A new tungsten gate metal oxide semiconductor capacitor using a chemical vapor deposition process

A new process for tungsten gate metal oxide semiconductor (MOS) capacitors has been developed using chemical vapor deposition (CVD) of tungsten on a thin poly-Si layer of appropriate thickness. The poly-Si acts as a sacrificial layer and is consumed during the CVD of tungsten (W). This process yields a nearly pure W metal gate after Sill, reduction of WF6 at 300 degrees C. Compared with sputtered tungsten films, the CVD tungsten film has lower resistivity and lower intrinsic film stress. In addition, the CVD tungsten metal gate MOS capacitor has a lower interface state density (D-it) and a higher charge-to-breakdown (Q(bd)), than sputter-deposited tungsten gate MOS capacitors.