K. Matsuda

A new machine for film formation by ion and vapour deposition

Abstract A new machine for film coating with ion beam and vapour deposition (IVD) has been designed in order to realize practical applications of IVD. The machine consists of a rectangular bucket type multi-aperture ion source, evaporator with electron gun, rotary specimen holder and film thickness monitor. The ion energy is variable in the region 2–40 keV and the current for nitrogen ions is 100 mA. The area of the ion beam is 4 × 10 cm 2 . The beam uniformity is ± 10% and in the central region within a length of 6 cm it is ± 5%. The temperature of a specimen is controlled by water cooling. The technology was applied to a process of aluminum coating on low carbon steel. After coating with a 300 A layer of aluminum, an implantation process using 1 × 10 17 /cm 2 argon ions with 30 keV energy was performed. Then the aluminum deposition was continued by electron beam evaporation to a thickness of 1 μm. The resulting aluminum coating is maintained during a peel-off test up to 300 kg/cm 2 . Results related to the bending and corrosion properties of aluminum layers formed with ion beam assisted techniques are reported.

Nitride film formation by ion and vapour deposition

Abstract Boron nitride coating films were produced using ion beams of nitrogen molecules with energies 25–40 keV and simultaneous evaporation of boron (IVD method) and were analysed by infrared absorption spectra. X-ray diffraction and electron microscopy. Films with the composition ratio B N larger than about 0.9 have structures of cubic BN or close to this. Those with smaller B N than about 0.9 consist of hexagonal (layered) boron nitride or close to this. On some films, well oriented wurtzite type crystal was observed. A depth analysis for a titanium nitride film deposited on stainless steel prepared by IVD indicates the presence of a thick mixed layer of film and substrate.

Large diameter ion beam implantation system

Abstract A large diameter ion beam is expected to be applied in etching, sputtering and ion implantation processes. The recently developed ion implantation system consists of a large diameter ion source with no mass analyzing unit, and a wafer handling unit. The main characteristics of the system are the following: (1) the uniformity of the ion beam intensity is better than ± 15% within the 10 cm × 10 cm area at the target; (2) the ion beam energy is variable in the range of 5–40 keV, and the beam current is up to 40 mA for BF3 and PH3; (3) solid ion source materials can be used by attachment of the vaporizer to minimize the impurity; and (4) the high throughput operation of wafers up to 500 wafers per hour can be attained.

Interactions between arsenic and boron implanted in silicon during annealing

Arsenic ions (As+) and Boron ions (B+) were implanted into silicon (Si) at energies such that their respective projected ranges differ. In the implanted Si, the overlapping population of implanted As and B atoms occurred in the region in Si almost midway between their projected ranges near the surfaces after annealing. The only region in Si with As atoms concentration more than three times as large as the B atom concentration became n type.

Development of a high current and high energy metal ion beam system

Abstract A high current metal ion accelerating system, which consists of a metal vapor plasma ion source with a multicusp magnetic field and a single gap acceleration column, has been developed. The following results were obtained experimentally: (1) a 110 mA aluminum ion beam and a 95 mA chromium ion beam were extracted from the ion source, (2) the impurities contained in the beams were less than 1%, and (3) the aluminum ion beam was accelerated up to 90 keV at 50 mA on the target.

Dual arsenic and boron ion implantation in silicon

Arsenic (As) and boron (B) ions were implanted into silicon (Si) at energies such that their projected ranges coincided. The implanted Si was annealed in argon gas at a temperature of 950 °C for 30 or 300 min. The activation efficiency of the implanted As atoms decreased with an increase in the implant dose of the B ions, and the diffusivity of the As atoms decreased. On the other hand, the diffusivity of the B atoms decreased with an increase in annealing time.

Hyperthermal (30–500 eV) C+ ion-beam doping into GaAs during molecular beam epitaxy

Abstract Ion-beam doping of GaAs with hyperthermal (30–500 eV) carbon ion (C + ) has been investigated using a combined ion beam and molecular beam epitaxy (CIBMBE) system. The CIBME system is a combination technique between a low-energy ion accelerator and a solid-source MBE, which are connected under ultra-high vacuum (UHV) condition. C + -doping was carried out during GaAs MBE growth at substrate temperature of 550°C with the same C + beam current density. Grown layers were characterized by low-temperature (2 K) photoluminescence and room temperature Hall effect measurements, and it was revealed that the incorporation behavior of C significantly depends on the acceleration energy of C + ( E C ). The highest net hole concentration (∥ N A − N D ∥) was obtained at E C + = 170 eV. In the energy range of E C + N A − N D ∥ slightly increased as E C + increased, and for E C + > 170 eV ∥ N A − N D ∥ dramatically decreased with increasing E C + , which can be explained in terms of enhanced sputtering effect. On the other hand, ion-beam induced radiation damages were observed for E C + > 170 eV.

Reliability of shallow n+-type layers formed in dual As and B implanted silicon by rapid thermal annealing

Abstract Czochralski-grown 20 Ω cm, B-doped, (100) Si wafers were implanted with combinations of As + and B + ions at energies such that their respective projected ranges coincide at a position of about 30 nm. The implanted dose of As + ions was 1 × 10 16 cm −2 and those of B + ions were in the range of 2.4 × 10 14 – 5 × 10 15 cm −2 . The samples were annealed at 950°C for 10 s using halogen lamps. The junction was formed at a depth of about 120 nm for Si implanted with doses below 2.4 × 10 15 cm −2 of B + ions. The junction, however, could not be formed for Si implanted with a dose of 5 × 10 15 cm −2 of B + ions. The sample changed to n-type by subsequent furnace annealing at 950°C for 30–300 min. The junction depth became shallower with dose of B + ions because an inactive and immobile complex such as AsB is formed in the surface region.

High current implantation equipment

Abstract High current ion implantation technology has been getting a great deal of attention in the fields of surface modification and new material formation. For such diverse applications a high current implanter with a sputter-ion source has been developed and stable production of metal ion beams has been demonstrated. High melting point metal ions such as Cr+, Fe+ and Pd+ were successfully extracted at a beam current of 420, 340, and 260 μA, respectively. A monitor system of metal vapor production for a stable beam has been tested using an optical spectrometer and its usefulness was confirmed.

Hydrogenation of High-Concentration Arsenic-Doped Silicon Using Radio Frequency Hydrogen Plasma

n-type layers in silicon with high carrier concentrations have been formed by high-dose (1×1015–1×1016 cm-2) As-ion implantation and subsequently 950°C-annealing. The n-type layers containing many As clusters were exposed to radio-frequency hydrogen plasma for 30 min. While the hydrogenated samples had the same As-atom concentration profile as the as-annealed samples, the carrier concentration profiles approached the As atom concentration profile with increasing substrate temperature. The activation energy obtained from the Arrhenius plot of the carrier concentration agreed well with that of the diffusivity of H atoms in silicon. Thus, the increase in the carrier concentration is a result of H atoms reacting with As clusters.