Integrated AlGaN/GaN HEMTs in MCM-D technology

High packaging density and low cost integration of active and passive components are becoming the key issues in the modern wireless communication market. Early developments have shown that multi-chip module with deposited thin film (MCM-D) technology can be an effective candidate for system-in-package (SiP) realization. In this paper, we present the demonstration of integrating SiC based AlGaN/GaN high electron mobility transistors (HEMTs) with high-quality passive components in a thin-film technology. The MCM-D technology developed at IMEC uses alternating layers of BCB and electroplated Cu combined with TaN resistors and Ta2O5 capacitors integrated on a high-resistivity Si substrate. Within this platform, wirebonding techniques are used to connect in-house fabricated AlGaN/GaN HEMTs with thin-film substrates, forming a SiP approach. The design frequency of the power amplifier is 5.5 GHz, while a class-AB bias condition has been selected. Measurement results show that the fabricated module can deliver an output power of 1.6 W together with a drain efficiency of 28%, and further measured data at high drain voltage indicate that the circuit has the potential to obtain a maximum output power of 4.1 W, 2.6 W and 2.5 W at 2 GHz, 4 GHz and 5.5 GHz, respectively. Due to the inherently larger breakdown field of AlGaN/GaN HEMTs, the presented prototype can offer a 1.6–10 times higher output power than the reported MCM and LTCC PA modules based on conventional technologies such as Si-MOSFET, InGaP/GaAs, pHEMTs, etc. The major benefit of using a single-package approach with MCM-D technology is the dramatic cost reduction compared to an MMIC and the size reduction compared to a hybrid PCB approach.