Semiconductive behavior of and the fabrication of ap-n junction diode from amorphous polymer-derived ceramics

The electrical properties of high temperature semiconducting silicon oxycarbonitride (SiCNO) using titanium nitride (TiN) interconnects are studied. This research had three objectives. The first was to fabricate possible high temperature electrical ceramic and to construct metallic interconnects on SiCNO. The interconnect was selected by investigating the reaction between metals and SiCNO in powders by x-ray characterization of the reaction products. It was concluded that TiN is the most suitable interconnect material. In the final process TiN was produced by coating SiCNO with Ti by RF magnetron sputtering and then heat-treating at high temperatures in argon or nitrogen atmosphere to form TiN. The phase transformation from Ti to TIN starts at 1000°C, however optimum condition for the formation of TiN layer was found to be 1200°C for 2 hours. X-ray analysis on the coated and heat-treated surface reveals presence of TiN and TiO2 phases. The TiN coating was found to be stable up to a maximum temperature of about 1400°C without any noticeable degradation, which was confirmed X-ray analysis. The second was to study the electrical properties of silicon oxycarbonitride (SiCNO) at temperature up to 1300°C as a function of their composition. Silicon oxycarbonitride was made with processing temperature between 1100°C and 1400°C. Their electrical conductivities at temperature up to 1300°C were measured as a function of their chemical compositions that were already analyzed for each processing conditions. As varying processing temperature, their chemical compositions were changed and affect their electrical conductivity. The ratio of nitrogen and oxygen in SiCNO affected their electrical conductivity changes. Polymer-derived SiCNO ceramics remained semiconductive at all temperature and followed Mott's variable range hopping (VRH) mechanism for amorphous semiconductor. From the carrier concentration by Hall-effect measurement of SiCNO ceramics, their hopping energy and distance were also calculated by the Mott's variable range hopping theory. For each processed condition of SiCNO ceramics, their density of states, hopping energy, and hopping distance were found to be N(E) = 4.8 x 1017 ∼ 5.9 x 1018 (eV·cm 3)-1, W = 0.017 ∼ 0.047 (eV), and R = 13.4 ∼ 21.8 (nm), respectively. The third was to make a microelectric device, such as diode etc., using photo-polymerized SiCNO and Silicoboron oxycarbonitride (SiBCNO) which is made by adding boron in SiCNO system. Their semiconductive p/n type was determined by thermoelectric power measurement. SiCNO showed p-type and SiBCNO showed n-type semiconductive behavior. Based on their different semiconductive type, the p-n junction diode was successfully fabricated and its properties were characterized. The p-n junction diode from polymer-derived ceramics shows Zener diode properties with breakdown at voltage of about 32 volt and a reverse saturation current of about 2∼3 mA.