1. Field of the Invention
The present invention relates to an apparatus for binding a carrier plate, used in a silicon wafer polishing apparatus, to a silicon wafer.
1. Prior Art
In the polishing of a monocrystal silicon wafer (hereafter referred to as just "wafer"), a fixed carrier plate is bonded to a plurality of wafer sheets: this carrier plate is then casted into the polishing apparatus and the polishing of the wafer is carried out.
In the prior art disclosed in First Publication Laid open number 63-245366, when a wafer is being bonded to the aforementioned carrier plate, wax has been previously applied to the inside of the wafer as a binding agent. A plurality of wafers are then placed on top of the carrier plate and after adhesion, the bonding was carried out using a pressure binding apparatus, as shown in FIG. 36.
In this apparatus on top of the main frame 80, inside the pressure lowering chamber 81, a press plate 83 is provided. To begin with a carrier plate 91 is placed on top of the pedestal 85, and resting directly above that is a press plate 83 for applying pressure to the wafer 90. At that time, while pressure is being lowered inside the pressure lowering chamber 81, which includes both the carrier plate 91 (on top of the pedestal) and the press plate 83, pressure is being applied to the wafer by the press plate 83. Following the deaeration of the binding surfaces of the wafer 90 and the carrier plate 91, the pressure lowering chamber 81 is returned to normal pressure and the bonding can then be carried out without the existence of air bubbles between the wafer and carrier plate.
However, the minimum line width of the integrated circuit (IC) used in the silicon monocrystal is 1 .mu.m. Additionally, when trying to form a circuit using optical lithography, due to the shallow depth of focus, a wafer possessing a satisfactory flatness is required. In order to obtain this desired wafer, improvements in both the polishing process as well as in the controlling of the carrier plate flatness are being carried out. There exist additional problems however, during the bonding, in the thickness and the thickness distribution of the wax layer: the wax layer thickness can be no greater than 1 .mu.m. Furthermore, there were also drawbacks in that refuse was entering into the space in between the carrier plate and the wafer as well as air bubbles were being left behind creating unwanted dimples, on the surface of the wafer following the polishing. Deterioration of the ability to flatten the carrier plate also was a point of concern.
In the bonding procedure of the prior art, when the aperture of the wafer becomes as big as 200 mm .phi., the uniform application of pressure becomes difficult. Additionally, when the wafer to which wax has been applied is facing downward, the occurrence of refuse cannot be ignored because a significant problem arises even when small particle refuse gets in between the wafer and carrier plate.