A 4K-bit static I2L memory

A 4096-bit ECL random-access memory using high-density I²L memory cell has been developed. Novel ECL circuit techniques and I²L flip-flop memory cells are introduced for realizing high-speed performance, low-power operation, and small chip size. It operates typically under 20-ns access time and 300 mW of power dissipation, realizing 1.46 pJ/bit of access time and power-per-bit product, a figure of merit of memory devices. The memory cell and chip size of 1122 µm²(33 µm × 34 µm) and 9.9 mm²(3 mm × 3.3 mm), respectively, are achieved with V-groove isolated bipolar process technology. The memory is organized into 4096 words × 1 bit, and is packaged into 18-pin DIP and also 18-pad leadless chip carrier package. Development results have shown that the n-p-n-coupled superintegrated I²L flip-flop memory cell is very promising for high-speed and low-power static RAM's above 4K-bit/chip area.     

The annealing of phosphorus-ion-implanted cadmium telluride by a pulsed electron beam

A pulsed electron beam of 10 µs FWHM has been successfully applied to anneal phosphorus-implanted CdTe. The sheet resistance drops to 6.3 × 10²Ω/ from nearly infinite for the As-implanted wafers as the irradiation intensity exceeds 9.2 J/cm². A p-type carrier concentration as high as 3 × 10¹⁸cm^-3has been reached as measured by the van der Pauw and Hall techniques.     

Submicrometer fully self-aligned AlGaAs/GaAs Heterojunction bipolar transistor

A novel submicrometer fully self-aligned AlGaAs/GaAs heterojunction bipolar transistor (HBT) for reducing parasitic capacitances and resistances is proposed. The fabrication process utilizes SiO2sidewalls for defining base electrode width and separating this electrode from both emitter and collector electrodes. Measured common-emitter current gain β for a fabricated HBT with 0.6 × 10-µm²emitter dimension and 0.7 × 10-µm²× 2 base dimension is 26 at 9 × 10⁴-A/cm²collector current density.     

Infrared laser addressing of media for recording and displaying of high-resolution graphic information

Projection display systems which use a scanned infra-red laser beam to thermally record graphic information on different media may offer a useful alternative to CRT and other display systems. Three different types of thermal-recording projection display systems are reviewed. Laser micromachining of thin bismuth film has proved to be a very simple and efficient way to obtain instant high-quality images which are also permanent. Variable amplitude light pulses produced by an intracavity modulated laser beam were used to write these images. With an average laser power of 20 mW, 8×10 mm²facsimile type continuous-tone images, with a resolution of 1300×2000 resolvable elements, were recorded in 4 s. Thermal writing on liquid crystals offers a unique and simple way to record and display high-quality high-resolution graphic images with the capabilities of fast total or local erase. A CW Nd:YA1G laser was used to write graphic and alphanumeric-type information on cholesteric and smectic-type liquid-crystal light valves. High quality black and white images with a resolution of 2000×2000 picture elements were recorded within 30×30 mm²of liquid-crystal cell frames. With 4 mW of laser power, images were recorded at a rate of 10⁴resolvable elements per second. A contrast ratio of 7:1 was obtained with the cholesteric-type liquid-crystal light valve. The stored image was electrically erased in about 0.1 s. In smectic-type light valves, the contrast ratio was better than 10:1 and local erase was achieved by the application of an electric field while the laser beam locally heated the erased area.     

Sensitivity measurement of a 10.6-µm parametric upconverter

The sensitivity of a parametric upconverter for the detection of 10.6-µm radiation was measured. 10.6-µm radiation was mixed with the 1.06 µm beam of an Nd :YAG laser in properly oriented single-crystal proustite. The upconverted output at 0.967 µm was then detected by an S-1 photomultiplier tube. NEP of 1.1×10^-9W . s^½was measured.     

Electron microprobe analysis of impurity heterogeneities in thermally grown silicon oxide

The electron probe X-ray microanalyzer is a powerful tool for studying impurity distribution and motion in thin films. This analytical instrument is capable of detecting metallic impurities present in areas as small as 1 × 10^-6mm²and in concentrations of greater than 1 × 10¹⁹atoms/cm³. The analysis requires no sample preparation and is essentially a nondestructive test. This instrument was used to examine unoxidized and oxidized silicon surfaces and a finished microcircuit. With the electron microprobe, aluminum-bearing regions approximately one microns in diameter were detected on the bare surface of mechanically polished silicon slices. These aluminum-rich regions are believed to be alumina abrasive used in polishing. If these regions are not removed by chemical etching they will generate oxide defects during oxidation. These defects were found to contain Al (1 × 10²¹atoms/cm³and Na (1 × 10²⁰atoms/cm³). Other oxide defects, i.e., pinholes, generated during oxidation varied in size from 0.5 to 5.0 microns and were found to contain Na (1×10²¹atoms/cm³) and K (5×10²¹atoms/cm³). Mg and Ca (1 × 10²⁰atoms/cm³) were occasionally observed in these defects. After oxidation, all these impurities could be removed with a hot hydrochloric acid and deionized water rinse; surprisingly, this treatment reduced the silicon surface charge in the MOS structure (X_{0} cong 1500Å) by approximately 1.4 × 10¹¹charges/cm². The surface charge could be further reduced by heating the oxidized wafer at 900°C in a silicon nitride tube.     

Channeling depth distributions of Be and Si in GaAs as a function of implantation energy and fluence

Be and Si are commonly employed p- and n-type respectively dopants, implanted in GaAs. Channeled implantation produces deeper and sharper profiles than standard random implants. To employ channeling, we need to know how the profile shape, depth, and doping density vary with implantation energy and fluence, and what maximum density can be achieved. This work shows how channeling profiles in the direction of GaAs vary with energy and fluence for room temperature channeling. Data are shown for fluences of 3 × 10¹², 3 × 10¹³, and 3 × 10¹⁴cm^-2and energies of 40, 75, 150, and 300 keV. The deep channeling profile saturates for 150 keV Be just below a fluence of 3 × 10¹⁴cm^-2and a density of about 4 × 10¹⁷cm^-3can be achieved at depths of about 1 to 3 µm for energies from 75 to 300 keV. The maximum density for 150 keV Si for room temperature channeling is about 4 × 10¹⁶cm^-3and occurs at depths from 1 to 4 µm in the energy range from 40 to 300 keV.     

A three-dimensional static RAM

A three-dimensional (3-D) 256-bit static random-access memory (RAM) with double active layers has been fabricated by using the laser recrystallization technique. Memory cells were located in a bottom active layer with an NMOS configuration and peripheral circuits were arranged in a top active layer with a CMOS configuration. Both active layers were connected by 112 via holes. The chip and cell sizes were 2.6 × 1.9 mm²and 50 × 70 µm², respectively. The memory operation was observed with a supply voltage from 4 to 8 V. The shortest address access time of 42 ns was obtained at the supply voltage of 8 V.     

A frame-transfer CCD color imager with vertical antiblooming

A high-density 604 (H)× 576 (V) frame-transfer CCD color image sensor is realized with a pixel dimension of 10.0 (H) × 15.6 (V) µm², an image diagonal of 7.5 mm, and a total chip area of 66 mm². On-chip color filters and the use of a triple read-out register result in separate Cy, G, and Ye output signals. The imager is an n-p-n buried-channel CCD which can handle 125 times overexposure with vertical antiblooming. For the calculation of a suitable dopant distribution in the image, storage, and output sections, a four-step procedure has been developed. This procedure has proved to be successful and is much faster than an approach based exclusively on two-dimensional potential calculations.     

Some reactive effects in forward biased junctions

The small-signal equivalent parallel capacity of forward-biased semiconductor junctions is strongly dependent on the current. At very low currents (less than 10 µa for a junction area of 1 mm²) the capacity appears to be chiefly due to space charge effects. For currents up to approximately 100 µa, the capacity complies with Shockley's predicted low-level theory. For larger currents, however, there is a definite deviation from the low-level diffusion predominance and capacity reaches a maximum after which it decreases through zero and then goes to large inductive values. The latter phenomena is explained, qualitatively, by considering an inductance in series with the diffusion capacity. The capacity increases linearly with current but the inductance (due to conductivity modulation) increases faster. The result is that a change from an equivalent RC circuit to an equivalent RL circuit is made at high enough currents (5 ma is a typical value for the 1 mm²junction area). Measurements were made on abrupt silicon junction diodes with junction areas of about 7 × 10^-4, 10^-2, 10^-1cm²and on the emitter junction (about 5 × 10^-5cm²) of a diffused base silicon transistor.     

Surface carrier wave amplification in InSb at X-band

Experiments have been conducted with slabs (1.5 × 2.5 × 0.3 mm³) of n-InSb to determine the propagation of surface waves in the presence of drifting carriers. Interdigital transducers of 10 fingers each with finger width of 7.5 µ (periodicity 30 µ) are used to excite slow surface waves with phase velocity on the order of the electron drift velocity of 2 × 10⁷cm/s. Integrated coplanar strip lines are used to carry to and from the transducers to X-band waveguides at each end. A nonsaturable unidirectional electronic gain of 11 dB/mm has been observed in the presence of counterstreaming electron-hole plasma created under pulsed high fields and a transverse magnetic field of 10 kG. The experimental results are explained on the basis of a surface plasma wave propagation model including the surface properties of the material through the surface recombination velocity. Rougher surfaces are shown to result in enhanced interaction but suffer from the susceptibility to oscillations. Reasonably well prepared but not exceptionally smooth surfaces are found to be better from the point of view of stable amplification.     

An improved scan laser with a VO2programmable mirror

A 10.6 μm scan laser has been constructed and operated with an off-axis cathode ray tube, high reflectance multilayer thin-film structures, and a tapered plasma discharge tube. Equations are given for the switching time of a high-reflectance spot on the VO2and for the relation of scan laser output power to cavity geometry, cavity losses, and the gain of the active CO2medium. A scan capability of2.1 times 10^{3}easily resolvable directions was demonstrated, and sequential and randomly addressed spot rates of 10⁵/s were achieved. The equations relating output power and cavity mode size were experimentally verified using a nonscanned beam.     

In-situ low energy BF2+ion doping for silicon molecular beam epitaxy

An experimental study of the p-type ion dopant BF2+ in silicon molecular beam epitaxy (MBE) is described. BF2+ was used to dope MBE layers during growth to levels ranging from 1 × 10¹⁶/cm³to 4 × 10¹⁸/cm³over a growth temperature range of 650°C to 1000°C. The layers were evaluated using spreading resistance, chemical etching, and secondary ion mass spectroscopy. Complete dopant activation was observed for all growth temperatures. Remnant fluorine in the epitaxial layer was less than 2 × 10¹⁶/cm³in all cases. Diffused p-n junction diodes fabricated in BF2+-doped epitaxial material showed hard reverse breakdown characteristics.     

Properties of ion-implanted junctions in mercury—cadmium—telluride

The formation of n-p junctions by ion-implantation in Hg0.71Cd0.29Te is shown to be a result of implantation damage. n-p photodiodes have been made by implantation of Ar, B, Al, and P in a p-type substrate with acceptor concentration of 4 × 10¹⁶cm^-3. The implanted n-type layer is characterized by sheet electron concentration of 10¹⁴to 10¹⁵cm^-2and electron mobility higher than 10³cm². V^-1. s^-1, for ion doses in the range 10¹³-5 × 10¹⁴cm^-2. The photodiodes have a spectral cutoff of 5.2 µm, quantum efficiency higher than 80 percent, and differential resistance by area product above 2000 Ω . cm²at 77 K. The temperature dependence of the differential resistance is discussed. The junction capacitance dependence on reverse voltage fits a linearly graded junction model. Reverse current characteristics at 77 K have been investigated using gate-controlled diodes. The results suggest that reverse breakdown is dominated by interband tunneling in field-induced junctions at the surface, for both polarities of surface potential.     

Performance characteristics and extended lifetime data for InGaAsP/InP LED's

The performance and lifetest results of InGaAsP/InP LED's emitting at 1.27 µm are described. At a current density of 10 kA/cm², 40 µW of optical power is coupled into a 63 µm core, 0.21 NA optical fiber, and the projected lifetime at room temperature is approximately estimated to be 8 × 10¹⁰hours.     

The DSI diode—A fast large-area optoelectronic detector

Fast double-Schottky-interdigitated diodes have been fabricated by evaporating Al-Schottky contacts on lowly doped n-GaAs (n=10¹⁴cm^-3), These detectors have a relatively large light-sensitive area of 400 µm². Rise and fall times are in the order of 10 ps. The external quantum efficiency is 25 percent at λ = 820 nm. The frequency response of the diodes is essentially flat up to 18 GHz, which is the limit of the measuring equipment.     

Hybrid IRCCD imaging array

A hybrid IRCCD for high background application has been successfully fabricated. The device consists of fifty Hg0.7Cd0.3Te detector diodes of 50-µm × 50-µm sensitive areas and a silicon CCD maltiplexer with input circuits on 40-µm centers having bucket background subtraction and blooming protection circuits. The noise-equivalent power (NEP) of the IRCCD is 5 × 10^-14W-Hz^-1/2at background photon flux level of 4 × 10¹⁵photons . cm^-2s^-1, integration time of 2 × 10^-5s, and clock frequency of 3 × 10⁶Hz. The noise source of the detector diodes limits the IRCCD performance. The IRCCD is also evaluated with the real-time raster-scanned thermal images displayed on a CRT monitor. Two-dimensional images are generated by using a scanning mirror. A fixed-pattern noise is reduced by comparison of an object video to the reference video stored in a memory. A noise-equivalent temperature difference of the system is 0.6°C at a frame rate of 30 Hz. Instantaneous field of view is 1 mrad × 1 mrad and the field of view of the system is 12° × 5.7°.     

Source—Drain contact resistance in CMOS with self-aligned TiSi2

The contact resistance between TiSi2and n⁺-p⁺source-drain in CMOS is studied for a variety of junction profiles and silicide thicknesses. It is shown that the measured contact resistance is consistent with the transmission-line model for electrically long contacts. The contact contribution to the total device series resistance can be significant if excessive silicon is consumed during silicide formation. Contact resistivities of 3 × 10^-7and 1 × 10^-6Ω . cm²can be obtained for 0.15-0.20-µm-deep arsenic and boron junctions, respectively, if the interface doping concentration is kept at 1 × 10²⁰/cm³. Furthermore, low-temperature measurements show that the contact resistivity is nearly constant from 300 to 77 K, as would be expected from a tunneling-dominated current transport at the TiSi2-n⁺and TiSi2-P⁺interfaces.     

Quadruply self-aligned MOS (QSA MOS)—A new short-channel high-speed high-density MOSFET for VLSI

A new device named Quadruply Self-Aligned (QSA) MOS is proposed to overcome speed and density limits of conventional scaled-down MOS VLSI circuits. This device includes four mutually self-aligned areas: narrow poly-Si gate, shallow-source/drains to eliminate short-channel effects, deep junctions for high conductance, and specific contacts to afford efficient metal interconnection. To get these four regions to register, the gate pattern is first defined followed by undercutting of the polysilicon, anisotropic reactive ion etching of the gate oxide, and ion implantation into the source/drain regions. The device has been fabricated and its proper operation has been demonstrated. Because of its short-channel length and small gate-drain overlap capacitance, this device allows the design of high-speed VLSI circuits using high-conductive interconnects. Also, the self-aligned process allows the design of high-density VLSI circuits. It is shown that the design of the ultimate 3F × 2F cell (6 µm²/cell, namely 3 × 2 mm²/1 Mbit in 1-µm rule) and the 4F pitch sense amplifier in dynamic MOS RAM are feasible using this QSA technology. (F is the minimum feature size.)     

Microchannel plate inverter image intensifiers

The characteristics of microchannel plate/inverter image intensifiers (MCP/III) are described. This type of image tube is shown to be well suited to some night vision applications. The 25 mm MCP/III developed by the authors has a minimum magnification of 0.96, a maximum distortion of 5 percent, and a limiting resolution of 10 cycles/mm. Its luminance gain is about 10⁵at input levels up to 2 × 10^-3fc when an S20 photocathode and a P20 phosphor screen are employed. The operational life of a MCP/III is generally a few thousand hours. Accurate life data can be determined, for a given application, after the operating input light level value, the applied MCP potential, and the duty cycle are established. The unique bulb design allows the tube high voltage power supply to be placed around the tube envelope within a 50 mm diameter and reduces the total interelectrode capacitance of the gating/focus electrode to 7 pF.