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|A Low Temperature Process to Integrate High K-Low Loss Pyrochlore Films in Organic Substrates for Thin Film RF Capacitors|
|Keywords: capacitors, RF components, thin film|
|Unlike perovskites such as barium titanate, pyrochlores have low loss and stable properties with temperature and frequency while retaining a moderately high dielectric constant. Hence, these are ideally suited for RF capacitor components. Unfortunately, pyrochlores are generally formed at above 400 C making them difficult for organic compatible integration either on BCB build-up layers on Si or traditional organic substrates. We present a new process to convert perovskites into pyrochlores at room temperatures by ion irradiation technique. This new process can embed thin film capacitors directly on organic substrates with a capacitance density of 200 nF/cm2. The process starts by depositing a thin layer of Ti by e-beam evaporation, followed by converting it to barium titanate using chemical solution reactions. The film is then transformed into a pyrochlore phase at less than 100 C by oxygen ion irradiation. The results were confirmed with XRD, SEM, low frequency and high frequency dielectric constant and Temperature Coefficient of Capacitance measurements. By a combination of wet chemical treatment followed by oxygen ion irradiation, this technique shows the feasibility of depositing a low TCC (<100 ppm/C), low loss (<0.005) and high capacitance density film (200 nF/cm2) directly on plastic substrates at temperatures less than 150 C, with adequate Break Down Voltages and leakage current behavior. Current RF thin film capacitors are either polymer-based with low capacitance density, or high temperature vacuum-deposited (PECVD/MOCVD thin film) or LTCC based composites. These cause serious limitations for RF integration and miniaturization. This new process is expected to enable complete RF integration for various applications such as matching networks, filters and even tunable components such as phase shifters.|
|P. Markondeya Raj , Assistant Research Director
Georgia Institute of Technology