Planarized aluminum submicron structure formation for interconnections of ULSI by laser lithography and electrochemical anodizing

Laser lithography with irradiation at a wavelength of 266 nm and electrochemical anodizing techniques were used to Term a submicron structure of aluminium lines planarized with anodic alumina films. The average size of the aluminium line width obtained in this research was about 500 nm and the minimum feature size of interconductor gaps, filled with dielectric anodic alumina, was 700 nm for a 660 nm thick aluminium layer. Aluminium lines appeared as slight trapezoids in cross-sections with some bent lateral surfaces. The surface of this structure is nearly plane. The small relief at the edges of the tantalum mask does not exceed 50 nm. The main technological processes steps involved in the technology developed are described. The results obtained show that using laser lithography and electrochemical anodizing techniques is a prospect to form planarized submicron pattern of ULSI aluminium interconnections. The nature of the anodic alumina film growth (nanosize cellular structure) opens the possibility of forming very small submicron structures down to nanometre size.