Microstructure and Texture in Copper Filled Millimeter Scale Through Silicon Vias

The microstructure and crystallographic texture of copper electrodeposits in millimeter scale through silicon vias are characterized using electron backscatter diffraction. The deposits obtained from additive-containing CuSO₄-H₂SO₄ electrolytes are characteristic of the superconformal deposition process, with growth textures and columnar grains consistent with previous findings in smaller TSV. The microstructure, like the filling evolution it records, changes substantially with chloride concentration for the concentrations of polymer suppressor used. With chloride concentrations of 80 micromol·L^-1 and less, columnar grains of Cu capture the linear motion of the local growth front during filling with a strong <110> orientation along the elongated grain axes typical of deposition in chloride-containing Cu electrolytes. In the mid- and upper- via locations these columnar grains are angled upward from the sidewalls toward the center of the v-shaped growth front. In a limited region adjacent to the via bottom they extend vertically from the bottom surface. With millimolar chloride concentration, deposition also exhibits columnar grains with preferred <110> growth orientation in the lower region of the via and adjacent to the sidewalls. However, separation of the central deposit from the sidewalls results in a convex geometry of the growth front and spatially varying texture in most of the deposit.