Optimal inductance and capacitance values of a receiver (Rx) LC matching network are proposed in order to maximize the efficiency of capacitive wireless power transfer (CWPT). To maximize the overall Tx-to-load efficiency, a general polynomial equation is proposed that gives an optimum Rx inductance and capacitance value under the given constraints of inductor losses, load impedance, and coupling capacitance. It is found that the efficiency is maximized when the Rx input resistance is approximately equal to the impedance of the coupling capacitance. It is also shown that Tx inductance and capacitance values should be chosen based on the trade-off between efficiency and Tx amplifier operation. The proposed method is applied to wireless charging of an Unmanned Aerial Vehicle (UAV) because the small Rx plate of CWPT can easily be mounted on a UAV. The fabricated system delivers 45 W with overall efficiency of 78.2% across wide lateral misalignments even with a small Rx plate at 6.78 MHz.
As the feature sizes of integrated circuits shrink, thinner photoresist coating should be used in order to avoid high aspect ratio which can cause pattern collapse. Especially for 193 nm lithography, photoresist coating is too thin to subsequent etching step. One of the solutions to this problem is using hardmasks which have good etch selectivity to adjacent layers. In this paper, silicon-based anti-reflective spin-on hardmasks (Si-SOH) are described. One of the major problems of silicon based polymers in the hardmask compositions is poor storage stability because silanol group is reactive enough to condense each other, which can instigate molecular weight increase to yield gel-type particles. The storage stability of our hardmask materials have been improved by thermodynamically controlled synthesis and reactive mask strategy. Especially the reactive masked silanol groups can take part in crosslinking reaction under the process conditions without additional deprotection step. Although this strategy could encounter intermixing problems with other layers, we can produce silicon-based hardmasks without any deleterious effects. These hardmasks show antireflective properties and great etch selectivity to both photoresists and organic hardmasks (C-SOH).
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