An accurate method to extract specific contact resistivity using cross-bridge Kelvin resistors

The cross-bridge Kelvin resistor structure is used to extract true interfacial specific contact resistivity (ρc). Two-dimensional (2-D) simulations demonstrate that the sublinear behavior of the measured contact resistance versus contact area on a log-log plot is due to current crowding around the contact which results from the contact window size being smaller than the diffusion width. The effect is more pronounced for low values of ρc. Excellent agreement has been found between the simulations and measured data of contact resistances. An accurate value of ρchas been extracted for the case of PtSi to n⁺polysilicon contacts.     

Transport across a high—low barrier and its influence on specific contact resistivity of a metal—n-GaAs ohmic system

Thermionic emission is hypothesized as a mechanism of carrier transport across the high-low barrier of a metal-semiconductor (M-S) ohmic junction. The barrier resistance, based on this theory is calculated and combined with tunneling resistance of the M-S junction to evaluate specific contact resistivity of ohmic contact to n-GaAs. The theoretical results interpret the published experimental data convincingly and thus validate the proposed mechanism of thermionic emission.     

Folded gate—A novel logic gate structure

We propose a new logic gate structure which consists of two semiconducting layers separated by an insulator. The input electrode is a rectifying contact to the top conducting layer which acts as a channel of a switching field-effect transistor. The bottom conductive layer serves as a load. The conducting layers are connected and capacitively coupled. The top layer acts as a gate for the load element whereas the bottom layer acts as a second gate for the top conductive channel. This "folded" gate is a majority-carrier device which may be implemented using different technologies and materials. It allows a CMOS-like operation with a very low power consumption in the stable states, speed comparable or higher then the speed of conventional direct-coupled field-effect transistor logic (DCFL), and a larger voltage swing.     

A vertical Kelvin test structure for measuring the true pecific contact resistivity

A vertical Kelvin test structure, which can be used to measure the true specific contact resistivity of a metallization system, is proposed and studied. For this test structure, the driving current flows "vertically," thus the sheet resistance and current crowding effects are eliminated and measurement on the true specific contact resistivity becomes possible. Experimental works show that this test structure gives a more linear relation between resistance and contact area than the conventional six-terminal test structure.     

Specific contact resistivity measurement by a vertical Kelvin test structure

A vertical Kelvin test structure is used to measure the specific contact resistivity of the Al (1-percent Si)/Si and Al (1-percent Si)/TiSi2/Si contact system. For the vertical test structure, the driving current flows "vertically," thus the current crowdings and sheet resistance effects are eliminated and measurement on the true specific contact resistivity becomes possible. Experimental works show that results obtained by using this vertical structure are closer to the true specific contact resistivities than those obtained by using the conventional six-terminal Kelvin method. It is also found that Rsd, the sheet resistance directly underneath the contact pad, is much less than that of the conduction bar without the contact pad. A value of (1.17 ± 0.17) × 10^-7Ω . cm²specific contact resistivity is obtained for the Al (1-percent Si) /TiSi2(direct reaction) /Si system.     

Solar cell contact resistance—A review

An overview of ohmic contacts on solar cells is presented. The fundamentals of metal-semiconductor contacts are reviewed, including the Schottky approach, Fermi level pinning by surface states, and the mechanisms of thermionic emission, thermionic/field emission, and tunneling for current transport. The concept of contact resistance is developed and contact resistance data for several different contact materials on both silicon and gallium arsenide over a range of doping densities are summarized. Finally, the requirements imposed by solar cells on contact resistance are detailed.     

A novel 0.1 μm MOSFET structure with inverted sidewall andrecessed channel

To solve the problems of trade-off between the short channel effect and the performance enhancement of sub-quartermicrometer MOSFETs, we have developed a recessed channel MOSFET structure called ISRC (Inverted-Sidewall Recessed-Channel). The oxide thickness is 4 nm and the effective channel length is 0.1 μm, which is the smallest Si-MOSFET ever reported in the recessed channel structures. The maximum saturation transconductance at V_D=2 V is 446 mS/mm for the 0.1 μm n-channel device. The threshold voltage roll-off is kept within 64 mV when the gate length varies from 1.4 μm to 0.1 μm and good subthreshold characteristics are achieved for 0.1 μm channel device     

Simuron—A novel dynamic memory device

The Simuron (simulated neuron) is a distributed active element analogous to the neuron and has learning and oblivious mechanisms. Like the neuristor, it can be coupled by two types of junctions. This letter proposes frequency memory and logical memory circuits using the Simuron.     

A further comment on "Determining specific contact resistivity from contact end resistance measurements"

The purpose of this comment is to contribute to a better understanding of the influence of lateral current crowding, sheet resistance, and interface pitting in the determination of the interface contact resistivity in four terminal resistor test patterns, for two different metallization schemes, i.e., 1Al/n⁺Si and (Al + 1.5-percent Si)/n⁺Si.     

Experimental verification of a novel electrical test structure formeasuring contact size

An electrical test structure that measures contact size without reliance on contact resistivity measurements is presented. A comparison with SEM photographs shows that the structure measures contact size in the range of 1.0 μm with a resolution close to 0.2 μm. Results are shown for measuring the size of contacts to poly, but the concept should also apply to measuring contacts to active areas, or contacts between two metal layers. In addition to the size of contacts to poly, the structure presented also measures the linewidth and sheet resistance of the poly, and misalignment of contacts to poly. It consists of a digital vernier of 72 samples and a linewidth structure and is implemented without active circuitry in a 2 by 12 pad array using three masking levels     

Current crowding and misalignment effects as sources of error in contact resistivity measurements—Part II: Experimental results and computer simulation of self-aligned test structures

In this work we show that an accurate and straightforward extraction of the contact resistivity from contact resistance data can be achieved using properly designed self-aligned test patterns. In this way, the parasitic effects are minimized and the contact resistivity can be derived using simple one-dimensional models as confirmed by our computer simulation. Experimental results obtained in self-aligned structures are presented for Al/CoSi2/n⁺Si and Al-Si/n⁺Si contacts.     

HPSAC—A silicided amorphous-silicon contact and interconnect technology for VLSI

A high-performance silicided amorphous-silicon contact and interconnect technology (HPSAC) for VLSI is presented. In this novel scheme, a patterned silicide layer is used to form self-aligned contacts to the source/drain regions, as well as to interconnect devices. The fabrication procedures and some key processing techniques are described, Experimental results on n^-and p^-channel MOSFET's fabricated with HPSAC technology are presented. The performance improvement due to reduction of parasitic capacitance and resistance is discussed.     

Acoustic sounding—A new approach to the study of atmospheric structure

Short pulses of acoustic energy at a carrier frequency of 950 Hz were beamed upwards from an array of loudspeakers. The energy which was backscattered from the random fluctuations of temperature within the turbulent regions of the lower 300 meters of the atmosphere was received on the same array and recorded on a facsimile receiver. The acoustic echoes were calibrated against temperature and wind data obtained from sensing elements fitted on a tower 75 meters high, 500 meters away from. the acoustic sounder. Sounding records, together with temperature and wind data, are presented for thermal plumes, breaking waves, and the formation and breakup of a radiation inversion. The usefulness of the acoustic sounding technique in continuously monitoring the intensity of small-scale temperature inhomogeneities in the lower atmosphere is emphasized. Future developments are outlined.     

The factorization problem—A survey

The problem of factoring a positive Hermitian operator into the product of a causal operator and its adjoint is reviewed. Three classes of factorization are studied, miniphase factorization, regular factorization, and special factorzation. The former always exists, and a complete representation thereof is obtained in terms of the properties of reproducing kernel spaces. The regular factorization does not exist, in general, and its existence theroy is shown to be equivalent to the unitary equivalence problem of classical operator theory. Finally, an existence and uniqueness theorem for special factors is formulated in terms of certain Cauchy integrals and is shown to be closely related to Wiener-Hopf theory.     

The effect of lateral current spreading on the specific contact resistivity in D-resistor Kelvin devices

The effects of lateral current spreading on the determination of ohmic contact resistivity when Using Kelvin devices with a D-resistor layout are studied by numerical simulation and experimental measurements. Simulations show that the extracted contact resistivity can be higher or lower than the actual resistivity. The extracted contact resistivity is found to be a strong function of the geometrical layout, the semiconductor sheet resistance, and the actual contact resistivity. Futhermore, it is shown that the actual contact resistivity cannot be determined below some minimum value and the effect of misalignment during processing is shown to produce significant errors. Good agreement with the experiment is found for As-implanted ohmic contacts to Si. Guidelines for the design, processing, and evaluation of D-resistor Kelvin devices are presented.     

The transistor—A new semiconductor amplifier

This article describes the construction, characteristics, and behavior of the newly discovered device, the transistor. Used as a semiconductor amplifier, it works on an entirely different principle and is capable of performing the same tasks now done by the vacuum tube triode.     

The ryotron—A new cryogenic device

This paper describes a cryogenic electronic variable inductor called the ryotron. This device may be represented as a dc-isolated two-port network useful for both digital and analog circuits. Included are 1) general introduction, 2) the principle of operation, 3) experimental results, 4) device applications, and 5) discussion.     

The scanistor—A solid-state image scanner

Scanistors form a new class of semiconducting devices which perform image scanning or dissection by reason of a novel electronic method of commutating a single output terminal to any preselected illuminated portion of the device. The selection is uniquely determined by a voltage applied across two terminals of the device. The present investigation is concerned with a strip-shaped unit called the multijunction scanistor which is comprised of a linear, integrated-circuit array of photodiodes. This device provides an output either as a sequence of pulses which represent spatial sampling of a line image at a discrete number of points, or as an analog wave-form which is a linear transformation of the line image. A theory appropriate to scanners of this type is developed and applied to the multijunction scanistor for purposes of design and analysis. A time-dependent circuit analysis of a model of the scanistor is carried out and tested experimentally. It provides an understanding of the upper limits to the scanning rate set by junction capacitance. Experimental units designed according to theory are tested for their sine-wave response, uniformity of output, sensitivity, and scanning linearity. These units are shown to give good results when used to scan a typewritten document for facsimile display on an oscilloscope.