Direct probing on large-array fine-pitch micro-bumps of a wide-I/O logic-memory interface

In order to obtain acceptable compound stack yields for 2.5D- and 3D-SICs, there is a need to test the constituting dies before stacking. The non-bottom dies of these stacks have their functional access exclusively through large arrays of fine-pitch micro-bumps, which are too dense for conventional probe technology. A common approach to obtain pre-bond test access is to equip these dies with dedicated pre-bond probe pads, which comes with drawbacks such as increased silicon area, test application time, and reduced interconnect performance. In order to avoid the many drawbacks of dedicated pre-bond probe pads, we advocate the usage of advanced probe technology that allows to directly probe on these micro-bumps. This paper reports on the technical and economical feasibility of this approach.