Acceleration of Cu surface precipitation from bulk by adsorbed organic molecules

Cu has the highest solubility and diffusivity in silicon. Hence Cu in the bulk of silicon wafers can easily diffuse to the wafer surface even at room temperature, and is in danger of deteriorating the devices. It is reported that such a Cu out diffusion phenomenon is affected by the wafer surface condition. It is also known that adsorbed organic molecules on the wafer surface can be a factor changing the surface condition. We investigated the correlation between adsorbed organic molecules on the wafer surface and Cu out diffusion. We found that the organic molecules adsorbed on the wafer lower the surface electrostatic potential, and accelerate Cu out diffusion. We also found that Cu precipitates caused by the out diffusion phenomenon lower the surface potential, and then promote the out diffusion of Cu onto the wafer surface.