In-Ho Jeong

High-performance air-gap transmission lines and inductors for millimeter-wave applications

The air-gap transmission lines and inductors are developed by new multilayer process. The developed transmission lines are air-gap coaxial line, air-gap strip line, air-gap coplanar waveguides (CPW), and air-gap buried microstrip line (BMSL). The air-gap transmission lines show very low signal loss and very high isolation performances. The transmission line loss of the coaxial line is less than 0.08 dB/mm up to 40 GHz. Those of the CPW, strip line and BMSL are about 0.07, 0.15, and 0.13 dB/mm, respectively. The isolation characteristics of the coaxial line and BMSL are measured. In case of the coaxial line with 2-mm coupling length and 60-μm distance between signal lines, the coupling is less than –52 dB up to 40 GHz. In case of the BMSL with the same conditions, the coupling is less than –43 dB. Therefore, the air-gap transmission line is very suitable structure for high performance and high-density RF application. Additionally, the air-gap inductors are monolithically fabricated using the same process of the transmission line. The fabricated inductors have very high quality factors, the maximum factor of 1.46-nH air-gap inductor is about 130. Using the developed multilayer process, we can realize various types of air-gap transmission lines (coaxial line, CPW, strip line and BMSL) and air-gap inductors simultaneously.

Monolithic implementation of coaxial line on silicon substrate

A coaxial line has been monolithically fabricated on a silicon substrate using benzocylobutene (BCB) for dielectric spacers. Because of its closed structure, it is an effective interconnection method to reduce parasitic radiation and the coupling effect. The fabricated coaxial line with 2 mm length has high isolation (<-60 dB), low attenuation (<0.08 dB/mm) and low return loss (<-32 dB) in the range of 1-20 GHz. It can be easily fabricated using standard silicon IC technologies, and requires no wafer thinning and backside processing. In view of cost performance and integration density, the coaxial line on low-resistivity silicon is shown to be suitable for RF interconnect and multichip module (MCM) package applications.

System in a package solution for RF receiver with SAW filter integration

An RF receiver module including a SAW filter in a package has been developed for providing a system in a package (SIP) solution. The most significant feature for the receiver module is that the RF SAW (surface acoustic wave) filter is integrated within the package. A typical silicon substate with thick oxide on top (/spl sim/25 /spl mu/m) made it possible to implement the different technologies such as GaAs MMIC and SAW filter on a single substate. MCM-D technology using a silicon substrate in this paper shows the proper solution for a SIP. RF performance and basic circuit components such as inductors, capacitors, resistors and transmission lines are developed. To verify the application of a silicon substrate to a system, an RF receiver module having dual band/tri-mode functions (CDMA, AMPS, and PCS) is implemented on a silicon substrate. A low noise amplifier, RF SAW filter and mixer are integrated on a specialized silicon substrate and show 2.4/spl sim/3 dB NF and 27/spl sim/28 dB gain for PCS (1840/spl sim/1870 MHz) and CDMA (869/spl sim/894 MHz), respectively.

Monolithic implementation of air-buried microstrip lines for high-density microwave and millimeter wave ICs

This paper introduces a new type of monolithic transmission line structure for high-density microwave and millimeter wave integrated circuits. An air-buried microstrip line (ABMSL) has been monolithically fabricated on glass substrates using a new multi-layer process. The ABMSL has the advantages of low insertion loss and high isolation between transmission lines compared to conventional planar transmission lines such as microstrip lines and coplanar waveguides (CPWs), because of its geometric structure that has air as a dielectric medium and ground conductor walls formed to surround the strip conductor. Over a high frequency range (from 5 GHz to 40 GHz), the ABMSL has very low insertion loss below 0.08 dB/mm. The isolation between two ABMSLs that have 2 mm coupling length and are separated by a 60 /spl mu/m distance is less than -43 dB.

Ka-band branch line coupler using high-performance air-buried microstrip lines

In this paper, a branch line coupler using airburied microstrip lines (ABMSLs) has been monolithically fabricated for millimeter-wave applications. Because the ABMSL structure employs air-dielectric medium and ground conductor walls surrounding strip signal line, it is very effective in reducing a dielectric loss, as well as parasitic coupling between close transmission lines over high frequency range. The fabricated branch line coupler shows a coupling and transmission loss of 3.6 dB and 3.9 dB, respectively at the center frequency of 29GHz. In the frequency range from 26GHz to 32GHz (20% bandwidth), it exhibits a return loss of better than 15 dB and isolation of better than 14 dB.

High performance air gap transmission lines for millimeter wave applications

The air gap transmission lines are developed by a new multi-layer process. The developed transmission lines are air gap coaxial line, air gap strip line and air gap BMSL (buried microstrip line). Air gap transmission lines show very low signal loss and very high isolation performances. The transmission line loss of the coaxial line is less than 0.08 dB/mm up to 40 GHz. Those of the strip line and the BMSL are about 0.15 dB/mm and 0.13 dB/mm, respectively. Reduction of the parasitic coupling between signal lines is very important in high-density MICs and MMICs. The isolation characteristics of the coaxial line and the BMSL are measured. In case of coaxial lines with 2 mm coupling length and 60 /spl mu/m distance between signal lines, the coupling is less than -52 dB up to 40 GHz. Under the same conditions, the coupling of the BMSL is less than -43 dB. Therefore the air gap transmission lines are very suitable structures for high performance and high-density RF applications.

Low-Loss and High-Frequency Interconnection Technology on Membrane Supported by Porous Silicon Post

A coplanar waveguide (CPW) has been fabricated on a 40 µm-thick porous silicon layer and the measured maximum available gain is -0.59 dB/mm at 40 GHz. The coplanar waveguide is then released in the air by etching the porous silicon layer under the signal line, which is supported at each end by porous silicon posts. The porous silicon post is surrounded by silicon sidewalls and a dielectric layer to protect it from the etchant. The porous silicon layer can be etched in 0.25 wt% NaOH solution with the rate of more than 2.5 µm/min but metal patterns are not attacked significantly by the etchant when there is no protection mask for them. A 5-mm-long coplanar waveguide has a maximum available gain of -1.32 dB at 40 GHz and a return loss of less than -16 dB up to 40 GHz. A maximum available gain of -0.2 dB/mm at 40 GHz is obtained when the gap between the membrane and silicon substrate is 100 µm. Because of its low-loss characteristic, the coplanar waveguide can be used for RF interconnection and multichip module package applications.