Laser machining device and laser machining method

Abstract

The controllability of modified spots is improved. A laser processing apparatus 100 comprises a first laser light source 101 for emitting a first pulsed laser light L 1 , a second laser light source 102 for emitting a second pulsed laser light L 2 , half-wave plates 104, 105 for respectively changing directions of polarization of the pulsed laser light L 1 , L 2 , polarization beam splitters 106, 107 for respectively polarization-separating the pulsed laser light L 1 , L 2 having changed the directions of polarization, and a condenser lens 112 for converging the polarization-separated pulsed laser light L 1 , L 2 at an object to be processed 1 . When the directions of polarization of the pulsed laser light L 1 , L 2 changed by the half-wave plates 104, 105 are varied by a light intensity controller 121 in the laser processing apparatus 100 , the ratios of the pulsed laser light L 1 , L 2 polarization-separated by the polarization beam splitters 106, 107 are altered, whereby the respective intensities of the pulsed laser light L 1 , L 2 are adjusted.

1 . A laser processing apparatus for converging a plurality of pulsed laser light at an object to be processed, so as to form a plurality of modified spots within the object along a line to cut and cause the plurality of modified spots to produce a modified region, the apparatus comprising:
 a first laser light source for emitting a first pulsed laser light having a first wavelength;   a second laser light source for emitting a second pulsed laser light having a second wavelength different from the first wavelength;   a first half-wave plate for changing a direction of polarization of the first pulsed laser light;   a second half-wave plate for changing a direction of polarization of the second pulsed laser light;   polarization separation portion for polarization-separating the first pulsed laser light having the direction of polarization changed by the first half-wave plate and the second pulsed laser light having the direction of polarization changed by the second half-wave plate;   a condenser lens for converging at the object the first and second pulsed laser light polarization-separated by the polarization separation portion; and   light intensity control portion for controlling an intensity of the first and second pulsed laser light by varying the directions of polarization of the first and second pulsed laser light changed by the first and second half-wave plates.   
     
     
         2 . A laser processing apparatus for converging a plurality of pulsed laser light at an object to be processed, so as to form a plurality of modified spots within the object along a line to cut and cause the plurality of modified spots to produce a modified region, the apparatus comprising:
 a first laser light source for emitting a first pulsed laser light having a first wavelength;   a nonlinear optical crystal for receiving the first pulsed laser light and emitting the first pulsed laser light and a second pulsed laser light having a second wavelength different from the first wavelength;   a first half-wave plate for changing a direction of polarization of the first pulsed laser light;   a second half-wave plate for changing a direction of polarization of the second pulsed laser light;   polarization separation portion for polarization-separating the first pulsed laser light having the direction of polarization changed by the first half-wave plate and the second pulsed laser light having the direction of polarization changed by the second half-wave plate;   a condenser lens for converging at the object the first and second pulsed laser light polarization-separated by the polarization separation portion; and   light intensity control portion for controlling an intensity of the first and second pulsed laser light by varying the directions of polarization of the first and second pulsed laser light changed by the first and second half-wave plates.   
     
     
         3 . A laser processing apparatus according to  claim 2 , further comprising pulse width control portion for controlling a pulse width of the first pulsed laser light emitted from the first laser light source;
 wherein the pulse width control portion changes the pulse width of the first pulsed laser light so as to lower a harmonic conversion efficiency of the nonlinear optical crystal such that the nonlinear optical crystal emits no second pulsed laser light.   
     
     
         4 . A laser processing apparatus according to  claim 1 , further comprising concentering portion for making the first and second pulsed laser light concentric with each other. 
     
     
         5 . A laser processing apparatus according to  claim 1 , wherein the polarization separation portion includes:
 a first polarization beam splitter for polarization-separating the first pulsed laser light having the direction of polarization changed by the first half-wave plate; and   a second polarization beam splitter for polarization-separating the second pulsed laser light having the direction of polarization changed by the second half-wave plate.   
     
     
         6 . A laser processing apparatus according to  claim 1 , wherein the light intensity control portion has a greater width of controllability for the first pulsed laser light than for the second pulsed laser light. 
     
     
         7 . A laser processing apparatus according to  claim 1 , wherein the light intensity control portion makes the intensity of the first pulsed laser light lower than an intensity threshold at which the modified spots are formed when the first pulsed laser light is converged alone at the object. 
     
     
         8 . A laser processing apparatus for converging a plurality of pulsed laser light at an object to be processed, so as to form a plurality of modified spots within the object along a line to cut and cause the plurality of modified spots to produce a modified region, the apparatus comprising:
 a first laser light source for emitting a first pulsed laser light having a first wavelength;   a second laser light source for emitting a second pulsed laser light having a second wavelength different from the first wavelength; and   a condenser lens for converging the first and second pulsed laser light at the object;   wherein the first pulsed laser light has an intensity made lower than an intensity threshold at which the modified spots are formed when the first pulsed laser light is converged alone at the object.   
     
     
         9 . A laser processing apparatus for converging a plurality of pulsed laser light at an object to be processed, so as to form a plurality of modified spots within the object along a line to cut and cause the plurality of modified spots to produce a modified region, the apparatus comprising:
 a first laser light source for emitting a first pulsed laser light having a first wavelength;   a nonlinear optical crystal for receiving the first pulsed laser light and emitting the first pulsed laser light and a second pulsed laser light having a second wavelength different from the first wavelength; and   a condenser lens for converging the first and second pulsed laser light at the object;   wherein the first pulsed laser light has an intensity made lower than an intensity threshold at which the modified spots are formed when the first pulsed laser light is converged alone at the object.   
     
     
         10 . A laser processing apparatus according to  claim 1 , wherein the first pulsed laser light has a wavelength longer than that of the second pulsed laser light. 
     
     
         11 . A laser processing method of converging a plurality of pulsed laser light at an object to be processed, so as to form a plurality of modified spots within the object along a line to cut and cause the plurality of modified spots to produce a modified region;
 the method comprising the step of converging a first pulsed laser light having a first wavelength and a second pulsed laser light having a second wavelength different from the first wavelength at the object through a condenser lens;   wherein the step makes the first pulsed laser light have an intensity lower than an intensity threshold at which the modified spots are formed when the first pulsed laser light is converged alone at the object.   
     
     
         12 . A laser processing method according to  claim 11 , wherein the first pulsed laser light has a wavelength longer than that of the second pulsed laser light. 
     
     
         13 . A laser processing apparatus according to  claim 2 , further comprising concentering portion for making the first and second pulsed laser light concentric with each other. 
     
     
         14 . A laser processing apparatus according to  claim 2 , wherein the polarization separation portion includes:
 a first polarization beam splitter for polarization-separating the first pulsed laser light having the direction of polarization changed by the first half-wave plate; and   a second polarization beam splitter for polarization-separating the second pulsed laser light having the direction of polarization changed by the second half-wave plate.   
     
     
         15 . A laser processing apparatus according to  claim 2 , wherein the light intensity control portion has a greater width of controllability for the first pulsed laser light than for the second pulsed laser light. 
     
     
         16 . A laser processing apparatus according to  claim 2 , wherein the light intensity control portion makes the intensity of the first pulsed laser light lower than an intensity threshold at which the modified spots are formed when the first pulsed laser light is converged alone at the object. 
     
     
         17 . A laser processing apparatus according to  claim 2 , wherein the first pulsed laser light has a wavelength longer than that of the second pulsed laser light. 
     
     
         18 . A laser processing apparatus according to  claim 8 , wherein the first pulsed laser light has a wavelength longer than that of the second pulsed laser light. 
     
     
         19 . A laser processing apparatus according to  claim 9 , wherein the first pulsed laser light has a wavelength longer than that of the second pulsed laser light.