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Hafnium oxides and hafnium silicate films were investigated as a possible replacement for the SiO2 gate dielectric. Hafnium oxide films were formed by reactive sputtering from a single Hf oxide target in a predominantly Ar atmosphere containing small additions of oxygen. Hafnium silicates were made by adding a He-diluted silane gas for Si incorporation. By changing the silane gas flow, different Si atomic concentrations were incorporated into the Hf oxide films. Depositions were performed with the substrate held at temperatures of 22 °C and 500 °C. The chemical composition of the films was determined with nuclear techniques. Optical reflectivity was used to measure the optical band gap. The film morphology was investigated by transmission electron microscopy (TEM) and the electrical properties were measured with capacitance–voltage and current–voltage measurements using aluminum gate capacitors. TEM and electrical measurement showed that a SiO2 interfacial layer of about 3 nm formed at the Si interface due to the oxidizing sputter ambient. This precluded the growth of Hf based high-K films with small equivalent thickness. After correction for the interfacial oxide layer, the dielectric constant was found to decrease from about 21 for Hf oxide to about 4–5 for the Hafnium silicates with low Hf content (3 at. % Hf and 32 at. % Si). The optical band gap was found to increase from 5.8 eV for Hf oxide to about 7 eV for the silicate films. After annealing at 1000 °C followed by a 300 °C postmetallization anneal, negligible flat band voltage shift were measured on hafnium silicate films and good interface passivation was observed. However, leakage currents increased due to the high temperature processing.

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We have examined the stability of Al2O3/Si heterostructures and show that significant Al diffusion occurs into the silicon for temperatures of 1000 °C and more. This may be caused by dissociation of small quantities of Al2O3 and subsequent dissolution of the Al into the silicon. Such diffusion may be reduced, though not eliminated via an interfacial silicon oxynitride diffusion barrier. Using long channel metal gate Al2O3/Si n field effect transistor data, we show that anneals at 1000 °C result in a degradation of the electron mobility by a factor of 2.

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Dealing with nanometer-sized particulate contamination is still one of the major challenges during the manufacturing of yielding semiconductor devices. This is especially true for the increasing number of critical processing steps, where residues of particulate matter need to be removed without mechanically damaging sensitive device patterns and, at the same time, achieve the lowest possible substrate loss. If higher substrate loss would be permitted, a more or less pure chemical mechanism could be employed (e.g. particle undercut by substrate etching and lift-off). However, being only allowed to have statistically seen sub-Angstrom material loss, physical forces need to be integrated jointly with the appropriate chemical support. In this paper we describe particle cleaning techniques, which are based on monodisperse droplet impact, controlled bubble cavitation (acoustic and laser induced), moving contact lines as well as normal-directed extensional flow to meet present and future industry requirements.

To realize environmental and cost benefits it is desirable to reduce the RCA cleaning sequence from its historical SC1 ϩ SC2 combination, in which the particle-removing SC1 solution deposits certain metals, necessitating the metal-removing SC2. One approach is to add a chelating agent to the SC1. Extensive testing of SC1 solutions with addition of the complexing agent 1,2-cyclohexanediaminetetraacetic acid ͑CDTA͒ were performed. CDTA was shown to be more stable than other complexing agents in SC1 solutions, facilitating significant bath life extension. Further, SC1 solutions with CDTA were shown to be capable of removing large quantities of metals from contaminated wafers, comparable to SC2, and preventing deposition of metals. An exception is aluminum, which can deposit from SC1 even with large amounts of added CDTA, but which can be removed by a subsequent dilute (1000:1) H 2 O:HCl step.Semiconductor wafer cleaning has, for nearly thirty years, been dominated by the RCA cleaning sequence. 1 Removal of particles and light organics, as well as complexation of some metals such as Cu by NH 3 , is accomplished using the SC1 solution. This is an aqueous mixture of NH 3 and H 2 O 2 . It effectively removes particles by a slight etching of the substrate, often assisted by the introduction of megasonic energy. Reattachment of particles is prevented because the surface charges of wafers and particles tend to interact repulsively at the solution pH ͑between 9 and 10͒. The SC1 solution, however, is known to deposit metals such as Fe and Al, often by inclusion in the chemical oxide grown by the SC1. This occurs even when high purity chemicals are used. For example, an SC1 solution with 1 ppb of Fe or Ni deposits about 10 12 atoms/cm 2 on a wafer surface. For 1 ppb of Al in solution, the deposition is on the order of 10 13 atoms/cm 2 on the wafer. 2 Deposition typically occurs as metal hydroxides such as Fe͑OH͒ 3 and Ni͑OH͒ 2 , which form easily in solution at higher pH. 3,4 Metal impurities have deleterious device effects such as accelerated gate dielectric breakdown. The International Technology Roadmap for Semiconductors specifies 6 ϫ 10 9 atoms/cm 2 as a target for maximum allowable critical metal concentration in the year 2001. 5 Consequently, the SC2 solution, an aqueous mixture of HCl and H 2 O 2 , is used for removal of metals by dissolution of hydrolyzed species. In addition to adding a chemical step to the process, with associated cycle time, chemical consumption, and waste disposal issues, use of the SC2 solution can result in addition of particles because the surface charges induced at the solution pH ͑around 1͒ are not strongly repulsive.Another problem associated with SC1 is the roughening of bare Si surfaces, which is related to H 2 O 2 decomposition catalyzed by metal contaminants in the chemistry or on the silicon surface. Fe has the most significant effect on H 2 O 2 decomposition, followed by Cu with about an order of magnitude smaller effect. 6 Respiking the solution with H 2 O 2 to maintain concentration...