Studying electrophysical material characteristics of vacuumdeposited layers of aluminium tantalum when using aluminium sheet as a carrier for MCM, interconnections, vias and resistive groups

• Published in: Microelectronics international 1998-12, Vol.15 (3), p.31-35
• Main Authors: Philippov, Ph, Arnaudov, R., Yordanov, N., Ianev, V., Gospodinova, M.
• Format: Article
• Language: English
• Subjects: Aluminium; Interconnection; Multichip module; Vacuum deposition; Vias
• ISSN: 1356-5362
• DOI: 10.1108/13565369810233131

Investigations of material parameters within the system Al, Al2O3, Ta, Ta2O5 and TaOxN1x are presented. This combination is characteristic when using Al sheet for production of substrates including electronic interconnections, vias and resistive groups. They can serve for MCMs due to the specific features of Al. The technological process includes first electrochemical oxidation of Alsheet as base isolation layer Al2O3 5070m. This process is followed by vacuum deposition of relatively thick layers of Al 25m. Each layer is then processed by lithographic methods followed by selective electrochemical oxidation as a help process for structuring. The development of this combined structuring method allows the simultaneous achievement of interconnections Al and isolation Al2O3 levels with least size up to 50m. The importance of the method consists of a vertical combination of several conductive layers of Al structured as described above, burying the interconnections in the insulating Al2O3 films. All necessary combinations and configurations of different kinds of microstrip lines are possible. The dielectric characteristics of Al2O3, achieved through the above mentioned method, can be changed in accordance with the parameters of the technological steps and filling of the porous structure. Thus some interesting high frequency features of microstrips are obtained. Extra advantage is the ability of combination of conductive Al layers with other types of such layers as tantalum Ta. With Ta can be achieved other permittivity constants of the insulation layers and in combination with TaOxN1x intermediate planes of resistive groups are developed. The measurement of the stripline parameters is done by microwave technics, because the desired application of the substrates is for highspeed digital signals in the GHz range.