Abstract
The use of aluminium alloy films, and in particular Al-1%-Si, is common in many microelectronic interconnection schemes. Specular reflectivity and sheet resistance measurements are often used to characterise the deposited film. These and other properties, such as electromigration resistance, are dependent on the film's structure. An understanding of the relationship between the film structure and its properties is therefore important. Al-1%-Si films were deposited using dc magnetron sputtering onto (100) silicon substrates with or without thermal or deposited oxide layers. The film grain size and orientation were determined using scanning electron microscopy and X-ray diffraction measurements respectively. The orientation was quantified by the ratio of the X-ray diffraction intensities from the (111) and (200) planes. The structure of Al-1%-Si films depended strongly on film thickness using continuous mode deposition, and on substrate position using batch mode. For both modes of deposition the X-ray diffraction ratio was dependent on the substrate used. By careful choice of monitor substrate, and control of deposition conditions, the film structure could be successfully predicted and controlled. The specular reflectivity of Al-1%-Si films has been shown to depend on their roughness, optical properties and grain size, and the measurement wavelength. Of particular importance in determining the specular reflectivity is the substrate used as well as its position for batch mode deposition. The critical dimension size and automatic alignment accuracy obtained during the photolithographic patterning of the deposited film depended on its specular reflectivity. This shows that specular reflectivity control, especially for a batch deposition process, is important. Finally, room temperature sheet resistance has been shown to vary with the substrate used and substrate position during batch mode deposition.