Abstract
The transport of copper in silicon dioxide thermally grown on single crystalline silicon was studied by capacitance techniques, secondary ion mass spectroscopy (SIMS) analysis, and Rutherford backscattering spectrometry (RBS). Metal/oxide/silicon (MOS) capacitors were used to study the penetration of copper into the oxide as a function of temperature and applied electric field. The role of a titanium layer between the copper and the oxide was also studied. Bias‐thermal stress (BTS) studies of MOS structures were conducted at 150°C to 300°C with an electric field of 1 MV/cm for times ranging between 10 min and 168 h. It is shown that without bias a relatively small amount of copper reaches the silicon/silicon dioxide interface, with a maximum surface concentration of about 1017 cm−3 that drops exponentially with depth in the oxide. The high‐frequency (100 kHz) capacitance vs. voltage (CV) characteristics of the MOS devices changed drastically when a positive bias was applied to the gate and copper reached the silicon/silicon‐dioxide interface. The penetration time for copper through the oxide was characterized as a function of the temperature. The copper drift velocity, mobility and diffusivity in the oxide were determined and the copper profiles in the capacitors were characterized by SIMS. The activation energy for the diffusivity and mobility models was found to be 
. Devices without a barrier layer, which were stressed under a positive electric field, showed high copper concentration in the oxide, up to 1021 cm−3. At high temperatures and long stress times a significant amount of copper was also found in the silicon substrate. A titanium layer thicker than 5 nm acted as effective barrier even after 30 h of BTS at 300°C.