High Q-factor CMOS-MEMS inductor

This study investigates a high Q-factor spiral inductor fabricated by the CMOS (complementary metal oxide semiconductor) process and a post-process. The spiral inductor is manufactured on silicon substrate using the 0.35 m CMOS process. In order to reduce the substrate loss and enhance the Q-factor of the inductor, silicon substrate under the inductor is removed using a post-process. The post-process uses RIE (reactive ion etching) to etch the sacrificial layer of silicon dioxide, and then TMAH (tetra methyl ammonium hydroxide) is employed to remove the underlying silicon substrate and obtain the suspended spiral inductor. The advantage of the post process is compatible with the CMOS process. The Agilent 8510C network analyzer and a Cascade probe station are used to measure the performances of the spiral inductor. Experiments indicate that the spiral inductor has a Q-factor of 15 at 11 GHz, an inductance of 4 nH at 25.5 GHz and a self-resonance frequency of about 27 GHz

Design Of Mems Inductor And Varactor For Low Noise Voltage Controlled Oscillators

Micro-Electro-Mechanical-Systems (MEMS) technology has been used to develop high quality factor (Q), low cost and low power consumption circuit blocks in RF communication systems. This research focuses on the design of high-performance MEMS inductor and varactor for use in Complementary Metal-Oxide Semiconductor (CMOS) voltage controlled oscillators (VCO) operating at 2.4 GHz. The air suspended inductor has been designed using MEMS technology to reduce the resistive loss and the substrate loss. Lowresistivity material has been used. A MEMS two-gap tunable capacitor, using two parallel plates (one fixed and one movable), has been designed. The capacitance can be varied by applying low voltage to the movable plate. The pull-in voltage has been optimized to achieve low phase noise, low power consumption, and a wide frequency tuning range for VCO. The MEMS inductor and MEMS capacitor have been used in the design of VCO. The inductor has been modeled with a physical, equivalent two-port model known as Yue's model to compute the parameters and Q factor of the inductor. The designed inductor has a Q factor of 27 and the inductance is about 2.87nH at 2.4GHz. The capacitor has a value of 2.04 pF capacitance and Q factor of 40 at 2.4 GHz. The proposed MEMS inductor and varactor has been used in simulation of VCO to determine the effect of high Q factor on the VCO phase noise. The active part of the circuit has been designed using CMOS. Based on the simulation, low phase noise and low power consumption have been obtained simultaneously. The results of - 117.7 dBc/Hz at 1 00 KHz and 11m W have been achieved for phase noise and power consumption of VCO respectively

Design and simulation of high Q MEMS LC-tank for oscillators

This research focuses on the design of a high-performance MEMS LC-tank using a high Q MEMS inductor and capacitor. A two different gap varactor has been used to avoid pull-in voltage at 2.4 GHz. The layout has been done by CoventorWare software. The DC voltage is 2.5 v, which is applied to the plates and results of 2.04 pF could be gained. The Q factor of the varactor is computed at about 557.27, which is good enough to make a low-phase noise VCO. A hollow spiral inductor with a silicon base substrate for compatibility with CMOS technology has been designed. The Greenhouse equation has been used to obtain the dimensions of the inductor. A suspended inductor has been implemented to avoid substrate coupling. The simulation has been done by CoventorWare. The Q factor of the inductor has been calculated using Yue's model. The resultant values of inductance and the Q factor at 2.4 GHz, are 2.89 nH and 27, respectively, which are in good agreement with the results of theoretical computation. The results were verified with the well-documented literature

Manufacture and Characterization of High Q-Factor Inductors Based on CMOS-MEMS Techniques

A high Q-factor (quality-factor) spiral inductor fabricated by the CMOS (complementary metal oxide semiconductor) process and a post-process was investigated. The spiral inductor is manufactured on a silicon substrate. A post-process is used to remove the underlying silicon substrate in order to reduce the substrate loss and to enhance the Q-factor of the inductor. The post-process adopts RIE (reactive ion etching) to etch the sacrificial oxide layer, and then TMAH (tetramethylammonium hydroxide) is employed to remove the silicon substrate for obtaining the suspended spiral inductor. The advantage of this post-processing method is its compatibility with the CMOS process. The performance of the spiral inductor is measured by an Agilent 8510C network analyzer and a Cascade probe station. Experimental results show that the Q-factor and inductance of the spiral inductor are 15 at 15 GHz and 1.8 nH at 1 GHz, respectively

Implantable parylene-based wireless intraocular pressure sensor

This paper presents a novel implantable, wireless, passive pressure sensor for ophthalmic applications. Two sensor designs incorporating surface-micromachined variable capacitor and variable capacitor/inductor are implemented to realize the pressure sensitive components. The sensor is monolithically microfabricated using parylene as a biocompatible structural material in a suitable form factor for increased ease of intraocular implantation. Pressure responses of the microsensor are characterized on-chip to demonstrate its high pressure sensitivity (> 7000 ppm/mmHg) with mmHg level resolution. An in vivo animal study verifies the biostability of the sensor implant in the intraocular environment after more than 150 days. This sensor will ultimately be implanted at the pars plana or iris of the eye to fulfill continuous intraocular pressure (IOP) monitoring in glaucoma patients

Q-enhanced fold-and-bond MEMS inductors

This work presents a novel coil fabrication technology to enhance quality factor (Q factor) of microfabricated inductors for implanted medical wireless sensing and data/power transfer applications. Using parylene as a flexible thin-film device substrate, a post-microfabrication substrate folding-and-bonding method is developed to effectively increase the metal thickness of the surface-micromachined inductors, resulting in their lower self-resistance so their higher quality factor. One-fold-and-bond coils are successfully demonstrated as an example to verify the feasibility of the fabrication technology with measurement results in good agreements with device simulation. Depending on target specifications, multiple substrate folding-and-bonding can be extensively implemented to facilitate further improved electrical characteristics of the coils from single fabrication batch. Such Q-enhanced inductors can be broadly utilized with great potentials in flexible integrated wireless devices/systems for intraocular prostheses and other biomedical implants

Microfabricated Implantable Parylene-Based Wireless Passive Intraocular Pressure Sensors

This paper presents an implantable parylene-based wireless pressure sensor for biomedical pressure sensing applications specifically designed for continuous intraocular pressure (IOP) monitoring in glaucoma patients. It has an electrical LC tank resonant circuit formed by an integrated capacitor and an inductor coil to facilitate passive wireless sensing using an external interrogating coil connected to a readout unit. Two surface-micromachined sensor designs incorporating variable capacitor and variable capacitor/inductor resonant circuits have been implemented to realize the pressure-sensitive components. The sensor is monolithically microfabricated by exploiting parylene as a biocompatible structural material in a suitable form factor for minimally invasive intraocular implantation. Pressure responses of the microsensor have been characterized to demonstrate its high pressure sensitivity (> 7000 ppm/mmHg) in both sensor designs, which confirms the feasibility of pressure sensing with smaller than 1 mmHg of resolution for practical biomedical applications. A six-month animal study verifies the in vivo bioefficacy and biostability of the implant in the intraocular environment with no surgical or postoperative complications. Preliminary ex vivo experimental results verify the IOP sensing feasibility of such device. This sensor will ultimately be implanted at the pars plana or on the iris of the eye to fulfill continuous, convenient, direct, and faithful IOP monitoring

Fabrication of 3D Air-core MEMS Inductors for High Frequency Power Electronic Applications

AbstractWe report a fabrication technology for 3D air-core inductors for small footprint and very-high-frequency power conversions. Our process is scalable and highly generic for fabricating inductors with a wide range of geometries and core shapes. We demonstrate spiral, solenoid, and toroidal inductors, a toroidal transformer and inductor with advanced geometries that cannot be produced by wire winding technology. The inductors are embedded in a silicon substrate and consist of through-silicon vias and suspended windings. The inductors fabricated with 20 and 25 turns and 280-350 μm heights on 4-16 mm2 footprints have an inductance from 34.2 to 44.6 nH and a quality factor from 10 to 13 at frequencies ranging from 30 to 72 MHz. The air-core inductors show threefold lower parasitic capacitance and up to a 140% higher-quality factor and a 230% higher-operation frequency than silicon-core inductors. A 33 MHz boost converter mounted with an air-core toroidal inductor achieves an efficiency of 68.2%, which is better than converters mounted with a Si-core inductor (64.1%). Our inductors show good thermal cycling stability, and they are mechanically stable after vibration and 2-m-drop tests.</jats:p