Jun Bo Yoon

CMOS-compatible surface-micromachined suspended-spiral inductors for multi-GHz silicon RF ICs

Fully CMOS-compatible, highly suspended spiral inductors have been designed and fabricated on standard silicon substrates (1/spl sim/30 /spl Omega//spl middot/cm in resistivity) by surface micromachining technology (no substrate etch involved). The RF characteristics of the fabricated inductors have been measured and their equivalent circuit parameters have been extracted using a conventional lumped-element model. We have achieved a high peak Q-factor of 70 at 6 GHz with inductance of 1.38 nH (at 1 GHz) and a self-resonant frequency of over 20 GHz. To the best of our knowledge, this is the highest Q-factor ever reported on standard silicon substrates. This work has demonstrated that the proposed microelectromechanical systems (MEMS) inductors can be a viable technology option to meet the todays strong demands on high-Q on-chip inductors for multi-GHz silicon RF ICs.

Surface micromachined solenoid on-Si and on-glass inductors for RF applications

RF performance of surface micromachined solenoid on-chip inductors fabricated on a standard silicon substrate (10 /spl Omega//spl middot/cm) has been investigated and the results are compared with the same inductors on glass. The solenoid inductor on Si with a 15-/spl mu/m thick insulating layer achieves peak quality (Q-) factor of 16.7 at 2.4 GHz with inductance of 2.67 nH. This peak Q-factor is about two-thirds of that of the same inductor fabricated on glass. The highest performance has been obtained from the narrowest-pitched on-glass inductor, which shows inductance of 2.3 nH, peak Q-factor of 25.1 at 8.4 GHz, and spatial inductance density of 30 nH/mm/sup 2/. Both on-Si and on-glass inductors have been modeled by lumped circuits, and the geometrical dependence of the inductance and Q-factor have been investigated as well.

Fully integrated low phase-noise VCOs with on-chip MEMS inductors

We present fully integrated high-performance voltage-controlled oscillators (VCOs) with on-chip microelectromechanical system (MEMS) inductors for the first time. MEMS inductors have been realized from the unique CMOS-compatible MEMS process that we have developed to provide suspended thick metal structures for high-quality (Q) factors. Fully integrated CMOS VCOs have been fabricated by monolithically integrating these MEMS inductors on the top of the CMOS active circuits realized by the TSMC 0.18-/spl mu/m mixed-mode CMOS process. Low phase noise has been achieved as -124 and -117 dBc/Hz at 300-kHz offset from carrier frequencies of 1 and 2.6 GHz, respectively, in the fabricated single-chip VCOs.

A high fill-factor infrared bolometer using micromachined multilevel electrothermal structures

A high fill-factor uncooled infrared (IR) bolometer has been fabricated by using thin-film titanium resistors sandwiched in a surface-micromachined silicon oxinitride membrane (50 /spl mu/m/spl times/50 /spl mu/m). This bolometer is realized in multilevel electrothermal structures with a fill-factor over 92%. From the multilevel structure, thermal isolation can be independently optimized without sacrificing IR absorbing area. Initial measurements show a thermal time constant of 12 ms, a responsivity of 1600 V/W, and a detectivity (D*) of 5/spl times/10/sup 8/ cm/spl radic/Hz/W.

Monolithic Fabrication of Electroplated Solenoid Inductors Using Three-Dimensional Photolithography of a Thick Photoresist

A novel and high-yield fabrication process has been devised for monolithic integration of solenoid inductors. In order to simplify the fabrication steps, we decompose the solenoid inductor into two parts, bottom conductor lines and air bridges. The air bridge is formed as a single body during a single electroplating step. This single-step fabrication of the air bridges is possible by forming a three-dimensional (3D) photoresist mold using multiple exposures with varying exposure depths, followed by a single development step, which realizes the 3D latent image of the unexposed volume in the photoresist. We have successfully fabricated solenoid inductors with and without a magnetic core using this process. This process is easy and simple, so that one can significantly improve the fabrication yield over that achieved by conventional methods. Also, this process has good compatibility with the integrated circuit (IC) process owing to a low process temperature (<120°C) and the monolithic feature.

Monolithic integration of 3-D electroplated microstructures with unlimited number of levels using planarization with a sacrificial metallic mold (PSMM)

A new monolithic integration method for 3-D electroplated microstructures of unlimited number of levels has been developed using unique planarization with a sacrificial metallic mold (PSMM). Contrary to the conventional electroplating mold of photoresist or polyimide, the sacrificial metallic mold (SMM) is used for multiple functions: a sacrificial layer, a planarization layer, and a seed layer for the next-level electroplating as well. We have successfully demonstrated various three-level metallic microstructures, such as levitated on-chip inductors, micro-bridges, micro-cantilevers, and micro-mirrors. The RF performance of the fabricated inductor has shown excellent results of 5 nH, Q-factor of 50 at 5 GHz on glass. This method is very simple, highly adaptable, and IC-compatible, so that it can be used as a versatile tool to integrate various 3-D metallic microstructures in multiple levels.

3-D lithography and metal surface micromachining for RF and microwave MEMS

A new metal surface micromachining technology utilizing 3-D lithography, electroplating, and mechanical polishing has been developed to fabricate arbitrary 3-D metal microstructures as post-IC processes at low temperature below 120/spl deg/C. Using this technology, various highly-suspended 3-D microstructures have been successfully demonstrated for RF and microwave MEMS applications. We have fabricated spiral inductors suspended 100 /spl mu/m over the substrate, coplanar waveguides suspended 50 /spl mu/m over the substrate, and complicated micro-coaxial lines which have 50 /spl mu/m-suspended center signal lines surrounded by ground shields of 100 /spl mu/m in height.

Hermetically sealed inductor-capacitor (LC) resonator for remote pressure monitoring

This paper reports an integrated inductor-capacitor (LC) resonator structure fabricated using bulk micromachining and anodic bonding technologies. In this resonator structure, pressure change monitored by a capacitive pressure sensor results in the change of resonance frequency. The resonance frequency shift is detected by inductive coupling from an external transmission coil; therefore, pressure can be monitored remotely using the passive LC resonator. The fabricated device size measures 3 mm×3 mm×0.6 mm, and pressure responsivity has been estimated to be 2 MHz/mmHg. This micromachined, hermetically sealed structure is suitable for biomedical applications such as intraocular, cardiovascular and brain pressure monitoring.

A low-voltage two-axis electromagnetically actuated micromirror with bulk silicon mirror plates and torsion bars

In this paper, a new micromirror structure has been proposed and fabricated. The proposed micromirror is electromagnetically actuated along two-axis at low voltage using an external magnetic field. The mirror plates and torsion bars are made of bulk silicon and the actuation coils are made of electroplated copper. The maximum deflection angles have been measured as /spl plusmn/4.35/spl deg/ for x-axis actuation and /spl plusmn/15.7/spl deg/ for y-axis actuation. The actuation voltages are below 4.2 V for x-axis actuation and 1.76 V for y-axis actuation, respectively.

A disposable DNA sample preparation microfluidic chip for nucleic acid probe assay

A new DNA sample preparation microfluidic chip for Nucleic Acid (NA) probe assay has been proposed. The proposed microfluidic chip is composed of three parts: microfilter, micromixer and DNA purification chip. We have fabricated a microsieve type filter with an array of 2.2 /spl mu/m diameter holes. We have also demonstrated the mixing can be successfully achieved for low Reynolds number below 50 by using the fabricated micromixer. The fabricated DNA purification chip has shown a binding capacity of 15 ng/cm/sup 2/ and a minimum extractable input concentration of 100 copies/200 /spl mu/L. The proposed microfluidic chip can be applied for low-cost, disposable sample preparation of NA probe assays.