Method for producing recesses in a substrate

1. A method for producing a recess or a through-opening in a substrate using an optical system, a thickness of the substrate not exceeding 2 mm in a region of the recess or the through-opening to be produced, the method comprising:

applying pulsed laser radiation having a pulse duration to the substrate material of the substrate, which is transparent at least in part to the laser wavelength, wherein the laser radiation is focused using the optical system at an original focal depth and, by non-linear self-focusing within the pulse duration of an individual pulse, is also focused by the optical system at a focal depth different from the original focal depth, a length between the focal depths being greater than and extending across the thickness of the substrate in the region of the recess or the though-opening to be produced, whereby an intensity of the laser radiation modifies the substrate along a beam axis of the laser radiation in the region of the recess or the through-opening, but does not result in removal of the substrate material necessary to form the recess or the through-opening, wherein the laser radiation is deflected through a transmissive medium having a higher intensity-dependent refractive index than air, the transmissive medium being arranged between the substrate and a laser machining head emitting the laser radiation such that the distance between the focal depths between a maximum intensity and a minimum intensity of the individual laser pulse is greater than the predetermined longitudinal extent of the recess or the though-opening to be produced; and

anisotropically removing the substrate material in the modified region of the recess or the through-opening so as to produce the recess or the through-opening extending into the substrate in a direction of the thickness.

2. The method of claim 1 , wherein the focal depth is less than the original focal depth.

3. The method of claim 1 , wherein the substrate comprises glass, sapphire, and/or silicon, as a significant material proportion.

4. The method of claim 1 , wherein the anisotropically removing comprises etching in hydrofluoric acid.

5. The method of claim 1 , further comprising:

coating the substrate with an etch resist on at least one side prior to the laser treatment.

6. The method of claim 5 , further comprising:

removing the etch resist from the surface of the substrate after the anisotropically removing.

7. The method of claim 1 , further comprising:

coating the substrate is carried out in a planar manner with an etch resist on at least one surface prior to the laser treatment; and

removing, as a result of the action of the laser radiation, the etch resist in a dot-like action region, thereby producing the modification in the substrate on the at least one surface simultaneously.

8. The method of claim 1 , further comprising:

coating the substrate with a metal on at least one side.

9. The method of claim 8 , wherein the coating comprises providing the substrate, after the laser treatment, with a planar metal layer covering at least the recess or the through-opening to be produced such that the subsequent anisotropically removing produces the recess or the through opening sealed on one side by the planar metal layer.

10. The method of claim 1 , wherein a numeral aperture (NA) of the optical system is greater than 0.3.

11. The method of claim 1 , further comprising:

deflecting the laser radiation through a focusing subsystem of the optical system and through a material of the optical system having a higher intensity-dependent refractive index than air,

wherein the material transmits the laser wavelength of the laser radiation.

12. The method of claim 1 , wherein the transmissive medium comprises sapphire.

13. The method of claim 1 , wherein the original focal depth is disposed past a rear face of the substrate remote in the direction of the laser radiation along the beam axis.

14. The method of claim 1 , wherein the focal depths are separated by at least 30 μm in a direction of the beam axis of the laser radiation during the pulse duration of the individual pulse.

15. The method of claim 1 , further comprising, while the laser radiation is acting on the substrate:

moving the substrate relative to the laser radiation and/or a laser machining head emitting the laser radiation.

16. The method of claim 1 , wherein a plurality of recesses or through-holes are produced by the optical system being moved relative to the substrate at a uniform relative speed.

17. The method of claim 1 , wherein the laser radiation additionally removes a surface region.

18. The method of claim 1 , wherein the pulse duration of the laser radiation is less than 50 ps.

19. The method of claim 1 , wherein the original focal depth is positioned outside of the substrate, and wherein, during focal depth movement by the non-linear self-focusing, the intensity of the individual laser pulse increases from the minimum intensity at the original focal depth to the maximum intensity at the focal depth different from the original focal depth.

20. The method of claim 1 , wherein the anisotropically removing is performed so as to form the through-opening extending entirely across the thickness of the substrate.