System and method for automatic analysis of defect material on semiconductors

• US 6,407,386 B1
• Filed: 02/23/1999
• Issued: 06/18/2002
• Est. Priority Date: 02/23/1999
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Dotan, Noam, Kadyshevitch, Alexander
• Primary Examiner(s): Berman, Jack
• Assistant Examiner(s): Fernandez, Kalimah
• Application Number:
  US09/255,495
• Time in Patent Office: 1,211 Days
• Field of Search: 250/310, 250/311, 702/85, 702/86, 702/28, 702/30
• US Class Current: 250/310
• CPC Class Codes: G01N 23/20 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
• CPC Class Codes: H01J 2237/2561 electron

Abstract

A method and system for automatic EDX analysis of defects quantitatively take into consideration x-ray signals attributable to the background. The method and system are capable of automatically identifying suitable locations for background and defect x-ray sampling. The method and system are also capable of effectively and quantitatively, rather than qualitatively, removing signals attributable to the background and not the defect. One advantageous feature that enables the method and system to have a high throughput is termed “trace element analysis.” The method and system are particularly beneficial for analysis of defects on semiconductor wafers and, due to automation, are suitable for in-line inspection of wafers in the fabrication plant.

Claims

1. A method for automatic material analysis of an object within a background, comprising the steps of:

automatically determining a desired location on the object for spectrum acquisition;

acquiring an object spectrum in accordance with said determining;

obtaining a background spectrum;

obtaining count numbers from the object spectrum, corresponding to elements present in the object;

obtaining count numbers from the background spectrum, corresponding to elements present in the background;

analyzing the count numbers of the object spectrum to determine whether a count number appearing in the object spectrum is a non-present element in the object;

analyzing the count numbers of the background spectrum to determine whether a count number appearing in the background spectrum is a non-present element in the background;

standardizing the spectra count of the object according to the count of said non-present element to obtain a net object count; and

analyzing the net object count to determine the material composition of the object.

2. The method according to claim 1, wherein the step of analyzing comprises:

determining all common elements that appear in the count spectra of the background and object;

for each common element calculating a count ratio of object count to the background count for that element;

analyzing the ratios to determine whether any of the common elements is a non-present element.

3. The method of claim 2, wherein the step of analyzing the ratios comprises defining the element having the smallest ratio as the non-present element.

4. The method of claim 2, wherein the step of analyzing the ratios comprises selecting the smallest ratio and, if the smallest ratio exceeds a predetermined threshold, defining the element corresponding to the smallest ratio as a non-present element.

5. The method of claim 1, wherein the step of automatically determining comprises:

obtaining an image of the object;

performing a boundary analysis to obtain an object footprint; and

,

selecting a point on the object footprint from spectra measurement.

6. The method according to claim 1, wherein the step of standardizing comprises the steps of:

normalizing the spectra count of the background according to the count number of the non-present element to obtain a normalized background; and

subtracting the normalized background from the object spectra count of the object to obtain said net object count.

7. The method of claim 1, wherein the step of analyzing the net object count comprises comparing the net object count to an object material library.

8. The method of claim 6, wherein the step of analyzing the net object count comprises comparing the net object count to an object material library.

9. The method of claim 1, wherein the step of obtaining a background spectrum is performed by one of the method:

fetching a background spectrum from a memory;

acquiring a background spectrum from a selected point on the background; and

acquiring a background spectrum from a large background area near the object.

10. The method of claim 8, further comprising the steps of:

for each entry in the object material library determining whether the entry contains the non-present element; and

if the entry contains the non-present element, normalizing the entry to remove the non-present element.

11. The method of claim 10, wherein the step normalizing the entry comprises reducing the level of all count of that entry by an amount corresponding to the count of the non-present element in that entry.

12. The method of claim 1, further comprising the steps of:

comparing each count number of the object spectra count to a list of elements in an object material library; and

if none of the count numbers of the object spectra count appears in the list of elements in the object material library, then defining said object as a foreign object.

13. The method of claim 1, further comprising the steps of:

comparing each element of the object spectra count to a list of elements in a foreign object library; and

,

if one of the elements of the object spectra count appears in the list of elements in the foreign object library, defining said object as a foreign object.

14. A method for automatic material analysis of an object within a background, comprising the steps of:

automatically determining a desired location on the object for spectrum acquisition;

acquiring an object spectrum in accordance with said determining;

obtaining count numbers from the object spectrum, corresponding to elements present in the object;

obtaining count numbers from the background spectrum, corresponding to elements present in the background;

comparing each count number of the object spectrum count to a list of elements in a material library;

comparing each count number of the background spectrum count to a list of elements in a material library; and

if none of the count numbers of the object or background spectrum count appears in the list of elements in the material library, then defining said object as a foreign object.

15. A method for automatic material analysis of an object within a background, comprising the steps of:

automatically determining a desired location on the object for spectrum acquisition;

acquiring an object spectrum in accordance with said determining;

obtaining count numbers from the object spectrum, corresponding to elements present in the object;

obtaining count numbers from the background spectrum, corresponding to elements present in the background;

comparing each count number of the object spectrum count to a list of elements in a foreign object library;

comparing each count number of the background spectrum count to a list of elements in an foreign object library; and

if any of the count numbers of the object or background spectrum count appears in the list of elements in the foreign object library, then defining said count number as a foreign object.

16. A system for material analysis of defects on substrates, said system comprising:

an energized beam for causing said substrate to emit X-rays from one or more automatically selected locations on the substrate;

an X-ray detector collecting X-rays emitted from the substrate;

a processor receiving and analyzing the output of the X-ray detector;

a library containing substrate defect information; and

a library containing materials information.