Defect inspection method and defect inspection apparatus

• US 6,779,159 B2
• Filed: 05/29/2002
• Issued: 08/17/2004
• Est. Priority Date: 06/08/2001
• Status: Active Grant

• Current Assignee: Sumitomo Mitsubishi Silicon Corporation
• Original Assignee: Sumitomo Mitsubishi Silicon Corporation
• Inventors: Nakashima, Yutaka, Yokoyama, Hirokazu
• Primary Examiner(s): Siek, Vuthe
• Assistant Examiner(s): LIN, SUN J
• Application Number:
  US10/156,464
• Publication Number:
  US 20020188917A1
• Time in Patent Office: 811 Days
• Field of Search: 716/4, 716/19, 716/1, 716/20, 716/21
• US Class Current: 382/145
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

A defect inspection method and a defect inspection apparatus accurately determine whether potential defects on a surface of a wafer are true defects, and restrains the oversight or the like of defects, permitting reliable quality assurance and accurate quality control to be achieved. The number and positions of detected potential defects are used as the parameters for determining whether potential defects are true defects. The density of potential defects is determined, and the determined density is compared with a set value to decide whether the potential defects are true defects. A surface of a wafer is captured using a differential interference microscope, and the image is processed to count the number of potential defects observed on the surface. The potential defects are detected at the spots where luminance shifts in the captured image. A spatial filter is applied to the captured image to enhance the area where the luminance shifts, and the enhanced area is binarized. This allows even adjoining potential defects to be detected without overlapping. Based on the characteristic amounts of the detected areas, it is decided whether the potential defects are true defects or noises, then the number of the true defects is counted.

Claims

1. A defect inspection method for detecting potential defects observed on a surface of an object to be inspected, wherein,

a density of the detected potential defects is determined on the basis of the number of and the positions of the detected potential defects and the positions of the detected defects generated adjacently in dotted or in-line configuration, by using gravity center position of the detected defects as a standard, and the density is compared with a set value so as to decide whether the detected potential defects are true defects.

2. The defect inspection method according to claim 1, wherein

if it is determined that the detected potential defects are not true defects, then inspection is carried out in a visual field in the vicinity of an inspected visual field.

3. The defect inspection method according to claim 1, wherein

the inspection results at two positions that align the gravity center positions of the detected potential defects with the central position of the foregoing area, counts the number of the detected potential defects in the area;

determines the density of the detected potential defects on the basis of the ratio of the number of the detected potential defects to the total number of the detected potential defects in the inspection visual field, and decides whether the determined density of the detected potential defects is a set percentage or more so as to determine whether the detected potential defects are true defects.

4. A defect inspection method for detecting potential defects observed on a surface of an object to be inspected, comprising the steps of:

setting an area that is smaller than an inspection visual field if a total number of potential defects in the inspection visual field is smaller than a set value;

aligning the gravity center positions of the detected potential defects with the central position of the foregoing area;

counting the number of the detected potential defects in the area;

determining the density of the detected potential defects on the basis of the ratio of the number of potential defects to the total number of potential defects in the inspection visual field; and

deciding whether the determined density of the detected potential defects is a set percentage or more so as to determine whether the detected potential defects are true defects.

5. A defect inspection method for detecting potential defects observed on a surface of an object to be inspected, comprising the steps of:

determining the gravity center positions of all potential defects if a total number of potential defects in an inspection visual field is smaller than a set value;

determining an n-order approximate curve on the basis of the distribution of the gravity center positions;

counting the number of the detected potential defects existing in a set width along the n-order approximate curve;

determining the density of the detected potential defects the basis of the ratio of the number of potential defects to the total number of the detected potential defects in the inspection visual field; and

determining whether the density of the detected potential defects is a set ratio or more so as to determine whether the detected potential defects are true defects.

6. A defect inspection method for detecting potential defects observed on a surface of an object to be inspected, comprising the steps of:

determining the gravity center positions of all potential defects if a total number of potential defects in an inspection visual field is smaller than a set value;

calculating the distances among the detected potential defects on the basis of the gravity center positions to determine the mean value of the distances; and

determining whether the distance that is smaller than the value obtained by adding or subtracting an offset value preset for the determined mean value is a set ratio or more against the number of combinations of the distances among all potential defects in the inspection visual field so as to determine whether the potential defects are true defects.

7. A defect inspection apparatus for detecting potential defects observed on a surface of an object to be inspected, comprising a defect determining unit,

determining a density of the detected potential defects on the basis of the number of and the positions of the detected potential defects and the positions of the detected defects generated adjacently in dotted or in-line configuration, by using gravity center position of the detected defects as a standard, and

comparing the density with a set value so as to decide whether the detected potential defects are true defects.

8. The defect inspection apparatus according to claim 7, wherein

if the defect determining unit determines that the detected potential defects are not true defects, then performs inspection in a visual field in the vicinity of an inspected visual field.

9. The defect inspection apparatus according to claim 7, wherein the defect determining unit

compares the inspection results at two positions that are symmetrical on the whole surface of an inspected object, and

determines whether the difference there between exceeds a set value so as to determine whether the detected potential defects are true defects.

10. A defect inspection apparatus for detecting potential defects observed on a surface of an object to be inspected, comprising a defect determining unit,

wherein the defect determining unit

sets an area that is smaller than an inspection visual field if a total number of potential defects in the inspection visual field is smaller than a set value,

aligns the gravity center positions of the potential defects with the central position of the area,

detects the number of potential defects in the area;

determines the density of the potential defects on the basis of the ratio of the number of the detected potential defects in the area to the total number of potential defects in the inspection visual field, and

decides whether the determined density of the potential defects is a set percentage or more so as to determine whether the detected potential defects are true defects.

11. A defect inspection apparatus for detecting potential defects observed on a surface of an object to be inspected, comprising a defect determining unit,

wherein the defect determining unit

determines the gravity center positions of all potential defects if a total number of potential defects in an inspection visual field is smaller than a set value,

determines a curve on the basis of the distribution of the gravity center positions,

detects the number of potential defects existing in a set width along the n-order approximate curve,

determines the density of the potential defects on the basis of the ratio of the number of the detected potential defects to the total number of potential defects in the inspection visual field, and

determines whether the density of the potential defects is a set ratio or more so as to determine whether the detected potential defects are true defects.

12. A defect inspection apparatus for detecting potential defects observed on a surface of an object to be inspected, comprising a defect determining unit,

wherein the defect determining unit

determines the gravity center position of all potential defects if a total number of potential defects in an inspection visual field is smaller than a set value,

calculates the distances among the potential defects on the basis of the gravity center positions to determine the mean value of the distances, and

determines whether the distance that is smaller than the value obtained by adding or subtracting an offset value preset for the determined mean value is a set ratio or more against the number of combinations of the distance among all potential defects in the inspection visual field so as to determine whether the potential defects are true defects.

13. A defect inspection method for capturing, by using a differential interference microscope, a surface of an object to be inspected, and processing an image to count the number of potential defects observed on the surface, comprising the steps of:

applying a spatial filter to the captured image to enhance the spot where the luminance shifts;

binarizing the enhanced spots;

detecting potential defects at the binarized and enhanced spots where luminance shifts in the captured image;

determining whether the detected potential defects are true defects or noises based on the characteristic amount of the detected spots; and

counting the number of true defects.

14. A defect inspection apparatus for capturing, by using a differential interference microscope, a surface of an object to be inspected, and processing an image to count the number of potential defects observed on the surface, comprising:

a boundary enhancing unit that applies a spatial filter to the captured image to enhance a boundary area where luminance changes, and binarizes the boundary area to obtain a clear potential defect image;

a defect detecting unit for detecting the potential defects that have been enhanced and clarified by the boundary enhancing unit; and

a defect counting unit that determines whether the detected potential defects are true defects or noises on the basis of the characteristic amount of the area detected by the defect detecting unit, then counts the number of true defects.