Trenching at the Copper Line Edge

FIGURE 17.31 Edge of the line trenching after copper CMP. The left image shows that the copper line edge is an accentuated form of copper pitting. 

FIGURE 17.33 Effect of electron beam exposition time on the low dielectric. The left picture is taken after 2 s of electron bombardment (minimum time to make acceptable focus). The right picture presents the same structure as on the left after 8 s of electron bombardment. The dielectric material has visibly shrunk. Note that these are low-resolution SEM images because the acquisition time of a high-resolution SEM image takes longer than 8 s. 

The copper surface roughness can be a problem for the defect inspection tools. When the sensitivity of the defect inspection tool is increased in order to detect smaller defects, the tool may view copper roughness as a defect. The real defects may be lost in the crowd. In order not to miss the smaller defects, it is important to lower the copper surface roughness as much as possible during 

6 Discoloration—Metals Thickness Variations and/or Dielectric Thickness Variation 

FIGURE 17.37 Very high dishing on a 100 pm square pad structure (left image). The copper in the middle of the copper structure is completely removed this copper CMP process has a very poor topography performance. On the contrary, the picture on the right shows a 200-mm wafer with SEMATECH mask 862. Only the largest 25-mm copper pad is dished down to the bottom. This copper CMP process exhibits excellent planarization performance. 

---