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Damage on the mask surface caused by charging effect during plasma etching process continues to attract much attention currently. For example, the round shape of holes can be changed into hexagonal shape. In our previous paper, the reason for this phenomenon has been explained through a particle simulation approach [P. Zhang et al., Plasma Sci. Technol.15 (2013) 570]. However, it has been observed that the round shape of holes in a mask can also be etched into an asymmetric shape due to factors such as nonuniform plasma source, inclination or vibration of sample platform, etc. This work further aims to explore the charging effect when the round-shaped holes in a mask have been changed into asymmetric-shaped ones by particle simulation method. The distribution of electric field produced by electrons was calculated for different shaped isolated holes (round, hexagonal and asymmetric shapes) in a mask as well as various heights from the mask surface. It is found that the field strength reaches its maximum around a hole edge and presents uniform distribution for the round hole and nonuniform distribution for the hexagonal- and asymmetric-shaped holes. The nonuniform electric field distribution can affect the trajectories of ions falling on the mask surface, further enhancing the asymmetry of the mask hole shape. Additionally, the charging effect on a mask of asymmetric holes aligned in a hexagonal array is also studied. It is found that due to the alignment of holes, the charging effect is quite different from the case in an isolated hole.

In the plasma etching technique, acquiring a high-quality transfer from the mask pattern onto the substrate under the suppression of the charging effects is of great significance. Most previous publications only focus on studying the charging phenomena on smooth round mask holes. This work shifted the target to an isolated mask hole with a rough edge using a classical particle simulation program, to examine the effects of edge roughness on surface charging for a mask hole. This study adopted the CF₄ plasmas, due to the widely used fluorocarbon plasmas for the contact-holes. Simulated results indicate that the mask holes with various shapes present differences in electric field ($E$-field) strength distribution, etching rate and profile evolution, relying on some condition parameters (roughness and reflection probability on the mask surface). The larger the dominant wavelength (DW), the more uniform the $E$-field distribution around the edge of the mask hole will be. The simulation of the profile evolution further confirmed that the deformation is in keeping with the distribution of the $E$-field. It was further found that the root mean square (RMS) of roughness increases with time in cases of the relatively small values of wavelength (10 and 35 nm) and decreases for other cases. Possible mechanisms behind have been discussed in detail. The findings of this work would shed light on an approach to maintain the pattern integrity.

Channel waveguides have been fabricated in x-cut lithium niobate (LiNbO₃) by proton exchange (PE) method and optically measured. The thickness and the optical constants of the thin PE layer were characterized using a prism coupling technique. The PE area was plasma etched and a 2.775-μm total etching depth was achieved. The measured average etching rate is 92.5 nm/min. One- and two-dimensional dense arrays of LiNbO₃ nanostructures have also been fabricated by using interference lithography (IL) and inductively coupled plasma reactive ion etching (ICP-RIE) techniques.

There is a demand for composite films with excellent hydrophobic properties in inertial confinement fusion (ICF) physics experiments. In this paper, we prepared fluorinated polyimide hydrophobic films using spinning and plasma etching methods. The experimental results indicate that the water contact angle for the perfluorodecyltrichlorosilane (PFTS) treatment polyimide (PI) film is 112.0${}^{\circ }$, which is larger than the pure PI film $(69.0^{\circ })$. The rap oil contact angle is 84.2${}^{\circ }$, which is also much larger than the contact angle of PI film $(12.0^{\circ })$. Moreover, the surface roughness of the prepared films was measured by white light interferometry (WLI). The surface roughness (Ra) of pure PI is 9.79nm, but with the application of FSiO₂ particles, the Ra of the films increases to 65.05nm. After plasma treatment, the Ra of the PI/FSiO₂ composite film increases to 186.71nm because plasma treatment can scratch the film surface and increase its roughness. However, treating the PI/FSiO₂ composite film with the plasma and PFTS, the Ra is only 88.90nm. This decrease in Ra is due to the PFTS, which is able to reduce the surface roughness. The development of composite films, compared to pure PI films, could prove to be an extremely valuable material in ICF experiments.