A Research of the Micro-Damage of the Backside TSV Heterogeneous Microstructure after CMP Process with Alkaline Slurry

Through silicon via (TSV) technology is widely used to achieve 3D integration of integrated circuits. Chemical mechanical planarization (CMP) is a mature technology to achieve both local and global planarization which can be applied in the traditional 1st back side via reveal (BVR) process during the back side thinning and flattening of TSV wafers. In this paper, the surface and subsurface micro-damage of the TSV heterogeneous microstructure after back side CMP process was observed and characterized by cross-sectional transmission electron microscope (TEM) measurements, microscopic high resolution Raman spectra and I-V curves were also measured. As the results, CMP introduces micro-damage to surface and subsurface of Cu (local defects), of interface between Cu and barrier material (bimetallic corrosion), of Si (amorphous layers) and of insulation material (leakage current). The results illustrate that CMP induced amorphous Si layer shows barrier property, CMP changes the barrier property of Ti/TiN little, slurry formulation changes the insulation property of polished TEOS much, the addition of 5 mM BTA to CMP slurry and the controlling of pH≈10.5 can help to protect the back side surface of TSV wafers during CMP and to reduce the surface and subsurface damage of the back side metal structures. The conclusions in the research will guide the further research of TSV back side CMP and BVR process.