Deposition of SiNx : H thin films by the electron cyclotron resonance and its application to Al/SiNx : H/Si structures

Abstract

We have analyzed the electrical properties and bonding characteristics of SiNx:H thin films deposited at 200 degrees C by the electron cyclotron resonance plasma method. The films show the presence of hydrogen bonded to silicon (at the films with the ratio N/Si<1.33) or to nitrogen (for films where the ratio N/Si is higher than 1.33). In the films with the N/Si ratio of 1.38, the hydrogen content is 6 at. %. For compositions which are comprised of between N/Si=1.1 and 1.4, hydrogen concentration remains below 10 at. %. The films with N/Si=1.38 exhibited the better values of the electrical properties (resistivity, 6x10(13) Omega cm; and electric breakdown field, 3 MV/cm). We have used these films to make metal-insulator-semiconductor (MIS) devices on n-type silicon wafers. C-V measurements accomplished on the structures indicate that the interface trap density is kept in the range (3 - 5) x 10(11) cm(-2) eV(-1) for films with the N/Si ratio below 1.38. For films where the N/Si ratio is higher than 1.3, the trap density suddenly increases, following the same trend of the concentration of N-H bonds in the SiNx:H films. The results are explained on the basis of the model recently reported by Lucovsky [J. Vac. Sci. Technol. B 14, 2832 (1996)] for the electrical behavior of (oxide-nitride-oxide)/Si structures. The model is additionally supported by deep level transient spectroscopy measurements, that show the presence of silicon dangling bonds at the insulator/semiconductor interface (the so-called P-bN0 center), The concentration of these centers follows the same trend with the film composition of the interface trap density and, as a consequence, with the concentration of N-H bonds. This result further supports the N-H bonds located at the insulator/semiconductor interface which act as a precursor site to the defect generation of the type . Si=Si-3, i.e., the P-bN0 centers. A close relation between interface trap density, P-bN0 centers and N-H bond density is established.