Suspended Spiral Inductor and Band-Pass Filter on Thick Anodized Aluminum Oxide

We make suspended inductors and 2.45 GHz BPFs on the selectively anodized aluminum. The thick anodized alumina is used as the supporting dielectric and it is easily removed by using chemical wet-etching. The thickness of anodized alumina is 80 mum and the depth of the total air-cavity is 200 mum. The fabricated inductor over an air cavity has a 25% greater Q factor and 21% higher inductance at 2 GHz compared to an inductor on anodized aluminum. The 2.45 GHz BPF adjusting the suspended inductors has 2.8 dB of insertion loss with a narrow bandwidth.