Semiconductor device separation using a patterned laser projection

Abstract

A method for separating a semiconductor wafer into several thousand devices or dies 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 dies are then transferred to a grip ring for further processing.

1 . A method for preparing a semiconductor wafer comprising the steps of: 
 providing said semiconductor wafer, the providing step including the step of, on a sapphire substrate, depositing a device layer;    directing a laser through optical elements to form a patterned laser projection; and    making a plurality of cuts in at least the sapphire substrate via laser ablation using the patterned laser projection.    
     
     
         2 . The method of  claim 1 , wherein said device layer comprises gallium nitride.  
     
     
         3 . The method of  claim 1 , wherein said device layer comprises gallium arsenide.  
     
     
         4 . The method of  claim 1 , wherein said device layer comprises aluminum nitride.  
     
     
         5 . The method of  claim 1 , wherein said device layer comprises indium nitride.  
     
     
         6 . The method of  claim 1 , wherein said device layer comprises silicon.  
     
     
         7 . The method of  claim 1 , wherein said device layer comprises III-V material.