This study presents a detailed fabrication method, together with validation, discussion, and analysis, for state-of-the-art silicon carbide (SiC) etching of vertical and bevelled structures by using inductively coupled plasma reactive ion etching (ICP-RIE) for microelectronic applications. Applying different gas mixtures, a maximum bevel angle of 87° (almost vertical), large-angle bevels ranging from 40° to 80°, and small-angel bevels ranging from 7° to 17° were achieved separately using distinct gas mixtures at different ratios. We found that SF6 with additive O2 was effective for vertical etching, with a best etching rate of 3050 Å/min. As for the large-angle bevel structures, BCl3 + N2 gas mixtures show better characteristics, exhibiting a controllable and large etching angle range from 40° to 80° through the adjustment of the mixture ratio. Additionally, a Cl2 + O2 mixture at different ratios is applied to achieve a small-angel bevels ranging from 7° to 17°. A minimum bevel angel of approximately 7° was achieved under the specific volume of 2.4 sccm Cl2 and 3.6 sccm O2. These results can be used to improve performance in various microelectronic applications including MMIC via holes, PIN diodes, Schottky diodes, JFETs’ bevel mesa, and avalanche photodiode fabrication.
Bulk absorption-based microwave humidity sensing characteristics of a laser-induced graphene (LIG) is investigated for the first time. An LIG flake with a 3D network of high-porosity patterned on a polyimide substrate using CO2 microlaser is integrated into the capacitive sensing region of a 1.985 GHz microwave resonator. The performance evaluation reveals that the developed microwave-LIG sensor linearly detects the wide range of relative humidity (10%–95% RH) with a high sensitivity, short response and recovery times (< 6 s), and small hysteresis (up to 0.375% RH); thus validating the high-performance intrinsic humidity sensing characteristics of LIG at microwave regime.
This paper presents highly selective, low-loss, and miniaturized balun devices fabricated using the integrated passive device (IPD) technique for the GSM band (900/1800 MHz) and the WiFi band (2400 MHz) in mobile applications. Balun devices were fabricated on a gallium arsenide (GaAs) substrate using the IPD fabrication process to reduce the overall size (0.05λ g × 0.036λ g at 900 MHz). Each device is the combination of lattice lumped structure with a low-pass filter and a high-pass filter configuration. This structural formation of lumped elements helps to reduce the phase mismatch error in the balun devices. For all the balun devices, the measured results indicated a minimum amplitude imbalance (<0.47 dB) and low phase imbalance (180 ± 2.6 • ). Mathematically calculated, calculated after considering parasitic effects, simulated and measured results exhibited a good correlation. The return loss is below 18 dB and insertion loss is below 0.25 dB for the entire fabricated devices. A balun device with a center frequency of 900 MHz has given the best results amongst all fabricated devices. INDEX TERMS Integrated passive device (IPD), gallium arsenide (GaAs), MIM capacitor, spiral inductor.
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