Diagnosing Research On Spatial Nonuniformity Of Dual-frequency Capacitive Coupled Plasma

The application of plasma technology in material processing plays important roles in new technology revolution, which is the most active research area in vacuum technology and material science. Having the advantage of independent control of the ion flux and bombardment energy to the wafer, a new plasma processing technology utilizing dual frequency capacitive coupled plasma (DF-CCP) had been developed in recent years and used more and more in microelectronic industry. For these applications, it is great meaningful to study the properties of this type of discharge using diagnosis means for further understanding of its physical processes. Up till now, it has not been fully developed of the theory model and the physical mechanism of DF-CCP, due to the complexity and difficulties brought by the second frequency source added to the single radio frequency discharge.In DF-CCP, the diagnose method of traditional Langmuir probe will be severely disturbed by dual radio signals so that it can't work correctly, and the methods such as choke and assistant electrode using in single frequency discharge diagnose will have little effect to reduce the disturbance and have much difficulties in application, which is due to the short gap length of the two electrodes (-2cm) and the complex harmonic component that exits in the dual frequency signals. So there is a pressing need to develop methods and equipments in both industrial production and science research.To solve this problem, we have developed a virtual instrument based double probe diagnose system, realized complete floating of the probe system to the discharge circuit, so that effectively avoided the dual frequency disturbance to the probe measurements. Using this probe system, we successfully diagnosed the DF-CCP (60MHz/2MHz), and obtained detailed radial and axial distribution of the electron density and temperature under various discharge conditions.