The lattice parameter of high‐purity silicon is measured as a function of temperature between 300 and 1500 K, and the linear thermal expansion coefficient is accurately determined. Precise measurements are made by the high‐temperature attachment for Bond’s x‐ray method to a few parts per million. It is found that the temperature dependence of the linear thermal expansion coefficient α(t) is empirically given by α(t)=(3.725{1−exp[−5.88×10−3{(t−124)} +5.548×10−4t)×10−6 (K−1), where t is the absolute temperature ranging from 120 to 1500 K. It is shown that the lattice parameter in the above temperature range can be calculated using α(t) and the lattice parameter at 273.2 K (0.5430741 nm). Measured values of the lattice parameter and the thermal expansion coefficient for high‐purity float‐zoned (100 kΩ cm) and Czochralski‐grown (30 Ω cm) single crystals are uniformly distributed within ±1×10−5 nm and ±2×10−7 K−1 with respect to the values obtained from the above empirical formula.

Precise determination of lattice parameter and thermal expansion coefficient of silicon between 300 and 1500 K

Silicon molecular beam epitaxy

Building on nearly two decades of reported results for MOSFET's fabricated in small-grain polycrystalline silicon, a design methodology is developed that yields devices which have low threshold voltage, high drive current, low leakage current, tight parameteric control, and reduced topology, while requiring no nonstandard materials, processes, and tools. Design criteria and device performance are discussed, grain boundary characterization techniques are described, technological issues pertinent to VLSI implementation are investigated, and long-term device reliability is studied. The potential applications of the polysilicon MOSFET's in high-density dRAM and sRAM are explored. The successful implementation of an experimental stacked CMOS 64K static RAM proves the utility of these devices for three-dimensional integration in a VLSI environment.

Characteristics and three-dimensional integration of MOSFET's in small-grain LPCVD polycrystalline Silicon

The specific current-voltage characteristics of epitaxial silicon films on insulator (ESFI®) SOS MOS transistors are shown, discussed in comparison to bulk silicon MOST's, and explained by the differences in geometrical considerations, charge distribution, and operation mode, The ESFI MOST's are produced on silicon islands, in most applications, the electrical substrate is at floating potential. This results in two effects. At first a threshold voltage change occurs with increasing drain voltage, producing a kink in the current curve; if the drain voltage further increases, a parasitic bipolar transistor begins to work and effects another kink or bend in the curve. On the other hand, the finite vo|ume effects a strong dependence of the base width of the parasitic bipolar transistor on the drain voltage and causes a rise of the current amplification with the drain voltage. The finite volume below the gate oxide also limits the bulk-charge magnitudes with subsequent increase in mobile carrier charge, thereby increasing the transconductance. All these effects are also described theoretically; the I D -V D characteristics could be simulated by computer model based on the physical effects.

Properties of ESFI MOS transistors due to the floating substrate and the finite volume

The critical aspects of the epitaxial growth of alkaline-earth oxides on silicon are described in detail. The step by step transition from the silicon to the alkaline-earth oxide as shown through reflection high energy electron diffraction is presented, with emphasis placed on the favorable interface stability, oxidation, structural, and strain considerations for each stage of the growth via molecular beam epitaxy.

Critical issues in the heteroepitaxial growth of alkaline-earth oxides on silicon

A model is proposed to explain the anomalous current-voltage characteristics of ESFI MOS transistors. Due to the floating state the substrate potential of the ESFI transistor is increasing with increasing majority carrier current flowing through the substrate to source. In the region of multiplication by avalanche that effect will get quite pronounced. The change of substrate potential yields a change of the threshold voltage hereby increasing the drain current and resulting a bend in the I D (U D ) curves. The assumptions of the model have been justified by additional experiments as with illumination of light or increased temperatures. Based on the physical model a computer program was developed to simulate the I D (U D ) characteristics of ESFI MOS transistors of the enhancement type, resulting good agreement between measured and simulated characteristics.

Influence of the floating substrate potential on the characteristics of ESFI MOS transistors

Silicon films on single crystal magnesium-aluminium spinel slices and similarly on sapphire are strained under compressive stress. This is due to the difference in thermal expansion and to the high growth temperature, causing a curvature of the slices. The coefficients of thermal expansion have been measured by a dilatometer. From the curvature measured by a stylus tracing method a residual stress of about 8 × 10 3 kp/cm 2 has been determined. The expected change in resistivity, effective Hall mobility, and band gap has been calculated from the known influence of stress on the electrical properties of bulk semiconductors, and has been compared with the experiments. The measured mobility as a function of carrier concentration has a maximum between 10 16 and 10 17 carriers per cm 3 . The highest mobilities measured were 600 cm 2 /V-sec for n -type and 350 cm 2 /V-sec for p -type silicon films. The observed decrease of carrier mobility with decreasing carrier concentration (for n , p ≤ 10 16 cm −3 ) and the relatively low minority carrier lifetime are explained by the assumption of space-charges localized at crystal defect accumulations. In accordance with this assumption an anomalous dependence of mobility on temperature has also been found. The existence of localized space charge regions was further confirmed by the change of photo-voltage on scanning the film with a finely focused laser beam. First characteristics of MOST's on relatively thick silicon films on spinel do not show any remarkable difference from that of transistors on bulk silicon, both having been produced by applying the usual MOS technology.

Mechanical and electrical properties of epitaxial silicon films on spinel

An integrated structure for bi-directional optical fiber transmission has a laser diode, a photodetector, and a bi-directional optical waveguide integrated on a common substrate, the waveguide guiding radiation from the laser diode out of the structure and directing incoming radiation of a different wavelength through the structure to the photodetector. The structure also includes a passive optical component cooperating with the strip waveguide for substantially isolating the radiation propagated in one direction in the waveguide from the laser diode, and substantially isolating the radiation propagated in the opposite direction in the waveguide from the photodetector. A method for manufacturing this structure includes essentially growing two epitaxial multi-layer structures spaced from each other and covering selected portions of the substrate constituting the laser diode and the photodetector, with the strip waveguide extending therebetween.

Integrated structure for bi-directional optical fiber transmission

Structure, especially for bidirectional optical signal transmission, and method for manufacturing such a structure

Monolithisch integrierter WDM-Demultiplexmodul, bei dem auf einem Substrat (1) aus InP ein Schichtwellenleiter (10) aus InGaAsP ausgebildet ist, auf den eine Fotodiode (31) aus InGaAs aufgebracht ist. is formed monolithically integrated WDM Demultiplexmodul, in which on a substrate (1) made of InP a wave guide layer (10) of InGaAsP, onto which a photodiode (31) is applied from InGaAs. Die Fotodiode (31) ist durch Leckwellenkopplung an den Schichtwellenleiter (10) optisch gekoppelt. The photodiode (31) optically coupled by leakage wave coupling to the film waveguide (10). In der Oberflache des Schichtwellenleiters (10) ist ein wellenlangenselektierendes Element (20) in Form eines Gitters ausgebildet. In the surface of the slab waveguide (10) is a wavelength selecting element (20) is in the form of a grid. Der Modul kann mit einem einzigen Epitaxieschritt hergestellt werden. The module can be produced with a single epitaxial step. Es werden auch Masnahmen zur Erhohung der Nebensprechdampfung des Moduls angegeben sowie eine Masnahme zur besseren Einkopplung von Strahlung in den Modui. measures to increase the crosstalk attenuation of the module are given as well as a measure to improve the coupling of radiation into the Modui.

Heinrich Dr. Schlötterer

Papers

Influence of the floating substrate potential on the characteristics of ESFI MOS transistors

Mechanical and electrical properties of epitaxial silicon films on spinel

Integrated structure for bi-directional optical fiber transmission

Structure, especially for bidirectional optical signal transmission, and method for manufacturing such a structure

Monolithically integrated WDM Demultiplexmodule and method of manufacturing such a module