Etching Of Si Research Articles

Kinetics and coupled dynamics of dewetting and chemical reaction in Si/$$\hbox {SiO}_2$$/Si system

We report on the observation of a coupling between the dewetting of a Si layer on $$\hbox {SiO}_{{2}}$$ induced by surface/interface energy minimization and the etching between both materials due to the $$\hbox {Si}+\hbox {SiO}_{2}\longrightarrow 2$$ $$\hbox {SiO}^\uparrow _g$$ reaction. In the limit of a thin $$\hbox {SiO}_{{2}}$$ layer ( $$\le 10 \,\hbox {nm}$$ ) sandwiched between a Si layer and a Si handle wafer, the front of Si dewetting and the front of $$\hbox {SiO}_{{2}}$$ etching coexist in a narrow region. The interplay between both phenomena gives rise to specific morphologies. We show that extended Si fingers formed by dewetting are stabilized with respect to Rayleigh–Plateau-type instability over tenth of microns thanks to a localized etching of the $$\hbox {SiO}_{{2}}$$ layer. The breakup of this structure occurs abruptly by an unzipping process combining dewetting and etching phenomena. We also put in evidence that Si rings are created with a thin $$\hbox {SiO}_{{2}}$$ layer in the center. These processes are thermally activated with an activation energy of $$2.4\pm 0.5 \,\hbox {eV}$$ and $$4.0\pm 0.5 \,\hbox {eV}$$ , respectively, for dewetting and the etching reaction. All these results highlight the respective roles of wetting and etching in Si/ $$\hbox {SiO}_{{2}}$$ /Si system dynamics and could be a stepping stone for the development of advanced processes based on Silicon-On-Insulator technology.

A Novel Silicon-Air-Silicon Through-Silicon-Via Structure Realized Using Double-Side Partially Overlapping Etching

This letter presents the design and fabrication of a through-silicon-via (TSV) structure using ultra-low-resistivity-silicon (ULRS) as the central conductor and air-gap as the insulation layer. Silicon-air-silicon (SAS) TSVs are successfully fabricated using a simple and low-cost fabrication process based on a novel double-side half-annular Si etching technique. A comparative study on different overlapping areas of the double-side Si etching is carried out to guarantee the proper formation of the air-gap insulation layer and to minimize the lateral undercutting effect occurred near the openings of the air-gaps. Thanks to the good isolation nature of the air and the successful formation of the air-gaps, we have achieved a capacitance density of 0.137 nF/cm2 and a leakage current density of 3.85 nA/cm2 for a single SAS TSV, indicating superior electrical properties in terms of ultra-low parasitic capacitance and excellent insulating performance, which shows an alluring prospect in future 3-D integration strategies and applications.

Chemical carving lithography with scanning catalytic probes

This study introduces a new chemical carving technique as an alternative to existing lithography and etching techniques. Chemical carving incorporates the concept of scanning probe lithography and metal-assisted chemical etching (MaCE). A catalyst-coated probe mechanically scans a Si substrate in a solution, and the Si is chemically etched into the shape of the probes, forming pre-defined 3D patterns. A metal catalyst is used to oxidize the Si, and the silicon oxide formed is etched in the solution; this local MaCE reaction takes place continuously on the Si substrate in the scanning direction of probes. Polymer resist patterning for subsequent etching is not required; instead, scanning probes pattern the oxidation mask directly and chemical etching of Si occurs concurrently. A prototype that drives the probe with an actuator was used to analyze various aspects of the etching profiles based on the scanning speeds and sizes of the probe used. This technique suggests the possibility of forming arbitrary structures because the carving trajectory is formed according to the scan direction of the probes.

Silicon Nanowire Arrays Coated with Ag and Au Dendrites for Surface-Enhanced Raman Scattering

Silicon nanowires (SiNWs) were comprehensively characterized in dependence on conditions of their formation via metal (Ag) -assisted chemical etching (MACE) of monocrystalline Si. The Ag structures remained on/between SiNWs based on both n- and p-Si were found to promote surface enhancement of Raman scattering (SERS) from organic molecules adsorbed on their surface. The Ag structures on/between the SiNWs/p-Si facilitated two times higher SERS-signal from 10-6 M rhodamine 6G than those in the SiNWs/n-Si. The activity of the SERS-substrates based on p-Si was improved by modification with small Au dendrites, which provided rich family of hot spots and prevented degradation of the SERS-activity observed for pure Ag dendrites due to formation of Ag2S during one week of storage in air. The SERS-substrates based on the Au/Ag dendrites on SiNWs/p-Si allowed to achieve nanomolar detection limit of rhodamine 6G and 5,5′-dithiobis (2-nitrobenzoic acid).

Study on plasma characteristics and gas analysis before and after recovery using liquid-fluorocarbon precursor

Perfluorocarbon (PFC) gas is a representative greenhouse gas with high global warming potential (GWP) and is mainly used in the etching processes applicable to the manufacture of semiconductor devices. High capacity and high integration have been achieved in recent years as semiconductor device structures have been replaced by vertical layer structures, and the consumption of PFC gas has exploded due to the increase in high aspect ratio and patterning processes. In this study, the etching and recovery process were performed using C5F8 in L-FC which is in liquid phase at room temperature. This is because the ratio of F and C constituting C4F8, which is a PFC gas used for conventional etching, is similar. In addition, the recovered C5F8 was injected back into the chamber to confirm its reusability, and the electron temperature, plasma density, and ion energy distribution were analyzed. In addition, based on these data, the Si and SiO2 etching process requiring high selectivity was applied using the gas obtained before and after recovery. An analysis of the surface composition of Si and SiO2 after the etching process confirmed the possibility of recovering and reusing the exhaust gas during the process.

Effects of O2 addition on in-plasma photo-assisted etching of Si with chlorine

Addition of oxygen was used to control the in-plasma photo-assisted etching (PAE) of p-type Si(100) and poly-Si in a high density, inductively coupled, Faraday-shielded, Ar/Cl2 (225/25 SCCM), 60 mTorr plasma. After etching, samples were transferred under vacuum to an UHV x-ray photoelectron spectroscopy chamber for surface analysis. Samples etched under PAE conditions (ion energies below the ion-assisted etching, IAE, threshold) had a thicker surface oxide and lower [Cl] surface concentration, when compared to samples etched under IAE conditions (ion energies above the IAE threshold). PAE was found not to be affected by 0.1 or 0.25 SCCM O2 addition, while etching stopped with more than 0.5 SCCM O2 addition. IAE with RF power on the sample stage, resulting in −65 V self-bias, was not affected by up to 2 SCCM of oxygen addition but decreased rapidly when more than 5 SCCM O2 was added to the plasma. These results imply that PAE may be completely suppressed, while IAE occurs unobstructed. The implications of these findings are discussed in view of applications involving continuous wave and pulsed-plasma processes.

Hybrid III-V-on-SOI optical spot size converter by self-aligned selective undercut dry etching of Si.

A technology called self-aligned selective undercut dry etching processing has been demonstrated for fabricating a highly efficient hybrid optical spot size converter (SSC) on a Si-on-insulator (SOI) template. The process was based on a bonded wafer between the upper InP-based multiple quantum well heterostructure and the lower SOI substrate. After defining the mask on the upper InP-based ridge waveguide, CF4/O2 dry reactive ion etching was then used for selective undercut etching of the Si material from the surrounding materials, forming a vertical waveguide coupler of the optical SSC. The lower waveguide, whose dimension is even smaller than the upper one, can thus be vertically self-aligned to the top ridge via an independent processing step. A laterally tapered waveguide ranging from 0.3 to 3 µm in width on the upper InP waveguide was fabricated. The phase-matching condition of the vertical coupler leads to a length of 45 µm and extracts 88% conversion efficiency. The selective undercut etching processing in III-V/SOI material provides a vertical self-alignment scheme for realizing compact and submicron scale heterogeneous integration in a Si photonics template.

Selective chemical wet etching of Si1-xGex versus Si in single-layer and multi-layer with HNO3/HF mixtures

A gate-all-around device, considered as a key structural design for improving performance and density, requires selective etching to obtain nanostructure channels. We investigated the wet etching of epitaxial Si1-xGex films with various HNO3/HF-based chemical etchants to elucidate the mechanism of selective etching of Si1-xGex versus pure Si. Blanket etching was performed on Si1-xGex single-layer and lateral etching was performed on Si/Si1-xGex/Si multi-layer with three different Ge concentrations (x = 0.13, 0.24, and 0.30). In both cases of etching, our results show that the Si1-xGex layer with higher Ge concentration was etched faster. We found that the Si1-xGex etch rate decreased consistently with decreasing HF in both cases, while the slope of the etch rate lowers as the Ge concentration decreases with the blanket etching of Si1-xGex. We postulated that the decrease in the slope of the Si1-xGex etch rate with low Ge concentration occurs due to the difficulty of hole injection into the surface of Si1-xGex, which has a lower valence band offset. In contrast, for the case of lateral etching of Si1-xGex, we found that the slopes of the etch rate are similar to each other irrespective of Ge concentrations. We suggest that the similarity of the slopes is due to the sufficiency of holes, which is supplied not only by HNO3 but also from adjacent Si layers into the Si1-xGex layer. Furthermore, we investigated the effect of structural factors on the lateral etching of Si1-xGex to apply a selective etching process in Si/Si1-xGex/Si multi-layer to obtain Si nanostructures. We found that the lateral etch rate of Si1-xGex in Si/Si1-xGex/Si multi-layers can be reduced owing to the oxide of adjacent Si layers in the etched tunnel, which is not completely removed by HF during the etching process.

Atomic layer etching of metals with anisotropy, specificity, and selectivity

In this work, a special focus is given to atomic layer etching (ALE) of metals, since this is a relatively new field but is expected to grow rapidly given the major advancements potentially enabled via metal incorporation throughout the manufacturing process of integrated circuits. The impact of John Coburn’s work on the development of ALE processes is analyzed with a focus on ion energy and the neutral-to-ion ratio. To realize atomic precision in removing etch-resistant materials with complex compositions or structures, the surface reactivity would replace etch rate as the parameter of interest to control the chemical contrast needed for selectivity. The desirable etching anisotropy dictates the usage of directional ions. John Coburn’s work on ion-enhanced etching of Si serves as an example that a fine control of ion energy and the neutral-to-ion ratio could be the gateway of reactivity control, which is demonstrated with recent progress on thermal-plasma ALE of Ni. The effect of surface reactivity is studied from first-principle atomistic calculations and confirms the experimental findings.

Fabrication of an infrared wire-grid polarizer via anisotropical Si etching in KOH solution

An infrared wire-grid polarizer was fabricated using two-beam interference lithography, anisotropical etching of Si in KOH solution, and thermal evaporation of Al. Consequently, an infrared wire-grid polarizer with a 1-µm-pitch and 195-nm-thick Al grating could be fabricated on the Si grating. The transmittance of transverse magnetic polarization was greater than 48% at 10-µm wavelength, and the extinction ratio was over 22 dB at this wavelength. This polarizer can be fabricated at a much lower cost and using simpler fabrication processes compared to those for conventional infrared polarizers fabricated using dry etching.

High‐Aspect‐Ratio Grating Microfabrication by Platinum‐Assisted Chemical Etching and Gold Electroplating

Diffractive optics play a key role in hard X‐rays imaging for which many scientific, technological, and biomedical applications exist. Herein, high‐aspect‐ratio microfabrication of gratings for X‐ray interferometry is demonstrated using Pt as a catalyst for the metal assisted chemical etching of Si in a solution of HF and H2O2. The Pt layer is thermally treated to realize a porous catalyst layer that stabilizes the etching of a pattern with a pitch size from 4.8 to 20 μm in the direction perpendicular to the <100> Si substrate and an aspect ratio up to 60:1. The superior etching performance of Pt as a catalyst and its stability in a solution with high HF content are reported in direct comparison with the Au catalyst for the same grating parameters. The Si structure is then used as a template for filling with Au, as a high absorbing X‐ray material. The Pt catalyst layer is used as a conductive seed for Au electroplating. The quality of the overall process is assessed by obtaining a visibility map using 30 μm‐thick Au grating in an X‐ray interferometric setup at 20 keV.

Plasma Parameters and Silicon Etching Kinetics in C4F8 + O2 + Ar Gas Mixture: Effect of Component Mixing Ratios

In this work, we investigated the possibidlxlity to control both gas-phase chemistry and silicon etching kinetics in C4F8 + O2 + Ar inductively coupled plasma by changes in O2/Ar, C4F8/O2 and C4F8/Ar mixing ratios at the constant fraction of the rest component (50%), gas pressure (10 mTorr), input power (700 W) and bias power (200 W). The combination of plasma diagnostics and modeling tools allowed one: (a) to compare the effects of gas mixing ratios on both steady-state plasma parameters and densities of active species; (b) to figure out key processes which determine the fluorine atom formation/decay balance in each gas system; and (c) to analyze the differences in Si etching kinetics in terms of process-condition-dependent effective reaction probability. It was shown that the maximum changes in gas-phase chemistry take place in O2-rich plasmas due to CFx + O/O(1D) → CFx−1O + F, CFxO + e → CFx−1O + F + e and CFO + O/O(1D) → CO2 + F stepwise dissociation pathways. It was suggested also that the effective probability for Si + xF → SiFx reaction may be controlled by either fluorocarbon film thickness (in C4F8—rich plasmas) or O atom flux (in Ar and O2—rich plasmas) through the balance of adsorption sites on the etched surface.

Numerical investigation of the effect of variation of gas mixture ratio on density distribution of etchant species (Br, Br+, Cl, Cl+, and H) in HBr/Cl2/Ar plasma discharge

A self-sustained fluid model is used to study the effect of variation of noble gas fraction (Ar) and variation of gas mixture ratio (HBr/Cl2/Ar) on density distribution of important etchant species (Br, Br+, Cl, Cl+, and H) in HBr/Cl2/Ar capacitive coupled plasma discharge that is being vastly used for dry etching of Si, GaAs, GaSb and other group III and IV semiconductor materials. A comprehensive set of 80 reactions in this plasma discharge is presented which contains electron impact reactions, neutral–neutral reactions, ion–ion reactions, and charge transfer reactions. Based on simulation results, it is found that densities of neutral species have normal distribution curve; density is higher at center of the reactor and decreases as we move towards electrode surface, while densities of charged species follow bimodal distribution in which peaks occur near electrodes. Furthermore, the addition of Ar in HBr/Cl2 causes electron density to increase which promotes ionization and dissociation. It was found that at constant supply of Cl2 gas, by increasing Ar fraction (HBr/Cl2/Ar from 80/10/10 to 10/10/80) densities of Br, Br+ and H will go down and at constant supply of Ar gas, raising Cl2 fraction in feedback gases (HBr/Cl2/Ar from 70/20/10 to 20/70/10) promoted the production of Cl and Cl+ while densities of Br, Br+, and H are dropped-off. Hence, densities and fluxes of important etchant species – for chemical vs. physical etching – can be controlled by tuning of mixture ratio.

Novel fabrication of fixed suspended silicon nitride structure for MEMS devices with dry etching

A method of fabricating suspended LPCVD and PECVD silicon nitride structure is demonstrated for a wide range of MEMS (Micro-Electro-Mechanical Systems) applications. Low stress LPCVD and PECVD silicon nitride film of 1 μm thickness were selected for the structure separately. Optical Lithographic parameters, viz, photoresist (PR) thickness, PR variety and baking parameters were optimized to obtain the PR suitable for selective etching of silicon and silicon nitride. Parameters of the dry etching process were also optimized to achieve anisotropic etching of silicon nitride and isotropic etching of Si to release the silicon nitride beam. The silicon nitride structures, thus released, were characterized using Scanning Electron Microscope (SEM) and Laser Doppler Vibrometer (LDV). Finite Element Method (FEM) analysis was carried out using COMSOL, to compare with the experimental modes of vibration investigated using the Laser Doppler Vibrometer (LDV). Thus we demonstrate that the first mode at 30 kHz was indeed the optimum match.

Tilted black-Si: ∼0.45 form-birefringence from sub-wavelength needles.

The self-organised conical needles produced by plasma etching of silicon (Si), known as black silicon (b-Si), create a form-birefringent surface texture when etching of Si orientated at angles of θi < 50 - 70° (angle between the Si surface and vertical plasma E-field). The height of the needles in the form-birefringent region following 15 min etching was d ∼ 200 nm and had a 100 μm width of the optical retardance/birefringence, characterised using polariscopy. The height of the b-Si needles corresponds closely to the skin-depth of Si ∼λ/4 for the visible spectral range. Reflection-type polariscope with a voltage-controlled liquid-crystal retarder is proposed to directly measure the retardance Δn × d/λ ≈ 0.15 of the region with tilted b-Si needles. The quantified form birefringence of Δn = -0.45 over λ = 400 - 700 nm spectral window was obtained. Such high values of Δn at visible wavelengths can only be observed in the most birefringence calcite or barium borate as well as in liquid crystals. The replication of b-Si into Ni-shim with high fidelity was also demonstrated and can be used for imprinting of the b-Si nanopattern into other materials.

Concerning the Effect of Type of Fluorocarbon Gas on the Output Characteristics of the Reactive-Ion Etching Process

The comparative research of the parameters, steady-state composition, and the effects of heterogeneous interaction in the plasma of fluorocarbon gases CxHyFz with various z/x relations in conditions of an induction RF (13.56 MHz) discharge is carried out. The binary systems CxHyFz + Ar based on CF4 (z/x = 4), CHF3 (z/x = 3), and C4F8 (z/x = 2) are used as the subjects of research. Through the methods of diagnostics and simulation of plasma we found (a) the reasons of the differences in the physical parameters (temperature and density of electrons, energy of ion bombardment) of the plasma in the studied systems; (b) the special characteristics of the kinetics of the plasma-chemical processes determining the steady state concentrations of fluorine atoms and polymer-forming radicals; and (c) the special characteristics of the kinetics of the heterogeneous process forming the output parameters (rate, selectivity, anisotropy) of the reactive ion etching of Si and SiO2.

On the Control of Plasma Chemistry and Silicon Etching Kinetics in Ternary HBr + Cl2 + O2 Gas System: Effects of HBr/O2 and Cl2/O2 Mixing Ratios

The influences of both HBr/O2 (at constant Cl2 fraction) and Cl2/O2 (at constant HBr fraction) ratios in HBr + Cl 2 + O2 gas mixture on bulk plasma characteristics, active species densities and etching kinetics of silicon were studied. The results indicated that an increase in O2 content in a feed gas at constant Cl2 fraction in a processing gas (1) produces the stronger impact on plasma chemistry by the influence on the kinetics of electron-impact and atom-molecular reaction; and (2) provides the wider adjustments for both halogen atom flux and ion flux with the opposite tendencies with those for variable Cl2/O2 mixing ratio. The experiments demonstrated that the transition toward more oxygenated plasmas in both cases lowers the Si etching rate as well as result is decreasing effective reaction probability and etching yield. These effects may be associated with decreasing amount of adsorption sites for Cl/Br atoms as well as increasing sputtering (ion-stimulated desorption) threshold for reaction products due to the formation of the low-volatile silicon oxy-chlorides and-bromides in heterogeneous SiClx + O/OH and SiBrx + O/OH reactions.

Etching of Si3N4 induced by electron beam plasma from hollow cathode plasma in a downstream reactive environment

An etching system based on the interaction of electrons extracted from a direct current hollow cathode (HC) Ar plasma and injected toward an Si3N4 covered silicon substrate located in the downstream reactive environment created by an additional remote CF4/O2 plasma source was developed and evaluated. By controlling the properties of the injected beam electrons, this approach allows to deliver energy to a surface functionalized by exposure to reactive species and initiate surface etching. The energy of the primary beam electrons is controlled by the acceleration voltage relative to the HC discharge. Ar atoms flow from the high-pressure HC discharge into the low pressure downstream reactive environment in the process chamber. For an acceleration voltage greater than the ionization potential of Ar and/or process gas species, the energetic primary beam electrons produce a secondary plasma in the process chamber and can also cause additional dissociation. The authors have characterized the properties of the secondary plasma and also surface etching of Si3N4 as a function of process parameters, including acceleration voltage (0–80 V), discharge current of the HC discharge (1–2 A), pressure (3.5–20 mTorr), source to substrate distance (1.5–5 cm), and feed gas composition (20% and 80% O2 in CF4/O2). The electron energy probability function measured with a Langmuir probe about 2.5 cm below the extraction ring suggests several major groups of electrons for this situation, including high energy primary beam electrons with an energy that varies as the acceleration voltage is changed and low-energy electrons produced by beam electron-induced ionization of the Ar gas in the process chamber. When a remote CF4/O2 plasma is additionally coupled to the process chamber, Si3N4 surfaces can be functionalized, and by varying the energy of the beam electrons, Si3N4 etching can be induced by electron-neutral synergy effect with plasma-surface interaction. For conditions without beam electron injection, the remote plasma etching rate of Si3N4 depends strongly on the O2 concentration in the CF4/O2 processing gas mixture and can be suppressed for O2-rich process conditions by the formation of an SiONF passivation layer on the Si3N4 surface. The combination of the HC electron beam (HCEB) source with the remote plasma source makes it possible to induce Si3N4 etching for O2-rich remote plasma conditions where remote plasma by itself produces negligible Si3N4 etching. The electron enhanced etching of Si3N4 depends strongly on the O2/CF4 mixing ratio reflecting changing arrival rates of O and F species at the surface. Optical emission spectroscopy was used to estimate the ratio of gas phase F and O densities and found to be controlled by the gas mixing ratio and independent of HCEB operating conditions. At this time, the detailed sequence of events operative in the etching mechanism is unclear. While the increase of the electron energy is ultimately responsible for initiating surface etching, presently, the authors cannot rule out a role of ions from the simultaneously produced secondary plasma in plasma-surface interaction mechanisms.

Field emission from nanotubes and flakes of transition metal dichalcogenides

Transition metal dichalcogenides such as MoS2 and WS2 are low-dimensional semiconductor materials. MoS2 and WS2 nanotubes and flakes were grown by a chemical transport reaction under a temperature gradient. I2 was used as a transport agent for previously synthesized MoS2 and WS2, respectively. These multilayered nanotubes are indirect bandgap semiconductors with a bandgap depending on their diameter. WS2 flakes were prepared by the sulfurization of thin WOx flakes. To increase the field enhancement of such low-dimensional structures by a higher aspect ratio, two approaches were examined: (a) the MoS2 and WS2 nanotubes were attached individually by a focused ion beam with Pt on dry etched n-type Si pillars and (b) the WS2 flakes were grown directly on the surface of the (n-type and p-type) Si pillars. Integral field emission measurements were performed in a diode configuration with a 50 μm mica spacer in a vacuum chamber at pressures of about 10−9 mbar. At a voltage of 900 V (18 MV/m), the integral emission current from the nanotubes is up to 11 μA for the lateral mounted MoS2 and about 1.3 μA (1.0 μA) for the upright mounted WS2 (MoS2). The onset voltage for a current of 1 nA is about 550 V for MoS2 and 500 V for WS2, respectively. The voltage conversion factor is in the range of 6 × 104–8 × 104 cm−1 for the nanotubes. The mounted MoS2 flakes show a field emission current of about 6 μA at 18 MV/m in contrast to the directly grown WS2 flakes, which show a pronounced saturation regime and, therefore, a lower emission current of about 0.5 μA is reached at 1500 V (25 MV/m). The WS2 flakes show a two times higher (1 × 105 cm−1) voltage conversion factor in comparison to the MoS2 flakes (5 × 104 cm−1). The extracted characteristics of the current-limiting part show a difference in the behavior of the extracted current-limiting characteristics between the lateral (linear) and upright mounted (exponential) nanotubes and the MoS2 flakes. In contrast, the WS2 flakes show charge carrier depletion effects.

Lamellar Orientation of a Block Copolymer via an Electron-Beam Induced Polarity Switch in a Nitrophenyl Self-Assembled Monolayer or Si Etching Treatments

Directed self-assembly (DSA) was investigated on self-assembled monolayers (SAMs) chemically modified by electron beam (EB) irradiation, which is composed of 6-(4-nitrophenoxy) hexane-1-thiol (NPHT). Irradiating a NPHT by EB could successfully induce the orientation and selective patterning of block copolymer domains. We clarified that spatially-selective lamellar orientations of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) could be achieved by a change of an underlying SAM. The change of an underlying SAM is composed of the transition of an NO2 group to an NH2 group, which is induced by EB. The modification in the polarity of different regions of the SAM with EB lithography controlled the lamellar orientation of PS-b-PMMA. The reduction of the NPHT SAM plays an important role in the orientation of block copolymer. This method might significantly simplify block copolymer DSA processes when it is compared to the conventional DSA process. By investigating the lamellae orientation with EB, it is clarified that only suitable annealing temperatures and irradiation doses lead to the vertical orientation. We also fabricated pre-patterned Si substrates by EB lithographic patterning and reactive ion etching (RIE). DSA onto such pre-patterned Si substrates was proven to be successful for subdivision of the lithographic patterns into line and space patterns.