3D Integration challenges today from technological toolbox to industrial prototypes

3D integration, also referred as “More than Moore” approach is considered as the most attractive alternative to “More Moore” concept in order to increase circuit functionalities and performances while keeping reasonable cost of integrated devices. This technology has been widely presented and discussed during last years and is now available on several world wide integration platforms. Major part of the work done in recent years was focused on the three challenges to be overcome to allow manufacturing of 3D technology: design, process integration and tests. This was presented [1] as the availability of a complete toolbox including the design kit definition, the development and maturity increasing of the required process modules such as TSV, Wafer bonding and debonding, back side contact, both side interconnects and the definition of functional and reliability tests. This toolbox is dedicated to the construction of specific process flows and designs depending on the targeted applications. These applications, in the 3D integration world, are very flexible going from the passive and active interposers to memory on logic or logic on logic partitioning as well as stackable processors. Today, the different process modules are at a sufficient maturity state to allow the realization of demonstrators for all types of integration schemes. Depending on the type of integration flow and requested device, challenges to perform this demonstrator can come from the process integration itself but also from the need of specific equipment toolset. Base wafers already containing devices for 3D demonstrator can come from various site and be of different size. The demonstrator can be fully realized from bulk silicon as it is the case for an interposer or the 3D part of the device, only, will have to be developed which will be the case for heterogeneous integration. For this, a new 300 mm pilot line was built in Leti in addition to the 200 mm one and was designed to be compatible with manufacturing lines. These facilities are today allowing the realization of 300 mm 3D demonstrators. Results of these prototypes and the challenges overcome for integration are discussed in this paper.