High-efficiency line-forming optical systems and methods using a serrated spatial filter
High-efficiency line-forming optical systems and methods that employ a serrated aperture are disclosed. The line-forming optical system includes a laser source, a beam conditioning optical system, a first aperture device, and a relay optical system that includes a second aperture device having the serrated aperture. The serrated aperture is defined by opposing serrated blades configured to reduce intensity variations in a line image formed at an image plane as compared to using an aperture having straight-edged blades.
1. A method of performing defect annealing at a defect anneal temperature T D of a semiconductor wafer having a surface that includes a pattern, comprising:
forming from a CO 2 laser a light beam having a wavelength λ of 10.6 microns and a first intensity profile with a Gaussian distribution in at least a first direction;
passing at least 50% of the light beam in the first direction to form a first transmitted light;
focusing the first transmitted light at a Fourier plane to define a second intensity profile having a central peak and first side peaks immediately adjacent the central peak;
truncating the second intensity profile within each of the first side peaks with a serrated aperture disposed at the Fourier plane to define a second transmitted light that forms on the surface of the semiconductor wafer a first line image having between 1000 W and 3000 W of optical power and an intensity uniformity of within +/−5% over a first line length in the range from 5 mm to 100 mm; and
scanning the first line image over the surface of the semiconductor wafer to locally raise a temperature of the surface of the semiconductor wafer to the defect anneal temperature T D .
2. The method according to claim 1 , wherein the focusing of the first transmitted light is performed with a relay optical system having an optical component with a focal length f that defines the Fourier plane, wherein the serrated aperture has a width d2, and wherein the serrated aperture includes serrations having a length l in the range 0.1·(λ/(d2))·f≤l≤(λ/(d2))·f.
3. The method according to claim 2 , wherein the serrations have a pitch p within the range (0.9)·l≤p≤(1.1)·l.
4. The method according to claim 1 , wherein the defect anneal temperature T D is in the range 650° C.≤T D ≤1100° C.
5. The method according to claim 1 , further comprising performing spike annealing at a spike anneal temperature T A by:
forming a second line image at the surface of the semiconductor wafer using a second light beam having a second wavelength, wherein the second line image at least partially overlaps the first line image; and
scanning the second line image to locally raise the temperature of the surface of the semiconductor wafer from the defect anneal temperature T D to the spike anneal temperature T A .
6. The method according to claim 5 , wherein the spike anneal temperature T A is in the range 1100° C.≤T A ≤1350° C.
7. The method according to claim 5 , wherein the first line image has a first width and the second line image has a second width that is between 5% and 25% of the first width.
8. The method according to claim 7 , wherein the first width is in the range from 50 microns to 5 mm.
9. The method according to claim 5 , further comprising forming the second light beam using a laser diode light source and line-forming optics operably arranged relative thereto.
10. The method according to claim 5 , wherein the second wavelength is between 500 nm and 1000 nm.
11. The method according to claim 5 , wherein the second line image has a second line length in the range between 5 mm and 100 mm and an intensity uniformity of within +/−5%.
12. The method according to claim 5 , wherein the temperature of the surface of the semiconductor wafer has a variation from the spike anneal temperature T A due to pattern effects, and wherein the variation is no more than 60° C.