Mechanisms of Metallic Impurity Deposition on Silicon Substrates Dipped in Cleaning Solution

A theoretical and experimental study of metallic deposition on silicon substrates was carried out in the cleaning solutions most widely used in microelectronics. This study highlights three preponderant deposition mechanisms: ( i ) physisorption due to van der Waals interactions between the substrate and metallic impurities, ( ii ) chemisorption which results from electrons commonly shared between the substrate and metallic impurities, and ( iii ) metal displacement due to a transfer of electrons between the substrate and metallic impurities. In addition, the solution ionic strength and the polarity of the impurities and of the silicon surface are shown to be relevant parameters which govern the transfer of impurities from the heart of the solution to the substrate.