Ion Beam Induced Chemical Vapor Deposition of Dielectric Materials
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ABSTRACT Direct writing by locally induced chemical vapor deposition has been applied to direct-write tailor-made microstructures of siliconoxide for modification and repair of microelectronic circuits. Focused ion beam (FIB) tools are used for locally confined deposition of dielectric material in the deep sub-jim range. State-of-the-art procedures typically provide insufficient dielectrics with high leakage currents and low breakdown voltage. The detailed investigation of the deposition mechanisms in this study proposes an approach to significantly improve dielectric material properties. Siloxane and oxygen as volatile precursors introduced in a vacuum chamber are used to deposit siliconoxide at ambient temperatures on various substrates such as Si, GaAs, or metals. The deposition process was initiated by a focused Ga'-beam. As elementary electronic test vehicles for a systematic electrical investigation ion beam induced depositions in of capacitor architectures are applied. The chemical composition of the layers is investigated by secondary ion mass spectroscopy (SIMS) and reveals effects of atomic mixing at the interfaces. The variation of process parameters such as ion energy and ion dose, scan time and delay time lead to a better understanding of the mechanisms. The composition of the precursor gas mixture is of significant influence on insulating properties. The results demonstrate that optimized FIBinduced deposition of dielectrics offers a new window for in-situ post-processing of integrated circuits.
INTRODUCTION The advancement and refinement of Direct-Write Technologies has triggered a steadily increasing interest of semiconductor fabrication and microelectronic circuit design in these techniques [1,2]. Improvement [3] of the reliability of the process and the properties of materials deposited by direct-writing have qualified direct-write technologies suitable for practical production line applications. Since direct-write technologies allow complex modifications on VLSI devices and ASICs [4,5] without using a lithographic transfer step the semiconductor fabrication has a fast and versatile tool in its hands. A majority of direct-write methods such as laser writing [6] or inkjet deposition provide a reliable technique for fabricating mesoscopic structures [7]. The continuous decrease of feature size in microelectronics generates a growing demand for methods that allow to directly write structures in the deep sub-jim range. Direct-writing of nanostructures is applied for fabrication of novel device prototypes or for designing advanced integrated circuits using a mix and match approach [7]. The availability of direct-write technologies for the sub-gm range, however, is 163 Mat. Res. Soc. Symp. Proc. Vol. 624 © 2000 Materials Research Society
limited. Electron beam induced deposition suffers from slow writing speed. AFM direct-writing appears to be a promising approach [8], but still lacks the necessary refinement and reliability of a fabrication tool. On the other hand focused ion beam (FIB) technology h
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