K. Matsunaga

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.

Extraction characteristics of a high current metal ion source

A metal ion source has been developed for extracting high current ion beams of high melting point metals. In the discharge chamber, metal vapor was confined in high‐temperature shields, and the pure metal plasma was produced by the arc discharge. In order to prevent the vapor deposits, the extraction electrodes were also required to be high temperature. Thus, multislit electrodes were improved to maintain fine beam optics even if they were heated. To investigate the metal ion extraction characteristics, Al ion beams were extracted and compared with Ar ion beams. Furthermore, high current Al, Cr, Si, and Ti ion beams were extracted, and the extracted current ≳100 mA was obtained for each metal.

Development of high current metal ion beam source

Abstract A magnetic multipole ion source with some modifications to sustain high density metal vapour plasma has been developed and investigated. The following results are experimentally obtained for aluminium plasma: (1) the inside of the ion source is heated up to about 1500 K to sustain the metal vapour density necessary for a discharge; (2) the high purity aluminium plasma is produced; (3) the ion current density is over about 10 mA/cm2; and (4) the radial uniformity of ion current density is about ± 5% over a radius of 3 cm.

Ion species measurement of high current metal ion beams extracted from a multicusp ion source

Ion charge state and impurities extracted from a multicusp ion source have been studied with the use of a magnetic momentum mass analyzer. Impurities contained in high current metal ion beams are crucible materials (such as Al2O3, BN, Y2O3, C) and high melting point materials (such as Mo, Ta, W). To reduce these impurities, the dependence of the impurity on the arc discharge voltage has been investigated experimentally. Amounts of impurities and multicharged ions are decreased with arc discharge voltage. For example, at the arc discharge voltage of 60 V, aluminum ion beam contains 1% impurities and 4% multicharged ions, and at the arc discharge voltage of 20 V, impurities and multicharged ions are less than 1% in all. High‐purity single‐charged metal ion beams have been obtained.

High‐current metal ion beam extraction from a multicusp ion source

Improvements have been made in a multicusp ion source, which made it possible to produce metal–vapor plasma and extract a high‐current metal ion beam. In the discharge chamber, double radiation shields were set and the inner shields were heated to 1860 K. Therefore, it became possible to maintain enough metal–vapor density to produce plasma without the use of support gas. For the extraction of a high‐current metal ion beam, we used multislit electrodes in the accel–decel electrode structure. Experiments of the metal ion beam extraction were performed with several kinds of metals (Al, Cr, Si). For example, the extracted Al ion beam current reached 65 mA. As a result of mass analysis, it was found that more than 90% of an Al ion beam is Al+. Furthermore, stable operation could be achieved. For Al (58 mA) and Si (28 mA) ion beam extraction, the temporal drift of each ion beam current was within ±5% for 3 h.

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.

Extraction of high current Cr ion beam from a multicusp metal ion source

Improvements have been made in a metal ion source, which made it possible to produce high density metal vapor plasma for extracting high current metal ion beams. Experiments of chromium ion beam extraction were performed. The ion beam current reached 250 mA at the extraction voltage of 36 kV. Furthermore, stable operation was achieved at the extracted current of 117 mA. The temporal drift of ion beam current was within ±1% for 1 h.

Experiment of wide energy range control for metal ion beam

The continuous control of Cr ion beams from low energy to high energy in a single ion beam system was attempted. For this wide energy range control, a deceleration tube was connected to an acceleration tube. The Cr ion beams extracted from a metal ion source were mass separated and accelerated or decelerated in the acceleration or the deceleration tube. We divided the energy into two energy ranges, 100eV-30keV and 30keV-100keV. For each energy range, a different arrangement of power supplies was used, but the setup of the equipment was not changed. As a result, continuous control from 92eV to 101keV was achieved. The target current was 2.1mA (92eV) and 15mA (101keV).

Development of high current metal ion beams

R & D project of high current metal ion beam technology is being carried out for use in material surface modification and new material formation by means of ion implantation. Present results of the R & D are as follows. (1) A multicusp high temperature metal ion source with an operation temperature of 2000 degrees K was attained using heat reflectors in the ion source discharge chamber. (2) Extracted ion beam currents of Al, Cr, Si and Ti were more than 100mA. (3) Al ion beam could be accelerated up to 90keV yielding 50mA on the target.

High Current Metal Ion Beam Transport through a 90° Sector Magnet

For development of a mass separated high current (>100 mA) metal (Cr + ,Si + ,etc.) ion implantation system, beam transport characteristics through a mass separator were investigated. When a 121 mA Cr ion beam was extracted at the extraction voltage of 37 kV, Cr + beam of 79 mA passed through the 90° sector magnet with a bending radius of 50 cm, a pole piece gap of 12 cm and pole piece width of 20 cm. In these experiments the passed Cr + current increased in proportion to the extracted current, and the ratio of the passed current to the extracted current was about 64%. Thus the estimation of extraction conditions to transport a high current Cr + beam through the sector magnet became possible.