatively smooth surface roughness around 20 nm Ra were achieved with Ar/Cl2/BCl3 mixture using 1.2 kW RF power and -500 V V dc.

Plasma and ion beam surface treatment of polyethylene

Plasma treatment is a widely used technique for altering the surface properties of polymers. The present paper deals with the surface modification of polyethylene foils in a capacitively coupled industrial r.f. (13.56 MHz) plasma system. The treated surfaces were investigated by scanning electron microscopy and contact angle measurement. Also etch rates of PE for different plasma parameters were measured. Different sample positions, directly upon the cathode and inside the plasma, distinguished by different ion bombardment due to a d.c. self bias of the cathode, were used for processing. This caused different etch rates, surface structures and roughness. Owing to the creation of polar groups on the surface, the surface tension generally increases with the duration of the plasma treatment. Depending on the sample position, different contributions of polar and dispersion components of the surface tension were found. Even short plasma treatments showed good spatial homogeneity of surface tension. This was independent of the spatial distribution of the plasma density. Ion beam treatment generally showed results similar to those with the plasma treatment, although the effect of the ion energy was more significant for ion beam treatment.

Etch rate and surface roughness of deep narrow U-grooves in (110)-oriented silicon

Long U-shaped grooves that have been anisotropically etched into (110)-oriented silicon with KOH are required for many microsensors and actuators like for microcoolers, force sensors, separating trenches, printheads, etc. Specifications for the etched structures (such as minimum roughness, steep walls or high etch uniformity) require different etch parameters. The etch rates, etch-rate ratios and roughness of the (110) planes are investigated as a function of the KOH temperature and concentration. An important influence on the etch process, especially during the etch of narrow grooves, is also exerted by the (311) planes observed at KOH concentrations above 30%.

Polysilicon Etchback Plasma Process Using HBr , Cl2, and SF 6 Gas Mixtures for Deep‐Trench Isolation

Etchback of polysilicon used for refilling deep trenches isolating bipolar devices has been investigated in a magnetically enhanced reactive ion etcher using , , and gas combinations. Etch rates, uniformities, and loading effects have been studied as a function of gas mixtures. Polysilicon etchback processes with uniformity better than 2%, polysilicon etch rate larger than 5000 Aå/min, and loading factor less than 1.3 were obtained with a gas mixture consisting of less than 9 sccm flow in a predominant and mixture. It was found that the etch roughness and surface profile of the resulting trench polysilicon was a strong function of percentage in the mixture. The controllable trench polysilicon etchback profile with smooth surface and curvature was obtained by using 60 sccm and 50 sccm gas mixtures with 6 sccm gas flow.

Etching roughness for (100) silicon surfaces in aqueous KOH

The quality of vertical roughness produced by the etching of Si in aqueous KOH has been studied by varying several experimental parameters such as molarity, time of etching, temperature, and stirring. We note that at room temperature, unstirred etching is smoother at low and high molarities, and etch rate and roughness both peak near 5–6 M. With no stirring, roughness increases as a function of etch time, then levels off. With stirring, roughness decreases, especially around the peak etch rate near 5–6 M. For a fixed molarity like 5 M, unstirred etching becomes smoother with increasing temperature even as the etch rate increases rapidly. Such results suggest that masking by hydrogen bubbles or silicate etch products is the principle origin of vertical roughness. Bubble properties as a function of molarity and stirring (as determined from electrolysis experiments) are used to suggest a pseudo-masking model to explain some roughness properties.

Plasma Etching of Oxygen Containing Titanium Silicide Films

Anisotropic etching of titanium silicide is essential if its low resistivity gate properties are to be utilized on scaled MOS devices. and plasmas, as well as ion milling, were used to etch composite titanium silicide/polysilicon films, with each displaying definite drawbacks. plasmas yielded rough etching and etch residue, presumably due to the high oxygen content of the silicide film and the relatively high selectivity (low oxide etch rate) of the etch. reactive ion etching and ion milling produced smooth etching but lacked the selectivity to stop on thin underlying gate oxides. A combination of these processes, however, provided successful anisotropic patterning of such structures. A nonselective, smooth etching reactive ion etch was used to etch through the silicide layer, followed by a higher selectivity plasma etch through the underlying polysilicon down to the thin gate oxide.