COPPER DISTRIBUTION NEAR A SiO2/Si INTERFACE UNDER LOW-TEMPERATURE ANNEALING

In relation to the thickness of a surface SiO2 film, the behavior of Cu atoms existing at the SiO2/Si interface during low-temperature annealing (less than or equal to 400 C) is investigated by an analytical method combining step-etching and multi-angle total reflection of X-ray fluorescence. SiO2 thickness plays an important role in the re-distribution of Cu. For a 2-nm-thick SiO2 film, Cu diffused from the interface to the SiO2 surface. On the other hand, in a 5-nm-thick SiO2 film, Cu diffused toward the bulk. This Cu re-distribution behavior also affected the electrical characteristics, such as Dit and Vth, of the MOS capacitors. The degradation of oxide breakdown characteristics after 400 C annealing suggests that Cu atoms move around in the SiO2 film before leaving the interface. 23 refs.