Superconducting thin films of Y-Ba-Cu oxide have been prepared on yttria-stabilized zirconia substrates using metal trifluoroacetate spin-on precursors. The films exhibit an extremely sharp resistive transition with zero resistance at temperatures as high as 94 K. The superconducting phase is formed by a three-step process: (a) decomposition of the spun-on trifluoroacetate film to the fluorides, (b) conversion of the fluorides to oxides by reacting with water vapor, and (c) annealing followed by slow cooling in oxygen. The properties of the films depend on the amount of conversion of the fluorides by reaction with water. Films which show the presence of some unreacted barium fluoride have strong c-axis normal preferred orientation, with a sharp resistive transition. When all the barium fluoride is converted, the film is more randomly oriented and exhibits a broader transition to zero resistance.

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Direct writing of high-purity copper lines has been achieved by photothermal decomposition of copper formate films under ambient conditions using a focused argon ion laser (514 nm) beam on a scanning quartz or silicon substrate. The fast decomposition kinetics of the precursor allows use of writing speeds as high as 1 cm/s for deposition of micron-thick copper films. There is negligible oxidation of the copper after decomposition in the presence of air due to the rapid heating and cooling of the deposit during laser writing.

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...