HIGH-Q COPPER / POLYIMIDE INDUCTORS: FABRICATION RESULTS AND ELECTRICAL PERFORMANCE ANALYSIS
M. B. PISANI, C. HIBERT, M. PAVIUS, D. BOUVET, P. BEAUD, C. DEHOLLAIN, A. M. IONESCU

Abstract. This paper presents fabrication and electrical characterization results obtained during the development of a 2-metal level copper / polyimide process for high-quality factor integrated inductors fabricated using thick metal layers (4 µm) over an insulated low-resistivity silicon substrate (0.3 Ω cm). S-parameter measurements were performed and inductance and quality factor as function of the frequency were extracted. We demonstrate inductors with peak quality factor arround 10, which is a remarkable value using low-resistivity substrates. Measured performance was limited by the contact resistance between the 2 metal layers, a processing issue that is being addressed. Simulations replacing the low-resistivity silicon by a high-resistivity one show the possibility to obtain quality factors in excess of 10 over a wide frequency range.

Index Terms: Cu low k, high quality factor inductor, copper tantalum polyimide, RF IC passive device, electromagnetic simulation and parameter extraction.