Method of modifying a solid using laser light

Abstract

The invention relates to a method for creating a detachment zone ( 2 ) in a solid ( 1 ) in order to detach a solid portion ( 12 ), especially a solid layer ( 12 ), from the solid ( 1 ), said solid portion ( 12 ) that is to be detached being thinner than the solid from which the solid portion ( 12 ) has been removed. The method according to the invention preferably comprises at least the steps of: providing a solid ( 1 ) which is to be processed and which is made of a chemical compound; providing a LASER light source; and subjecting the solid ( 1 ) to LASER radiation from the LASER light source so that the laser beams penetrate into the solid ( 1 ) via a surface ( 5 ) of the solid portion ( 12 ) that is to be cut off; the LASER radiation controlling the temperature of a predefined portion of the solid ( 1 ) inside the solid ( 1 ) in a defined manner such that a detachment zone ( 2 ) or a plurality of partial detachment zones ( 25, 27, 28, 29 ) is formed; characterized in that the temperature produced by the laser beams in a predefined portion of the solid ( 1 ) is so high that the material forming the predefined portion is subject to modifications ( 9 ) in the form of a predetermined conversion of material.

The invention claimed is: 
     
         1 . A method, comprising:
 directing laser light from a laser light source into a solid surface of a solid, the laser light controlling a temperature of a predefined portion of the solid, the temperature controlled by the laser light subjecting a material of the solid which forms the predefined portion to modifications which convert the material; and   moving the solid in a translational manner with respect to the laser light source such that a number of the modifications per cm2 of the solid surface per translational movement, through which the laser light penetrates into the solid to generate the modifications, is below a predefined maximum number,   wherein a maximum number of the modifications per cm2 and per the translational movement is determined as a function of the material and of an energy density of the laser light,   wherein the number of generated modifications per cm 2  is different in at least two different zones of the solid,   wherein a first block of modifications is generated in a first zone and spaced apart from one another by less than 20 μm,   wherein a second block of modifications is generated in a second zone and spaced apart from one another by less than 20 μm,   wherein the first zone and the second zone are spaced apart from one another by a third zone,   wherein fewer modifications as compared to the first zone or the second zone per cm 2  are generated in the third zone by the laser light,   wherein the first zone is spaced apart from the second zone by more than 20 μm.   
     
     
         2 . The method of  claim 1 , wherein the material of the solid is selected from the group consisting of a third, fourth and/or fifth main group of the periodic table of elements and/or from the 12 th  subgroup of the periodic table of elements. 
     
     
         3 . The method of  claim 1 , further comprising:
 connecting the solid to a cooling device; and   operating the cooling device during application of the laser light to the solid.   
     
     
         4 . The method of  claim 3 , wherein the cooling device has at least one sensor device for capturing the temperature of the solid and, as a function of a predefined temperature course, effects a cool-down of the solid. 
     
     
         5 . The method of  claim 3 , further comprising:
 coupling the cooling device to a rotating means; and   rotating the cooling device with the solid arranged thereon by the rotating means during generation of the modifications.   
     
     
         6 . The method of  claim 1 , wherein the solid is subjected to consecutive rotations with respect to the laser light source, and wherein the modifications are generated with different patterns, in response to the consecutive rotations of the solid with respect to the laser light source. 
     
     
         7 . The method of  claim 1 , wherein the laser light source is a laser light scanner, and wherein generation of the modifications is a function of a laser scanning direction of the laser light scanner, a laser polarization direction and crystal orientation of the material of the solid. 
     
     
         8 . The method of  claim 1 , wherein a distance between centers of two modifications, which are generated consecutively in a modification generating direction or in a circumferential direction of the solid, is less than 10000 nm. 
     
     
         9 . The method of  claim 1 , wherein an outer limitation of the modifications, which are generated consecutively in a modification generating direction or in a circumferential direction of the solid, are spaced apart from one another by less than 10000 nm. 
     
     
         10 . The method of  claim 1 , wherein the number of generated modifications per cm 2  is different in at least two different zones of the solid, wherein a first block of modifications is generated in a first zone and spaced apart from one another by less than 20 μm, wherein a second block of modifications is generated in a second zone and spaced apart from one another by less than 20 μm, wherein the first zone and the second zone are spaced apart from one another by a third zone, wherein fewer modification as compared to the first zone or the second zone per cm 2  are generated in the third zone by the laser light, and wherein the first zone is spaced apart from the second zone by more than 20 μm. 
     
     
         11 . The method of claim  10   1 , further comprising:
 generating the modifications at least in the first block of modifications and in the second block of modifications in pulse intervals of between 0.01 μm and 10 μm.   
     
     
         12 . The method of claim  10   1 , further comprising:
 generating the modifications at least in the first block of modifications and in the second block of modifications in line spacings of between 0.01 μm and 20 μm.   
     
     
         13 . The method of claim  10   1 , further comprising:
 generating the modifications at least in the first block of modifications and in the second block of modifications at a pulse repetition frequency of between 16 kHz and 20 MHz.   
     
     
         14 . The method of  claim 1 , further comprising:
 providing an optics for guiding the laser light from the laser light source to the solid; and   adapting the optics as a function of a location at which a modification is generated, from
 which at least one change of a numerical aperture of the optics is effected, 
 wherein the numerical aperture at a location in an edge zone of the solid is smaller than at a different location of the solid, which is located closer to a center of the solid. 
   
     
     
         15 . A method, comprising:
 directing laser light from a laser light source into a solid surface of a solid, the laser light controlling a temperature of a predefined portion of the solid such that a detachment zone is formed in the solid, the temperature controlled by the laser light subjecting a material of the solid which forms the predefined portion to modifications which convert the material;   connecting the solid to a cooling device;   operating the cooling device during application of the laser light to the solid;    expanding a crack in the solid along the detachment zone to separate a solid portion from the solid along the crack; and   after the solid portion separates from the solid along the crack, again directing laser light from the laser light source into the solid to control the temperature of an additional predefined portion of the solid such that an additional detachment zone is formed, the temperature subjecting a material of the additional predefined portion of the solid to a predetermined material conversion.   
     
     
         16 . The method of  claim 15 , further comprising:
 connecting the solid to a cooling device; and   operating the cooling device during application of the laser light to the solid.   
     
     
         17 . The method of claim  16   15 , wherein the cooling device has at least one sensor device for capturing the temperature of the solid and, as a function of a predefined temperature course, effects a cool-down of the solid. 
     
     
         18 . The method of claim  16   15 , further comprising:
 coupling the cooling device to a rotating means; and   rotating the cooling device with the solid arranged thereon by the rotating means during generation of the modifications.   
     
     
         19 . A method, comprising:
 directing laser light from a laser light source into a solid surface of a solid, the laser light controlling a temperature of a predefined portion of the solid, the temperature controlled by the laser light subjecting a material of the solid which forms the predefined portion to modifications which convert the material;   connecting the solid to a cooling device;   operating the cooling device during application of the laser light to the solid; and   rotating or moving the solid in a translational manner with respect to the laser light source,   wherein a distance between centers of two modifications which are generated consecutively in a modification generating direction or in a circumferential direction of the solid is less than 10000 nm, and/or an outer limitation of the modifications which are generated consecutively in the modification generating direction or in the circumferential direction of the solid are spaced apart from one another by less than 10000 nm.   
     
     
         20 . The method of  claim 19 , wherein the material of the solid is selected from the group consisting of a third, fourth and/or fifth main group of the periodic table of elements and/or from the 12 th  subgroup of the periodic table of elements. 
     
     
         21 . The method of  claim 19 , further comprising:
 connecting the solid to a cooling device; and   operating the cooling device during application of the laser light to the solid.   
     
     
         22 . The method of claim  21   19 , wherein the cooling device has at least one sensor device for capturing the temperature of the solid and, as a function of a predefined temperature course, effects a cool-down of the solid. 
     
     
         23 . The method of claim  21   19 , further comprising:
 coupling the cooling device to a rotating means; and   rotating the cooling device with the solid arranged thereon by the rotating means during generation of the modifications.   
     
     
         24 . The method of  claim 19 , wherein the solid is subjected to consecutive rotations with respect to the laser light source, and wherein the modifications are generated with different patterns, in response to the consecutive rotations of the solid with respect to the laser light source. 
     
     
         25 . The method of  claim 19 , wherein the laser light source is a laser light scanner, and wherein generation of the modifications is a function of a laser scanning direction of the laser light scanner, a laser polarization direction and crystal orientation of the material of the solid. 
     
     
         26 . The method of  claim 19 , further comprising:
 providing an optics for guiding the laser light from the laser light source to the solid; and   adapting the optics as a function of a location at which a modification is generated, from
 which at least one change of a numerical aperture of the optics is effected, 
 wherein the numerical aperture at a location in an edge zone of the solid is smaller than at a different location of the solid, which is located closer to a center of the solid. 
   
     
     
       27. A method for separating a solid portion, in particular a wafer, from a solid, comprising:
 providing a solid to be processed, wherein the solid consists of silicon carbide;   exposing the solid to laser radiation from a laser light source, wherein
 the laser radiation penetrates the solid body via a surface of the solid portion to be separated; 
 the laser radiation controls the temperature of a predetermined portion of the solid inside the solid in a defined manner to form a detachment region or a plurality of partial detachment regions; and 
 the temperature produced in the predetermined portion of the solid by the laser radiation is so high that the material forming the predetermined portion is subject to modifications in the form of a predetermined material conversion or a phase conversion, the modifications creating a detachment region; and 
   separating the solid portion from the solid along the detachment region, the solid portion being thinner than the remaining solid reduced by the solid portion,   wherein the modifications are in the form of a predetermined material conversion comprising a decomposition of silicon carbide into its individual elements.    
     
     
       28. The method of  claim 27 , wherein separating the solid portion comprises introducing a force into the solid.  
     
     
       29. The method of  claim 27 , wherein the modifications each have a vertical extent of less than 30 μm.  
     
     
       30. The method of  claim 27 , wherein the modifications are in the form of a phase transformation, and the resulting phases are silicon and diamond-like carbon phases.  
     
     
       31. The method of  claim 27 , wherein the solid in the region of the modifications has a reduced stability compared to the solid outside the modifications.  
     
     
       32. The method of  claim 27 , wherein the temperature produced by the laser radiation is at least 2790° C.  
     
     
       33. The method of  claim 27 , wherein:
 in at least two different regions of the solid, the number of modifications generated per cm 2  is different;   a first block of modification lines is generated in a first region, wherein the individual modifications per line are generated at a distance of less than 10 μm from each other, the individual lines of the first block being generated less than 20 μm apart from one another, wherein a first partial detachment region is formed by the first block of modifications;   a second block of modification lines is generated in a second region, wherein the individual modifications per line are generated at a distance less than 10 μm apart from one another, the individual lines of the second block being generated less than 20 μm apart from one another, wherein a second partial detachment region is formed by the second block of modifications; and   the first region and the second region are spaced apart by a third region, wherein there are no modifications in the third region or there are fewer modifications per cm 2  generated by the laser radiation in the third region compared to the first or second region, and the first region is spaced apart from the second region by more than 20 μm.    
     
     
       34. The method of  claim 33 , wherein the modifications are generated by the laser radiation at least in the first block and in the second block at a pulse repetition frequency between 16 kHz and 20 MHZ.  
     
     
       35. The method of  claim 27 , wherein the laser light source is a laser light scanner, and wherein generation of the modifications is a function of a laser scanning direction of the laser light scanner, a laser polarization direction and crystal orientation of the material of the solid.  
     
     
       36. The method of  claim 27 , further comprising:
 providing an optics for guiding the laser light from the laser light source to the solid; and   adapting the optics as a function of a location at which a modification is generated, from which at least one change of a numerical aperture of the optics is effected, wherein the numerical aperture at a location in an edge zone of the solid is smaller than at a different location of the solid, which is located closer to a center of the solid.    
     
     
       37. The method of  claim 27 , wherein separating the solid portion comprises:
 arranging a receiving layer on the solid; and   applying a thermal application on the receiving layer to mechanically generate crack propagation stresses in the solid, wherein the crack propagation stresses cause a crack to propagate in the solid along the detachment region.    
     
     
       38. The method of  claim 37 , wherein the thermal application comprises cooling the receiving layer below a glass transition temperature of the material of the receiving layer.  
     
     
       39. The method of  claim 27 , wherein the solid is at least partially transparent for the laser radiation.  
     
     
       40. The method of  claim 27 , wherein the laser radiation is pulsed laser radiation with a wavelength of between 800 nm and 1200 nm.  
     
     
       41. A method, comprising:
 directing laser light from a laser light source into a solid surface of a solid, the laser light controlling a temperature of a predefined portion of the solid such that a detachment zone is formed in the solid, the temperature controlled by the laser light subjecting a material of the solid which forms the predefined portion to modifications which convert the material;   expanding a crack in the solid along the detachment zone to separate a solid portion from the solid along the crack; and   after the solid portion separates from the solid along the crack, again directing laser light from the laser light source into the solid to control the temperature of an additional predefined portion of the solid such that an additional detachment zone is formed, the temperature subjecting a material of the additional predefined portion of the solid to a predetermined material conversion,   wherein the modifications are in the form of a predetermined material conversion comprising a decomposition of silicon carbide into its individual elements.    
     
     
       42. The method of  claim 41 , wherein the modifications are in the form of a phase transformation, and the resulting phases are silicon and diamond-like carbon phases.  
     
     
       43. The method of  claim 41 , wherein the solid is at least partially transparent for the laser light.  
     
     
       44. The method of  claim 41 , wherein the laser light is pulsed laser radiation with a wavelength of between 800 nm and 1200 nm.  
     
     
       45. A method, comprising:
 directing laser light from a laser light source into a solid surface of a solid, the laser light controlling a temperature of a predefined portion of the solid, the temperature controlled by the laser light subjecting a material of the solid which forms the predefined portion to modifications which convert the material; and   rotating or moving the solid in a translational manner with respect to the laser light source,   wherein a distance between centers of two modifications which are generated consecutively in a modification generating direction or in a circumferential direction of the solid is less than 10000 nm, and/or an outer limitation of the modifications which are generated consecutively in the modification generating direction or in the circumferential direction of the solid are spaced apart from one another by less than 10000 nm,   wherein the modifications are in the form of a predetermined material conversion comprising a decomposition of silicon carbide into its individual elements.    
     
     
       46. The method of  claim 45 , wherein the modifications are in the form of a phase transformation, and the resulting phases are silicon and diamond-like carbon phases.  
     
     
       47. A method for separating a solid portion, in particular a wafer, from a solid, comprising:
 providing a solid to be processed, wherein a material of the solid is silicon carbide or gallium nitride;   exposing the solid to laser radiation from a laser light source, wherein
 the laser radiation penetrates the solid body via a surface of the solid portion to be separated; 
 the laser radiation controls the temperature of a predetermined portion of the solid inside the solid in a defined manner to form a detachment region or a plurality of partial detachment regions; and 
 the temperature produced in the predetermined portion of the solid by the laser radiation is so high that the material forming the predetermined portion is subject to modifications in the form of a predetermined material conversion or a phase conversion, the modifications creating a detachment region; and 
   separating the solid portion from the solid along the detachment region, the solid portion being thinner than the remaining solid reduced by the solid portion,   wherein the temperature produced by the laser radiation is at least 2790° C.    
     
     
       48. The method of  claim 47 , wherein the solid is at least partially transparent for the laser radiation.  
     
     
       49. The method of  claim 47 , wherein the laser radiation is pulsed laser radiation with a wavelength of between 800 nm and 1200 nm.