A microwave plasma cleaning apparatus

In a microwave electron cyclotron resonance plasma source, reactive plasmas of oxygen and its mixtures of argon have been used for evaluating plasma cleaning technologies. Small aluminum samples (0.95 x 1.9 cm) were coated with thin films ({le} 20 {micro}m in thickness) of Shell Vitrea oil and cleaned with reactive plasmas. The discharge parameters, such as gas pressure, magnetic field, substrate biasing, and microwave power, were varied to change cleaning conditions. A mass spectroscopy (or residual gas analyzer) was used to monitor the status of plasma cleaning. Mass loss of the samples after plasma cleaning was measured to estimate cleaning rates. Measured cleaning rates of low-pressure (0.5-mtorr) argon/oxygen plasmas were as high as 2.7 {micro}m/min. X-ray photoelectron spectroscopy was used to determine cleanliness of the sample surfaces. In this paper, significant results of the plasma cleaning are reported and discussed.