Electron-beam lithography with the scanning tunneling microscope

Marrian, C. R. K.

doi:10.1116/1.585978

Cited by 71 publications

(28 citation statements)

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“…Most of these techniques take advantage of the spatial resolution of the electronic emission from a tip to locally expose ultrathin electron resists [367][368][369][370], such as self-assembled monolayers [371,372] or Langmuir-Blodgett films [373], or to directly modify the structure of the superficial layer [374][375][376][377], such as the oxygenation of hydrogenated silicon [378,379]. A few methods based on mechanically engraving a soft layer with the sharp atomic microscope tip have also been proposed [380].…”

Section: Introductionmentioning

confidence: 99%

Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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Laser ablation of polymers has been studied with designed materials to evaluate the mechanism of ablation and the role of photochemically active groups on the ablation process, and to test possible applications of laser ablation and designed polymers. The incorporation of photochemically active groups lowers the threshold of ablation and allows high-quality structuring without contamination and modification of the remaining surface. The decomposition of the active chromophore takes place during the excitation pulse of the laser and gaseous products are ejected with supersonic velocity. Time-of-flight mass spectrometry reveals that a metastable species is among the products, suggesting that excited electronic states are involved in the ablation process. Experiments with a reference material, i.e., polyimide, for which a photothermal ablation mechanism has been suggested, exhibited pronounced differences. These results strongly suggest that, in case of designed polymers which contain photochemically active groups, a photochemical part in the ablation mechanism cannot be neglected. Various potential applications for laser ablation and the special photopolymers were evaluated and it became clear that the potential of laser ablation and specially designed material is in the field of microstructuring. Laser ablation can be used to fabricate three-dimensional elements, e.g., microoptical elements.Keywords Laser ablation · Ablation mechanism · Photopolymers · Polyimide · Spectroscopy This was not always true, of course. For many years, the laser was viewed as "an answer in search of a question". That is, it was seen as an elegant device, but one with no real useful application outside of fundamental scientific research. In the last two to three decades however, numerous laser applications have moved from the laboratory to the industrial workplace or the commercial market. Lasers are unique energy sources characterized by their spectral purity, spatial and temporal coherence, and high average peak intensity. Each of these characteristics has led to applications that take advantage of these qualities: -Spatial coherence: e.g., remote sensing, range finding and many holographic techniques. -Spectral purity: e.g., atmospheric monitoring based on high-resolution spectroscopies. -and of course the many other applications in communication and storage, e.g., CDs.All of these high-tech applications have come to define everyday life in the late twentieth century. One property of lasers, however, that of high intensity, did not immediately lead to "delicate" applications but rather to those requiring "brute force". That is, the laser was used in applications for removing material or heating. The first realistic applications involved cutting, drilling, and welding, and the laser was little more advanced than a saw, a drill, or a torch. In a humorous vein A.L. Schawlow proposed and demonstrated the first "laser eraser" in 1965 [4], using the different absorptivities of paper and ink to remove the ink without damaging the und...

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Section: Introductionmentioning

confidence: 99%

Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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“…Alternatively, the STM can be used to expose organic resist layers. For example, McCord et al 3 have used poly͑methylmethacrylate͒ PMMA, Marrian et al 4 have used SAL 601 and recently Stockman et al 5 have used a Langmuir-Blodgett film. Since these layers do not always conduct sufficiently, the STM tip can penetrate the resist during lithography which can limit the tip lifetime due to mechanical interactions between tip and layer.…”

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confidence: 99%

“…[1][2][3][4][5][6][7] In scanning tunneling microscopy tip-substrate interactions are very local, making it possible to modify the surface of a substrate to a very high lateral resolution ͑Ͻ20 nm͒. Several methods to fabricate metallic nanowires using this technique, have been demonstrated.…”

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confidence: 99%

Fabrication of metallic nanowires with a scanning tunneling microscope

Kramer

Birk

Jorritsma

et al. 1995

Applied Physics Letters

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A procedure to pattern thin metal films on a nanometer scale with a scanning tunneling microscope ͑STM͒ operating in air is reported. A 30 nm film of hydrogenated amorphous silicon ͑a-Si:H͒ is deposited on a 10 nm film of TaIr. Applying a negative voltage between the STM tip and the a-Si:H film causes the local oxidation of a-Si:H. The oxide which is formed is used as a mask to wet etch the not-oxidized a-Si:H and subsequently, the remaining pattern is transferred into the metal film by Ar ion milling. Metal wires as narrow as 40 nm have been fabricated. Since a-Si:H can be deposited in very thin layers on almost any substrate, the presented procedure can be applied to structure all kind of thin films on a nanometer scale. © 1995 American Institute of Physics.During the previous 5 years, the scanning tunneling microscope ͑STM͒ has attracted interest as a tool for lithography on a nanometer scale. [1][2][3][4][5][6][7] In scanning tunneling microscopy tip-substrate interactions are very local, making it possible to modify the surface of a substrate to a very high lateral resolution ͑Ͻ20 nm͒. Several methods to fabricate metallic nanowires using this technique, have been demonstrated. Ehrichs et al. 2 and McCord et al. 3 have used an STM induced chemical vapor deposition ͑CVD͒ process in which a metalorganic gas is decomposed between the STM tip and the substrate, depositing metal on the substrate surface. A drawback of this technique is that there is only a limited choice of metals which can be deposited, due to the number of gas precursors which are available. Alternatively, the STM can be used to expose organic resist layers. For example, McCord et al. 3 have used poly͑methylmethacrylate͒ PMMA, Marrian et al. 4 have used SAL 601 and recently Stockman et al. 5 have used a Langmuir-Blodgett film. Since these layers do not always conduct sufficiently, the STM tip can penetrate the resist during lithography which can limit the tip lifetime due to mechanical interactions between tip and layer.In this letter, we present a method to pattern a thin film on a nanometer scale with an STM operating in air, using on a conducting resist layer. The method was inspired by the work of Dagata et al. 1 who demonstrated that a hydrogen terminated silicon ͑111͒ surface can be locally oxidized with the STM. The oxide layer which is formed can act as a mask for etching the silicon, as was demonstrated by Snow et al. 6A thin film could be patterned with this method if a silicon layer which is both stable against oxidation in air and sufficiently conducting could be deposited on the metal film. Hydrogenated amorphous silicon ͑a-Si:H͒ is a material which can fulfill both requirements. It is stable against oxidation in air because of its high hydrogen content ͑Ϸ10 at. %͒.8 Thin films of a-Si:H can be highly doped, to make them electrically conducting for STM operation. In addition, with plasma enhanced chemical vapor deposition ͑PECVD͒ a layer of a-Si:H can be deposited on almost any surface at low temperature, because of the high r...

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“…It may be possible to achieve lower minimum feature sizes by patterning at other soft X-ray energies. Patterning with lower energy electrons has been reported to decrease linewidths [51,52] but to our knowledge this has not been explored for patterning with monochromatic X-rays. We note that lower electron beam energy is not intrinsically a recipe for higher resolution since the electron beam writers used to fabricate the smallest zone width zone plates, such as the LBNL Nanowriter [53], operate at 50-100 keV.…”

Section: Improving the Optics And Exploring New Energiesmentioning

confidence: 98%

Zone plate focused soft X-ray lithography

Leontowich

Hitchcock

2011

Appl. Phys. A

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The zone plate focused soft X-rays of a scanning transmission X-ray microscope have been used to pattern poly(methyl methacrylate) and poly(dimethylglutarimide) films by a direct write method which is analogous to lithography with a focused electron beam. The lithographic characteristics of both polymers have been determined for 300 eV X-rays. With low doses (1 MGy), developed lines 40 ± 5 nm wide were created in poly(methyl methacrylate). At higher doses an exposure spreading phenomenon substantially increases the lateral dimensions of the developed patterns. The spreading mechanism has been identified as the point-spread function of the zone plate lens. The performance of focused soft X-ray lithography is compared to other direct write methods. The practicality of a dedicated focused soft X-ray writer instrument is discussed.

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Electron-beam lithography with the scanning tunneling microscope

Cited by 71 publications

References 0 publications

Laser Application of Polymers

Laser Application of Polymers

Fabrication of metallic nanowires with a scanning tunneling microscope

Zone plate focused soft X-ray lithography

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