Laser irradiation method and laser irradiation system

A laser irradiation system comprising:

• a stage configured to move, in at least one scanning direction, an irradiation object in which an impurity source film containing at least an impurity element as a dopant is formed on a semiconductor substrate;
• a laser apparatus configured to generate a pulse laser beam having photon energy larger than the bandgap energy of the semiconductor substrate;
• an optical system through which the pulse laser beam is shaped to have a rectangular beam shape and incident on an irradiation region having a rectangular shape and set on the irradiation object;
• and
• a laser irradiation control unit configured to control the stage and the laser apparatus and perform processing of;
• reading, as a first irradiation condition for laser doping, first fluence that is fluence per pulse of the pulse laser beam with which the irradiation region is irradiated and a first irradiation pulse number that is the number of irradiation pulses the irradiation region is irradiated, the number being equal to or larger than two, the first fluence being equal to or larger than a threshold at or beyond which ablation occurs to the impurity source film when the irradiation object is irradiated with the pulse laser beam in the same number of pulses as the first irradiation pulse number and smaller than a threshold at or beyond which damage occurs to a surface of the semiconductor substrate;
• calculating a first scanning speed Vdx based on Expression (e) below when Bx represents a width of the irradiation region in a scanning direction, Nd represents the first irradiation pulse number, and f represents a repetition frequency of the pulse laser beam;
• and
• moving the irradiation object at the first scanning speed Vdx relative to the irradiation region while irradiating the irradiation region with the pulse laser beam at the repetition frequency f.
• Vdx=f·Bx/Nd (e)