| abstract |
Disclosed is a substrate processing method for forming a void along a prescribed line (12) in a silicon substrate (11). Said method includes: a first step in which elliptically polarized laser light (L), which has an ellipticity other than 1, is focused on a silicon substrate (11), thereby forming a plurality of modified spots (S) along a line (12) inside the silicon substrate (11), forming a modified region (7) including said modified spots (S); and a second step, after the first step, in which the silicon substrate (11) is anisotropically etched, said etching made to selectively progress along the modified region (7) to form a void in the silicon substrate (11). In the first step, the laser light (L) is focused on the silicon substrate (11) such that the direction in which the laser light (L) moves with respect to the silicon substrate (11) forms an angle of less than 45° with the polarization direction of the laser light (L), and the plurality of modified spots (S) are formed so as to line up, multiple spots wide, along the aforementioned line (12). |