High-resolution lithography, exposure

A photosensitive composition, consisting of an aromatic azide compound (4,4 -diazidodi-phenyl methane) and a resin matrix (poly (styrene-co-maleic acid half ester)), has been developed and evaluated as a negative deep UV resist for high resolution KrF excimer laser lithography. Solubility of this resist in aqueous alkaline developer decreases upon exposure to KrF excimer laser irradiation. The alkaline developer removes the unexposed areas of this resist. 

Lithography In order to precisely resolve the nanometer structures in microelectronics, various enhancement techniques have been applied to the current optical exposure tools that are equipped with deep UV light (193 nm wavelength). These enhancement techniques include phase-shift masks and immersion lenses (putting a liquid between final lens of the stepper and the wafer). The trade-off for the high resolution of modern steppers is an extremely small depth of focus (DOF) that is around 0.5pm over a typical field size of... 

The two principal modes of operation of electron-beam exposure systems include the maskless direct-write electron-beam machines and the mask-based electron-beam machines. Direct-write electron-beam machines operate directly from design data and are capable of extremely high resolution. Mask-based electron-beam systems utilize masks in their imaging process. The implementation of electron-beam lithography in mix-and-match mode with optical lithography in a manufacturing environment has been demonstrated. 

The nano-antennas where fabricated on top of a 200 nm silicon dioxide layer on a standard silicon wafer. The substrate was spin coated with high resolution positive PMMA 950 K resist and electron beam lithography was used to define the nano-antenna structures. After exposure, the samples where developed in a M1BK 1PA solution with a 1 3 composition. Finally, silver was thermally evaporated and Ufted-off to remove of the unwanted residual metal areas. The total number of nano-antennas created was 6.25 x 10 distributed over an area of 2.13 mm. Although the final array of nano-antennas was laid on top of a dielectric layer of silicon dioxide, the silicon substrate obstructed the transmitted light. In Fig. 1.21, SEM pictures at different magnifications show the obtained results through this process. The two transversal nano-antennas in an L shape form a... 

The tynthetic flodbility and demonstrated performance (e.g., photospeed and contrast) of the positive PCB resists based on functional methaoylate polymers provided the incentive to extend the methaoylate terpotymer design concepts to the submicron lithography arena. The methacrylate terpolymers have been modified in attempts to provide thin film, high resolution resists suitable for exposure at 248 and 193 nm. This woric demonstrates that high performance and low materials cost are not mutually e lusive. 

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