Takayoshi Seki

Ion beam acceleration using variable frequency RFQ

Abstract To develop a high-current MeV ion implanter, a beam acceleration feasibility study using a variable frequency RFQ system was carried out. The RFQ system consists of an LC tank circuit and conventional RFQ electrodes 60 cm in length. The resonance frequency was varied by changing the electrical capacity in the circuit. Experimental results show that injected N+ beams of 1.3 keV were accelerat frequency in the range of 12–15 MHz. The Q-value obtained was over 1500. Results show that a variable frequency RFQ system is suitable for application in MeV ion implantation.

New microwave ion source for high energy ion implanter

Abstract A new high current multiply-charged ion source, which is used for a high energy ion implanter, was designed to produce a mA-class multiply-charged ion beam. The discharge chamber is approximately four times larger than that of a conventional coaxial-type source and has a multipole magnetic field. An ion beam of a several mA is extracted from the new source and mass-analyzed. The extracted ion beam has an Ar 2+ beam of approximately 1 mA. The Ar 2+ /Ar + ratio obtained from this new source is 80%, which is a large improvement over the 10% of the conventional source. This ratio increases with absorbed microwave power.

Emittances of a microwave ion source for implantation

Abstract A new apparatus was developed to study the performance of a microwave ion source as a means to improve a high-current ion implanter. The apparatus consists of an emittance measuring device, a mass separator and a beam profile monitor. It can handle beams of high current (several 10 mA) and high power (up to 2 kW). By studying emittances of the ion source, conditions for improved matching of the ion source and the mass separator in the ion implanter were obtained.

High-current microwave ion source for wide-energy-range O+ ion implantation

A high-current microwave ion source which is used for O+ ion implantation in separation by implanted oxygen (SIMOX) wafer fabrication is presented. The source consists of a new transform waveguide which efficiently propagates a 2.45 GHz microwave power into the ion source, a cylindrical plasma chamber of 90 mm in diameter, and a multiaperture extraction electrode system. The extracted beams are mass separated and then postaccelerated up to 200 keV. Ion source operates stably for a long time and the microwave absorption efficiency is as high as 80%. A total extraction current of 240 mA is obtained at the extraction voltage of 50–60 kV and the mass-separated O+ current reaches about 100 mA at the same extraction voltage. The data show that the ion source has a good potential to provide 100 mA-class O+ ion beams stably in the wide energy range demanded for SIMOX ion implantation.

New microwave ion source for multiply charged ion beam production

Abstract To obtain high-current beams of rather lower-charge-state multiply charged ions, a new microwave ion source is designed. Ion beams of a few mA are extracted from the plasma and mass-analysed. The extracted beams have large quantities of multiply charged Ar ions at relatively lower gas pressures of 10 −4 −10 −3 Pa. In addition, these quantities tend to effectively increase with microwave power. The microwave power necessary for mA-class implantation current of low-charge-state ions is estimated to be from 3–5 kW.

Magnetic Field Design of a Superconducting Wiggler in the SAGA-LS Storage Ring

A magnetic field design for a superconducting (SC) wiggler system, which has been installed in the Saga light source storage ring, was described. The wiggler is a three-pole type, consisting of a 4.0-T SC center magnet and two normal-conducting side magnets; thus, each pole forms a magnet. Since the wiggler consists of isolated magnets, reduction of the first field integral of the center SC magnet was important from the viewpoint of suppression of the orbit displacement. For this purpose, the center SC magnet was designed to have a separated iron core with field clamps and no transverse return yoke. This concept made magnetic field negative regions near the center peak magnetic field on the electron beam orbit to reduce the first field integral and beam meandering. Heat generations due to eddy currents and the magnetic field due to supporting structures were calculated to have ignorable effects. The appropriateness of the design has been confirmed through daily stable operation at the light source.

Beam qualities of a microwave ion source

Beam characteristics of a microwave ion source for implantation were studied with an apparatus that can evaluate the degree of matching between the ion source and mass‐separator optics. The principal cause that limits the beam transmission of mass separator optics was clarified and an approach was taken to eliminate it. The emittance for the length depends on the plasma density distribution along the slit, which was found to be closely related to the vapor inlet system of the plasma chamber. In order to make the plasma density distribution uniform, several vapor inlets were arranged in a line along the slit. This resulted in a lower emittance.

Improvement of a microwave ion source for surface modification

Abstract A microwave ion source for metallic ions was modified to eliminate the magnetic field from the ion extraction space, thus providing stable beams. The beam characteristics of the source were measured with both N 2 and TiCl 4 . Ratios of N + to N 2 + and Ti + to Cl + in the mass spectra varied depending on discharge conditons such as microwave power and gas pressure. Emittance variations were also measured with an apparatus consisting of an emittance measuring device, a mass separator and a beam profile monitor. Conditions for improved matching of the ion source and the mass separator are discussed.

Advanced microwave ion source for 100 mA-class SIMOX ion implantation

To produce SIMOX wafers with high throughput, a compact and long lifetime microwave ion source for 100 mA-class oxygen ion implantation was newly developed. The ion source operated stably for more than 3 months with no maintenance under the beam extraction condition of 150 mA at 50 kV. When the source was installed in a SIMOX ion implanter, operation test showed that the ion source is suited to 100 mA-class ion implantation, giving volume production of high quality SIMOX wafers.

Ge+ ion extraction from a microwave ion source

Preamorphization of a silicon substrate by Ge+ ion implantation is required for shallow doping of boron, which, in turn, is the key process to realize highly integrated semiconductor devices. However, Ge+ ions have not been stably extracted by conventional methods. Several chemical compounds of germanium, GeO, GeS, GeCl4, and GeF4, were supplied to a microwave ion source and the characteristics of their ion extractions were compared. The conditions for obtaining mass‐separated Ge+ ions of more than 1 mA were found.