Naotsugu Yoshihiro

Correlation between lattice damage and electrical activation of phosphorus-implanted silicon

Quantitative comparision between the profiles of damage density before annealing and carrier concentration after annealing were examined for a wide range of phosphorus‐implantation dose (1013–1016 cm−2). Electrical‐activation mechanisms during low‐temperature (around 500 °C) annealing before epitaxial regrowth occurs were found to be different in the different damaged regions (very low, ∼20%, 20–75%, 75%∼damage density).

Nature and Annealing Behavior of Disorders in Ion Implanted Silicon

A comprehensive review is given on the studies of the nature and low temperature(≈500°C) annealing behavior of disorders generated in silicon single crystal substrates during impurity ion implantation. Interaction of disorders and impurity atoms during annealing treatment is analysed over each layer along ion trajectories. This is because the concentrations of both disorders and implanted impurity atoms have unique distribution profiles in the substrate. On the assumption that a carrier compensation center is left where the recovery of each implantation generated amorphous cluster occurs, it is found to be essential, for the electrical activation of implanted impurity atoms, that spatial overlapping of the amorphous clusters occurs. Excess vacancies generated during annealing from amorphous layers are thought to thought to contribute to the anomalous behavior of solid solubility of impurity atoms involved in regrown layers. A better understanding of the phenomena that govern implantation and subsequent annealing offered would open a way for new applications of implantation technology.

Damage-dependent electrical activation of ion-implanted silicon. I. Experiments on phosphorus implants

The electrical activation mechanism of phosphorus ions implanted into a silicon substrate is studied during low‐temperature (?550 °C) annealing. Apparently anomalous behavior where the electrically active fraction versus dose curve shows a peak in a limited dose range is analyzed by measuring the distribution profiles of damage and carrier concentration. Carrier generation was found to be strongly influenced by the extent of damage in the layer. Phosphorus atoms in layers with less than 20% damage were not electrically activated. However, in layers with more than 20% damage, electrical activation abruptly increased with the change of damage. This correlation existed at each depth in the substrate for all samples with various doses. The anomalous dose dependence of the electrically active fraction was recognized to be an integral result of the phenomenon. Analysis of the damage formation showed that overlapping of amorphous clusters produced in each ion trajectory is essential for the electrical activation...

Outside dislocations generated from phosphorus implanted silicon layers

The growth, movement and nature of outside dislocation, which propagate from heavily phosphorus (>1015 ions/cm2) implanted (111), (100), and (110) silicon layers into unimplanted outside regions by a compressive strain induced during 1100° C wet O2 annealing, are investigated using transmission electron microscopy and x-ray diffraction topography. Outside dislocations are formed, mainly on (111) planes., by the glide motion of dislocation networks formed in implanted layers during early annealing. This results in dislocations extending into the unimplanted areas to different degrees, in the order of, from the largest to smallest, (111), (110), and (100) wafers. In (110) wafers, the [001] oriented dislocations in the implanted regions rise to the surface at the implant and unimplant boundary. On the other hand, the [110] dislocations penetrate into the unimplanted region. Two sets of orthogonal 〈110〉 oriented dislocations generated in (100) implanted wafers behave in the same manner as the [001] dislocations in (110) wafers. Some sources of the compressive strain related to the generation of these dislocations are discussed.

Low Temperature Annealing Characteristics of Phosphorus-Implanted Silicon

The process of electrical activation of phosphorus implanted into silicon at a dose of 1.0×1014–2.0×1015 cm-2 and an energy of 35–170 keV is investigated in an annealing temperature range around 500°C. In the low dose regions (≤3–4×1014 cm-2), the doping efficiency increases with increasing ion dose and the isolated amorphous region generated during implantation is easily decomposed by low temperature annealing. On the other hand, in the high dose regions, the doping efficiency decreases with increasing ion dose and an appreciable part of amorphous zones remains unannealed during the low temperature treatment.

Two signals in electrically detected magnetic resonance of platinum-doped silicon p–n junctions

We have found two electrically detected magnetic resonance (EDMR) signals at room temperature in forward-biased platinum (Pt)-doped (111) silicon p–n junction diodes with a linearly graded junction. The g values of the two EDMR signals are 1.991 (signal 1) and 1.978 (signal 2), respectively, when the surface of the diode is parallel to the magnetic field. The two signals increase after applying a large reverse-bias voltage to the junction. They decay with time; the decay rate after more than 1 h is smaller for signal 1 than for signal 2. The recombination current also changes in a similar manner as the EDMR signals. The intensity of the two EDMR signals each shows a known bell-shape dependence on a forward bias voltage; signal 1 is observed at slightly lower voltages than signal 2. The deep level transient spectroscopy (DLTS) spectrum from the diodes shows two peaks at 0.23 and 0.32 eV. For diodes with different Pt-diffusion temperatures, 865 and 885 °C, the ratio of the intensity of the EDMR signals corr...

Mobility and carrier‐concentration profiles of P+ ion‐implanted, isothermally annealed silicon crystals

Experimental data of carrier mobility and carrier concentration profiles in depth from the surface of silicon wafers implanted with 50 keV P+ ions of various doses, isothermally annealed at 480 °C, are reported. Generation and annihilation of mobility controlling defects and carrier trapping centers are discussed with these data. A comment on the carrier recovery of heavily dosed specimens is given.

High Dose Phosphorus-Germanium Double Implantation in Silicon

The formation of the dislocation networks in the well annealed high dose phosphorus implanted silicon can be suppressed if phosphorus-germanium double implantation is applied. The dose of germanium less than a half of that of phosphorus is required. A wet oxidation at about 800°C before high temperature anneal enhances the effect.