Variation of stress and resistivity with time, called as self-annealing phenomena, is studied in the copper interconnection layer. In high stress Cu layer deposited on TaN barrier layer, resistivity and stress decrease rapidly with the self-annealing. For instance, resistivity decreases from 2.8 to 2.4 μΩ-cm with releasing of the stress from 32 to 28 MPa by this self-annealing for a week. Such self-annealing effect, however, cannot be observed in low stress and low resistivity copper layer. Resistivity is as low as 2.3 μΩ-cm in as-deposited layer and decreases to 2.1 μΩ-cm in this layer. Depositing of low stress and low resistivity copper interconnection layer can also be achieved by the electroplating torn CHFC solution. Self-annealing phenomena are not appeared in this layer. Just waiting of time until the formation of low stress and low resistivity layer after depositing of high resistivity Cu layer is less meaning. Development of low resistivity copper layer is much more important rather than just waiting of time.
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