Abstract
A lapping/polishing machine has been newly designed and constructed to produce precise flat surfaces efficiently. The machine can control the shape of a base plate by varying the pressure distribution on the work plates and the conditioning rings. It is also possible to control the shape of the base plate by changing the rotating speeds of the base plate and the work plates. Stable floating characteristics and vibration suppression to less than 1 μm are attained by using hydrodynamic bearings for the base plate bearings. Accurate and large loading are also attained by using parallel leaf springs. The base plate and work plate surfaces are lapped within a few microns by controlling the pressure distribution. The base plate always attains an isothermal state during silicon wafer polishing, because the upper and lower surface temperatures of the base plate rise simultaneously due to polishing and motor power heat. On the other hand, the work plates are deformed thermally. Therefore, two-layer discs with a larger coefficient of thermal expansion in the upper layer were used to reduce thermal deformation. As a result, it has been proved that highly accurate polishing may be attained efficiently by using the machine.
