Intense laser irradiation using reflective optics
First Claim
1. An optical system for directing a beam of pulses of relatively intense ultraviolet radiation to a work piece surface comprising,(a) a source of ultraviolet radiation producing a beam of pulses of substantially monochromatic, directional , ultraviolet radiation of relatively high pulse fluence F0, on the order of 100 mJ/cm2 or greater,(b) a reflecting objective lens system having an optical input and an optical output, said optical output being immediately adjacent to said work piece surface, said optical input receiving said source radiation of pulses of fluence F0,(c) said reflective objective lens system having two or more reflecting surfaces that are highly reflective of said ultraviolet radiation and(d) at least one of said reflecting surfaces being formed of material that readily withstands said ultraviolet radiation pulses of fluence F0 incident thereon with negligible degradation of said surface reflectivity,(e) whereby said reflecting objective lens system focuses said beam pulses on said work piece surface to a fluence Ft, which is subtantially greater than F0.
2 Assignments
0 Petitions
Accused Products
Abstract
Intense far-ultraviolet laser radiation is applied to a workpiece in performance of processes in the fabrication of integrated circuits, including processes of ablation, deposition, impurity implantation and radiation induced chemical processes. Other processes where intense far-ultraviolet laser radiation is applied include hardening and annealing a workpiece by exposure to the radiation. Particular embodiments of the invention herein enables selective removal of a polymer film on a semiconductor substrate by ablative photodecomposition (APD) using intense far-ultraviolet, or shorter wave length, radiation from a pulsed laser requires focusing the laser radiation to provide sufficiently high fluence of laser light energy to ablate a selected area of the polymer to a useful depth in a reasonable time, sometimes referred to as the threshold of fluence of the laser pulses required to produce effective APD of the polymer. This is done with a reflective objective lens system between the laser and the polymer film that focuses the laser beam on a target area of the film surface to a high fluence image of the beam exceeding the threshold for APD. All optical surfaces of the objective lens system are reflective and so are not damaged by the intense radiation as refractive lenses can be. In a preferred embodiment, the reflective objective lens system includes two reflectors, one large concave reflector with an entrance aperture at the center facing the target and one small centrally-located convex reflector facing away from the target.
-
Citations
45 Claims
-
1. An optical system for directing a beam of pulses of relatively intense ultraviolet radiation to a work piece surface comprising,
(a) a source of ultraviolet radiation producing a beam of pulses of substantially monochromatic, directional , ultraviolet radiation of relatively high pulse fluence F0, on the order of 100 mJ/cm2 or greater, (b) a reflecting objective lens system having an optical input and an optical output, said optical output being immediately adjacent to said work piece surface, said optical input receiving said source radiation of pulses of fluence F0, (c) said reflective objective lens system having two or more reflecting surfaces that are highly reflective of said ultraviolet radiation and (d) at least one of said reflecting surfaces being formed of material that readily withstands said ultraviolet radiation pulses of fluence F0 incident thereon with negligible degradation of said surface reflectivity, (e) whereby said reflecting objective lens system focuses said beam pulses on said work piece surface to a fluence Ft, which is subtantially greater than F0.
-
21. In a system for illuminating the surface of a work piece with radiation of high flux density of magnitude substantially greater than the flux density of said radiation from the source thereof, means for directing and focusing said radiation from said source to said work piece surface comprising,
(a) a source of ultraviolet radiation producing a beam of pulses of substantially monochromatic, directional , ultraviolet radiation of relatively high pulse fluence F0, on the order of 100 mJ/cm2 or greater, (b) a reflecting objective lens system having an optical input and an optical output, said optical output being immediately adjacent to said work piece surface, said optical input receiving said source radiation of pulses of fluence F0 , (c) said reflecting objective lens system having two or more reflecting surfaces that are highly reflective of said ultraviolet radiation and (d) at least one of said reflecting surfaces being formed of material that readily withstands said ultraviolet radiation pulses of fluence F0 incident thereon with negligible degradation of said surface reflectivity, (e) whereby said reflecting object lens system focuses said beam pulses on said work piece surface to a fluence Ft, which is substantially greater than F0.
-
31. In a system for causing ablative photodecomposition at the surface of an organic material by pulsed ultraviolet laser radiation from a source of such laser radiation pulses of fluence F0, the improvement comprising,
(a) a source of said ultraviolet laser radiation producing a beam of pulses of substantially monochromatic, directional , ultraviolet radiation of pulse fluence F0, (b) a reflecting objective lens system having an optical input and an optical output, said optical output being immediately adjacent to said work piece surface, said optical input receiving said source radiation pulses of fluence F0, (c) said reflecting objective lens system having two or more reflecting surfaces that are highly reflective of said ultraviolet radiation and (d) at least one of said reflecting surfaces being formed of material that readily withstands said ultraviolet radiation of intensity I0 incident thereon with negligible degradation of said surface reflectivity, (e) whereby said reflecting objective lens system focuses said laser beam on said work piece surface to a pulse fluence Ft which is substantially greater than F0.
-
41. An optical system for directing a laser beam to a work piece surface comprising,,
(a) a source of laser radiation producing a beam of pulses of substantially monochromatic, directional radiation of relatively high pulse fluence F0, (b) a reflecting objective lens system immediately adjacent to the work piece surface, the optical axis of said reflecting ojbective lens system being essentially normal to the plane of said work piece surface, (c) said source including a laser producing a beam of substantially monochromatic, directional, pulsed radiation and (d) optical means defining an optical path for said laser beam between said laser and said objective lens system, (e) whereby said reflecting objective lens system focuses said laser beam on said work piece surface to a pulse fluence Ft which is substantially greater than F0. (f) a source of visible light, (g) means for directing said visible light to said objective lens system, (h) whereby said visible light illuminates said work piece surface and (i) visible light optical means, including an eyepiece for viewing said work piece surface through said objective lens system.
-
42. In a method of selectively removing material from a surface of an organic material by ablative photodecomposition of the material by a pulsed beam of ultraviolet laser radiation from a source of such laser radiation pulses of relatively high fluence F0, the improvement including the steps of:
-
(d) intercepting said ultraviolet laser radiation beam of pulses of fluence F0 by a first relatively small convex reflector that is adjacent to said surface, the optical axis of said first reflector being essentially normal to the plane of said surface and the reflective face thereof facing away from said surface and (e) intercepting said ultraviolet laser radiation beam that reflect from said first reflector by a second relatively large diameter concave reflector that is optically between said first reflector and said laser, the optical axis of said second reflector being essentially coincident with the optical axis of said first and the reflective face thereof facing toward said surface (f1) whereby said reflectors focus said laser radiation pulses on said surface to a pulse fluence Ft which is substantially greater than F0. - View Dependent Claims (43, 44, 45)
-
Specification