Showing papers in "Journal of Vacuum Science & Technology B in 1996"
TL;DR: In this paper, a process for reproducibly and reliably realizing thin-layer patterning having details with dimensions of 100 nm or even less is described, which is called mold lithography, and the strengths of this process are its simplicity and low cost while maintaining compatibility with (standard) semiconductor technology processing.
Abstract: A process for reproducibly and reliably realizing thin‐layer patterning having details with dimensions of 100 nm or even less is described. This process has been called mold lithography. It is a two‐step process: First, a photopolymerization‐replication step is carried out, after which pattern transfer is realized through, e.g., wet or dry etching into the substrate material. We performed a number of elementary experiments to evaluate this process. Processing conditions are given and the obtained results are discussed. The strengths of this process are its simplicity and low cost while maintaining compatibility with (standard) semiconductor‐technology processing.
740 citations
TL;DR: In this paper, the fabrication of gated diamond field-emission cathodes is described and a theory of their operation is discussed, and the cathodes are made using commercial diamond grit with the addition of Ni and Cs salts to enhance emission.
Abstract: The fabrication of gated diamond field‐emission cathodes is described and a theory of their operation is discussed. These cathodes are made using commercial diamond grit with the addition of Ni and Cs salts to enhance emission. The resulting structure resembles a field‐emission Spindt cathode with the internal metal cone replaced by a ∼100 nm layer of diamond grit. Emission from these cathodes occurs at the lowest reported gate voltage of any field emission device and is unaffected by operation at pressures of over 100 Pa of N2. Operation in oxygen and H2S at pressures of 6×10−4 Pa degrades emission, but the cathodes recover once the ambient pressure is reduced to below 1×10−4 Pa. The emission current noise is 2.5% rms over an 8 h period and 1% rms over 3 ms. These cathodes suffer from high gate current that varies from 0.2 to 1000 times the emitted current. The high gate current is known to be process dependent and not inherent to the cathodes. The emission performance is explained by the stable negative electron affinity of diamond, which allows for injection of electrons from diamond into vacuum with little to no electric field, 0–1 V μm−1. Cathode operation is limited by the injection of electrons into the diamond at the back metal–diamond interface, which depends upon the doping of the diamond and the roughness of that interface.
294 citations
TL;DR: In this article, Johnson et al. studied the variation of frictional force with externally applied load for a Pt-coated atomic force microscope tip in contact with the surface of mica cleaved in ultrahigh vacuum.
Abstract: We have studied the variation of frictional force with externally applied load for a Pt‐coated atomic force microscope tip in contact with the surface of mica cleaved in ultrahigh vacuum. At low loads, the frictional force varies with load in almost exact proportion to the area of contact as predicted by the Johnson–Kendall–Roberts (JKR) theory [K. L. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Soc. London Ser. A 324, 301 (1971)] of elastic adhesive contacts. The friction‐load relation for a deliberately modified tip shape was proportional to an extended JKR model that predicts the area‐load relation for nonparabolic tips. The tip shape was determined experimentally with a tip imaging technique and was consistent with the predicted friction behavior. This demonstrates that the frictional force is proportional to the area of contact between the tip and sample. Using the JKR/extended JKR model, interfacial surface energies and shear strengths can be estimated.
285 citations
TL;DR: In this paper, the thermal stability of thin films of Group III nitrides prepared by low-pressure chemical vapor deposition from organometallic precursors was investigated by elastic recoil detection analysis (ERDA).
Abstract: We present results on the thermal stability as well as the thermally induced hydrogen, hydrocarbon, and nitrogen–hydrogen effusion from thin films of Group III nitrides prepared by low‐pressure chemical vapor deposition from organometallic precursors. We have deposited amorphous, polycrystalline, and epitaxial InN, GaN, and AIN films on (0001) Al2O3 substrates using the chemical reaction of azido[bis(3‐dimethylamino)propyl]indium, triethylgallium, and tritertiarybutylaluminium with ammonia. The substrate temperature was varied between 400 °C and 1100 °C. The elemental composition, in particular its dependence on the growth temperature, was investigated by elastic recoil detection analysis (ERDA). The influence of growth rate and crystallite size on the concentration of surface adsorbed hydrocarbons and carbon oxides is determined by a combination of ERDA and thermal desorption measurements. In addition, the stability of and the nitrogen flux from the InN, GaN, and AIN surfaces was determined by x‐ray diffraction and thermal decomposition experiments.
276 citations
TL;DR: In this article, an experimental system and methodology were developed to realize dry etching of single crystal silicon with monolayer accuracy, which was self-limiting with respect to both reactant and ion dose.
Abstract: An experimental system and methodology were developed to realize dry etching of single crystal silicon with monolayer accuracy. Atomic layer etching of silicon is a cyclic process composed of four consecutive steps: reactant adsorption, excess reactant evacuation, ion irradiation, and product evacuation. When successful, completion of one cycle results in removal of one monolayer of silicon. The process was self‐limiting with respect to both reactant and ion dose. Control of the ion energy was the most important factor in realizing etching of one monolayer per cycle.
274 citations
TL;DR: In this article, the diffusion barrier properties in between Cu and Si were investigated by using sheet resistance measurement, x-ray diffraction, Auger electron spectroscopy, and Secco etching.
Abstract: Tantalum (Ta) and tantalum nitride films (Ta2N and TaN) of about 50 nm thickness were reactively sputter deposited onto (100) Si substrate by using dc magnetron sputtering and their diffusion barrier properties in between Cu and Si were investigated by using sheet resistance measurement, x‐ray diffraction, Auger electron spectroscopy, and Secco etching. With increasing amounts of nitrogen in the sputtering gas, the phases in the as‐deposited film have been identified as a mixture of β‐Ta and bcc‐Ta, bcc‐Ta, amorphous Ta2N, and crystalline fcc‐TaN. Diffusion barrier tests indicate that there are two competing mechanisms for the barrier failure; one is the migration of Cu into the Si substrate and another is the interfacial reaction between the barrier layer and the Si substrate. For instance, we identified that elemental Ta barrier failure occurs initially by the diffusion of Cu into the Si substrate through the barrier layer at 500 °C. On the other hand, the Ta2N barrier fails at 700 °C by the interfacial reaction between Ta2N and Si substrate instead of the migration of Cu into the Si substrate. For the case of TaN, the barrier failure occurs by the migration of Cu into the Si substrate at 750 °C. It is also demonstrated that the diffusion barrier property is enhanced as the nitrogen concentration in the film is increased.
247 citations
TL;DR: In this article, a piezoresponse technique based on scanning force microscopy (SFM) has been used for studying domain structure in ferroelectric thin films and the effect of the film structure on the imaging resolution of domains is discussed.
Abstract: A piezoresponse technique based on scanning force microscopy (SFM) has been used for studying domain structure in ferroelectric thin films. Studies were performed on Pb(Zrx,Ti1−x)O3(PZT) thin films produced by a sol–gel method. The piezoresponse images of the PZT films were taken before and after inducing polarization in the films by applying a direct current voltage between the bottom electrode and the SFM tip. Polarization induced patterns were written with 20 V pulses and subsequently imaged by the SFM piezoresponse technique. The effect of the film structure on the imaging resolution of domains is discussed.
213 citations
TL;DR: Achromatic interferometric lithography is the preferred approach for producing large area, spatially coherent 100 nm period gratings and grids as discussed by the authors, which has enabled exposure areas of ≊10 cm2.
Abstract: Achromatic interferometric lithography is the preferred approach for producing large‐area, spatially coherent 100 nm period gratings and grids. We report on improvements to processes which have enabled exposure areas of ≊10 cm2. In addition, we report on the fabrication of 100 nm period free‐standing gold gratings.
193 citations
TL;DR: The force amplified biological sensor will take advantage of the high sensitivity of force microscope cantilevers to detect the presence of as little as one superparamagnetic particle bound to a cantilever by a sandwich immunoassay technique.
Abstract: We are developing a sensor capable of detecting biological species such as cells, proteins, toxins, and DNA at concentrations as low as 10−18 M. The force amplified biological sensor will take advantage of the high sensitivity of force microscope cantilevers to detect the presence of as little as one superparamagnetic particle bound to a cantilever by a sandwich immunoassay technique. The device, which will ultimately be small enough for hand‐held use, will perform an assay in about 10 min. Lock‐in detection and use of a reference cantilever will provide a high degree of vibration immunity. An array of ten or more cantilevers will provide greater sensitivity and the capability to detect multiple species simultaneously. The force amplified biological sensor also offers the potential of distinguishing and studying chemical species via its ability to measure binding forces.
186 citations
TL;DR: In this paper, several oxide-GaAs heterostructures were fabricated using in situ multiple-chamber molecular beam epitaxy, and the oxides include SiO2, MgO, and Ga2O3, all evaporated by an electron beam method.
Abstract: Several oxide‐GaAs heterostructures were fabricated using in situ multiple‐chamber molecular beam epitaxy. The oxides include SiO2, MgO, and Ga2O3(Gd2O3), all evaporated by an electron beam method. The SiO2 and Ga2O3(Gd2O3) films are amorphous while the MgO films are crystalline and part of the films are epitaxially grown on GaAs(100). Among these heterostructures, the Ga2O3(Gd2O3)–GaAs shows a photoluminescence intensity comparable to that of Al0.45Ga0.55As–GaAs, and forms accumulation and inversion layers as measured from capacitance voltage measurement in quasistatic and high frequency modes.
165 citations
TL;DR: In this paper, a Monte Carlo sheath simulator, a Poisson equation solver, and an ion/electron trajectory simulator were used to study surface charging and ion trajectory distortion during submicron patterning in high density plasma etching.
Abstract: Numerical simulation was used to study both surface charging and ion trajectory distortion during submicron patterning in high density plasma etching. The plasma was assumed uniform and the cause for the surface charging was the directionality difference between ions and electrons. The role of ion transit time effects on the ion energy distribution function was also considered, while the effect of discharging currents such as through insulators was not included. Using a Monte Carlo sheath simulator, a Poisson equation solver, and an ion/electron trajectory simulator, the steady state potential distribution and ion trajectories were calculated for various line‐and‐space structures and plasma conditions where notching, which is a local sidewall etching, has been observed after the overetching part of polysilicon etching processes. The results show significant positive charging at the bottom of high aspect ratio spaces which depends on the ion energy distribution function. Notching at the bottom of an outermost polysilicon line before a wide space is the result of ion deflection toward the line which has the lower potential from receiving more electrons from a side facing the wide space. The simulator was validated using previously reported electron cyclotron resonance etcher notching results. It was found that the calculated potential difference between the bottom of a space and the adjacent line shows the same qualitative dependence on the wide space width as experimental notch depth results show. In addition, these potential differences are large enough to substantially increase the ion flux at regions where notching occurs for the ion energy distribution function for the plasma conditions used. Thus this shows aspect ratio dependent charging effects which are not dependent on initial plasma nonuniformity.
TL;DR: In this article, the procedure for three-dimensional additive lithography with electron-beam induced deposition is applied in a scanning electron microscope equipped with an image processor beam control system for lithography.
Abstract: The procedure for three‐dimensional additive lithography with electron‐beam induced deposition is applied in a scanning electron microscope equipped with an image processor beam control system for lithography. Employing organometallic materials, which contain gold or platinum, quantum dots, resistors, and field emitter tips are deposited. Changing the current, the properties of the deposited nanocrystalline compound materials can be selected to be insulating or conducting. High resolution and high aspect ratio structures are grown with this technique. To find the mechanism responsible for conductivity in the deposited material, resistors are characterized at temperatures ranging from −150 °C to +180 °C. Measurements are performed in a high‐vacuum chamber equipped with a gas cooling system cooled with liquid nitrogen and a resistive heater. Poole–Frenkel plots show that field electron emission and hopping of electrons is the dominant mechanism of conduction. The metal content of the deposits is increased w...
TL;DR: In this paper, the authors review the status of the microcolumn program and discuss opportunities and challenges of this approach to high-throughput nanolithography and related applications, and special emphasis is given to lithography in the 100 nm regime.
Abstract: Lithography with an array of miniaturized scanning electron‐beam columns presents one of the most promising high‐throughput possibilities for fabrication of devices with feature sizes less than 100 nm. With scanning electron beams no mask is required and the necessary resolution and alignment of overlay structures are realizable. With arrays of microcolumns, the lithography throughput of a single column can be multiplied. The approach can also be used for a number of lithography related applications such as metrology, inspection, testing, etc. We review the status of the microcolumn program and discuss opportunities and challenges of this approach to high‐throughput nanolithography and related applications. Special emphasis is given to lithography in the 100 nm regime.
TL;DR: By adapting a scanning force microscope to operate at frequencies above the highest tip-sample resonance, the sensitivity of the microscope to materials' properties is greatly enhanced as mentioned in this paper, and the cantilever's behavior in response to high-frequency excitation from a transducer underneath the sample is fundamentally different than to its low-frequency response.
Abstract: By adapting a scanning force microscope to operate at frequencies above the highest tip–sample resonance, the sensitivity of the microscope to materials’ properties is greatly enhanced The cantilever’s behavior in response to high‐frequency excitation from a transducer underneath the sample is fundamentally different than to its low‐frequency response In this article, the motivations, instrumentation, theory, and first results for this technique are described
TL;DR: In this article, a platinum/10% rhodium resistance thermal probe is used to image variations in thermal conductivity or diffusivity at micron resolution and to perform localized calorimetry.
Abstract: We have used a platinum/10% rhodium resistance thermal probe to image variations in thermal conductivity or diffusivity at micron resolution and to perform localized calorimetry. The probe is used as an active device that acts both as a highly localized heat source and detector; by generating and detecting evanescent temperature waves, we may control the maximum depth of sample that is imaged. Earlier work has shown that subsurface images of metal particles buried in a polymer matrix are consistent with computer simulations of heat flows and temperature profiles, predicting that a 1 μm radius probe in air will give a lateral resolution of ∼200 nm near the surface, with a depth detection of a few μm. We have a special interest in polymer blends, and we present zero‐frequency mode and temperature‐modulation mode thermal images of some immiscible blends in which the image contrast arises from differences in thermal conductivity/diffusivity between single polymer domains. The behavior of domains is observed in real time as the blends are subjected to a slow temperature rise. We have also achieved localized differential thermal analysis of a number of polymers, and recorded events such as glass transitions, meltings, recrystallizations, and thermal decomposition within volumes of material estimated at a few μm3. This opens the way forward towards calorimetric imaging, by which it should be possible to distinguish between different regions undergoing either reversible or irreversible changes as the temperature is varied.
TL;DR: In this paper, the authors investigated the limitations on the formation of focused ion beam images from secondary electrons and found that for small features, sputtering is the limit to imaging resolution, and for extended small features (e.g., layered structures), rearrangement, redeposition, and differential sputtering rates may limit the resolution in some cases.
Abstract: This article investigates the limitations on the formation of focused ion beam images from secondary electrons. We use the notion of the information content of an image to account for the effects of resolution, contrast, and signal‐to‐noise ratio and show that there is a competition between the rate at which small features are sputtered away by the primary beam and the rate of collection of secondary electrons. We find that for small features, sputtering is the limit to imaging resolution, and that for extended small features (e.g., layered structures), rearrangement, redeposition, and differential sputtering rates may limit the resolution in some cases.
TL;DR: In this paper, a computational procedure for the estimation of the geometry of the scanning probe from the topographic image data alone is presented, and the properties of the tip function extracted from such data permit an assessment of the sample-related information content of an image.
Abstract: Scanning probe microscopy has proven to be an invaluable tool for the investigation of surface topography; however, the finite geometry of the imaging tip can often distort image data and complicate metrological investigations of surface features. Here, the derivation of a computational procedure for the estimation of the geometry of the scanning probe from the topographic image data alone is presented. The properties of the tip function extracted from such data permit an assessment of the sample‐related information content of an image. The technique is demonstrated by its application to simulated scanning probe microscopy image data, where its performance can be assessed, and by its application to experimental image data obtained from the scanning force microscope.
TL;DR: In this article, the first successful operation of a scanning force microscope using microfabricated capacitive force sensors was reported, which consisted of a cantilever spring with integrated tip at the free end and an electrically insulated counter electrode.
Abstract: We report on the first successful operation of a scanning force microscope using microfabricated capacitive force sensors. The sensors, which are made from single crystal silicon on insulator wafers, consist of a cantilever spring with integrated tip at the free end and an electrically insulated counter electrode. Dynamic force gradient sensing is the preferred operating mode. Here, tip–sample interactions are detected by letting the sensor act as a resonator in a phase controlled oscillator setup and measuring corresponding shifts of the oscillation frequency. Experiments were performed in vacuum using a standard tunneling microscope. A Cr grating on a quartz substrate served as the test sample. Topographic images showing details on a 10 nm scale were obtained operating at a constant force gradient of the order of 0.01 N/m. In addition, critical design parameters are discussed based on an analysis of the electromechanical properties of the sensors.
TL;DR: The properties of Ta2N and TaN compound films as a diffusion barrier between Cu and Si have been investigated by examining compositional depth profiles obtained by Auger electron spectroscopy as discussed by the authors.
Abstract: The properties of Ta2N and TaN compound films as a diffusion barrier between Cu and Si have been investigated by examining compositional depth profiles obtained by Auger electron spectroscopy The use of a Ta2N barrier is effective for improving the thermal stability of the contact system by raising the silicide formation temperature as compared with the use of a Ta barrier The contact system of Cu/TaN/Si is fairly stable due to annealing for 1 h even at 750 °C This is interpreted by the stability of the TaN compound, which is chemically inert to Si as well as Cu at this temperature Eliminating the grain growth of TaN due to annealing is also effective for suppressing the physical diffusion through the barrier
TL;DR: In this article, the authors used Rheological models to represent different scanning probe microscope configurations and found that modulating the sample at high frequencies results in the best microscope behavior for measuring the stiffness of rigid materials, and detecting the motion of the tip itself (not its position relative to the tip holder) should be best for studying compliant materials.
Abstract: Rheological models are used to represent different scanning probe microscope configurations. The solutions for their static and dynamic behavior are found and used to analyze which scanning probe microscope configuration is best for a given application. We find that modulating the sample at high frequencies results in the best microscope behavior for measuring the stiffness of rigid materials, and that by modulating the tip at low frequencies and detecting the motion of the tip itself (not its position relative to the tip holder) should be best for studying compliant materials in liquids.
TL;DR: In this article, thin films of TiO2 have been deposited on silicon wafers from titanium tetrakis-isopropoxide (TTIP) and TTIP/H2O using low pressure metalorganic chemical vapor deposition.
Abstract: Thin films of TiO2 have been deposited on silicon wafers from titanium tetrakis‐isopropoxide (TTIP) and TTIP/H2O using low pressure metalorganic chemical vapor deposition. The films have been characterized by Rutherford backscattering spectrometry, forward recoil spectrometry, x‐ray diffraction, and electrical techniques. Dielectric constants of approximately 30 were measured by high frequency C–V. Metal–oxide–semiconductor capacitors were fabricated using sputtered platinum as the upper electrode material. Films deposited in the presence of water vapor had a much lower quality interface with the silicon substrate. Normal thermionic emission was observed when the gate electrode was positively biased and barrier heights were extracted. Dramatically reduced leakage currents and increased barrier heights were seen after 750 °C anneals in dry oxygen. Using a ramped voltage test, capacitors were found to break down at applied fields of 3.0 MV/cm.
TL;DR: In this article, the authors show that the electric field required to induce electron emission from diamond can be significantly reduced when the samples are properly grown or postgrowth processed so that they contain a substantial amount of structural defects.
Abstract: Diamond films and islands have been synthesized with varying defect densities and dopant levels by chemical vapor deposition for field emission display applications. Vacuum field emission measurements show that the electric field required to induce electron emission from diamond can be significantly reduced when the samples are properly grown or postgrowth processed so that they contain a substantial amount of structural defects. The defective diamond is characterized by a broadened peak at 1332 cm−1 in Raman spectroscopy with a full width at half‐maximum in the range of 7–11 cm−1. These materials require a turn‐on field (for a current density of 0.01 mA/cm2) as low as 15 V/μm, and a threshold field (for a current density of 10 mA/cm2) as low as 30 V/μm for electron emission. These field values are almost an order of magnitude lower than those required for high quality, p‐type semiconducting diamond. Detailed numerical analysis of the emission current‐voltage data from multiple diamond tips with varying g...
TL;DR: In this paper, it has been proposed that the shape of the tip can be reconstructed from images of a known shape characterizer, which is known to have a small tip size.
Abstract: In scanned probe microscopy the image is a combination of information from the sample and the tip. In order to reconstruct the true surface geometry, it is necessary to know the actual tip shape. It has been proposed that this shape may be reconstructed from images of ‘‘tip characterizer’’ artifacts of independently known shape. The requirements for this strategy—dimensional uncertainty and instability of the characterizer small compared to the tip size—are not trivial. An alternative is ‘‘blind reconstruction,’’ which requires no information about the characterizer geometry apart from that contained within its image, yet produces an outer bound on the tip shape which for appropriately chosen characterizers is a good approximation. With blind reconstruction dimensional instability of characterizers is less problematical, and characterizer measurability is no longer a constraint, so more complex distributed characterizer geometries may be advantageously employed. In situations where part of a characterizer has a known shape, blind reconstruction and the known‐characterizer method may be combined.
TL;DR: In this article, the authors used the two-dimensional histogram technique to determine the loading dependence of friction on terrace and step sites of NaCl(001) and an extended adhesion model was used to analyze the data.
Abstract: The two‐dimensional histogram technique is used to determine the loading dependence of friction on terrace and step sites of NaCl(001). An extended adhesion model is used to analyze the data. Both Hertz and JKR theory are incorporated for the elastic deformation. Depending on the model, shear strengths of 100–190 MPa are found at the terrace region. Increased shear strength values of 500–1800 MPa are found at the step edges that are interpreted in terms of the increased energy barriers at the steps, known as Schwoebel barriers.
TL;DR: In this paper, the spatial resolution of Kelvin probe force microscopy measurement was investigated using cleaved Al0.3Ga0.7As/GaAs structures and Si-pn structures.
Abstract: Kelvin probe force microscopy was applied to the characterization of Al0.3Ga0.7As/GaAs multilayer structures and Si‐pn structures. The spatial resolution of Kelvin probe force microscopy measurement was investigated using cleaved Al0.3Ga0.7As/GaAs structures. A 40‐nm‐thick Al0.3Ga0.7As layer was resolved with potential difference of 15 mV. It was found that the measured potential is sensitive to the Al mole fraction for AlGaAs. Two‐dimensional delineation of Si‐pn structures was successfully carried out on the topmost and the cleaved surfaces. A decrease of a depletion‐layer width with increasing the intensity of light illuminating the sample was observed. It was confirmed through investigating illumination effects on various kinds of structures that the measured Kelvin probe force microscopy potential reflects the surface band structure of the sample. A lateral impurity profile under the ion implantation mask was extracted from the two‐dimensional potential image obtained on the cleaved pn junction by ca...
TL;DR: In this article, the authors used multiple internal transmission infrared absorption spectroscopy to probe the interface between the wafers upon initial joining and also during subsequent annealing steps, and observed a pronounced shift in the Si-H stretching frequency due to the physical interaction (van der Waals attraction) that occurs when the surfaces come into intimate contact.
Abstract: Silicon wafer bonding is achieved by joining two particle‐free silicon wafers and annealing to elevated temperatures (∼1100 °C). We have used multiple internal transmission infrared absorption spectroscopy to probe the interface between the wafers upon initial joining and also during subsequent annealing steps. For atomically flat hydrophobic wafers (H passivated), we observe a pronounced shift in the Si–H stretching frequency due to the physical interaction (van der Waals attraction) that occurs when the surfaces come into intimate contact. The hydrogen eventually disappears at high temperatures (1000 °C) and Si–Si bonds are formed between the two surfaces. For hydrophilic wafers (oxide passivated), we initially observe three to five monolayers of water at the interface (providing the initial attraction through H bonding), as well as the presence of hydroxyl groups that terminate the oxide at low temperature. Upon moderate heating (<400 °C), the water trapped at the interface dissociates and leads to the formation of additional oxide. Between 400 and 800 °C, the hydroxyl groups disappear, resulting in a corresponding increase in oxide and the formation of Si–O–Si bridging linkages across the two surfaces.
TL;DR: In this article, a force-based scanning Kelvin probe microscope has been applied to the problem of dopant profiling in silicon, where the detected electrostatic force couples the sample and only the tip at the end of a force sensing cantilever.
Abstract: A force‐based scanning Kelvin probe microscope has been applied to the problem of dopant profiling in silicon. Initial data analysis assumed the detected electrostatic force couples the sample and only the tip at the end of a force sensing cantilever. Attempts to compare measurements quantitatively against device structures with this simple model failed. A significant contribution arises from the electrostatic force between the sample and the entire cantilever, which depends strongly upon the relative size of the tip, cantilever, and lateral inhomogeneities in the surface topography and material composition of the sample. Actual and simulated measurements which demonstrate the characteristic signature of this effect are presented.
TL;DR: In this article, a trilayer resist process has been developed to provide smooth Ni etch mask edges by postbaking the top imaging resist and the resultant Si etched sidewall showed a roughness of 18.69 nm.
Abstract: Micromachined vertical mirrors and lenses in Si were fabricated as micro‐optical components. A Cl2 plasma generated by an electron cyclotron resonance source was used to etch these mirrors and lenses in Si and the etched Si sidewalls were characterized by atomic force microscopy and scanning electron microscopy. A trilayer resist process has been developed to provide smooth Ni etch mask edges by postbaking the top imaging resist. The resultant Si etched sidewall showed a roughness of 18.69 nm, as compared to the sidewall roughness of 29.95 nm without postbaking. As the plating current density was varied from 5 to 400 mA/cm2, the etched Si sidewall roughness increased from 24.31 to 43.69 nm. Optimized etch conditions were investigated for smooth Si sidewalls. Sidewall was much rougher with a roughness of 98.99 nm when 50 W rf power was applied for dry etching, whereas the roughness was only 29.95 nm when 100 W rf power was used. Additionally, thermal oxidation followed by oxide removal was able to reduce etched Si sidewall roughness. After oxide removal, the sidewall roughness decreased to 5.93 nm after 135 min wet oxidation at 1100 °C. However, oxide grown at 900 °C was less efficient for reducing the sidewall roughness as compared to 1100 °C. The deep etch‐shallow diffusion process was applied to fabricate micromirrors and microlenses. It was found that B diffusion at 1175 °C for 2 h decreased the Si sidewall roughness from 29.95 to 10.79 nm and selective wet etch lowered sidewall roughness further to 5.01 nm. Vertical micromirrors that were 40 μm tall and 2 μm wide were bonded onto the glass substrate and released. Microlenses that were 40 μm thick with radius of curvature of 50 μm have also been demonstrated.
TL;DR: The scanning probe microscope has demonstrated itself to be a versatile and effective tool for patterning surfaces at the nanometer scale Two common methods for modifying surfaces using probe microscopes are direct physical patterning and electric field assisted patterning.
Abstract: The scanning probe microscope ~SPM! has demonstrated itself to be a versatile and effective tool for patterning surfaces at the nanometer scale Two common methods for modifying surfaces using probe microscopes are direct physical patterning and electric field assisted patterning While both methods of surface modification are quite different, they both require that a sharp tip interacts with the surface to be patterned Physical patterning consists of scribing or indenting a sample using the tip of the SPM Jung 1 has used this process to scribe patterns into polymer surfaces, and Mamin 2 has used the physical indentation process in conjunction with laser heating to store 100 nm bits at 100 kHz in a polymer surface This approach has the advantage that the sample is typically much softer and generally unreactive with the tip, thereby reducing tip wear The literature on electrical modification of surfaces with probe microscopes is much more extensive Scanning probe lithography was pioneered by Dagata, 3 who patterned ^111& silicon with the scanning tunneling microscope ~STM!, and Lyding 4 has used this same technique in ultrahigh vacuum ~UHV! to pattern features less than a few nanometers Snow and Campbell have modified this technique and patterned Si 5 and GaAs 6 with the atomic
TL;DR: In this paper, the dependence of conductance on exposure dose was investigated for beam energies between 2 and 20 keV and a range of exposure doses, and it was found that the initial dependence was nonlinear and attributed to the change from a discontinuous to a continuous film, and to increased backscattering.
Abstract: Electron beam induced deposition from W(CO)6 was studied for beam energies between 2 and 20 keV and a range of exposure doses, to investigate the dependence of deposit thickness and electrical conductivity on energy and the dependence of deposit conductance on cumulative exposure dose. Larger deposited thicknesses and higher conductivities were produced at the lower beam energies and were attributed to the higher secondary electron yield at lower energies. The deposit thickness was found to scale linearly with exposure dose. The initial dependence of conductance on exposure dose (and deposit thickness) was nonlinear and was attributed to the change from a discontinuous to a continuous film, and to increased backscattering. The subsequent dependence of conductance on exposure dose was linear for deposit thicknesses which were small compared with the electron range, implying that burial precludes the further decomposition of partially decomposed W(CO)6 molecules incorporated in the deposit. Transmission ele...