Impact of mobile charge on matching sensitivity in SOI analog circuits

Elements such as sodium and potassium can contaminate oxides in semiconductor devices, including buried oxides in Silicon-On-Insulator (SOI) devices. Common fabrication processes use chemicals which contain such contaminants - an example being chemical-mechanical polish slurries - which can contain high levels of sodium or potassium. When charge contamination, particularly mobile charge contamination, gets under SOI devices, it can shift characteristics such as threshold voltage, and when this happens in sensitive analog circuits, it can lead to yield and reliability issues. We will describe an example and suggest possible layout mitigation strategies.