Fabrication technologies for dual 4-kbit stacked SRAM

The process technologies for realizing a 3-D LSI are reported with emphasizing the high quality laser recrystallization and the thermally stable interconnects. A homogeneous recrystallization of the silicon island array was achieved all over a wafer by the dual laser beam recrystallization method (DLB), in which the 2-dimensional energy distribution of the laser beam was precisely controlled. Thermally stable interconnects in the 1st layer were realized by W wiring and stoichiometry controlled W/WSi/Si contact structure. By these key technologies, the 8-kbit CMOS SRAM with two-active layers has been fabricated. It was confirmed that these technologies were available to fabricate the 3-D LSI.