High-efficiency line-forming optical systems and methods using a serrated spatial filter
View Patent ↗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 system for performing defect annealing of a semiconductor wafer having a surface with a pattern, comprising:
a CO 2 laser source that emits an initial light beam having a wavelength λ of 10.6 microns;
a beam-conditioning optical system that receives the initial light beam and forms therefrom a conditioned light beam having a first intensity profile with a Gaussian distribution in at least a first direction;
a first aperture device operably disposed at an object plane and that defines a first slit aperture that truncates the first intensity profile in the first direction to define first transmitted light that constitutes at least 50% of the conditioned light beam;
a relay optical system that defines the object plane and that also defines an intermediate Fourier plane at which is operably disposed a second aperture device, the relay optical system defining at the Fourier plane a second intensity profile having a central peak and first side peaks immediately adjacent the central peak, wherein the second aperture device is configured with serrated blades that truncate the second intensity profile in the first direction and within each of the first side peaks to define second transmitted light;
wherein the relay optical system forms from the second transmitted light a first line image at the wafer surface, wherein the first line image includes between 1000 W and 3000 W of optical power, has a first length in the range from 5 mm to 100 mm, and has an intensity uniformity of within +/−5%;
a chuck that operably supports the wafer; and
a moveable wafer stage that operably supports the chuck and that is configured to move the chuck and the wafer supported thereon so that the first line image scans over the wafer surface to locally raise a temperature of the wafer surface to a defect anneal temperature T D .
2. The system according to claim 1 , wherein the relay optical system has a first optical component with a focal length f that defines the Fourier plane, wherein the blades of the second aperture device are separated by a width d 2 , and wherein the serrated blades each includes serrations having a length l in the range 0.1·(λ/(d 2 ))·f≤1≤(λ/(d 2 ))·f.
3. The system according to claim 2 , wherein the serrations have a pitch p within the range (0.9)·1≤p≤(1.1)·1.
4. The system according to claim 1 , wherein the defect anneal temperature T D is in the range from 650° C. to 1100° C.
5. The system according to claim 1 , wherein the chuck is heated so that it can pre-heat the wafer.
6. The system according to claim 1 , further including a diode-based line-forming optical system that generates a visible light beam that forms at the wafer surface a second line image that at least partially overlaps and scans with the first line image to locally raise the temperature of the wafer surface from the defect annealing temperature T D to a spike anneal temperature T A , and wherein the second line image has an intensity variation of within +/−5%.
7. The system according to claim 6 , wherein the spike anneal temperature is in the range from 1150° C. to 1350° C.
8. The system according to claim 6 , wherein the first and second line images have respective first and second widths, and wherein the second width is in the range from 5% to 25% of the first width.
9. The system of claim 6 , wherein the diode-based line-forming optical system includes a laser diode light source and line-forming optics arranged relative thereto.
10. The system according to claim 1 , wherein each side peak is defined by a maximum value MX and first and second minimum values m 1 and m 2 , and wherein the second aperture device is configured to truncate the second intensity profile between the maximum value MX and the second minimum value m 2 in each first side peak.
11. The system according to claim 1 , wherein the relay optical system has substantially 1× magnification in the first direction.
12. The system according to claim 11 , wherein the relay optical system is a cylindrical optical system having optical power only in the first direction.
13. The system according to claim 1 , wherein the optical relay system consists of reflective optical components only.
14. The system according to claim 1 , wherein the first aperture device comprises a pair of blades operably disposed in the object plane.
15. The system of claim 1 , wherein the second aperture device comprises a pair of blades operably disposed in the intermediate Fourier plane.
16. A line-forming optical system for forming a line image at an image plane, comprising:
a laser source that emits an initial light beam having a wavelength λ;
a beam-conditioning optical system that receives the initial light beam and forms therefrom a conditioned light beam having a first intensity profile with a Gaussian distribution in at least a first direction;
a slit aperture that truncates the first intensity profile in the first direction to define first transmitted light that constitutes at least 50% of the conditioned light beam;
a relay optical system that includes first and second optical components and that defines an object plane, an image plane and a Fourier plane between the object and image planes, wherein the first optical component has a focal length f and forms at the Fourier plane a second intensity profile having a central peak and first side peaks immediately adjacent the central peak;
opposing serrated blades arranged at the Fourier plane and configured to truncate the second intensity profile in the first direction and within each of the first side peaks to define second transmitted light; and
wherein the second optical component forms from the second transmitted light the line image at the image plane.
17. The line-forming optical system according to claim 16 , wherein the laser source includes a CO 2 laser and wherein the initial light beam has a wavelength of 10.6 microns.
18. The line-forming optical system according to claim 16 , wherein the opposing serrated blades are separated by a width d 2 , and wherein the serrated blades each includes serrations having a length l in the range 0.1·(λ/(d 2 ))·f≤1≤(λ/(d 2 ))·f.
19. The line-forming optical system according to claim 18 , wherein the serrations have a pitch p within the range (0.9)·1≤p≤(1.1)·1.
20. The line-forming optical system according to claim 16 , wherein the line image has between 1000 W and 3000 W of optical power, has a length in the range from 5 mm to 100 mm, and has an intensity uniformity of within +/−5%.