Showing papers by "Herman Maes published in 1993"

On the geometric component of charge-pumping current in MOSFETs

Abstract: A simple method of unambiguously determining the presence of any geometric component in a charge-pumping measurement by collecting this component at another node via a nearby junction is presented. With the method it has been possible to study the dependence of geometric components on device dimensions and various experimental conditions with unprecedented sensitivity. By effectively separating the two current contributions, this method can at the same time be used to reduce geometric components in the regular charge-pumping signal, thereby increasing the accuracy of the various implementations of the charge pumping (CP) technique. >

HIM0S-a high efficiency flash E/sup 2/PROM cell for embedded memory applications

Abstract: A flash E/sup 2/PROM device which is programmed with a highly efficient hot-electron injection mechanism is described. This high-injection MOS (HIMOS) device combines a very high programming speed at 5-V-only operation with a low development entry cost, which renders it highly attractive for embedded memory applications. The HIMOS concept exhibits complete soft-write immunity and the possibility of overerasure without causing any problem in a memory architecture. It is shown that this device can also operate with a 3.3-V voltage supply, which is of a major importance for the next generation of submicron flash E/sup 2/PROM technologies. >

Integration of CMOS-electronics and particle detector diodes in high-resistivity silicon-on-insulator wafers

Abstract: A new approach to monolithic pixel detectors, based on silicon on insulator (SOI) wafers with high resistivity substrate, is being pursued by the CERN RD19 collaboration. The fabrication methods and the results of the electrical evaluation of the SOI-MOSFET devices and of the detector structures fabricated in the bulk are reported. The leakage current of the high-resistivity PIN-diodes is kept of the order of 5 to 10 nA/cm/sup 2/. The SOI preparation processes employed-SIMOX (separation by implantation of oxygen) and ZMR (zone melting recrystallization)-produce working electronic circuits, and appear to be compatible with the fabrication of detectors of suitable quality. >

Method for programming a semiconductor memory device

Abstract: A programmable EEPROM cell structure consisting in a split-gate structure in series with a coupling capacitor between the floating gate and an additional program gate in order to provide enhanced injection efficiency. The electron injection is controlled by a control gate at the source side. The area of the coupling capacitor is selected with a substantial coupling factor to a high voltage onto the floating gate during programming so as to produce hot-electron injection at the split point in the channel region between the control gate and the floating gate. Submicrosecond programming at a 5 V drain voltage can thereby be achieved.

Double snapback in SOI nMOSFETs and its application for SOI ESD protection

Abstract: Double snapback in silicon-on-insulator (SOI) nMOSFETs is reported. An extensive experimental analysis of this phenomenon and a tentative model are presented. It is shown that this double-snapback phenomenon offers a basis for an electrostatic discharge (ESD) protection concept for SOI technologies. >

Direct and post-injection oxide and interface trap generation resulting from low-temperature hot-electron injection

Abstract: We have studied direct and post‐injection trap generation, induced by low‐temperature (∼77 K) hot‐electron injection. At these temperatures the main degradation mechanism, attributed to the release, migration, and subsequent reaction of a hydrogenic species is inoperative, not only due to the suppressed release but also to the freeze‐out of the species motion. As a result, trap creation is strongly reduced as compared to room‐temperature injection. Additional interface traps are created during warmup following low‐temperature injection. Two post‐injection generation processes have been observed: a low‐temperature (120 K), bias‐independent process believed to be related to the migration of neutral atomic hydrogen released during stress, and a high‐temperature (250 K), negative‐bias enhanced process that apparently cannot be attributed to the migration of a species, but rather resembles the negative‐bias‐temperature instability phenomenon.

Single poly cell as the best choice for radiation-hard floating gate EEPROM technology

Abstract: The total dose radiation response of two classes of floating gate nonvolatile memory devices is examined. While the hardness of commonly studied double polysilicon cells is restricted to a few kilorads, devices having only one polysilicon layer are shown to be much more radiation-hard. This is mainly due to the thinner oxide that can be used in the coupling capacitor of such cells. It is also shown that the contribution of the field oxide regions, present under the floating gate of the cells, is of major importance for their radiation response. The programming behavior of the devices is shown to remain fairly unaffected by the ionizing radiation. >

Explosive crystallization of amorphous Si3N4 films on silicon during silicon laser melting

Abstract: The explosive crystallization of Si3N4 layers deposited on silicon samples during laser melting of the silicon is investigated. The crystallization threshold is defined as the minimal laser‐beam power to start crystallization. The precipitate‐initiator hypothesis which states that the explosive crystallization is initiated by the formation of Si3N4 precipitates in the molten zone is formulated. Based on this hypothesis the dependency of the crystallization threshold on the scan conditions and the sample structure can be completely and consistently explained. Methods to prevent crystallization are formulated.

Optimization of a submicron HIMOS Flash E 2 PROM cell for implementation in a virtual ground array configuration

Abstract: This paper describes the implementation of High Injection MOS Flash E2PROM devices in a 0.7?m CMOS technology. The cell has been optimized from the point of view of cell area as well as programming speed. A virtual ground array configuration is proposed to scale the cell area down to the range of 15?m2. The device is programmed in a few hundreds of nanoseconds at 5V-only operation and in 100?s at 3.3V-only operation. The combination of these results with a low development entry cost shows that the HIMOS cell is a viable candidate for fast-programmable 5V-only (and 3.3V-only) medium-to-high density Flash memories.

Comparative study of hot-carrier degradation in p + and n + poly p-MOSFET's of a 0.5 μm CMOS technology

Abstract: In this paper, the degradation of p+ and n+ poly p-MOSFET devices of a 0.5 μm technology is studied in detail. The former devices exhibit intrinsically a better hotcarrier hardness. The difference in hot carrier behaviour between the p+ and n+ poly transistors is attributed mainly to the short channel effect. The p+ poly devices are therefore more suited for the realisation of deep submicron devices.

Variation of Local Mechanical Stress During the Different Processing Steps of Ic-Isolation: a Micro-Raman Spectroscopy Study

Abstract: Local mechanical stress introduced in the silicon substrate during the successive steps of poly-buffered local isolation of MOS integrated circuits is studied with micro-Raman spectroscopy. It is shown that the magnitude and the local variation of the stress is highly affected by the different processing steps. After deposition of the nitride mask, the stress can be described as caused by an edge-force. Field oxidation reduces the mask-induced stress but introduces thermal stress from the field oxide. Also the formation of the bird’s beak gives rise to additional local tensile stress, especially at the tip of the bird’s beak. Removal of the nitride mask results in a partial relaxation: the stress caused by the bird’s beak relaxes. In this last stage of the isolation process, the stress image is mostly determined by the field oxide.

Raman spectroscopy measurement of local stress induced by LOCOS and trench structures in the silicon substrate

Abstract: Micro-Raman spectroscopy is used to study local mechanical stress at trench-LOCOS structures. At the trench edges the stress is compressive. The local stress surrounding trench and LOCOS is highly affected when both structures are located close to each other. The stress picture obtained from both planar and cross-sectional experiments agrees very well with stress predicted by finite element calculations.

The influence of mechanical stress on hot-carrier degradation in MOSFET's

Abstract: Non-uniform hot-carrier degradation in n-channel polycide-gate MOSFET's with different thicknesses of the poly-Si film, and in p-channel polycide-gate MOSFET's with TiSi 2 - or CoSi 2 -gate-silicide, is studied. The n-MOSFET's with the thinnest poly-Si film, show an increased interface trap generation, while the influence of the gate-silicide material on the degradation behaviour of the p-MOSFET's is found to be very small. The results are evaluated in terms of the effect of mechanical stress on the degradation characteristics: favourable for compressive mechanical stress and unfavourable for tensile stress. A correlation with stress measurements by micro-Raman spectroscopy is made.

Stress in Thin Micro-Zone-Molten Crystalline Silicon Films on Solid Substrates

Abstract: Thin crystalline silicon films supported by a substrate can be obtained by zone melting recrystallization. In this study a model for the stress generated in the substrate during this process and for the final stress in the thin silicon film is presented. For a given structure the stress is determined by the preheating temperature only. In the substrate compressive stress is induced by the localized heating inherent to the ZMR process. The moving heater introduces a tensile stress component in the final SOI film. If a line shaped heat source is used, this tensile stress is non-equi-axed. The presented model can account for a wide variety of reported experimental results.