/ Kazuyuki Saito / Professor
/ Kenichi Kuroda / Professor
/ Yasuhiro Hisada / Assistant Professor
The Computer Devices Laboratory, the CDL, focuses on education and research on the VLSI technologies and their related areas. The main activities are as follows:
Education:
The CDL established a frame work on the computer assisted education system for above fields. Followings are softwares for these purpose.
The CDL is performing following two Top-Down-Education Projects of the University of Aizu.
The computer devices laboratory and the computer solid state physics laboratory jointly proposed a facility for physical and chemical experiments for Solid State Physics education and VLSI education. The proposal was accepted and the detail planning is now in progress.
Research:
The main objective of the research in the CDL is to develop a new environment for VLSI design and diagnoses. That will be an intelligent manufacturing system for VLSIs including a statistical representation, a topographic representation, and an expert system representation of VLSI design and diagnoses. And the objects of representation are not restricted in the devices and processing technologies, but will cover from the manufacturing system modeling to the reliabilities of VLSI. The research projects being performed in the CDL are as follows:
Others:
Prof. Ken-ichi Kuroda newly joined the CDL on Oct. 1, 1995. He had been working for the NTT LSI Laboratories. His specialties are the super-conducting LSI technologies, X-ray lithography (especially on the lithography using a synchrotron radiation system), and VLSI design using an HDL language. Dr. K. Saito, Dr. Y. Hisada, and Mr. K. Nakazawa (in the Center for Cultural Researches and Studies) organized a research project on Psi Energy as an extracurricular project (SCCP), and preparing a measurement system of the signals from a human body. From Oct. 1995, Prof. K. Kuroda joined this project.
Refereed Journal Papers
The capacitance-voltage (C-V) characteristics of multiple-quantum-well (MQW) semiconductor heterostructures are studied theoretically. The structures with the tunneling emitter barrier show a strong variation of capacitance, starting from large values, corresponding to the emitter barrier width at low bias, and saturating at low values, corresponding to the length of the MQW structure at high bias. These features of the C-V characteristics are associated with the recharging of the quantum wells with applied voltage. In turn, the recharging effects are closely related to the electron injection and transport properties of the MQW structures.
We study a small-signal performance of a quantum well (QW) diode with triangular emitter and collector barriers providing thermionic electron transport. Analytical expression for the QW diode admittance is obtained from the rigorous self-consistent small-signal analysis. Capacitance of the QW diode depends critically on the efficiency of the electron transport through the QW, and can significantly exceed all geometric capacitances associated with the device structure. Analytical analysis of transient currents in the QW diode allows a transparent explanation why an incremental charge-partitioning technique fails to calculate the capacitance even in the low-frequency limit.
The defects induced by through-oxide implantation of arsenic into silicon have been studied using thermal desorption spectroscopy (TDS) after hydrogen adsorption on the defects. TDS peaks observed at 350$^{\circ}$C and at 540$^{\circ}$C are assigned to the desorption of hydrogen when divacancies are recovered and when the recrystallization takes place. This paper confirms that TDS is a useful too for investigating the annealing behavior of implanted defects.
An x-ray extraction setup with a double-window configuration (diamond and beryllium windows) is investigated for x-ray lithography beamlines using synchrotron radiation (SR) sources. A cylindorical frame for holding the Be foil greatly reduces the film thickness required to withstand the atmospheric herium pressure, but Be foil is subject to plastic deformation at temperatures above 250 $^{\circ}$C. A thermal shield is therefore required upstream from the Be window. Testing the combination of a 1-$\mu$m-thick diamond film as the thermal shield and a 15-$\mu$m-thick Be foil as the vacuum separation window confirmed the excellent performance of this double-widow setup even when the irradiation power was 8 W/cm$^{2}$ which corresponds to a 500 mA storage current in the NTT SR ring (Super-ALIS: critical wavelength = 17.3 A).
In order to improve the performance of X-ray lithography beamlines with a two toroidal mirror system, we have developed a simple yet efficient mirror design tool and a conventional alignment technique, A ray-tracing design tool named X-BEAM calculates a small number of rays and automatically optimizes mirror specifications in a short time. Optimization of mirror specifications proceeds by minimizing an evaluation function of power intensity uniformly and runout errors. A procedure to align mirrors using X-BEAM is also proposed. A plate which has three pinhole image configuration on screens located downstream of mirrors and by deriving manipulating parameters from X-BEAM calculation. Using these design and alignment techniques, we have achieved a highly efficient beamline using a two toroidal mirror system for X-ray lithography.
In this article, we experimentally confirm the possibility of X-ray projection using Fresnel zone plate (FZP) and monochromatic synchrotron radiation (SR) light at a wave length of 1.0 nm by pattern replication. To evaluate the characteristics and pattern ability of the FZP, we designed one with a 400-nm Ta absorber on a 0.2-$\mu$m SiN membrane with a 0.159- outermost zone with for 0.2-$\mu$m resolution. Using the designed linear and circular FZPs, the focusing image of the X-ray source we obtained was almost equal to that predicted theoretically. We used FZP projection optics to obtain single-layer resist patterns as projection images. Moreover, using a penetrat-ing mask, which is the conventional transmission type, We suctessfully replicated 0.2-$\mu$m line and space and a mesh with a reduction ratio of 112.
In this paper we present the results of the theoretical study of static and dynamic properties of multiple Quantum Well Infrared Photodetectors (QWIPs). This study is based on the original model of the QWIPs describing the electron injection from the emitter, transport in the QW structure, and capture (emission) in the QWs in a self-consistent manner. Both static and transient characteristics of the QWIPs are dominated by the contact effects associated with the recharging of the QWs under the applied voltage or infrared radiation.
High-frequency characteristics of a quantum well (QW) diode with thermionic electron transport are reported in this paper. The frequency-dependent admittance of the QW diode is obtained in an analytical using the rigorous self-consistent small-signal analysis. The frequency dependencies of the QW diode capacitance and conductance are governed by a characteristic time of the recharging of the QW, which depends strongly on temperature and device structural parameters. Experimental data on conductance and capacitance of the QW diode as functions of temperature and frequency can be used to extract the parameters of the QW, such as QW recombination velocity and ionization energy.
The purpose of this study is investigating the profiles and crystallographic configurations of the defects induced when arsenic ions are implanted into a Si substrate. The following characteristics of defects are summarized: 1) hydrogen adsorbs to form mainly $-SiH$ bonds with the implanted defects, 2) the bonds are distributed as deep as the amorphous and crystalline silicon boundary, and 3) the bond remain stable at 540$^{\circ}$C; that is, near the recrystallization temperature of silicon.
We have attempted to detect ion implanted impurities such as B, P and As which desorb from the implanted wafers. Thermal desorption of implanted impurities are directly observed. The temperature at which they start to move in the substrate are discussed. The thermal desorption method has been successively applied in detecting the above impurities to desorb from the surface for the first time. This method can be used as a micro laboratory to observe directly the thermal treatment of LSI process and to make an optimal thermal process.
This textbook is used in the lecture of VLSI Design (VLSI-I). This book includes: History of VLSI technology, Specific features of VLSI technology, MOSLSI design & circuit technologies, Fundamental devices for MOSLSI, MOSLSI process technologies, VLSI manufacturing technologies, Reliability problems in MOSLSI, and Quality control technologies.
This textbook is used in the exercise of VLSI Design. This book includes: Introduction, Design rule and layout, CMOS process design using VLSI topography simulator; PARADISE, Characteristics of MOS devices, MOS device design using process & device simulator; VEGA, Dynamic characteristics of MOS integrated circuits, and Circuit analyses using Spice.