Dual mode control of the rotational grinding process

The rotational grinding process enables the production of substrates to meet the submicron planarity specifications required for micro-fabrication of semiconductor integrated circuits. Improvements in process capability, with respect to both form and finish, have been generally realised by the development of machine tools and systems based on a principle of precise and predictable “position” control. An alternative principle for optimisation is demonstrated here comprising a dual mode control system where a “finishing mode” is based on local normal force control. Test results show significant relative improvements in levels of surface roughness and a reduction in the normal spatial variation.