Tungsten/Aluminum First Metal System for Non-Overlapped Second Metal Etched Metallurgy
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
A film of in situ sputter-deposited tungsten (W) on top of aluminum (Al) is reported as a mask for the first level metal (M1) system and is subsequently utilized as an etch stop for the second level metal (M2) etch step. Fig. 1(a) shows the nominal case where M1 Al is defined by a reactive ion etch (RIE). Next, an insulator is deposited and patterned over the first level metal system. The via opening in the insulator is usually made larger than the smallest M1 line to insure a certain contact overlap area. The via sidewalls are sloped for optimum M2 Al coverage. A mask is used to pattern the M2 Al, and the M2 metal is reactive ion etched (RIE M2). The M2 etch and subsequently required overetch definition may cause M1 lines in the M2 cross-over and via regions to be eroded by etching, as shown in Figs. 1(a) and 1(b).