Atmosphärisches Plasmaspritzen zur Kupfermetallisierung leistungselektronischer Halbleiterbauelemente

Description

Atmospheric plasma spraying is an innovative manufacturing technology that offers a cost-effective and flexible alternative to conventional Copper metallization in power electronics. It enables the flexible deposition of thermo-mechanical bond-buffers. During the spraying process, spherical copper powder is applied at high particle temperatures and low velocities, resulting in a lamellar, transversely isotropic coating structure in which copper oxides are embedded. A thermal post-treatment with hydrogen homogenizes the coating and reduces oxide content, thereby enhancing electrical properties. Throughout the process chain, the high thermal input induces thermo-mechanical stresses in the semiconductor chip, which results in strong chip warpage. The post-treatment mitigates these effects by promoting grain recrystallization. For successful ultrasonic wire bonding of thick copper wires, both cohesion and adhesion of the plasma-sprayed coating play a crucial role. However, hydrogen embrittlement reduces cohesion, leading to delamination and internal fractures within the coating. Adhesion, in contrast, is primarily influenced by the surface roughness of the semiconductor chip, which is determined by its cell structure. By optimizing process parameters, it is possible to achieve reliable and durable aluminum wire bonds on plasma-sprayed copper metallization which double the lifetime of a wire-bonded power module without changing the manufacturing chain.