Rapid Assessment of Aluminum Nitride Properties and Applications Towards 4-inch AlN-based MMICs

AlN provides significant advantages for advanced electronics with its ultrawide bandgap (6.2 eV), high critical electric field (15 MV/cm), and excellent thermal conductivity (~340 W/mK), promoting efficient heat dissipation essential for high-frequency circuits. Its compatibility with GaN and AlGaN HEMTs enhances integration by eliminating lattice mismatch and thermal boundary issues, enabling compact, high-power devices. However, the electrical permittivity (?) of AlN, a crucial property for electromagnetic wave propagation and device performance, must be characterized across frequencies to ensure suitability for MMIC production. Despite the importance of high-frequency characterization, current data for AlN, particularly for its anisotropic properties, are sparse and inconsistent. Accurate measurement of these permittivities up to W-band frequencies (30-300 GHz) is proposed to assess the quality of AlN substrates for MMIC applications.To properly assess AlN’s material properties, high-quality AlN substrates will be thinned to 100-300 microns for MMIC fabrication. These substrates will be analyzed to understand defect impacts on frequency-dependent loss via resonator and transmission line fabrication. The team will design, fabricate, and characterize AlN permittivity using novel Fabry-Perot and substrate-integrated waveguide (SIW) resonators. SIWs will separate metal and dielectric losses by temperature dependencies, allowing precise characterization of real and imaginary parts of ?|| at millimeter-wave frequencies. The characterization will be conducted at Cornell's High Frequency Testing Laboratory using a vector network analyzer. Success criteria include completed SIW resonator masks, fully fabricated SIW resonators, and ? characterization up to 75 GHz. The final effort of the project focuses on the design, fabrication, and characterization of transmission lines, leveraging the permittivity and loss tangent data to ensure transmission lines with return loss < 10 dB and insertion loss < 0.6 dB/mm up to 75 GHz.In parallel to the technical development, the team will assess Army relevant applications, identifying a beachhead market for which AlN-platform MMICs are most urgently needed. Looking at both the technical results and DoD customer discovery information, the team will make an assessment on the feasibility of AlN-platform MMICs for RF applications.