Patent ID: 7678588

Claim:
A method for measuring optical critical dimension, adapted for measuring a to-be-measured pattern of a to-be-measured device, wherein the to-be-measured pattern comprises a polysilicon layer thereunder, the method comprising: obtaining a real curve corresponding to the to-be-measured device; selecting a different module in accordance to whether the polysilicon layer has been subjected to an ion implantation process; when the polysilicon layer has not been subjected to the ion implantation process, a first module is selected, and the first module is established with a first stacked layer, and the first stacked layer includes a polysilicon material layer but does include an amorphous silicon material layer, and when the polysilicon layer has been subjected to the ion implantation process, and a surface of the polysilicon layer is amorphorized into an amorphous silicon layer, then the module being selected is in accordance to whether a thermal process has been performed to sufficiently crystallize the amorphous silicon layer, when the polysilicon layer has not been subjected to the thermal process or the amorphous silicon layer has not crystallized completely into the polysilicon layer, a second module is selected, wherein the second module is established with a second stacked layer, and the stacked layer includes a polysilicon material layer and an amorphous silicon material layer above the polysilicon material layer, and when the polysilicon layer has been subjected to the thermal process to completely crystallize the amorphous silicon layer into the polysilicon layer, a third module is selected, wherein the third module is constructed with a third stacked layer, wherein the third stacked layer includes a polysilicon material layer, but does not include an amorphous silicon material layer; and performing a correlation process based on the selected module to generate a theoretical curve that correlates with the real curve to obtain a plurality of parameters corresponding to the theoretical curve.