Electron beam lithography drawbacks

Many synthetic processes and techniques to obtain IONPs have been developed, which are classified in physical and chemical methods. Initially, methods such as gas phase deposition and electron beam lithography were used. However, their main drawback is the inability to control the nanometric size of particles. In contrast, chemical routes are simpler, more efficient and tractable, with appreciable control over the size and, sometimes, the shape of particles. Most chemical syntheses are based on the coprecipitation of Fe2+ and Fe3+ aqueous salt solutions by addition of a base [32, 33]. 

Ion-beam lithography is not without its drawbacks, especially when compared to electron-beam lithography. Shot noise is a major issue for ion-beam lithography, just as it is for electron-beam lithography. Ion current densities are significantly lower than electron current densities, a limitation that is somewhat offset by the fact that each ion deposits more energy into the resist than an electron deposits, which implies that lower doses are needed to produce the same exposure effect when using ions relative to when electrons are used. °... 

Elegant results have been achieved by electron-beam exposure of supramolecular films. However, there are a number of drawbacks associated with electron beam lithography that should be borne in mind. First, state-of-the-art electron beam lithography apparatus is fast and very powerful, but it is also expensive and usually requires maintenance by skilled staff. For researchers with a major facility in a neighboring laboratory, it may be a very attractive tool. 

Perhaps the simplest and oldest pattern transfer technique is wet etching, which is surprisingly effective even for copolymer templates. Typical use of wet etching involves photolithography or electron beam lithography to selectively expose substrate areas for dissolution. An aggressive liquid etchant is then used to remove exposed areas of a wafer. One historical drawback has been the isotropic nature of many etchants so that high aspect features are difficult to fabricate. However, as will be discussed in Section 9.6, some success has been reported for copolymer templates. 

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