The role of ion bombardment in plasma etch selectivity of organosilicate glass to etch stop layers of silicon carbide and silicon nitride has been investigated in a C4F8/N2/Ar plasma using a method that produces a narrow ion energy distribution (IED) at the substrate surface. The effects of the narrow IED are compared with those of the broad, bimodal IED produced by the conventional sinusoidal bias voltage wave form (at 13.56 MHz). A comparison of etch rate versus average ion bombardment energy shows a higher ion energy threshold for etching, a larger gap between the thresholds for the two materials, and high selectivity over a wider range of bias voltage with the narrow IED. A physical explanation of the observed phenomena is proposed.

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This paper proposes a novel miniaturization technique of quarter-wave transformers (QWTs), implemented using multi-section transmission lines (MSTLs), based on the quarter-wave-like transformer (QWLT) theory. Multi-section QWLT characteristics are derived analytically and solved via appropriate optimization algorithms for associated transmission-line parameters. For an illustration purpose, two-and three-section QWLT prototypes with 50% physical size reduction from the corresponding QWT size operating at 2.4 GHz are fabricated using microstrips and tested. It is found that these prototypes yield acceptable return loss at 2.4 GHz without significant bandwidth reduction, comparing to the QWT result.

Influence of ion mixing on the energy dependence of the ion-assisted chemical etch rate in reactive plasmasIn fluorocarbon-based plasma etching of dielectrics, deposition of fluorocarbon on the substrate contributes to a complex surface chemical structure that strongly affects etch rate and etch selectivity. Results reported herein demonstrate that the energy distribution of bombarding ions ͑IED͒ has a significant effect on this polymer layer, subsequently affecting etch rate and selectivity in submicron patterned structures. Specifically, we have narrowed the IED while keeping other process conditions unchanged by tailoring the shape of the rf voltage wave form used for substrate bias. Significant improvements in etch selectivity for organosilicate glass ͑OSG͒ over silicon carbide in a C 4 F 8 /N 2 / Ar plasma have been obtained by using a narrow IED compared to the broad IED resulting from the typical sinusoidal bias wave form. Trenches etched in OSG with the tailored bias voltage wave form show good feature profiles and high selectivity at feature bottoms. Slight differences in feature profiles between tailored and sinusoidal wave forms, as well as variations in etch selectivity with feature depth, are consistent with an enhancement in polymerization at the substrate in the case of the tailored bias voltage wave form.

Abstract-Conjugately characteristic-impedance transmission lines (CCITLs) are a class of transmission lines possessing conjugately characteristic impedances (Z ± 0 ) for waves propagating in the opposite direction. A typical Z 0 uniform transmission line is a special case of CCITLs whose argument of Z ± 0 is equal to 0 • . This paper aims to generalize the CCITL system by demonstrating a theoretical study of CCITLs and their applications in the microwave transistor amplifier design. It is found that the bilinear transformation plays an important role in transforming circles in the reflection coefficient Γ 0 -plane in the Z 0 system to the Γ-plane in the CCITL system. In addition, MetaSmith charts, a graphical tool developed for solving problems in the CCITL system, are employed to design matching networks to achieve desired amplifier properties. Results show that stability regions on Meta-Smith charts can be determined, and source and load reflection coefficients can be selected properly to obtain desired operating power gain. In addition, an example shows that Meta-Smith charts offer a simple approach for matching network design using open-circuited single-stub shunt tuners.