Studying electro‐physical material characteristics of vacuum‐deposited layers of aluminium (tantalum) when using aluminium sheet as a carrier for MCM, interconnections, vias and resistive groups

Abstract

Investigations of material parameters within the system Al, Al₂O₃, Ta, Ta₂O₅ and TaO_xN_1‐x 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 Al‐sheet as base isolation layer Al₂O₃ (50‐70μm). This process is followed by vacuum deposition of relatively thick layers of Al (2‐5μm). Each layer is then processed by lithographic methods followed by selective electro‐chemical 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 50μm. 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 TaO_xN_1‐x 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 high‐speed digital signals in the GHz range.

Citation

Philippov, P., Arnaudov, R., Yordanov, N., Ianev, V. and Gospodinova, M. (1998), "Studying electro‐physical material characteristics of vacuum‐deposited layers of aluminium (tantalum) when using aluminium sheet as a carrier for MCM, interconnections, vias and resistive groups", Microelectronics International, Vol. 15 No. 3, pp. 31-35. https://doi.org/10.1108/13565369810233131