Effect of plasma and heat treatment on silicon dioxide films by plasma-enhanced atomic layer deposition

Silicon dioxide films were deposited using di-isopropylaminosilane and Ar/O ₂ plasma by the plasma enhanced atomic layer deposition (PE-ALD) system. Film depositions were carried out at a temperature range of 50-200 °C, while the plasma exposure time within the PE-ALD cycle varied from a very short time of 0.3 s to a sufficiently long time of 4.0 s. The growth per cycle, wet etch rate (WER), dielectric constant, and leakage current of as-deposited samples were significantly decreased with increasing in-cycle Ar/O ₂ plasma time. At the same time, the hydrogen content in the film, of which the presence was found in the form of Si-OH from Fourier transform infrared analysis, was shown to be decreased according to the elastic recoil detection measurements. The increase in the growth temperature also affected the decrease of the aforementioned film properties; however, the influences were insignificant compared to the in-cycle plasma time. In addition, the effect of the postplasma treatment after the whole process was limited merely on the upper layer of the film. Meanwhile, the postannealing process of the films resulted in different thickness shrinkages depending on the densified degree of the as-deposited film. Moreover, the film properties including WER, hydrogen content, dielectric constant, and leakage current were decreased to levels comparable to or more improved against thermal oxide.