Through Silicon Via (TSV)

A through silicon via, also abbreviated as TSV, is basically a connection that passes through the silicon wafer. These connections are considered to be extremely high performing and high quality interconnects, especially when creating three dimensional integrated circuits and packages. This is because they can be used for vertical stacking to allow the various integrated circuits placed on top of a single 3D package to consume less space yet still have high connectivity and performance. They also allow for interposer layers in between the integrated chips to further increase the size and width of the 3D package in terms of capacity and performance, yet as small and flat as possible when it comes to physical dimensions.

Through Silicon Via Types

There is a total of three kinds of through silicon vias or TSVs based on the manner they have been manufactured.

Via-first TSVs

This is when the TSV is fabricated before the actual device has been patterned or the metal layers have been laid down.

Via-middle TSVs

This is when the TSV is fabricated after the front end of line process has been completed but before the back end of line part begins, i.e. before the metal layers are put down. This is the most popular method of TSV development and deployment when it comes to interposer stacks and three dimensional integrated chips.

Via-last TSVs

This is when the TSV is fabricated after both the front as well as the back end of lien processes have been accomplished.

Through Silicon Via Applications

Through silicon vias allow for the creation of chips that are smaller yet boast extremely high functionality and performance, making them the perfect interconnects for 3D packages and 3D integrated circuits. A 3D package typically comprises of two or more integrated circuits that have been stacked on top of one another vertically. TSVs eliminate the need to use edge wiring when the ICs are stacked on top of each other by creating vertical connections through the silicon wafers and removing the additional interposer layer, making the package smaller in length as well as flatter. A 3D integrated circuit, on the other hand, comprises of multiple silicon wafers that connected through TSVs along their vertical alignment as they are stacked on top of each other, thus creating a smaller footprint while behaving as a singular, cohesive device. Through silicon vias are also used in image sensors, such as CIS technology where they replace wire bonds. By doing so, they reduce the form factor and allow for instruments that have a much higher density.