All hot wire CVD TFTs with high deposition rate silicon nitride (3 nm/s)

Abstract

Using the hot wire (HW) chemical vapor deposition (CVD) method for the deposition of silicon nitride (SiN x ) and amorphous silicon (a-Si:H) thin films we have achieved high deposition rates for device quality materials up to 7.3 nm/s and 3.5 nm/s, respectively. For thin films of SiN 1.3, deposited at 3 nm/s, the mass-density of the material reached a very high value of 3.0 g/cm 3. The silane utilization rate for this fast process is 77%. The high mass-density was consistent with the low 16BHF etch rate of 7 nm/min. We tested this SiN 1.3 in “all hot wire” thin film transistors (TFTs), along with a-Si:H material in the protocrystalline regime at 1 nm/s. Analysis shows that these “all hot wire” TFTs have a V th = 1.7–2.4 V, an on/off ratio of 10 6, and a mobility of 0.4 cm 2/V s after a forming gas anneal. We therefore conclude that the HWCVD provides SiN x materials with dielectric properties at least as good as PECVD does, though at a much higher deposition rate and better gas utilization rates.