摘要:

Electron beam lithography (EBL) and scanning probe lithography (SPL) are electron exposure techniques capable of high resolution patterning of organic resists. This article compares the exposure properties of these two systems. We consider the resist sensitivity to EBL and SPL electrons, exposure tolerances, patterning linearity, and proximity effects. It is possible to print sub-50 nm features using both systems, but SPL has a wider exposure latitude at these small feature sizes. SPL requires a significantly higher incident electron dose for exposure than does EBL. In EBL, lithography control is most limited by proximity effects which arise from backscattered electrons whose range is considerably larger than the forward scattering range in the resist film. As a result, the exposed feature dimension depends strongly on the local feature density and size, leading to unacceptable linewidth variations across a wafer. These limitations are alleviated in the case of SPL exposures. We demonstrate improved linearity and reduced proximity effects with SPL. We have patterned 200 nm pitch grids with SPL where all individual features are resolved. The linewidth of features in these grids is the same as the width of an isolated line at the same dose. Finally, we suggest that the SPL exposure mechanism may be different than that for EBL.

ISSN:1071-1023    

DOI:10.1116/1.590425

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The selective removal of hydrogen from a passivated Si(100) surface with an ultrahigh vacuum scanning tunneling microscope (STM) allows nanometer-sized “templates” of clean Si(100) to be defined on an otherwise unreactive surface. Such depassivated areas have already been shown to react selectively withO2andNH3in preference to the surrounding H-terminated surface. This selectivity suggests two more sophisticated approaches to fabricating nanostructures with this technique: (1) selective metallization by thermal chemical vapor deposition, and (2) formation of ordered organic monolayers by reaction with specific organic molecules. In the first case, an intrinsic difference in the reaction rate of a metal precursor with the clean and H-terminated Si(100) surface results in selective deposition of a metal on the STM-patterned area. In order to prevent hydrogen desorption and loss of selectivity, the metal precursor must dissociate its ligands at relatively low temperatures. In the second case, the patterned surface is exposed to an organic molecule expected to react in a site specific manner with unsaturated Si dimer sites. An example of this site selective reaction is the[2+2]cycloaddition reaction between carbon–carbon double bonds and the Si dimer bond. Such reactions can result in the formation of spatially resolved nanometer-sized regions containing organic monolayers. In this article we describe progress toward the fabrication of nanostructures utilizing these two techniques. First, we discuss the use of a new amidoalane precursor for the selective chemical vapor deposition of aluminum on STM-patterned Si(100) surfaces, as well as the selective patterning of a nucleation promoter,TiCl4,commonly used to initiate aluminum film growth. We also discuss the selective chemisorption of norbornadiene (bicyclo[2.1.1] hepta-2,5-diene) on STM-patterned areas. STM images reveal the formation of a norbornadiene adlayer with indications of local ordering. Both of these methods show promise as techniques for the fabrication of nanostructures on Si(100) surfaces.

ISSN:1071-1023    

DOI:10.1116/1.590426

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Recently, we have shown that small trenches in amorphous carbon films can be produced by a field induced local oxidation with a voltage biased cantilever tip in a scanning force microscope. The depth of the holes and the trenches corresponds to the total thickness of the carbon film while the width was found to be as small as 30 nm. Amorphous carbon films as resist masks for lithography show some advantageous properties, e.g., the stability against halogen plasma etching, negligible chemical reactivity with most substrates and the possibility of removing the mask by oxygen reactive ion etching. In this article, we demonstrate the transfer of the carbon patterns into metal films by argon ion beam etching. By this new method, we produced 10-nm-wide trenches in thin AuPd films. Furthermore, we made small gaps in narrow AuPd lines which have been predefined by conventionale-beam lithography. In order to control and minimize the width of the gaps, the resistance of the conducting lines was controlledin situduring ion beam etching.

ISSN:1071-1023    

DOI:10.1116/1.590435

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Wires of the high temperature superconductorYBa2Cu3O7−δ(YBCO) were fabricated by electron beam lithography and were subsequently modified further on a sub-100 nm scale using the scanning tunneling microscope (STM). The process responsible for this modification has been shown to be field enhanced corrosion of the YBCO surface in the presence ofCO2andH2O.The intention of this work is to investigate the effect of the STM induced modifications on the electrical transport behavior of the YBCO wires with current–voltage characteristics (CVCs) measured at 77 and 4.2 K. Different types of CVCs can be distinguished, depending on the size of the cut into the wire generated by the STM. The measured characteristics will be explained by thermal self-heating at locations of the wire induced by the STM. Thus, the STM modifications initiate thermal domains in the wire where the Joule heat emission generated at sufficient high current values raise the temperature of the wire above its critical temperature. Furthermore, a steplike structure in the CVC of a STM fabricated nanobridge is detected, which we attribute to an increase of the number of vortex trajectories as the transport current through the wire is increased.

ISSN:1071-1023    

DOI:10.1116/1.590427

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We demonstrate a fabrication method to define high-density, uniform nanostructures by electron beam lithography at conventional beam voltages (<40 kV). Here we optimize the exposure and development conditions needed to generate such nanostructure arrays using polymethylmethacrylate as positive resist and isopropyl alcohol as a developer. Arrays of 12 nm dots with 25 nm period and 20 nm lines with 40 nm period were fabricated to show the resolution of this optimized process.

ISSN:1071-1023    

DOI:10.1116/1.590428

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A simple fabrication method for submicron diameter metallic apertures using negative electron beam resist and metal lift-off has been developed. In general, the lift-off process is beneficial for semiconductor quantum dot spectroscopy, since the original surface condition of the substrate is not altered or destroyed as it may be in a conventional dry or wet etching processes to form apertures in a subtractive process. With an optimum combination of process parameters, such as higher pre- and postexposure bake temperatures for longer times, longer developing time and with optimal mixtures of developers, high aspect ratio resist posts were obtained. Using 20 kV single dote-beam exposure, a reentrant profile can be obtained directly. While this profile is not obtained with 50 kV single dote-beam exposure, a higher aspect ratio (∼7:1) and sub-100 nm diam resist posts are possible. High vertical sidewall 100 nm diam resist posts are obtained using 50 kV areae-beam exposures. Taking advantage of these characteristics: high aspect ratio, high vertical resist sidewall, and resist undercut at the bottom of post, sub-100 nm diam apertures in 100 nm thick metallic films are obtained by evaporation of metal on the sample and dissolving the resist post in solvent. For sub-100 nm apertures, a significant improvement in aperture edge smoothness was achieved by applying an oxygen plasma.

ISSN:1071-1023    

DOI:10.1116/1.590429

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

To achieve a fine periodic semiconductor structure by electron beam (EB) lithography, calixarene was used as an EB resist. A 25 nm pitch InP pattern was formed successfully and 40 nm pitch InP structures were achieved with good reproducibility. A shorter developing time, precise stage motion, accurate control of the widths of lines and spaces, and slightO2ashing were important to obtain a fine InP pattern by a two-step wet chemical etching process. Furthermore, the fabricated periodic InP pattern was buried in a GaInAs structure by organometallic vapor phase epitaxy. The introduction of tertiarybutylphosphine as the phosphorus source prevented the fine structure from deforming when the temperature was raised and a 25 nm pitch periodic structure was buried successfully.

ISSN:1071-1023    

DOI:10.1116/1.590430

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A 50 kVGa+focused ion beam was applied for milling submicronPt-(La0.5Sr0.5)CoO3–Pb(NbxZryTiz)O3–(La0.5Sr0.5)CoO3–Pt-based ferroelectric capacitor heterostructures prepared by pulsed laser and sol-gel deposition techniques. The milling yields were found to be0.22±0.02 μm3/nCforPb(NbxZryTiz)O3,0.3.4±0.01 μm3/nCfor(La0.5Sr0.5)CoO3,and0.34±0.06 μm3/nCfor Pt layers. The influence of the ion beam current and its scan strategy, as well as depth of milling, on the quality of fabricated structures was studied. The minimum sizes down to 0.017 μm2for the top electrode, and 0.04 μm2for the capacitor structures milled to the bottom electrode were achieved without an additional sacrificial layer. A scanning probe microscopy technique was employed to test the properties of the milled capacitor structures.

ISSN:1071-1023    

DOI:10.1116/1.590431

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Diffractive optical components can be made using multiple level kinoforms or single level artificial dielectric structures. The latter require the fabrication of pillars of equal depth but differing width and spacing. As a demonstration device, the diffractive optic equivalent of a wedge has been made in GaAs for use at 1.15 μm. The need for all pillars to have the same height was met by using a selective etch and a very thin etch-stop layer on AlGaAs. The experimental diffraction efficiency was 87.8%, among the best ever obtained and close to the theoretical maximum of 97.6%.

ISSN:1071-1023    

DOI:10.1116/1.590432

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We have microfabricated two-dimensional (2D) photonic band gap structures in a thin slab of dielectric material to define reflectors and high-Qmicroresonators. By selectively omitting holes from the 2D photonic crystal, optical microcavities, and in-plane microresonator switches can be defined. We have designed this structure with a finite difference time domain approach, and demonstrate the effect of lithographic 2D band gap tuning on the emission spectra of InGaAs/InGaAsP multiple quantum well material emission wavelength of 1.55 μm.

ISSN:1071-1023    

DOI:10.1116/1.590433

出版商:American Vacuum Society    

年代:1998

数据来源: AIP