Improved package reliability of AlGaN/GaN HFETs on 150Â mm Si substrates by SiNx/polyimide dual passivation layers

- The output power of the AlGaN/GaN HFETs was reduced after TO-220 plastic package.
- The passivation layer was cracked during the plastic package.
- The SiNx/PSPI layers prevented filler-induced stress and fluorine ion diffusion.
- The SiNx/PSPI layers are promising passivation for suppression of output power drop.

In order to prevent reduction of output power of AlGaN/GaN heterostructure field effect transistors(HFETs) with inorganic passivation layer such as SiO2 and SiNx after TO-220 plastic package, SiNx/photosensitive polyimide(PSPI) dual layers were proposed as passivation layers for high power, enhanced mode AlGaN/GaN HFETs on 6 in. Si substrates. The PSPI layer can endure the filler-induced mechanical stress during the plastic package, followed by prevention of the passivation layer cracking and metal deformation. Furthermore the SiNx layer can suppress the diffusion of fluorine ions during curing of the PSPI layer, which causes the reduction of 2DEG concentration due to the strong electronegativity of fluorine ions. The results showed that output power of the AlGaN/GaN HFETs with the SiNx/PSPI dual passivation layers was not deteriorated even after plastic package process, which can be attributed to prevention of the filler-induced stress and fluorine ion diffusion by the dual passivation layers.