Masao Tamura

Si Bridging Epitaxy from Si Windows onto SiO2 by Q-Switched Ruby Laser Pulse Annealing

Single crystal Si films have been epitaxially grown from chemical vapor-deposited poly-Si films from 2000 to 6000 A thick on (100) Si substrates by Q-switched ruby laser pulse irradiation of 25 ns duration at power densities above 2.0 J/cm2. When a poly-Si film deposited on the thermally grown SiO2 comes in contact with the substrate at the oxide window area, epitaxial growth first occurs at the window area. It then propagates in the lateral direction over the SiO2 up to a distance of 1.2 µm from the oxide edge. In Si films grown on SiO2, dislocations and stacking faults lying nearly in the directions remain.

MeV-energy B+, P+ and As+ ion implantation into Si

Abstract Annealing behavior of secondary defects in 2 MeV B + and P + , and 1 MeV As + ion implanted (100) Si has been investigated in terms of their structure, nature and depth distribution. This is done mainly through cross-sectional TEM observations at doses of 2 × 10 13 , 1 × 10 14 and 5 × 10 14 ions/cm 2 . The critical dose for generating secondary defects is between 2 × 10 13 and 1 × 10 14 ions/cm 2 , independent of ion species. A characteristic of B + and P + ion implanted layers is that buried secondary defects are formed beneath the substrate surface, with their maximum densities at depths of around 3.2 μm (B) and 2.1 μm (P) below the surface. These defect peak positions in the crystal are constant under all annealing conditions (e.g., a temperature range of 700 to 1250°C, annealing time of up to 6780 min at 1000°C). In contrast, the defects in the layers implanted with As + ions have an almost constant density in their depth distribution and change their depth position with annealing time and temperature. The peaks (B and P) and the central position (As) of these secondary defects are positioned deeper than both the projected range and the primary defect peak of each ion species.

MeV-ion-induced damage in Si and its annealing

Abstract The interactions between buried defects and impurities formed by MeV ion implantation in Si have been investigated from the following aspects: First, the interactions between the O atoms in CZ Si and the defects introduced during annealing after implantation with various ions, such as B, C, F, Si, P, Ge and As, are discussed by clarifying the amount, nature, morphology and depth distribution of the generated defects. Generally, oxygen atoms are gettered in two different regions of implanted layers. A shallow O peak appears in regions near the surface (between 0.5 and 1.5 μm deep), where no visible defect band exists. A deep peak of O is observed at locations where severe defects exist. These results are explained by considering ion mass, mismatch stress and point defects generated along individual ion tracks. Second, the effect of additional C and F implantation on density reduction and on changes in the configuration of defects formed by individual P and B implantation is reported. Under optimum implantation conditions, an effective suppression of elongated defect formation is observed after annealing at temperatures above 800 ° C. The results are discussed on the basis of interactions between implantation-induced interstitials (which are responsible for secondary defect formation) and implanted C and F atoms.

Lateral solid phase epitaxy of amorphous Si films on Si substrates with SiO2 patterns

Lateral solid phase epitaxy of amorphous Si films vacuum evaporated on Si substrates with SiO2 patterns has been investigated, in which the films first grow vertically in the region directly contacted to the Si substrates and then grow laterally onto SiO2 patterns. It was found from transmission electron microscopy and Nomarski optical microscopy that the lateral growth occurred in dense amorphous Si films formed by evaporation on heated substrates and subsequent amorphization by Si+ ion implantation, but it hardly occurred in porous films deposited at room temperature. The maximum length of the epitaxial film on SiO2 was about 6 μm after 10‐h annealing at 600 °C.

Generation of Dislocations Induced by Chemical Vapor Deposited Si3N4 Films on Silicon

The correlation between the dislocation generation and the stress in the (100) Si substrate surface completely covered with CVD Si3N4 films is investigated in relation to the film deposition and subsequent annealing conditions. The stress in the Si3N4 films deposited at 940°C at the NH3 flow rate of 1000 cc/min, when measured at room temperature, is tensile with 1.2–1.8×1010 dyn/cm2, and straight dislocations along two sets of [011] and [01] directions are formed in the Si surfaces after heat treatments at temperatures above 1050°C. The stress is small when the films are deposited at the small NH3 flow rate and high deposition temperatures. The interfacial stress generating the dislocations is found to be the inherent intrinsic stress produced during the deposition of Si3N4 film. Some characters of generated dislocations are described.

Low-energy mass-separated ion beam deposition of materials

Abstract A low energy mass-separated ion beam deposition system was developed. Ge+ ions of 100 μA were obtained at an acceleration energy of 100 eV with a beam spot size of 5 mm o at 5 × 10−8 Torr. Material buildup has been observed at the range of ion energy where the self-sputtering yield is below unity. The incident ion energy dependence of the reactions of the F+ and CFx+ ions with a silicon substrate has been measured, as well as the physical phenomena conventionally observed between impinging ions and a substrate material. Epitaxial growth of Ge films on Ge and Si single crystal substrates has been observed at 300°C with a Ge+ ion energy of 100 eV. Deposited Ge crystal properties were evaluated.

Damage formation and annealing of high energy ion implantation in Si

Abstract Damage formation and defect behavior during annealing in high-energy (1–3 MeV) and high-dose [(1−5) × 10 15 ions/cm 2 ] B + , P + and As + implanted (100) and (111) Si have been investigated, mainly using cross-sectional TEM observations. Specific characteristics of defect behavior during annealing are clarified in the annealing stages between 550 and 1300° C based on whether or not buried amorphous layers are formed in the implanted regions. The effect of bulk material nature (CZ or FZ) on defect growth is also described by clarifying the redistribution and gettering of mobile oxygens into damage-zones using secondary ion mass spectrometry (SIMS) measurements. These results provide detailed information on formation of buried impurity-layers of high concentration, e.g., aiming at subcollector formation of bipolar transistors.

Growth of hexagonal GaN on Si(111) coated with a thin flat SiC buffer layer

Hexagonal GaN films were grown on Si(111) covered with a thin flat SiC buffer layer under both N- and Ga-rich growth conditions. A flat 2.5-nm-thick SiC layer was an effective buffer layer for GaN growth. The growth mode and microstructure of GaN depended strongly on the Ga/N flux ratios. Under N-rich growth conditions, the growth mode was three dimensional; GaN showed statistical roughening of the surface and a characteristic columnar structure. Under Ga-rich conditions, the GaN growth mode was two dimensional; GaN films with a flat surface and an almost stacking-fault-free microstructure were obtained. The two-dimensional growth mode was facilitated by strong wetting between Ga and SiC(111) at the first Ga-layer deposition on SiC.

Depth distribution of secondary defects in 2‐MeV boron‐implanted silicon

Annealing behavior of secondary defects in 2‐MeV boron ion‐implanted (100) silicon has been investigated mainly through cross‐sectional TEM observations. The maximum defect density is located at a mean depth of 3.2 μm from the surface and the location is 0.3 μm deeper than that of the projected range of boron ions. This defect position in the crystal is constant under all annealing conditions (e.g., a temperature range of between 700 and 1000 °C, annealing time of up to 6780 min at 1000 °C), although the vertical distribution width of defects changes with both annealing temperature and time.

Nonequilibrium solid solutions obtained by heavy ion implantation and laser annealing

Nonequilibrium solid solubility of P, As, and B in single‐crystalline silicon annealed by Q‐switched ruby laser pulse irradiation was experimentally investigated for residual defects, lattice strain, and electrical activation of implanted impurities. The maximum solubility obtained without any macroscopically extended defect formation was 2–4 times higher than the thermal equilibrium solubility limit. Above this solubility, precipitates, dislocations, and surface cracks were observed. The highest full activation was realized by P implantation, with carrier concentration up to ∼5×1021/cm3 showing no such defects. Formation mechanisms of the defects are discussed and shown to be attributable to the rapid solidification process of the heavily doped layer and to large impurity‐induced misfit stress comparable to the fracture stress.Nonequilibrium solid solubility of P, As, and B in single‐crystalline silicon annealed by Q‐switched ruby laser pulse irradiation was experimentally investigated for residual defects, lattice strain, and electrical activation of implanted impurities. The maximum solubility obtained without any macroscopically extended defect formation was 2–4 times higher than the thermal equilibrium solubility limit. Above this solubility, precipitates, dislocations, and surface cracks were observed. The highest full activation was realized by P implantation, with carrier concentration up to ∼5×1021/cm3 showing no such defects. Formation mechanisms of the defects are discussed and shown to be attributable to the rapid solidification process of the heavily doped layer and to large impurity‐induced misfit stress comparable to the fracture stress.