Method and system for high speed measuring of microscopic targets

• US 6,249,347 B1
• Filed: 10/19/1999
• Issued: 06/19/2001
• Est. Priority Date: 03/05/1998
• Status: Expired due to Fees

• Current Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Original Assignee: General Scanning, Inc. (KOCH Industries Incorporated)
• Inventors: Ehrmann, Jonathan S., Svetkoff, Donald J., Kilgus, Donald B. T., Lin, Warren
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US09/420,935
• Time in Patent Office: 609 Days
• Field of Search: 356/375, 356/376, 356/237.4, 356/237.5, 356/394, 356/237.1, 356/73, 250/559.19, 250/559.22, 250/559.23, 250/559.29, 250/559.31, 702/159, 702/162
• US Class Current: 356/625
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object
• CPC Class Codes: G01B 11/2545 with one projection direction and several detection directions, e.g. stereo
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G02B 21/22 Stereoscopic arrangements

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.

Claims

1. 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 in the array of objects;

computing height estimate data for the array of objects utilizing the first set of data;

analyzing the height estimate data to obtain an estimate of the height; and

obtaining additional information about the array of objects using a confocal sensor system based upon the estimate of the height, wherein the confocal sensor system has a spatial filter and a confocal detector to produce sufficient confocal slices of the objects to obtain confocal defect and dimensional information of the objects.

2. The method as claimed in claim 1 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.

3. The method of claim 1 wherein each of the objects has a diameter and wherein the dimensional information is a diameter of at least one of the objects.

4. The method of claim 1 wherein each of the surfaces is a shiny curved surface which is a re-flowed, substantially spherical, solder ball surface.