Pulse tuning cycle

While electrodeposited copper represents considerable promise for HDI and VLSI applications, simple insertion of the additive chemistry or PRC processes developed for PTHs application are not likely to be successful. Furthermore, while new additive chemistries may initially be successful, the extreme tolerances and associated control issues, impurity incorporation, and waste associated with CMP prohibit the chemistry-only approach. By considering the fundamental differences associated with the PTH and HDI as well as VLSI applications, we have developed a modulated reverse electric field process (MREF) for copper electrodeposition. In contrast to the long cathodic duty cycle-short anodic duty cycle used in the PRC process, the MREF process consists of a short cathodic duty followed by a long anodic pulse. By tuning the frequency and the cathodic to anodic charge ratio (Qc/Qa), conformal and filling capability are demonstrated for vias and trenches in the 0.5 to 100 pm size range. 

FIGURE 11.21 An example of a clock atomic transition. The excitation probability of the clock transition (the atomic oscillator) is measured through the quantum jump number vs. the laser tuning of the local oscillator. Each probe pulse is of 90 ms duration, and twenty probe cycles were performed for each value of the detuning. (Reproduced with the permission of the Physikalisch-Technisehe Bundesanstalt.)... 

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