Electron-beam lithography

About: Electron-beam lithography is a research topic. Over the lifetime, 8982 publications have been published within this topic receiving 143325 citations. The topic is also known as: e-beam lithography.

Polymer Resist Systems for Photo- And Electron Lithography

Abstract: Modcrn technology is dependent on solid state electronics. Computers, communica­ tion equipment, medical instruments, and transportation systems all require complex electronic devices. The complexity of these devices is increasing each year, thus placing more demand on the materials and processes used in their fabrication. Manufacture of silicon integrated circuits (SIC) requires as many as 90 processing steps; a completed device is a complex structure containing five or more different materials, including dielectrics, conductors, and semiconductors. These materials, except the substrate semiconductor, are low-defect thin films ( < 3 JIm in most cases) deposited using a variety of techniques. The thin films must be patterned to form individual elements of an integrated circuit or other device. Shape and size of individual elements determine size, ultimate complexity, and operating parameters of a finished device. Increasing the scale of integration (device complexity) may reduce fabrication costs and increase performance; however, it requires a reduction in element geometry. Conventional pattern delineation is accomplished by etching a thin conductor or dielectric film through a polymer resist film that has been selectively patterned. The pattern conventionally is transferred to a resist by exposing to UV radiation through a mask. The polymer's solubility is altered by this exposure, and the pattern is developed by immersion in a solvent (developer), which removes the more soluble material. Resolution of photolithography is limited to 1·-3 JIm mainly as a result of the wavelength (300-40.0. nm) of radiation employed and mask technology. Exposure with short wavelength electrons is currently being developed at several laboratories for pattern generation of features less than I pm. This technique is used to fabricate master masks and complex integrated circuits. For either photo­ lithography or electron beam lithography to be useful, high-quality resist materials are required. This review attempts to cover materials and processing considerations for both photoresists and electron resists.

100 nm wide copper lines made by selective electroless deposition

Abstract: Copper lines with a minimum width of 100 nm were fabricated by selective electroless copper deposition (SED). The deposition reaction is based on the neutralization of positive copper ions in a basic solution by electrons which are the result of the reaction between formaldehyde and the hydroxyl ions. The reduction reaction requires a high pH typically in the range of 11.5-13 at the deposition temperature which is between 55 degrees C and 70 degrees C. The high pH required for the deposition reaction is achieved either by using alkaline bases, like sodium-hydroxide, or alkaline-free bases, like tetramethylammonium hydroxide (TMAH). Experimental data show similar results for both alkaline and alkaline-free deposition solutions. The copper nanolines were produced using electron beam lithography and polymethylmethacrylate (PMMA) e-beam resist due to its compatibility with the high pH of the deposition solution. The first approach, which is described here for making copper nanolines, produced 100 nm wide lines with vertical side walls and aspect ratio (height/width) as high as 4:1. The lines were uniform over both small and large areas and the deposition was only on the pre-designated regions (i.e. full selectivity). A second fabrication technique, which is also described, formed a fully-planar topography in which the copper is buried in an interlevel dielectric. 150 nm wide copper lines buried in 250 nm deep trenches in chemically-vapor-deposited (CVD) silicon-dioxide were made using that technique. Both techniques are described in detail and experimental results are presented in the form of SEM pictures. Selective copper deposition introduces some new problems in general and there are also some particular problems that are associated with the techniques described. Specific problems, such as step coverage and copper line shapes are discussed as well as more general problems like the compatibility with integrated circuit manufacturing technology.

Method of compensating the proximity effect in electron beam projection systems

Abstract: For compensating scattering losses of electrons in photoresists (proximity effect) which influence electron beam lithography by altering the pattern geometry it is suggested to expose selected partial areas of a pattern to an additional irradiation dosage in a second exposure step. For that purpose, a specific mask with corresponding correction openings can be used which is applied with the same, or with a different electron beam intensity. In a particularly advantageous manner the correction of the proximity effect can be achieved when complementary masks are used; the correction openings for the partial areas of the one complementary mask are arranged in the other complementary mask. The proximity effect is then corrected without an additional exposure step. For measuring the proximity effect a photo-optical process is suggested where line patterns with decreasing ridge width in the photoresist are defined through electron beam projection, and where the developing process of the photoresist is discontinued prematurely. The ridge edges which in the presence of the proximity effect are asymmetrical can be easily detected under the microscope.

Electron‐beam lithography with the scanning tunneling microscope

Abstract: The scanning tunneling microscope (STM), operated in vacuum in the field emission mode, has been used in lithographic studies of the resist SAL‐601 from Shipley. Patterns have been written by raising the tip–sample voltage above −12 V while operating the STM in the constant current mode. Resist films, 50 nm thick, have been patterned and the pattern transferred into the GaAs substrate by reactive ion etching. The variation of feature size with applied dose and tip–sample bias voltage has been studied. Comparisons have been made to lithography with a 10 nm, 50 kV electron e‐beam in a JEOL JBX‐5DII in the same resist thickness films. In all cases the resist films were processed in the standard fashion before and after exposure. The STM can write smaller minimum features sizes and has a greater process latitude. Proximity effects are absent due to the reduced scattering range of the low energy primary electrons. However, the writing speed is slower, being limited by the response of the piezoelectric scanner....

Secondary Electrons in EUV Lithography

Abstract: Secondary electrons play critical roles in several imaging technologies, including extreme ultraviolet (EUV) lithography. At longer wavelengths of light (e.g. 193 and 248 nm), the photons are directly involved in the photochemistry occurring during photolysis. EUV light (13.5 nm, 92 eV), however, first creates a photoelectron, and this electron, or its subsequent daughter electrons create most of the chemical changes that occur during exposure. Despite the importance of these electrons, the details surrounding the chemical events leading to acid production remain poorly understood. Previously reported experimental results using high PAG-loaded resists have demonstrated that up to five or six photoacids can be generated per incident photon. Until recently, only electron recombination events were thought to play a role in acid generation, requiring that at least as many secondary electrons are produced to yield a given number of acid molecules. However, the initial results we have obtained using a Monte Carlo-based modeling program, LESiS, demonstrate that only two to three secondary electrons are made per absorbed EUV photon. A more comprehensive understanding of EUV-induced acid generation is therefore needed for the development of higher performance resists