Abstract
An unique type of residues with ring shape was detected at high topography metal surface after the via etch process, which is plasma dry etching with the combination of isotropic etch and anisotropic etch. This process needs to etch through the Inter Metal Dielectric (IMD) stack consists of High Density Plasma (HDP) Undoped Silicate Glass (USG), SIlicon Oxy-Nitride (SION) and TetraEthylOrthoSilicate (TEOS). This ring shape residues formed during the isotropic etch and could not be etched away in the subsequent anisotropic etch, and it was found to be induced by the significant etch rate differences between TEOS and SION, coupled with the fluctuations in the TEOS thickness and the isotropic etch rate. The detailed mechanism on the formation of this ring shape residue and the solution to this issue are discussed in this paper. The solution has been proven to be effective with no trace of via ring shape residues since the implementation.
Published Version
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