Plasma diagnostics for the characterization of etching and deposition reactors

The characterization of plasmas in realistic etching/deposition tools, using two fast, non-intrusive diagnostics, microwave interferometry and radio-frequency (rf) current-voltage measurements, are presented here. The advantage of these kinds of diagnostics is that they allow real-time plasma data to be taken without interference to the process. Using these diagnostic tools, the plasma characteristics of three etch/deposition systems, the rf-parallel-plate diode and triode reactors, and an electron cyclotron resonance (ECR) reactor have been studied.; The impedance characteristics and electron density behavior for argon, a gas used in sputter-deposition processes, and sulfur hexafluoride, SF{dollar}sb6,{dollar} an etchant gas, have been investigated in a 13.56 MHz parallel-plate diode reactor, as a function of pressure and power. Pressures in the range of 20 to 400 mTorr and rf-generator powers (the nominal power) from 50 to 1500 W were studied. Electron density is an important plasma parameter; it determines the rates of production of reactive species and ions and provides a basis for process monitoring and real-time control. Microwave interferometry provides an absolute measure of the line-integrated electron density of the plasma. The impedance characteristics of the plasma provide important processing information for matching-network design, while the actual power coupled to the plasma (the plasma power) is important for reactor performance correlations. Both of these parameters can be derived from rf-current and voltage measurements. The stray impedances inherent in such high frequency measurements have been corrected for by applying the technique of unterminating and deembedding from microwave engineering.; The current-voltage measurements have been extended to the triode reactor, and to the rf-biased electrode-chuck of an ECR (electron cyclotron resonance) etch tool. In both these reactors, the plasma generation mechanism and the ion-impact energies are in some measure decoupled. This decoupling allows for better control of the ion-impact energy, which enhances the materials processing capabilities of these tools. Both the rf-parallel plate triode and the ECR reactors achieve this decoupling through a separate independently powered electrode, used for control of the ion energies. The perturbations introduced in the plasma by these ion energy control electrodes are examined through the use of current and voltage measurements. The extent of decoupling between the plasma generation and ion acceleration mechanisms is investigated in the case of the triode and the ECR. A term known as the power defect is used to characterize the effectiveness of the decoupling. The power defect is the fraction of power put by the secondary electrode of the triode and the rf-biased electrode of the ECR into processes other than sheath ion acceleration.