- Email: [email protected]
7338. Growth mechanism and morphology of semiconducting FeSi2 films
Classified abstracts 7334-7342
34 7334. Thermal conductivity and diffusivity of a thin film SiO2-Si3-N 4 sandwich system The thermal conductivity, diffusivity and emissivity of a sandwich system of low pressure chemically vapour-deposited SiO 2 and Si3N4 films (200 nm of Si aN 4 followed by 400 nm of SiO 2 and 200 nm of Si 3N 4) are investigated in the temperature range 80400 K. The steady state and dynamical measuring principles are described and the results are represented and discussed. F Vrlklein, Thin Solid Films, 188, 1990, 27-33. 34 7335. Interdiffusion and reaction in (Cr-Si)/AI and (Cr~Si-O)/AI thin film systems The interactions in the (C~Si)/A1 and ( C ~ S i ~ ) / A 1 film systems, as a result of thermal load, were investigated with regard to the electrical properties and the metallurgical stability. The layers were deposited on Si/SiO2 and NaC1 substrates using a reactive de, magnetron sputtering technique in vacuum sequence. The film systems were characterized by means of secondary-ion mass spectrometry and transmission electron microscopy transmission electron diffraction. The electrical resistance and its temperature coefficient and the reflection coefficient were measured. In both film systems the film components had already been intermixed during deposition. In the (C~Si)/AI system the amorphous Cr-Si layer begins to crystallize at a temperature of 260°C, thereby forming CrSi2 and giving rise to strong interdiffusion at 400°C. The thermal stability in the (C~Si-O)/A1 system is improved by the oxygen incorporated. The formation of CrSi2 is then retarded to 450-550°C as is the beginning of intensive interdiffusion. Upon heat treatment the two film systems show local defects which are caused by different mechanisms. The changes in physical properties observed are attributed to the chemical and structural alterations in the film systems. K-H B~ither et al, Thin Solid Films, 188, 1990, 67 83. 34 7336. Study of Co-Cr films for perpendicular magnetic recording using nuclear magnetic resonance A 59Co nuclear magnetic resonance measurement and a transmission electron microscope observation are utilized to investigate the compositional distribution of Co Cr films with and without heat treatment. The spin-echo spectra of evaporated films are found to be entirely different from those of C o ~ r alloy powders. The spectra o f films comprise a very complicated hyperfine field distribution and the resonant frequencies are much higher than those of powder samples, implying the existence of various kinds of segregation regions typical of a film. Chrysanthemumlike patterns, which disappear with heat treatment, are also observed for chemically etched films. This disappearance is accompanied by the disappearance of the highest-frequency resonant line. K Yoshida et ai, J Appl Phys, 68, 1990, 705 712. 34 7337. lnterfacial reaction of Ta- and Si-rich tantalum silicides with Si suhstrate Properties of tantalum silicide (TaSix) films deposited from a TaSi x composite target are studied. Ta-rich (Si/Ta atom ratio, x = 1.83) and Sirich (x = 2.60) films are deposited by dc magnetron sputtering on Si substrates. In Ta-rich films a silicidation reaction occurs with annealing above 700°C. As a result, Si composition, x, and silicide film thickness increases with consuming Si substrate. Stress changes abruptly from tensile to compressive with this reaction. This stress changes leads to peeling in the Ta-rich film during the silicidation reaction. In Si-rich films, excess Si precipitates at the interface at 750"C. However, the stress changes more gently in the Si-rich film and a more uniform TaSi2/Si interface is formed. Therefore, peeling can be avoided in Si-rich films. T Hara and M Murota, J Appl Phys, 68, 1990, 183 188. 34 7338. Growth mechanism and morphology of semieonducting FeSi2 films Semiconducting fl-FeSi 2 films grown on (100) -oriented Si and on (1T02) sapphire substrates are investigated by X-ray diffraction, Nomarski optical microscopy, stress, and surface roughness measurements. As a result of an exothermic, nucleation controlled reaction, we observe a characteristic ring-shaped surface pattern of the silicide. Surface rough-
ness and stress in fl-FeSi2 are less pronounced for films grown at lower temperatures and cooling rates. Sapphire substrates result in smoother surfaces than Si due to the match of the thermal expansion coefficient of sapphire to the silicides. C A Dlmitriadis and J H Werner, J Appl Phys, 68, 1990, 9346. 34 7339. Improvement of oxide quality by rapid thermal annealing Rapid thermal processing as a post-oxidation annealing (POA) process is of considerable influence on the quality of thin thermal oxides. The number of defect-related oxide failures is reduced, together with a slight reduction of the intrinsic oxide quality, but to a degree that is of no importance as regards reliability aspects. According to our investigations, it is important that POA is performed after poly-Si deposition and doping, whereas POA after poly-Si patterning is found to be an undesirable process. Infrared spectroscopy indicates stress relaxation caused by the POA treatment, but no change of the SiO2/Si-interface roughness could be observed by high-resolution electron microscopy. This relaxation process was accompanied by the creation of electron traps. Constant-current investigations indicated an enhanced electron trapping in the oxides after POA. This electron trapping increased with increasing POA temperature. The reduced defect-related oxide failures after POA are attributed to a retarded runaway of the injection current by negative space charges. H Wendt et al, JAppl Phys, 67, 1990, 7531 7535.
35. ION A N D PLASMA ETCHING 35 7340. Evaluation of dry etch processes with thermal waves Thermal wave analysis of plasma etching damage in the processing of trench capacitors is discussed. This rapid and reliable technique can be used to assess damage during processing and predict the electrical performance of fully-processed D R A M s M Engelhardt, Solid St Technol, 33, 1990, 151-156. 35 7341. Pattern marking on synthetic diamond film by Penning discharge sputtering Method and apparatus to perform micro-etching and micro-inlay of patterns and numericals on synthetic diamond films by Penning discharge sputtering has been developed and evaluated. In this apparatus, selection of etching and inlay modes are made by a change of anode position. In etching mode, etching beam originates in a Penning discharge space and is guided through a duct in order to reach the diamond film surface covered with a pattern mask and then forms an etching pattern on the surface. After the etching is made, a new position of the anode is selected for the inlay process and the metal atoms that sputtered from the cathode surface through the duct deposit on the previously etched portion on the diamond film. A 5.3 #m thick diamond film formed by microwave plasma CVD. A fiat dish-shaped etching of 2.5 mmtk and a same size inlay with gold were made with a mask having 2.5 mm~b hole and gold cathodes. In this case, etching rate of diamond film is 0.07~3.12/zm min t and deposition rate of gold 0.06 #m min ~. By the same technique, etching and gold inlay shaped after the numeral '5' with 120 #m in width and 180/~m in length was produced. T Sugita et al, Vacuum, 41, 1990, 1371-1373. 35 7342. Influence of the surface electron processes on the kinetics of silicon etching by fluorine atoms The model of silicon etching by fluorine atoms is presented. It is shown that the dielectric SiFx film formed on the surface plays an important part in the etching. As a consequence of high heat of adsorption for fluorine atoms on this film its penetration under the surface by thermal activation is difficult. A specific mechanism explaining the origin of the electric field in the film is proposed. The process of electric field formation is connected with valence electrons tunneling from silicon to adsorbed fluorine. The analysis of the electron processes in the S i ~ i F x F system results in non-linear equations which can be used to calculate the electric field strength and etch rate in a stationary regime. In the proposed model non-activated fluorine penetration into the SiFx film is provided and essential experimental results can be explained. Yu E Babanov et al, Vacuum, 41, 1990, 902-905. 587
34 7334. Thermal conductivity and diffusivity of a thin film SiO2-Si3-N 4 sandwich system The thermal conductivity, diffusivity and emissivity of a sandwich system of low pressure chemically vapour-deposited SiO 2 and Si3N4 films (200 nm of Si aN 4 followed by 400 nm of SiO 2 and 200 nm of Si 3N 4) are investigated in the temperature range 80400 K. The steady state and dynamical measuring principles are described and the results are represented and discussed. F Vrlklein, Thin Solid Films, 188, 1990, 27-33. 34 7335. Interdiffusion and reaction in (Cr-Si)/AI and (Cr~Si-O)/AI thin film systems The interactions in the (C~Si)/A1 and ( C ~ S i ~ ) / A 1 film systems, as a result of thermal load, were investigated with regard to the electrical properties and the metallurgical stability. The layers were deposited on Si/SiO2 and NaC1 substrates using a reactive de, magnetron sputtering technique in vacuum sequence. The film systems were characterized by means of secondary-ion mass spectrometry and transmission electron microscopy transmission electron diffraction. The electrical resistance and its temperature coefficient and the reflection coefficient were measured. In both film systems the film components had already been intermixed during deposition. In the (C~Si)/AI system the amorphous Cr-Si layer begins to crystallize at a temperature of 260°C, thereby forming CrSi2 and giving rise to strong interdiffusion at 400°C. The thermal stability in the (C~Si-O)/A1 system is improved by the oxygen incorporated. The formation of CrSi2 is then retarded to 450-550°C as is the beginning of intensive interdiffusion. Upon heat treatment the two film systems show local defects which are caused by different mechanisms. The changes in physical properties observed are attributed to the chemical and structural alterations in the film systems. K-H B~ither et al, Thin Solid Films, 188, 1990, 67 83. 34 7336. Study of Co-Cr films for perpendicular magnetic recording using nuclear magnetic resonance A 59Co nuclear magnetic resonance measurement and a transmission electron microscope observation are utilized to investigate the compositional distribution of Co Cr films with and without heat treatment. The spin-echo spectra of evaporated films are found to be entirely different from those of C o ~ r alloy powders. The spectra o f films comprise a very complicated hyperfine field distribution and the resonant frequencies are much higher than those of powder samples, implying the existence of various kinds of segregation regions typical of a film. Chrysanthemumlike patterns, which disappear with heat treatment, are also observed for chemically etched films. This disappearance is accompanied by the disappearance of the highest-frequency resonant line. K Yoshida et ai, J Appl Phys, 68, 1990, 705 712. 34 7337. lnterfacial reaction of Ta- and Si-rich tantalum silicides with Si suhstrate Properties of tantalum silicide (TaSix) films deposited from a TaSi x composite target are studied. Ta-rich (Si/Ta atom ratio, x = 1.83) and Sirich (x = 2.60) films are deposited by dc magnetron sputtering on Si substrates. In Ta-rich films a silicidation reaction occurs with annealing above 700°C. As a result, Si composition, x, and silicide film thickness increases with consuming Si substrate. Stress changes abruptly from tensile to compressive with this reaction. This stress changes leads to peeling in the Ta-rich film during the silicidation reaction. In Si-rich films, excess Si precipitates at the interface at 750"C. However, the stress changes more gently in the Si-rich film and a more uniform TaSi2/Si interface is formed. Therefore, peeling can be avoided in Si-rich films. T Hara and M Murota, J Appl Phys, 68, 1990, 183 188. 34 7338. Growth mechanism and morphology of semieonducting FeSi2 films Semiconducting fl-FeSi 2 films grown on (100) -oriented Si and on (1T02) sapphire substrates are investigated by X-ray diffraction, Nomarski optical microscopy, stress, and surface roughness measurements. As a result of an exothermic, nucleation controlled reaction, we observe a characteristic ring-shaped surface pattern of the silicide. Surface rough-
ness and stress in fl-FeSi2 are less pronounced for films grown at lower temperatures and cooling rates. Sapphire substrates result in smoother surfaces than Si due to the match of the thermal expansion coefficient of sapphire to the silicides. C A Dlmitriadis and J H Werner, J Appl Phys, 68, 1990, 9346. 34 7339. Improvement of oxide quality by rapid thermal annealing Rapid thermal processing as a post-oxidation annealing (POA) process is of considerable influence on the quality of thin thermal oxides. The number of defect-related oxide failures is reduced, together with a slight reduction of the intrinsic oxide quality, but to a degree that is of no importance as regards reliability aspects. According to our investigations, it is important that POA is performed after poly-Si deposition and doping, whereas POA after poly-Si patterning is found to be an undesirable process. Infrared spectroscopy indicates stress relaxation caused by the POA treatment, but no change of the SiO2/Si-interface roughness could be observed by high-resolution electron microscopy. This relaxation process was accompanied by the creation of electron traps. Constant-current investigations indicated an enhanced electron trapping in the oxides after POA. This electron trapping increased with increasing POA temperature. The reduced defect-related oxide failures after POA are attributed to a retarded runaway of the injection current by negative space charges. H Wendt et al, JAppl Phys, 67, 1990, 7531 7535.
35. ION A N D PLASMA ETCHING 35 7340. Evaluation of dry etch processes with thermal waves Thermal wave analysis of plasma etching damage in the processing of trench capacitors is discussed. This rapid and reliable technique can be used to assess damage during processing and predict the electrical performance of fully-processed D R A M s M Engelhardt, Solid St Technol, 33, 1990, 151-156. 35 7341. Pattern marking on synthetic diamond film by Penning discharge sputtering Method and apparatus to perform micro-etching and micro-inlay of patterns and numericals on synthetic diamond films by Penning discharge sputtering has been developed and evaluated. In this apparatus, selection of etching and inlay modes are made by a change of anode position. In etching mode, etching beam originates in a Penning discharge space and is guided through a duct in order to reach the diamond film surface covered with a pattern mask and then forms an etching pattern on the surface. After the etching is made, a new position of the anode is selected for the inlay process and the metal atoms that sputtered from the cathode surface through the duct deposit on the previously etched portion on the diamond film. A 5.3 #m thick diamond film formed by microwave plasma CVD. A fiat dish-shaped etching of 2.5 mmtk and a same size inlay with gold were made with a mask having 2.5 mm~b hole and gold cathodes. In this case, etching rate of diamond film is 0.07~3.12/zm min t and deposition rate of gold 0.06 #m min ~. By the same technique, etching and gold inlay shaped after the numeral '5' with 120 #m in width and 180/~m in length was produced. T Sugita et al, Vacuum, 41, 1990, 1371-1373. 35 7342. Influence of the surface electron processes on the kinetics of silicon etching by fluorine atoms The model of silicon etching by fluorine atoms is presented. It is shown that the dielectric SiFx film formed on the surface plays an important part in the etching. As a consequence of high heat of adsorption for fluorine atoms on this film its penetration under the surface by thermal activation is difficult. A specific mechanism explaining the origin of the electric field in the film is proposed. The process of electric field formation is connected with valence electrons tunneling from silicon to adsorbed fluorine. The analysis of the electron processes in the S i ~ i F x F system results in non-linear equations which can be used to calculate the electric field strength and etch rate in a stationary regime. In the proposed model non-activated fluorine penetration into the SiFx film is provided and essential experimental results can be explained. Yu E Babanov et al, Vacuum, 41, 1990, 902-905. 587