Dielectric ALD with Hydrogen Peroxide: Comparative Study of Growth and Film Characteristics for Anhydrous H₂O₂, H₂O₂/H₂o Mixtures, H₂o and Ozone

Abstract

ALD of dielectrics requires new precursor chemistries. Recent development efforts have focused on new Organometallic, Organosilicon and Organoaluminum precursors. Our research focus has been on oxidants, and specifically hydrogen peroxide reactivity. Due to this reactivity, hydrogen peroxide use may allow lower deposition temperatures and achieve distinct properties in the resulting film when compared to other oxidants. Our research study uses: Gas-phase hydrogen peroxide, delivered from an anhydrous, ampoule-based formulation by use of a membrane delivery system. High concentration H 2 O 2 /H 2 O delivery by in situ concentration methods and use of a membrane vaporizer as a gas generator. Initial results for ALD growth of ZrO 2 from anhydrous H 2 O 2 and CpZr(N(CH 3 ) 3 ) exhibit high quality growth of film at 260° C. Minimal saturation delay and a linear growth curve were observed. XPS and XRR were used to characterize ZrO 2 composition, showing significant similarities to films grown using ozone. Subsequently, films grown using ALD and H 2 O 2 were placed into MIMCAP structures, which had high k values measured at 35. This was a slight improvement over films grown with 20% ozone concentration which had high k values of 32. Novel Gas Generator Our approach involved development of a novel gas generator that delivers H 2 O 2 /H 2 O mixtures. A carrier gas is connected to this generator, which delivers up to 5% H 2 O 2 /21% H 2 O gas by volume from 30wt% H 2 O 2 liquid solution (H 2 O/H 2 O 2 =4.2). This gas mixture enables SiO 2 films to be grown at highly reduced temperature compared to water. Initial testing was done with tris(dimethylaminosilane) (N(CH 3 ) 2 ) 3 SiH and H 2 O 2 /H 2 O. SiO 2 was deposited at temperatures at least 200° C lower with the hydrogen peroxide mixture than with water. Titanium dioxide ALD is of interest for several applications. The unique properties of this material make it an attractive candidate for advanced patterning applications. Here, low temperature deposition is required (100-250° C). Key required properties of the resultant film include film density and wet etch rate, where low wet etch rates are needed for selective etching of SiO 2 vs TiO 2 . Moreover, high growth per ald cycle (GPC) is needed for increased manufacturing throughput. For TiO 2 ALD, we began our study with tetrakis(dimethylamino)titanium (TDMAT) precursor. Our initial goal was to compare the growth and film properties of Ozone (O 3 ) vs Water (H 2 O) vs H 2 O 2 /H 2 O mixtures. Initial results show that H 2 O 2 /H 2 O mixtures can be grown at growth rates (GPC) 10-20% higher than H 2 O and 20-50% higher than O 3 . More significantly, the H 2 O 2 /H 2 O mixtures generate films with wet etch rates (WER) much lower than the traditional oxidants. At 125° C , over 50% reduction in WER was observed for H 2 O 2 /H 2 O vs H 2 O and over 70% reduction was observed for H 2 O 2 /H 2 O vs O 3 . Additional comparision data will be reported on wet etch rates, refractive index and composition. Initial composition results by XPS show that residual carbon and nitrogen for the H 2 O 2 /H 2 O film grown at 125° C are non-detectable vs 1.1% carbon and 1.1% nitrogen for Ozone at 125° C. Compositional correlations will be made with respect to wet etch rates. Figure 1