Bonding Pad Over Active Structure for Chip Shrinkage of High-Power AlGaN/GaN HFETs

This paper reports a bonding pad over active (BPOA) structure with photosensitive polyimide (PSPI) as the intermetal dielectric layer to reduce the chip size of high-power enhancement-mode AlGaN/GaN heterojunction FETs (HEFTs) on a 150-mm (6-in) Si substrate. The fabricated AlGaN/GaN HFETs with a BPOA structure exhibited a threshold voltage and a maximum current of 0.6 V and 38.6 A, respectively, at $V_{\textrm {GS}}$ of 6 V. The leakage current was $4.3 \times 10^{-5}$ A at 700 V, which was the same value as that of the AlGaN/GaN HFETs without a BPOA structure. The reliability of the AlGaN/GaN HFETs with the BPOA structure during the packaging process was improved by the PSPI layer and a modified bonding pad structure, which endured the stress during the wedge wire bonding and epoxy molding processes.