Various scanning probe lithography methods have been utilized to manipulate and modify materials in a nanometer scale resolution. Since SPL does not use light for lithography, it is not limited by the diffraction limit, and its resolution can be as small as individual atoms. Another important advantage is that it can be used under quite versatile environments including ambient, liquid and vacuum (Table 1). For this reason, SPL method has been applied for patterning soft and biological materials that are very sensitive to environmental conditions. In addition, since many SPL processes can be done under ambient conditions, SPL does not require extensive instruments for environmental control and its instrumentation cost is much lower than those for other lithography techniques (e.g. e-beam lithography, focused-ion beam etc).
One major bottleneck applying SPL methods for industrial application is its throughput. Since SPL is a serial patterning process in nature, it is usually slower than parallel patterning processes such as photolithography. One obvious solution is having multiple probes patterning simultaneously. Parallel patterning systems have been realized for some SPL processes such as dip-pen nanolithography, nanomelting, and nanoox-idation. As the parallel SPM technology advances, the throughput is expected to improve.
SPL is expected to have immediate applications for high-resolution rapid prototyping and custom manufacturing area (Figure 14). These include fabrication of prototype nano-devices, photomask repair, mask-less lithography, etc. In SPL processes, the patterns designed in the computer can be directed printed to the substrates without extensive preparation steps. It makes SPL strategy an ideal method for custom-design high precision manufacturing tools like e-beam lithography does for microelectronics industry. However, SPL strategy has several advantages over other custom manufacturing tools: 1) high resolution down to single atomic level, 2) versatile lithography environments friendly to soft and biological materials, and 3) low instrumentation cost.
Now, SPL strategy provides quite a versatile tool set for nanotechnologists, and it has become an essential tool kit for research and development in the age ofnanotechnology.
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