An amorphous silicon blocking mask for MOSFET after gate channel implants and bipolar implants in advanced BiCMOS technology

A thin amorphous silicon layer is used to protect the gate oxide from subsequent photoresist, implantation, and cleans during BiCMOS processing. Channel implantation after gate oxidation may then be used to create a more localized dopant distribution under the gate, improving transistor performance without degrading the gate oxide integrity.