Ultra thin power amplifier module with embedded passives and actives on aluminum substrate

We introduce new hybrid integration technology with high density interconnection (HDI). A Power Amplifier module (PAM) for the 1.9 GHz Korea-PCS band is fabricated using embedded passives and actives on selectively anodized aluminum substrate. 2.5 mm × 2.5 mm Al₂O₃ layers more than 120-μm thick are selectively anodized from an aluminum substrate and then a Hole 1200 μm × 960 μm × 125 μm in volume, to fit MMIC die, is formed on each Al₂O₃ layer by chemical etching. An InGaP HBT MMIC die is directly bonded to the aluminum substrate inside this hole to effectively dissipate heat to the aluminum substrate. An organic layer is coated on the Al₂O₃ layer in order to flatten the surface of the Al₂O₃ layer where the MMIC die is accommodated inside. Thin film process is followed to fabricate passive devices, transmission lines and direct interconnections among the electrodes on the MMIC die and the passives. Finally, a 2.5 mm × 2.5 mm × 0.3 mm PAM with fully integrated passives, an embedded active and a high density interconnection (HDI) is successfully fabricated and the fabricated PAM exhibits a 28.3 dB power gain and, 43% power added efficiency (PAE) under a supply voltage of 3.2 V.