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QUANTUM MAGNETO FLUX trapped magnetic flux from supercon- while conventional pipeline acceler-
LOGIC PROJECT: SUPER- ductors, as the first step toward a ates only a factor of 3 using the same

project consists of three groups, Fun- The Magnetic Shielding Group

damental Property, Computer Archi- aimed for the verification of a high Project Director: Eiichi Goto

tecture, and Magnetic Shielding. The performance refrigerator and establish

former two were at Hitachi's Central ment of trapped flux detection and The advancements of supercomput. Research Laboratory and the third one removal technology. The characterisers have made it possible to simulate was with ULVAC Corp.

tics of a bellows type refrigerator were many complicated natural and artifi- The detailed achievements of this examined first, and it was found that cial phenomena, such as meteorology, project are listed in References 3 and 4 multilayering eases the maximum stress. large-scale integration (LSI) design, and and a brief summary is stated here. The The fatigue strength of bellows was even protein structures. However, more Fundamental Property Group aimed also made clear. The new pulse-tube than several hundreds of times faster to clarify the physics of QFP devices to type refrigerator, which has no moving computers should be required to accu- investigate the QFP logic circuit design, parts in the low temperature region, rately analyze these large and compli- to demonstrate very fast operation of was investigated and high efficiency and cated systems, including long-term QFP circuits, and to verify 3D integra- reliability were ascertained. The trapped weather forecast, accurate ultra LSI tion. A highly functional logic gate, flux in the superconductor film was (ULSI) design, and DNA simulations. D-gate, was proposed and was shown detected by superconducting quantum The silicon LSIs, which are mainly uti- to be twice as powerful as compared interference device (SQUID), with a lized in today's supercomputers, should with semiconductor logic gates. The spatial resolution of 100 um and a face such limitations as power con- operation of D-gate was successfully magnetic field resolution of less than sumption and propagation delay in these demonstrated by experiment. A shift 0.1 flux quanta. The trapped flux was very large and fast computer systems. register circuit, fabricated by 5-um Pb successfully removed by irradiating a Therefore, very fast operation and low alloy technology, operated at 16 GHz laser beam to the superconductor film power consumption devices should be and was simulated to operate at 100 GHz and heating it up to the normal state necessary for the future high perfor- if 2.5-um Nb technology was utilized. (micro heat flushing). mance computer systems.

Other circuits, such as analog-to-digital These achievements of the QMFL A quantum flux parametron (QFP) converters, were also demonstrated to project, which came to an end in device was first reported in 1984 (Ref 1) operate at more than 18 GHz. Three- September 1991 and has already reached and was named after the parametron dimensional signal transfer via mag- the applied research level, will be sucdevice (Ref 2) invented about 30 years netic coupling was also successfully ceeded by a high-tech consortium, with before. QFP is a very promising candi- demonstrated. These results suggest that Hitachi and ULVAC, supported by date for future supercomputers because QFP is a very promising candidate for JRDC. The other achievements, in a of its very low power dissipation (10-9 w/ the future high performance computers. relatively basic research level, will be gate) and fast switching speed (10-12 s/ The Computer Architecture Group further pursued by the Goto Research gate), with its capability of three- looked into the cyclic pipeline archi- Laboratory at RIKEN. dimensional (3D) packaging through tecture (CPC), which is suitable for the magnetic coupling. These characteris- very fast latching circuits, such as QFPs. KUNITAKE MOLECULAR tics should make it possible to inte- Compilers and several application soft- ARCHITECTURE PROJECT: grate the whole system in a very small ware were designed, and the perfor- NOVEL FUNCTIONS volume. Thus, a TFLOPS (1012 float- mance of CPCwas verified. Along with THROUGH SELFing operations per second) computer these simulation studies, a CPC com- ORGANIZATION OF should be made possible by QFP cir- puter, made of silicon emitter-controlled MOLECULAR MATERIALS cuits. The Quantum Magneto Flux Logic logic (ECL) integrated circuits, was (QMFL) project aims to demonstrate designed and fabricated, and the per- Project Director: Toyoki Kunitake (1) multi GHz operation of QFP cir- formance was evaluated using standard cuits; (2) highly functional QFP logic supercomputer benchmarks. It was made The biomembrane is formed by circuits; (3) a suitable operation sys- clear that CPC architecture acceler- self-organization of component moletem for fast QFP computers; (4) a reli- ates the performance by a factor of 10, cules (lipids and proteins) that are able refrigerator; and (5) removal of if 12 jobs are processed in parallel, derived from their unique steric structures. The preparation of synthetic nucleotides, ATP) in specific manners. Composite Architecture Group. bilayer membranes has been success- The strong binding behavior observed Regular multilayer films were obtainfully achieved in Japan and other coun- in exposure to bulk water at the air- able from aqueous mixtures of bilayers tries by using a large variety of novel water surface is surprising.

and polar bifunctional monomers. organic compounds. These compounds Surface force measurements pro- Photoirradiation and removal of the are composed of hydrophilic head groups vided the evidence for a strong attrac- template produced multilayered twoand hydrophobic hydrocarbon chains tive force between two hydrophobic dimensional (2D) polymer networks. in an analogy to biolipid molecules. surfaces at an unprecedented distance When allylammonium monomers were This new molecular system provides an of 300 nm. Any theory to explain this

of 300 nm. Any theory to explain this used, multilayered ultrathin ion exciting possibility to produce artificial effect has not been proposed yet. The exchange films were formed. A similar organization and to lead to a new field subsequent measurement of repulsion technique was realized in nonaqueous of chemical science.

between two polyelectrolyte-modified media by the use of polyfluorinated In our ERATO project, the major surfaces produced data that could be amphiphiles, which formed ordered emphasis is placed on self-organization discussed in the conventional theoret- dispersions in some organic solvents. of the above-mentioned types of organic ical framework.

These fluorocarbon amphiphiles also molecules in the form of surface mono- Scanning tunneling microscopy gave uniform, stable monolayers. layers, Langmuir-Blodgett (LB) films, (STM) showed that azobenzene- Molecularly thin 2D networks were aqueous bilayers, and cast films. We carboxylic acids were regularly aligned prepared by covalent bonding of ion aim at construction of molecular orga- on highly oriented poly graphite complexes of oppositely charged polynizations that would possess particular (HOPG). The liquid crystalline nature mers formed at the air-water interface. electronic, magnetic, and chemical of the azobenzene derivatives was closely Defect-free films of a few molecular functions. Improvements of these func- related to complete wetting of graphite. layers were thus formed by proper tions will be attained by means of chem

combination of the starting polymers. ical modifications of simple assemblage Functional Architecture Group. The and formation of multiply composed self-assembling property of synthetic Direct Observation of organizations. These studies should bilayer membranes was used to pro- Molecular Assembly by provide clues for the development of duce regular organization of metal ions Scanning Tunneling novel industrial materials that are (transition metals and lanthanides) on Microscopy equipped with sophisticated functions a two-dimensional molecular surface. analogous to those of the biological Multilayered films of ultrathin silicate Masahito Sano, Fundamental Design organization and yet are characterized and aluminosilicate layers were pre- Group by stability and processability of syn- pared by using cast films of synthetic thetic materials.

bilayer membranes as molecular tem- Azobenzene derivatives, selfOur laboratories are set up at plates. The morphology of the highly assembled on the graphite surface, were Kurume Research Park on Kyushu porous silicate was replicas of aqueous imaged directly by STM in air (Ref 5). Island. The total staff is 21, as of bilayer dispersions and showed surpris. The images confirmed the model pre1 October 1991, including project direc- ing variations depending on the com- viously proposed for layered aggregates tor, administrative staff, researchers, position and the preparative conditions. and compared well with the bulk corand technicians. The whole research An ion exchange technique applied to relation length. The methyl terminated team is divided into three groups. The cast multilayer films provided an addi- compounds frequently showed bimocurrent activities of each group are tional template procedure. These lecular packings, while the brominated described below.

methods were also used to obtain derivatives indicated a monomolecu

metal oxide multilayers from ultra-fine lar structure. The difference in the Fundamental Design Group. We particles of metal oxides.

distance between the carbon-hydrogen have prepared a series of surface mono- A series of novel oligo (phenylene- and the carbon-bromine atoms is an layers that possess hydrogen bonding vinylene) amphiphiles formed stable important factor contributing to these functionalities such as phenolic hydroxyl, monolayers on water. Some of these different packing styles. carboxylic acid, 2,6-diaminotriazine, wholly pi-conjugated monolayers pro- In the course of sample preparadiphenyl-urea, and guanidinium. These duced Z-type LB films with nonlinear tion, it has been found that the liquid monolayers bind biologically impor- optical properties.

crystalline molecules with a sufficiently tant compounds (sugars, amino acids,

long alkyl chain in the nematic phase wet the basal plane of graphite com- can form self-supporting, multi-bilayer This research will hopefully lead to pletely. Also, alkylated compounds that films by casting from water or from the fabrication of semiconductor eleare not liquid crystalline can be made appropriate organic solvents. Especially, ments at the level of molecular layers, to wet the graphite completely by form- those amphiphiles that have olefinicor giving birth to a new engineering field ing a mixture with other compounds. ether units in the tail exhibit higher that might well be called Molecular These observations, together with STM solubilities (dispersibilities) in many Electronics. It should also contribute images of these compounds, allow us organic solvents and produce well- to a sharp increase in not only the to argue a mechanism of wetting on a ordered films rather readily.

measuring techniques of lattice and molecular scale.

These fluorocarbon amphiphiles can molecular oscillations but also the future

be used as molecular templates to pre- speed and volume of communication Synthesis of Multilayered pare multilayered poly(stearyl acrylate). devices. Inorganic Ultrathin Films by The thickness of the individual layer is

ng Cast Multi-Bilayer Films determined to be 500 Å or less by scan. Research Strategy as Molecular Templates ning electron microscopy (SEM). The

formation of multi-bilayer cast films This project is investigating comMunetoshi Isayamagi

, Functional Archi- even from organic solvents enlarges pound semiconductors of the size of tecture Group the usefulness of the casting technique. molecular ultrathin layers fabricated

by carefully controlled photo-stimulated Cu2+ ion was incorporated into a NISHIZAWA TERAHERTZ molecular layer epitaxial growth. Since multi-bilayer cast film of a phosphate PROJECT: EXPLORATION it is not certain whether knowledge amphiphile by an ion exchange pro- FOR TERAHERTZ

concerning electron behavior in concess. The Cu2+ ion showed different SEMICONDUCTOR DEVICES ventional element structures is applielectron spin resonance (ESR) patterns

cable to devices operating in the teradepending on the angle of the cast film Project Director: Jun'ichi Nishizawa hertz frequency region, crystal techsurface against the magnetic field.

nology at the molecular-layer level is Silicate and silica-alumina ions can Background

being studied. be also inserted into the cast film of an

Circuits that can operate as a mixer, ammonium amphiphile in stoichio- The last several decades has wit- detector, harmonic generator, and metric quantities by the same technique. nessed a tremendous growth in the traveling-wave type optical modulator Ultrathin films of silicate and silica- understanding and development of solid- are also being investigated. New devices alumina could be obtained after extrac- state materials, resulting in a prolifer- that are very thin, less than several tion of the amphiphile.

ation of semiconductor devices. These hundred molecular layers, must be The high regularity and the ion can be applied to ever-increasing regions achieved not only for devices used to exchange ability of a multi-bilayer cast of the electromagnetic spectrum. amplify signals but also for detectors film that was prepared from a self- In the electromagnetic wave region and receivers that can also convert assembling amphiphile enable orien- the usable frequency band has been optical waves into lower frequencies. tation control of inorganic structure extended to 10" Hz (3-mm wavelength) units and synthesis of molecularly thin owing to technological advancements Research Progress inorganic materials.

of microscopic semiconductor elements

(less than 0.1 micron). Further, the A buried heterostructure Raman Preparation of Ultrathin

near-infrared region (near 1-micron laser has been investigated in which an Fluorocarbon Film and its wavelength) is now usable owing to intermediate layer is formed for pump Application

progress in quantum electronics. Jun'ichi power introduction, while Stokes radi

Nishizawa is presently following up his ation is confined within the active region Kenji Fukuta, Composite Architecture very successful Perfect Crystal project without any disturbance from the Group

(described in post-project-phase entrance window. Lasing has been

ERATO projects) with a study of the demonstrated and the pump power Novel double-chain ammonium manipulation and use of the hitherto improved to as low as 0.5 W. The fabriamphiphiles, whose alkyl tails are unexplored terahertz region (1012 Hz cation method is based on liquid-phase composed of fluorocarbon and hydro- or 300-micron wavelength).

epitaxy by a temperature-difference carbon segments, are synthesized. They

method under controlled vapor pres- wave and modulating wave phase veloc- Such n+np*n'nt sandwiches have sure, which can maintain a very low ity are matched. Three-dimensional fine bean fabricated with MLEon GaAs(100) nonstoichiometric defect concentration processing is necessary to fabricate steps n wafers. The fabrication process For the first time very perfect control of a few microns height and vertical, started with a 20-nm-thick nt buffer of the crystal thickness in single crys- smooth sidewalls. The etching of the followed by subsequent growths of a tals has been achieved.

dielectrics and semiconductors used for 200-nm-thick no layer, thin pt layer, In molecular-layer epitaxy the car. optical waveguides and metals for 50-nm-thick n' layer, 20-nm-thick n* rier concentration in a film strongly electrodes has progressed.

source layer, and finally a 10-nm-thick depends on the injection period of There are three subgroups in our layer for contact. The potential impurity gas, as well as substrate sur- project located in Sendai: Basic Anal- barrier value is a very sensitive funcface orientation. From studying the ysis, Functional Device, and Circuit tion of the Zn doping of the player. doping efficiency of Si using Si H., it Configuration. In the Basic Analysis So far, selective fabrication of could be doped on a Ga-compound Group, the photo-stimulated molecu- semiconductor regions of one substrate surface. Sites may be influ- lar layer epitaxy (MLE) technique is conduction type, surrounded by regions enced by the AsH, pressure. More- used to obtain the very thin epitaxial of opposite type, was characteristic for over, Si can be incorporated as a donor layers for the very high speed transis- silicon rather than for III-V device on the (111)Bor (100) surfaces and as tors and diodes. Several kinds of devices technology. We applied MLE for an acceptor on the (111) A surface. such as the SIT, the Tunnett diode, the selective growth of GaAs pn structures

Films have been made that are thin- semiconductor Raman laser, etc. have in grooves, similar to those required ner than the carrier mean free path, been developed. The circuits that oper- for gates of ISIT devices. A GaAs resulting in the absence of both colli- ate as the mixer, detector, harmonic substrate with an n Si doped metal sions and scattering by lattice vibra- generator, travelling-wave-type optical organic chemical vapor deposited tion, enabling a mesoscopic static induc- modulator, etc. are also being (MOCVD) layer was covered by phototion transistor (SIT) to be fabricated investigated.

excited chemical vapor deposited with an operation speed greater than

(PECVD) silicon nitride. The SiN was 1 THz. Ideal Static Induction

patterned to form square openings. This Progress has also been made towards Transistor (ISIT)

served as a mask for subsequent wet an SIT device with a very thin base

etching of grooves in GaAs and as a layer, thus limiting the frequency. Piotr Plotka, Functional Device Research mask for epitaxy. Two different MLE Eventually, both Tunnett and SIT prep- Laboratory

processes were checked: one doped with aration will be combined.

Zn and the second doped with carbon. A fabrication procedure for Pt/GaAs Yutaka Oyama, Basic Analysis Research Current-voltage measurements were diodes (used for low-noise mixers with Laboratory

performed to evaluate quality of the low conversion loss in the THz region)

regrown pn junctions. Characteristics has been developed. Reactive ion etch- The ISIT transistor may be looked of diodes containing MLE layers on ing and surface treatment of GaAs wafer at as composed of some "building (100) bottom and sidewalls parallel to surfaces have been improved and the blocks":n*n'ptn'n sandwich, extrin- the {01-1} direction of the groove and diode diameter reduced to obtain a sic gate, and nonalloyed contacts. To terminated at overhanging SiN are not higher cutoff frequency: 0.8-micron- develop a fabrication process, methods worse than characteristics of diodes diameter diodes have been fabricated for fabrication of these blocks should with MLE layers on (100) bottoms only. with a 11,600-K mixer noise tempera- be developed first.

However, the performance of regrown ture and a 19.1-dB conversion loss at a Nearly ballistic operation of the ISIT pn junctions fabricated with Zn as signal frequency of 1.4 THz. Further, can be obtained if the distance between dopant is better than for C as dopant. an antenna pattern suitable for imag- highly doped nt regions of drain and The ideality factor of forward characing optics and antenna impedance of a source is on the order of 100 nm (Ref 6). teristics for Zn-doped junctions is n=1.3, good Schottky diode by tuning the direc- To induce a potential barrier, we applied whereas in the case of Cdoping n=1.6. tor element of a Yagi-Uda antenna has a very thin, fully depleted player inside The technique developed for selecbeen achieved. A new-type traveling- an no layer, an idea taken from high tive growth of pn junctions with MLE wave optical modulator is being devel- power SIT devices and planar doped can find application not only for oped and analyzed in which the optical barrier devices.

fabrication of gates on ISITs but also for many other devices. It is attractive In conventional impact avalanche we have the basic technology for freespecially because of the low tempera- transit-time (IMPATT) diodes, reduc- quency measurements from the far ture required to grow MLE layers. ing the device dimensions causes an infrared to infrared.

To exploit fully the advantages of increase of the electric field intensity in The Tunnett diode oscillation sysvery thin layers that can be grown with the injection region. Eventually, tun- tem is very convenient because of its MLE, we are working on development neling replaces avalanching as the high small size and power requirements. It of nonalloyed contacts to both n and p frequency carrier injection mechanism. is considered that submillimeter osciltype GaAs.

Therefore, it can be said that the Tunnett lation from the Tunnett diode will be Contacts to n-type GaAs were formed diode is necessary to obtain higher very important for the development of by lift-offon MLE layers heavily doped frequencies.

devices in this frequency region. Furwith selenium. The specific contact A field intensity in the injection ther, it will make a significant contriresistance, evaluated with the trans- region of about 106 V/cm is needed to bution to the study of the interaction mission line method, was in the range get tunnel injection. On the other hand, between submillimeter waves and of low 106 12-cm? This is the best in the running region a field intensity matter. reported result for homogeneously of about 104 V/cm is sufficient to obtain doped n-type GaAs.

the saturation velocity of carriers. To Photoexcited Etching of GaAs The specific contact resistance for achieve such field intensities in these p-type GaAs MLE layers heavily doped two regions, it is necessary to control Kenji Yamamoto, Functional Device with Zn is 2 x 106 S2-cm2. Although thickness and doping concentration of Research Laboratory other methods enable obtaining even each layer precisely. MLE is a promislower values of contact resistance, and ing method to realize the necessary To fabricate a superlattice strucare selective as well, the advantage of precision. It is considered that submil- ture or a quantum effect device, atomic this method is the possibility of fabri- limeter oscillation of the Tunnett diode scale controllability of processing is cating high quality pn junctions with with optimized potential distribution demanded. In recent years, there have excellent coverage of sidewalls of will be realized with an applied voltage been many reports on the use of the complicated shapes. This makes the of about 1 V. We are now making alternate operation of gas feeding, which method suitable for contacts to thin, Tunnett diodes to oscillate in the tera- has atomic scale controllability in thinburied layers or two-dimensional hole- hertz region.

film growth, but few such reports in gas layers.

We are also researching resonators etching. In conventional etching, the

for the submillimeter region. One type etchant and the energetic particles (ion, Tunnett Diode

is a waveguide cavity resonator and electron, photon) are introduced onto

another is an open resonator. We can- the substrate simultaneously. On the Toshifumi Suzuki, Functional Device not analyze the behavior of resonators other hand, in digital photoexcited Research Laboratory

in the submillimeter region directly etching (DPE), the etchant and ultra

because no network analyzer for this violet (UV) irradiation are applied The tunneling-electron transit-time region exists. So we made a W-band alternately (Ref 8,9). The basic condiode, the Tunnett diode, is considered resonator (75 to 110 GHz) and mea- cept is as follows: (1) The etchant is the most important semiconductor sured network characteristics with good introduced into the chamber and is device in the submillimeter-wave region. results. In the submillimeter region, adsorbed on the substrate (the etchant We have made Tunnett diodes using the electromagnetic wavelength is very should not etch the substrate spontaMLE, controlling layer thickness with small, so it is very difficult to make

small, so it is very difficult to make neously at this moment). (2) Excess an accuracy on the order of one molec- waveguide cavity resonators for this etchant is evacuated. (3) UV light irradiular layer (Ref 7).

region. Therefore, it is expected that ates the surface to initiate the photoThe Tunnett diodes we have made the larger dimensions of the open res- chemical reaction between adsorbed utilize ap*n*i(n)n* structure. Tunnel onator will make it easier to fabricate. etchant and the surface atoms and to current is injected from the pÎnt region We have used a Fourier-transform promote the photodesorption of into the i(n) region. The oscillation infrared (FTIR) system to measure the products. frequency depends on the running time oscillation frequency of Tunnett diodes. In the present study, DPE of GaAs of these carriers in the i(n) running The Michelson interferometer in this (100) and (111) has been demonstrated region. Therefore, to obtain a higher system has a Mylar film as a half mirror. with a Xe/Hg lamp/Cl2 system. Depenfrequency, it is desirable to reduce the We have measured a wavenumber of dence of etching rate per cycle on UV thickness of the running region. 4.5 cm-' (135 GHz). With this system, irradiation time, Cl, evacuation time,

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