Cu wire bonding process induced fail mechanism — Inter Layer Dielectric Crack

Converting gold wire to copper wire for IC packaging is a common strategy to achieve challenging cost reduction goal in semiconductor industry. This trend has both advantage and disadvantage. This cost effective solution also creates all kinds of quality, reliability issue. Inter Layer Dielectric crack, known as ILD crack, is one of the most common fail mode inducing at wire bonding stage. In this paper, several experiments are shown to proof that ultrasonic (USG) is the most critical factor to induce IC inter layer dielectric (ILD) crack out of wire bonding parameters by physical analysis. Furthermore, a novel concept about the ILD crack root cause investigation is delivered and supported by several real cases. In short, wire bonding process is not always the only cause of an ILD crack event. Metal line layout design and wafer fabrication process variation should also be checked to identify the real root cause.