In this article, we report film properties of HfO2 and La2O3 gate dielectrics grown on Si(100) substrate using atomic layer deposition (ALD) with various surfaces modified before film growth. The precursors used for HfO2 and La2O3 films are hafnium tetrachloride (HfCl4), lanthanum tris[bis(trimethylsilyl)amide] (C18H54N3LaSi6) and water. Pre-deposition treatments examined for HfO2 dielectric films include (1) surface nitridation using NH3, N2O, or NO, (2) substrate annealing in an oxidizing or reducing ambient, and (3) surface fluorination. These results were compared to those obtained using established approaches of growing HfO2 on an OH terminated surface produced chemically. Linear film growth was observed for the HfO2 with all pre-deposition treatments. Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) and transmission electron microscopy (TEM) analysis indicated that all pre-treatments result in good film coverage with no interaction between HfO2 and silicon at the silicon substrate. The as deposited ALD HfO2 film is mainly amorphous, continuous, and relatively smooth on all pretreated Si surface. The thickness of a thin interfacial layer varies depending on the particular pre-treatments. Similar studies were also conducted for the growth of ALD La2O3. In this case, a significant interaction between La2O3 and silicon substrate was observed on films grown directly on chemical oxide. A rough interface between La2O3 and the silicon substrate is clearly seen in XTEM results. This interaction is more significant when the film is deposited at higher temperature. The XTEM images showed that the ALD La2O3 films are mostly amorphous. Results show that independent of surface pre-treatments, interactions between La2O3 and the silicon substrate occur for the deposition conditions explored here. Electrical characterization using evaporated platinum electrodes and mercury probe of the high-k film stacks have been carried out to determine the impact of the pre-treatments on the electrical properties of the films. Results indicated that ALD HfO2 films have higher dielectric constant, lower leakage and better flatband voltage stability during post deposition annealing compared to ALD La2O3 films. These results indicate that ALD HfO2 is a more promising candidate than ALD La2O3 due to superior thermal stability in contact with silicon.

Articles you may be interested inCharacterization of advanced complementary metal-oxide-semiconductor processes with reverse secondary ion mass spectrometry profiling Approach to the characterization of through-oxide boron implantation by secondary ion mass spectrometry

Reduction in surface roughness during secondary ion mass spectrometry depth profiling with an ion-milling method J.Effects of oxygen flooding on crater bottom composition and roughness in ultrashallow secondary ion mass spectrometry depth profiling Secondary ion mass spectrometry analysis of through-oxide ion implantation in silicon often exhibits strong matrix effects across the SiO 2 /Si interface. In this study we explored the analytical conditions that required minimal correction for the variation in the relative sensitivity factors and the sputtering rates across the interface. We found that an O 2 ϩ beam at 1 keV and 46°provided an equal sputtering erosion rate for SiO 2 and Si. Under these sputtering conditions, the SiO 2 surface remained smooth, but Si became rough ϳ50 nm below the SiO 2 /Si interface. A complete depth profile of B implantation through oxide was obtained by utilizing the 1 keV 46°O 2 ϩ beam in SiO 2 and across the SiO 2 /Si interface and a 1 keV 60°O 2 ϩ beam deeper in the Si substrate. The data exhibited an apparent drop in the concentration of the implanted B at the SiO 2 /Si interface which was attributed to a phase transition in the matrix from amorphous to crystalline. In addition, analyses of an ion-beam synthesized oxide ͑5 keV O 2 ϩ at normal incidence͒ confirmed the occurrence of outdiffusion of B in the altered layer. Also, the results indicated preferential sputtering of B at the surface.

Articles you may be interested inUltralow energy boron implants in silicon characterization by nonoxidizing secondary ion mass spectrometry analysis and soft x-ray grazing incidence x-ray fluorescence techniques Ion yields and erosion rates for Si 1 − x Ge x ( 0 ≤ x ≤ 1 ) ultralow energy O 2 + secondary ion mass spectrometry in the energy range of 0.25-1 keV On the migration behavior of metal impurities in Si during secondary ion mass spectrometry profiling using lowenergy oxygen ionsThe ever increasing interest in surface analysis techniques with excellent depth resolution, great detection sensitivity, and good throughput has been a driving force for development of dynamic secondary ion mass spectrometry using low energy primary beams. This work investigated sputtering erosion of Si and emission of secondary ions from Si bombarded by sub-keV O 2 + beams at glancing incidence. It was demonstrated that surface roughening remained minimal for 250 and 500 eV O 2 + beams at an angle of incidence above 80°but developed rapidly at angles between 60°a nd 80°. The depth resolution for B and Ge appeared very different at the glancing incidence and changed dramatically in opposite ways as the angle of incidence decreased. The difference in the depth resolution was explained by the different diffusion/segregation behavior between B and Ge during O 2 + bombardment. In general, the use of sub-keV O 2 + beams at the glancing incidence ͑above 80°͒ favored a thinner altered layer, a short surface transient, a minimal apparent shift in depth profiles, a better depth resolution ͑not for B in Si͒, a good sputter rate, but a poor yield of the positive secondary ions. To address the issues with the low ion yield, we identified optimal cluster ions for common dopant such as boron and nitrogen. Good sensitivity was achieved for analyses of boron in Si by detecting BO 2 − as the characteristic secondary ion. A parallel study published elsewhere suggested SiN − as an ideal candidate for detection of nitrogen in ultrathin oxynitride ͓Z. X. Jiang et al., Surf. Interface Anal. ͑in press͔͒. For analyses of thin SiGe films in Si at glancing incidence, detection of Ge + provided fairly good sensitivity. Applications of an O 2 + beam at 250 eV 83°for analyses of shallow boron implant demonstrated superior accuracy in the measured near-surface boron distribution. Also the characterization of thin SiGe films exhibited excellent depth resolving power for Ge in Si although the ion yield of Ge + was low.

The compatibility of ALD and CVD metal deposition with mesoporous and microporous carbon-doped organosilicate glass (OSG) films was examined. Blanket film studies using TEM, TOF-SIMS, and positron lifetime spectroscopy demonstrate that ALD Wand TaN penetrate deep into the mesoporous film via the film's connected pore structure. In contrast, metal penetration into microporous OSG films was not observed. He and NH3 plasma pretreatments to the mesoporous OSG film surface did not seal the mesopores to ALD metal penetration, but the plasmas did damage the bulk of the mesoporous OSG film with varying severity. The results indicate that porosity, pore size, and/or pore structure regulate ALD/CVD precursor diffusion and that ALD metal deposition is a good probe of pore sealing strategies.