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1. (WO2019028064) FIBER LASER APPARATUS AND METHOD FOR PROCESSING WORKPIECE
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CLAIMS:

1. A method of processing an amorphous silicon (a-Si) film deposited on a glass panel, comprising:

(a) outputting a beam at a desired power P along a pre-scan path from at least one quasi-continuous wave (QCW) fiber laser which operates at a desired duty cycle of at most 100%;

(b) impinging the beam upon a scanner unit, thereby temporally chopping the beam into a plurality of sub-beams deviated off the pre-scan path within a desired angular range and at a desired angular velocity towards the a-Si film;

(c) optically shaping each deviated sub-beam to provide a spot of light on the a-Si film having spot length Ls and spot width Ws and spatial intensity beam profile in the scanning direction;

(d) sweeping the spot across the film in a scanning direction at a desired scanning velocity thereby forming a stripe on the film of a predetermined length and width Ws, wherein the scanning velocity and spatial beam profile generate such a controlled exposure duration at each location of the stripe and provide a desired fluence distribution in the scanning direction at each location within the stripe; and

(e) continuously displacing the glass panel in a cross-scanning direction, thereby sequentially forming a plurality of consecutive scanned stripes spaced from one another direction at a distance dy, which is at most equal to spot width WSl and together defining a column of polysilicon (p-Si) with a column width which corresponds to the length of the stripe Lsam.

2. The method of claim 1 , wherein the distance dy varies between 0.025 Ws to Ws and tends to increase within the range as a repetition rate of formation the consecutive scanned stripes increases to prevent p-Si grains from degradation and physical destruction of the a-Si film due to feedback overheating.

3. The method of claim 1 further comprising repeating the steps (a) through (d) to further process the column of the p-Si film if a previous sequence of these steps has not led to a desired grain size and orientation of p-Si.

4. The method of claim 4, wherein the desired scanning velocity Vscan and beam intensity profile are controlled so that each spot on the beam creates a completely melted triangularly-shaped film area with an apex which is spaced from the spot in a counter-scanning direction at a length L„ at least 10 times greater than the width tVs.

5. The method of any of the previous claims, wherein the glass panel is continuously displaced in the cross-scanning direction during the formation of the column of p-Si at a panel velocity at mm/sec, wherein the scanning velocity is maintained at km/sec.

6. The method of any of the previous claims, wherein the QCW fiber laser operates with the duty cycle less than 10094 so as to output the beam at a pulse repetition frequency from 80 MHz, which is sufficient to generate a thermal response of the a-Si identical to that caused by the beam from the QCW fiber laser operating at 100% duty cycle.

7. The method of any of the previous claims further comprising displacing the panel in the scanning direction at a distance dx at most equal to the column width Lscan, if the column width is smaller than that of the panel, and repeating steps (a) through (e), thereby forming at least one additional column of p-Si shifted off a previously formed adjacent column of p-Si by the distance dx, wherein the distance dy between adjacent stripes and distance dx between adjacent columns are selected such that each location of the processed film is irradiated in a range from 10 to SO times, and repeating displacing the panel in the scanning direction and forming the columns, thereby forming the p-Si film over the entire panel.

8. The method of claim 7, wherein displacing the panel in the scanning direction at thedistance dx of at most 0.5 mm precludes visible Mura.

9. The method of any of the previous claims, wherein the distances dy and dx are selected to be equal to one another or different from one another but the product dx*dy at each location is constant

10. The method of any of the previous claims, further comprising providing at least one additional spot of light, such that the desired spatial intensity profiles is achieved in one of scanning, cross-scanning, or scanning and cross-scanning directions.

11. The method of any of the previous claims, further comprising shaping the sub-beams incident on the film so as to have a Gaussian, super-Gaussian, or flat-top intensity profile in the cross-scanning direction, wherein the Super-Gaussian power factor is bigger than 2.

12. The method of any of the previous claims further comprising shaping of the sub-beam in each of the scanning and cross-scanning directions, thereby having the desired spatial intensity profiles in respective scanning and cross-scanning directions.

13. The method of any of the previous claims further comprising controlling polarization of the sub-beam incident on the film, thereby controlling alignment of the polycrystalline grains.

14. The method of claim 13 further comprising controlling polarization direction of the beam such that the polarization of the sub-beam incident on the film is set perpendicular to the spot beam scanning direction, thereby controlling alignment of the polycrystalline grains.

15. The method of any of the previous claims, wherein the beam is a single mode in a ultraviolet (UV) wavelength range.

16. The method of any of the previous claims, wherein the beam output is multimode.

17. The method of any of the previous claims, further comprising calibrating the scanner unit which includes an acousto-optical deflector (AOD), a plurality of rotating mirrors coupled together to define a polygon, or the AOD and the polygon.

18. The method of claim 17, further comprising collimating the beam upstream from the AOD, and gating the QCW fiber laser by turning the AOD off and on such that the incidence of the beam on free-space areas between adjacent mirrors of the polygon is prevented, or such that the scanned stripe has a predetermined length Lsca„ that is smaller than the maximum length of the stripe, with the maximum length being tens of centimeters.

:

19. The method of claim 18, further comprising adjusting a radio frequency (RF) at an input of the AOD for each mirror of the polygon, upon displacing the panel in the cross-scanning direction, thereby ensuring that the scanned stripes produced by respective mirrors are not shifted relative to one another.

20. The method of claim 18, further comprising:

measuring a focal depth of the sub-beam incident on the panel at a plurality of spaced-apart locations along the stripe length £,«,„;

measuring a signal at each of the locations;

comparing the measured signal with a reference value to generate the comparison result; and responsive to the comparison result, modulating an RF frequency at an input of the AOD so as to adjust a divergence of the sub-beam, thereby altering the focal depth.

21. The method of claim 18, further comprising generation of a plurality of RFs at the input of the AOD, and adjusting amplitudes of respective RFs to alter the divergence of sub-beams in the cross-scanning direction, thereby providing a desired intensity profile across the stripe, the intensity profile being selected from Gaussian, super-Gaussian or flat-top.

22. The method of any of the previous claims, further comprising:

measuring a focal depth of the sub-beam incident on the panel at a plurality of spaced-apart locations along the stripe length Lscan\

generating a signal at each of the locations;

comparing the generated signal with a reference value to generate the comparison result; and responsive to the comparison result, modulating an RF frequency at an input of a mechanical device or devices, thereby adjusting a divergence of the sub-beam to alter the focal depth thereof on the Si film, wherein the mechanical device includes a voice coil or piezo-electric actuator.

23. The method of any of the previous claims, further comprising mounting deformable optics between the scanner unit and the panel such that a focus plane tracks the panel surface, the deformable optics including one or more deformable mirrors, each of which have a continuously variable radius of curvature along a length of the sub-beam and along a length of each mirror of the polygon to compensate for an unevenness of the panel surface.24. An apparatus for processing a surface of a workpiece, comprising:

a QCW fiber laser operative to emit a laser beam at a constant power along a pre-scan path; a pre-scan beam conditioner configured to shape the laser beam such that an instantaneous spot beam has predetermined geometrical dimensions, intensity profile, and power;

a scanner positioned downstream from the pre-scan beam conditioner configured to receive the laser beam and deflect it into a plurality of sub-beams deflected off the pre-scan path, wherein the scanner operates at a predetermined angular velocity and angular range;

a post-scan optical assembly configured to provide the spot beam with predetermined geometrical dimensions, power, angular velocity and range, spot dimensions and intensity profile being selected such that when the instantaneous spot beam is dragged in a linear scan direction at a desired scan velocity, a desired exposure duration and fluence within a scanned stripe is achieved; and

a multi-axis stage operating to displace the workpiece at least in a cross-scan direction to form a plurality of uniform stripes that at least partially overlap one another to define a column, wherein the desired scan velocity and fluence provide a desired quality of the surface comparable to that of the surface that is processed by an excimer laser or a burst-mode fiber laser.

25. The apparatus of claim 24, wherein the QCW fiber laser operates with a duty cycle of at most 100%, whereby when operated at a duty cycle below 100%, the QCW fiber laser outputs a train of nanosecond pulses at a regular pulse repetition frequency from 80 to 200 MHz, which generates a thermal response of the treated surface identical to that caused by the beam from the QCW fiber laser operated with a 100% duty cycle.

26. The apparatus of any of the above apparatus claims, wherein the QCW fiber laser outputs the laser beam in a single mode or multiple transverse modes.

27. The apparatus of any of the above apparatus claims, wherein the pre-scan beam conditioner is configured with a polarizer assembly configured to lower the constant power to the predetermined power.

28. The apparatus of any of the above apparatus claims, further comprising a power controller located downstream from the pre-scan beam conditioner and coupled to the polarizer so as to adjust the constant power if it deviates from the predetermined power.

29. The apparatus of any of the above apparatus claims, wherein the pre-scan beam conditioner further includes a collimator configured to shape the laser beam so that it to becomes parallel upstream from the scanner which includes an acousto-optical deflector (AOD).

30. The apparatus of any of the above apparatus claims, further comprising multiple QCW fiber lasers outputting respective laser beams incident on the pre-scan beam conditioner, which is configured with a beam combiner configured to output the laser beam having the desired intensity profile in the scan direction, cross-scan direction, or scan and cross-scan directions, wherein the desired intensity profile is selected from the group consisting of a Gaussian, super-Gaussian, flat top profile, and combinations of these profiles.

31. The apparatus of any of the above apparatus claims wherein the scanner is configured as a polygon, AOD, or a combination of AOD and polygon where the polygon is located downstream from the AOD, and all operate to generate a km sec velocity at the workpiece.

32. The apparatus of any of the above apparatus claims, wherein the AOD is operative to gate the QCW fiber laser in order to prevent the incidence of the laser beam on interstices between adjacent facets of the polygon.

33. The apparatus of claims 31 or 32, wherein the AOD includes an RF generator configured to drive the AOD so as to control a divergence angle of the sub-beams deflected from the polygon.

34. The apparatus of claim 33, wherein the AOD is configured to alter the divergence angle so as to compensate for pointing errors of the facets of the polygon and unevenness of the surface to be treated.

35. The apparatus of claim 33, wherein the RF generator is operative to output a plurality of different frequencies into the AOD so as to control the spatial profile of the spot beam in the scan direction.

36. The apparatus of any of apparatus claims 24 through 31, wherein the post-scan optical assembly is configured with an objective lens selected from the group consisting of spherical, anamorphic, and a combination of spherical and anamorphic objective lenses.

37. The apparatus of claim 36, wherein the spherical objective lens includes a spherical F-theta lens and the anamorphic objective lens includes a spherical imaging lens with fixed

demagnification.

38. The apparatus of claim 36, wherein the anamorphic objective lens includes an anamorphic F-theta, cylinder, or anamorphic imaging lenses, the anamorphic imaging lens being configured with different magnification in scan and cross-scan directions.

39. The apparatus of claims 36 and 37, wherein the post-scan optical assembly, including the spherical imaging lens, a cylindrical imaging lens and an anamorphic imaging lens, further includes one or more cylindrical lenses located downstream from the objective lens, which functions to adjust the spot beam in the cross-scan direction.

40. The apparatus of any of the previous apparatus claims, wherein the multi-axis stage is configured to continuously move the workpiece in the cross-scan direction at a m/sec speed and over a distance dy not exceeding a full width of the stripe to form the column.

41. The apparatus of claim 40, wherein the multi-axis stage is operative to displace the workpiece in the scan direction at a distance dx at most equal to a width of the column, wherein the distance between adjacent stripes in the cross-scan direction and distance between adjacent columns are selected such that each location of the processed surface is irradiated in a range from 10 to 40 times.

42. The apparatus of claim 41, wherein the distances dy and dx are selected to be equal to one another or different from one another but the product dx*dy at each location is constant.

43. The apparatus of any of the above apparatus claims, further comprising deformable optics between the scanner and the workpiece configured to compensate for an unevenness of the surface.

44. The apparatus of any of the above apparatus claims, wherein the stripes each have a length varying from a few millimeters to a meter.

45. An apparatus for processing an amorphous silicon (a-Si) film deposited on a glass panel, comprising:

at least one quasi-continuous wave (QCW) fiber laser assembly operating at a desired duty cycle of at most 100% so as to output a beam at a desired power P along a path;

a scanner configured to deflect the beam into a plurality of sub-beams off the path within a desired angular range towards the a-Si film;

pre- and post-scan optical assemblies configured to optically shape the beam such that each deviated sub-beam deflected from the scanner and impacting the Si-film provides a spot of light having a length Ls in a scanning direction, a spot width W* and a spatial intensity beam profile in the scanning direction,

wherein the spot of light with the length Lt, the spot width W* and the intensity beam profile is swept across the film in the scanning direction at a desired scanning velocity Vscan, thereby forming a stripe on the film of a desired length and the width W, and the intensity beam profile, such that a desired exposure duration at each location of the stripe and a desired fluence distribution in the scanning direction at each location within the stripe is provided; and

a stage operating to continuously displace the glass panel in a cross-scanning direction such that a plurality of consecutive scanned stripes are spaced from one another at a distance dy, which is at most equal to the spot width Ws, and together define a column having a column width which corresponds to the length of the stripe Lsca„.