Three-dimensional micromachined on-chip inductors for high frequency applications

Demands for wireless communication are ever-escalating for consumer and military communication applications. The requirements of portability, more functionality and lower cost have been driving forces toward smaller, more sophisticated and flexible wireless devices with lower power consumption. To meet these requirements, monolithically integrated passive inductors with high Q-factors and high self-resonant frequencies are desirable. Q-factor and self-resonant frequency of an inductor are significantly degraded at high frequencies due to conductor ohmic loss, magnetically induced eddy current in the conductive substrate, and lower self-resonant frequency from capacitance between conductive substrate and conductors. In this dissertation, novel three-dimensional arch-like solenoid and dome-shaped spiral inductors are designed, fabricated, and characterized. MEMS-based fabrication techniques such as copper electroplating through voids in thick SU-8 photoresist molds and EAGLE2100 conformal photoresist molds on sacrificial arch-like or dome-shape SJR5740 photoresist mounds are utilized. An air gap between the inductor and the silicon substrate is used to reduce the degradations of inductor performance. According to the Sonnet electromagnetic simulations, 30 μm air-gap suspension over the substrate is an adequate choice for these inductors. Suspended arch-like solenoid copper inductor has flat bottom conductor connected to arch-like top conductor with an air core in between. This design has only 2 contact points per inductor turn to minimize series resistance. Suspended domeshaped spiral copper inductor is fabricated on a sacrificial photoresist dome with the outer end connected to one probe pad, and the inner end connected to the other probe pad through vias and an air-bridge. The sidewalls of spiral turns in this design overlap less with each other thereby reducing inter-turn capacitances. Fabricated inductors are characterized and modeled at high frequencies from Sparameter measurements. ABCD-parameters, derived from the S-parameters are translated into a simplified physical π-model. The resulting arch-like suspended inductors with 2-5 turns have inductances between 0.62 to 0.79 nH, peak Q-factor values between 15.42 to 17 at peak-Q frequencies between 4.7 GHz to 7.0 GHz, and self-resonant frequencies between 47.6 GHz to 88.6 GHz. The 3-turn dome-shaped spiral inductor has inductance of 3.37 nH, peak Q-factor of 35.9 at 1.65 GHz, and self-resonant frequency at 18.74 GHz

Metal-embedded SU-8 Slab Techniques for Low-resistance Micromachined Inductors

This work presents a new fabrication technique for micro power inductors by using metal-embedded SU-8 slab molding techniques. The proposed technique uses X-ray lithography to fabricate high-aspect-ratio LIGA-like microstructures in form of embedded structures in the SU-8 slab. This process was applied to fabricate an inductor’s windings with an aspect ratio of 10, which can provide very low resistance but still preserve a small form factor and low profile. Inductors were designed as pot-core structures with overall heights of 370 μm and embedded with 250-μm-thick windings. From the advantage of metal embedded SU-8 slab techniques, 8 μm-thick permalloy core could be fabricated by electroplating around the winding in a single step that could help simplify the process. Four types of inductors were fabricated with 3, 5, 10, and 16 turns in the area of 1.8 to 9.5 mm2. The measured inductance was in the range of 70 nH to 1.3 μH at 1 MHz and DC resistance of 30–336 mΩ for 3–16 turns, respectively. The DC resistance of fabricated inductor was low, as expected, and showed good result compared with the results in literature

Al Microheater and Ni Temperature Sensor Set based-on Photolithography with Closed-Loop Control

This article proposes the development of a new low-cost microheater and temperature sensor set. It was developed based on Micro-Electro-Mechanical Systems (MEMS) which based on photolithography technique and lift-off technique. Thin film of aluminum was utilized as microheater and encompassed nickel temperature sensor inside in order to decrease response time of the desired temperature. To control the various temperatures correctly, closed-loop feedback control based on PI-controller was adapted into control circuit system. Microcontroller was implemented to control and observe the responses of temperature between 40°C and 120°C. Simulation and experimental results are also presented

solenoid inductors

Surface micromachined arch-shape on-chip 3-