Electron-beam-induced deposition of materials has been known for almost 40 years from contamination writing. It has developed into “additive lithography” with nanometer resolution employed in scanning electron microscopes, in dedicated lithography systems, in reducing image projection systems, and in scanning tunneling microscopes. The technique allows deposition of nanometer- to micrometer-size structures with nanometer precision in three dimensions without supplementary process steps such as lift-off or etching procedures. Depending on the deposition conditions, novel compound materials are created from organometallic precursors which form resistors with a resistivity ranging from 103 Ω· cm to 2×10-3 Ω· cm and sustain current densities higher than 5×105 A/cm2 without damage. High-resolution transmission electron microscope analysis of the deposits reveals a new class of nanocrystalline compound materials. Crystals of metals or metalcarbides and oxides are immersed in a matrix of carbonaceous material. The deposition process is compatible with conventional VLSI technology. Tips for atomic force and scanning tunneling microscopy can be produced with radii of curvature as small as 5 nm. Field electron emission is obtained from deposited tips starting at an extraction voltage of 8 V and yielding 180 µ A of current at 20 V. Three-dimensional conducting structures can be produced as sensors.

A finely focused electron beam is used as a source of energy to decompose molecules, e.g., organometallics or hydrocarbons, adsorbed on the surface of a substrate. Films deposited by these means can be used as etch mask for reactive ion etching, as an absorber for various types of radiation, or directly as part of a device structure. A vector scan electron beam system with a LaB6 cathode has been equipped with a temperature controlled reservoir to supply vapors into a differentially pumped sample chamber. The substrate is mounted on a stage which can be cooled or heated in the range of −40 to +110 °C. The ability to utilize backscattered electron micro- scopy is maintained. Area, line, and spot deposition rates have been measured for tungsten hexacarbonyl [W(CO)6] and dimethyl–gold–trifluoro–acetylacetonate [Me2Au(tfac)] at various fluxes, sample temperatures, and current densities. Three-dimensional buildup of tips and free standing lines across holes in membranes and resolution better than 0.25 μm have been achieved. The composition of the deposited films has been analyzed and each deposit is rich in metal and carbon. Tungsten rich deposits can be used as a highly selective etch mask for oxygen plasmas. Effects limiting the ultimate resolution, such as backscattering from the substrate, and scattering from the deposited material are discussed.

The technique of electron-beam induced deposition allows three-dimensional structures to be generated on the nanometer scale. This is achieved in a scanning electron microscope equipped with a lithography attachment that enables separate position and time control for every pixel. By decomposing adsorbed molecules with the electron beam, structures are created on arbitrarily chosen substrates with nm precision under computer control. Deposits containing metallic nanocrystallites can be produced using organometallic precursor materials. The decomposition of cyclopentadienylplatinum (IV)-trimethyl (CpPtMe3) results in platinum single crystals with a 2 nm diameter embedded in a carbon-containing amorphous matrix. The metal content of deposits can be adjusted by choosing an appropriate acceleration voltage and beam current for deposition. The growth rate of deposits from CpPtMe3 is superior to that of frequently used organogold compounds. Tips can be deposited with growth rates up to 150 nm/s. This property is in favor of a higher throughput for nanofabrication. The deposition cross section for this precursor molecule is estimated at 1×10−16 cm2. The electrical resistivity of material deposited at room temperature is measured by a two-point technique and amounts to 1–100 Ω cm depending on the current employed for deposition. The technique is applied to generate fields of dot marks visible in the optical microscope for metrology purposes. These dot arrays can be fabricated on the surface of finished three-dimensional structures without additional treatments like resist deposition or development.

Articles you may be interested inNanostructuring of free-standing, dielectric membranes using electron-beam lithography J. Vac. Sci. Technol. B 31, 06F402 (2013); 10.1116/1.4820019 Advanced photolithographic mask repair using electron beams J. Vac. Sci. Technol. B 23, 3101 (2005); 10.1116/1.2062428High-speed and high-precision deflectors applied in electron beam lithography system based on scanning electron microscopy In situ electron-beam lithography on GaAs substrates using a metal alkoxide resist High-resolution electron-beam-assisted deposition and etching is an enabling technology for current and future generation photomask repair. NaWoTec in collaboration with Carl Zeiss NTS (formerly LEO Electron Microscopy) has developed a mask repair tool capable of processing a wide variety of mask types, such as quartz binary masks, phase shift masks, extreme ultraviolet masks, and e-beam projection stencil masks. Specifications currently meet the 65 nm device node requirements, and tool performance is extendible to 45 nm and below. The tool combines LEO's ultra-high-resolution Supra scanning electron microscope platform with NaWoTec's proprietary e-beam deposition and etching technology, gas delivery system, and mask repair software. In this article, we focus on tool performance results; that is, the reproducibility and accuracy of repair of clear and opaque programmed defects on Cr binary and MoSi phase shift masks. These masks have in the past been difficult to repair due to beam position instability caused by charging of the insulating quartz areas. We have found and implemented a solution to this charging problem and have demonstrated in spec repair of various defect types. The extendibility of e-beam-based repair technology to future lithography nodes, both in terms of the required resolution and the ability to repair next generation lithography mask types, will also be addressed.

Two- and three-dimensional patterns and structures can be grown by electron-beam induced deposition from organic and metalorganic precursors. Using a very fine electron beam in a dedicated field emission scanning electron microscope produces nanometer size deposits which extend from surfaces to heights in the micrometer range. The material is fed to the sample through a nozzle which presents a small leakage flux to the specimen chamber. Having an image processor attached to the microscope allows two- and three-dimensional deposition of material to be controlled. Selecting special speed rates for the motion of the beam generates inclined deposits even at a 90° beam landing angle. Combining a tilted sample and the two-dimensional way of structuring yield three-dimensional structures. These nanostructures have very special characteristics with respect to resistivity and shape. Selecting dimethyl- gold-trifluoro-acetylacetonate as precursor, a current of 1 nA, and a low electron energy of 10 keV for the deposition process, resistors of 700 Ω are obtained with a specific resistivity of 10−2 Ω cm.