8“ uniform electron cyclotron resonance plasma source using a circular TE₀₁ mode microwave

A new type of electron cyclotron resonance (ECR) plasma source has been developed using a circular TE₀₁ mode microwave converted from the principal TE₁₀ rectangular mode. The ion saturation current density of 36 mA/cm₂ is achieved for the input microwave power of 3 kW at the nitrogen gas pressure of 5 x 10^-4 Torr. The uniformity of the ion saturation current density is within ±3% over 8 inches in diameter, which is better than that produced by a conventional TE₁₁ mode microwave. The mean ion energy at the substrate position in this ECR plasma source is in the range of 20-30 eV, depending on the shape of magnetic fields. The direction of ion motion is confirmed by etching test to be almost perpendicular to the wafer and to be useful for fabricating ULSI circuits on wafers larger than 6 inches in diameter.