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Published in Robert Doering, Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology, 2017
Tungsten silicide is used in combination with polysilicon in so-called “polycide” structures in place of standard doped polysilicon. Its advantage over single-layer doped polysilicon is lower sheet resistance while maintaining polysilicon integration characteristics such as for polysilicon self-aligned gates. The most common applications are for the gate electrode and bit line in memory devices [108]. Tungsten silicide has similar oxidation resistance and wet chemical resistance (HF, RCA clean) as polysilicon and is thermally compatible with polysilicon. One of the reasons tungsten silicide stands out among the various silicides is its manufacturability by CVD.
Fabrication of polarization colour filter device via direct Au film imprinting
Published in Journal of Modern Optics, 2021
Figure 1 illustrates the fabrication process. Using the two-beam interference method, a subwavelength-structured surface pattern was formed on the substrate coated with a tungsten silicide (WSi) film using the sputtering method because this method enabled us to fabricate the gratings with simple equipment and easily control the grating periods. A photoresist was coated and exposed to an interference fringe from He-Cd laser beams (wavelength = 325 nm). Exposure was employed using two-beam interference to generate a short-period grating structure because the wire-grid polarizers with a period smaller than the wavelength exhibit higher transverse magnetic (TM, electric-field vector perpendicular to the grid) transmittance and higher extinction ratio. After the exposed photoresist was developed, the grating period, Λ, was calculated by where λ is the wavelength of the He-Cd laser and θ denotes the angle of beam incident on the photoresist film. The fringe period can be controlled by changing the incident angle, θ, of the two beams. Therefore, gratings with different periods can be fabricated using a two-beam interference system. In this experiment, the incident angle of laser beams was approximately 33°. After the development of the exposed resist, the WSi mask layer and SiC substrate were patterned using an inductively coupled plasma reactive ion etching apparatus (RIE, Samco RIE-200iP; Samco Inc.). The WSi mask layer and SiC substrate were etched using SF6 and CHF3 gases, respectively. The etching conditions were adjusted to fabricate sharp gratings considering secure demolding [5,20]. Figure 2 shows the scanning electron microscopy (SEM) images of the fabricated SiC mold. As shown in Figure 2, a sharp grating structure was formed on the SiC surface, and the sidewall roughness was hardly observed. The grating period (Λ), fill factor (f), and depth (d) of the SiC mold were 300 nm, 0.5, and approximately 240 nm, respectively. The mold was a one-dimensional, periodic, sharp structure to increase the tip pressure.