Abstract: A laser irradiation apparatus includes a laser beam generator that generates a first laser beam, a beam expander that expands the first laser beam and outputs the expanded first laser beam as a second laser beam, a beam splitter that splits the second laser beam into third laser beams and outputs the third laser beams, and a beam condenser that condenses the third laser beams and outputs condensed third laser beams. The beam expander includes a first lens having a first focal length and a second lens having a second focal length. The first lens is disposed between the laser beam generator and the second lens, the second lens is disposed between the first lens and the beam splitter, and the laser beam generator is spaced apart from the first lens by the first focal length.

Abstract: In a method of estimating a self refresh period of a semiconductor memory device according to an exemplary embodiment, a plurality of internal address signals are reset in response to a refresh reset signal. The plurality of internal address signals are sequentially changed synchronously with an oscillation signal. A refresh completion signal is generated based on the plurality of internal address signals. The self refresh period is detected based on the refresh reset signal and the refresh completion signal.

Abstract: In a method of estimating a self refresh period of a semiconductor memory device according to an exemplary embodiment, a plurality of internal address signals are reset in response to a refresh reset signal. The plurality of internal address signals are sequentially changed synchronously with an oscillation signal. A refresh completion signal is generated based on the plurality of internal address signals. The self refresh period is detected based on the refresh reset signal and the refresh completion signal.