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6173. Surface preciption of boron nitrate on the surface of type 304]' stainless steels doped with nitrogen, boron, and cerium
Classified abstracts 6166-6173
spin resonance measurements were used to characterize the bombarded samples. Extensive microstructural modifications occur as a result of hydrogen ion bombardment; the orientation, size, density, and distribution of the features which form vary as a function of crystal orientation, dose rate, bulk temperature, and total dose. Electron spin resonance studies indicate no detectable change in the number of occupied unpaired electron spin states occur in conjunction with this damage. J K G Pa&z et al, J Vat Sci Technol, A3, 1985 l-5. 31 6166. Effect of dopant implantation on the properties of TaSi,/poly-Si composites
Refractory metal silicide/poly-Si composites are replacing poly-Si in VLSI circuits in order to reduce runner resistance without sacrificing poly-Si MOS compatibility. In a typical integrated circuit (IC) fabrication sequence, the gate serves as a mask for the formation of self-aligned sources and drains. It is, therefore, exposed to various heavy implants of B, P, or As. These implants subsequently redistribute during further processing. This paper investigates the effect of dopant implantation and redistribution on the mechanical, structural and klectrical properties of silicided polv-Si. Implantation increases the sheet resistance of 2500 A of sintered ‘?a&, by a-factor of 2-3. This coincides with a decrease in the silicide stress, proportional to the implant range in TaSi,, and to a lesser degree, the implant dose. These stress changes, however, recover by 5OO”C, while the TaSi, resistivity returns to its nominal value (2-2.5 R Cl-‘) following a 900°C heat cycle. Doses as high as lE16As cm-’ do not render TaSi, amorphous. If the underlying LPCVD poly-Si is initially undoped, the nature of the impurity appears to influence subsequent poly-Si recrystallization. With P/As, the poly-Si grains grow during a high temperature anneal. However, with B, the grains remain needle-like. This recrystallized poly-Si grain structure nevertheless significantly different from the large, equiaxed grains developed when the poly-Si is doped in a PBr, gas flow, prior to TaSi, deposition. N-type impurities readily redistribute from the silicide into poly-Si by 950°C. Thus, a single n + source/drain implant can effectively dope the gate, buried gate-substrate contacts and junctions in NMOS circuits. The corresponding gate metal work function I$,,,is comparable to the reported values for n + poly-Si. B, on the other hand, is retained in the silicide. This results in a somewhat lower 4, value than expected for p + poly-Si. S Vaidya et al, J Vat Sci Technol, B3, 1985, 846-852. 31 6167. As+ implantation and transient annealing of MoSi, thin films
The effect of 100 keV arsenic implantation on the structural, compositional, and electrical properties of sputtered and annealed MoSi, films is investigated. Before implantation, the silicide films had a tetragonal structure with a sheet resistance of approximately 2.2 a 0 -I for a nominal film thickness of 0.3 pm. As+ implantation increased the sheet resistance by approximately 140% of its initial value at a dose of 5 x 1016 cm-‘. Hexagonal MoSi, phase was formed at implantation doses >5 x 1Ol5 cm-‘. Rapid lamp annealing at 900°C for 10 s removed the hexagonal phase but was not enough to restore the low sheet resistance of the unimplanted wafers. Transient annealing at 1100°C for 10 s was sufficient to regain the low sheet resistance for all films (u 2.2 Q 0 -I). A thermal spike model was successfully applied to explain the absence of an amorphous phase and the formation of a low temperature hexagonal structure in high dose implantation films. In addition, the recorded RBS spectra showed pronounced low-energy tails which were independent of the implantation conditions. The origin of these tails was attributed to the anomalous surface morphology of the silicide films deposited on oxide layers. S A Agamy et al, J Vat Sci Technol, A3, 1985, 718-122. 32. ION IMPLANTATION
OF METALS
32 6168. The trapping of deuterium in argon-implanted nickel Argon ions with energy 250 keV were implanted at fluences of 2x 1Cl’6cm-2 at temperatures of 500, 250, and 21”C, in a specimen of relatively pure polycrystalline nickel. Deuterium was introduced into the surface and implanted regions by making the specimen the negative electrode of an electrolytic cell containing 1-N pure deuterated sulfuric acid. Deuterium trapped in the vacancy complexes of the implanted regions was analyzed as a function of temperature using the 2H(3He, ‘H)4He nuclear reaction during an isochronal annealing process. The results indicate that the types of traps and trap densities found in the regions implanted at 21 and 250°C were essentially identical while the trap density found in the region implanted at 500°C was approximately 40% of
that found in the other regions. Math model comparison with the experimental results suggests the existence of at least two types of traps in each region. Trap binding enthalpies used in the math model to fit the experimental data were slightly higher for the region implanted with argon at 500°C than for the regions implanted at the lower temperatures. TEM studies revealed the presence of small voids in the region implanted at 500°C as well as dislocation loops similar to those found in the regions implanted at the lower temperatures. R C Frank et al, J appl Phys, 57, 1985, 845-848. 32 6169. Modification of silicon structure during highly intensive Ar+ ion implantation
By means of transmission electron microscopy it is established that the rearrangement of silicon structure under highly intensive Ar+ ion implantation proceeds through the four following well-defined stages: (i) disorder accumulation; (ii) amorphization; (iii) solid phase epitaxy; (iv) structure modifications in the crystallized layers. The features of structure modifications during these stages of implantation are different. This is suggested to be a result of variation of the dynamic balance between the accumulation of radiation damage and thermally activated annealing. F F Komarov et al, Rad EJfcts, 90, 1985, 307-315. 32 6170. Interaction of slow charged particles (H+,He+ ‘) with solids We have generalized the formula firstly given by Neufeld and Ritchie (see Ref I) describing the electric field of a charged particle moving through solid when the particle velocity (u,) may be of the same order (or less) as compared to the Fermi velocity uF. Corrections to the pair interaction potentials of protons and alpha-particles with the target atoms due to the dynamical screening are estimated. G V Dedkov and A Sh Nasipov, Rad Eficts Letts, 87, 1985, 37-41. 32 6171. Comparative study of intermetallic phases formed by direct ion implantation and radiation enhanced diffusion of tin in two kinds of steel
The surface layers of high-carbon and stainless steel samples, treated by both direct ion implantation of Sn+ ions and radiation enhanced diffusion of tin, are analyzed by means of Rutherford backscattering and l19Sn and “Fe conversion electron MGssbauer spectroscopy. The intermetallic phases formed in the treated surfaces are determined and their thermal evolution is established. The compositions and phase transformations observed in the surface of the samples treated by both direct ion implantation and radiation-enhanced diffusion are very similar, and this similarity indicates that these two treatment processes are essentially equialent for practical applications. P H Dionisio et al, J appl Phys, 58, 1985, 773-778. 32 6172. Immobilization mechanisms for ion-implanted deuterium in aluminum
Aluminum was ion implanted with deuterium (D) and then subjected to linear temperature ramping, and the resulting D redistributions were monitored using the ion-induced nuclear reaction D(3He,p)4He. Data from such experiments were analyzed in terms of various immobilization processes, utilizing numerical solutions of the appropriate diffusion formalism. The identification of mechanisms was augmented by transmission electron microscopy. Irradiation defects believed to be of vacancy type were shown to trap the D with a binding enthalpy of 0.52&0.10 eV relative to solution sites, in excellent agreement with calculations based on effective medium theory. Stronger binding at the surface oxide was quantitatively described by assuming the formation of D, molecules at the metal-oxide interface. At higher implanted concentrations the immobilization of D by precipitation of D, bubbles was observed, and the subsequent release from these bubbles at more elevated temperatures was described by diffusion theory. Small, high-pressure He bubbles formed by ion implantation of He did not trap the D more strongly than the irradiation defects, in contrast to observations in a number of other metals, but consistent with predictions of effective medium theory for Al. S M Myers et al, J appl Phys, 58, 1985, 1841-1850. 32 6173. Surface precipitation of boron nitride on the surface of type 304 stainless steels doped with nitrogen, boron, and cerium
The surface compositions of two types of stainless steels in vacuum were observed with A& and XPS at 10&l 100 K; a 304 stainless steel doped with nitrogen and boron (304-NB) and a 304 stainless steel doped with nitrogen, boron, and cerium (jO4-NBCe). The changes of surface compositions of these steels were compared with that of commercial 304 stainless steel. A thin layer of boron nitride came out from grain boundaries and spread over the surface of the 304-NB, but did not 733
spin resonance measurements were used to characterize the bombarded samples. Extensive microstructural modifications occur as a result of hydrogen ion bombardment; the orientation, size, density, and distribution of the features which form vary as a function of crystal orientation, dose rate, bulk temperature, and total dose. Electron spin resonance studies indicate no detectable change in the number of occupied unpaired electron spin states occur in conjunction with this damage. J K G Pa&z et al, J Vat Sci Technol, A3, 1985 l-5. 31 6166. Effect of dopant implantation on the properties of TaSi,/poly-Si composites
Refractory metal silicide/poly-Si composites are replacing poly-Si in VLSI circuits in order to reduce runner resistance without sacrificing poly-Si MOS compatibility. In a typical integrated circuit (IC) fabrication sequence, the gate serves as a mask for the formation of self-aligned sources and drains. It is, therefore, exposed to various heavy implants of B, P, or As. These implants subsequently redistribute during further processing. This paper investigates the effect of dopant implantation and redistribution on the mechanical, structural and klectrical properties of silicided polv-Si. Implantation increases the sheet resistance of 2500 A of sintered ‘?a&, by a-factor of 2-3. This coincides with a decrease in the silicide stress, proportional to the implant range in TaSi,, and to a lesser degree, the implant dose. These stress changes, however, recover by 5OO”C, while the TaSi, resistivity returns to its nominal value (2-2.5 R Cl-‘) following a 900°C heat cycle. Doses as high as lE16As cm-’ do not render TaSi, amorphous. If the underlying LPCVD poly-Si is initially undoped, the nature of the impurity appears to influence subsequent poly-Si recrystallization. With P/As, the poly-Si grains grow during a high temperature anneal. However, with B, the grains remain needle-like. This recrystallized poly-Si grain structure nevertheless significantly different from the large, equiaxed grains developed when the poly-Si is doped in a PBr, gas flow, prior to TaSi, deposition. N-type impurities readily redistribute from the silicide into poly-Si by 950°C. Thus, a single n + source/drain implant can effectively dope the gate, buried gate-substrate contacts and junctions in NMOS circuits. The corresponding gate metal work function I$,,,is comparable to the reported values for n + poly-Si. B, on the other hand, is retained in the silicide. This results in a somewhat lower 4, value than expected for p + poly-Si. S Vaidya et al, J Vat Sci Technol, B3, 1985, 846-852. 31 6167. As+ implantation and transient annealing of MoSi, thin films
The effect of 100 keV arsenic implantation on the structural, compositional, and electrical properties of sputtered and annealed MoSi, films is investigated. Before implantation, the silicide films had a tetragonal structure with a sheet resistance of approximately 2.2 a 0 -I for a nominal film thickness of 0.3 pm. As+ implantation increased the sheet resistance by approximately 140% of its initial value at a dose of 5 x 1016 cm-‘. Hexagonal MoSi, phase was formed at implantation doses >5 x 1Ol5 cm-‘. Rapid lamp annealing at 900°C for 10 s removed the hexagonal phase but was not enough to restore the low sheet resistance of the unimplanted wafers. Transient annealing at 1100°C for 10 s was sufficient to regain the low sheet resistance for all films (u 2.2 Q 0 -I). A thermal spike model was successfully applied to explain the absence of an amorphous phase and the formation of a low temperature hexagonal structure in high dose implantation films. In addition, the recorded RBS spectra showed pronounced low-energy tails which were independent of the implantation conditions. The origin of these tails was attributed to the anomalous surface morphology of the silicide films deposited on oxide layers. S A Agamy et al, J Vat Sci Technol, A3, 1985, 718-122. 32. ION IMPLANTATION
OF METALS
32 6168. The trapping of deuterium in argon-implanted nickel Argon ions with energy 250 keV were implanted at fluences of 2x 1Cl’6cm-2 at temperatures of 500, 250, and 21”C, in a specimen of relatively pure polycrystalline nickel. Deuterium was introduced into the surface and implanted regions by making the specimen the negative electrode of an electrolytic cell containing 1-N pure deuterated sulfuric acid. Deuterium trapped in the vacancy complexes of the implanted regions was analyzed as a function of temperature using the 2H(3He, ‘H)4He nuclear reaction during an isochronal annealing process. The results indicate that the types of traps and trap densities found in the regions implanted at 21 and 250°C were essentially identical while the trap density found in the region implanted at 500°C was approximately 40% of
that found in the other regions. Math model comparison with the experimental results suggests the existence of at least two types of traps in each region. Trap binding enthalpies used in the math model to fit the experimental data were slightly higher for the region implanted with argon at 500°C than for the regions implanted at the lower temperatures. TEM studies revealed the presence of small voids in the region implanted at 500°C as well as dislocation loops similar to those found in the regions implanted at the lower temperatures. R C Frank et al, J appl Phys, 57, 1985, 845-848. 32 6169. Modification of silicon structure during highly intensive Ar+ ion implantation
By means of transmission electron microscopy it is established that the rearrangement of silicon structure under highly intensive Ar+ ion implantation proceeds through the four following well-defined stages: (i) disorder accumulation; (ii) amorphization; (iii) solid phase epitaxy; (iv) structure modifications in the crystallized layers. The features of structure modifications during these stages of implantation are different. This is suggested to be a result of variation of the dynamic balance between the accumulation of radiation damage and thermally activated annealing. F F Komarov et al, Rad EJfcts, 90, 1985, 307-315. 32 6170. Interaction of slow charged particles (H+,He+ ‘) with solids We have generalized the formula firstly given by Neufeld and Ritchie (see Ref I) describing the electric field of a charged particle moving through solid when the particle velocity (u,) may be of the same order (or less) as compared to the Fermi velocity uF. Corrections to the pair interaction potentials of protons and alpha-particles with the target atoms due to the dynamical screening are estimated. G V Dedkov and A Sh Nasipov, Rad Eficts Letts, 87, 1985, 37-41. 32 6171. Comparative study of intermetallic phases formed by direct ion implantation and radiation enhanced diffusion of tin in two kinds of steel
The surface layers of high-carbon and stainless steel samples, treated by both direct ion implantation of Sn+ ions and radiation enhanced diffusion of tin, are analyzed by means of Rutherford backscattering and l19Sn and “Fe conversion electron MGssbauer spectroscopy. The intermetallic phases formed in the treated surfaces are determined and their thermal evolution is established. The compositions and phase transformations observed in the surface of the samples treated by both direct ion implantation and radiation-enhanced diffusion are very similar, and this similarity indicates that these two treatment processes are essentially equialent for practical applications. P H Dionisio et al, J appl Phys, 58, 1985, 773-778. 32 6172. Immobilization mechanisms for ion-implanted deuterium in aluminum
Aluminum was ion implanted with deuterium (D) and then subjected to linear temperature ramping, and the resulting D redistributions were monitored using the ion-induced nuclear reaction D(3He,p)4He. Data from such experiments were analyzed in terms of various immobilization processes, utilizing numerical solutions of the appropriate diffusion formalism. The identification of mechanisms was augmented by transmission electron microscopy. Irradiation defects believed to be of vacancy type were shown to trap the D with a binding enthalpy of 0.52&0.10 eV relative to solution sites, in excellent agreement with calculations based on effective medium theory. Stronger binding at the surface oxide was quantitatively described by assuming the formation of D, molecules at the metal-oxide interface. At higher implanted concentrations the immobilization of D by precipitation of D, bubbles was observed, and the subsequent release from these bubbles at more elevated temperatures was described by diffusion theory. Small, high-pressure He bubbles formed by ion implantation of He did not trap the D more strongly than the irradiation defects, in contrast to observations in a number of other metals, but consistent with predictions of effective medium theory for Al. S M Myers et al, J appl Phys, 58, 1985, 1841-1850. 32 6173. Surface precipitation of boron nitride on the surface of type 304 stainless steels doped with nitrogen, boron, and cerium
The surface compositions of two types of stainless steels in vacuum were observed with A& and XPS at 10&l 100 K; a 304 stainless steel doped with nitrogen and boron (304-NB) and a 304 stainless steel doped with nitrogen, boron, and cerium (jO4-NBCe). The changes of surface compositions of these steels were compared with that of commercial 304 stainless steel. A thin layer of boron nitride came out from grain boundaries and spread over the surface of the 304-NB, but did not 733