Pulse stretcher and electronic device manufacturing method

An electronic device manufacturing method comprising:

• generating laser light using a gas laser device including a pulse stretcher;
• outputting the laser light to an exposure apparatus;
• and
• exposing a photosensitive substrate to the laser light in the exposure apparatus to manufacture an electronic device,
• the pulse stretcher including:
• a beam splitter configured to split pulse laser light into two beams of pulse laser light;
• a plurality of first concave mirrors arranged side by side in a predetermined direction;
• and
• a plurality of second concave mirrors arranged side by side in the predetermined direction as having the same number as the first concave mirrors and facing the first concave mirrors, respectively, wherein
• the plurality of first concave mirrors and the plurality of second concave mirrors are configured such that one beam of pulse laser light split by the beam splitter is alternately reflected 12 times prior to returning to the beam splitter,
• the plurality of first concave mirrors and the plurality of second concave mirrors are configured such that a number of optical paths of the beam of pulse laser light that overlap at each of a plurality of concentration point is only two,
• a number of the plurality of first concave mirrors is three, and a number of the plurality of second concave mirrors is also three, and
• the one beam of pulse laser light is reflected once at each of two reflection points in each of the three first concave mirrors and the three second concave mirrors, during one cycle in which the one beam of pulse laser light travels from the beam splitter back to the beam splitter via the plurality of first concave mirrors and the plurality of second concave mirrors.