Seong-Su Park

Fabrication of semiconductor optical switch module using laser welding technique

The 4/spl times/4, 1/spl times/2, and 1/spl times/4 semiconductor optic-switch modules for 1550 nm optical communication systems were fabricated by using the laser welding technique based on the 30-pin butterfly package. For better coupling efficiency between a switch chip and an optical fiber, tapered fibers of 10-15 /spl mu/m lens radius were used to provide the coupling efficiency up to 60%. The lens to lens distance of the assembled tapered fiber array was controlled within /spl plusmn/1.0 /spl mu/m. A laser hammering technique was introduced to adjust the radial shift, which was critical to obtain comparable optical coupling efficiencies from all the channels at the same time. The fabricated optical switch modules showed good thermal stability, with less than 5% degradation after a 200 thermal cycling. The transmission characteristics of the 4/spl times/4 switch module showed good sensitivities, providing error free transmissions below -30 dBm for all the switching paths. The dynamic ranges for the 4/spl times/4 and 1/spl times/2 switch modules were about 8 dB for a 3 dB penalty and about 17 dB for a 2 dB penalty, respectively.

Low-voltage, Low-power and High-gain Mixer Based on Unbalanced Mixer Cell

A low-voltage, low-power and high-gain mixer core structure based on the unbalanced mixer cell or square-law mixer cell for 5GHz wireless LAN applications is presented in this paper. To reduce power dissipation, a new single-balanced mixer was proposed which operates under a low supply voltage and with the current reuse technique. The circuit was designed with a 0.18mum CMOS process. The designed down-conversion mixer has a maximum conversion gain of 22dB with LO power of -2.5dBm. However, with small LO power of -10dBm, -15dBm and -20dBm the mixer shows a moderate conversion gain of 14.9dB, 10dB and 5.1dB, and an input P1dB of -14dBm, -9.5dBm and -4.5dBm, and an input IP3 of -4.5dBm, 0dBm and 5dBm, respectively. The designed mixer including a bias circuit consumes 1.2mA under a 1.5V supply voltage. The chip size including pads is 0.77mm times 0.81mm

Embedded passive components in MCM-D for RF applications

The increasing demand for high density packaging was the driving forces to the development of MCM-D technology. Most of these development efforts have been focused on high performance digital circuits. However, recently there is a great need for mixed mode circuits with a combination of digital, analog and microwave devices. Mixed mode modules often have a large number of passive components that are connected to a small number of active devices. Integration of passive components into the high density MCM substrate becomes desirable to further reduce cost, size, and weight of electronic systems while improving their performance and reliability. So, we developed the embedded passive components (including resistors, capacitors, inductors) for RF module in MCM-D substrate. This paper will describe the manufacturing process of MCM-D substrate, the method for integrating passive components in MCM-D substrate and electrical performance test.

High frequency modeling for 10 Gbps DFB laser diode module packaging

In packaging the laser diode several electrical requirements must be satisfied. The conventional packaging method which consists of transmission line, matching resistor and wire bonding interconnect showed good result for the modulation bandwidth requirement of greater than 10 GHz. However the return loss requirement was not content with less than -10 dB. To analyze the effects of package parasitics on return loss, we proposed a small signal circuit model of a laser diode module. From the small signal measurement data, we obtained the small signal circuit model of the laser diode for each bias current, which contains package parasitics and intrinsic laser diode characteristics. Considering both the intrinsic laser diode characteristics and total parasitic effects of the packaged module, the overall frequency response of the laser diode module was simulated and compared to the experimental results. The simulation results on the small signal modulation bandwidth and return loss showed a good agreement with measurements. However, the return loss does not meet the requirement for 10 Gbps laser diode module. Therefore, the wire bonding effect on the return loss was analyzed. The characteristics of wire bonding inductance which affect the return loss were simulated using an interconnect analysis program. As a result, shorter wire bonding length would be the best step to reduce the package induced inductance.

Effects of O/sub 2//C/sub 2/F/sub 6/ plasma descum with RF cleaning on via formation in MCM-D substrate using photosensitive BCB

In this paper, we present the effect of plasma descum by O/sub 2//C/sub 2/F/sub 6/ gas mixture on the via formation of photosensitive BCB layer and compare it with that of RF cleaning. Test vehicle was fabricated on Si wafer with Cu/photosensitive BCB layer structure and ECR-CVD system was used to descum the via. Residues at via bottom after the descum process were investigated by AES (auger electron microscope) and SEM (scanning electron microscope). It is shown in this work that O/sub 2//C/sub 2/F/sub 6/ plasma etching and the RF cleaning are effective for organic C, native C respectively, therefore the via descum by a combination of plasma etching with O/sub 2//C/sub 2/F/sub 6/ gas mixture and RF cleaning can efficiently remove the via residues.

Reliability considerations of laser diodes for optical communication system application

The purpose of this paper is to propose a reliability parameter of laser diodes for optical communication system applications. Based on the alarm function in optical communication systems, we have developed a reliability parameter; /spl rho//sub a/(=/spl eta//sub a///spl eta//sub 0/.Ith/sub a//Ith/sub 0/)/spl ges/1.5, which is more applicable to estimate reliability projections and to design LD modules for optical communication systems.

1.5 V ultrawide-band GaAs monolithic amplifier for portable wireless LAN and satellite communication applications

A 1.5 V operating GaAs 2/spl sim/9 GHz ultrawide-band MMIC amplifier for portable wireless LAN, microwave link and satellite communication applications has been developed. This amplifier has 16/spl plusmn/1 dB gain and more than 10 dB input and output return loss in the 2/spl sim/9 GHz frequency range with 118 mA operating current. Measured 1-dB compression power is 13 dBm at 0 dBm input power and minimum noise figure is 4.8 dB. When operated at 3 V and 128 mA, this amplifier has up to 18/spl plusmn/1 dB gain, 18 dBm 1-dB compression power, more than 10 dB return loss and 4.9 dB minimum noise figure.

The effect of via size on fine pitch and high density solder bumps for wafer level packaging

This study investigated how the shapes of high density electroplated bump and reflowed bumps depend on via size. The solder bump was fabricated by subsequent processes as follows. After sputtering a Ti/Cu seed layer on a 5-inch Si-wafer, a thick photoresist for via formation was obtained by multi-coating, and vias with various diameters were defined by a conventional photolithography technique using a contact aligner with an I-line source. After via formation, eutectic solder bumps were electroplated. After reflow, the reflowed bump diameters at the bottom were unchanged compared with the electroplated diameters. The electroplated bump and reflowed bump shapes, however, depended significantly on the via size. The heights of the electroplated bumps and reflowed bumps increased with a larger via, while the aspect ratio of bumps decreased. To obtain high density bumps, the bump pitch was decreased so that the nearest bumps touched. The touching between the nearest bumps occurred during the over-plating procedure but not during the reflowing procedure because the mushroom diameter formed by over-plating was larger than the reflowed bump diameter. This study demonstrated that an arrangement in zig-zag rows is effective in realizing flip chip interconnect bumps with both a high density and high aspect ratio.

Fuel economy validation of the smart microhybrid system for used cars

We developed a smart microhybrid system for used cars to improve fuel efficiency via the OBD-II interface. The proposed smart microhybrid system can accurately measure the amount of fuel that is saved by stopping engine idling and estimates the amount of fuel that is consumed when the engine begins to start. It automatically determines when is optimal to stop or start the engine using various driving status. The system was implemented and tested in a used car. Experimental results show that it outperforms conventional cars not equipped with the smart microhybrid system in fuel economy. We will massively reduce CO2 by using smart microhybrid systems and prove the possibility of the CDM (clean development mechanism) project.

A Dual-Channel 6b 1GS/s 0.18um CMOS ADC for Ultra Wide-Band Communication Systems

This work proposes a dual-channel 6b 1GS/s ADC for ultra wide-band communication system applications. The proposed ADC based on a 6b interpolated flash architecture employs wide-band open-loop track-and-hold amplifiers, comparators with a wide-range differential difference preamplifier, latches with reduced kickback noise, on-chip CMOS references, and digital bubble code correction circuits to optimize power, chip area, and accuracy at 1GS/s. The ADC implemented in a 0.18mum 1P6M CMOS technology shows a signal-to-noise-and-distortion ratio of 30dB and a spurious-free dynamic range of 39dB at 1GS/s. The measured differential and integral nonlinearities of the prototype ADC are within 1.00LSB and 1.25LSB, respectively. The dual-channel ADC has an active area of 4.0mm2 and consumes 594mW at 1GS/s and 1.8V