Katsumi Tokiguchi

Microwave ion source for high-current implanter.

A long-life, high-current, microwave ion source for an electromagnetic mass separator is described. Ionization takes place due to the 2.45-GHz microwave discharge at a magnetic field intensity which is higher than the electron cyclotron resonance magnetic field. The discharge chamber is a ridged circular waveguide. The discharge region is restricted to a rectangular volume between the ridged electrodes by filling the remaining portions with dielectric. This source operates under low pressure (10(-2)-10(-3) Torr) and with high power efficiency. The incident microwave power is only several hundred watts at maximum output. When PH(3) gas is introduced, the total extracted current is about 40 mA with a 2x40-mm extraction slit. A P(+) ion implantation current of more than 10 mA is obtained by combining the source with a 40-cm radius, 60 degrees deflection magnetic mass separator.

High‐current ion implanter using a microwave ion source

A new ion implanter has been designed for high‐dose predeposition in a semiconductor production line. It incorporates a microwave ion source, a 90° magnetic mass separator, and a rotating disk target chamber. Mass peak variations of PH3 gas are shown as a function of the incident microwave power. The ion energy level can be varied from 10 to 50 keV. It makes 10 mA P+ implantation (maximum 15 mA) possible. After beam adjustment, implantation is automatically carried out with a microcomputer. The operation rate of the implanter is remarkably improved due to the long lifetime of the modified microwave ion source and the low gas consumption. The dose nonuniformity of a 3‐in. wafer implanted with this implanter has a standard deviation (σ) of 0.5%. This small nonuniformity results in a small σ in the transistor current gain (less than 3.5%).

Microwave ion source for high current metal beams

Abstract A high current, metal ion source has been developed for application to materials modification in metals and insulators. In a microwave discharge type ion source, even highly reactive materials such as metal halides, as well as oxygen, can be used for source feed materials. The microwave ion source originally developed for conventional semiconductor fabrication has been modified to provide several mA of mass-separated metal ions. So far, ions of Al + , Ga + , Ti + , Hf + and Sc + have been obtained.

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.

Beam extraction experiments from microwave ion sources

With the aim of designing a new ion source for ampere‐class beams, the beam extraction characteristics of standard coaxial‐type microwave ion sources were investigated in detail at energies lower than 10 keV. It was found that this source has the capability of providing Ar+ beams of 200 mA at the acceleration voltage of 7.0 kV and the microwave power of 850 W. The obtainable beam current increases with a decrease of gap width between positive and negative electrodes. Moreover, it is shown that the microwave ion source is suitable for obtaining high‐current beams of single‐charged ions. Both the plasma source and extraction electrode diameters for 1‐A beam are estimated to be about 13 cm. The required microwave power is about 6 kW.

High energy aluminum ion implantation using a variable energy radio frequency quadrupole implanter

A high energy aluminum ion implantation using a variable energy radio frequency quadrupole (RFQ) implanter has been studied for the fabrication of high power semiconductor devices. The implanter consists of a microwave ion source with a crucible for AlCl3 sublimation, a sector type mass separator, a magnetic quadrupole triplet, a variable energy four-rod RFQ linac as an additional accelerator, an energy analyzer, and an implantation chamber. Al2+ ions, with energies of 1.0 MeV and 0.9 MeV, are implanted into a 6-inch diameter wafer, and the depth profile and dose uniformity are measured by secondary ion mass spectroscopy and sheet resistivity, respectively. Results show that the depth profile has the desired features for the projected range, and the dose non-uniformity is 0.7%.

Production of milliampere class mass‐separated multiply charged ion beam

A new type of microwave ion source for a megaelectron volt ion implanter is designed to produce milliampere class multiply charged ion beams. This ion source has a single stage plasma chamber with both a mirror and an octopole magnetic field to produce milliampere class lower‐charge‐state ions efficiently. The extracted ion beam is mass separated, and a Kr2+ beam of 2.3 mA and an Ar2+ beam of 3.0 mA are obtained with absorbed microwave powers of 700 and 570 W, respectively. Combination of this new source with an ion accelerator should realize a milliampere class megaelectron volt ion implanter.

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.

Annealing effect on structural defects in low-dose separation-by-implanted-oxygen wafers

The annealing characteristics of low-dose separation-by-implanted-oxygen (SIMOX) (100) Si have been investigated by transmission electron microscopy (TEM). Samples are prepared by 60, 120, and 210 keV oxygen implantations with doses between 1.0×1017 and 6.0×1017/cm2 at 560 °C, followed by annealing at temperatures between 1000 and 1350 °C for 5 to 60 min in a vacuum of 10-6 Torr. As-implanted layers split into two sublayers during high-temperature annealing. The shallow SiO2 precipitate region is located at around projected range (Rp)/2 instead of damage peak (Dp), while the deep buried oxide layer (BOX) lies at around Rp. Also, during the same annealing stages, cavities and SiO2 precipitates are produced and then dissolved in the near surface region above Rp/2. These experimental results are discussed, referring to the point defect distributions in the substrates obtained by Monte Carlo simulation.