Method and system for calibrating a laser processing system and laser marking system utilizing same

Abstract

A method of calibrating a laser marking system includes calibrating a laser marking system in three dimensions. The step of calibrating includes storing data corresponding to a plurality of heights. A position measurement of a workpiece is obtained to be marked. Stored calibration data is associated with the position measurement. A method and system for calibrating a laser processing or marking system is provided. The method includes: calibrating a laser marker over a marking field; obtaining a position measurement of a workpiece to be marked; associating stored calibration data with the position measurement; relatively positioning a marking beam and the workpiece based on at least the associated calibration data; and calibrating a laser marking system in at least three degrees of freedom. The step of calibrating includes storing data corresponding to a plurality of positions and controllably and relatively positioning a marking beam based on the stored data corresponding to the plurality of positions.

1 . A method of calibrating a laser marking system, the method comprising: 
 calibrating a laser marking system in three dimensions, the step of calibrating including storing data corresponding to a plurality of heights;    obtaining a position measurement of a workpiece to be marked; and    associating stored calibration data with the position measurement.    
     
     
         2 . The method of  claim 1  wherein the data is stored in multiple calibration files, the calibration files corresponding to a plurality of pre-determined marking system parameter settings.  
     
     
         3 . The method of  claim 2  wherein the multiple calibration files correspond to a height level and one of marker system parameter settings is a marking field dimension.  
     
     
         4 . The method of  claim 2  wherein one of the marking system parameter settings is a spot size.  
     
     
         5 . The method of  claim 2  wherein one of the marking system parameter settings is a working distance.  
     
     
         6 . The method of  claim 1  wherein the marking system is a backside wafer marking system having a fine alignment camera for obtaining reference data from a topside of the wafer.  
     
     
         7 . A laser-based wafer marking system for marking a wafer having a topside containing a circuit, the circuit having circuit features, the wafer having a backside to be marked, the system comprising: 
 a calibrated galvanometer marking head having a scan lens and a marking field substantially smaller than the wafer;    a calibrated positioning stage for carrying the wafer with a range of motion large enough to position any wafer location to be marked to within the marking field;    a calibrated alignment camera with a field of view substantially smaller than the wafer;    a frame which mounts the stage rigidly with respect to the camera and the marking head; and    a controller having a map for coordinating locations of the marking head, stage, and alignment camera for causing the stage and the marking head to be positioned relative to each other such that the wafer is accurately marked on its backside relative to the circuit features on the front side.    
     
     
         8 . The system of  claim 7  where the alignment camera and the marking field are located on opposite sides of the wafer.  
     
     
         9 . The system of  claim 7  where the alignment camera is offset from the marking head.  
     
     
         10 . The system of  claim 7  where a mark inspection camera is offset from the marking field.  
     
     
         11 . The system of  claim 10  where the controller compares a location of a mark obtained from the inspection camera with a location of a circuit obtained with the alignment camera.  
     
     
         12 . The system of  claim 7  with a second alignment camera is offset from the marking field and a mark inspection camera is offset from the marking field on the backside of the wafer.  
     
     
         13 . The system of  claim 7  wherein the scan lens is a telecentric lens.  
     
     
         14 . The system of  claim 7  wherein the controller coordinates positioning of first and second wafer portions to be marked based on the map, and wherein the portions overlap the marking field.