Semiconductor device separation using a patterned laser projection

Abstract

A method for separating a semiconductor wafer into several thousand devices or die by laser ablation. Semiconductor wafers are initially pre-processed to create multiple devices, such as blue LEDs, on the wafers. The wafers are then mounted with tape coated with a generally high level adhesive. The mounted wafer is then placed on a vacuum chuck (which is itself positioned on a computer controlled positioning table) to hold it in place during the cutting process. The cutting surface is then covered with a protective layer to prevent contamination from the effluent resulting from the actual cutting process. A laser beam is generated and passed through optical elements and masks to create a pattern, such as a line or multiple lines. The patterned laser projection is directed at the wafer at a substantially normal angle and applied to the wafer until at least a partial cut is achieved through it. A mechanical separation process completes the separation when only a partial cut is achieved by the patterned laser projection. The die are then transferred to a grip ring for further processing.

What is claimed:  
     
         1 . A method for scribing a semiconductor wafer, said method comprising the steps of: 
 directing a patterned laser projection at a surface of said semiconductor wafer, said semiconductor wafer comprising a substrate layer and a device layer;    applying said patterned laser projection with a given set of parameters until at least a partial cut in said semiconductor wafer is obtained; and    blowing gas across the surface for removing particles during said partial cut.    
     
     
         2 . The method of  claim 1 , wherein said substrate layer comprises a sapphire substrate layer.  
     
     
         3 . The method of  claim 2 , wherein said device layer comprises a nitride device layer.  
     
     
         4 . The method of  claim 2 , further comprising the step of vacuuming said gas received from across the surface with a vacuum hose.  
     
     
         5 . The method of  claim 2 , wherein said blowing is performed by at least one jet nozzle.  
     
     
         6 . The method according to  claim 5 , wherein the blowing step adjusts said jet nozzle to blow gas at a rate greater than 2 psi.  
     
     
         7 . The method of  claim 2 , wherein said patterned laser projection is reflected back into the wafer from a reflector disposed near a second surface of said semiconductor wafer during the applying step.  
     
     
         8 . A method for scribing a semiconductor wafer comprising a substrate layer and a device layer, said method comprising the steps of: 
 directing a patterned laser projection at said device layer of said semiconductor wafer;    applying said patterned laser projection with a given set of parameters until at least a partial cut in said semiconductor wafer is obtained; and    reflecting said patterned laser projection back into said semiconductor wafer during said partial cut.    
     
     
         9 . The method of  claim 8 , wherein said substrate layer comprises a sapphire substrate layer.  
     
     
         10 . The method of  claim 9 , wherein said device layer comprises a nitride device layer.  
     
     
         11 . A method for preparing a semiconductor wafer comprising the steps of: 
 providing said semiconductor wafer, the providing step including the step of, on a substrate, depositing a device layer;    directing a laser through optical elements to form a patterned laser projection;    making a plurality of cuts in at least the substrate via laser ablation using the patterned laser projection; and    blowing gas across a surface of said semiconductor wafer for removing particles during said partial cut.    
     
     
         12 . The method of  claim 11 , wherein said substrate comprises a sapphire substrate layer.  
     
     
         13 . The method of  claim 12 , wherein said device layer comprises a nitride device layer.  
     
     
         14 . The method of  claim 12 , further comprising the step of vacuuming said gas received from across the surface with a vacuum hose.  
     
     
         15 . A laser-based system for dicing semiconductor wafers, comprising: 
 a table for holding and positioning a semiconductor wafer having a plurality of devices, said semiconductor wafer comprising a substrate layer and a device layer;    a projection delivery system for directing a patterned laser projection to a surface of said semiconductor wafer;    a controller for applying said patterned laser projection in accordance with given parameters to achieve at least a partial cut through said semiconductor wafer; and    a cleaning system for removing particles during said partial cut.    
     
     
         16 . The system of  claim 15 , wherein said substrate layer comprises a sapphire substrate layer.  
     
     
         17 . The system of  claim 16 , wherein said device layer comprises a nitride device layer.  
     
     
         18 . The system of  claim 16 , wherein said cleaning system blows gas across the surface of the wafer.  
     
     
         19 . The system of  claim 16 , wherein said cleaning system includes at least one jet nozzle adapted to blow gas across the surface of the wafer.  
     
     
         20 . The system of  claim 16 , wherein said cleaning system includes at least one vacuum hose to remove particles from the surface being cut.  
     
     
         21 . The system according to  claim 16 , wherein said projection system includes a reflector underlying the wafer set on said table for reflecting said patterned laser projection back into the wafer to enhance the cutting process.  
     
     
         22 . The system according to  claim 21 , wherein said reflector is a reflective metal applied to a surface of said wafer.  
     
     
         23 . A laser-based system for dicing semiconductor wafers, comprising: 
 a table for holding and positioning a semiconductor wafer having a plurality of devices, said semiconductor wafer comprising a substrate layer and a device layer;    a projection delivery system for directing a patterned laser projection at said device layer of said semiconductor wafer;    a controller for applying said patterned laser projection in accordance with given parameters to achieve at least a partial cut through said semiconductor wafer; and    a reflector in said substrate layer for reflecting said patterned laser projection back into said semiconductor wafer during said partial cut.    
     
     
         24 . The system of claim of  23 , wherein said substrate layer comprises a sapphire substrate layer.  
     
     
         25 . The system of  claim 24 , wherein said device layer comprises a nitride device layer.  
     
     
         26 . The system according to  claim 24  wherein said reflector is a reflective metal applied to a surface of said substrate.