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Properties of epitaxial silicon layers on buried silicon nitride produced by ion implantation
World Abstracts on Microelectronics and Reliability induced carbon enrichment of the surface layer of iron and silicon after nitrogen ion implantation has been observed by AES and XPS combined with ion milling. In the range of ion doses implanted (4.8x 1016-3x 1017N atoms cm -2) the carbon contamination level in a thin sub-surface layer has been found to be essentially independent of the dose. A graphite-like form of carbon was found on the surface of both iron and silicon while, in the sub-surface layer, a carbide-like form ofcarbon in the iron samples was observed.
Electrical characterization of p+/nshallow junctions obtained by boron implantation into preamorphized silicon. E. LANDI and S. SOLMI. Solid-St. Electron. 29(11), 1181 (1986). Electrical characteristics of p÷/n diodes obtained by boron implantation into amorphous silicon layers formed by a prior implantation of Si ÷ ions are presented. The absence of channeling phenomena (preamorphization), the low boron implantation energy (10-20 keV), and the post-implantation low temperature anneal (600-10000C) or rapid anneal (electron beam) allow to obtain very shallow junctions (0.1-0.3 gin). Particular attention is given to analyse effects on the reverse diode current from dislocation loops which are formed at the amorphous-crystalline interface during annealing. If the dislocation loops are outside of the space charge region, the diodes show a low leakage current ( ~ 1 nA cm-2 at - 1 v), but the reverse current increases strongly when this residual damage falls into the depleted nregion. Experimental I-V characteristics are in excellent agreement with a numerical simulation, which takes into account a strong lifetime degration associated with the dislocation loops. The selectivity of poly Si and SiO2 etching using a negative dc biasing of powered electrode. JOZEE BRCKA and RUDOLF HARMAN. Vacuum 36(7--9), 531 (1986). In this work the etch rates of poly Si and SiO 2 in CCI4 plasma were investigated. The etch process in a planar flat-bed reactor was examined with the aim of controlling the selectivity by an external dc negative bias voltage. The pressure and rf current dependences of poly Si and SiO z etch rates were obtained. For typical etch conditions, etch rates of about 120 nm min -1 and 25 nn min-1 for poly Si and SiO2, respectively, have been achieved. The selectivity did not exceed a value of 5. It was shown the etch rate ratio (poly Si:SiO2) was dependent on dc voltage applied to the powered electrode. In order to achieve higher and more reproducible selectivity it is necessary to use a conducting bottom electrode and enhance the process chemistry. Application of ion beam techniques for amorphization and analysis of thin films. G. LINKER. Vacuum 36(7-9), 493 (l 986). High dose ion implantation or irradiation of metals may lead to amorphization depending on the ion-target system under consideration. Some advantages of the application of ion beam techniques in amorphization studies are outlined. The experimental techniques used in thin film amorphization studies like film preparation, ion bombardment, backscattering and thin film X-ray diffraction analysis are described. Examples of amorphization studies are given for irradiation of elements (Ga) and compounds (Nb3Ir) and binary alloys produced by successive implantation (B and P in Nb, B in Mo). The continuous observation of the amorphization process by implantation allows a direct comparison with theoretical amorphization models. The examples show that strain accumulation appears as an important prerequisite for the transition into the amorphous state. The use of ion beams in thin film deposition. D. G. ARMOUR, P. BAILEY and G. SHARPLES. Vacuum 36(11/12), 769 (1986). Bombardment of growing films with energetic ions has become an established method of improving or, at least changing, many of the important structural, optical and electrical properties of thin films. Although the techniques
795
used to achieve the desired bombardment vary quite dramatically from high pressure plasma processing to irradiation with mono-energetic, mass-analysed ion beams in ultrahigh vacuum environments, the ion-surface interaction processes which lead to the deposition, removal and relocation of surface and near surface atoms form the basis of all the ion assisted processing techniques. The purpose of this paper is to review the rates of penetration and entrapment, recoil particle and defect generation, and sputtering processes in determining the formation kinetics and characterization of films deposited under ion bombardment conditions. Consideration of these processes enables the deposition parameters to be optimized from the point of view of the relative contributions of energy and material deposition and the design and performance of experimental systems capable of realizing the specified conditions will be discussed.
The contribution of SIMS to the characterization of III-V semiconductor layers grown by molecular beam epitaxy. G. D. T. SP1LLAR and D. A. ANDREWS. Vacuum 36(11/12), 991 (1986). Secondary ion mass spectrometry (SIMS) is widely used in the analysis of semiconductor layers and devices, such as those fabricated by molecular beam epitaxy (MBE). The need for controllably-doped, high purity, single crystal layers with thicknesses from over a lam down to a few atomic layers, places considerable demands on the growth technique and on the assessment methods used to characterize the layers. This paper describes how SIMS is being used for trace level profiling of dopants and impurities and for matrix element profiling in MBE layers. The profiling of very thin layered (multi-quantum well) structures is also considered. Laser exitation of ion beams. REINHOLD HALL1N, ARNE ARNESEN, CARL NORDLING, OLLE VOGEL and ANDERS WANNSTROM. Vacuum 36(11/12), 939 (1986). During the last decade laser excitation of fast ion beams has become a powerful tool in atomic and molecular spectroscopy. The high velocity of the ions makes it possible to perform accurate lifetime measurements of excited states in a geometry with crossed ion and laser beams. The selective laser excitation avoids the problem of cascades from upper levels. Recent lifetime measurements of singly ionized atoms performed in our laboratory are discussed, as well as other possible uses of the high time resolution in crossed beam experiments. Very high spectral resolution (sub-Doppler) measurements of hyperfine structure and isotope shifts with collinear laser and ion beams are also reviewed. Properties of epitaxial silicon layers on buried silicon nitride produced by ion implantation. W. SKORUPA, U. KREISSIG,H. OERTEL and H. BARTSCH. Vacuum 36(11/12), 933 (1986). Buried silicon nitride layers were produced in (100) silicon substrates by implanting 330keV, 14N+ ions with doses in the range 0.8-1.2×1018cm -2 at target temperatures of 500°C. The substrates were then annealed by furnace and flash lamp and epitaxial silicon layers were grown. Crystal defects of the epitaxial layers are dislocations with a density of ~ 108cm -2 as revealed by cross-sectional TEM. No influence of the defects on the electrical properties of the SiO2-Si interface of MOS capacitors was found. Despite of the high defect density the generation lifetime of the minority carriers is relatively high and in the range 20-200ps. These values are at least one order of magnitude higher as compared to other SOl technologies. Preparation and thermal conductivity of doped semiconductors. D. M. ROWEand C. M. BHANDARI.Prog, Crystal Growth Characterisation 13, 233 (1986). Semiconductor material to which has been added carefully controlled amounts of impurities (dopant) is the basis of modern electronics. A parameter which has to be taken into account when assessing the suitability of a semiconductor for a parti-
Electrical characterization of p+/nshallow junctions obtained by boron implantation into preamorphized silicon. E. LANDI and S. SOLMI. Solid-St. Electron. 29(11), 1181 (1986). Electrical characteristics of p÷/n diodes obtained by boron implantation into amorphous silicon layers formed by a prior implantation of Si ÷ ions are presented. The absence of channeling phenomena (preamorphization), the low boron implantation energy (10-20 keV), and the post-implantation low temperature anneal (600-10000C) or rapid anneal (electron beam) allow to obtain very shallow junctions (0.1-0.3 gin). Particular attention is given to analyse effects on the reverse diode current from dislocation loops which are formed at the amorphous-crystalline interface during annealing. If the dislocation loops are outside of the space charge region, the diodes show a low leakage current ( ~ 1 nA cm-2 at - 1 v), but the reverse current increases strongly when this residual damage falls into the depleted nregion. Experimental I-V characteristics are in excellent agreement with a numerical simulation, which takes into account a strong lifetime degration associated with the dislocation loops. The selectivity of poly Si and SiO2 etching using a negative dc biasing of powered electrode. JOZEE BRCKA and RUDOLF HARMAN. Vacuum 36(7--9), 531 (1986). In this work the etch rates of poly Si and SiO 2 in CCI4 plasma were investigated. The etch process in a planar flat-bed reactor was examined with the aim of controlling the selectivity by an external dc negative bias voltage. The pressure and rf current dependences of poly Si and SiO z etch rates were obtained. For typical etch conditions, etch rates of about 120 nm min -1 and 25 nn min-1 for poly Si and SiO2, respectively, have been achieved. The selectivity did not exceed a value of 5. It was shown the etch rate ratio (poly Si:SiO2) was dependent on dc voltage applied to the powered electrode. In order to achieve higher and more reproducible selectivity it is necessary to use a conducting bottom electrode and enhance the process chemistry. Application of ion beam techniques for amorphization and analysis of thin films. G. LINKER. Vacuum 36(7-9), 493 (l 986). High dose ion implantation or irradiation of metals may lead to amorphization depending on the ion-target system under consideration. Some advantages of the application of ion beam techniques in amorphization studies are outlined. The experimental techniques used in thin film amorphization studies like film preparation, ion bombardment, backscattering and thin film X-ray diffraction analysis are described. Examples of amorphization studies are given for irradiation of elements (Ga) and compounds (Nb3Ir) and binary alloys produced by successive implantation (B and P in Nb, B in Mo). The continuous observation of the amorphization process by implantation allows a direct comparison with theoretical amorphization models. The examples show that strain accumulation appears as an important prerequisite for the transition into the amorphous state. The use of ion beams in thin film deposition. D. G. ARMOUR, P. BAILEY and G. SHARPLES. Vacuum 36(11/12), 769 (1986). Bombardment of growing films with energetic ions has become an established method of improving or, at least changing, many of the important structural, optical and electrical properties of thin films. Although the techniques
795
used to achieve the desired bombardment vary quite dramatically from high pressure plasma processing to irradiation with mono-energetic, mass-analysed ion beams in ultrahigh vacuum environments, the ion-surface interaction processes which lead to the deposition, removal and relocation of surface and near surface atoms form the basis of all the ion assisted processing techniques. The purpose of this paper is to review the rates of penetration and entrapment, recoil particle and defect generation, and sputtering processes in determining the formation kinetics and characterization of films deposited under ion bombardment conditions. Consideration of these processes enables the deposition parameters to be optimized from the point of view of the relative contributions of energy and material deposition and the design and performance of experimental systems capable of realizing the specified conditions will be discussed.
The contribution of SIMS to the characterization of III-V semiconductor layers grown by molecular beam epitaxy. G. D. T. SP1LLAR and D. A. ANDREWS. Vacuum 36(11/12), 991 (1986). Secondary ion mass spectrometry (SIMS) is widely used in the analysis of semiconductor layers and devices, such as those fabricated by molecular beam epitaxy (MBE). The need for controllably-doped, high purity, single crystal layers with thicknesses from over a lam down to a few atomic layers, places considerable demands on the growth technique and on the assessment methods used to characterize the layers. This paper describes how SIMS is being used for trace level profiling of dopants and impurities and for matrix element profiling in MBE layers. The profiling of very thin layered (multi-quantum well) structures is also considered. Laser exitation of ion beams. REINHOLD HALL1N, ARNE ARNESEN, CARL NORDLING, OLLE VOGEL and ANDERS WANNSTROM. Vacuum 36(11/12), 939 (1986). During the last decade laser excitation of fast ion beams has become a powerful tool in atomic and molecular spectroscopy. The high velocity of the ions makes it possible to perform accurate lifetime measurements of excited states in a geometry with crossed ion and laser beams. The selective laser excitation avoids the problem of cascades from upper levels. Recent lifetime measurements of singly ionized atoms performed in our laboratory are discussed, as well as other possible uses of the high time resolution in crossed beam experiments. Very high spectral resolution (sub-Doppler) measurements of hyperfine structure and isotope shifts with collinear laser and ion beams are also reviewed. Properties of epitaxial silicon layers on buried silicon nitride produced by ion implantation. W. SKORUPA, U. KREISSIG,H. OERTEL and H. BARTSCH. Vacuum 36(11/12), 933 (1986). Buried silicon nitride layers were produced in (100) silicon substrates by implanting 330keV, 14N+ ions with doses in the range 0.8-1.2×1018cm -2 at target temperatures of 500°C. The substrates were then annealed by furnace and flash lamp and epitaxial silicon layers were grown. Crystal defects of the epitaxial layers are dislocations with a density of ~ 108cm -2 as revealed by cross-sectional TEM. No influence of the defects on the electrical properties of the SiO2-Si interface of MOS capacitors was found. Despite of the high defect density the generation lifetime of the minority carriers is relatively high and in the range 20-200ps. These values are at least one order of magnitude higher as compared to other SOl technologies. Preparation and thermal conductivity of doped semiconductors. D. M. ROWEand C. M. BHANDARI.Prog, Crystal Growth Characterisation 13, 233 (1986). Semiconductor material to which has been added carefully controlled amounts of impurities (dopant) is the basis of modern electronics. A parameter which has to be taken into account when assessing the suitability of a semiconductor for a parti-