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Advanced Nobel Metals (Gold, Palladium, Rhodium,Platinum)/Ta Plating Seed Layer for Damascene Sub-Micron Pitch Cu Coil for Recording Head and Microelectronic Devices Disclosure Number: IPCOM000015414D
Original Publication Date: 2002-May-02
Included in the Prior Art Database: 2003-Jun-20

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For Conventional Cu plating process of sub-micron holes for damascene Copper (Cu) application, conducting seed layers such as Cr/Ta/Cu or Cu/Ta/TaN have been used for the plating process. however , upon long time air exposure between seed layer deposition and plating cause the seed layer to oxidize, removed during immersion into Cu plating solution and subsequently causing problem such as incomplete hole filling and plating of Cu films . Instead of conventional Cu/Ta/Cu or Cu/Ta/TaN seed layer, Inert noble metal such as Gold (, Palladium or Pt or Rh)/Ta seed layers are deposited (by Ion Beam Deposition or Collimated PVD) as composited seed layers for Cu plating process. The Gold/Ta are better Cu/Ta seeding layer since gold is not oxidized easily and more stable in Cu plating solution chemistry. This layer is also more suitable and better for recording head Cu coil than NiFe/Cu or Co/Cu seed layers since it is nonmagnetic, much more stable and less reactive to various Cu plating solution . Gold films have better adhesion an can be used to initiate Cu plating in case the Cu seed layer sidewall coverage is insufficient. Au, Rd (or Pd or Pt) is non magnetic, stable, less oxidizing than other materials like Ta/Cu or Ta/TaN/Cu This Au seed layer is more compatible head fabrication since Au diffusion is an issue for Silicon device (but not for MRAM). Below are the FIB/SEM cross section (figures 1 and 2) of 0.9 um pitch coil deposited with IBD 2000A Gold/ 200 A Ta and then plated in Copper bath . It can be seen that the high aspect ratio (4:1) structure plating quite well even with a slight entrance. Figure 1- FIB/SEM cross section of 0.9 um pitch coil with Gold/Ta seed layer 1