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External connections to thin film hybrid integrated circuits (HICs) by solder bonding have several advantages over those bonded by solid phase or thermocompression bonding. This paper reviews these advantages and discusses the parameters necessary for high strength, reliable solder joints to thin films. Dissolution of the soluble thin film@) into solder limits the solder reflow times. Recent work has shown that dissolution rates of thin films in solder depend primarily on the degree of thin film heat treatment prior to soldering, substrate surface texture, and the method of thin film deposition. Auger in-depth profiling data show that alloy formation and internal oxidation reduces film dissolution during solder reflow. Metallographic sectioning and chemical analysis are used to identify weak solder bond interfaces which result from intermetallic formation. Tin from the solder diffuses rapidly and reacts with soluble metals such as gold, palladium and copper to form brittle intermetallics such as AuSn4, PdSn4 and Cu6Sn,. Intermetallic formation between the solder and the thin film systems of interest can affect joint strength and reliability.

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The Cameca Ion Microanalyzer has been used to analyze the surface and bulk of a number of sputtered tantalum thin films. This technique of chemical analysis has unique analytical capabilities which are based on the emission and subsequent mass analysis of characteristic secondary ions ejected by high energy (several K e V ) ion bombardment. The results obtained on sputtered tantalum films, reactively sputtered (argon.oxygen, argonsnitrogen mixtures) tantalum films, and oxidized tantalum films are presented to demonstrate these unique analytical capabilities. Quantitative analysis by this method is shown to depend on the accurate and reproducible measurement of characteristic parameters s u c h a s t h e secondary ion current of the impurity ( i a i ) and the secondary ionization yield of the impurity relative to t h e matrix (Krel). The magnitude of Krel is best determined by the use of standards.This paper describes and critically evaluates a relatively new analytical technique, Secondary Ion Emission, for localized surface and bulk thin film analysis and to present a method of performing quantitative analysis by the use of standards. This technique of chemical analysis is based on the emission and subsequent mass analysis of characteristic secondary ions which are ejected from a sample due to bombardment by a high energy (several KeV) ion beam. All elements and their isotopes can be detected by mass spectroscopy with a sensitivity in the ppm range, and for some elements in the ppb range. With this technique, ion images providing spatial elemental distribution of the sample can also be obtained with approximately -1 pm resolution. In-depth analysis can also, be performed. The in-depth analysis is accomplished by a controlled and gradual sputtering of the sample, and in-depth resolutions better than 100 A have been reported ( I ) .Results have been obtained for T a films sputtered in argon, argon-nitrogen, argon-oxygen mixtures, and for thermally oxidized films which demonstrate the unique capabilities of the technique for both bulk and surface analysis. Equations for quantitative analysis have been developed. These equations require the use of standards, are empirical, and are not based on a model of secondary ion emission. In addition, the capabilities and limitations of secondary ion emission for surface analysis are presented along with complementary results on surface impurities detected on similar tantalum films by Auger Electron Spectroscopy.

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