Experimental and numerical studies on nonlinear plasma series resonance effect in capacitively coupled radio frequency glow discharge plasma by homogeneous discharge model

Abstract

Self-excited nonlinear plasma series resonance (PSR) heating is observed in low pressure capacitvely coupled radio frequency (CCRF) plasma as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma and lead to increased the plasma density1. A negative dc potential is also known to develops between the bulk plasma and the power electrodes, which is termed as ‘self bias’ in RF plasma and make the CCRF plasma suitable for different material processing applications. This self bias is generated as a result of the geometrical asymmetry of the electrodes, which can be achieved by appropriately design the area of the powered and the grounded electrodes. However, independent control of the dc self bias in single frequency CCRF plasma is not possible, since the changing in any operating parameters including geometrical asymmetry will also change the plasma parameters. In addition, no such dc self bias is generated in geometrically symmetric CCRF plasma. A study on the dual frequency CCRF plasma could be useful in understanding the separate control of the dc self bias and plasma density, which respectively determine the ion energy and ion flux. Another aspect of the study on the dual radio frequency plasma could be the generation of the dc self bias in geometrically symmetric CCRF plasma. In our previous work, we have studied the PSR effect1 and developed a geometrical symmetric CCRF plasma model2,3 on the based on homogeneous discharge model4. In this work, details on the results obtained for independent control of ion energy and ion flux, generation of dc self bias in geometrically symmetric CCRF plasma and PSR heating in single as well as dual frequency CCRF glow discharge plasma will be discussed. In addition, preliminary studies on the extension of the model to atmospheric pressure rf plasma torches will be also presented.