3Di (3D integration) refers to a family of technologies which enable the stacking of active Si layers with vertical connections between them. 3Di has the ability to enhance chip performance by increasing bandwidth, reducing wire delay, and enabling better power management. Several researchers have investigated TSV (Through Silicon Via) fabrication, insulation, metallization, integration, the impact of TSVs on devices, thermo-mechanical integrity and reliability of TSVs. This paper presents a review of some of these publications in order to understand the options and challenges in 3Di.