K. Yamanishi

Formation of superconducting ErBaCuO thin films by ionized cluster beam apparatus

Abstract The crystallization and oxidation processes used to make ceramic superconducting films will have to be performed at temperatures lower than those currently used before superconducting devices can be produced economically for highly anticipated commercial applications. The ICB technique using three ionized cluster beams and ozone to form ErBaCuO high-temperature superconducting thin films at a temperature below 650 ° C was studied. The as-grown film formed at a substrate temperature of 650 ° C and at an acceleration voltage of 300 V showed a T c of 90 K and J c of 1.2 × 10 6 A/cm 2 at 77 K at a width of 17 μm and length of 20 mm. It is considered that nonthermal energy contributed by the ICB and ozone is important for film formation at this temperature. Furthermore, the as-grown film formed at a substrate temperature of 550 °C showed a stronger c -axis orientation at an acceleration voltage of 1 kV compared with the case of 300 V. This result suggests that kinetic energy can be substituted for thermal energy and is more important for forming high quality thin films at temperatures as low as 550°C.

Development of ionized cluster beam source for practical use

Low‐energy ion bombardment during film growth can significantly modify film properties. The practical advantages of using an ionized cluster beam (ICB) include reduced damages and high deposition rates at low temperature. The design and the characteristics of the ICB source are described. The ionized cluster trajectories and the potential profiles were numerically calculated in order to optimize the design. The ionization chamber has restrictive electrodes to enhance the ionization probability in the low cluster density region near the anode. With these electrodes, the source provides uniform ion current densities up to 30 μA/cm2 at voltages ranging from 200 to 8000 V over a 127 mm diam substrate at a distance of 300 mm from the source. The ICB source can operate over a wide temperature range up to 2000 °C. Deposition rates up to 120 nm/min are obtained for Ti, Si, and Cu. The source has successfully operated for more than 100 h in several industrial applications.

Synthesis of superconducting YBaCuO thin films by ionized cluster beam codeposition

Abstract The technique of ionized cluster beam (ICB) deposition is very effective in synthesizing high-temperature superconducting thin films, because of its kinetic energy and electric charges. An ICB codeposition with multiple sources was used to control the composition ratio and the crystal structure of the films by controlling the intensity, the kinetic energy and the ionization ratio of each cluster beam independently. Superconducting YBaCuO films were obtained by a combined method of codeposition of Y, Ba and Cu, and postannealing in an oxygen atmosphere. The films were deposited in a vacuum chamber with a pressure below 1.3 × 10−3 Pa without intentional heating of substrates. The characteristics of the films such as the transition temperature to zero-resistance state (Tc,zero) depend mainly on the acceleration voltage which determines the kinetic energy of the ionized clusters. Films with Tc,zero above 77 K were synthesized with an acceleration voltage of 0.5 kV. Superconducting YBaCuO films with Tc,zero of 70 K were also synthesized by codeposition in oxygen gas without postannealing.

Development of an ionized cluster beam system for large-area deposition

Abstract The ionized cluster beam (ICB) method [1], which can transport large mass with low ion energy, is very effective to form tailored thin-film materials for application in advanced technical devices. A multinozzle-type ICB system has been developed for large-area film deposition, which is very important for extending its application from research and development to industrial use. In this apparatus, uniformity of ion current density on a substrate of 250 mm diameter and homogeneity of large-area thin film were obtained. A multisource-type ICB system in which four ion sources can be mounted has also been developed, to study compound thin films such as TiSi 2 , PbTiO 3 , superconductor YBa 2 Cu 3 O 7− x , etc. The characteristics of gold (Au) film on copper (Cu), the forma of aluminum (Al) film on silicon and the crystallinity of FeO x films which were made by this ICB system, are described.

Applications of ionized cluster beam to anti-reflection coating of transmission windows

Abstract High transmission films with high adhesive strength have been developed by using the ionized cluster beam (ICB) method. It was demonstrated that the acceleration voltage plays a very important role in controlling the optical quality of films. The transmission windows obtained are as follows. (1) The germanium (Ge) window coated with a zinc sulfide (ZnS) film obtained at 3 kV acceleration voltage had a transmittance of 96% at 10 μm wavelength and the adhesive strength of the film obtained was over 430 kg cm −2 , which endured even after thermal treatment at 460°C. (2) The zinc sulfide (ZnS) window coated with lead fluoride (PbF 2 ) film obtained by controlling the acceleration voltage within the range from 0.5 kV to zero had a transmittance of 95% at 10 μm wavelength and the adhesive strength of the film was 240 kg cm −2 .

Industrial applications of ICB deposition for the fabrication of electronic devices

Abstract Technologies for forming functional layers are required to increase functions and to achieve miniaturization of devices. Ionized cluster beam (ICB) deposition is suitable for these needs and has been used to form thin films with unique characteristics compared to films formed by other techniques. Here, the ICB technique for forming a TiN Ti layer at the bottom of contact holes in DRAMs is discussed. A simple deposition model predicted that the narrow angular distribution of evaporated species and deposition at low vacuum pressure are essential conditions for sufficient coverage of the contacts. The bottom coverage of TiN Ti films has been improved by over 10 times by using the ICB technique in comparison with films produced by conventional sputtering methods. Other applications of ICB to high reflective optical mirrors with an atomically flat surface and high-temperature superconductors with high critical current density within a wide range are also discussed.

Solution of in-line inspection problem for grainy metal layers by "saturation effect" of grayscale

We demonstrate a solution, which enhances the practical sensitivity of in-line pattern matching inspectors for grainy metal layers by reducing the nuisance counts without additional investment. We confirmed that most nuisance defects are caused by the grain boundaries on the Hot-AlCu wirings. Then we proposed a new solution called saturation effect to decrease the defect signals from the grain boundaries. The experimental results prove that the saturation effect with illumination brightness optimization successfully cancels the defect signal from grain boundaries. As a result, we can efficiently detect real defects without detecting the grain boundaries. The observed practical sensitivity limit is enhanced from 0.8 /spl mu/m to 0.4 /spl mu/m. We believe this solution may accelerate the yield enhancement counter measurements based on in-line inspection results.

Capture rate enhancement method of 0.1 /spl mu/m-level defects by pattern matching inspectors

In this paper, a method of enhancing the capture rate of 0.1 /spl mu/m-level defects by pattern matching inspectors is studied from the viewpoint of image variances. The inspection sensitivities are experimentally evaluated by using the detection rate of the defects on an actual device and also on the TEG. The image noise and the defect signal of the captured CCD images of the same defect are quantitatively analyzed. The observed image noise and the defect signal obey a normal distribution. The capture rate calculated by our model, based on a normal distribution, almost agrees with the experimental data. In addition, as an example of capture rate enhancing, a unique TEG called TWICE is demonstrated. By our method, defect inspection engineers can obtain the key factors for enhancing the capture rate of 0.1 pm-level defects on both actual devices and TEGs.

A defect-situation forecasting technology to optimize future DRAM-redundancy design

A method of forecasting defect situations in future DRAMs manufactured in the same or similar lines is demonstrated The estimated word-line defect situation of a 0.35 micron DRAM almost agreed with the actual data. By calculation with actual 0.5 micron DRAM word-line defect data, we approximated D(x), the function of particle-existing-probability density on a particle diameter x, as a proportion of 1/x/sup 1.5/. The word-line defect counts of a 0.35 micron DRAM were estimated by the product of the approximated D(x) and P/sub k/(x), the possibility function that k-lines of short or open circuits will be made.

Investigation of laser and ion beam applications for industrial use

Technologies for processing materials precisely and for forming functional layers within a defined region without harming substrates are required to achieve further miniaturization of devices and to augment functions. Though processes utilizing laser and ion beam energy are suitable for meeting these needs, a number of problems must be solved in order to effectively apply these technologies in industry. A CO 2 laser system featuring a short pulse duration and high peak power has been developed to permit high speed perforation of electric circuit boards. Holes can be formed with only a thin thermally damaged wall layer which can readily be removed by light etching. A high efficiency excimer laser system was developed for making many small holes without damaging plastic films. An ICB (Ionized Cluster Beam) technique for a wafer process of LSI was also developed. This technique allows formation of barrier films at the bottom of contact holes with a high aspect ratio. Finally methods for depositing ceramic film at high rates utilizing a CO 2 laser and dynamic mixing by ion beam were studied to permit production of mechanical parts with a hard surface at low cost.