AVS 49th International Symposium
    Microelectromechanical Systems (MEMS) Thursday Sessions
       Session MM+TF-ThM

Paper MM+TF-ThM8
A New Approach to Electrical Characterization of Spin-on Dielectrics for Power MEMS Applications

Thursday, November 7, 2002, 10:40 am, Room C-210

Session: Development and Characterization of MEMS Materials
Presenter: A. Modafe, University of Maryland
Authors: A. Modafe, University of Maryland
R. Ghodssi, University of Maryland
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We have developed a new method and special-purpose test structures for electrical characterization of spin-on low-k dielectrics for Power Micro-Electro-Mechanical Systems (MEMS) that operate under high voltages. The spin-on low-k dielectrics in this study are ACCUGLASS T-12B, a methylsiloxane-based spin-on glass (SOG) from Honeywell and CYCLOTENE 3022-35, a polymer based on B-staged bisbenzocyclobutene (BCB) monomer from Dow Chemical. Due to their simple, low-temperature processes, these materials are suitable for the inter-level dielectric layer in a Power MEMS device, in this case a bottom-drive variable-capacitance micro-motor supported on micro-ball bearings. The existence of relatively high voltages makes the electrical components of the device, especially the inter-level dielectric more vulnerable to failure. Furthermore, the likelihood of failure increases with time due to absorption of moisture and dust. The proposed method performs capacitance and current vs. voltage measurements (C-V and I-V) on the inter-digit comb-type and spiral-type capacitor test structures to characterize the electrical properties of the dielectric film under test, i.e. dielectric constant, dielectric strength, leakage current, and their dependency on absorbed moisture and operation time. The measurement of the dielectric constant is based on a geometry-extractor method that compares the capacitance of the test structure before and after dielectric deposition. The dielectric constant is calculated by extracting a geometry factor representing the shape of the test structure from the C-V test. The dielectric constant measurement error is minimized using the extracted geometry factor, instead of measuring the geometrical features in separate experiments. The measurement of the dielectric strength and the leakage current is based on a ramped voltage-stress (RVS) method using the I-V test on the developed test structures. Preliminary results for electrical characterization are presented.