Intra-stack sealing of tier interconnects using the interconnect alloy

Abstract

Interlayer cooling has been demonstrated to enable heat removal scaling in true 3D integration. This technology will unavoidably expose tier interconnects to coolant. If using electrically conductive liquids, such as water based coolants, the interconnects require a sealing mechanism to protect from short-circuiting. As an efficient technological solution we present a concentric ring sealing, realized around the interconnect in the very same alloy, thereby forming a joint of its own. We compare different aspect ratios of upper and lower joining parts, as well as single joint sealing and multiple joint sealing. We demonstrate the post-bonding states of the sealing using CuSnAg, AuSn transient liquid phase bonding (TLPB) and Cu-Cu thermocompression bonding. We lay emphasis on the resulting intermetallic compounds and present shear strengths of consistently beyond 30 MPa, reaching up to 85 MPa, which clearly shows the feasibility of the concept.