Effect of ions and radicals on formation of silicon nitride gate dielectric films using plasma chemical vapor deposition

We have clarified effects of ions and radicals on the film property of ultrathin silicon nitride (SiNx) films of 5 nm in thickness formed on Si substrates at 300 degreesC in electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) employing ammonia and silane (NH3/SiH4), and nitrogen and silane (N-2/SiH4) gases. In situ Fourier transform infrared reflection absorption spectroscopy and in situ x-ray photoelectron spectroscopy confirmed that in N-2/SiH4 plasma, Si-N bonds in the film were increased by eliminating charged species, and thus, radicals promoted the formation of the SiNx film of high Si-N bond density. On the other hand, Si-N bonds in the film were decreased by eliminating charged species, and eventually, ions played an important role in forming the film of high Si-N bond density in NH3/SiH4 plasma. The excellent hysteresis of 0.04 V was successfully achieved with the NH3/SiH4 plasma. Furthermore, the quadrupole mass spectroscopy suggests that NH4+ charged species make a significant contribution to the formation of ultrathin SiNx films with high quality. These results provide insights into important species to be controlled in the PECVD for low temperature formation of the SiNx gate dielectric films in ultralarge scale integrated circuits. (C) 2001 American Institute of Physics.