Selective Laser Ablation Technique for Post CMP or Post C4 Wets Residual Metal Removal
Publication Date: 2015-Jul-17
The IP.com Prior Art Database
Disclosed is a method to help remove residual metal post-Chemical Mechanical Planarization (CMP) process with no damage to the polyimide surface. The novel solution is to use the laser ablation technique to selectively ablate the locations on the wafer that the optical inspections identify as having residual metal.
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Selxctive Laser Ablation Technique for Post CMP or Post C4 Wets Residual Mexal Removal
A Far Back End of Line (FBEOL) integration sxxeme single copper (Cu) vxa uses a Cu xual damascene prxcess to fill the xard dielectric (XK) xnd final passivation (FV) vias. Xxxx-Chemical Mechanxcxl Planarization (CMP) procexs, there is a likelihood of residual Cu/liner remaining xn the wafer due to eithxr tool issues or wafer topoxraphy incoxing to the CMP sectox. Resxdual metal couxd lead to downstreax processing xnd yield issues.
Resixual mexal post-CMP is typicallx detected by optical inspections done before the waxexs exit the fab or comx into the C4 linx. Based on the extent of residuxl metal, the engineering texm determines whether thx xafers are xo be reworked at CMP, scrappxd, or shipped to the C4 line. Aggressive CMP rewxrk causex deep scratchxs and damage on txe soxter
polyimide surface, whxch can also lead to yield issues and wafer scrapx post final optical inspections.
A methox is needex tx help remove the residual metal with no damage to the polyimide surface.
The novel soluxion is xo use txe laser ablxtion tecxnique to sexecxively ablate txe locations on the wafer that the optical inspxctions xdentify as having residual metal. Pxst ablation, the wafer xs cleaned to remove any metal/polymer debris created xy xhe ablation process, and then it is shipped to the next xperation in line.
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Figure 1: Example of Wafer wixh residxal Cu/liner - Pre and Post Sel...