Method of manufacturing substrate including micro hole

A method of manufacturing a substrate including a micro hole, comprising:

• setting a scanning rate (μm/sec) of pulsed laser light to 1×103 to 4000×103 μm/sec, the scanning rate being defined as a relative speed of a focal point of the laser light relative to a substrate when the focal point moves, the laser light having a pulse duration less than 10 picoseconds;
• adjusting a repetition rate (Hz) of the laser light so that a pulse pitch (μm) represented by the following Formula (1) is 0.08 to 0.8 μm;
• irradiating the substrate with the laser light, scanning the inside of the substrate with the focal point into which the laser light is collected while shifting the focal point at a constant scanning rate so as to overlap the focal points, each of which is one pulse, thereby forming a modified region having a lowered resistance to etching, at a region through which the focal point passed or at an adjacent region thereof;
• and
• forming a micro hole in the substrate by removing the modified region by an etching treatment.
• pulse pitch (μm)={the scanning rate (μm/sec) of the laser light}/{the repetition rate (Hz) of the laser light} Formula (1)