Samsung just announced today that they have begun mass production of the industry's first 3D TSV technology based DDR4 modules for enterprise related products. Samsung has said: "announcing that we have begun mass producing the industry's first 64GB DDR4 RDIMMs that use 3D 'through silicon via' (TSV) package technology. The new 64GB TSV module performs twice as fast as a 64GB module that uses wire bonding packaging, while consuming approximately half the power."
"Samsung's volume production of 3D TSV modules marks a new milestone in the history of memory technology, following the company's initial production of 3D Vertical NAND (V-NAND) flash memory last year. While 3D V-NAND technology embraces high-rise vertical structures of cell arrays inside a monolithic die, 3D TSV is an innovative packaging technology that vertically interconnects stacked dies. With its introduction of the new TSV modules, Samsung has further strengthened its technological leadership in the '3D memory' era. Samsung has worked on improving 3D TSV technology since it developed 40nm-class* 8GB DRAM RDIMMs in 2010 and 30nm-class* 32GB DRAM RDIMMs in 2011 using 3D TSV. This year, Samsung started operating a new manufacturing system dedicated to TSV packaging, for mass producing the new server modules."
In order for Samsung to build these 3D TSV modules, the dies are ground down to a few dozen micrometers, and then pierced to contain hundreds of fine holes. Electrodes passing through the holes allow them to be vertically connected and stacked. In the future Samsung believes they will be able to stack more than four dies using 3D TSV technology.