Thin Film Analysis by Ion Beam Techniques

Wan Hong, Gi Dong Kim, Hyung Joo Woo, Han Woo Choi and Joon Kon Kim (KIGAM)

Since thin film processes are generally very complex and have to be precisely controlled in semiconductor industry, it is an important step to verify the elemental stoichiometry and the depth of the films. Electrolytic films also play important roles in many studies on development of battery and thin film capacitor. To understand the behavior of these thin films and improve the quality, analysis of thin film, not bulk, is essential. Many analytical methods such as AES(Auger Electron Spectrometry), SIMS (Secondary Ion Mass Spectroscopy), XPS (X-ray Photoelectron Spectrometry), RBS(Rutherford Backscattering Spectrometry) and ERD(Elastic Recoil Detection analysis) are applied to the characterization of thin films. RBS is a widely used method since it is an absolute non-destructive analysis method and has good analytical quality. ERD has excellent sensitivity and depth resolution in the quantitative analysis of light elements. In this work, a multi-purpose chamber for RBS and TOF(Time of Flight)-ERD is introduced and several analysis results on thin films are discussed. Ions were accelerated by a 1.7 MV tandem van de Graaff accelerator, which has two ion sources, alphatross ion source and SNICS (Source of Negative Ion by Cesium Sputtering). A multi-purpose target chamber was fabricated to perform both of RBS and TOF-ERD. A six-axis sample manipulator and a SSB (Silicon Surface Barrier) detector were set in the chamber. The chamber has a TOF arm for TOF-ERD at the forward direction of 30 degree with respect to beam direction. Two time detectors composed of MCPs(Micro Channel Plate) and a SSB detector were set in the TOF arm. Heavier elements than Si were analyzed by RBS with 2.4 MeV He ions, and lighter elements by TOF-ERD with 9.6 MeV Cl ions. An electrolytic film (1000 A) on a silicon wafer for thin film battery composed of lithium, vanadium and nickel was analyzed. Composition of vanadium, nickel and silicon were measured by RBS and the other elements were by ERD. Hydrogen and oxygen ratio, a very important parameter of the performance of the battery, could be determined. Another sample of electrolytic film composed of lithium and phosphor was also analyzed. In this sample, the nitrogen content was very high, and small carbon peak appeared. New dielectric films are being extensively studied in order to fabricate more integrated device since the dielectric layer with higher specific resistance is needed. Active layers in TFT and PDP displays are composed of many kinds of thin films, and thin film characterization is essential for the development of the device. A dielectric film, an insulator in semiconductor device, was studied. Ruthenium film has been developed as a transparent electrode for TFT display since it is a good conductor. However, it can be applied to semiconductor device as a barrier layer when it contains oxygen. Oxygen to ruthenium ratio is a very important parameter in this case. It was found that electrical property of the film is changed rapidly when oxygen content is higher than a critical value. Fluorine peak was found in the film, which was migrated during deposition process using fluorine as a carrier gas. Impurity control is also another important factor to fabricate the film with good electrical property.

제15회 탄템 가속기 및 그 주변기술연구회 (2002.6, Tsuruga, Japan)

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