Method and system for machine vision-based feature detection and mark verification in a workpiece or wafer marking system

Abstract

A precision laser based method of marking semiconductor wafers, packages, substrates or similar workpieces is provided. The workpieces have articles which may include die, chip scale packages, circuit patterns and the like. The marking occurs in a workpiece marking system and within a designated region relative to an article position. The method includes determining at least one location from which reference data is to be obtained using (a) information from which a location of an article is defined, and (b) a vision model of at least a portion of at least one article. Reference data is obtained to locate a feature on a first side of (a second) workpiece using at least one signal from a first sensor. The method further includes positioning a marking field relative to the workpiece so as to position a laser beam at a marking location on a second side of the workpiece. The positioning is based on the feature location. A predetermined pattern is marked on the second side of the workpiece using a laser marking output beam. The workpiece is a semiconductor wafer, and the step of determining includes: measuring at least one feature in an image obtained from a first wafer portion; relating the measured feature to a wafer map; and storing the data for use when marking of wafers substantially identical to the first wafer.

1 .- 15 . (canceled)  
     
     
         16 . In a laser based system for laser marking of substrates such as semiconductor wafers or similar substrates with a laser marking beam, the substrates having a repetitive pattern of articles arranged in rows and columns, each of the articles having a feature detectable with an imaging subsystem, the system having a laser marking head, the imaging subsystem for imaging and measurement, a motion subsystem having a stage for positioning at least the substrate relative to the imaging subsystem, and a user interface connected at least to the imaging subsystem and motion subsystem, wherein laser marks are to be placed at predetermined locations relative to the articles, a method of laser marking with beam position control using predetermined pattern features, the method comprising: 
 providing, through the user interface, an input so as to cause a portion of the pattern to be identified for automatic feature detection and measurement with a machine vision algorithm;    positioning a first substrate relative to the imaging subsystem automatically to traverse the pattern along at least one of a row or column of the pattern so as to acquire image data at a first set of feature locations;    measuring a dimension using at least one detectable feature of a plurality of articles, the algorithm, and the image data;    storing dimensional data based on the measurement;    determining at least three feature locations of a second set of feature locations relative to the pattern using the dimensional data, the feature locations of the second set suitably defining a relationship between a pattern coordinate system and a stage coordinate system;    removing the first substrate;    positioning a second substrate to be marked relative to the imaging subsystem;    locating the at least three corresponding feature locations of the second set of feature locations in image data obtained from the corresponding pattern on the second substrate;    relating coordinates of the pattern on the first substrate to the corresponding pattern on the second substrate; and    positioning the substrate relative to the marking beam based on at least the three feature locations of the second set to mark the substrate.    
     
     
         17 . The method of  claim 16  wherein a first estimate of the dimension is obtained by semiautomatic relative positioning of the substrate and the imaging subsystem over a substantially small area of the pattern and further comprising: 
 identifying a feature in a displayed image; and    communicating the image location of the feature using the user interface.    
     
     
         18 . The method of  claim 17  wherein the substrate is a semiconductor wafer, the articles are die, and a feature is a corner of the die.  
     
     
         19 . The method of  claim 18  wherein the dimensional measurement is the average die pitch measured over a substantial number of die along at least one of a row and column.  
     
     
         20 . The method of  claim 19  wherein the average die pitch is related with a wafer map.  
     
     
         21 . The method of  claim 16  wherein the pattern coordinate system has an origin defined relative to a boundary of the pattern.  
     
     
         22 . The method of  claim 16  wherein the step of determining includes searching for pattern locations, and wherein searching is carried out controlling the stage based on pattern system coordinates.  
     
     
         23 . The method of  claim 16  wherein the step of providing further includes generating a vision model using an image of a portion of the pattern.  
     
     
         24 . A system for carrying out the method of  claim 16.