This paper presents on-chip characterization of electrostatic discharge (ESD) impacts applied on the Si-substrate backside of a flip-chip mounted integrated circuit (FC-IC) chip. An FC-IC chip has an open backside and there is a threat of reliability problems and malfunctions caused by the backside ESD. We prepared a test FC-IC chip and measured Si-substrate voltage fluctuations on its frontside by an on-chip monitor (OCM) circuit. The voltage surges as large as 200mV were observed on the frontside when a 200-V ESD gun was irradiated through a 5kΩ contact resistor on the backside of a 350μm thick Si substrate. The distribution of voltage heights was experimentally measured at 20 on-chip locations among thinned Si substrates up to 40μm, and also explained in full-system level simulation of backside ESD impacts with the equivalent models of ESD-gun operation and FC-IC chip assembly.

We developed a high-frequency and integrated design based on a flip-chip interconnection technique (Hi-FIT) as a wire-free interconnection technique that provides a high modulation bandwidth. The Hi-FIT can be applied to various high-speed (>100 Gbaud) optical devices. The Hi-FIT EA-DFB laser module has a 3-dB bandwidth of 59 GHz. And with a 4-intensity-level pulse amplitude modulation (PAM) operation at 107 Gbaud, we obtained a bit-error rate (BER) of less than 3.8×10-3, which is an error-free condition, by using a 7%-overhead (OH) hard-decision forward error correction (HD-FEC) code, even after a 10-km SMF transmission. The 3-dB bandwidth of the Hi-FIT employing an InP-MZM sub-assembly was more than 67 GHz, which was the limit of our measuring instrument. We also demonstrated a 120-Gbaud rate IQ modulation.

This paper discusses a pulse generator implemented by CMOS flipped on a glass substrate aiming at low power applications with low duty cycle. The pulse generator is theoretically possible to generate a pulse at a frequency near and beyond Fmax. It also features a quick starting time and zero stand-by power. By using a simplified circuit model, analytical expressions for Q factor, energy conversion efficiency, output energy, and oscillation frequency of the pulse generator are derived. Pulse generator prototypes are designed on a 0.18 μm CMOS chip flipped over a transmission line resonator on a glass substrate. Measurement results of two different prototypes confirm the feasibility of the proposed circuit and the analytical model.

In this paper, we designed and fabricated large scale micro-light-emitting-diode (LED) arrays and silicon driver for single chip device for realizing as prototypes of heterogeneous optoelectronic integrated circuits (OEICs). The large scale micro-LED arrays were separated by a dry etching method from mesa structure to 16,384 pixels of 128 128, each with a size of 15 µm in radius. Silicon driver was designed the additional bonding pad on each driving transistor for bonding with micro-LED arrays. Fabricated micro-LED arrays and driver were flip-chip bonded using anisotropic conductive adhesive.

A 76-GHz Gunn voltage-controlled oscillator (VCO) with a high output power and a wide tuning-frequency range was fabricated by optimizing VCO circuits and using laser micromachining. The tuning-frequency range of the fabricated Gunn VCO was more than two times higher than that attained in our previous experiments by optimizing VCO circuits. The VCO attained a tuning-frequency range of 493 MHz, output power variation of 1.0 dB, and tuning-frequency linearity of 6.1% over a tuning-voltage range from 0 to 10 V. Its power consumption was 2.0 W at operation voltage of 3.6 V. And it measured output power was 13.3 dBm with DC-RF conversion efficiency of 1.0% at 76.5 GHz. Moreover, under fundamental-mode operation, it achieved low phase noise of -107.8 dBc/Hz at an offset frequency of 1 MHz. Since laser micromachining was used in fabricating the Gunn VCO, the reproducibility of its RF performance was improved.

Recent advances in 77-GHz MMIC module design techniques for automotive radar applications are reviewed in this paper. The target of R&D activities is moving from high performance to low cost, mass production, high-yield manufacturing and testing. To meet the stringent requirements, millimeter-wave module design techniques have made significant progress especially in packaging, bonding, and making interface with other modules. In addition, millimeter-wave semiconductor devices and MMICs have made remarkable improvements for low cost and mass production. In this paper, the topics focusing on millimeter-wave semiconductor devices and 77-GHz MMICs are reviewed first. Then the recent R&D results on 77-GHz MMIC module design techniques are introduced, showing the technical trend of packaging, bonding, and making interface with other modules for millimeter-wave, highly-integrated, low-cost MMIC modules. Finally, the existing and future module design issues for automotive radar applications are discussed.

We developed a new millimeter-wave plastic chip size package (CSP) to operate up to 100 GHz by using a thin-film substrate. It has a flip-chip distributed amplifier with inverted microstrip lines and the amplifier has a bandwidth of beyond 110 GHz. The transmission line on the substrate consists of grounded coplanar waveguides that yield low insertion loss and high isolation characteristics in coupled lines even in mold resin in comparison with conventional microstrip lines. The CSP amplifier achieved a gain of 7.8 dB, a 3-dB bandwidth of 97 GHz, and operated up to 100 GHz. To the best of our knowledge, this value is the highest operating frequency reported to date for a distributed amplifier sealed in a plastic CSP. We also investigated the transmission characteristics of lead-free solder bumps through experiments by assemblying CSPs on printed circuit boards and modeling them so that we could design the packages accurately.

A GaAs HEMT with flip-chip interconnections using a suitable transmission line has been developed. The underfill resin, which was not used for the conventional flip-chip interconnection structure, was adopted between GaAs chip and assembly substrate to obtain high reliability. The underfill resin is effective in relaxing the thermal stress between the chip and the substrate and in encapsulating the chip. There are various possible ground current paths for the GaAs chip in the structure with flip-chip interconnections. An actual ground current path is determined depending on the transmission line type for the chip. For an active device, it is important to utilize an assembly structure capable of realizing excellent high-frequency characteristics. In addition, each transmission line for the chip has its own transmission characterizations such as characteristic impedance. Therefore, it is necessary to choose a suitable transmission line for the chip. We evaluated the high-frequency characteristics of the HEMT test element groups (TEGs) with flip-chip interconnection for three types of transmission lines: with a microstrip line (MSL), with a coplanar waveguide (CPW), and with an inverted microstrip line (IMSL). All three types of TEGs had similar values of a maximum available power gain (MAG) at 30 GHz. However, it was found that the IMSL-type TEG, which had superior characteristics in high-frequency ranges of more than 30 GHz, is the most suitable type. The IMSL-type TEG had an MAG of 10.02 dB and a Rollett stability factor K of 1.20 at 30 GHz.

In the present GHz-clock high-density LSI, a design of signal lines is getting so critical that the transmission line analysis should be introduced to signal line design. This leads to the complex design of line structure and i/o drivers including impedance matching. Our target is to implement a system-in-package (SiP) for software-defined-radio (SDR). The SiP operates up to 10 GHz, and requires a compact and high-density packaging technology with a simple signal wiring design. In this paper, we propose a new concept of 3-D multilayer-stacked SiP. The new 3-D packaging concept includes (1) design guideline for interconnection lengths, (2) bridging register circuits in LSI chips, (3) flip-chip microbump bonding technology of chips onto system-buildup printed wiring boards (PWB), (4) multilayer-stacked 3-D package of several sets of chips and PWB, and (5) 100-µm-diameter bumps at peripheral region of PWB as vertical via-bump bus lines. A critical interconnect length, in which interconnect wiring is treated as a conventional RC line, is discussed for wiring design. Both wiring lengths in LSI chips and that among chips corresponding to total thickness of vertical bus lines are designed to be shorter than the critical length. The key points of the 3-D package for GHz signal transfer are a delay guarantee due to limitation of line length and separation between local lines in a chip and a bus line among chips.

This paper describes a new millimeter-wave hybrid integrated circuit (HIC) technology which applies a thin film multi-layered dielectric substrate and flip-chip bonding technology employing stud bump bonding (SBB). We have previously proposed and demonstrated a novel HIC structure, named millimeter-wave flip-chip IC, (MFIC), applying an excellent dielectric material of benzocyclobutene (BCB) thin film and flip-chip bonding. In this paper, an advanced thin film multi-layer process using non-photosensitive BCB was newly developed. Characteristics of the transmission lines and the built-in MIM capacitor within the multi-layered structure were discussed. Furthermore, stud bump bonding was newly adapted to the MFIC as a flip-chip method, and the millimeter-wave characteristics of the bumps were examined. Using these technologies, we demonstrate characteristics of a miniaturized 25 GHz down converter MFIC. Our newly proposed HIC structure enabled us to bring down chip size to less than 1/3 of our conventional structure. Finally, we discuss future possibilities for high performance multi-chip-modules (MCMs) using SBB technology as a further improved HIC for compact millimeter-wave radio equipment.

The flip-chip structure for millimeter-wave MMICs has been investigated to obtain high performance and high reliability. In our approach, an air gap between the MMIC and the alumina substrate was determined so as not to change electrical characteristics from those of the unflipped MMIC. We calculated the proximity effect between the MMIC and the substrate by using 3D-electromagnetic simulator, and found that the air gap should be controlled to be greater than 20 µm. Since the discontinuity of transmission lines at bump interconnects is not negligible above 60 GHz, we constructed the LCR-equivalent circuit for the bump interconnect and confirmed its validity by comparing measurement with calculation. Based on these investigations, the 60- and 76-GHz-band CPW three-stage low noise amplifiers were successfully mounted on the alumina substrate using a thermal compression bonding process. The gain of the flipped 60- and 76-GHz-band MMICs are greater than 18 dB at around 60 GHz and 17 dB at around 76 GHz, respectively. The noise figures are 3.6 dB and 3.9 dB, respectively. The gain and noise performances showed little degradation compared to those of the unflipped MMICs when appropriate bonding conditions are given. We confirmed that the flip-chip structure has high reliability under a thermal cycle test. From these results, flip-chip technology is promising for millimeter-wave applications.

Optoelectronic hybrid integration is a promising technology for realizing the optical components needed in optical transmission, switching, and interconnection systems that use wavelength division multiplexing (WDM) and time division multiplexing (TDM). We have already developed versatile optical hybrid integrated modules using a silica-based planar lightwave circuit (PLC) platform. However, these modules consist solely of the optoelectronic semiconductor devices such as laser diodes (LDs) and photo diodes (PDs) and monolithic optoelectronic integrated circuits (OEICs). To carry out high-speed and versatile electric signal processing functions in future network systems, it is necessary to install semiconductor electrical integrated circuits (ICs) on a PLC platform. In this paper, we describe novel technologies for high-speed PLC platforms which make it possible to assemble both ICs and optoelectronic devices. Using these technologies, we fabricated a two-channel hybrid integrated optical transmitter module which is hybrid integrated with an LD array chip and an LD driver IC. On this PLC platform, we use microstrip lines (MSLs) to drive the LD driver IC. We also considered the effect of heat interference on the LD array chip caused by the LD driver IC when designing the layout of the chip assembly region. The LD array chip and the LD driver IC were flip-chip bonded with solder bumps of a different material to avoid any deterioration in the coupling efficiency of the LD array chip. The optical transmitter module we fabricated operated successfully at 9 Gbit/s non-return-zero (NRZ) signal. This approach using a PLC platform for the hybrid integration of an LD array chip and an LD driver IC will carry forward the development of high-speed optoelectronic modules with both optical and electrical signal processing functions.

Optoelectronic hybrid integration is a promising technology for realizing the optical components needed in optical transmission, switching, and interconnection systems that use wavelength division multiplexing (WDM) and time division multiplexing (TDM). We have already developed versatile optical hybrid integrated modules using a silica-based planar lightwave circuit (PLC) platform. However, these modules consist solely of the optoelectronic semiconductor devices such as laser diodes (LDs) and photo diodes (PDs) and monolithic optoelectronic integrated circuits (OEICs). To carry out high-speed and versatile electric signal processing functions in future network systems, it is necessary to install semiconductor electrical integrated circuits (ICs) on a PLC platform. In this paper, we describe novel technologies for high-speed PLC platforms which make it possible to assemble both ICs and optoelectronic devices. Using these technologies, we fabricated a two-channel hybrid integrated optical transmitter module which is hybrid integrated with an LD array chip and an LD driver IC. On this PLC platform, we use microstrip lines (MSLs) to drive the LD driver IC. We also considered the effect of heat interference on the LD array chip caused by the LD driver IC when designing the layout of the chip assembly region. The LD array chip and the LD driver IC were flip-chip bonded with solder bumps of a different material to avoid any deterioration in the coupling efficiency of the LD array chip. The optical transmitter module we fabricated operated successfully at 9 Gbit/s non-return-zero (NRZ) signal. This approach using a PLC platform for the hybrid integration of an LD array chip and an LD driver IC will carry forward the development of high-speed optoelectronic modules with both optical and electrical signal processing functions.

The hybrid electrical/optical multi-chip integration technique for optical modules for optical network system has been developed. Employing the technique, a 44 broadcast-and-select type optical matrix switch module has been realized. The module consists of four sets of silica waveguide 1 : 4 splitters/4 : 1 combiners, four 4-channel arrays of polarization insensitive semiconductor optical amplifiers with spot-size converters as optical gates, printed wiring chips for electrical wiring and single mode fibers for optical signal interface on planar waveguide platform fabricated by atmospheric pressure chemical vapor deposition. All the gates and the wiring chips were mounted precisely onto the platform at once in flip-chip manner by self-align technique using AuSn solder bumps. Coupling loss between the waveguide and the SOA gate was estimated to be 4.5 dB. Averaged fiber-to-fiber signal gain, on-off ratio and polarization dependent loss for each of the signal paths was 7 dB 2 dB, more than 40 dB and 0.5 dB, respectively. High speed 10 Gb/s photonic cell switching as short as 2 nsec has been successfully achieved.

The hybrid electrical/optical multi-chip integration technique for optical modules for optical network system has been developed. Employing the technique, a 44 broadcast-and-select type optical matrix switch module has been realized. The module consists of four sets of silica waveguide 1 : 4 splitters/4 : 1 combiners, four 4-channel arrays of polarization insensitive semiconductor optical amplifiers with spot-size converters as optical gates, printed wiring chips for electrical wiring and single mode fibers for optical signal interface on planar waveguide platform fabricated by atmospheric pressure chemical vapor deposition. All the gates and the wiring chips were mounted precisely onto the platform at once in flip-chip manner by self-align technique using AuSn solder bumps. Coupling loss between the waveguide and the SOA gate was estimated to be 4.5 dB. Averaged fiber-to-fiber signal gain, on-off ratio and polarization dependent loss for each of the signal paths was 7 dB 2 dB, more than 40 dB and 0.5 dB, respectively. High speed 10 Gb/s photonic cell switching as short as 2 nsec has been successfully achieved.

This paper describes new IC design concepts using flip-chip bonding technologies for microwave and millimeter-wave circuit integration. Two types of bonding technologies, stud bump bonding (SBB) and micro bump bonding (MBB) are introduced, and their applications to microwave and millimeter-wave ICs are presented. Receiver front-end hybrid IC (HIC) for cellular and PHS handsets using SBB and new millimeter-wave ICs on Si substrate called millimeter flip-chip IC (MFIC) using MBB have been designed and fabricated to prove their advantages. These flip-chip bonding technologies are experimentally proven to provide excellent solutions for high performance and compact-sized ICs with low-cost. The HIC concept is applicable consistently over a wide range of devices from RF/microwave to millimeter-wave region.

This paper describes new millimeter-wave ICs based on flip-chip bonding using micro bumps on a low cost silicon substrate, named millimeter-wave flip-chip ICs (MFICs). They have significant advantages such as good performance, low cost and excellent flexibility in the active device selection which makes them superior to conventional monolithic microwave integrated circuits (MMICs). In order to demonstrate these advantages, a K-band front-end block for a broadband wireless communication equipment was designed and fabricated. This front-end block consists of four MFIC chips: a low noise amplifier (LNA), a down converter and two medium power amplifiers. These chips are designed to satisfy stable operation conditions using a simplified model derived for micro bump bonding (MBB). In experimental measurements; the LNA using heterojunction field-effect transistors (HFETs) had an 18 dB gain, the down converter using an HFET had a 9. 5 dB conversion loss, and two power amplifiers using heterojunction bipolar transistors (HBTs) had saturated powers of 13. 0 dBm and 11. 7 dBm, respectively. The performance for each of the developed ICs agreed with the designed values, and satisfied circuit requirements. These results show that the MFIC technique is a potential technology for manufacturing multi-functional millimeter-wave ICs.

A new mm-wave IC, constructed by flip-chip bonded heterojunction transistors and microstrip lines formed on Si substrate, has been proposed and demonstrated by using MBB (micro bump boding) technology. Millimeter-wave characteristics of the MBB region has been estimated by electro-magnetic field analysis. Good agreements between calculated and measured characteristics of this new IC (named MFIC: millimeter-wave flip-chip IC) have been obtained up to 60 GHz band. Several MFIC amplifiers with their designed performances have been successfully fabricated.

We applied a filip-chip-bonding technique to GHz-band SAW filters. The SAW filters mounted by the stud-bump-bonding (SBB) technique which is a kind of flip-chip-bonding technique showed almost the same frequency characteristics as those mounted by the conventional wire-bonding technique at 1.5 GHz. The SAW filter configuration, fabrication process using the SBB, and its electrical characteristics are described and discussed. The SBB technique has a lot of potential to reduce the size and weight even above GHz frequencies.