METHOD FOR FORMING BITLINE TO GUARANTEE CONTACT MARGIN IN FORMING SUBSEQUENT STORAGE NODE CONTACT

摘要

PURPOSE: A method for forming a bitline is provided to guarantee a contact margin in forming a subsequent storage node contact by minimizing a loss of a SiON layer and a silicon nitride layer in a bitline etch process. CONSTITUTION: A tungsten layer, a silicon nitride layer(13a) and a SiON layer are sequentially formed on a semiconductor substrate(10). A photoresist layer pattern is formed on the SiON layer to cover a metal interconnection region. By using the photoresist layer pattern as a mask, SF6 and N2 gas of a plasma state is supplied to the front surface of the substrate to firstly etch the SiON layer. The photoresist layer pattern is eliminated. By using the residual SiON layer after the first etch process and the silicon nitride layer as a mask, Cl2 and NF3 gases of a plasma state are supplied to the front surface of the resultant structure and the tungsten layer is secondly etched to form a metal interconnection.