Abstract: To prevent moisture and oxygen permeation into flexible organic electronic devices formed on substrates, the deposition of an inorganic diffusion barrier material such as SiN x is important for thin film encapsulation. In this study, by a very high frequency (162 MHz) plasma-enhanced chemical vapor deposition (VHF-PECVD) using a multi-tile push–pull plasma source, SiN x layers were deposited with a gas mixture of NH3 /SiH4 with/without N2 and the characteristics of the plasma and the deposited SiN x film as the thin film barrier were investigated. Compared to a lower frequency (60 MHz) plasma, the VHF (162 MHz) multi-tile push–pull plasma showed a lower electron temperature, a higher vibrational temperature, and higher N2 dissociation for an N2 plasma. When a SiN x layer was deposited with a mixture of NH3 /SiH4 with N2 at a low temperature of 100 °C, a stoichiometric amorphous Si3 N4 layer with very low Si–H bonding could be deposited. The 300 nm thick SiN x film exhibited a low water vapor transmission rate of 1.18 × 10 −4 g (m 2 · d) −1, in addition to an optical transmittance of higher than 90%.

Crystalline thin films of silicon nitride have been grown on a variety of substrates by microwave plasma-enhanced chemical vapor deposition using N2, O2, and CH4 gases at a temperature of 800 deg C. X-ray diffraction and Rutherford backscattering measurements indicate the deposits are stoichiometric silicon nitride with varying amounts of the alpha and beta phases. Scanning electron microscope imaging indicates beta-Si3N4 possesses six-fold symmetry with particles size in the submicron range. In one experiment, the silicon necessary for growth comes from the single crystal silicon substrate due to etching/sputtering by the nitrogen plasma. The dependence of the grain size on the methane concentration is investigated. In an another experiment, an organo- silicon source, methoxytrimethylsilane, is used to grow silicon nitride with controlled introduction of the silicon necessary for growth. Thin crystalline films are deposited at rates of 0.1 micrometer/hr as determined by profilometry. A growth mechanism for both cases is proposed.

The large amount of literature on the technology of thin film silicon nitride indi cates the interest of the Department of Defense, NASA and the semiconductor industry in the development and full utilization of the material. This survey is concerned only with the thin film characteristics and properties of silicon nitride as currently utilized by the semiconductor or microelectronics industry. It also includes the various methods of preparation. Applications in microelectronic devices and circuits are to be provided in Part 2 of the survey. Some bulk silicon nitride property data is included for basic reference and comparison purposes. The survey specifically excludes references and information not within the public domain. ACKNOWLEDGEMENT This survey was generated under U.S. Air Force Contract F33615-70-C-1348, with Mr. B.R. Emrich (MAAM) Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio acting as Project Engineer. The author would like to acknowledge the assis tance of Dr. Judd Q. Bartling, Litton Systems, Inc., Guidance and Control Systems Division, Woodland Hills, California and Dr. Thomas C. Hall, Hughes Aircraft Company, Culver City, California in reviewing the survey. v CONTENTS Preface. i Introduction 1 Literature Review. 1 Bulk Characteristics 1 Technology Overview. 2 References 4 Methods of Preparation • 5 Introduction • 5 Direct Nitridation Method 8 Evaporation Method • 9 Glow Discharge Method. 10 Ion Beam Method. 13 Sputtering Methods 13 Pyrolytic Methods. 15 Silane and Ammonia Reaction 15 Silicon Tetrachloride and Tetrafluoride Reaction. 24 Silane and Hydrazine Reaction 27 Production Operations. 28 Equipment.