Dimitris Lymberopoulos

Synchronous Pulse Plasma Operation upon Source and Bias Radio Frequencys for Inductively Coupled Plasma for Highly Reliable Gate Etching Technology

Synchronous pulse operation upon both source and bias RFs for inductively coupled plasma (ICP) etching system, having both dynamic matching networks and RF frequency-sweeping to ensure the lowest RF reflected power, is introduced for the first time. A superior performance of synchronous pulse operation to conventional continuous wave (cw) as well as source pulse operations is confirmed through plasma diagnostics by using Langmuir probe, plasma simulation by using hybrid plasma equipment model (HPEM) and etching performance. Significant reduction of RF power reflection during pulse operation as well as improvement of 35 nm gate critical dimension (CD) uniformity for sub-50 nm dynamic random access memory (DRAM) are achieved by adapting synchronous pulse plasma etching technology. It is definitely expected that synchronous pulse plasma system would have a great ability from a perspective of robustness on fabrication site, excellent gate CD controllability and minimization of plasma induced damage (PID) related device performance degradation.

Temporal fluctuations: A fingerprint of surface chemical reactions

A real-time fast Fourier transform of temporal fluctuations of optical emission and rf power signals captures surface chemical reactions. The observed fluctuations, previously considered as noise and traditionally time averaged, depend on process chemistry and surface materials. The coherent optical emission fluctuations are specific only to the etch by-products. Plausible explanations, such as plasma density or electron temperature modulations, plasma instabilities, rf coupling modulations, or external hardware effects are dismissed by the data. It has been confirmed that the observed frequency patterns are directly related to surface chemical reactions of the film exposed to the plasma. This finding can be used to diagnose, monitor, and control chemical surface reactions in real time.