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Si Nanowire Grids Polarize Down to 193 nm

The continual decrease in microelectronic device feature size, captured in the famous "Moore's Law", has come in part from a decrease in the wavelength of light used in the photolithographic steps used to pattern these features. Today, the most advanced production photolithography uses 193 nm ultraviolet (UV) light from an ArF excimer laser. At such short wavelengths, control of the polarization of the light becomes critical for achieving minimum feature size. Recently, PCCM researchers demonstrated a method for making grids of silicon (Si) nanowires, spaced by only 33 nm but aligned over square-inch areas. These Si grids polarize ultraviolet and deep ultraviolet light, even down to 193 nm. Since these polarizers are compact, do not deflect the beam, and function with light as it is being focused, they can be inserted into the lithographic optical train- and could also be used in the immersion lithographic processes which are on the horizon.



Figure 1: Schematic of the process flow for the fabrication of a Si nanowire polarizer.

Figure 2: Scanning electron microscope image of an oblique view of a Si nanowire grid, supported on a transparent quartz substrate. The wires have a pitch (line + space) of 33 nm.