Method for monitoring an ion implanter and ion implanter having a shadow jig for performing the same

A method for monitoring an ion implanter includes positioning a substrate behind an interceptor for intercepting a portion of an ion beam to be irradiated toward the substrate, irradiating a first ion beam toward the substrate to form a first shadow on the substrate, rotating the substrate about a central axis of the substrate, irradiating a second ion beam toward the substrate to form a second shadow on the substrate, and measuring a dosage of ions implanted into the substrate to monitor whether the rotation of the substrate has been normally performed. Preferably, a dosage of ions implanted into the substrate is calculated from a thermal wave value of the substrate and whether the rotation of the substrate has been normally performed is monitored by comparing the thermal wave value corresponding to the first shadow with a reference thermal wave value.