System and method for automatic orientation of a chip to the CAD layout with sub-optical resolution

• US 9,390,486 B2
• Filed: 09/23/2011
• Issued: 07/12/2016
• Est. Priority Date: 09/29/2010
• Status: Expired due to Fees

• Current Assignee: Neeraj Khurana
• Original Assignee: Neeraj Khurana
• Inventors: Khurana, Neeraj
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): PERLMAN, DAVID S
• Application Number:
  US13/243,804
• Publication Number:
  US 20120076395A1
• Time in Patent Office: 1,754 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01R 31/311 of integrated circuits G01R31/31728 takes precedence
• CPC Class Codes: G06T 2207/20221 Image fusion; Image merging
• CPC Class Codes: G06T 2207/20224 Image subtraction
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction

Abstract

A method and system for aligning a DUT image for testing. The alignment is performed by obtaining an optical image of the DUT from an optical system; obtaining a computer aided design (CAD) data having CAD layers of the DUT; constructing a CAD image of the DUT by overlaying the CAD layers; operating on the CAD image to generate a synthetic image simulating an optical image of the DUT; generating a difference image by comparing the optical image to the synthetic image; and, varying parameters of the synthetic image so as to minimize the difference image.

Claims

1. A computerized method for orienting an image of an integrated circuit device under test (DUT) using a computing system, comprising:

obtaining an optical image of the DUT from an optical system;

obtaining a computer aided design (CAD) data having a plurality of CAD layers of the DUT;

operating on each of the CAD layers to generate a synthetic image simulating an optical image of the CAD layer;

constructing a CAD image of the DUT by overlaying the synthetic images of the CAD layers;

generating a difference image by comparing the optical image to the synthetic image;

varying parameters of each CAD layer of the synthetic image so as to minimize the difference image by, for each of the plurality of CAD layers;

aligning each layer to the optical image in translation, rotation, and image magnification;

adjusting brightness, emissivity and transmittance values of each layer; and

,

indicating edges of transparent layers.

2. The method of claim 1, wherein varying the parameters further comprises varying a global brightness of the synthetic image.

3. The method of claim 2, wherein relative brightness value of each layer is predetermined and wherein the brightness value of each layer is variable on within a redetermined brightness range.

4. The method of claim 1, wherein generating the synthetic image comprises removing hidden geometries for each layer.

5. The method of claim 1, wherein generating the synthetic image comprises applying optical point spread function to each layer so as to simulate the transformation from the CAD design to the fabricated geometries.

6. The method of claim 1, wherein generating the synthetic image comprises removing dummy geometries.

7. The method of claim 1, wherein generating the synthetic image comprises applying blurring to selected layers so as to simulate the image acquisition properties of the optical system.

8. The method of claim 1, further comprising performing a statistical operation on the difference image to statistically quantify the difference image.

9. The method of claim 8, wherein the statistical operation comprises calculating at least one of sum of the squares and Chi-square values of each pixel value of the difference image.

10. The method of claim 9, wherein minimizing the difference image comprises minimizing at least one of the sum of the squares and Chi-square values of each pixel value of the difference image.

11. The method of claim 1, further comprising:

selecting an area of the DUT to be resolved;

for each active device in the selected area calculating a metal line emission reflection;

applying attenuation to each calculated metal line emission reflection.

12. The method of claim 11, wherein applying attenuation comprises one or more of:

applying correction to simulate intensity changes due to angle of incidence of the metal line emission reflection with respect to the optical axis;

applying correction to simulate intensity changes due to changes in refractive indices of materials in which the metal line emission reflection travels; and

,

applying attenuation to simulate intensity changes due to collection efficiency of an optical system.

13. The method of claim 12, further comprising using the CAD data to trace each metal line emission reflection and removing each metal line emission reflection that does not intersect a metal line indicated in at least one layer of the CAD data.

14. The method of claim 12, further comprising tracing each metal line emission reflection and removing each metal line emission reflection that does not pass within a prescribed numerical aperture of the optical system.

15. The method of claim 12, wherein applying attenuation comprises applying a point spread function of the optical system.

16. The method of claim 1, wherein parameters of pixels in central area of the synthetic image are weighted heavier than other pixels.