Impact of introducing CuSiN self-aligned barriers in advanced copper interconnects

Self Aligned Barrier Approach: Overview on Process, Module Integration and Interconnect Performance Improvement Challenges

“…CuSiN process, which is fully compatible with existing materials and processes, evidenced a nearly 10x TTF improvement with respect to a SiC barrier [26], using a stand-alone CuSiN process in a 90 nm technology node and 3 decades higher TDDB performance than SiCN were demonstrated [5]. These results make this process an accurate solution regarding performance requirements expressed within the ITRS roadmap for the 45 technology node.…”

“…It consists in a three steps process ( Figure 1.a-d) [4][5][6]: i) First, native Cu oxide is removed and surface is activated using reducing plasmas; for instance, H 2 -based cleaning plasmas were shown to be more efficient than NH 3 for ii) Cu silicidation, i.e. copper enrichment with Si atoms using Si-based precursor decomposition (CVD) such as silane or tri-methyl silane.…”

“…Indeed, except for CuSiN [4,5], the via is opened on a new material, i.e. CoWP or W, not directly on Cu, and etch process must be tuned accordingly.…”

“…As a consequence, etching plasmas must be tailored to SAB composition to avoid any degradation of the ULK material ( Figure 6.c), or any over-etching (laterally and vertically) due to polymer removal at this stage of the process (Figure 6.d). However, etch issues are also related to the SAB thickness: for instance, whereas an ultra-thin capping such as CuSiN may be completely etched during the dielectric opening step, or during standard punch-through metallization [4,5], thick metallic deposited films will require the introduction of adapted plasmas for a direct contact with Cu. In fact, it is proposed that the SAB is partially preserved to simplify the integration scheme, or completely etched to lower via resistivity.…”

“…(left & middle) CuSiN/SiN bi-layer simultaneous formation mechanisms during CuSiN process and (right) TEM cross-section observation[5].…”