Microwave ion source for ion implantation

Abstract

Fundamentals of microwave ion sources used for ion implantation as well as their main features are reviewed and evaluated. Ion sources using plasmas generated by microwave discharge in a magnetic field have many advantageous features. Since they operate even with reactive source materials, they can provide long-life stable ion beams for a variety of ion species. They can provide either multiply-charged ion beams or high-current ion beams of singly-charged ions depending on selected operational conditions. High-current beams of singly-charged ions can be extracted in various sizes and forms. An ion source that extracts an ion beam of 40 mm diameter through a multiaperture lens can provide argon, hydrogen and oxygen ion beams of several hundred mA at 5 kV. The ion current can be further increased by increasing the volume of the discharge chamber and the area of the multiaperture lens. An ion source that extracts a slit-shaped beam suitable for ion implantation can provide mass-separated currents of 10 mA (maximum 15 mA) for As + and P + as well as various metal ions of several mA. Due to versatility of beam extraction, this ion source has been modified to a higher voltage (120 kV) by combining a double-stage extraction lens, and to a higher mass-separated current (30 mA) by lengthening the ion exit slit.