“High Precision Film Thickness Trimming for TFH Industry”

Many applications in semiconductor technology are characterised by extreme requirements in terms of film thickness homogeneity. When manufacturing Thin Film Head (TFH) devices, it is necessary to adjust film thickness values of different materials with accuracy values in the nm-range. Standard processes, such as the film deposition techniques, or Chemical Mechanical Polishing (CMP) tend do not fulfil these homogeneity requirements sufficiently any more. Thus it is necessary to perform a local correction of the film thickness in a follow-up process.

The authors here introduce a new method of local film thickness trimming and its technical implementation. During the process, the wafer is moved in front of a focussed ion beam. The local milling rate is controlled upon the residence time of the ion beam at certain positions. A modulated velocity profile is calculated specifically for each wafer, in order to mill the material at the associated positions to the homogenous target film thickness.

The IonScan technology can be applied for any material desired, such as Al2O3, SiO2, Ta, NiFe, Co, Ru, DLC, etc. By means of adjusting the ion incidence angle there is also an opportunity to adjust certain selectivities between the materials. Beside of affecting film homogeneities it is also possible to reduce step height errors between different materials.