The microstructure of submicrometer wide planar-reactive ion etched versustrench-damascene AlCu lines

The microstructure was measured for AlCu lines, formed using either a tradi tional planar metal subtractive etch process or a newly developed hot AlCu- trench-damascene process. It was found that 0.35 mu m wide damascene AlCu l ines formed a large grained bamboo microstructure with little or no Al (111 ) texture. The local crystallographic texture was measured in a scanning el ectron microscope using electron backscatter pattern analysis often referre d to as backscatter Kikuchi diffraction. Damascene structures consisted of AlCu films deposited at greater than 400 degrees C onto Ti or Ti/TiN into p reformed amorphous SiO2 trenches, 0.3-5.0 mu m wide by 0.4 mu m deep, follo wed by aluminum chemical mechanical polishing to remove the metal overburde n. Standard planar metal control samples consisted of blanket Al or AlCu fi lms deposited onto either an amorphous SiO2 substrate or onto SiO2/Ti/TiN s ubstrates, followed by subtractive etching to define 0.45-10 mu m wide line s as well as large (e.g., 10x10 mu m(2)) pads. The planar metal samples exh ibited either little change or a slight strengthening of their (111) fiber texture with decreasing line width; this was in sharp contrast to the damas cene films in which a marked weakening in the (111) fiber texture with decr easing line width was found. In addition a trimodal (111) texture distribut ion developed in trenches where TiAl3 intermetallic formed. The role of int ermetallic formation (TiAl3), elevated (> 400 degrees C) AlCu deposition te mperature, large bamboo grain size, local AlCu crystallographic texture and differences in sidewall coverage between subtractive etched and trench-dam ascene processed AlCu on film microstructure are examined. (C) 2000 America n Institute of Physics. [S0021-8979(00)00322-4].