A large-area electron cyclotron resonance (ECR) plasma is generated by using permanent magnets and applying the whistler-mode launching of microwaves. A uniform plasma is produced with the uniformity of ±3.5% over 20 cm and ±1.8% over 16 cm in diameter; the plasma space potential is about 17 V with the uniformity of ±1% over 20 cm. The maximum ion current density is about 11.5 mA·cm-2. The purity of the produced plasma is high. No damage was found after the operation for 100 h with the microwave power of 600 W.

This paper describes an improved large-diameter electron cyclotron resonance (ECR) source which employs a strip-bar antenna. By launching a 2.45 GHz microwave near the magnetic field of permanent magnets of alternative polarity set along closed loops, an ECR plasma is produced. The source diameter is 30 cm. The characteristics of an oxygen plasma produced with this modified source are an electron density of 1.4 × 10 11 cm −3 , electron temperature of 3 eV and space potential with respect to the chamber wall of less than 20 V. A high plasma density of uniformity within ±3.8% over 30 cm is achieved.

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