Method and system for integrated circuit backside navigation

• US 7,135,123 B1
• Filed: 01/14/2004
• Issued: 11/14/2006
• Est. Priority Date: 01/14/2004
• Status: Expired due to Fees

• Current Assignee: DCG Systems Incorporated (Thermo Fisher Scientific Incorporated)
• Original Assignee: Credence Systems Corporation (COHU Incorporated)
• Inventors: Thompson, William B., Thompson, Mark Alan, Kardach, Catherine, Le Roy, Erwan, Lundquist, Theodore
• Primary Examiner(s): Ahmed, Shamim
• Application Number:
  US10/758,146
• Time in Patent Office: 1,035 Days
• Field of Search: 216/59, 216/60, 438/14, 438/16, 438/17, 204/192.33, 204/192.34, 700/121, 250/492.3
• US Class Current: 216/59
• CPC Class Codes: G01R 31/2898 Sample preparation, e.g. removing encapsulation, etching sample preparation in general G01N1/00
• CPC Class Codes: G01R 31/307 of integrated circuits
• CPC Class Codes: H01L 21/3043 Making grooves, e.g. cutting
• CPC Class Codes: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

The backside navigation method of the present invention includes milling a fiducial opening through the substrate of an integrated circuit. The milling process is stopped when the fiducial opening reaches the bottom of a trench isolation structure. The trench isolation structure delineated by the fiducial opening may be imaged and registered to a computer aided design layout image to achieve sub-micron navigation resolution.

Claims

1. A method of backside navigation comprising:

milling a fine fiducial opening through a substrate with a charged particle beam; and

endpointing said fine fiducial opening upon delineating a trench isolation structure to create a registration marker to register an image of said trench isolation structure to a reference image.

2. The method according to claim 1, further comprising:

acquiring said image of said delineated trench isolation structure with said charged particle beam;

receiving said reference image; and

registering said acquired image and said reference image.

3. The method according to claim 2, wherein said reference image comprises a computer aided design layout image.

4. The method according to claim 1, wherein endpointing said fine fiducial opening comprises:

imaging a floor of said fine fiducial opening with said charged particle beam;

detecting a voltage contrast indicating said fine fiducial opening has reached said trench isolation structure; and

stopping said milling of said fine fiducial opening upon detecting said voltage contrast.

5. The method according to claim 1, wherein a width of said fine fiducial opening is substantially sufficient to expose the width of said trench isolation structure.

6. A method of backside navigation comprising:

forming a fiducial opening, wherein a portion of a trench isolation structure is delineated;

acquiring an image of said delineated portion of said trench isolation structure;

registering said acquired image and a reference image; and

generating position control information as a function of said registered acquired image and said reference image.

7. The method according to claim 6, wherein said reference image comprises a computer aided design layout image.

8. The method according to claim 6, wherein forming said fiducial opening comprises:

forming a coarse fiducial opening, wherein a static device region is delineated;

depositing an oxide layer in said coarse fiducial opening; and

forming a fine fiducial opening in said coarse fiducial opening, wherein said portion of said trench isolation structure is delineated.

9. The method according to claim 8, wherein forming said fiducial opening further comprises:

imaging a boundary of said well region to detect a doping deviation in said well region indicative of a presence of said trench isolation structure; and

milling said fine fiducial opening substantially at said detected doping deviation.

10. The method according to claim 8, wherein forming said fiducial opening further comprises:

thinning a substrate prior to forming said fiducial opening; and

imaging said substrate to detect said static device region.

11. The method according to claim 6, further comprising:

making a fiducial marking proximate said fiducial opening; and

maintaining said registration of said acquired image and said reference image as a function of said fiducial marking.

12. The method according to claim 6, wherein registering said acquired image and said reference image comprises:

generating a cross correlation image as a function of said acquired image and said reference image;

oversampling said cross correlation image;

determining an offset of said oversampled cross correlation image; and

aligning said reference image and said acquired image according to said offset.

13. The method according to claim 12, wherein registering said acquired image and said reference image comprises:

preprocessing said acquired image, wherein preprocessing comprises one or more processes consisting of rotation adjustment, magnification adjustment, intensity adjustment and filtering.

14. The method according to claim 12, further comprising:

forming a plurality of fiducial openings, wherein each fiducial opening delineates a separate portion of a trench isolation structure within a field of view;

acquiring an image of each said delineated portion of said trench isolation structure;

registering said image of each delineated portion of said trench isolation structure to a corresponding trench isolation structure in a portion of a trench mask corresponding to said field of view; and

generating position control information as a function of said registered acquired images and said portion of said trench mask.

15. A method of forming a backside marker in an integrated circuit comprising:

forming a coarse fiducial opening;

forming a fine fiducial opening in said coarse fiducial opening, wherein said fine fiducial opening delineates a portion of a trench isolation structure.

16. The method according to claim 15, wherein said coarse fiducial opening delineates a static device region.

17. The method according to claim 16, wherein said static device region comprises a well region.

18. The method according to claim 15, wherein a focused ion beam milling process is utilized to form said fine fiducial opening.

19. The method according to claim 18, wherein forming said fine fiducial opening comprises:

milling at a first focused ion beam current;

milling at a second focused ion beam current as said fine fiducial opening approaches said trench isolation structure, wherein said second focused beam current is less than said first focused ion beam current;

imaging said fine fiducial opening at said second focused ion beam current to detect a first voltage contrast indicative of said fine fiducial opening reaching said trench isolation structure; and

stopping said milling upon detection of said first voltage contrast.

20. The method according to claim 15, wherein forming said coarse fiducial opening comprises:

imaging said integrated circuit to detect a position of a static device region;

milling at said first focused ion beam current;

milling at said second focused ion beam as said coarse fiducial opening approaches said static device region;

imaging said coarse fiducial opening at said second focused ion beam current to detect a second voltage contrast indicative of said coarse fiducial opening reaching said static device region; and

stopping said milling upon detection of said second voltage contrast.

21. The method according to claim 15, further comprising forming an initial opening, wherein said coarse fiducial opening will be formed in said initial opening.