Analysis of microhelix inductors with focused ion beam

Abstract

This paper describes a microhelix inductor structure fabricated with focused ion beam(FIB) stress introducing technology(SIT). With the decrease of the implantation does, the pitch and the diameter of the microhelix inductors decreases, which will also affect the performance of the microinductors. Microhelix inductors with different scales are fabricated from 120 nm thick, 2 um wide, 41um long aluminum microbeams, which are built on SOI substrate. The solenoid microinductor is fabricated with implantation does 2.83×1017cm-2. With different scales of microbeams and fabrication does, we get a microsolenoid inductor with pitch 6 um, diameter 2.3 um. So under the control of different FIB condition, we can get the desired microhelix inductor with needed pitch, diameter and turn number. The fabrication process is controllable and repeatable. We get the S parameters of the microhelix with the help of Agilent network analyzer from 100 MHz to 40 GHz at an interval of 50 MHz, after open structure and through structure deembedding process, the calculated inductance is as small as 10-4 nH, Quality factor arises from 0.02 to 0.55 when the frequency arises from 100 MHZ to 40GHZ respectively.