US Patent 7727867 Method for manufacturing SIMOX wafer

A MLD-SIMOX wafer is obtained by forming a first ion-implanted layer in a silicon wafer; forming a second ion-implanted layer that is in an amorphous state; and subjecting the wafer to a high-temperature heat treatment to maintain the wafer in an atmosphere containing oxygen at a temperature that is not lower than 1300° C. but lower than a silicon melting point to change the first and the second ion-implanted layers into a BOX layer, wherein the dose amount for the first ion-implanted layer is 1.25 to 1.5×1017 atoms/cm2, the dose amount for the second ion-implanted layer is 1.0×1014 to 1×1016 atoms/cm2, the wafer is preheated to a temperature of 50° C. to 200° C. before forming the second ion-implanted layer, and the second ion-implanted layer is formed in a state where it is continuously heated to a preheating temperature.