Mechanical Polish Clean Up After M2 CVD W Blanket Etch for CMOS Dram
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
A process sequence is disclosed for achieving planarity after a chemical vapor deposition (CVD) tungsten (W) process step used in a CMOS process to form second level (M2) via studs. Because a non-uniform film thickness of tungsten is created when chemical vapor deposition processes are utilized, current planarization techniques do not achieve their desired effect. A description of the process sequence which creates the problem is shown in Figs. 1-3. Fig. 1 shows a structure of patterned oxide, nitride with CVD W on top. (Note the non-uniform thickness (T1, T2 and T3) of the CVD W.) Fig. 2 shows the structure after a blanket reactive ion etchback process. (Note the undesirable combination of results possible, i.e., over etched studs, over etched nitride and residual W left on the surface.) Fig.