Scribing sapphire substrates with a solid state UV laser

Abstract

A process and system scribe sapphire substrates, by performing the steps of mounting a sapphire substrate, carrying an array of integrated device die, on a stage such as a movable X-Y stage including a vacuum chuck; and directing UV pulses of laser energy directed at a surface of the sapphire substrate using a solid-state laser. The pulses of laser energy have a wavelength below about 560 nanometers, and preferably between about 150 in 560 nanometers. In addition, energy density, spot size, and pulse duration are established at levels sufficient to induce ablation of sapphire. Control of the system, such as by moving the stage with a stationary beam path for the pulses, causes the pulses to contact the sapphire substrate in a scribe pattern at a rate of motion causing overlap of successive pulses sufficient to cut scribe lines in the sapphire substrate.

1 . A method for manufacturing die from a sapphire substrate, comprising; 
 mounting the sapphire substrate on a stage, the sapphire substrate having a top surface and a bottom surface, the bottom surface facing the stage;    coupling laser energy having a wavelength below about 560 nanometers, directly into the top surface of the sapphire substrate by absorption sufficient to induce ablation of sapphire at the top surface; and    causing the laser energy to impact the sapphire substrate in a scribe pattern to cut scribe lines in the sapphire substrate.    
     
     
         2 . The method of  claim 1 , wherein said coupling includes directing pulses of laser energy at a surface of the sapphire substrate, the pulses having a peak power of less than about 10 GW/cm 2 , a spot size, and a repetition rate inducing non-linear absorption of the laser energy by the sapphire substrate.  
     
     
         3 . The method of  claim 1 , including using a solid state laser to generate said laser energy.  
     
     
         4 . The method of  claim 1 , wherein said wavelength is about 355 nanometers.  
     
     
         5 . The method of  claim 1 , including using a Nd-doped solid state laser having a primary laser wavelength to generate said laser energy, and said wavelength of said laser energy is a fourth harmonic wavelength of said primary laser wavelength.  
     
     
         6 . The method of  claim 1 , including separating die defined by the scribe pattern from the sapphire substrate.  
     
     
         7 . The method of  claim 1 , wherein said coupling includes causing delivering a sequence of overlapping pulses of laser energy to the sapphire substrate.  
     
     
         8 . The method of  claim 1 , wherein the wavelength is between about 150 and 560 nanometers.  
     
     
         9 . The method of  claim 1 , wherein said coupling includes causing delivering a sequence of overlapping pulses of laser energy to the sapphire substrate with a repetition rate between about 10 kHz and 50 kHz.  
     
     
         10 . The method of  claim 1 , wherein said coupling includes causing delivering a sequence of overlapping pulses of laser energy to the sapphire substrate with a pulse duration between about 10 and 30 nanoseconds, and a spot size between about 5 and 25 microns.  
     
     
         11 . The method of  claim 1 , including: 
 during said coupling, detecting edges of the sapphire substrate, and in response to detected edges, preventing said laser energy from being directed off of the substrate.    
     
     
         12 . The method of  claim 1 , including: 
 placing the substrate on an adhesive tape prior to said coupling; and preventing said laser energy from directly impacting the adhesive tape.    
     
     
         13 . The method of  claim 1 , wherein said coupling includes generating pulses of laser energy using a Q-switched Nd:YAG laser.  
     
     
         14 . The method of  claim 1 , wherein said coupling includes generating pulses of laser energy using a Q-switched Nd:YVO 4  laser.  
     
     
         15 . The method of  claim 1 , wherein said coupling includes generating pulses of laser energy using a diode pumped, Q-switched solid state laser.  
     
     
         16 . The method of  claim 1 , wherein the coupling includes providing laser energy with a spot size on the surface of the sapphire substrate between 5 and 15 microns.  
     
     
         17 . The method of  claim 1 , wherein the substrate has an active surface and a back side, and including placing the active surface of the substrate on an adhesive tape, and mounting the substrate on the stage to couple the laser energy into the back side of the substrate.  
     
     
         18 . The method of  claim 1 , wherein the substrate has an active surface and a back side, and including coupling the laser energy into the back side.  
     
     
         19 . The method of  claim 1 , including moving the substrate relative to the laser energy along a scribe line in the scribe pattern at a rate greater than about 8 mm/sec while coupling sufficient laser energy into the sapphire substrate to cut the scribe line in one pass.  
     
     
         20 . A method for manufacturing die from a sapphire substrate, comprising; 
 mounting the sapphire substrate on a stage, the sapphire substrate having a top surface and a bottom surface, the bottom surface facing the stage;    coupling pulses of laser energy having a wavelength below about 560 nanometers, directly into the top surface of the sapphire substrate by absorption sufficient to induce ablation of sapphire at the top surface, the pulses having a peak power of less than about 10 GW/cm 2 , a spot size less than about 25 microns, and a repetition rate greater than about 10 kHz, inducing non-linear absorption of the laser energy at or near the top surface of the sapphire substrate; and    causing the laser energy to impact the sapphire substrate in a scribe pattern to cut scribe lines in the sapphire substrate, including moving the substrate relative to the laser energy along a scribe line in the scribe pattern at a rate greater than about 8 mm/sec while coupling sufficient laser energy into the sapphire substrate to cut the scribe line in one pass.