Method and system for high speed measuring of microscopic targets

Abstract

A system including confocal and triangulation-based scanners or subsystems provides data which is both acquired and processed under the control of a control algorithm to obtain information such as dimensional information about microscopic targets which may be “non-cooperative.” The “non-cooperative” targets are illuminated with a scanning beam of electromagnetic radiation such as laser light incident from a first direction. A confocal detector of the electromagnetic radiation is placed at a first location for receiving reflected radiation which is substantially optically collinear with the incident beam of electromagnetic radiation. The system includes a spatial filter for attenuating background energy. The triangulation-based subsystem also includes a detector of electromagnetic radiation which is placed at a second location which is non-collinear with respect to the incident beam. This detector has a position sensitive axis. Digital data is derived from signals produced by the detectors. In this way, data from at least one triangulation-based channel is acquired in parallel or sequentially with at least one slice of confocal image data having substantially perfect temporal and spatial registration with the triangulation-based sensor data. This allows for fusion or further processing of the data for use with a predetermined measurement algorithm to thereby obtain information about the targets.

What is claimed is:  
     
         1 . A method for developing dimensional information about an object on a specular background utilizing a scanning system having a sensor, the scanning system scanning an illumination beam of electromagnetic energy, the method comprising the steps of: 
 determining reference data based on an illumination beam reflected from the specular, background;    positioning the sensor based on the reference data so that a waist of the illumination beam substantially coincides with an expected predetermined 3D location of the object so as to enhance contrast and obtain three-dimensional sensor data and/or confocal sensor data; and    processing the sensor data to obtain the dimensional information.    
     
     
         2 . The method as claimed in  claim 1  wherein the object is a bump and wherein the dimensional information includes a height estimate of the bump.  
     
     
         3 . The method as claimed in  claim 2  wherein the dimensional information includes information as to whether the bump is defective or not.  
     
     
         4 . The method as claimed in  claim 1  wherein the object has a spherical, mirror-like surface and wherein the object is mounted on a planar mirror-like surface of the background.  
     
     
         5 . The method as claimed in  claim 4  wherein the dimensional information includes a diameter for the spherical mirror-like surface.  
     
     
         6 . The method as claimed in  claim 1  wherein the dimensional information includes 3D information.  
     
     
         7 . The method as claimed in  claim 1  wherein the object is a micromechanical device.  
     
     
         8 . The method as claimed in  claim 1  wherein the object is a conductive trace.  
     
     
         9 . The method as claimed in  claim 1  wherein the object is an interconnect on a semiconductor device.  
     
     
         10 . The method as claimed in  claim 1  wherein the three-dimensional sensor data and the confocal sensor data are processed sequentially or in parallel with a predetermined measurement algorithm.  
     
     
         11 . The method as claimed in  claim 1  wherein the three-dimensional sensor data and the confocal sensor data have substantially perfect temporal and spatial registration before the step of processing.  
     
     
         12 . The method of  claim 1  wherein the object has a diameter and wherein the dimensional information is a measurement of the diameter.  
     
     
         13 . The method of  claim 1  wherein the object is a defect of or on a wafer.  
     
     
         14 . The method as claimed in  claim 1  wherein the dimensional information includes height information.  
     
     
         15 . The method as claimed in  claim 1  wherein the step of processing the sensor data is performed in combination to produce the dimensional information.  
     
     
         16 . The method as claimed in  claim 1  wherein the object has a diameter and wherein the dimensional information includes diameter information and wherein the method further comprises the step of locating a region of the object for further data acquisition based on the dimensional information.  
     
     
         17 . A system for developing dimensional information about an object, the system comprising: 
 at least one illuminator for illuminating an object with at least one beam of electromagnetic energy to obtain at least one reflected beam of electromagnetic energy;    a confocal detector for detecting the at least one reflected beam of electromagnetic energy and producing at least one signal;    a signal processor for processing the at least one signal to obtain confocal data; and    a data processor having digital data processing data smoothing and curve fitting algorithms for processing the confocal data with a priori knowledge about the object to obtain the dimensional information whereby the accuracy of the confocal data is improved.    
     
     
         18 . The system as claimed in  claim 17  further comprising at least one triangulation-based detector for detecting the at least one beam of electromagnetic energy and producing at least one triangulation-based signal and a triangulation-based signal processor for processing the at least one triangulation-based signal and producing triangulation-based sensor data.  
     
     
         19 . The system as claimed in  claim 18  further comprising storage means for storing the triangulationbased sensor data and the confocal data in parallel.  
     
     
         20 . The system as claimed in  claim 18  further comprising a controller coupled to the data processor for controlling the system based on either the confocal image data or the triangulation-based sensor data.  
     
     
         21 . The system as claimed in  claim 17  wherein the dimensional information includes height information.  
     
     
         22 . The system as claimed in  claim 18  wherein the confocal data and the triangulation-based sensor data are processed by the data processor in combination to produce the dimensional information.  
     
     
         23 . The system as claimed in  claim 17  wherein the dimensional information includes gray scale information.  
     
     
         24 . A method for inspecting bumps on a wafer, the method comprising the steps of: 
 acquiring reference data based on 3D information obtained from either a confocal subsystem or a triangulation subsystem having a triangulation sensor;    generating a scan based upon reference data to obtain 3D data wherein the 3D data is obtained from the triangulation sensor; and    determining height of the bumps based on the 3D data.    
     
     
         25 . A method for developing dimensional information about an array of objects, each of the objects having a surface, the method comprising the steps of: 
 obtaining a first set of data representing maximum specular reflections from the surfaces of the objects;    computing height estimate data for the array of objects utilizing the first set of data; and    analyzing the height estimate data to obtain an estimate of the height.    
     
     
         26 . The method as claimed in  claim 25  further comprising the step of obtaining additional dimensional information about the array of objects using a confocal sensor based upon the estimate.  
     
     
         27 . The method as claimed in  claim 25  further comprising the steps of obtaining a second set of data represented by a region in proximity to the maximum specular reflection and analyzing the second set of data by peak location to reduce optical crosstalk.  
     
     
         28 . The method of  claim 25  wherein each of the objects has a diameter and wherein the dimensional information is a diameter of at least one of the objects.  
     
     
         29 . The method of  claim 25  wherein each of the surfaces is a shiny curved surface which is a reflowed, substantially spherical, solder ball surface.  
     
     
         30 . A method of measuring at least one dimension of an interconnect on a specular wafer, the method comprising the steps of: 
 measuring the wafer at three or more non-colinear locations to obtain reference data;    forming a reference surface from the reference data;    scanning the wafer to obtain scan data based on the reference surface; and    determining the at least one dimension of the interconnect based on the scan data.    
     
     
         31 . The method of  claim 30  wherein the scan data is confocal data.  
     
     
         32 . The method of  claim 30  wherein the scan data is triangulation data.  
     
     
         33 . The method of  claim 30  wherein the scan data is confocal and triangulation data.  
     
     
         34 . The method of  claim 30  wherein the interconnect has a curved specular surface.  
     
     
         35 . The method of  claim 30  wherein the interconnect is a solder ball.