Effect of DC bias voltage on the characteristics of low temperature silicon-nitride films deposited by internal linear antenna inductively coupled plasma source

The characteristics of silicon-nitride deposited at the temperature lower than 100 °C using an internal linear-type inductively coupled plasma were investigated as functions of the NH3/SiH4 ratio and ion bombardment energy applied to the substrate (dc bias voltage) for use as the gate dielectric material of flexible display devices. Decreasing the NH₃/SiH ₄ ratio to 2 and increasing the dc bias voltage to -150 V decreased the Si-O bonding and increased the Si-N bonding, resulting in a more nitrogen-rich SiNx thin film. In addition, the capacitance-voltage measurement of the metal-insulator-semiconductor devices fabricated with the SiNx thin film deposited at various dc bias voltages showed a hysteresis curve in the cyclic voltage measurement and the increase of the dc bias voltage with decreasing hysteresis voltage. The interface trap density measured at a dc bias voltage of -150 V and NH₃/SiH₄ ratio of 2 showed the lowest interface trap charge density of about 2 × 1011 cm^-2. Under these conditions, the dielectric constant was as high as 7.2.