This paper presents an overview and perspective on processing technologies required for continued scaling of leading edge and emerging semiconductor devices. We introduce the main drivers and trends affecting future semiconductor device scaling and provide examples of emerging devices and architectures that may be implemented within the next 10-20 yr. We summarize multiple active areas of research to explain how future thin film deposition, etch, and patterning technologies can enable 3D (vertical) power, performance, area, and cost scaling. Emerging and new process technologies will be required to enable improved contacts, scaled and future devices and interconnects, monolithic 3D integration, and new computing architectures. These process technologies are explained and discussed with a focus on opportunities for continued improvement and innovation.

The HfO2–Si valence and conduction band offsets (VBO and CBO, respectively) of technologically relevant HfO2/SiO2/Si film stacks have been measured by several methods, with several groups reporting values within a range of ∼1 eV for both quantities. In this study we have used a combination of x-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry to measure the HfO2–Si VBO and CBO of both as-deposited and annealed stacks. Unlike previous XPS based measurements of the HfO2–Si VBO, we have corrected for the effect of charging in the XPS measurement. We find that after correction for charging, the HfO2–Si VBOs are decreased from their typical XPS-measured values, and agree better with values measured by UV photoemission spectroscopy and internal photoemission. We also report values for the rarely reported HfO2–SiO2 and SiO2–Si VBOs and CBOs in HfO2/SiO2/Si stacks. In addition to the band offsets, XPS was used to measure the band bending in the Si substrate of HfO2/SiO2/Si film stacks. Unannealed HfO2 stacks showed downward Si band bending of 0.4–0.5 eV, while annealed HfO2 stacks showed negligible band bending. Finally, we investigated the composition of the SiO2 layer in SiO2/Si and HfO2/SiO2/Si. By decomposing the Si 2p spectra into the spin orbit partner lines of its five oxidation states we observed that the growth of the HfO2 films resulted in the growth of the SiO2 underlayer and an increase by a factor of ∼2.3 in the density of suboxide species of SiO2. Based on the relatively high binding energy of the Si 2p4+ level with respect to the Si 2p0 level and a survey of results from literature, we conclude that the SiO2 layer in the HfO2/SiO2/Si samples we measured does not undergo significant intermixing with HfO2.

In this work we present physical and electrical characterization of HfO2 films deposited using the Dep-Anneal-Dep-Anneal (DADA) deposition scheme. Electrical results from MOSCAP devices fabricated using a low temperature (Gate Last-like) integration flow are presented. In addition we report detailed physical analyses of the films and changes in the films versus as-deposited ALD HfO2 and films undergoing a single post-deposition anneal and show the correlation between observed physical changes in the film and electrical results. Observed physical changes using HR-RBS, HR-TEM, SIMS, XPS and XRR include crystallization, densification, Si intermixing, reduction of in-film carbon and improved etch resistance leading to improved leakage vs. EOT and electrical non-uniformity. Dependence of these changes on the underlying interface layer (e.g. SiO2 vs SiON) is also described.

Crystalline materials with broken inversion symmetry can exhibit a spontaneous electric polarization, which originates from a microscopic electric dipole moment. Long-range polar or anti-polar order of such permanent dipoles gives rise to ferroelectricity or antiferroelectricity, respectively. However, the recently discovered antiferroelectrics of fluorite structure (HfO2 and ZrO2) are different: A non-polar phase transforms into a polar phase by spontaneous inversion symmetry breaking upon the application of an electric field. Here, we show that this structural transition in antiferroelectric ZrO2 gives rise to a negative capacitance, which is promising for overcoming the fundamental limits of energy efficiency in electronics. Our findings provide insight into the thermodynamically forbidden region of the antiferroelectric transition in ZrO2 and extend the concept of negative capacitance beyond ferroelectricity. This shows that negative capacitance is a more general phenomenon than previously thought and can be expected in a much broader range of materials exhibiting structural phase transitions.

Effect of slot plane antenna (SPA) Ar plasma on the reliability of intermediate plasma (DSDS) treated ALD Hf1-xZrxO2 samples with x = 0, 0.31, 0.8 were investigated. The metal oxide semiconductor capacitors (MOSCAP) were subjected to a constant field stress of 27.5 MV/cm in the gate injection mode and the stress-induced flatband voltage shifts and stress induced leakage currents were monitored. The dielectric film deposited without any intermediate step (As-Dep), having the same number of atomic layer deposition (ALD) cycles as DSDS samples was used as the control sample. It was observed that plasma exposure enhances the quality of high-κ film by reducing the number of intrinsic traps in the film and Zr addition further enhances the reliability. Breakdown characteristics also confirm this behavior. Electron affinity variation in HfO2 and ZrO2 and Zr variation seems to contribute to the improvement in DSDS Hf1-xZrxO2 (x = 0.8) by suppressing the oxide trap formation as observed in the Weibull characteristics. DSDS Hf1-xZrxO2 with x = 0.8, therefore, demonstrates a superior equivalent oxide thickness (EOT) downscaling ability and good reliability performance.

In order to enhance the dielectric properties of HfO2, the alloying of HfO2 with ZrO2 was studied. HfxZr1-xO2 films with different Hf:Zr ratios were deposited by atomic layer deposition (ALD) combined with a cyclical deposition and annealing scheme (termed DADA) in which an annealing was performed after every 20 ALD cycles. The impact of the ZrO2 addition on the structural properties of the ALD grown films was investigated by grazing incidence in-plane X-ray diffraction and pole figure measurement using synchrotron radiation as well as transmission electron microscopy and X-ray photoelectron spectroscopy. The HfxZr1-xO2 films with x=1 show the presence of monoclinic (-111) fiber texture. As the Zr content increases, stabilization of the tetragonal phase is observed. The pole figure measurements indicate the presence of tetragonal (111) fiber texture for the ALD HfxZr1-xO2 films with higher Zr content grown by DADA in contrast to random orientation in post deposition annealed films.

With the replacement of SiO2 by high-k Hf-based dielectrics in complementary metal–oxide–semiconductor technology, the measurement of the high-k oxide bandgap is a high priority. Spectroscopic ellipsometry (SE) is one of the methods to measure the bandgap, but it is prone to ambiguity because there are several methods that can be used to extract a bandgap value. This paper describes seven methods of determining the bandgap of HfO2 using SE. Five of these methods are based on direct data inversion (point-by-point fitting) combined with a linear extrapolation, while two of the methods involve a dispersion model-based bandgap extraction. The authors performed all of these methods on a single set of data from a 40 Å HfO2 film, as well as on data from 20 and 30 Å HfO2 films. It was observed that the bandgap values for the 40 Å film vary by 0.69 eV. In comparing these methods, the reasons for this variation are discussed. The authors also observed that, for each of these methods, there was a trend of increasing bandgap with decreasing film thickness, which is attributed to quantum confinement. Finally, the authors observed a greater variation in bandgap values among the methods for the 40 Å films than among the methods for the 30 and 20 Å films. This is attributed to the larger tail in the extinction coefficient k curve for the 40 Å film.

A low-temperature (320–480 °C) metal-organic chemical vapor deposition (MOCVD) process was developed for the growth of ruthenium and ruthenium oxide thin films. The process used bis(ethylcyclopentadienyl)ruthenium [Ru(C5H4C2H5)2] and oxygen as, respectively, the ruthenium and oxygen sources. Systematic investigations of film formation mechanisms and associated rate limiting factors that control the nucleation and growth of the Ru and RuO2 phases led to the demonstration that the MOCVD process can be smoothly and reversibly modified to form either Ru or RuO2 through simple and straightforward modifications to the processing conditions–primarily oxygen flow and substrate temperature. In particular, films grown at low oxygen flows (50 sccm) exhibited a metallic Ru phase at processing temperatures below 480 °C. In contrast, films grown at high oxygen flow (300 sccm) were metallic Ru below 400 °C. Above 400 °C, a phase transition was observed from Ru to RuOx (0 < x < 2.0) to RuO2 as the processing temperature was gradually increased to 480 °C.