| 초록 |
Interconnections are increasingly determining the limitations in density, performance, and reliability of ultra large scale integration (ULSI) and require new materials and deposition technologies for more complex structures.Until now, aluminum(resistivity = 2.67Ωcm) and its alloys have been used as an interconnect material, but these alloys are susceptible to electromigration failure and their resistivities are still not low enough to operate at ultrahigh speed. Recently, copper(1.67Ωcm) is suggested as an interconnecting material which replace aluminum. Since the geometry of interconnector has a severely restricted morphology(width < 0.18㎛, aspect ratio = 1:5), it is very difficult to obtain a compact Cu filling which does not reduce a Cu conductivity in itself. Leading candidate for the copper deposition technology is electroplating because of high productivity and low cost. To fill copper compactly inside trenches, inhibitor and leveller is required because an ohmic-drop between trench tip and mouth exist. We propose three additives, which are polyethylene glycol(PEG), chloride ions and benzotriazole(BTAH). When such additives are present in small concentrations in the bulk electrolyte, their consumption rate at the electrode surface can be affected by mass transfer process, and inhibition of the deposition reaction tends to be more pronounced where diffusion layer thickness is smaller. Furthermore, to fill copper without void and seams in copper electroplating, copper grain size control is necessary and current waveform should be modulated. Current waveform can be classified ; direct current method, on-off pulse waveform, reverse pulse waveform, and etc. Especially, copper grain size can be controlled by different pulse waveform. In this work, we investigate the effect of additives on Cu electrodeposition by using rotating disc electrode (RDE). Different current waveforms were applied for controlling the grain size.
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