Titanium nitride as electrode for MOS technology and Schottky diode: Alternative extraction method of titanium nitride work function

摘要

Titanium nitride (TiN) films have been used as gate electrodes in metal-oxide-semiconductor (MOS) capacitors, which were fabricated with SiO_2 layer as gate dielectric, and as upper electrodes in Schottky diodes on Si substrates. The TiN layer has presented the electrical resistivity of 270 μΩ cm and poly crystalline structure (Ti_2N and TiN phase formation), which were extracted by four probe testing, and, X-ray diffraction and Raman spectroscopy, respectively. To get both MOS and Schottky devices on the same substrate, with TiN/SiO_2/Si/Al and TiN/Si/Al structures, respectively, 300 nm thick TiN layer was simultaneously deposited by DC sputtering process on SiO_2/Si and on Si on the same n-type substrate. The MOS capacitors and Schottky diodes were sintered in conventional furnace in forming gas at 450 ℃ for different annealing times between 5 and 30 min. These devices were electrical characterized by capacitance-voltage (C-V) and current-voltage (I-V) measurements, respectively. With both measurements from capacitors and diodes fabricated on the same substrate, the TiN work function values were extracted, resulting in values between 4.5 and 4.2 eV. These values agree with results from literature. Our TiN work function extraction method presents higher accuracy, due to two different measurements were carried out to extract the same parameter, and lower defect incorporation on semiconductor surface can occur, because both devices were fabricated on the same substrate at the same conditions. Furthermore, the distortion in MOS capacitor C-V curve is reduced at 10 min of sintering process, indicating that the charge density at TiN/SiO_2/Si/Al structures is reduced to one level of 1010 cm~(-2). From the I-V curves of Schottky diodes, the ideality factor between 1.0 and 1.5 was extracted. And, these excellent results, such as low charge density of 1010 cm~(-2), the ideality factor of 1.0, and work function of 4.2 eV, indicates that TiN electrodes can be used for MOS technology and Schottky diode.