| abstract |
A new method of preparing an exceedingly flat substrate for forming semiconductor devices having an SOI structure is disclosed. n In this process at least a first wafer made of silicon single crystal is concavely warped beforehand. A second silicon single crystal wafer is bonded to the concavely warped side of the first wafer with an oxide film interposed between the first and the second wafers. Subsequently the wafers are subjected to polishing and/or etching so that the second wafer bonded is thinned into a thin film to prepare a substrate for forming semiconductor devices having a SOI structure. n At this time the polishing and/or etching cause the bonded wafers to be warped convexly to offset the concavity of the first wafer, resulting in realization of a precisely flat substrate for forming semiconductor devices having an SOI structure. n Further, at the time of determining the magnitude of the warp of the first wafer beforehand, an approximate linear equation is used which shows a relationship between the warps formed before and after the formation of the oxide film. |