An embodiment includes an apparatus comprising: a first layer, including a first semiconductor switching element, coupled to a first portion of a first bonding material; and a second layer, including a second semiconductor switching element, coupled to a second portion of a second bonding material; wherein (a) the first layer is over the second layer, (b) the first portion is directly connected to the second portion, and (c) first sidewalls of the first portion are unevenly serrated. Other embodiments are described herein.