Apparatus and methods for improving the intensity profile of a beam image used to process a substrate
Methods and apparatuses are provided for improving the intensity profile of a beam image used to process a semiconductor substrate. At least one photonic beam may be generated and manipulated to form an image having an intensity profile with an extended uniform region useful for thermally processing the surface of the substrate. The image may be scanned across the surface to heat at least a portion of the substrate surface to achieve a desired temperature within a predetermined dwell time. Such processing may achieve a high efficiency due to the large proportion of energy contained in the uniform portion of the beam.
1. A method for processing a semiconductor substrate, the method comprising the steps of:
(a) generating at least one photonic beam having a total beam energy and a nonuniform intensity profile;
(b) using the at least one photonic beam to form an image on a surface of the substrate, the image exhibiting a substantially uniform intensity profile over a useful portion thereof such that energy utilization by the useful portion of the image is at least 15% of the total beam energy; and
(c) scanning the image across the surface of the substrate to heat at least a portion of the substrate at and/or near the surface to achieve a desired temperature within a predetermined dwell time, D.
2. The method of claim 1 , wherein the nonuniform intensity profile of photonic beam is substantially Gaussian in shape.
3. The method of claim 2 , wherein the intensity profile of the photonic beam exhibits a profile consistent with a curve generated from a set of Hermite-Gaussian polynomials.
4. The method of claim 1 , wherein step (b) further comprises the step of:
(d) manipulating the at least one photonic beam to render at least a portion of its intensity profile more uniform.
5. The method of claim 4 , wherein step (b) is carried out such that the intensity profile of the image is rendered less Gaussian and more box-car in shape that an intensity profile that would be produced without manipulation of the at least one photonic beam in step (d).
6. The method of claim 1 , wherein step (a) generates a single photonic beam having a nonuniform intensity profile.
7. The method of claim 1 , wherein at least two photonic beams are combined to form a contiguous image.
8. The method of claim 7 , wherein the contiguous image has a substantially uniform intensity profile over the useful portion that is longer than provided by any one of the at least two beams.
9. The method of claim 1 , wherein the energy utilization by the useful portion of the image is at least about 25% of the total beam energy.
10. The method of claim 1 , wherein the energy utilization by the useful portion of the image is at least about 35% of the total beam energy.
11. The method of claim 1 , wherein the desired temperature is an annealing temperature sufficient to electrically activate dopant atoms implanted into a semiconductor material.
12. The method of claim 1 , wherein the desired temperature is at least about 1300° C.
13. The method of claim 1 , wherein the predetermined dwell time is no longer than about 1 millisecond.
14. The method of claim 1 , wherein the at least one beam is pulsed.
15. The method of claim 1 , wherein the at least one beam is continuous.
16. The method of claim 1 , wherein the substrate surface has a Brewster's angle for the at least one beam and the at least one beam is incident to the substrate surface at or near the Brewster's angle.
17. The method of claim 1 , wherein the at least one beam has a power of at least 250 W.
18. The method of claim 1 , wherein the at least one beam has a power of at least 1000 W.
19. The method of claim 1 , wherein the at least one beam has a power of at least 3500 W.
20. The method of claim 1 , wherein scanning the substrate across the image provides an exposure energy dose of at least about 25 J/cm 2 when D is about 1 millisecond.
21. The method of claim 1 , wherein the exposure energy dose is no more than about 60 J/cm 2 when D is about 1 millisecond.
22. The method of claim 1 , wherein the image has a peak intensity within the useful portion thereof and the substantially uniform intensity profile is entirely within a range of about 98% to 100% of the peak intensity.